But both FADECs would consist of identical hardware and be running identical software correct? So despite the safety precautions, it is still theoretically possible that some command sent to them triggered the exact same bug in both, assuming an actual software or specification problem. (In systems like these a specification can be buggy) That would be one of my suspicions.
I'm not familiar with the B777 or the Trent engines, but on other aircraft the FADEC typically only receive quite simple commands. Those commands are pretty much universally independent between the two FADECs (i.e. if one command was screwy, it should only affect one FADEC. But even then, commands coming into the FADEC would normally be checked for validity. Thrust commands typically come from LVDT attached to the thrust levers in the cockpit. Other things like engine anti-ice commands typically are simply discrete inputs from cockpit switches, or commands via a data bus.
I'll bet you a case of beer that the AAIB report will state that something other than a FADEC software bug caused this accident.
My bet is on some other common cause, such as a fuel issue (water in fuel, or out of spec fuel freezing or gelling in the fuel system and restricting the fuel flow, etc).
The fact that the engines responded the same way, at the same time, strongly suggests a single point of failure in an electronic flight control system.
It is not nearly so simple. The design standards for transport category aircraft require that the engines and engine installations be designed so that single failures do not cause all engines to stop. For example, each engine would have its own separate Full Authority Digital Engine Control (somewhat like electronic fuel injection on your car), with each FADEC connected to separate sensors. A failure in one FADEC or one sensor would not affect both engines. See FAR 25.901(c)
For each powerplant and auxiliary power unit installation, it must be established that no single failure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane except that the failure of structural elements need not be considered if the probability of such failure is extremely remote.
In the event of a passenger jet crash, probability is that everyone will die. If everyone does not die, the statistics still favor a majority of the passengers being killed in the crash.
Sorry to burst your bubble, but the actual data from the NTSB shows that there is less than a 10% chance of a fatality in any single accident for scheduled US airline operations. The data from 1987 to 2006 shows a total of 628 accidents, but only 60 of those had any fatalities at all (Note: their definition of an accident is essentially "aircraft gets damaged, or anyone gets injured"). For the accidents with fatalities, an average of 36.6 people died per accident. Thus much less than half of the people on the aircraft die in each fatal accident. The data over that period shows 0.018 fatal accidents per 100,000 flights, or about one fatal accident in 5,500,000 flights.
The problem is much more difficult than simply certifying every cell phone design as safe. The problem is that a small number of cell phones might have shielding that becomes ineffective, either through a problem during manufacturing, or something that happens in service (dropped cell phone, cell phone disassembled and reassembled by curious geek, etc).
And, it is possible that the avionics or coax cabling in some aircraft might be not quite up to snuff. So, most aircraft of a given design are OK, when coupled with most cell phones. But put a defective cell phone in the right place in the right aircraft, and you could have a problem.
Several years ago I spoke with the captain of a Challenger business jet who told me an interesting story. They were in cruise, when suddenly the VOR indications in the cockpit started doing very strange things. He sent the copilot back in the cabin to see if anyone was using an electronic device. He found that the CEO's son was playing with a Game Boy. The Game Boy was turned OFF, and the VOR indications returned to normal. The Game Boy was turned back ON, and the VOR problems returned. Game Boy OFF for the rest of the flight.
91.817 Civil aircraft sonic boom.
(a) No person may operate a civil aircraft in the United States at a true flight Mach number greater than 1 except in compliance with conditions and limitations in an authorization to exceed Mach 1 issued to the operator under appendix B of this part.
So, even if you manage to solve the sonic boom issue, you still need to obtain an authorization from the FAA to operate at supersonic speeds over the US.
Autopilot Emergency Descent Mode (EDM) has not been required by any civil aviation authority. The Global Express was approved for operation at 51,000 ft before the EDM as available. The EDM was developed to meet customer requests. The Global Express (and similar large business jets) will never get a single-pilot approval. Single-pilot approvals are only given for much smaller, simpler aircraft (smaller Cessna Citations, etc).
As I understand the history, EDM was first developed for some Cessna Citations that could fly up to 51,000 ft. These aircraft don't have an autothrottle system, so the EDM can only achieve a slow descent, as it limits the speed to MMO/VMO. In reality I'm not convinced that the descent would be quick enough to save lives if the crew passed out before they could bring the thrust levers back. If they did pull the thrust to idle before passing out, they will need to wake up quickly enough during the level off at 15,000 ft to push the thrust back up before the aircraft stalls. But the presence of EDM made the customers feel better about flying at high altitude, so it helped sell aircraft.
The EDM on the Global Express (and the equivalent Gulfstream products) will use the autothrottle to pull the thrust to idle for the descent, and push them back up again to hold speed after the level off at 15,000 ft. The system (at least on the Global Express - I don't know about Gulfstream) isn't hooked into the speed brakes, so the descent is still a bit more leisurely than you would like, but it does offer a reasonable chance of survival. Of course, if the crew is following the regs and one pilot has the O2 mask on for operations above 41,000 ft, then there is no problem for super high altitude ops. And if the aircraft is at 41,000 ft or lower then no one will likely die if the EDM does its job.
