737 'Tailstrike' Caused By Typo On a Tablet (arstechnica.com)

An anonymous reader writes: In August of last year, a Boeing 737 operated by Qantas experienced a tailstrike while taking off — the thrust wasn't great enough for the tail to clear the runway, so it clipped the ground. The investigation into the incident (PDF) has finally been completed, and it found the cause of the accident: the co-pilot accidentally entered the wrong plane weight data into the iPad used to make calculations about the takeoff thrust. "First, when working out the plane's takeoff weight on a notepad, the captain forgot to carry the "1," resulting in an erroneous weight of 66,400kg rather than 76,400kg. Second, the co-pilot made a "transposition error" when carrying out the same calculation on the Qantas on-board performance tool (OPT)—an iPad app for calculating takeoff speed, amongst other things. "Transposition error" is an investigatory euphemism for "he accidentally hit 6 on the keyboard rather than 7." This caused the problem: "For a weight of 76,400kg and temperature of 35C, the engine thrust should've been set at 93.1 percent with a takeoff speed of 157 knots; instead, due to the errors, the thrust was set to 88.4 percent and takeoff speed was 146 knots."

Comments

It's even worse than that now.

[idontgno]

In the future, any flight engineer or pilot using that iPad to enter the plane weight data runs the risk of having it auto-corrected to the wrong value used by the crew in this case.

No, not really. I hope.

Re:It's even worse than that now.

[Austerity Empowers]

That'll make for some angry birds.

Re:It's even worse than that now.

[davester666]

no, the pigs are all in the plane.

Re:It's even worse than that now.

[sycodon]

Umm...Tail Strikes on take off are caused by over rotation.

Regardless, seems to me that pilots calculating the take off weight is anachronistic. Manufacturers can easily incorporate weight sensing devices into the gear. Or, weight sensors could be incorporated into a Wheel Chock device. There is no reason for guesstimates.

Re:It's even worse than that now.

[tripleevenfall]

"76,860 kg" autocorrected to "Settings thousand ate sexy cardiograms"

Re:It's even worse than that now.

[tripleevenfall]

The birds might be angry about the word "transposition" being used incorrectly in the summary. They hate that.

Re: It's even worse than that now.

[Anonymous Coward]

Sure, over rotation due to running out of runway due to insufficient power applied!!

Re:It's even worse than that now.

[bluescrn]

Let's just hope they're not entering anything case-sensitive with the iOS8 on-screen keyboard...

Re:It's even worse than that now.

[michelcolman]

First of all, tail strikes on take-off are obviously the result of overrotation, but this usually happens because the pilot rotates at the wrong speed. You pull back, expecting the plane to leave the ground, but instead the plane remains on the ground while the nose keeps going up. Also, you may be running out of runway if the calculations were off, so you'll pull back regardless.

About the weight sensors: good idea, but this is aviation, where everything has to work reliably in pretty difficult environmental circumstances. Even something as simple as a proximity switch to determine whether or not the gear is down, fails from time to time. We often deal with incorrect tire pressure indications, temperature indications, etcetera. Measuring the weight of a plane with sufficient precision is quite a bit more complex than a simple tire pressure reading, so I can't see any manufacturer trusting that kind of system enough to let it determine take-off settings by itself. Maybe as an extra crosscheck for the data from the loadsheet, sure, but not as the primary source of information.

People always go "we should replace the pilots with automated systems because pilots make too many mistakes", but they have no idea how many mechanical failures we deal with as part of the routine of our job. We make mistakes, sure. But so does automation.

Re: It's even worse than that now.

[manu144x]

As a software developer I love it when people forget that computers run software written by humans who are error prone too :)

Re:It's even worse than that now.

[Anonymous Coward]

How difficult can it be to put some scales in the taxiway to actually weigh the planes? There are just three points to measure.

Re:It's even worse than that now.

[skovnymfe]

Or worse, it'll autocorrect from kg to lbs because 'Merica!

Re:It's even worse than that now.

[michelcolman]

Neural networks in an airplane? Looking at the glacial pace of technological improvements in airplanes, that's quite a few decades away.

All airplane software has to conform to rigorous specifications and costs millions of dollars/euros to validate. We often wonder why airplane autopilots sometimes perform certain maneuvers less efficiently or smoothly than we would have, and usually it's because the specs say it has to do it exactly that way because otherwise in certain situations it might exceed certain limits. No room for something resembling common sense, it has to be proven safe.

So now imagine a neural network, where you just give it input and let it "learn" while nobody really knows what's going on inside, the best we can do is say it's sort of like how a brain works. Would they let something fuzzy like that control anything important inside the airplane? Probably not in my lifetime.

Re:It's even worse than that now.

[stoatwblr]

Ok, so a big-ass weighstation platform. Let's ignore the logistics of something that size that for a moment

Weighing accurately from under 1 ton to over 700?

Compensating for rain? Compensating for wind? (This will make apparent weight change. A parked 747 in even a mild breeze moved and heaves like a beast wanting to leap into the air)

Calculating the centre of mass too? (This is at least as important as overall TOW)

Re:It's even worse than that now.

[michelcolman]

Reduced thrust take-offs have been normal procedure for decades now. They save a lot of fuel, make less noise and produce less wear on the engines so you can use them a lot longer with less maintenance. They also make engine failures less likely to occur: the last few engine failures in my company have been full thrust take-offs (which we rarely do anymore, only when required on short runways, heavy weight, high temperature,...).

It's even got to the point where we often take off with less than climb thrust, which is normally forbidden. Airbus got around that restriction by inventing two different climb settings, low level and high level climb. So you get the weird situation where, instead of the normal thrust reduction after take-off, you actually get an increase in thrust after flap retraction.

Re:It's even worse than that now.

[michelcolman]

What kind of sensors do you propose that can measure weight with a 0.1% tolerance and withstand the harsh environment of an airplane? Temperatures between +50 and -70C, shocks on landing, water and ice,...

Fuel gauges are often off 2% or more, pressure sensors usually have two or maximum three significant digits, I don't think there's any sensor in any airplane that has a 0.1% tolerance.

Now, to catch gross errors, 1% would be more than enough. But I doubt even that is achievable with anything near to the required reliablity for aviation.

Re:It's even worse than that now.

[strikethree]

Ummm. I know this is a VERY expensive idea, but you know that turn that planes make just before entering onto the runway? Yeah, that one. Why not have that section be a scale? There could even be some sort of giant electronic billboard that could show the weight... in kilograms if you are uncivilized. ;)

Re:It's even worse than that now.

[michelcolman]

First of all, you would need one of those scales at every runway, and at multiple intersections where planes line up for take-off. Then, pilots would have to do their calculations there and then, while the engines are running, wasting time and fuel. And of course every now and then one of the scales will inevitably break or become unreliable. Etcetera... Nope, ain't gonna happen.

I think I remember an airport once outfitted some of the parking positions with a scale, and they abandoned the project because it was too unreliable and broke all the time.

Re:It's even worse than that now.

[RockDoctor]

There are just three points to measure.

So, that's three sensors, each of which has to be accurate to around 1 part per thousand, over a range of loads from around a ton to around a thousand tonnes. And all 3 have to remain within calibration error of each other. Without taking into consideration the loads imposed on the plane by weather.

Have you ever actually built and operated instrumentation?

Data data everywhere and not a drop to think

[burtosis]

It still boggles my mind how we live in the Information Age and this data was not automatically uploaded and calculated. I'm not saying it dosent require a human to sign off on, but it's mildly insane it isn't all automatically calculated and simply checked.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

I don't know for sure, but I believe the pilots are supposed to *only* use the certified avionics systems in the aircraft, but they hate the godawful UIs in those things so they use iPads even though they're really, really, really not supposed to.

Re:Data data everywhere and not a drop to think

[kybred]

Yes, why isn't this something the flight system calculates, instead of "There's an App for That"?

Re:Data data everywhere and not a drop to think

[kuzb]

Probably because boeing would charge another $750,000 for that feature.

Re:Data data everywhere and not a drop to think

[iONiUM]

Uh, isn't the weight the plane + fuel + baggage + passengers? 3 of those are clearly easily gathered (fuel, plane, baggage) automatically. Only the 'passengers' part isn't, but I'm assuming they just use averages (they don't weight us when we get on) via # of people * average weight.

So yea, why the fuck isn't this automatically calculated and prepared? What part of this requires a human who is bad at math and able to make mistakes on simple data input?

Re:Data data everywhere and not a drop to think

[kelemvor4]

It still boggles my mind how we live in the Information Age and this data was not automatically uploaded and calculated. I'm not saying it dosent require a human to sign off on, but it's mildly insane it isn't all automatically calculated and simply checked.

Is there some reason they shouldn't just use 100% thrust at takeoff and make sure the cargo being carried was less than the maximum capacity?

Re:Data data everywhere and not a drop to think

[es330td]

Is there some reason they shouldn't just use 100% thrust at takeoff and make sure the cargo being carried was less than the maximum capacity?

These engines are optimized for certain turbine speeds. By staying within the recommended ranges they reduce wear & tear and improve efficiency. In addition, max acceleration is harder on the passengers. Think of it like driving a car. Do you accelerate from every stop by pressing the gas pedal all the way to the floor or do you match how much gas you give it to the driving conditions and who and how many people are in your car?

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

It still boggles my mind how Slashdot users still can't be bothered to read the linked article(s) and any comments associated with the original article.

In this case, the piece on Ars has comments from not one but *two* 737/A320 pilots outlining what happened and the reasons for it.

Re:Data data everywhere and not a drop to think

[NMBob]

That's what I thought. The answer is "yes", but not in the Information Age. In this age we need to make everything as complicated as possible, so that we can pile on more stuff to make things less complicated.

Re:Data data everywhere and not a drop to think

[thegarbz]

HOW would it be "all automatically calculated and simply checked"?

Sensors. Or do you think the co-pilot parked the plane on kitchen scales on the way out?
We live in a heavily instrumented world.

Personally, it boggles my mind how people who live in this Information Age don't understand how information is gathered and processed.

The irony of that statement is delicious.

Re:Data data everywhere and not a drop to think

[Impy the Impiuos Imp]

Well apparently both made the exact same error, for completely different reasons. So redundandy didn't help.

Really, though, why don't modern large planes all weigh themselves?

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

Cost of fuel + wear on engines.

Re:Data data everywhere and not a drop to think

[jedidiah]

This seems like something the plane should be able to do all by itself. This is $50M aircraft. It should be at least as sophisticated as a hospital bed.

Re: Data data everywhere and not a drop to think

[WarJolt]

My guess is that the 737 was built about 20 years ago. The ipad is taking place of what is essentially a circular slide ruler.

