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Old 21st Mar 2019, 21:27
  #2282 (permalink)  
jagema
 
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Originally Posted by VFR Only Please
Ignorant question: What is the practical use of a "disagree light"?? I suppose it means watch your workload increase as you continually assess your pitch attitude vis-à-vis the airflow in an aircraft with a natural tendency to pitch up markedly when power is applied.

Wouldn't it be smarter to have THREE AoA indicators (same principle as three attitude indicators) and have the system stick with the two that are agreeing?
The use is to know that something is up with the*sensor*itself, and to be especially skeptical of the output from other flight computers that factor in its data (ADIRU).*
The problem with adding more indicators (3, 4, 5...?) is that sometimes 2 of them get erroneous data and 1 is left with correct and it gets voted out (AF447).
There is no perfect system.

To others saying why not add the AoA indicator, in the B737 you could actually just use the difference between the FPV and the pitch angle to figure out your AoA if you wanted to (assuming, again, the data input into these is valid).
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