> So, not much information why the computers sent conflicting commands and also why the engines power down in such a situation.

I think shutting down the engines is probably the safest option when this sort of thing happens. You could argue they should stay in the present setting, but what would happen if one engine were at 0% and another 100%?

Most aircraft are pretty good at gliding even without power, and I'd assume a deadstick landing is part of the pilots training. In 2001, TS236 flew unpowered for 19 minutes before making an emergency landing (on a runway) with only minor injuries:

http://en.wikipedia.org/wiki/Air_Transat_Flight_236

> I think shutting down the engines is probably the safest option when this sort of thing happens. You could argue they should stay in the present setting, but...

Shutting down an engine should always be a decision made by the pilot not a machine IMO. A pilot might prefer to blow out an engine if that gives him enough ( even a couple of seconds matter in this situation ) time to reach a save landing spot or avoid an obstacle.

> what would happen if one engine were at 0% and another 100%?

Pilots are train in this situation all the time and is part of the syllabus for a multi-engine rating. Basically the plane would try to turn to the side that the engine failed. Pilot will use opposite ruder and aileron to compensate while cutting back power in the good engine to just enough you can keep altitude if possible.

> Most aircraft are pretty good at gliding even without power, and I'd assume a deadstick landing is part of the pilots training.

So happen here too. The crew tried tried a dead-stick landing in a field when they realized the could not make the airport. Unfortunately the hit a High Power pole and the plane catch fire.

One of the crew members lost in the accident was a friend of my father. My condolence to the families of those who lost their live that day.

"but what would happen if one engine were at 0% and another 100%"

Part of earning your multi-engine cert is memorizing all manner of different airspeed limits for that kind of situation. If you want to maintain yaw control with one engine feathered (er, shutdown) and the other at full throttle you must be going faster than X knots or whatever. Below that indicated airspeed you pull back on the throttle or you're going into a turn at best or more likely a spin.

In fact, there is a light blue radial line painted (or displayed) on the airspeed indicator for exactly this situation, so the crew doesn't have to remember the value in a high-stress situation.

>what would happen if one engine were at 0% and another 100%

Planes are designed to fly fine in that situation - it's what you get if one engine breaks down. Now landing the thing with one engine stuck on 100% would be interesting. I guess you could kill the engine somehow - turn off the fuel or pull the fuses.

An engine stuck on has happened before, though I believe this was only flight idle:

https://en.wikipedia.org/wiki/Qantas_Flight_32

Mind you, that was the result of an uncontained engine failure.

Planes with four engines are certainly not designed to fly with 3 of 4 engines out...

Indeed, planes are not designed to be flown in that configuration normally, but they are certainly capable of single-engine flight in emergency situations (where the alternative would be "flying like a ton of bricks"). Exhibit A: http://en.wikipedia.org/wiki/British_Airways_Flight_9

No, actually "capable of flying" means capable of performing all flight maneuvers required for safe flight and landing, including takeoff, go-around and approach/landing. BA Flight 9 failed all four engines, normally not survivable - but managed to restart all four engines by windmilling. So they recovered in time for landing.

Just curious, where did you find that definition of "capable of flying"? Because under that definition a glider ( unless it is a motorize glider ) is not "capable of flying".

Okay, under that definition, you are correct. Note that the flight later lost engine #2 again (incidentally making the record of five engine failures on a single flight), so it landed with 3 engines operational.

Pretty good at gliding from a high flight level. If you are hitting power poles, you are way too low for gliding an usually-powered aircraft. TS236 and Gimli Glider were exceptionally lucky, IMNSHO.