Airliners have had scales built into them for years, but you still need to calculate load based on fuel, passengers and cargo.

What's concerning is they didn't notice the velocity not rising fast enough to increase throttle. Additionally they didn't have enough intuition to recognize their calculations were way off.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

HOW would it be "all automatically calculated and simply checked"?

Sensors. Or do you think the co-pilot parked the plane on kitchen scales on the way out?
We live in a heavily instrumented world.

WHAT "sensors"? Ones accurate enough to be used to compute weight and balance for something that's going to weigh several hundred thousands of pounds as it flies through the air at several hundred miles an hour? Ones reliable enough to withstand airport baggage handlers?

Personally, it boggles my mind how people who live in this Information Age don't understand how information is gathered and processed.

The irony of that statement is delicious.

What color is the sky on your planet? It ain't blue, that's for sure.

Because you obviously haven't stopped to think about how hard it is to wire up everything needed to conduct weight and balance of an aircraft.

Re:Data data everywhere and not a drop to think

[Ichijo]

And for another layer of redundancy, the plane or the iPad should detect that it isn't accelerating at the expected rate.

Re:Data data everywhere and not a drop to think

[gstoddart]

Is there some reason you don't redline your car before you pull away from a stop light?

Having pilots who don't know how to do anything other that "rev it up to full speed and let 'er rip" sounds like a terrible idea to me.

Both for maximizing fuel and not abusing the engines, doing it based on real numbers makes more sense than the equivalent of flooring it.

Re: Data data everywhere and not a drop to think

[zaimor]

By taxiing the aircraft over a scale device at some point during the departing process. Similar to highway weigh stations. I've always wondered why they didn't do this.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

And $745,000 of that is needed to comply with and get the app through DO-178C certification. The rest is pure profit.

Re:Data data everywhere and not a drop to think

[SuricouRaven]

You shouldn't even need to calculate it - the plane can measure weight itsself. There are only three points of contact with the ground, easy to mount a strain gauge in the landing gear. It might not be precise enough, but it'll be fine for sanity checking - if the measured and calculate weights differ by more than the margin of error, plane refuses to bring the engines above taxi thrust.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

>WHAT "sensors"? Ones accurate enough to be used to compute weight and balance for something that's going to weigh several hundred thousands of pounds as it flies through the air at several hundred miles an hour? Ones reliable enough to withstand airport baggage handlers?

Place a sensor in each wheel strut. Add the total. Done. Seriously, it doesn't seem all that hard to me. Sure, it's probably expensive to make sensors that can read that many tons. Then again, so was the airplane.

The weight will only change in a "random" way while on the ground. Thus you can measure the plane while on the ground.

During flight, the computer knows how much fuel is being consumed. Subtract the estimated weight of the fuel, and you can now even have in-flight updated weight totals.

Re:Data data everywhere and not a drop to think

[Tawnos]

I can think of a few ways this could be done - integrated into the pressure monitoring of the wheels and shocks, using a rolling weigh system like semi trucks do, or similarly-constructed systems. It's hard, but not impossible.

Re:Data data everywhere and not a drop to think

[Goldenhawk]

I'm a flight test engineer that works on large (passenger-class) aircraft. We do tests related to this issue.

It actually has a lot to do with takeoff safety, ironically enough. If you lose an engine at high power, the airplane will try to yaw (turn left or right) because the engine(s) on the other side are still producing thrust. At lower speeds, with less aerodynamic forces, the rudder is not capable of keeping the airplane in a straight line. So there's a speed called "Vmcg" - "velocity minimum control ground" - below which you MUST pull back the power on the good engines to avoid going off the side of the runway (you're going to have to stop the takeoff). There's also a speed called Vmca, the airborne minimum control speed (you will start to yaw out of control).

So with less power on all the engines, there is less asymmetry possible in the event of a failure. With reduced takeoff thrust, you don't need as much rudder at any given airspeed, so your Vmcg and Vmca are both lower.

This is important for takeoff because if you have a lot of runway available, you can use it by taking longer to accelerate (by having lower thrust). As a consequence, your risk in the event of an engine failure is reduced - you won't head off into the grass if it happens on the ground, and you'll be assured of sufficient control authority if it happens in the air.

So when an airplane manufacturer builds the "takeoff performance charts", these Vmc speeds heavily factor into the takeoff planning.

Now, in this tail strike mishap, the lower weight caused the iPad to compute TOO LOW a speed. Lifting off too slow takes more nose-up (pitch) angle; lift goes up as a linear function of pitch angle; lift has to equal weight to go flying. Because of the reduced takeoff thrust, they were already planning to use most of the runway to accelerate - which put them into a corner; they were too slow to take off at the normal pitch angle, but were out of room to stop. So they pulled up until the airplane started flying - which means they pulled up high enough that the tail hit the ground (just barely in this case).

Re:Data data everywhere and not a drop to think

[jbwolfe]

As long as the device and software (the iPad and app in this case) has been vetted by the regulating agency, it is acceptable to use and may actually be required. I'm unsure of the interface to which you are referring, but takeoff performance calculations are not integrated into any large transport aircraft that I have ever flown. The FMC can only calculate data accurately if its given the correct inputs- stuff like ZFW, CG, flap setting, reduced thrust setting, etc. GIGO

At my airline, takeoff data calculations are centralized (acquired through datalink) rather than carried onboard, but still require those variables.

Re:Data data everywhere and not a drop to think

[ShanghaiBill]

Ok, Einstein. Provide model numbers of the sensors capable of doing what you claim "are clearly easily gathered".

The landing gear use hydraulic and pneumatic systems, and there are already sensors that measure that pressure. The weight of the plane is a simple linear function of the pressure of the fluids in the landing gear.

Re:Data data everywhere and not a drop to think

[drinkypoo]

Is there some reason you don't redline your car before you pull away from a stop light?

My car has traction control, and will behave perfectly nicely if I do that, you insensitive clod! Well, one of them anyway. The most modern one.

Re:Data data everywhere and not a drop to think

[Obfuscant]

I wish I had mod points today. Excellent answer.

Add in the safety factor that a heavy aircraft is better lifting off further down the runway so that the following departures and arrivals of lighter aircraft are less likely to encounter wake turbulence. As a small plane jockey, you always want to take off or land before the point the previous heavy aircraft took off, or after the point the previous heavy aircraft landed.

Re:Data data everywhere and not a drop to think

[jbwolfe]

Once airborne, the FMC can do performance calculations. But not unless it has been given the variables that only the pilot or load planner can know. Among the variables inputted by the pilot are ZFW, CG, cost index, flap setting, thrust reduction, and takeoff profile.

ZFW and CG relate to how many people and bags and where they are located. Cost index and thrust reduction are mostly economic decisions. Flap setting is dictated by runway choice.

Re: Data data everywhere and not a drop to think

[Overzeetop]

Or, you know, a simple translational sensor on the landing gear before rollback. AKA the weight of each support point.

Re:Data data everywhere and not a drop to think

[Jason Levine]

Weighing a person and weighing a fully loaded plane are two very different things. If you need the level of technology required to weight a plane when you're weighing a person, I doubt that person's going to fit into a standard hospital bed.

Re:Data data everywhere and not a drop to think

[Jason Levine]

Do you accelerate from every stop by pressing the gas pedal all the way to the floor or do you match how much gas you give it to the driving conditions and who and how many people are in your car?

Sadly, for too many drivers, the answer would be "I floor the gas, going from 0 to 60 in as short a time as possible. Then, I hit the brakes and come screeching to a halt at the red light four blocks ahead of me."

Re: Data data everywhere and not a drop to think

[bill_mcgonigle]

hey, now, this is just an airliner, not a fancy tractor trailer.

Re:Data data everywhere and not a drop to think

[edtice1559]

This all makes sense and I too wish I had mod points as I would use them instead of responding. What I don't understand here is how the error wasn't noticed while going down the runway. I'm going to explain this using all of the wrong terminology but hopefully my point comes across. As the plane travels down the runway, the generated lift causes the nose to start to rise at a certain angle. As you get closer and closer to leaving the ground, the pitch rises. My understanding is that the Concorde relied on starting to take off with no flaps or elevator to build up maximum speed and then at the last second the pilots pulled up as hard as they could. But subsonic passenger planes set the flaps prior to engaging thrust and so a takeoff has a certain "feel." How is it that the pilots didn't notice that they weren't getting enough lift. As a passenger, I think that I would notice it and I have no flying experience. (For reasons I can't fathom, they don't give commercial pilots licenses to us blind people)

Re:Data data everywhere and not a drop to think

[kipsate]

air speed*

Re:Data data everywhere and not a drop to think

[sunking2]

The real question is why is he doing the math by hand. Computers are pretty good at that.

Re:Data data everywhere and not a drop to think

[jbwolfe]

To add to this and in regard to the model flown here, The -800 and-900 versions are stretched and have higher MTOG. The end result is since the landing gear are just as short, there is even less margin for error with tail strikes. This is true both for takeoff and landing and results in higher rotation speeds as well as higher approach speeds. In some cases, this results in weight restrictions due solely to the needed increased speeds.

Also of note regarding Vmcg, if Vr (reject) is lower than Vmcg, you're overweight for takeoff. Virtually never a factor for a modern aircraft.

Re:Data data everywhere and not a drop to think

[MouseR]

The iPad is not at fault here. Pilot did simple math and forgot to carry over a "1". There's no carry over when you let a software add.

It's a whole system failure: paper being handed out to be hand-computer and then the number punched into a iPad for final trust numbers which are then entered in the avionics system.

A frickin piezo on the landing gears would have done the trick.

Re:Data data everywhere and not a drop to think

[HangingChad]

this data was not automatically uploaded and calculated.

I know, right? All the sophisticated sensors on an airliner and there isn't one to say your exact weight? The DMV can weigh trucks without stopping at scales now, how is it airlines are still using average passenger and bag weights? This is insane.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

Do you accelerate from every stop by pressing the gas pedal all the way to the floor

No, but my car doesn't tend to crash when I accelerate too little; planes do.

Re:Data data everywhere and not a drop to think

[avandesande]

yes you think there would be a speed you would expect to be at half way(or some other decision point) down the runway where you would abort the takeoff if it was too low.

Re:Data data everywhere and not a drop to think

[turning in circles]

I imagine noise restriction regulations cause pilots to be required not to use more thrust than necessary on takeoff.

Re:Data data everywhere and not a drop to think

[rholtzjr]

Hmm, something similar to a weigh station for semi trucks in order prior to take off?