I'm pretty sure that no current airliner has ever had a factory option for EDM, and I haven't heard of any after market mods either. It would be fairly expensive to develop EDM for retrofit to airliners, and airlines aren't going to spend the money unless mandated. I also agree that there are other bigger safety issues to solve first.
You need to read up on what's required to fly at those altitudes in those aircraft. I'd also like to see your references to where anyone says the autopilot in those three bizjets is automatically lowering the aircraft's altitude in response to a pressurization event, because I've never seen such references, and don't think such a system could get approved by the FAA.
I've flown at 51,000 ft in Cessna Citation X, Bombardier Global Express, and Global 5000, so I know very well what is required to fly at those altitudes. I did the Transport Canada flight testing to certify the autopilot Emergency Descent Mode on the Global Express. This mode has already been accepted by the FAA on several aircraft types, including the Cessna Citation Sovereign business jet. Read all about it in the report from Flight International.
Excerpt - Before descending to medium altitude, Bodlak explained the autopilot's emergency descent feature. At altitudes above 30,000 ft, with the autopilot engaged, a rise in cabin altitude to 13,500 ft will trigger the emergency descent mode. Once triggered, the autopilot will turn the aircraft 90 to the left and lower the nose to maintain MMO/VMO. Without pilot intervention, the autopilot will level the aircraft at 15,000 ft.
The autopilot Emergency Descent Mode doesn't take the aircraft all the way to the ground - it goes to 15,000 ft and levels the aircraft there. Yes, there are parts of the world where that will put you into the side of a mountain. But, if the crew gets their O2 masks on quickly like they should, they will be conscious, and they will take control. This mode only comes into play if they are unconscious, and then the slight chance they will hit a mountain is better odds than the certainty that they will die if the aircraft does not descend.
Why don't you use the International System of Units?
Because the radar altimeter aural callouts recorded by the Cockpit Voice Recorder were in feet, as were the aircraft's barometric and radar altimeters. The International System of Units isn't used that much in aviation, except in the former Warsaw Pact countries and in China, and perhaps a few other places. If you fly an aircraft in France, the home of the International System of Units, the altimeter will be marked in feet. International air traffic and the need to have a common system of units for Air Traffic Control has driven this. Safety has trumped politics.
But, I agree that I should have added metric values, for those who aren't pilots. The A320 in that accident ended up at about 10m above the runway before they tried to climb away.
The pilot had made a slow pass over the field, and when he tried to pull the plane up, the computer overrode his commands thinking he was trying to land, and that is why they crashed into the forest.
While there some conspiracy theories, as with many catastrophes, the generallyacceptedstory differs very substantially from the above.
The aircraft was flown at maximum angle of attack (AOA) at about 30-35 ft above the runway during an air show, with passengers on board. The pilot disconnected the autothrottle system, as its "alpha-floor" system would have automatically increased the engine thrust, preventing him from slowing the aircraft as much as he wanted. The aircraft eventually ended up at about 30-35 ft above the runway, with the engines at idle, and at the maximum allowable AOA.
The co-pilot noted that the obstacles ahead were higher than the aircraft, alerted the pilot, who pushed the thrust levers (i.e. throttles) ahead, and pulled back on the controls. The flight control system did not allow the pilot to raise the aircraft's nose, as that would have required increasing the angle of attack, and the wing would have stalled. The only way out of the hole he dug was to get more thrust. The faster you go at a given AOA, the more lift the wing produces. The fact that lift is now greater than the weight means the flight path starts to curve upwards, and the nose rises, even at the same AOA. But, it takes about 7 seconds for a modern high-bypass ratio turbofan engine to accelerate from idle to full thrust (the regulations allow 8 seconds), and they hit the trees 5 seconds after he pushed the thrust levers forward.
The flight control system's AOA limiting function prevented a much more serious accident, as if the wing had stalled the aircraft would have went out of control. As it was, it hit the trees in controlled flight, and only three people died.
After that, an emergency pilot override was placed in AirBus jets.
There is no emergency override in the Airbus jets. The pilot can manually turn off enough flight control computers to put the flight controls in Direct Law, where there are no longer any artificial limits on what he can do, but this would not have prevented this accident. He would have crashed much earlier in the sequence if he had tried to do the same thing in Direct Law.
The Boeing 777 can takeoff and land automatically.
The Boeing 777 cannot takeoff automatically. It can land automatically, as can all the other modern large airliners, including Airbus A320, A330 and A340.
