Air France 447

[Onkel Neal]

http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877


The Airbus's stall alarm is designed to be impossible to ignore. Yet for the duration of the flight, none of the pilots will mention it, or acknowledge the possibility that the plane has indeed stalled--even though the word "Stall!" will blare through the cockpit 75 times. Throughout, Bonin will keep pulling back on the stick, the exact opposite of what he must do to recover from the stall.




I guess the world is still trying to understand how the co-pilot could have reacted so badly... and why the Robert, with much more experience, was allowing Bonin to fly the craft during the stall?

[Herr-Berbunch]

There was a thread about this a couple of months ago, looks like nothing has changed on the blame front. Incredulous that it could've happened in this day and age! :nope:

[TheDarkWraith]

Commercial airliners have what is called a 'shaker' on the yoke. When the aircraft is nearing a stall the yoke will vibrate/shake warning the pilots of an impending stall. If the pilot's don't take action and the computer deams that a stall is imminent it usually pushes the yoke forward to prevent the stall. It's very hard to stall a commercial airliner these days.

[Herr-Berbunch]

I think that was one of the points, poor design and implementation of the fly-by-wire side-sticks, no feedback and not necessarily visible to other crew the sticks position. Hence one pulling back all the time and the others not reacting to that!

[Catfish]

For what i read and heard from an airbus captain, the joysticks on both sides of the cockpit are not interlocked in a way they mirror the other's position - one does not repeat the position of the other one.
I still wonder why someone would install this "solution" in an airliner, but ..

So one stick untouched being laid back at pull position, the other will probably not react to any input.
While pilots are trained though and know this, this seems to be one of the explanations how this situation was possible to happen.

[Falkirion]

Commercial airliners have what is called a 'shaker' on the yoke. When the aircraft is nearing a stall the yoke will vibrate/shake warning the pilots of an impending stall. If the pilot's don't take action and the computer deams that a stall is imminent it usually pushes the yoke forward to prevent the stall. It's very hard to stall a commercial airliner these days.
I know Boeing has the stick shaker installed, but does Airbus have it installed in the cockpit side stick as well?

[Stealhead]

I am not 100% sure that every aircraft over a certain size is required to have a "shaker" on both yokes there are also "stick pushers" that warn the pilot of a dive.Of course a crash can also be caused by an incompetent crew very easily.All large modern airliners pretty much are designed to keep the person controlling them from doing something that will cause the plane to enter an uncontrollable state but that has a limit.

NatGeo has a shown called seconds from disaster many are about plane crashes one episode about an Aeroflot Airbus crash the pilot let his kids sit in the seat and they turned off autopilot control to the ailerons and the plane of course went off course and the pilots failed to notice that the auto pilot had all but the ailerons under it control in the end they crashed the plane.

http://www.youtube.com/watch?v=xz0So--Xebo

[Falkirion]

Ah here's the info I was after. It's covered in a post in this forum discussion on Airliners.net
http://www.airliners.net/aviation-forums/tech_ops/read.main/81259
Looks like Airbus doens't provide stick shakers and instead relies on their FBW computer laws to keep the plane in a controlable state.

[Stealhead]

That is still fairly reliable and has redundancy in it just a different system.Sometimes things just go wrong though more than one redundant system can fail and even if the crew does everything correctly sometimes a crash is just unavoidable.

Two old military aviation sayings:
A fighter with two engines(jet) is better than a fighter with one engine(jet) with two engines if one fails the other one will stay running long enough for you to fly into the ground.

Always remember that there are more planes on the bottom of the sea than there are submarines in the sky.(Naval Aviation joke)

[Jimbuna]

Having read the transcript it looks like a catalogue of errors and obviously fatal consequences.

Always take the seat next to the black box when flying.

[Spoon 11th]

How about packing hand held GPS receiver (like cell phone) next time to have reliable indication of ground speed when pitots fail.

[Tchocky]

How about packing hand held GPS receiver (like cell phone) next time to have reliable indication of ground speed when pitots fail.

Not a bad idea, and I see what you're getting at. Unfortunately groundspeed isn't a very valuable metric once you get into serious head/tailwinds.
Given the narrow interval between stall speed and Mach buffet speed at cruising levels there isn't much groundspeed can tell you, and adding a wind component to the calculation requires (dammit!) pitot tubes.

[Stealhead]

Those GPS deals do not give an accurate speed reading.The Garmin that I have is off by about 5 MPH my speedo will say 60MPH the Garmin will say I am only going 55MPH and it seems that the higher my speed gets the more inaccurate the Garmin becomes.

When you are talking about a flying object(reguardless of the state of control it under) there are numerous speeds to consider.

[Schroeder]

@Stealhead.

