PPRuNe Forums - View Single Post - AF 447 Thread No. 7
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Old 10th Mar 2012, 07:48
  #793 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 72
Posts: 2,429
Machinbird;

Re, "As soon as the system cannot figure out which one of the speeds, if any, is "telling the truth." "

It doesn't need to. A power setting and pitch attitude is all you need and as someone suggested here, a recent history if the automation is to do it, (but no thanks!). Speed indication is now irrelevant. An AoA would help but it isn't necessary.

As discussed by Owain Glyndwr and to HN39's point regarding autoflight system programming when the AP and AT drops offline, the A330 fails/failed 'gracefully'. When disconnected by the airplane and by the instinctive disconnect buttons on the thrust levers, the autothrust reverts to the thrust-lock mode, maintaining the power setting at disconnect.

Almost all the time the thrust is appropriate. Here, the thrust had dropped slightly but to no short-term effect.

The checklist requires that the autothrust be disconnected, (press the AT button on the FCU or the instinctive buttons and THR LK is removed), then move the thrust levers out of the CLB detent and set thrust according to the tables. About 88% N1 or 1.2 EPR would be a good start, if I recall.

In Alternate Law pitch must be manually controlled so there is perhaps room for some form of "maintaining pitch" but I think this is taking automation precisely where we don't want to take it..."more", to cater to reduced thinking and skill levels.

The airplane is eminently flyable at cruise altitudes even in heavy turbulence, (done it...it's like any other airplane including the DC8)...tiny movements on the stick, (or control column), wait..., set the thrust, wait..., read the checklist, wait for the airspeed to return, as it did within 30 seconds in all previous events. And if it doesn't then complete the checklists, ECAMs, STATUS pages and secure the aircraft for manual flight, call the captain and decide whether to return to RIO (or..?) or continue.

RR_NDB, this response isn't "the academice ideal", this is what crews are trained to do and is absolutely middle-of-the-road SOPs. That it isn't done sometimes is not a counter-example argument for a sense that this is "expecting a lot", nor is it an argument for further-reduced standards and more automation.

In climb/descent and except for close in approach (when dirty), one levels off, and does the same thing. The powerpoint presentation to which Turbine D provided us the link is a superb explanation of the "new" (2006) process. The powerpoint referenced by Turbine D is at http://www.iag-inc.com/premium/Airbu...ableSpeeds.pdf

BTW, I quite appreciate that typing this stuff out is SO much easier. Like others here I'm sure, I've had a few "events" and they are never straightforward and the adrenaline always comes.

Last edited by PJ2; 10th Mar 2012 at 08:01.
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