Air France crash

[DMB]

I found this an interesting article http://www.timesonline.co.uk/tol/news/world/us_and_americas/article6446268.ece

It is now clear the crew, as they fought to stay airborne, no longer knew how fast their plane was travelling. According to Airbus and the accident investigators, the pilots’ instruments were giving “inconsistent” readings of the plane’s speed.

Did the crew or computer mistakenly think there was a danger of stalling? Did they power up, tipping the plane out of control and tearing it apart in the turbulence? Or did a violent updraft simply drive them too close to coffin corner?

I think anyone who has worked with computers will have misgivings about a system that relies so heavily on them, however much reduntancy is built in.

At the end of this report (http://edition.cnn.com/2009/WORLD/americas/06/08/brazil.plane.crash/index.html), I thought this was significant:

Investigators also reported the airline failed to replace a part on the aircraft, as recommended by the manufacturer, Airbus.

Airbus had advised airlines to update equipment that monitors speed, known as Pitot tubes. The recommendation was a result of technological developments and improvements, an Airbus spokesman told CNN. The change was not mandatory, and the spokesman would not comment on Air France's failure to follow the advice.

[Ray Moscow]

Yeah, apparently other Airbus planes have had similar problems with the airspeed indictators. We might never know if this caused this crash.

It's also possible that they got caught in the storm, maybe some unusually bad weather effect that caught them off guard.

[Worldtraveller]

Working in the aircraft industry and being familiar with the safety regulations, I have to admit to always being a bit nervous when I fly an Airbus. The A-320 was the first (I'm pretty sure) commercial airline to use fly by wire control. That means that ultimately, a computer is in control of what the plane does by interpreting the pilot's commands through the traditional flight controls.

No cables or direct links anywhere.

One crash was caused early by a software glitch. During an airshow, the pilot made a low pass, and when attempting to apply power and go around, the computer 'refused' and insisted on trying to land the plane. The result was the plane going into the trees and killing the three crewmembers. Another near miss occurred a couple years later, this one full of passengers, the crew managed to recover that one, though.

Since the instrumentation and sensors (like the pitot tube and dynamic ports) are the basis of what the computer uses to decide what to do, a bad sensor could quite easily cause an accident.

A similar event happened in Peru years ago, when a ground crew forgot to take the tape off the dynamic ports, and the crew couldn't tell their altitude or how fast they were going, and wound up flying into the ocean at night. :(

[Alex]

I've always assumed that manual override is available for the pilot to take control if the fly by wire technology gets a plane into difficulty. The idea that a faulty bit of software - perhaps in very unusual circumstances - can make the plane stop flying or "insist on trying to land" it in the middle of the ocean, adds a new terror to air travel.

[DMB]

If you read the whole article I linked to in the OP, you will see how horribly difficult these things are to fly manually.

Whoever was in the pilot’s seat was looking at two computer screens, a host of other instruments and two rudder pedals – but no traditional hand controls. Instead, an A330 pilot reaches for a small joy-stick to one side. It looks a bit like the control for a games console. Through that “sidestick”, the pilot flies the plane with electronic signals, rather than any mechanical linkages.

"It’s tricky. At altitude big planes wallow about,” said Roger Guiver, a former British Airways pilot. “It’s like trying to steer the QE2 with a 2ft rudder.”

[Alex]

For the sake of extreme manoeuvrability, I understand some military aircraft are intentionally designed with an aerodynamically unstable configuration and wouldn't be flyable without automation. Perhaps passenger planes like the Airbus now depend on flight control computers to a point where they're also nearly unflyable without them?

[Worldtraveller]

For the sake of extreme manoeuvrability, I understand some military aircraft are intentionally designed with an aerodynamically unstable configuration and wouldn't be flyable without automation. Perhaps passenger planes like the Airbus now depend on flight control computers to a point where they're also nearly unflyable without them?
No. At least not for aerodynamic maneuverability reasons. You'll notice almost all commercial and general aviation (GA) aircraft are built with a slight dihedral to their wings (they form a V if you look at them head on). This makes them naturally stable, and with the controls in the neutral position, they will tend to return to a wings level configuration.

Frankly, I'm not sure why Airbus has designed fly-by-wire systems into their commercial aircraft. I don't think it has improved reliability, maintainability, or reduced cost over traditional cable pully type systems that all other commercial aircraft use.

[Valheru]

I can imagine a whole host of reasons, and I'm no expert.

I can imagine reduced weight, increased autonomy from the flight systems, reduced maintenance, and improved reliability via electronic integration, thus smaller component size, and thus greater ability to install redundancy.

Isn't it true that traditional commercial aircraft don't use pulleys and whatnot anyway, and that the control surfaces are hydraulically controlled, the stick and rudder controls being physically removed from the surface actuators in any case?

[Worldtraveller]

I can imagine a whole host of reasons, and I'm no expert.

I can imagine reduced weight, increased autonomy from the flight systems, reduced maintenance, and improved reliability via electronic integration, thus smaller component size, and thus greater ability to install redundancy.

Isn't it true that traditional commercial aircraft don't use pulleys and whatnot anyway, and that the control surfaces are hydraulically controlled, the stick and rudder controls being physically removed from the surface actuators in any case?

Some large aircraft do, most of the use a combination of actual pulleys wuth hydraulic assist. Remember, most of the large commercial aircraft were designed in the 70s. :p

[DMB]

http://edition.cnn.com/2009/WORLD/americas/06/09/brazil.plane.crash/index.html

Air France has agreed to replace within days sensors on all of its Airbus A330 and A340 airplanes, parts that are suspected of being involved in last week's crash, a pilots' union said Tuesday.

Let's not hurry to do stuff, chaps. Wait at least until it causes a crash. Another reason not to fly Air France (I have avoided them for years)?

[Ray Moscow]

http://edition.cnn.com/2009/WORLD/americas/06/09/brazil.plane.crash/index.html

Air France has agreed to replace within days sensors on all of its Airbus A330 and A340 airplanes, parts that are suspected of being involved in last week's crash, a pilots' union said Tuesday.

Let's not hurry to do stuff, chaps. Wait at least until it causes a crash. Another reason not to fly Air France (I have avoided them for years)?

Remember Fight Club (film or book), in which the narrator/main character's job was gathering data on fatal car crashes?

His employer, a car company, only issued recalls when the estimated costs of settlements exceeded the recall costs -- which meant a lot of people had to die before recalls were implemented.

It's just fiction, right? :)

[Rilx]

Do you remember an old story, about a plane flight. All of the passengers were securely in their seats and the plane was racing down the runway when a voice came over the loudspeaker, that said: Ladies and Gentlemen, welcome to our flight 407. This is a recording speaking to you. We are now taking off and, in just a few seconds, we'll be in the air. The entire flight is being done by automation. There are no human pilots in this plane. Just relax, this is the most secure vehicle ever built. Nothing can go wrong... wrong... wrong... wrong...

[DMB]

Another article. An attempt to pull things together, but doesn't add all that much. http://edition.cnn.com/2009/WORLD/americas/06/11/air.france.crash.daly/index.html

[Puck]

It would be nice to get the 'black box'. Without that, we'll never know for sure what happened.