1. There are already multiple possible failures that could cause a depressurization (cabin window failure, door failure, engine rotor burst, crew error, etc). The design requirements call for systems to alert the crew if the cabin altitude exceeds normal values, and there must be oxygen masks that they can don within 5 seconds. The operational requirements call for the crews to be properly trained in the use of these masks, etc. So even if this chip has a problem, it doesn't necessarily create a new safety issue. Of course, the problem, if it exists, should be corrected.
2. Some business jet aircraft do have an autopilot mode that will automatically descend the aircraft if the cabin altitude exceeds a certain value (several Cessna Citation models, some Gulfstream models, latest Bombardier Global Express, etc). These aircraft often cruise at altitudes up to 51,000 ft, which is quite a bit higher than the maximum altitude for the A380 (apparently 43,000 ft, but typical cruise altitudes will be lower than that). The smaller cabin volume of the business jets mean the cabin depressurizes much quicker, given a similar failure.
You've got to admire ESR. If a 12 yr old broke into our site and posted something that made us look like a complete jackass, most of us would have removed it, and then figured out how we got hacked. But ESR knew what a propaganda coup it would be if MS could say "FOSS is no more secure than our SW. If even a leader of the FOSS world can get hacked, how do you think you could be safe with FOSS?
ESR is going along with the 12 yr old's joke, and allowing himself to be made a fool of, rather than exposing a break-in of a major FOSS site.
The automatic control system failed on the last Mercury flight. Gordon Cooper switched to manual control for the reentry, and did such a great job that he splashed down about 4 miles from the recovery ship. See details.
Radio waves in certain frequency bands wil bounce off the ionosphere, and this is used to establish communications over very long distances. Higher frequency radio waves zip right through the ionosphere, so normally communciations are limited to line of sight. But, if there are temperature inversions in the atmosphere, it is possible to get conditions that will cause the radio waves to follow along the "duct" created by the inversions. More info
I ran into this twice, when many years ago when I was flying S-2 Trackers on maritime patrol missions in Canada. The first time we had departed St. John's, Newfoundland, heading east over the Atlantic. I had left the VHF Com radio tuned to the airport control tower frequency, as there was no one else I needed to talk to after I left their control zone. It was quiet on the radio after we went below the radio horizon from St. Johns. We were over 200 miles east of St. John's when I dropped down to 100 ft above the water to inspect a boat. Suddenly I could hear St. Johns control tower on the radio. After I finished the work at that boat I tried talking to St. John's tower, and they answered me. If I climbed up, I couldn't hear them, but at 100 ft they were as clear as a bell.
One other night we were cruising south at 1500 ft, on our way to a naval exercise. The radar operator said that his radar was painting a fleet of ships about 150 nm ahead of us, which would normally be well below the horizon at our altitude. I took the range and bearing he gave me and plotted it to get a lat and long. Sure enough, once we got closer we found that the naval fleet we were going to play with was right where he had said it was.
But, radio ducting is apparently not been seen at frequencies over 1.2 GHz, and is rare at frequencies over 50 MHz. Source
If you read the article on the Indian boy, he is supposedly an MCSE, while the Pakistani girl is supposedly an MCP. So, she may very well be the youngest MCP.
An 8 yr old MCSE - either he is one bright kid, or MCSE isn't soo tough, or everything you read on the internet isn't true. Pick one.
One might call the dropping of the price of MS's stock from above $120 to $20 within weeks of the judgment a negative result.
And when would this dramatic stock price drop have happened? The data I can find doesn't show this at all. Stock price history. Be sure to consider the effect of stock splits too.
Sure, sure, but they didn't test at full capacity? Cripes, that has nothing to do with bleeding edge engineering, that's just being in too damn big a hurry.
They need a very, very high fuel fraction (ratio of fuel weight to total weight) to have enough range. That means they need a very, very light structure. The fuel weight was 83% of the weight at take-off, and some of the other 17% was engine, cockpit instruments, avionics, pilot, fuel pumps, etc. So the actual structure weight was probably closer to 10% than it was to 17%. The aircraft was designed to take-off with full fuel once.
You can't do things like this by taking a conservative approach. Add enough structure weight to allow multiple take-offs at max weight, and now you don't have the range to go around the world.
If this was easy, some one else would have already done it.
I had a very interesting class on sonic booms when I was at test pilot school in France too many years ago. The sonic boom comes down from the aircraft at an angle that depends on the Mach number. As it comes down from 50,000 - 60,000 ft where the Concorde cruised, the air temperature warms up, which increases the speed of sound. The gradual increase in the speed of sound causes the boom to refract, and its angle of descent slowly shallows out. Under "standard" atmospheric conditions, Concorde's sonic boom in cruise would supposedly shallow out to where it was going level with the earth's surface, then refract so it was going upwards. It would go way up into the upper atmosphere, where the air temperature profile goes all wonky - the air temperature increases with altitude at high altitude. The boom would refract so that it was coming down hill again, but steeper this time. This secondary boom would hit the ground, but it had travelled so far that it was very weak.
