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Old 24th Jun 2010, 18:58
  #1600 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 76
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There is a significant mis-understanding occurring here regarding the UAS QRH drill.

Someone here has already hinted at the problem - the UAS drill caters to failure of airspeed information at low altitudes, (as a result of the Birgenair and Aeroperu B757 accidents). The inital pitch attitude of 5deg, under the configuration anticipated, is reasonable.

The memorized portion of the UAS QRH drill does NOT require a "5deg" pitch attitude above MSA or circuit altitude. The last memorized item at the bottom of the drill states:

"When at, or above MSA or Circuit Altitude: Level off for troubleshooting."

The read-and-do section of the QRH drill then states:

– GPS ALTITUDE ............................................................ .........Display on MCDU

To level off for troubleshooting:
–AP/FD ............................................................ ......................OFF
–A/THR ............................................................ ......................OFF

Then the drill requires an assessment of configuration for which it provides pitch and power settings:




NOTE that between FL 200 and FL360, the Speed is 260kts and the required Pitch and Power are stated as "3.5deg/71.9%N1".

Assuming appropriate training and airmanship, I cannot imagine that an experienced crew would, at FL350, slavishly pitch the aircraft up to 5deg upon loss of airspeed information. They would, I expect, instinctively know what would happen if they did this, and changed what was working well, (in terms of pitch and power) moments before the loss of airspeed information.

Although Bloomberg/Businessweek reported it, the original story leaves out important details regarding this drill and speculates without either understanding the drill and the airplane or knowing all the facts, which remain locked in the DFDR and CVR.

PJ2

Last edited by PJ2; 24th Jun 2010 at 19:11.
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