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

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

[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

[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

[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

[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.

As if...

[CanadianMacFan]

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

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 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: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.