A few years after test pilot school I was home visiting my folks in southern Nova Scotia. I was outside working with my Dad, when I noticed that he kept checking his watch. I asked him why he was worried about the time, and he said he was waiting for Concorde. He said that every day at about the same time he would hear a faint noise that he believed had something to do with Concorde. Sure enough, there was a very faint "boom". I wouldn't have noticed it if he hadn't mentioned it. I checked the BA and AF schedules, and the time that he always heard the boom was compatible with one of the flights.
So, if the atmosphere was always nice enough to follow the profile of the International Standard Atmosphere, and no one live on higher ground where the first sonic boom could hit, the Concorde could have flown over land with no problems. But, the atmosphere's temperature profile is often fairly non-standard, and some people live on the sides of mountains. Oh well.
747's (and most other triple autopilot aircraft) have been able to autoland for 30 years.
Actually, the first autoland in commercial service was in July 1965, by a HS 121 Trident, almost 40 years ago. Autoland was one of the great British developments in aviation.
You're not the only one suspecting that he did intend to perform a one or two turn roll... and that the roll turned out to be vastly more intense than he bargained for.
I really doubt he rolled it on purpose. Mike Melvill has been working as a full-time professional test pilot for over 20 years. You don't stay alive long in that business if you "hot dog" it by doing things on the spur of the moment. You stick to the test card. You are especially when you are working in a part of the envelope that is relatively untested - they were heavier than on earlier flights, and with a longer engine burn.
Well, if you'd RTFA you'd learn that they have a spare oxygen generator on the space station that can be installed as a replacement if necessary, plus they have a bunch of spare parts they can use to repair the one that is giving trouble. They have over a month's supply of chemical oxygen generators, and they have oxygen supplies in the Soyuz that is docked. So they have lots of redundancy here.
There has to be some limit to the amount of redundancy they have in any one system, as they only have so much weight and volume available, but they don't seem to have cut any corners in the area of O2.
Sure, they can try for the X-Prize with dummy passengers with the same mass as two adults, but I wonder... will Paul Allen and Burt Rutan be the passengers?
Well, I'm betting that the next flight has Mike Melville as pilot, as he has done the two highest altitude flights so far, and it is safest to have him do the first pax flight. But I bet one of the other previous SpaceShipOne pilots is a pax, as this would be a good work up to having him pilot later missions. And I bet Paul Allen gets the other seat. He has certainly paid enough money to have the seat if he wants it. And he probably wants it pretty bad, or he wouldn't have put up as much money as he has.
In an aircraft, excessive g forces cause blackout because the eye and brain need a certain minimum blood pressure to function. The heart creates the blood pressure, and the pressure at the eye and brain is lower (assuming they are higher than the heart). If you pull some g in an aircraft, the blood pressure at the eye and brain decreases. The eye is more sensitive to low blood pressure than the brain, so if you slowly increase the g, you start to get lose colour vision, get tunnel vision, and then lose vision completely, but you are still conscious. Pull more g and you loss consciousness.
An untrained, fit individual will probably loss consciousness somewhere between 3 and 5 g, if the g is sustained for more than a few seconds. Military pilots and aerobatic pilots are taught ways to temporarily increase the blood pressure by straining the leg and abdomen muscles, and "grunting" against a closed glottis. Modern fighter aircraft are designed to manoeuvre at up to about 9g (exact limits vary with different aircraft types). They are fitted with g-suits which fit tightly around the pilot's legs and abdomen. The suit inflates as a function of the g-level, and it helps keep the blood from pooling in the legs and abdomen, and thus helps keep the blood pressure up. But, older fighters, many military trainers and aerobatic aircraft, don't have g-suits. A properly trained and fit pilot can do sustained manoeuvring at more than 7 g. I did a structural loads flight test program on the Canadair CT-114 Tutor many years ago which involved quite a few test points at the aircraft's limit of 7.33g, without a g-suit.
The g level that can be sustained depends on fitness and training, but also on the axis of the acceleration. For example, if the aircraft accelerates forward, the axis of acceleration is such that it has no effect on the blood pressure in the head, as the acceleration is on an axis at 90 degrees to a line drawn from the heart to the head. So, 3.5 g during the ascent of SpaceShipOne would be of no consequence at all.
If you have some fluid in a vessel, the pressure varies with the vertical location due to the head pressure from gravity (or acceleration). I.e. the pressure is highest at the bottom of the container, and lowest at the top.
But does putting the mass of 3 humans in suborbital flight really make a difference? This is akin to the Space Shuttle in the 1970s: It's designed to go somewhere, but there's nothing up there to go to.
If we had waited until Boeing developed the 747 before flying the Atlantic the 747 would never have been developed. Be patient, one step at a time.
