Comments on: The Crash of Flight 447 https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/ Sat, 10 Dec 2011 23:55:40 +0000 hourly 1 https://wordpress.org/?v=6.4.8 By: MadScientist https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510146 Sat, 10 Dec 2011 23:55:40 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510146 That was such a depressing read. When it was announced long ago that engineers suspected the air speed indicator was iced and not working I was telling my buddies that still doesn’t make sense – landing without the air speed indicator is a bitch but level flight is trivial. Basically the pilot in command stalled the aircraft and kept it in a stall. If the idiot had only let go of the yoke the aircraft would have gently adjusted itself and maintained altitude. It reads like the sort of jokes you’d hear in training: “I don’t understand why we’re stalled, I’m pulling the nose up as far as I can.” The more senior first officer wasn’t any better; he was trusting the idiot to do the right thing (and the idiot continued to pull back on the yoke despite being instructed multiple times to descend, which should be interpreted as ‘push the yoke forward ever so slightly’). If he had only checked the attitude indicators he should have realized that someone was pulling back on the yoke. I didn’t know Airbus had yokes which acted independently. At least on a Boeing you know someone’s fiddling with the control and you can scream at them. The article also states that the Airbus averages the input from the 2 yokes – I wonder if that’s true and why the system would ever be designed that way.

]]> By: Greg Laden https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510145 Sat, 10 Dec 2011 16:26:59 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510145 The lesson from TMI was to desing the alarm system so that important alarms turn off less important ones. The operators have a better chance of understanding the situation when they are not distracted by secondary events.

Yeah, but hold on a sec here! The alarm that was sounding of flight 447 was the stall alarm. The aircraft was in a stall. That’s why it crashed. The user interface worked fine, but the pilots ignore it!

Personally, I think every air plane should have at least one pilot who has flown a real airplane before.

]]> By: Lassi Hippeläinen https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510144 Sat, 10 Dec 2011 15:50:31 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510144 @Kuz: actually, as an engineer I do know a bit about what I was writing about.

I have no doubt about the airline industry leaning from its own disasters, but are they learning from disasters in other industries?

Three Mile Island wasn’t an airplane, it was a nuclear power plant. Yet it should have been a lesson also for airlines. The reactor was lost in very much the same manner: all sorts of alarms were ringing, and the operators couldn’t figure out what was happening. Yet if they had noticed one small gauge they could have saved the reactor. It was the one that indicated level in the overflow tank. It was rising, because that’s where all the coolant was going. So yes, it was a user interface issue, and a very famous one for us engineers.

The lesson from TMI was to desing the alarm system so that important alarms turn off less important ones. The operators have a better chance of understanding the situation when they are not distracted by secondary events. Another improvement is to have several sensors cross-checked to filter out silly readings, and alert the operators to fix that sensor. In an ideal case, the control computer should be reading all sensors, and compare them to a set of scenarios. If someting goes wrong, it could suggest the most likely scenario for the operators.

In an Airbus you can get speed reading also from other sources. They are not as good as the pitot tubes – if the pitot tubes are working. AF447 was cruising high above the Atlantic. At those speeds you can make a good guess from available data, e.g. correct GPS reading with wind speed (from weather map) to get air speed. Or use the computer model that predicts air speed from engine thrust, load, attack angle, etc. Those models exist. They are produced in the design phase. Give that speed to the pilot, but mark it as “unreliable”.

But no, the autopilot just switched off, leaving the pilots in limbo. The airline industry seems to have learned nothing from the TMI disaster.

]]> By: Greg Laden https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510143 Sat, 10 Dec 2011 02:28:01 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510143 I was totally talking about the angle of decent. And yes, the nose was pointing up a bit.

My point was that if you are in an aircraft that is falling at that speed and going that slow you can’t possibly miss the fact if you look at the altimeter and the GPS speed estimate.

The reason the aircraft crashed is that the pilots did pretty much everything they could do to drive it into the sea, and they did that becuase they did not know how to fly an airplane, and they did not know how to fly an airplane because they were never trained because they were flying an infallible machine.

]]> By: Daniello https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510142 Fri, 09 Dec 2011 22:57:34 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510142 Greg, they did not dive the airplane into the ocean at 45 degrees. The angle of the aircraft’s path (relative to the ground) was 45 degrees, because it was stalled. The aircraft itself was pointing up, about 15 degrees give or take (just like on take-off) while it was descending at 45 degrees towards the ocean, with its nose up. Picture an aircraft taking off, in that position, except it is flying down, not where the nose is pointing.

]]> By: Daniello https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510141 Fri, 09 Dec 2011 22:52:36 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510141 In response to: “Fun fact: An Airbus will not allow the pilot to perform an “unsafe” maneuver, such as a rapid pulling up, as that over stresses the wings. A Boeing, however, will let the pliot rip the wings off the plane if they want to. Boeing assumes the pilot knows what’s best for the aircraft.”

Well, interestingly, it was an Airbus that had it’s tail snapped by an overzealous pilot handling the rudder, not a Boeing. There should not be a possibility for the pilot to snap the whole vertical stabilizer like that in an airliner.

I think Boeing is doing more things right in regards to fly-by-wire and controls (yoke vs. sidestick). Airbus should switch over to yokes which move in tandem.

]]> By: Greg Laden https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510140 Fri, 09 Dec 2011 22:52:02 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510140 By the way, when the Airbus was first built, there was concern that having a jet liner that would pretty much fly itself would lead to a pattern of training and experience that would cause these planes to crash when the plane could not actually fly itself. I think it is worth acknowledging, now that we know the facts, that this Airbus crashed, taking all on board to their deaths, for that exact reason.

]]> By: Greg Laden https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510139 Fri, 09 Dec 2011 22:49:12 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510139 David: They actually did turn on de-icing equipment and the air speed indicators were returned to normal status. Then, they flew more or less correctly for several minutes, then accidentally drove the aircraft into the ocean at a 45 degreee angle. More or less.

They were messed up by the freezing indicators, rattled by the ITCZ, then they flaked out and demonstrated that it is probably not a good idea to have a system whereby pilots are “unable to fly a plane’ that is not flying itself

After reading the transcript, I came to the conclusion that an experienced Cessna pilot who know where the controls were would have kept that plane flying.

]]> By: Ron https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510138 Fri, 09 Dec 2011 22:45:57 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510138 Fun fact: An Airbus will not allow the pilot to perform an “unsafe” maneuver, such as a rapid pulling up, as that over stresses the wings.

Seriously? Keeping the stick back and the nose up during a stall for 20 minutes is not unsafe? That is not a fun fact. That is some kind of strange denialism!

]]> By: Greg Laden https://gregladen.com/blog/2011/12/09/the-crash-of-flight-447/#comment-510137 Fri, 09 Dec 2011 22:43:35 +0000 http://scienceblogs.com/gregladen/2011/12/09/the-crash-of-flight-447/#comment-510137 Kuz, I get your point about airspeed, but the fact remains that we can now look at the GPS speed indicator retrospectively using the “black box” data and note that for a very long time the GPS speed was something like 60-90 knots. Also, the altimeter was indicating dropping altitude. How is it possible that noting that the GPS speed was slower than takeoff speed would not give a clue that the aircraft was stalling, especially when combined with the stall alarm going off for several minutes?

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