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

Uh, isn't the weight the plane + fuel + baggage + passengers? 3 of those are clearly easily gathered (fuel, plane, baggage) automatically. Only the 'passengers' part isn't, but I'm assuming they just use averages (they don't weight us when we get on) via # of people * average weight.

Both NTSB and FAA recommends using the actual weight of passengers and baggage if the plane has less than 30 seats. The reason being a crash in Alabama (I think it was Alabama), which was due to overweight as all passengers were heavier than the average and had heavier baggage than average. This made the tail too heavy and the plane was unable to bring the nose down once it left the ground, stalled and crashed into the airport itself. However since it's a recommendation and not a rule, airlines are free to ignore this and some do. All "big planes" use average weight for people and passengers.

In the early days of flying, passengers had to be moved around the plane according to weight, which meant they had to weigh everybody. The reason is that the early planes was known to crash if their center of gravity was moved too much. As a result the "heavy passengers" were moved to the seats near the center of gravity. Modern planes are bigger, hence less affected and they have a computer, which automatically compensates. This mean if the pilot wants to go strait, the computer will turn to get a strait line of travel as a result. The same goes for tilting, meaning it will actively keep the wings level. Before computers, the pilot would have to compensate manually, hence the bigger importance of a well placed center of gravity.

Could we weigh all passengers? Sure one paper from FAA and it would be mandatory. However I saw one airline introducing mandatory weighing of passengers and a journalist went banannas regarding harassment of overweight people. The journalist completely skipped that it was according to the FAA recommendation or safety. This tells me the biggest challange regarding knowing the actual weight of passengers is politicial or mob opinions rather than technical or practical. Personally I fully support using actual measurements to increase safety, but the social media mob will not care for what engineers think or say.

Re:Data data everywhere and not a drop to think

[Andy Dodd]

I've never seen a flight where they were threatening bumping that they weren't gate-checking bags because every seat was full and there wasn't enough room for carryons.

(Not weight reduction here - bag was still on the plane, just in cargo instead of overhead bins in the passenger compartment.)

Re:Data data everywhere and not a drop to think

[Andy Dodd]

The real story behind $10,000 hammers you hear people joke about in defense & aerospace:

It's a $500 hammer because it's made from premium materials and is designed to handle things most hammers in civilian use would never see, plus $9,500 worth of government-mandated paperwork proving you didn't rip off the government.

Re:Data data everywhere and not a drop to think

[invictusvoyd]

That was my first reaction to this . But there must be a reason for not putting a sensor on the landing gear . I just cant imagine that they missed that out !

Re:Data data everywhere and not a drop to think

[edtice1559]

It seems (and again I'm speaking about something where I have very little knowledge) that they did realize at some point which is why they pulled up hard on the stick and struck the tail. I don't know the procedure in this case. Should they have also opened up the throttle? Should they have known sooner? I hate to be an armchair quarterback but the OP was good enough to raise these types of questions and I'm curious to know the answers.

Re:Data data everywhere and not a drop to think

[umghhh]

So what we need to tell all aircraft manufacturers - install this strain gauge of yours (if the view that there are only 3 points there is accurate enough is another story). This will surely include heavy cost as with anything aircraft related and produce its own faults. I am not saying it should not be done. What I wanted to covey is that it is not certain that the effort is worth it. I am pretty sure mistakes are made all the time more than it is comfortable to think about. Yet nothing really happens. In one case both pilots made a mistake making it to almost crash yet there was still no significant damage or? Thus the question is justifiable - is the technological measure so much better to make it into production? As with many other things that we experience in real life - there are solutions and we still do not use them because the cost does not justify the benefits. Especially if cost is not only deploying new solution but also costs of new faults that it brings with it.

Re:Data data everywhere and not a drop to think

[leathered]

I'm only a private pilot but you also need to take into account temperature, air pressure (QNH), headwind component, the amount of runway you have to work with as well as weight to calculate takeoff performance.

Re:Data data everywhere and not a drop to think

[edtice1559]

Just read your post again. I think the challenge is that the "too slow" speed is a function of how heavy you are. A lightly loaded plane can take off at a slower speed. Since they both thought the plane was 10k kg lighter than it was, the speed may not have been an indicator. But the fact that they didn't seem to be generating *lift* *could* have been an indicator but again I'm now very curious but don't have any hard knowledge.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

The amount of thrust needed to bring it up to speed is exactly what this calculation was for.

Re:Data data everywhere and not a drop to think

[tompaulco]

are you a pilot? Is it true that airlines now have to bump people to later flights not because the seats are oversold but because people are so fat that the airline maxes out on weight before everybody gets on board. fat people. what's up with that?

On a regional jet like the ERJ-140, if everybody was 250 pounds and brought a 25 pound bag, they would exceed the maximum payload weight. On larger aircraft like the 737-800, you could be well under maximum payload weight, at least before fuel is added, but then range is limited. The FAA uses 190 pounds in the summer and 195 in the winter for the weight calculations of passenger plus carryon. The average adult weight in the U.S. is 176.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

I routinely get asked for my weight when travelling on small commercial aircraft. My mother once described standing in line behind two other ladies who were asked their weight, and hearing their answer, estimated how much they lied by and added it to her own weight, just to be certain her flight was safe.

Re:Data data everywhere and not a drop to think

[jbwolfe]

I are a pilot. Nowadays, butts are just given an assumed weight. Not sure how much exactly, I think 250lbs per person and that includes luggage. A long history of weighing passengers and bags resulted in statistical averages plus a safety factor. If you got bumped with seats available, it was likely because performance, perhaps takeoff, but often landing limits resulted in weight restrictions.

Re:Data data everywhere and not a drop to think

[avandesande]

You would expect a certain speed with a certain thrust- even if the optimum takeoff speed changes. This would tell you if your calculations are off.

Re:Data data everywhere and not a drop to think

[Coren22]

Heck, just build a huge scale into a section of the airport apron for this purpose. It could even have a built in bluetooth or other wireless connection with the plane.

Re:Data data everywhere and not a drop to think

[nitehawk214]

The settings for takeoff should be known before you try it. You would want to know if the airplane was capable of taking off before you start to roll down the runway.

Re:Data data everywhere and not a drop to think

[CohibaVancouver]

Interestingly enough, most commercial planes can't measure how much fuel they're carrying

Of course they can. Here are some examples of the gauges on a 737 -

http://www.b737.org.uk/fuel.ht...

The Gimli Glider ran out of fuel because the gauges weren't working and they messed up the manual calculations.

Re:Data data everywhere and not a drop to think

[nitehawk214]

Kid, shouldn't you be in school or playing counterstrike right now?

Re:Data data everywhere and not a drop to think

[Coren22]

http://www.scalesgalore.com/Di...

http://www.cardinalscale.com/p... (look at the bottom one, likely big enough for a plane)

Re:Data data everywhere and not a drop to think

[laurencetux]

the big problem is building and certifying a weight sensor that

1 will not need to be calibrated (unless you are taking the wheel/struts OFF)
2 will have a small enough error range to be useful
3 can get a decent number (hint i don't think its a simple add plus how do you handle skew (not going straight DOWN) in the numbers )
4 oh and btw you have to comp for temps from ALASKA to HAWAII

Re:Data data everywhere and not a drop to think

[Coren22]

Didn't think of searching for it until after I posted, but they even make them for aviation!

http://www.intercompcompany.co...

Re:Data data everywhere and not a drop to think

[Coren22]

http://www.intercompcompany.co...

They make airplane sized scales...perhaps just build them into the taxiway and have a wireless communications to the plane of the weight.

Re:Data data everywhere and not a drop to think

[michelcolman]

Actually, every aircraft has fuel gauges, and they are normally pretty accurate. However, since any aircraft equipment can and does fail from time to time, including those fuel gauges, we do crosscheck with the amount of fuel delivered by the truck to make sure the gauge reading is correct. In some older planes, the figure calculated from the uplift is even considered to be more accurate than the gauges. But there's no such thing as a commercial plane that can't measure how much fuel it's carrying.

Re:Data data everywhere and not a drop to think

[Drethon]

One flight I was on was delayed for two hours due to the APU not working, then the air start cart they called to start the engines having a dead battery, then the next cart being too small and they jumped the first cart from the second (or something like that, I was 14) and finally were able to start the engines. After all that was done, the airplane was accelerating to what felt like full throttle even before pointing straight down the center line and made the most rapid ascent of any airliner I've ever been on.

So occasionally airliners to "floor it".

Re:Data data everywhere and not a drop to think

[Drethon]

I think that is somewhat dependent on the terrain around the airport and a bigger issue after the airplane leaves the ground.

Re: Data data everywhere and not a drop to think

[michelcolman]

Recent planes do that (even something as old as an A320), but you have to actually be flying for that to work. So it's pretty useless before take-off.

Re: Data data everywhere and not a drop to think

[michelcolman]

The day they can get tire pressure sensors, temperature sensors, fuel gauges etcetera to work reliably without failing or giving incorrect indications every now and then, maybe they can try measuring weight. Technology moves slowly in aviation.

Re:Data data everywhere and not a drop to think

[michelcolman]

Because you need more speed if the weight is higher. And you may also need more thrust if the runway isn't long enough.

Re:Data data everywhere and not a drop to think

[grahamtriggs]

How on earth did anyone cope in the 70s, before iPads were invented?

Re:Data data everywhere and not a drop to think

[evilviper]

It still boggles my mind how we live in the Information Age and this data was not automatically uploaded and calculated.

If you should have learned anything about "the information Age", it's that life-critical systems should NOT be highly interconnected. If it's just a single 5-digit number that needs to go from point-A to point-B, plain-paper sneakernet is quite convenient and by far the safest and most reliable option.

Re:Data data everywhere and not a drop to think

[swillden]

The settings for takeoff should be known before you try it. You would want to know if the airplane was capable of taking off before you start to roll down the runway.

Sure, but it still seems like measuring thrust vs acceleration as you start accelerating down the runway is a really easy way to double-check weight and if it's too far out of plan, automatically abort the takeoff. It seems like this should be possible long before the plane is moving too fast to cut thrust and brake safely to a stop.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

I routinely get asked for my weight when travelling on small commercial aircraft. My mother once described standing in line behind two other ladies who were asked their weight, and hearing their answer, estimated how much they lied by and added it to her own weight, just to be certain her flight was safe.

The FAA recommendation states that scales should be used, not just asking the passengers. Some airports installed them and it's very simple. The passenger always stand at a certain location when exchanging papers at checkin. The scale is located there and it is of a size and shape that doesn't look like a bathroom scale. It looks more like a device for "stay behind this line for privacy of the person in front of you" like you see at the doctor or similar places with personal info being exchanged. Most people might not even notice the airline measured their weight.