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I'm not familiar with the B777 or the Trent engines, but on other aircraft the FADEC typically only receive quite simple commands. Those commands are pretty much universally independent between the two FADECs (i.e. if one command was screwy, it should only affect one FADEC. But even then, commands coming into the FADEC would normally be checked for validity. Thrust commands typically come from LVDT attached to the thrust levers in the cockpit. Other things like engine anti-ice commands typically are simply discrete inputs from cockpit switches, or commands via a data bus.
I'll bet you a case of beer that the AAIB report will state that something other than a FADEC software bug caused this accident.
My bet is on some other common cause, such as a fuel issue (water in fuel, or out of spec fuel freezing or gelling in the fuel system and restricting the fuel flow, etc).
It is not nearly so simple. The design standards for transport category aircraft require that the engines and engine installations be designed so that single failures do not cause all engines to stop. For example, each engine would have its own separate Full Authority Digital Engine Control (somewhat like electronic fuel injection on your car), with each FADEC connected to separate sensors. A failure in one FADEC or one sensor would not affect both engines. See FAR 25.901(c)
For each powerplant and auxiliary power unit installation, it must be established that no single failure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane except that the failure of structural elements need not be considered if the probability of such failure is extremely remote.In the event of a passenger jet crash, probability is that everyone will die. If everyone does not die, the statistics still favor a majority of the passengers being killed in the crash.
Sorry to burst your bubble, but the actual data from the NTSB shows that there is less than a 10% chance of a fatality in any single accident for scheduled US airline operations. The data from 1987 to 2006 shows a total of 628 accidents, but only 60 of those had any fatalities at all (Note: their definition of an accident is essentially "aircraft gets damaged, or anyone gets injured"). For the accidents with fatalities, an average of 36.6 people died per accident. Thus much less than half of the people on the aircraft die in each fatal accident. The data over that period shows 0.018 fatal accidents per 100,000 flights, or about one fatal accident in 5,500,000 flights.
The problem is much more difficult than simply certifying every cell phone design as safe. The problem is that a small number of cell phones might have shielding that becomes ineffective, either through a problem during manufacturing, or something that happens in service (dropped cell phone, cell phone disassembled and reassembled by curious geek, etc).
And, it is possible that the avionics or coax cabling in some aircraft might be not quite up to snuff. So, most aircraft of a given design are OK, when coupled with most cell phones. But put a defective cell phone in the right place in the right aircraft, and you could have a problem.
Several years ago I spoke with the captain of a Challenger business jet who told me an interesting story. They were in cruise, when suddenly the VOR indications in the cockpit started doing very strange things. He sent the copilot back in the cabin to see if anyone was using an electronic device. He found that the CEO's son was playing with a Game Boy. The Game Boy was turned OFF, and the VOR indications returned to normal. The Game Boy was turned back ON, and the VOR problems returned. Game Boy OFF for the rest of the flight.
Also see another report of problem caused by Game Boy.
If they ever come up with a way to turn fine British beer into Budwiser I'll let you know.
That's easy - all you need to do is drink it, wait an hour or two ...
The FAA restricts the noise not the speed of aircraft going over the US, so keep it quiet and you can go as fast as you want.
Wrong. Take a look at Federal Aviation Regulation 91.817
91.817 Civil aircraft sonic boom.
(a) No person may operate a civil aircraft in the United States at a true flight Mach number greater than 1 except in compliance with conditions and limitations in an authorization to exceed Mach 1 issued to the operator under appendix B of this part.
So, even if you manage to solve the sonic boom issue, you still need to obtain an authorization from the FAA to operate at supersonic speeds over the US.
Autopilot Emergency Descent Mode (EDM) has not been required by any civil aviation authority. The Global Express was approved for operation at 51,000 ft before the EDM as available. The EDM was developed to meet customer requests. The Global Express (and similar large business jets) will never get a single-pilot approval. Single-pilot approvals are only given for much smaller, simpler aircraft (smaller Cessna Citations, etc).
As I understand the history, EDM was first developed for some Cessna Citations that could fly up to 51,000 ft. These aircraft don't have an autothrottle system, so the EDM can only achieve a slow descent, as it limits the speed to MMO/VMO. In reality I'm not convinced that the descent would be quick enough to save lives if the crew passed out before they could bring the thrust levers back. If they did pull the thrust to idle before passing out, they will need to wake up quickly enough during the level off at 15,000 ft to push the thrust back up before the aircraft stalls. But the presence of EDM made the customers feel better about flying at high altitude, so it helped sell aircraft.
The EDM on the Global Express (and the equivalent Gulfstream products) will use the autothrottle to pull the thrust to idle for the descent, and push them back up again to hold speed after the level off at 15,000 ft. The system (at least on the Global Express - I don't know about Gulfstream) isn't hooked into the speed brakes, so the descent is still a bit more leisurely than you would like, but it does offer a reasonable chance of survival. Of course, if the crew is following the regs and one pilot has the O2 mask on for operations above 41,000 ft, then there is no problem for super high altitude ops. And if the aircraft is at 41,000 ft or lower then no one will likely die if the EDM does its job.
