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Old 2nd Aug 2007, 07:18
  #897 (permalink)  
stickyb
 
Join Date: Feb 2000
Location: asia
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Deployment of Ground Spoilers

let me ask this again:
ground spoiler deployment is totally under control of the airplane systems. No manual way for the pilot to do it manually.
Also, the logic equation behind that requires a number of parameters to become TRUE before it will allow spoilers to deploy.
Does anyone have an Idea why the system tries so hard not to deploy them?
Looking at the diagram quoted earlier, i don't agree with you. In fact the logic seems to be doing it's best to deploy the spoilers, never mind if the pilot wants them.
Just to recap - if the following conditions are met, the ground spoilers will deploy -
One of (both wheels speed > 72kt) or (RA<6ft and both MLG compressed)
plus
one of (ground spoilers armed and TL at or near idle) or (one TL in reverse and the other TL in reverse or at or near idle)
It seems to me that the first condition is designed to detect that the plane is on the ground, and the second condition is to detect that the pilot wants it to stay on the ground
As the pilot cannot do anything to influence the first condition the only thing that has to be done to achieve ground spoiler deployment is to ensure that both TLs are in idle, or reverse, or one idle and one in reverse. The logic takes that as a positive signal of intent to stay on the ground.
Of course, I cannot comment on how the logic actually detects the position of the TL or the possibility of a physical problem preventing TL movement.
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