Asking overweight people how much they weigh is like the police asking drunk drivers how much they have been drinking. Some might tell the truth, quite a number lie to make them look better and some are in denial and say something incorrect thinking it is right. The human factor makes the measurement "quality" unsuitable for any safety related usage.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

There is, we called it line speed when I was flying -- the speed at which you should be going by 1000 feet of roll. If you are not at that speed or higher, something is wrong and you should abort, which isn't that fun in a fully loaded aircraft. I don't have any experience with airliners but I suspect that the crew missed it on this takeoff. They should have noticed the slow acceleration and either aborted or gone to full throttle depending on where they were in the takeoff roll.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

My step-brother is an onsite supervisor helping to build the new AP1000 reactors at the Vogtle Electric Generating Plant.

He's constantly complaining about the paperwork, how every nut and bolt is documented, and how people are slow to sign-off on paperwork because they're afraid of the buck stopping with them if something breaks.

And yet _his_ projects (the boilers) are way ahead of schedule. Their the only ones ahead of schedule, in fact. Why? Because even though he complains about the red tape and meddling of regulators, he's actually incredibly smart, very hardworking, and he manages to whip the crews he supervises into shape. He doesn't half-ass anything, but he's courageous enough to make the hard decisions, including extra work, that keeps things on time and under budget.

Government (as well as corporate, for similar reasons) projects are expensive not because of paperwork and red tape, but because _real_ people drag their feet. And because they will use paperwork and similar frictions as an excuse for poor performance, rather than treating it as any other challenge one might encounter.

I couldn't even imagine the amount of graft and corner-cutting that would occur without the paperwork holding people's feet to the fire.

Most people are lazy most of the time. Most people don't take pride in their work most of the time. Civilization works because a minority of people prefer getting the job done to whinging, even if they complain almost as much as the next guy.

Re:Data data everywhere and not a drop to think

[gnasher719]

They make airplane sized scales...perhaps just build them into the taxiway and have a wireless communications to the plane of the weight.

How many times has the total weight been entered completely right? Do you think you can make the system that you propose work with a lower failure rate? Good luck.

Re:Data data everywhere and not a drop to think

[SuricouRaven]

The strain gauge would at least be fail-safe: If it's faulty then the numbers won't match and the plane isn't going up until the fault is repaired.

Planes are very reliable now, due largely to the extreme level of regulation to which they are subject. The most unreliable component is the pilot. You can't trust the pilot.

Re:Data data everywhere and not a drop to think

[Deadstick]

Some large aircraft can weigh themselves, with strain gages on the landing gear axles.

Re:Data data everywhere and not a drop to think

[Deadstick]

Because the aircraft can't measure its own weight.

Some of the larger ones can. They have strain gages on the landing gear axles.

(It would seem simpler to put pressure gages in the oleo struts, but static friction in the struts corrupts that.)

Re:Data data everywhere and not a drop to think

[robbak]

Oh, don't forget - 5. 'won't break'. And 6. 'Doesn't weigh too much'.

A load cell (or strain gauge) is a device that flexes depending on how much force is on it. They want to put this between the wheels and the suspension, and leave it there to take the impact forces of landing. It would only be a matter of time before one of these would develop metal fatigue, snaps during a heavy landing, and kill a plane-load of passengers.

Re:Data data everywhere and not a drop to think

[Deadstick]

The telescoping tubes that make up the strut have to contain a lot of pressure, which means tight seals, which means static friction corrupts the measurement.

A better way: https://www.sawe.org/papers/12...

Re:Data data everywhere and not a drop to think

[DarkOx]

I am not a pilot so I don't know but I am curious. In all the old war novels I read they just run the throttles to "take off power" and go.

Is there any reason you don't just slam the throttles open on a modern jetliner until you are off the ground? Why do anything other than make sure you are not 'to heavy' to make it before you run out of runway? What not just 'punch it'.

Re:Data data everywhere and not a drop to think

[DarkOx]

"take off power" does not have to be red lining it. I don't see why using running the engines up to some high but within operation specs should damage or prematurely ware them. I don't know anything about modern turbo fan engines though.

Re:Data data everywhere and not a drop to think

[lgw]

A load sensor installed on each landing gear would easily gather the current weight of the aircraft

Accurate to 3 significant digits? There's a wind blowing. How much lift is the plane getting from that right now?

Heck, strain gauges have issues with calibration in the first place, and calibration is important. They're off in a time-varying magnetic field. They have to be calibrated to temperature, and are off in a way directly proportional to temperature, so you have to measure temperature quite accurately. But temperature keeps changing, along with that wind that keeps changing the weight you measure, because, hey, wings.

But it's easy, right?

Re:Data data everywhere and not a drop to think

[thegarbz]

Any off the shelf strain gauge will do that.

Next question?

Re:Data data everywhere and not a drop to think

[thegarbz]

It's almost like you need a calibration point that you can rely on to reset the measurement. Something like an empty plane perhaps? Strain gauges are quite linear in operation.

As for wind, if a bit of wind generates enough lift that throws your measurement out enough to make take-off impossible, maybe humans should just stay on the ground and leave the flying to Evel Knievel.

It really is quite easy. So easy in fact that some planes are already equipped with them: https://www.sawe.org/papers/12...

Re:Data data everywhere and not a drop to think

[laurencetux]

yeah i kind of glossed over than bit since a lot of folks even here would not know a wheatstone bridge if somebody smashed them in the head with it.

Re:Data data everywhere and not a drop to think

[thegarbz]

WHAT "sensors"?

Ok since you want it spelled out to you: Strain gauges would be the obvious choice. The type used to weight fucking heavy things to begin with, the type used in mining applications to weigh the loads attached to draglines will easily withstand a luggage handler (whatever that means in the scheme of a sensor that can weigh up to 80T)

I am an instrument engineer. What you claim is impossible is not so. Actually it's not even difficult. ACTUALLY it's been since the late 1970s: https://www.sawe.org/papers/12...

Also you do realise you don't need to weigh the plane while it's flying right? Just a once off on the ground. If you actually needed to know the weight of the plane you can calculate that during flight based on fuel used as a plane is an otherwise closed system.

Any significantly advanced technology is indistinguishable from magic. Let's just go with that. I'm going to weigh the plane using magic.

Re:Data data everywhere and not a drop to think

[lgw]

Hospital beds don't usually have airfoils. You've got a wind, say, 8% of the aircraft's takeoff speed, gusting to 12%. The aircraft has wings. How does this all work again? Plus, the kind of sensors that work at this scale tend to be temperature sensitive, magnetic field sensitive, and hard to calibrate.

As usual, the stuff that /. armchair experts thought up in 5 minutes did, in fact, occur to the actual professionals designing these things. You could likely make an automatic system of some sort, but would it be more accurate than the current method, which works pretty well on average?

Re:Data data everywhere and not a drop to think

[thegarbz]

How many times has the total weight been entered completely right? Do you think you can make the system that you propose work with a lower failure rate? Good luck.

Oh you said entered. Don't say that. That word implies human action. Human action can be considered good for about 90% of the time. Sounds like a perfect situation for something to be replaced by a computer.

Don't over-estimate humans.

Re:Data data everywhere and not a drop to think

[PrimaryConsult]

You do know that a small aircraft can actually lift off the ground while parked when the wind is high enough, right? Weight on the gear at that point is 0 :).

And even a sufficiently stripped 747 will lift off the ground with no engines.

Re:Data data everywhere and not a drop to think

[Eythian]

Someone elsewhere commented that it's expensive in terms of maintenance, it costs fuel, it increases the chance of engine failure, things along those lines.

Re:Data data everywhere and not a drop to think

[Anonymous Coward]

I'm kind of disappointed no one answered you yet. Let me say right off the start, I'm not a pilot. That being said, I'm going to guess the decision to no use full throttle is based on the same reason many other decisions are made in the world: money. More thrust = higher fuel consumption. Why waste fuel? I'm guessing fuel is a pretty big part of an airliner's expense, as suggested by the fact several years ago they added a 'fuel surcharge' to make up for the fact fuel prices were going up.

Like I said, just a bunch of assumptions. It would be great to hear from someone who knows although this kind of decision, I'm guessing, is more a business/financial decision than a technical/engineering one.

Re:Data data everywhere and not a drop to think

[nitehawk214]

I suppose you are right and you could calculate it on the fly, but with the cost in dollars and lives on the line if something goes wrong, you have to be sure everything is right before you touch the throttles.

Re:Data data everywhere and not a drop to think

[lgw]

There's usually some fuel in the plane, and some cargo. Perhaps you could 0 it from time to time with an empty plane, but you don't have to do that today. In any case, your weight measurement will depend on your temperature measurement, but the temp of the sensor itself, so you'd need to measure that alongside the weight measurement.

Winds 10% of takeoff speed are common. But you only need enough to through off your sensors by 1% to be trouble. As a sanity check on what the pilot calculates (as was used in that example), it might make sense. But the existing system is clearly pretty accurate, as this sort of problem is rare.

Or, you could just realize that every time there's a /. article on anything technical, every armchair expert is sure they saw something in 5 minutes that the working professionals missed. No, really, they also thought of it in 5 minutes.

Re:Data data everywhere and not a drop to think

[nitehawk214]

Best thing to do is do both techniques.

Re:Data data everywhere and not a drop to think

[Mass Overkiller]

Depending on the environmental conditions, going "balls to the wall" on a modern jet without computer controls would likely wipe out the engines by over torquing them and overheating them. Modern engine controls keep the engines together. Basically what happens now is that the computer is programmed for the aircraft configuration and the computer says "max power is XYZ". Then pushing the throttles all the way forward only nets you Max Power of XYZ. Some systems have an override condition, provision or button/lever, but most throttle systems on take off are "set and forget". This is to keep the engines together and keep them from over spinning, overheating or over torquing. Modern jet engines have more power than necessary for take off and climb. If you notice right after take off, the engines spin down slightly. This is to prevent over heating and increase engine reliability.

Re:Data data everywhere and not a drop to think

[Budgreen]

all this technology exists, I work in the weighing industry. you could drop a single (long) scale across the taxiways to gather per wheel weight and accumulate it then beam the total to the plane through a wireless link, wifi, bluetooth. plane wouldn't even have to stop. they do have some smaller ones to weigh cargo.

the problem here is this all needs calculated before they taxi out and take off.

the problem with the strain gauges in the landing gear idea is two fold. temperature extremes, and calibration.

Re:Data data everywhere and not a drop to think

[Budgreen]

failsafe? not exactly

if one of the 3 strain gauges goes bad it can still give you a reading that seems reasonable when combined with the other two. they would need to be calibrated periodically to account for wear and fatigue.

