Originally Posted by Will Fraser
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This with an automatic penalty in controllability, to wit, cancel roll, no protex, stab trim only, and 8 degrees of Rudder travel, still enough if cycled to rip off the VS. ????
Glad to see PJ2, ELAC and others still taking the time to write long and knowledgeable replies and explanations. Let me add perhaps a few comments, though not quite as eloquently.
Will Fraser, would you please, like so many others, get your facts straight before asking such questions.
Again, what is Alternate Law (Protections lost)?
It is a load-factor demand control in pitch, and roll is controlled as in any conventional aircraft, direct stick-to-surface deflection.
Where does the idea come from that in this control law aileron control was lost, and only manual stabiliser trim and rudder was available? What you are talking about is the last reversion step, still far removed from Alternate Law. It is only in effect in case of loss of all Flight Control Computers.
The rudder travel limiter is independent of Normal or Alternate Law, although it is obviously not independnt of reliable airspeed information. So that Alternate Law and RTL fault co-incide is not surprising here, but Alternate Law does not automatically disable the RTL.
There is seemingly even more confusion about what the computers do, can do, don't and cannot do, both in Airbus and in Boeings.
What people talk about regarding "the computer flies the aircraft" is true for most of the time in most flights in all airliners. The computer doing this is called an Autopilot. Boeing and Airbus are no different.
What the fly-by-wire system does is steer the aircraft precisely and deterministically in the way the pilot commands it to. It rolls at a commanded rate and gives a commanded g-load factor. These are some very basic feedback-control loops, nothing could be farther from "Artificial Intelligence". In no situation is there anything remotely resembling a computer "trying to outsmart the pilot". Whether or not over-reliance on automation leads to an erosion of basic flying skills is another matter, but looking at recent accidents with Airbuses, Boeings and Bombardiers I think that problem is not specific to Airbus crews.
The most prominent exclamation cited to show how confusing computerised aircraft are is the "What's it doing now?" Again, this may be true, but it always relates to mode confusion, which is a problem with modern, highly complex autoflight systems ("Autopilot/Autothrust"). It is common to Airbus, Boeing, Embraer, Bombardier, and has absolutely nothing to do with the fly-by-wire system.
DC-ATE,
During Flight-Law-degradation in Airbus, the pilot does not have to figure out what is going on, and does not need to remember how to control it entirely differently in Normal, Alternate (red. prot), Alternate (no prot) or Direct Law. It's always the same: push the stick: nose goes down, pull the stick: nose comes up, push it left: plane banks left, push it right: plane banks right. It is an airplane, and it is flown like an airplane. The difference is the level of protection (which in this form, non-FBW aircraft don't have in the first place), and the amount of "smoothing" the computers do to achieve the desired trajectory.
Even if it crops up again and again in this thread, there is absolutely no indication that flight control had reverted to manual reversion, i. e. rudder, pitch trim and thrust only.
Originally Posted by WhyIsThereAir
but the software will not let the plane be flown until the warnings are cleared.
Where does this come from? Are you seriously implying that, like a modal dialog in Windows Software, all operation of the flight controls is blocked or suspended until all ECAM procedures have been finished?
The aircraft can always be flown and will always be flown if that is necessary before any troubleshooting and other procedures can begin.
Again, that this is not always the case is well-known, but by no means an Airbus-only problem. An Adam Air B737 was lost not too long ago, because both pilots were troubleshooting the ADIRUs, and no-one was flying the airplane. It broke up in mid-air when recovery was finally attempted after the bank angle had reached 100 degrees, because in trying to arrest the steep dive the ultimate load limit was exceeded. Even in Alternate Law, Airbus would have prevented excessive load; if I remember correctly, the Adam Air flight reached some 3.7G before it disintegrated.
It is interesting to note that this flight broke up because it had no load limiting protection, and in the A320 accident at Perpignan the crwe might have wanted a bit more than the limited 2.5G. Whether or not 3G would have been enough to stop the descend before the water surface I cannot say.
As to flying "Pitch & Power": As has been mentioned before, the memory items are: disocnnect A/P and A/THR, set CL thrust (will be set as soon as A/THR is disconnected in the "normal" way), and 5 degrees pitch up (depending on altitude and flight phase).
There are then longish tables to be consulted which exact N1 value and pitch angle is to be set at which altitude. This may indeed be nigh impossible in severe turbulence at night.
ClippedCub,
Sometimes an engine that is on fire is still producing thrust that may be needed. It is the pilot's decision (on an airliner usually not engaged in a dogfight ...) when to shut it down. It should not be left to the computer. And on an airliner flight deck there are two pilots, unlike most modern fighters.
Bernd