PPRuNe Forums - View Single Post - A320 OEB Blocked AOA probes
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Old 6th Jan 2015, 05:07
  #23 (permalink)  
vilas
 
Join Date: Jun 2007
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FLEXPWR, Willie Nelson
I will examine the situation again. When AoA sensors are stuck(for whatever reason) at low speed(higher AoA) position and the speed increases, when the alpha prot threshold is lowered the protection gest triggered. Will it go in dive and exceed limits? Not possible because alpha prot is a latching condition and will maintain that angle of attack which also is stuck at lower speed(higher AoA)value. The problem is not dive but involuntary/unwanted descent at alpha prot which cannot be reversed and can be critical close to ground. So by switching to alternate law you override the protection. On the PFD the actual speed will be correct but the display of Valph prot and V alpha strip will be erroneous since it is coming from AoA sensors in the wrong position. It is not possible to investigate which AoA sensor is faulty and you will have to fly in alternate law.The cockpit indication for unreliable air speed can confusing and there are many scenarios but not the one discussed above. However once diagnosed you will reject all of them fly by attitude ad thrust. This AD and OEB is intricate and meant for Airbus FBW operators so those who are not and holding PPL etc. should not read it and confuse themselves and definitely should refrain from forming any opinion about the aircraft.
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