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Old 21st Mar 2015, 03:14
  #34 (permalink)  
cosmo kramer
 
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Regards your concerns about low speed stall - why can't it be high speed stall if you're in turbulence with strong vertical windshear??
Do you mean an accelerated stall or high speed buffet?

Accelerated stall (occurring at a higher speed than a 1G stall) is exactly what I mean. If you are deep in the low speed band, you are awfully close to the 1G stall speed. A few bumps of turbulence and the wing is stalled.

I have never heard of high speed buffet (supersonic shockwaves) causing disruption of the airflow to an extent that is causes the wing to stall in the case of 737. I doubt that turbulence would contribute further to the disruption of the airflow caused by the shockwaves as I would believe they are purely a function of the speed. Someone can correct me if I am wrong.

Anyway, Boeing did dive tests with full thrust as part of the certification!! The drag rises so much that it is not possible to accelerate the aircraft to such speeds in normal attitudes.


Exceeding MMO/VMO is no big deal, there is a huge margin. So, I would still go for the safe numbers:

12-15 deg pitch on takeoff

Descent all altitudes:
-1 deg / idle

Climb, at climb thrust:
Sealevel: 10
FL100: 8
FL200: 6
FL300: 4
FL400: 2

6 deg / 65% for level flight below FL100
2 deg / 85% for level flight at cruising altitude.

The short version (easy to remember): 12-15, 10, 8, 6, 4, 2, -1 - and the thrust settings 65/85 to go with 6 and 2.

In my opinion Boeing are dumbing things down, because they know the eroding manual flying skills causes people not to know these values anymore.

AF447 has been mentioned as an example. My point: Had they maintained a normal cruise pitch and thrust, nothing would have happened! From the CVR it appears that they never recognised the airspeed disagree, hence they would never have set pitch and thrust to a predetermined value, even if Airbus had had procedures comparable to the new ones of Boeing.

So for those who can still fly, "use attitude and thrust to maintain control". For those that can't, they will probably be so startled that it won't matter what procedures they use. Sad state of affairs.
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