I'm pretty sure that no current airliner has ever had a factory option for EDM, and I haven't heard of any after market mods either. It would be fairly expensive to develop EDM for retrofit to airliners, and airlines aren't going to spend the money unless mandated. I also agree that there are other bigger safety issues to solve first.
You need to read up on what's required to fly at those altitudes in those aircraft. I'd also like to see your references to where anyone says the autopilot in those three bizjets is automatically lowering the aircraft's altitude in response to a pressurization event, because I've never seen such references, and don't think such a system could get approved by the FAA.
I've flown at 51,000 ft in Cessna Citation X, Bombardier Global Express, and Global 5000, so I know very well what is required to fly at those altitudes. I did the Transport Canada flight testing to certify the autopilot Emergency Descent Mode on the Global Express. This mode has already been accepted by the FAA on several aircraft types, including the Cessna Citation Sovereign business jet. Read all about it in the report from Flight International.
Excerpt - Before descending to medium altitude, Bodlak explained the autopilot's emergency descent feature. At altitudes above 30,000 ft, with the autopilot engaged, a rise in cabin altitude to 13,500 ft will trigger the emergency descent mode. Once triggered, the autopilot will turn the aircraft 90 to the left and lower the nose to maintain MMO/VMO. Without pilot intervention, the autopilot will level the aircraft at 15,000 ft.
The autopilot Emergency Descent Mode doesn't take the aircraft all the way to the ground - it goes to 15,000 ft and levels the aircraft there. Yes, there are parts of the world where that will put you into the side of a mountain. But, if the crew gets their O2 masks on quickly like they should, they will be conscious, and they will take control. This mode only comes into play if they are unconscious, and then the slight chance they will hit a mountain is better odds than the certainty that they will die if the aircraft does not descend.
Why don't you use the International System of Units?
Because the radar altimeter aural callouts recorded by the Cockpit Voice Recorder were in feet, as were the aircraft's barometric and radar altimeters. The International System of Units isn't used that much in aviation, except in the former Warsaw Pact countries and in China, and perhaps a few other places. If you fly an aircraft in France, the home of the International System of Units, the altimeter will be marked in feet. International air traffic and the need to have a common system of units for Air Traffic Control has driven this. Safety has trumped politics.
But, I agree that I should have added metric values, for those who aren't pilots. The A320 in that accident ended up at about 10m above the runway before they tried to climb away.
The pilot had made a slow pass over the field, and when he tried to pull the plane up, the computer overrode his commands thinking he was trying to land, and that is why they crashed into the forest.
While there some conspiracy theories, as with many catastrophes, the generally accepted story differs very substantially from the above.
The aircraft was flown at maximum angle of attack (AOA) at about 30-35 ft above the runway during an air show, with passengers on board. The pilot disconnected the autothrottle system, as its "alpha-floor" system would have automatically increased the engine thrust, preventing him from slowing the aircraft as much as he wanted. The aircraft eventually ended up at about 30-35 ft above the runway, with the engines at idle, and at the maximum allowable AOA.
The co-pilot noted that the obstacles ahead were higher than the aircraft, alerted the pilot, who pushed the thrust levers (i.e. throttles) ahead, and pulled back on the controls. The flight control system did not allow the pilot to raise the aircraft's nose, as that would have required increasing the angle of attack, and the wing would have stalled. The only way out of the hole he dug was to get more thrust. The faster you go at a given AOA, the more lift the wing produces. The fact that lift is now greater than the weight means the flight path starts to curve upwards, and the nose rises, even at the same AOA. But, it takes about 7 seconds for a modern high-bypass ratio turbofan engine to accelerate from idle to full thrust (the regulations allow 8 seconds), and they hit the trees 5 seconds after he pushed the thrust levers forward.
The flight control system's AOA limiting function prevented a much more serious accident, as if the wing had stalled the aircraft would have went out of control. As it was, it hit the trees in controlled flight, and only three people died.
After that, an emergency pilot override was placed in AirBus jets.
There is no emergency override in the Airbus jets. The pilot can manually turn off enough flight control computers to put the flight controls in Direct Law, where there are no longer any artificial limits on what he can do, but this would not have prevented this accident. He would have crashed much earlier in the sequence if he had tried to do the same thing in Direct Law.
The Boeing 777 can takeoff and land automatically.
The Boeing 777 cannot takeoff automatically. It can land automatically, as can all the other modern large airliners, including Airbus A320, A330 and A340.
1. There are already multiple possible failures that could cause a depressurization (cabin window failure, door failure, engine rotor burst, crew error, etc). The design requirements call for systems to alert the crew if the cabin altitude exceeds normal values, and there must be oxygen masks that they can don within 5 seconds. The operational requirements call for the crews to be properly trained in the use of these masks, etc. So even if this chip has a problem, it doesn't necessarily create a new safety issue. Of course, the problem, if it exists, should be corrected.