Your Garmin is accurate, it's your speedometer that is off.:yep:
Speedometers in cars are build to indicate a bit more than you actually go. That is so to keep you from speeding. You think you go 10mph faster than the speed limit while in fact you are just 5-6 mph too fast and the cops won't stop you for that.
Mine indicates 4-6 km/h more than I actually go. Saved a lot of people a lot of money.:D

[Stealhead]

Well my speedo in my newer vehicle must be fairly close then because I have been ticketed 3 times and each time I was 100% aware of my speed and I do not give the law any information as to my exact speed but they will tell you and they have each time hit my speed on the head as to what the speedo was claiming.Maybe some cops a very good a math I recon.I have a old 240Z and that things speedo is off by almost 20MPH I know that because if I where actually going the speed it points at down my dirt road my head would smashing into the ceiling.

According to what I read your speedo can be 10% fast in the US but not any percentage off below actual speed.I also read that GPS in theroy is only off by 1% however that measurement is not constant it is over a length of time(very short but still it will miss changes) so it is not always 100% accurate either.If you have the cruise set and are on a level road then the GPS is more accurate.If you in conditions with a lot of speed variation then your speedo is more reliable.

Of course once I got pulled over in a 91 Honda Civic I had it nearly pegged which is 105MPH and I got pulled over and the cop said that I was going 77 MPH and I said "Sir you are correct I was going about 77MPH" he only gave me a warning this was in a 55 zone.Even if the speedo was 10% fast in that case I was still going about 95 MPH.I think he was just impressed that I had the pelotas to go that fast.

I would lean with a newer vehicle with the factory desgin tire and wheel size your speedo is likely not 10% fast but closer to 4 or 5 % fast.

Another thing to consider the GPS uses very accurate math (but the measurements can be incorrect because of spotty signal) most GPS have a fastest speed traveled a freind of mine looked at his once (this was the built into the dash kind) on his Prius and it said 180MPH yeah not possible I also read on a GPS forum once a page that listed top speeds traveled and one guy posted a picture of his 500mph.So the best bet is to use both your speedo and your GPS to be sure.

[Spoon 11th]

Not a bad idea, and I see what you're getting at. Unfortunately groundspeed isn't a very valuable metric once you get into serious head/tailwinds.
Given the narrow interval between stall speed and Mach buffet speed at cruising levels there isn't much groundspeed can tell you, and adding a wind component to the calculation requires (dammit!) pitot tubes.
They descended from cruise altitude pretty fast. At 10,000 feet you can safely fly at atleast 250 knots. Set ground speed to 200 knots using GPS and you have 50 knots margin for wind component (150 to 250 knots air speed depending on wind direction). Then call for assistance and military jet or something will wingman you to the touchdown.

[Stealhead]

The air gets thinner as your altitude increases meaning that your margin between stalling and controlled flight goes down as you go higher.The old U-2 and the modern TR-1s the space between stall speed and maximum speed at operating altitude 70,000 ft is a mere 10 knots and often times they fly at a mere 5 knots above stalling during a mission.

Also what speed is safe to fly at and at what altitude varies with each design and the conditions so the speed that a GPS alone might recorded is not really that relevant.An air crew is concerned with IAS and TAS not GS very much.

[Sailor Steve]

The old U-2 and the modern TR-1s the space between stall speed and maximum speed at operating altitude 70,000 ft is a mere 10 knots and often times they fly at a mere 5 knots above stalling during a mission.
As I understand it the U-2 had very stable stalling characteristics for just that reason. In a stall it would pretty much automatically pitch over into the proper position and descend properly until speed was built up again. Easy to build into a long, narrow plane with a huge wingspan; not so easy in a huge, heavy airliner.

[Stealhead]

Well that directly contradicts what a Corneal told me once in the Air Force he had flown the later TR-1s for a portion of his career before getting the old desk and he told myself and some others in a conversation about flying aircraft that the TR-1 would more or less drop like a rock at high altitude if you allowed it to stall and given the fact the the span of speed for the TR-1 and U-2 between stall speed and maximum is only about 10 knots that makes it an aircraft that requires great skill to fly at mission altitudes if you happened to be in ahead wind you might only manage to get the plane 2 or 3 knots above stall that is dangerously close.

What you say is true for the U-2 at lower altitudes I have no doubt but at 70,000ft it is not an easy aircraft to fly.

Now an airliner would simply not even be able to fly at 70,000 ft in the first place.

There was and is a reason that the TR-1 is one of the most difficult planes for an Air Force pilot to get into the cockpit off same goes for any Air Force members involved with the TR-1.

Here is an article about flying a mission in a U-2 written by a Lt. Corneal as you can see it was not an easy task at all.

http://www.blackbirds.net/u2/u-2mission.html

Very nice video of James May going for a ride in a TR-1 at 5:18 they see an airliner that is about 30,000ft below them.Looks like a nice place from that point of view doesn't it?

http://www.youtube.com/watch?v=1PmYItnlY5M

[magic452]

When I worked at Lockheed in the 60's I was talking to one of the U-2 pilots and he was saying that at altitude it was possible to have one wing tip in stall buffet and the other in Mach buffet. Pretty tight spot, can't speed up, can't slow down. :o

Magic