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Shouldn't there always be a manual flying mechanism failsafe in the case of electrical failure? Fly-By-Wire doesn't seem very safe to me... in the same way I ha

Shouldn't there always be a manual flying mechanism failsafe in the case of electrical failure? Fly-By-Wire doesn't seem very safe to me... in the same way I have doubts about Drive-By-Wire.

lmm 13y ago
Mechanical systems fail too. Cables can snap, gears can shear off, pedals can bend. As long as you require an appropriate level of redundancy, there's no reason an all-electronic plane should be any less safe.
- Zancarius 13y ago
  As an illustration and to provide some sample evidence for lmm's comment (there's plenty more): http://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981 http://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981 http://en.wikipedia.org/wiki/American_Airlines_Flight_96 http://en.wikipedia.org/wiki/American_Airlines_Flight_96 In both of these cases, rapid decompression from a failure of the cargo door caused parts of the floor to collapse and sever or restrict the mechanical cables leading to the aft control surfaces of the plane. Although the American Airlines pilots were able to land the plane safely (they still had some control), the Turkish Airlines pilots were not so lucky. Furthermore, even mechanical systems are assisted by hydraulics. Hydraulic systems can fail, usually through draining, leaving the flight uncontrollable. So to add to the comments by both lmm and leoedin, safety has no bearing on whether the aircraft is mechanically controlled or electronically. There are also deployable ram air turbines[1] that can provide a small amount of emergency backup power in the event of a total failure of all engines: [1] http://en.wikipedia.org/wiki/Ram_air_turbine http://en.wikipedia.org/wiki/Ram_air_turbine
testrun 13y ago
Fly-by-wire is pretty established by now. The system is also made redundant for safety.
- jessaustin 13y ago
  It can even be safer than mechanical, if the savings on parts and maintenance allows a better class of component or more redundancy.
virtuz 13y ago
Fly by wires have three redundancy systems built in (afaik), so four systems have to fail for loss of control. It might be as unlikely to lose data from S3 with their nine 9s of durability as it is to crash from a failure in fly by wire. Also, as @lmm says mechanical systems break too. And when they break, objects fly from the plane – sometimes into the fuselage, sometimes into the engine. I remember reading something about it and I think this caused a crash in a flight before, but I can't find the source right now.
leoedin 13y ago
The A320 (introduced in 1988) uses only fly-by-wire. There's been almost 6000 of them built since. The Boeing 777, 787, Airbus A330, A340, A380 and forthcoming A350 are all fly by wire. It's a proven technology which has millions of flight hours behind it. To fly something the size of a modern airliner, you need assistance. Even if they all used traditional control systems you'd still need functioning hydraulics to control the aircraft. That's why we build lots of levels of redundancy into the system. Rather than making something which can gracefully degrade to manual control, we make something which is so failure resistant that it never loses power. virtuz: It seems your account is dead. Not sure why - your comment history doesn't make it obvious. Maybe worth asking HN admins about?

Shouldn't there always be a manual flying mechanism failsafe in the case of electrical failure? Fly-By-Wire doesn't seem very safe to me... in the same way I have doubts about Drive-By-Wire.

lmm 13y ago

Mechanical systems fail too. Cables can snap, gears can shear off, pedals can bend. As long as you require an appropriate level of redundancy, there's no reason an all-electronic plane should be any less safe.

Zancarius 13y ago
As an illustration and to provide some sample evidence for lmm's comment (there's plenty more): http://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981 http://en.wikipedia.org/wiki/Turkish_Airlines_Flight_981 http://en.wikipedia.org/wiki/American_Airlines_Flight_96 http://en.wikipedia.org/wiki/American_Airlines_Flight_96 In both of these cases, rapid decompression from a failure of the cargo door caused parts of the floor to collapse and sever or restrict the mechanical cables leading to the aft control surfaces of the plane. Although the American Airlines pilots were able to land the plane safely (they still had some control), the Turkish Airlines pilots were not so lucky. Furthermore, even mechanical systems are assisted by hydraulics. Hydraulic systems can fail, usually through draining, leaving the flight uncontrollable. So to add to the comments by both lmm and leoedin, safety has no bearing on whether the aircraft is mechanically controlled or electronically. There are also deployable ram air turbines[1] that can provide a small amount of emergency backup power in the event of a total failure of all engines: [1] http://en.wikipedia.org/wiki/Ram_air_turbine http://en.wikipedia.org/wiki/Ram_air_turbine

testrun 13y ago

Fly-by-wire is pretty established by now. The system is also made redundant for safety.

jessaustin 13y ago
It can even be safer than mechanical, if the savings on parts and maintenance allows a better class of component or more redundancy.

virtuz 13y ago

Fly by wires have three redundancy systems built in (afaik), so four systems have to fail for loss of control. It might be as unlikely to lose data from S3 with their nine 9s of durability as it is to crash from a failure in fly by wire. Also, as @lmm says mechanical systems break too. And when they break, objects fly from the plane – sometimes into the fuselage, sometimes into the engine. I remember reading something about it and I think this caused a crash in a flight before, but I can't find the source right now.

leoedin 13y ago

The A320 (introduced in 1988) uses only fly-by-wire. There's been almost 6000 of them built since. The Boeing 777, 787, Airbus A330, A340, A380 and forthcoming A350 are all fly by wire. It's a proven technology which has millions of flight hours behind it. To fly something the size of a modern airliner, you need assistance. Even if they all used traditional control systems you'd still need functioning hydraulics to control the aircraft. That's why we build lots of levels of redundancy into the system. Rather than making something which can gracefully degrade to manual control, we make something which is so failure resistant that it never loses power. virtuz: It seems your account is dead. Not sure why - your comment history doesn't make it obvious. Maybe worth asking HN admins about?