2. Some business jet aircraft do have an autopilot mode that will automatically descend the aircraft if the cabin altitude exceeds a certain value (several Cessna Citation models, some Gulfstream models, latest Bombardier Global Express, etc). These aircraft often cruise at altitudes up to 51,000 ft, which is quite a bit higher than the maximum altitude for the A380 (apparently 43,000 ft, but typical cruise altitudes will be lower than that). The smaller cabin volume of the business jets mean the cabin depressurizes much quicker, given a similar failure.
You've got to admire ESR. If a 12 yr old broke into our site and posted something that made us look like a complete jackass, most of us would have removed it, and then figured out how we got hacked. But ESR knew what a propaganda coup it would be if MS could say "FOSS is no more secure than our SW. If even a leader of the FOSS world can get hacked, how do you think you could be safe with FOSS?
ESR is going along with the 12 yr old's joke, and allowing himself to be made a fool of, rather than exposing a break-in of a major FOSS site.
Way to go ESR!
The automatic control system failed on the last Mercury flight. Gordon Cooper switched to manual control for the reentry, and did such a great job that he splashed down about 4 miles from the recovery ship. See details.
Radio waves in certain frequency bands wil bounce off the ionosphere, and this is used to establish communications over very long distances. Higher frequency radio waves zip right through the ionosphere, so normally communciations are limited to line of sight. But, if there are temperature inversions in the atmosphere, it is possible to get conditions that will cause the radio waves to follow along the "duct" created by the inversions. More info
I ran into this twice, when many years ago when I was flying S-2 Trackers on maritime patrol missions in Canada. The first time we had departed St. John's, Newfoundland, heading east over the Atlantic. I had left the VHF Com radio tuned to the airport control tower frequency, as there was no one else I needed to talk to after I left their control zone. It was quiet on the radio after we went below the radio horizon from St. Johns. We were over 200 miles east of St. John's when I dropped down to 100 ft above the water to inspect a boat. Suddenly I could hear St. Johns control tower on the radio. After I finished the work at that boat I tried talking to St. John's tower, and they answered me. If I climbed up, I couldn't hear them, but at 100 ft they were as clear as a bell.
One other night we were cruising south at 1500 ft, on our way to a naval exercise. The radar operator said that his radar was painting a fleet of ships about 150 nm ahead of us, which would normally be well below the horizon at our altitude. I took the range and bearing he gave me and plotted it to get a lat and long. Sure enough, once we got closer we found that the naval fleet we were going to play with was right where he had said it was.
But, radio ducting is apparently not been seen at frequencies over 1.2 GHz, and is rare at frequencies over 50 MHz. Source
If you read the article on the Indian boy, he is supposedly an MCSE, while the Pakistani girl is supposedly an MCP. So, she may very well be the youngest MCP.
An 8 yr old MCSE - either he is one bright kid, or MCSE isn't soo tough, or everything you read on the internet isn't true. Pick one.
One might call the dropping of the price of MS's stock from above $120 to $20 within weeks of the judgment a negative result.
And when would this dramatic stock price drop have happened? The data I can find doesn't show this at all. Stock price history. Be sure to consider the effect of stock splits too.
Sure, sure, but they didn't test at full capacity? Cripes, that has nothing to do with bleeding edge engineering, that's just being in too damn big a hurry.
They need a very, very high fuel fraction (ratio of fuel weight to total weight) to have enough range. That means they need a very, very light structure. The fuel weight was 83% of the weight at take-off, and some of the other 17% was engine, cockpit instruments, avionics, pilot, fuel pumps, etc. So the actual structure weight was probably closer to 10% than it was to 17%. The aircraft was designed to take-off with full fuel once.
You can't do things like this by taking a conservative approach. Add enough structure weight to allow multiple take-offs at max weight, and now you don't have the range to go around the world.
If this was easy, some one else would have already done it.
Burt was the first with an airplane...
That would be Dick Rutan who flew around the world, not Burt.
I had a very interesting class on sonic booms when I was at test pilot school in France too many years ago. The sonic boom comes down from the aircraft at an angle that depends on the Mach number. As it comes down from 50,000 - 60,000 ft where the Concorde cruised, the air temperature warms up, which increases the speed of sound. The gradual increase in the speed of sound causes the boom to refract, and its angle of descent slowly shallows out. Under "standard" atmospheric conditions, Concorde's sonic boom in cruise would supposedly shallow out to where it was going level with the earth's surface, then refract so it was going upwards. It would go way up into the upper atmosphere, where the air temperature profile goes all wonky - the air temperature increases with altitude at high altitude. The boom would refract so that it was coming down hill again, but steeper this time. This secondary boom would hit the ground, but it had travelled so far that it was very weak.
