>Straw man alert! IF the current allegations wrt the 737 are true, they
>focus on the hydraulic actuators, not the cabling from the cockpit. The
>A320 uses pretty much the same kind of hydraulic pumps, the same plumbing,
>the same actuators, as any other airplane out there. It is the signalling
>mechanism that differs. Rather than have a set of steel cables from the
>control devices, wired through the airplane, and ending up at the control
>surfaces, the A320 design uses joysticks to signal a computer, which sends
>an electrical signal through much lighter wiring, through the same path,
>to the hydraulic actuators.
Oops, should have phrased this better (or check-read what I said more
carefully). I was trying to emphasise the fact that the hardware technology
for implementing FBW (electronic signalling via computer) is not usually
the problem, and people shouldn't forget that hydromechanical components
are also susceptible to failure. Concorde (FBW aircraft) has had flight
control failures too - delamination and separation of sections of the
rudder. Again, electronics not at fault.
[As an aside, I wonder if there are accidents where uncommanded control
input due to distortion of the fuselage (from otherwise non-fatal
structural failure for example) pulling cables has been a factor in the
loss of the aircraft, and whether an FBW aircraft with multiple independent
signal paths, would be less susceptible.]
>This aside, the problem with the A320 is not the FBW design. It's the
>human factors in the cockpit and the design decisions that accompanied
>the FBW implementation: non-coupled sidesticks, throttle design, and
>the huge number of MODALITIES which accompany this implementation.
The lack of tactile feedback is unique to Airbus FBW aircraft. The
information is available from other sources, but pilots don't always use
these for some reason and so removing a cue is a cause for concern for
some. Airbus might argue that these can be addressed through training.
Non-coupled sidesticks has resulted in incidents in the past. Non-moving
thrust levers have not been directly implicated in any incident I know of
(although moving thrust levers could have provided a vital cue at the Mt.
Saint-Odile crash).
The modalities are a feature of any automated cockpit, irrespective of
manufacturer. The 777 has a number of different control laws as well.
(BTW, Robert, has part of this branch ended up on the wrong list? It
started to go to the FMC list but should be on CRM? ATA watchers?)
Thanks for putting that straight,
mark.