I work on tanks with strain gauges that are regularly filled and drained with about 200k lbs of material regularly, and its not uncommon to see it drift by a few thousand pounds in a year due to wear, and this is in a relatively temperature stable environment.

Re:Data data everywhere and not a drop to think

[Budgreen]

cardinal makes nice stuff.

but if you laid a truck scale long ways across the taxiway you could weigh (axles) and their electronics will accumulate those 2 weights, tell you front, rear, total weight and transmit it any way you want.

Re:Data data everywhere and not a drop to think

[Pikoro]

Don't forget air temp, humidity, fuel tank placement, amount of reserve fuel, etc.. In the systems I work on, the Vx speeds aren't calculated automatically, they're supposed to be input by the pilot based on lookup tables.

Also, for the people talking about automatic calculation of these values, some weights are different than others. Fuel is a variable weight which changes during flight whereas passenger/cargo weights stay static. CG changes with angle of attack and acceleration which has to be taken into account when setting up initial spoiler and elevator settings for takeoff as well. It's not just a simple "Aircraft is 76k lbs"

Re:Data data everywhere and not a drop to think

[Budgreen]

wheel weighers... meant to be portable for spot checks, good luck not sliding a wheel off one when its rainy or snowy.

they are accurate and have their uses but day in day out is not one.

Re:Data data everywhere and not a drop to think

[Budgreen]

doubtful.

has to withstand the temperature swings *and* the shock loads of landing

Re:Data data everywhere and not a drop to think

[ChrisMaple]

A strain gauge is attached to the strut and its dimension changes just as much as the strut does. It shouldn't fail unless the strut fails. The weight should be miniscule, less than the wire used to hook up to it. Zeroing is simple; once the plane is aloft the force on the strut is a known minimum.

Re:Data data everywhere and not a drop to think

[jbwolfe]

In fact you can firewall it. All modern (since about the '80s) engines are computer controlled. The firewall position produces thrust as a function of mode. TOGA for takeoff and climb for, well, climb and cruise. Even idle thrust is a function of configuration- if the flaps are out or not, on the ground or not, is anti-ice on, is there a high demand for bleed air.

Re:Data data everywhere and not a drop to think

[turning in circles]

Actually, I was totally wrong; according to "pilot guide to takeoff safety," company policy is used to tell pilots how much thrust to use. (See Section 2.3.6).

Re:Data data everywhere and not a drop to think

[ls671]

We should make bigger overhead bins in the passenger compartment and eliminate the cargo space completely. This way, the luggage/cargo would be further from Earth center of mass so its weight would be less thus better fuel economy and easier take-offs ;-)

Re:Data data everywhere and not a drop to think

[ultranova]

Do you accelerate from every stop by pressing the gas pedal all the way to the floor or do you match how much gas you give it to the driving conditions and who and how many people are in your car?

I'm not trying to take-off from every stop. But when I am, for example when I'm about to join the highway, I do indeed floor the pedal.

Re:Data data everywhere and not a drop to think

[Lisandro]

There's a good number of reasons for this, and they're not immediately obvious.

- Optimize fuel usage; you want to burn only as much as you need on takeoff
- Reduce engine wear as much as possible. Engine overhauls are awfully expensive for airlines.
- Don't overthrust engines in case of failure. If an engine goes out on takeoff with too much airspeed the airplane might not be able to correct yaw before running out of runway.

On small piston aircrafts, yes, you usually go full power on takeoff every time. Airlines are a very different beast though.

Re:Data data everywhere and not a drop to think

[ls671]

> retrorocket.o not found, launch anyway?

Of course we launch anyway, what are you thinking???
And you are exaggerating anyway, it only has shrunk a little due to cold temperature.

Re:Data data everywhere and not a drop to think

[dave420]

Of course it does. Steering is acceleration, and clearly necessary to avoid crashing.

Re:Data data everywhere and not a drop to think

[stephanruby]

I don't know for sure, but I believe the pilots are supposed to *only* use the certified avionics systems in the aircraft

No, it's also important that they're able to make these kinds of calculations before they enter the cockpit as well.

...they use iPads even though they're really, really, really not supposed to.

iPads are not the problem. It's the fact that they didn't double check those results through another method that is really the problem.

Re:Data data everywhere and not a drop to think

[thegarbz]

You can doubt all you want. Strain gauges are used in many planes for expressly this purpose. They have been since the 70s. See the other links posted here.

These gauges are also inaccurate over changing temperatures but they are repeatable. It doesn't matter if they freeze while the plane is in the air as long as the measurement is consistent while they are on the ground. Even if you are flying from Siberia to the Sahara daily temperature compensation for sensing elements is a concept that has been around for the best part of 60 years. Also shock loads are not as bad as you think either. It's no like the entire force of the plane hits them, this is greatly reduced by shock absorbers and the fact that strain gauges that are built to measure in the range of 100T are actually damn shock resistant. If they can be used in swinging draglines then they'll withstand the minor abuse they may face in a plane.

Re:Data data everywhere and not a drop to think

[Big Hairy Ian]

Probably because the Boeing 737 is nearly 50 you'll be lucky to find an RS232 port

Re:Data data everywhere and not a drop to think

[dcw3]

You don't want a system automatically aborting when you might be running out of runway at 160kts.

Re:Data data everywhere and not a drop to think

[dcw3]

4 oh and btw you have to comp for temps from ALASKA to HAWAII

Does it weigh more cold or hot? Seriously though, what does temp have to do with weight calculation? Do the sensors readings change with temp?

Re:Data data everywhere and not a drop to think

[dcw3]

This seems like something the plane should be able to do all by itself. This is $50M aircraft. It should be at least as sophisticated as a hospital bed.

The first 737 was certified back in 1967, so a lot of the tech (unless it's been updated as most airlines do) is pretty old on some of these. There's a lot that planes should be able to do, but shit breaks, and pilots need to be able to deal with any contingency manually if possible.

Re:Data data everywhere and not a drop to think

[Archtech]

In view of the alternative (worst case, tail hits the ground hard enough to cause serious structural damage, tail falls off, everyone dies) it would be worth spending a little time and money on.

Thing of it is, people don't foresee that kind of contingency when they design a system as complicated as a jet airliner. No one says, "OK, what if the pilot is totting up the total takeoff weight in his head and makes an arithmetic error?" Nevertheless, it is certainly the kind of operation that deserves to be automated - perhaps, as someone has already suggested, just as a backup or safety check.

I'm reminded of a time many years ago when I went into a department store to buy a cheap alarm clock. The young sales assistant was obviously unfamiliar with his pocket calculator, and solemnly told me that the price of 25 pounds sterling, less 25 percent discount, was 33 pounds or something like that. I tried for some time to make him see that 25 pounds, with a discount, must be less than 25 pounds - but he could not see beyond the number displayed on his (incorrectly operated) calculator. Eventually I had to get a manager to sort it out.

That kind of simple arithmetic error should not be able to damage a huge airliner and (potentially) crash it.

Re:Data data everywhere and not a drop to think

[dcw3]

Then, shouldn't there be an optimum thrust that it's set at under all but abnormal situations? I realize this isn't the Cessna that I learned on, but why make a variable out of something that could normally be a constant?

Re:Data data everywhere and not a drop to think

[laurencetux]

it depends on the sensor and what said sensor is made of

Re:Data data everywhere and not a drop to think

[edtice1559]

Only for a plane of a certain weight. If I apply a certain amount of thrust to a 1kg object, it will go faster than if I apply it to a 10000 kg object. You expect a certain speed for a certain thrust and weight. But I think you're point is still valid, because you're not building ground speed at the expected rate. I still hope the OP comes back and comments as I'd like to think that the pilots could have known sooner that they weren't building enough speed. Then, adding thrust would have been easy.

Re:Data data everywhere and not a drop to think

[RoverDaddy]

Modern jet engines have more power than necessary for take off and climb.

This recent video demonstrated that nicely.

Re:Data data everywhere and not a drop to think

[swillden]

You failed to read the last sentence of my post.

Re:Data data everywhere and not a drop to think

[swillden]

+1

Re:Data data everywhere and not a drop to think

[stoatwblr]

Three words: Centre of Mass.

can a static weighstation calculate this?

Re:Data data everywhere and not a drop to think

[stoatwblr]

"Is there any reason you don't just slam the throttles open on a modern jetliner until you are off the ground?"

Firstly: In most parts of the world: Noise laws

Secondly: Going to 120% power dramatically shortens engine life so you only do it in an emergency (yes, you turn it up to 11, but there are tradeoffs). Engine overhauls are extremely expensive. Management frown on pilots who cost the company too much.

This was an aircraft that was 10 tons heavier than calculated - on a 737 that's easily a 15-20% variation on nominal MTOW. That makes a large difference to the rotate and liftoff velocities. These are precalculated based on the aircraft's assumed weight to give optimum climbout rate.

If you rotate early or overrotate, the aircraft takes longer to get to liftoff velocity. If you rotate late the ride is bumpy and that is bad for both the nerves of the passengers and the fatigue life of the airframe (late rotation is used in hot'n'high conditions or where you need to "spring" off the runway, but generally strongly discouraged). Taking longer to get to liftoff velocity may mean running out of runway.

The surprise is that they only kissed the tarmac. It must have been a long runway with an easy climbout. If they'd done that at Queenstown (where 737s have to fly out with the front 4 rows empty in order to be able to climb over terrain) this would have resulted in a messy smear mark over a nearby mountainside.

Re:Data data everywhere and not a drop to think

[multi io]

Why measure weight? All that's needed to know whether the plane will lift off is the current amount of thrust, the current speed and its acceleration.

The plane lifts off when its lift exceeds its weight. Its *weight*, see? The airspeed (and flaps setting) determines the lift; to determine the weight, you have to, well, weigh the thing.

Re:Data data everywhere and not a drop to think

[dcw3]

Yes, I confess having jumped the gun w/o reading your full post. Apologies.

Re:Data data everywhere and not a drop to think

[delt0r]

90% of wear and tear on a turbofan is at takeoff. So yea there are good economic reasons not to do this. But over all some pilots like to gun it anyway :D. Lets face it. It is fun.

Why do these data need to be entered manually?

[QuietLagoon]

Where do the pilots get the data? Is it displayed to them? Is it shouted at them as they board the plane?

.
Why can't the source of the data convey the data to the tablet apps automatically? Why involve an error-prone human in the process?

Re:Why do these data need to be entered manually?

[Anonymous Coward]

Why involve an error-prone human in the process?

Under the Pilots Union agreement the calculations will be handled by the pilot and check by the co-pilot. :P

Re:Why do these data need to be entered manually?