A few years after test pilot school I was home visiting my folks in southern Nova Scotia. I was outside working with my Dad, when I noticed that he kept checking his watch. I asked him why he was worried about the time, and he said he was waiting for Concorde. He said that every day at about the same time he would hear a faint noise that he believed had something to do with Concorde. Sure enough, there was a very faint "boom". I wouldn't have noticed it if he hadn't mentioned it. I checked the BA and AF schedules, and the time that he always heard the boom was compatible with one of the flights.
So, if the atmosphere was always nice enough to follow the profile of the International Standard Atmosphere, and no one live on higher ground where the first sonic boom could hit, the Concorde could have flown over land with no problems. But, the atmosphere's temperature profile is often fairly non-standard, and some people live on the sides of mountains. Oh well.
747's (and most other triple autopilot aircraft) have been able to autoland for 30 years.
Actually, the first autoland in commercial service was in July 1965, by a HS 121 Trident, almost 40 years ago. Autoland was one of the great British developments in aviation.
See the slide, "Brief History of Category 3" in this presentation.
HS 121 on Wikipedia.
You're not the only one suspecting that he did intend to perform a one or two turn roll... and that the roll turned out to be vastly more intense than he bargained for.
I really doubt he rolled it on purpose. Mike Melvill has been working as a full-time professional test pilot for over 20 years. You don't stay alive long in that business if you "hot dog" it by doing things on the spur of the moment. You stick to the test card. You are especially when you are working in a part of the envelope that is relatively untested - they were heavier than on earlier flights, and with a longer engine burn.
Well, if you'd RTFA you'd learn that they have a spare oxygen generator on the space station that can be installed as a replacement if necessary, plus they have a bunch of spare parts they can use to repair the one that is giving trouble. They have over a month's supply of chemical oxygen generators, and they have oxygen supplies in the Soyuz that is docked. So they have lots of redundancy here.
There has to be some limit to the amount of redundancy they have in any one system, as they only have so much weight and volume available, but they don't seem to have cut any corners in the area of O2.
Sure, they can try for the X-Prize with dummy passengers with the same mass as two adults, but I wonder... will Paul Allen and Burt Rutan be the passengers?
Well, I'm betting that the next flight has Mike Melville as pilot, as he has done the two highest altitude flights so far, and it is safest to have him do the first pax flight. But I bet one of the other previous SpaceShipOne pilots is a pax, as this would be a good work up to having him pilot later missions. And I bet Paul Allen gets the other seat. He has certainly paid enough money to have the seat if he wants it. And he probably wants it pretty bad, or he wouldn't have put up as much money as he has.
In an aircraft, excessive g forces cause blackout because the eye and brain need a certain minimum blood pressure to function. The heart creates the blood pressure, and the pressure at the eye and brain is lower (assuming they are higher than the heart). If you pull some g in an aircraft, the blood pressure at the eye and brain decreases. The eye is more sensitive to low blood pressure than the brain, so if you slowly increase the g, you start to get lose colour vision, get tunnel vision, and then lose vision completely, but you are still conscious. Pull more g and you loss consciousness.
An untrained, fit individual will probably loss consciousness somewhere between 3 and 5 g, if the g is sustained for more than a few seconds. Military pilots and aerobatic pilots are taught ways to temporarily increase the blood pressure by straining the leg and abdomen muscles, and "grunting" against a closed glottis. Modern fighter aircraft are designed to manoeuvre at up to about 9g (exact limits vary with different aircraft types). They are fitted with g-suits which fit tightly around the pilot's legs and abdomen. The suit inflates as a function of the g-level, and it helps keep the blood from pooling in the legs and abdomen, and thus helps keep the blood pressure up. But, older fighters, many military trainers and aerobatic aircraft, don't have g-suits. A properly trained and fit pilot can do sustained manoeuvring at more than 7 g. I did a structural loads flight test program on the Canadair CT-114 Tutor many years ago which involved quite a few test points at the aircraft's limit of 7.33g, without a g-suit.
The g level that can be sustained depends on fitness and training, but also on the axis of the acceleration. For example, if the aircraft accelerates forward, the axis of acceleration is such that it has no effect on the blood pressure in the head, as the acceleration is on an axis at 90 degrees to a line drawn from the heart to the head. So, 3.5 g during the ascent of SpaceShipOne would be of no consequence at all.
If you have some fluid in a vessel, the pressure varies with the vertical location due to the head pressure from gravity (or acceleration). I.e. the pressure is highest at the bottom of the container, and lowest at the top.
But does putting the mass of 3 humans in suborbital flight really make a difference? This is akin to the Space Shuttle in the 1970s: It's designed to go somewhere, but there's nothing up there to go to.
If we had waited until Boeing developed the 747 before flying the Atlantic the 747 would never have been developed. Be patient, one step at a time.