[Solandri]

Because if an automatic system fails in an "obvious" way and causes an accident, people here would be posting "why wasn't a human in the loop?"

In an ideal world, both automatic systems and people would complement each other with a person manually checking the automatic results. But in the real world, once you automate the system, people tend to get lazy and stop double-checking the automated system's calculations. NASA ran across the same problem - in the post-Challenger investigation they discovered that having multiple inspections actually decreased safety. Each inspector assumed the other was doing his job, so became more lax and sometimes didn't check things thoroughly or sometimes even skipped checks. Even in this incident, the pilot using the iPad didn't bother checking to make sure the number he entered into the iPad was the number he thought he typed. He just assumed the input method worked, despite everyone who's tried to type an email on a touch interface knowing that errors occur frequently.

So you end up with an either/or situation. Either the system has to be completely automated with the engineers trying to think up every possible scenario during design, and it'll still occasionally fail in ways you never thought of which will lead people to question why humans were left out of the loop. Or it has to be reliant on humans doing everything by hand, to ensure they take their job seriously and actually do it. Unless an automatic system has a track record showing decades of reliability (this is why computers on aircraft are usually more than a decade old), aerospace usually relies on humans.

Re:Why do these data need to be entered manually?

[jbwolfe]

Obtaining performance data requires knowing how many people and bags and where they are located, which runway is used, flap setting CG and weather data like pressure, winds and temperature. These factors, exclusive of the atmospheric conditions, are dictated by the humans operating the plane and while they could theoretically be automated, there likely isn't enough return on the invested effort to do so.

Re:Why do these data need to be entered manually?

[jbwolfe]

As a unionized airline pilot, I can assure you that your statement is completely false. I'd suggest that you visit here: http://alpa.org/ to get a better idea about the kinds of things that union has done to improve safety in the industry. Such as the following: science based duty limits, TCAS, Captains authority, security of the cockpit, hazardous cargo, safety reporting system, etc.

I suspect, sadly, that your bias against unions is an indicator that your mind is made up already.

Re:Why do these data need to be entered manually?

[RobinH]

This is exactly my thought. Either they have strain gauges in the landing gear to measure the weight directly, or they're calculating it from some indirect source like passenger load. Either way the value was already in a computer before that person messed it up.

Re:Why do these data need to be entered manually?

[umghhh]

Ah unions are at fault, why not directly Putin? Gee I came here years ago for the quality of comments also those at the lowers level now this gets modded up into /. mod-heaven and I am wondering what the hell is wrong with me that I spend time here.

Re:Why do these data need to be entered manually?

[sabbede]

It reminds me of old Heinlein novels from the pre-useful-computer era. Like Starman Jones where FTL calculations had to be solved in someone's head and the solution given to the computer.

Re:Why do these data need to be entered manually?

[Big Hairy Ian]

It's a 737 they've been around for like 50 years and you still can't get a decent coffee

So wrong data in Flight Management Controller

[Anonymous Coward]

So somebody entered bad data into the Flight Management Controller.

Happens all the time with Qantas, which has been caught out for having extremely lax protocols.

Search the ATSB database, there have been more than a dozen incidents in the past decade which by pure luck didn't result in mass casualties.

Then read the BS excuses Qantas gives. Such as "the ladder wasn't tall enough to check the engine cowling was locked".

Re:So wrong data in Flight Management Controller

[thegarbz]

People like picking on QANTAS for this, but the reality is that equal shit happens on all airlines. After all it wasn't a QANTAS plane which recently had the engine cowling fly off mid flight. And I say that for any of the several cases of this happening this year.

5%

[rfengr]

Seems to me 5% should be well within the margin or error. Are they trying to save fuel by cutting it that close?

Re:5%

[avandesande]

Yes that is a ridiculously small margin.... it's not hard to imagine a series of errors adding up to 5%. What about a sudden tail wind?

Re:5%

[fche]

Not just that ... it's weird that the pilot flying didn't monitor carefully enough the rotation angle. Sure, if she rotates early (due to wrong v1/power), there may not be an immediate lift-off -- so dip the nose down and use a bit of the remaining runway. (By this time they're past V1 so are committed to flying instead of stopping.)

Re:5%

[Anonymous Coward]

He meant a tailwind, you ignorant git. It's the velocity of air over the wings that causes lift. A sudden tailwind will reduce lift. Not knowing this just means you still have things to learn. Mouthing off about things you don't understand makes you an ignorant git.

Re:5%

[fluffernutter]

What about a hurricane?

Re:5%

[jbwolfe]

Performance data normally has a safety buffer built in. However, a 10,000kg error is not a variable that would fall into the margin or error for performance. The primary goal of reduced thrust is to extend the life of the engine. A secondary goal is to reduce the likelihood of a turbine failure.

Re:5%

[Talderas]

Headwinds are helpful for takeoff. Tailwinds are detrimental.

Re:5%

[Anonymous Coward]

It's not a "run out of fuel" saving, it's a saving of fuel on the takeoff (20,000 lbs of Jet-A per minute at full throttle) and engine life. It's also very good to not piss extra CO2 in the atmosphere, and there is a margin of safety built in, as they took off with scraped paint.

Re:5%

[Talderas]

To explain my comment.

Under no wind conditions you could expect a lighter plane to be travelling at 40mph when it takes off. It'll takeoff off after 200ft of runway. It will rise to an altitude of 101ft after 1000ft. Providing a 10mph headwind means it will have a ground speed of 30mph (-10mph), require 138ft of runway to takeoff (-62ft), and have an altitude of 140ft (+39ft) after 1000ft. Adding a 10mph tailwind would mean the plane will have a ground speed of 50mp (+10mph), require 384ft of runway to takeoff (+184ft), and have an altitude of 64ft (-35ft) after travelling 1000ft.

Re:5%

[Xenx]

I'm assuming they're talking about the 5% difference in thrust and not the error in the actual calculation.

As if...

[CanadianMacFan]

As if the co-pilot couldn't have made the exact same mistake with a calculator or even paper.

Re:As if...

[Mr D from 63]

As if the co-pilot couldn't have made the exact same mistake with a calculator or even paper.

The error could have happened regardless of the calculation tool as long as a human is entering the data. Inadequate verification of the information used seems to be at the heart of allowing the error to go unnoticed.

Re:As if...

[Misagon]

Sure, but an iPad has a touch-screen. Transposition errors are much more common on touch-screens than on proper keypads where you can feel when you have pressed a key - and where you can feel when you have pressed in-between two keys.
Real keypads even have a homing dot on the 5 key in the middle to make it easier to find the keys by touch.

Have you tried touch-typing on a tablet? That is an exercise in frustration, even if the tablet is really large, such as on a MS PixelSense.

Re:As if...

[fluffernutter]

I don't think it's that simple. It is a lot harder to make a mistake if you can feel the keys.

Re:As if...

[wonkey_monkey]

The error was that he pushed the wrong button, which, no, you can't do on paper.

Re:As if...

[edtice1559]

In accounting, they would call this an offsetting error. Two mistakes that cancelled each other out but still left the wrong answer. That seems a better name here. A transpositional error would be swapping two digits. $12.32 instead of $12.2.

Re:As if...

[cwsumner]

As if the co-pilot couldn't have made the exact same mistake with a calculator or even paper.

It seems like the Pilot did make a different mistake on paper, that resulted in a very similar value. So it looked like the value was verified, even though it was way wrong!

Re:As if...

[CanadianMacFan]

There were two errors. The first was not carrying a one which would have happened on paper or the iPad. The pushing the wrong button, or writing the wrong number, would not happen.

Why is a tablet signiifcant to this story?

[JoeyRox]

They could have just as easily mistyped the weight using the on-board flight management system's keyboard.

Re:Why is a tablet signiifcant to this story?

[tompaulco]

They could have just as easily mistyped the weight using the on-board flight management system's keyboard.

Yes, but one would hope that the FMS would make you enter all the numbers individually instead of just a total and have lots of error checking like (gee, are you sure you have a passenger count of 100, but the passenger weight is only 7000 pounds? Or, you have set the destination to BFE, but you did not enter enough fuel weight to get there with the required 45 minute reserve. Or, your luggage weight is several standard deviations off of what is expected given the passenger count.
Depending on the plane, it is not even just a total weight that has to be calculated. Center of Gravity calculations depend not just how many passengers there are, but how far from the center of lift they are, and the same for luggage and fuel.

Re:Why is a tablet signiifcant to this story?

[caseih]

The odds would be far less though. A keypad with actual, discrete buttons, is far, far more accurate for data input than a on-screen keyboard will ever be.

Re:Why is a tablet signiifcant to this story?

[Big Hairy Ian]

Surely the co-pilot wasn't allowed to use his IPad during take off and landing

"Transposition error"

[Nutria]

Is *not* an "off by one" error.

Re:"Transposition error"

[Red Flayer]

The other one transposed things so when they tried to enter 7XXXX they hit 6 by mistake.

But that's not a transposition error. A transposition error is when you type "47" instead of "74"... the two keystrokes are transposed.

Re:"Transposition error"

[Your.Master]

That's called a transcription error or typo, not a transposition error.

In a transposition error all the right keys are typed in the wrong order. In a transcription error, the wrong keys are pressed but otherwise the order is correct.

We all understand the summary, so on that level it worked, but we can't argue they used the right term because they didn't.

Re:"Transposition error"

[tompaulco]

In this case their fingers transposed the 7 for a 6, is the interpretation used here.

They transposed which key they were trying to hit without looking up from their calculations, resulting in hitting the wrong key.

But in the end the total matched the Captains total, so they nodded and carried on.

WolfWings, still here, yes I do check for replies occasionally, no I'm not signing in still to /.

They should lay it out like a calculator keyboard. You wouldn't be able to hit a 6 when going for a 7. This would result in an error so large that the computer would take notice.

That's why...

[CanadianMacFan]

you always have both the pilot and co-pilot make the calculations to make sure that they both come up with the same number. That is if you can't have the plane download and measure the necessary inputs in order to calculate the values for you automatically.

Re:That's why...

[BZ]

They did both do the calculation. The pilot did the arithmetic wrong and the copilot typed in his result wrong, and the upshot was that the numbers they entered independently agreed with each other... and were both wrong.

Re:That's why...

[craighansen]

Well, to be fair, that's the official report. I'd use Occam's razor and note that if the pilot did the arithmetic wrong and the copilot simply copied the pilot's calculation instead of doing it himself, the records would also match this explanation. Occam's razor cuts to the chase, even as it also cuts to the quick.

Forgot to carry the "1"

[Dunbal]

That is an arithmetic error, not a transposition error.

Re:Forgot to carry the "1"

[wonkey_monkey]

Now read the rest of the summary.

Where is there check?

[Rinikusu]

I used to be a Ramp Agent at a major international shipping firm. We did weight and balance for the flights. We had several layers of redundancy for our numbers: Every container number and weight was rechecked by another Ramp Agent, and then once again at the gate to match with the load sheets. We realized if we put the numbers in wrong, that could result in loss of life (not to mention aircraft assets and cargo). We took this job very seriously. Once we turned that paperwork (now done via ACARS, supposedly), I would hate to think that the cockpit just fat fingered the numbers in on their end without having a secondary check. "Hey Captain, can we check the numbers real quick?" Probably take them 15-30 seconds at most since they'd be concerned with big picture numbers and not individual positions.

Re:Where is there check?

[Anonymous Coward]

Believe it or not, flight schools make less money if someone does not complete the training and receive a Pilot Certificate. Also, flight examiners have become more lenient in recent years due to the "shortage" of pilots the big airlines keep complaining about (hint: if you don't want a shortage of pilots, pay pilots more than $10/hr).

It's a two-pronged problem. The low pay means competent people do not pursue careers in the cockpit. The lax standards mean that incompetent people who can't make more than $10/hr become pilots.

Re:Where is there check?

[wickerprints]

Both the captain and co-pilot did separate calculations. They just happened to make two different arithmetic errors that resulted in the same incorrect result, therefore failing to detect the error. The captain failed to carry a 1. The co-pilot type in a 6 instead of a 7.

What this incident shows is that automation or the use of computers to do calculations automatically, does not necessarily improve reliability. Independent and redundant systems are instrumental in reducing error, but basic vigilance and attention to detail frequently is the most effective means in preventing mistakes.

Re:Where is there check?

[dpidcoe]

I might have misread somewhere, but the impression I got is that one pilot fat fingered a number and just so happened to enter the same number that the other came up with by failure to carry a 1.

Re:Where is there check?

[Nidi62]

Both the captain and co-pilot did separate calculations. They just happened to make two different arithmetic errors that resulted in the same incorrect result, therefore failing to detect the error. The captain failed to carry a 1. The co-pilot type in a 6 instead of a 7.

What this incident shows is that automation or the use of computers to do calculations automatically, does not necessarily improve reliability. Independent and redundant systems are instrumental in reducing error, but basic vigilance and attention to detail frequently is the most effective means in preventing mistakes.

I may be wrong, but in my experience with commercial flights crews the pilots are trained to not only verbalize what they are doing but the other crew member is supposed to visually check and verbally repeat what is being done. So if the captain is putting in 70000lbs into the computer he should verbalize "weight 70000lbs" after which the FO should check to make sure that the entry was indeed "70000lbs" and verbally confirm so. If the weight does not match his calculations or what is in the system does not match what the CA then he should speak up. Sounds to me like this crew needs some additional work with CRM.

Re:Where is there check?

[Rinikusu]

This is exactly how we did it. I would call out my numbers one at a time, wait for confirmation (checking their copy), and continue. ", 1685" "check", etc. And yes, we would catch transposition errors t his way. Short-cutting this only saved less than a minute and the consequences were too "dire" to ignore. And then we'd do the same with fuel numbers, etc. Once our paperwork was double and triple checked, we'd sign off and hand to the crew to sign off on the numbers they needed to verify (fuel load, for example), they'd sign, and we'd be on our way. I always assumed the crew would also do a similar check with the numbers.

I really miss that job.

Why is the brand of tablet important?

[Anonymous Coward]

It seems like the summary writer is going out of their way to insinuate that the fact that it was an iPad had something to do with the Co-Pilot's gross incompetence.

#ipadlivesmatter

Re:Why is the brand of tablet important?

[tnk1]

Yes.

Garbage in, garbage out.

Re:Why is the brand of tablet important?

[Overzeetop]

Actually, it was a Microsoft Surface, but the FAA just calls it an iPad because that's the only brand of tablet they know. /s

Re:Why is the brand of tablet important?

[nitehawk214]

You may be on to something here.

http://apple.slashdot.org/stor...

amazing no ground scale or even strain gauges

[WindBourne]

Seriously, at this time, it would actually make sense for the manufacturers to design in weight happening automatically.

Re:amazing no ground scale or even strain gauges

[Lumpy]

And they could by putting load cells on the landing gear so the system knows exactly how much it weighs.

Re:amazing no ground scale or even strain gauges

[wonkey_monkey]

I'd have thought that adding anything to the landing gear which does nothing to help you land the plane would be a pretty dumb thing to do, engineering wise.

Re:amazing no ground scale or even strain gauges

[Lumpy]

Considering that 747's and 777's have them as an option when being ordered means that it's a good idea, engineering wise.
but then the stupidity of taking off at less than 100% throttle to save a little bit of fuel at the expense of increasing risk is also a pretty dumb thing to do, engineering wise.

Re:amazing no ground scale or even strain gauges

[jbwolfe]

There are variables other than weight that factor into the performance calculation: runway, flaps, CG, desired thrust reduction, atmospheric conditions. These things are variables programmed into the FMC during preflight by the pilot. While they could be automated onboard (most already are but externally), it is not likely there is an adequate return on the effort required to make it work.

Incidentally, the company I fly for has made significant effort to lessen the likelihood of this kind of error. Our performance is done by a centralized loadplanner and SCAP (Standardised Computerised Aircraft Performance) http://www.iata.org/whatwedo/workgroups/pages/scaptf.aspx. QANTAS apparently aren't using this. One feature alerts the pilots if they have requested data for a weight that is unexpected, but it still gives us the data. It essentially says "is this really what you wanted because I don't agree that is what you weigh."

Re:amazing no ground scale or even strain gauges

[jbwolfe]

I've flown both and I'm not aware of that feature. Not saying your wrong- just haven't heard of this. Wasn't on A320 either, flew them a lot. As for reduced thrust on takeoff, there are benefits to be gained. For example, the likelihood of turbine failure increases at higher thrust. Engine life is shortened by max thrust- has to do with sulfidation of the blades. Noise reduction (some airports levy fines like Orange County). Comfort. Also the fuel savings you mentioned, but not really such a big factor. That said, max thrust is required at least once every 30 days by certification, and sometimes the prudent pilot just wants the added performance for safety (wet runways, clutter, or just because ;)

Re:amazing no ground scale or even strain gauges

[Idarubicin]

...but then the stupidity of taking off at less than 100% throttle to save a little bit of fuel at the expense of increasing risk is also a pretty dumb thing to do, engineering wise.

Taking off at less than 100% throttle means reduced acceleration, which reduces stress on the airframe (and passengers). It reduces wear on the engines and - more important - reduces the risk of turbine failure. It makes the aircraft easier to control (less unbalanced thrust) if it does lose an engine immediately before or after takeoff.

So...not just to save fuel.

Re:amazing no ground scale or even strain gauges

[WindBourne]

really? The aircrafts require a max thrust every 30 days? Why is that?

Re:amazing no ground scale or even strain gauges

[WindBourne]

You missed the point. By having a strain gauge on the gears for doing weights, it allows for cross-checking. I doubt that any good pilot will give up total control.
Of course, I say that, and all of the airbus pilots do not actually fly the aircraft. It is a true computer controlled aircraft, with inputs from the pilots and other items.

Re:amazing no ground scale or even strain gauges

[nnull]

Still doesn't explain the tail strike. Why did the PIC pull the yoke back so hard that resulted in a tail strike?

Re:amazing no ground scale or even strain gauges

[ColaMan]

It's to ensure that the engine is capable of it and isn't suffering from some mechanical issue or slow decline.

That way if max thrust is needed in an emergency, the engines don't go bang when you really need them.

iPad?!?!?!

[Anonymous Coward]

Christ, even a server for a porn site has more error-checking hardware than an iPad.

"First, when working out the plane's takeoff weight on a notepad, the captain forgot to carry the "1," resulting in an erroneous weight of 66,400kg rather than 76,400kg.

Err, really, we're relying on mental arithmetic? Ok, fair enough as a backup, but then...

Second, the co-pilot made a "transposition error" when carrying out the same calculation on the Qantas on-board performance tool (OPT)—an iPad app for calculating takeoff speed, amongst other things. "Transposition error" is an investigatory euphemism for "he accidentally hit 6 on the keyboard rather than 7."

If the captain's working is being checked on the iPad, i.e. "same calculation", surely 76,400kg is an OUTPUT, not an INPUT. Was the co-pilot's "transposition error" such as to very coincidentally produce a 66,400kg output? Otherwise, the pilot and co-pilot's answers would be different, and they should have both started again.

"For a weight of 76,400kg and temperature of 35C, the engine thrust should've been set at 93.1 percent with a takeoff speed of 157 knots; instead, due to the errors, the thrust was set to 88.4 percent and takeoff speed was 146 knots."

11 knots and 4.9% thrust the difference between a safe take-off and a tailstrike? Christ, that's a narrow margin.

Re:iPad?!?!?!

[johnnys]

Once upon a time, there were the DC-8-61 and DC8-63 which were stretched several over 36 feet to a length that looked ridiculous. They put a hardpoint under the tail which could drag on the ground if the pilot overrotated, which was VERY common on that bird. (Also, sitting near the rear in turbulence was sphincter tightening as you could see the fuse was wobbling at least 6 feet sideways in random directions.)

I flew in one to France in 1973, and it dragged the tail *hard* on takeoff: There was no damage because of the hardpoint.

So if tailstrikes are a problem, quit screwing around and put a hardpoint there to protect the aircraft. If it worked on a DC-8 40 years ago, it can work on a piddly little 737 now, FFS.

Re:iPad?!?!?!

[jbwolfe]

After that they put great big CFM turbofans on them. First a tail strike followed by a pod strike!

Re:iPad?!?!?!

[Deadstick]

o if tailstrikes are a problem, quit screwing around and put a hardpoint there to protect the aircraft.

It's called a tailskid, and most airplanes have them...but there's a limit to how strong you can make them. A skid that will take a HARD tailstrike would need a prohibitive amount of structure above it, so they're designed to take a comparatively gentle scrape and crumple in a telltale way if it gets worse.

Why not 100% on takeoff?

[Lumpy]

Honestly flooring it is always the best option.

Re:Why not 100% on takeoff?

[The-Ixian]

To save on fuel costs?

Re:Why not 100% on takeoff?

[jklovanc]

Not just fuel but engine wear and air frame stress which reduces the life of the aircraft.

Siri

[chubs]

"Okay. I found 5 restaurants like 'calculate takeoff thrust' near you"

Human Error not Tablet Error

[vtn]

The tablet didn't miscalculate. The human did. In fact, tablets (or any technology) are great at math. To solve issue, automate the calculation and entering of the weight (or any other known information). People in the world all full of "I can't" or "it's not possible". But believe me, "it can happen" and "it is possible" to automate.

Gimli Glider

[jfdavis668]

At least they didn't run out of fuel like they did on the Gimli Glider.

Re:Gimli Glider

[jfdavis668]

But it didn't get to the ground without causing damage.

Re:ipads don't belong in the real world

[SuricouRaven]

I'd go for a very simple solution:
1. Pilot enters data.
2. Pilot hands to copilot.
3. Copilot enters data.
4. Pilot and copilot are forbidden from exchanging data until after the calculations are complete.
5. If both sets match, then ready for takeoff.

Qantas

[Anonymous Coward]

On a recent flight from SYD to MEL our Qantas pilot ranted on the PA about how evil the ATSB was because they wouldn't let the plane take off, because Qantas engineering accidentally put an incorrect black box into our plane. He said that Qantas maintenance made mistakes like that all the time, and that, since it wasn't a safety issue to fly without a black box, the ATSB were just being pricks.

I will never set foot on a Qantas plane ever agin.

Transposition error

[seven of five]

A transposition error's what you get when you mistakenly transpose 2 digits when typing a number, ie 5712 instead of 5172. If there's an error in the expected total of a set of numbers and the difference is divisible by 9, chances are good one of the numbers has a transposition error.

Re:Transposition error

[T.E.D.]

First, when working out the plane's takeoff weight on a notepad, the captain forgot to carry the "1," resulting in an erroneous weight of 66,400kg rather than 76,400kg. Second, the co-pilot made a "transposition error" when .... "Transposition error" is an investigatory euphemism for "he accidentally hit 6 on the keyboard rather than 7."

A transposition error would have been swapping the position of two adjacent glyphs, for instance coming up with "64,600".

Typing in a "7" when it should have been a "6" in the number "66,400" is a transcription error. Those are very different errors, typically caused by very different things.

Holy Flamebait headline Batman!

[Imazalil]

So human makes calculation on paper. The result is 66,400kg. Human then enters the same number onto a tablet.

Sure the human involved sucked at math and got the wrong result in the first place, but he copied the (wrong) result into the tablet perfectly fine.

How does this have anything to do with the tablet?

(yes, all this stuff should probably be automatically generated in this day and age, but that is a different discussion to have)

Re:Holy Flamebait headline Batman!

[Anonymous Coward]

You couldn't even read the summary? Two different people made two different errors while calculating the weight using two different methods, and happened to get the same result so the errors weren't caught. So there was a redundancy in place but in this very rare occurrence it didn't work.

Re:Holy Flamebait headline Batman!

[stoatwblr]

"Two different people made two different errors while calculating the weight using two different methods"

That's highly unlikely and probably an ass-covering excuse.

The more likely scenario is that one crewmember made an incorrect calculation and the other said "looks about right". Humans are humans, etc.

What I can guarantee is that both pilots will always crosscheck in future, no matter who they fly with. That degree of error would make the feel on takeoff "wrong" enough to be a brown-trouser moment.

Why ??

[mrlinux11]

Why is this not an automatically entered value with the ability to be manually changed, instead of having to be typed in all the time.

Fat Finger of Death

[KatchooNJ]

Imagine dying because someone fat fingered some figures on an iPad? I think most of us can testify that we are more likely to make a typo when typing on a touchscreen. Oof! Now the part with forgetting to carry the one is a whole 'nother issue. heh

clickbait title anyone?

[beltsbear]

This was not a tablet error. It was a math error.

real question

[NostalgiaForInfinity]

The real question is not really why this data has to be entered manually (instead of automatically), but why it is needed at all. You'd think that with all the sensors on an airplane, this sort of thing should be handled via automated control systems, based on actual measurements of how the plane is doing.

It might still be useful to enter the data, but only as a sanity check; that is, to identify when the plane isn't handling the way it should based on the weight that the crew things it actually has.

Insufficient safety margin

[gurps_npc]

Before you drive a 10,000 lb truck over a bridge, you make sure it is rated for 10,000 lbs.

That does not mean it can handle 10,000 lbs, it means it can handle MORE than 10,000 lbs - the excess is called a margin of safety. It can be expressed as a "factor of safety". If your factor of Safety is 2, then the engineer believes the bridge can handle twice the stated load.

For aircraft and spacecraft, the US government generally requires Factor of Safety of at least 1.2, but as high as 3 is common. That means that if the tire is expect to hold 10 tons, it was built to actually hold at least 12 tons. (All above info from Wikipedia)

Apparently the idiots that write these programs thought, hey, we don't need to use a reasonable Factor of Safety. They calculated they needed 93.1 units of thrust, but failed only 88.4. That means their Safety Factor was less than 1.12

If the morons had put in the expected margin of safety of 1.2, then the plane should have been able to take off even if they had only applied 77.67 units of thrust.

Clear failure of the programmer to build a sufficient margin of safety into their calculations

Re:Insufficient safety margin

[iggymanz]

No, 1.2 safety factor does not and cannot apply to thrusts for either rockets nor airplanes. Take some elementary physics and learn why.

Re:Insufficient safety margin

[gnasher719]

Apparently the idiots that write these programs thought, hey, we don't need to use a reasonable Factor of Safety. They calculated they needed 93.1 units of thrust, but failed only 88.4. That means their Safety Factor was less than 1.12

They didn't actually fail. The tail touched the ground. Someone noticed the noise, some sensor went off, but otherwise the airplane was absolutely fine.

Re:Insufficient safety margin

[gurps_npc]

You have a valid argument for Rockets - it's all about planned orbits, usually with a rather limited initial thrust and only minor course corrections. But that's because our power capabilities are so limited we are have no ability to build in a margin. Frankly, a truly mature space ship program would most likely use constant thrust at 1 G, with a turn around half way to slow down. It gets up places quicker and negates the major problems caused by low G.

But planes are ALREADY constant powered vehicles. They don't need to measure fuel by the gram, conserving it excessively. A 20% extra initial thrust at take off is a minor extra cost that provides a much needed margin of safety. The extra acceleration won't exceed structural limitations of the aircraft or the human cargo.

The plane should have pushed the fuel expenditure higher than the bare minimum.

Re:Insufficient safety margin

[im_thatoneguy]

Falcon 9 has engine 1-engine out capability almost on the launch pad. 9/8 = 1.12 (coincidence) but on the launch pad has a thrust-to-weight ratio of 1.18. It only takes a handful of seconds after liftoff to have burned enough fuel to reach 1.2. However it does take about 15 seconds before it could theoretically suffer 2-engine loss and *hover*. Certainly wouldn't make it to space but there is a time at which space craft definitely do have an abundance of engines for their thrust/weight ratio. Falcon 9 again actually starts throttling down before first stage shut-down.

Ummm. What?

[Brannon]

The tablet didn't make the error, the humans did.

And if you think you have to be rich to afford an iPad, well, then I guess you've had a tough, tough life.

define "tailstrike"

[Gravis Zero]

https://en.wikipedia.org/wiki/...

In aviation, a tailstrike is an event in which the rear end of an aircraft strikes the runway. This can happen during takeoff of a fixed-wing aircraft if the pilot pulls up too rapidly, leading to the rear end of the fuselage touching the runway. It can also occur during landing if the pilot raises the nose too aggressively. This is often the result of an attempt to land nearer to the runway threshold.

Re:define "tailstrike"

[sabbede]

Tailstrike (v): Slapping her ass whilst balls deep.

Re: Proves iPads are not reliable....

[Hognoxious]

The first line of a blues song - you always sing it two times. Two times.

Transposition Error?

[tompaulco]

What they described would be a transcription error. However, I submit that it was probably a CYA error. In other words, the pilot did the calculation wrong and the copilot did not check the pilots work, but saying that you did and just typed it in wrong is merely incompetence and carries less penalty than not doing your job, which is insubordination.

Re:ipads don't belong in the real world

[chadenright]

I'd go for a very simple solution: 1. Pilot enters data. 2. Pilot hands to copilot. 3. Copilot enters data. 4. Pilot and copilot are forbidden from exchanging data until after the calculations are complete. 5. If both sets match, then ready for takeoff.

This is exactly what happened. Both Pilot and Copilot made separate errors that resulted in their erroneous results matching.

Re:ipads don't belong in the real world

[tompaulco]

It's almost like ipads are a stupid, portable toy for rich morons and they don't belong in the real world like for example a workplace. My merchant services vendor massively screwed up my application a few years ago because that dumbass was using an ipad as well. It's almost like tablets are an inferior way to typing data into a computer system or something.

The FAA doesn't care whether you use pencil and paper, a calculator, an ipad or other device for weight and balance calculations. However, when you use a tool that obfuscates the math and just spits out an answer, you do not get the opportunity to sanity check the answer. If it came up with a number that was 13% over such as in this case, the pilot would probably overlook the error. Only if it came out significantly unusual, like half or twice the normal weight, would it be likely to register as a math error to the pilot.

Fucking use 100% thrust

[Bruha]

Are they trying to save money on takeoff wtf.

Re:Fucking use 100% thrust

[cwsumner]

Are they trying to save money on takeoff wtf.

Full thrust means a much greater chance of blowing up the engine on takeoff! That is a really Bad Thing...

Re:Fucking use 100% thrust

[hooiberg]

My sentiments exactly. Create a whirlpool in the tank, and get that shit off the ground.

Sad that the pilots even have to do this...

[FlyHelicopters]

Frankly, in 2015, it is a shame the pilots even have to do this...

You can have the airplane weigh itself, using sensors on the landing gear. Then it can take readings from the air (temp, pressure, etc.)

Then it can figure all this out with far less error than the humans can.

Wait a sec...

[sabbede]

Don't we still have to turn off our iPads on takeoff?

flight management

[Orgasmatron]

Too many tail strikes, and they are 99% avoidable, maybe 100%.

Most likely, in the next generation aircraft, the computer will override the pilot when too much pitch is requested too low.

The plane knows it is taking off, and it knows where the runway is (or a small radar can be added to the tail). "Stick back" will stop meaning "nose up" when the tail gets too close to the ground, and will instead start to mean "moar power". As the ground falls away, it will transition back.

Might not even need to wait for the next generation of planes. This could easily become a mandate shortly after the next tail strike that results in loss of life.

Pilot error, multiple parts

[ebvwfbw]

First error in calculation. Second error in not flying the airplane. If it doesn't look right, either add power or abort takeoff. These are basics, even for a 70 year old Cessna 140 tailwheel airplane.