Cycling The Prop Q

VUOFlyer

VUOFlyer

Well-Known Member
As a refresher for myself while working on my CFI, I was curious as to the exact nature why there's an increase in manifold pressure when you pull prop back during a complex aircraft engine run up? Thanks.
 
As the engine RPM decreases, the amount of air being "sucked" through the intake manifold decreases. Because the ambient pressure remains constant, the manifold pressure gauge will show a rise as the engine slows down (the engine is producing less suction then it does at a higher RPM)
 
I'm back with another question. Let say's when pulling back the prop during run-up, you notice no increase in manifold pressure. Would I then take that as a sign of a possible faulty MP gauge or a issue with the induction system?
 
Doubt there would be an issue with the induction system, since the engine is running. Indication system however, more likely. Fault the gauge in this scenario.
 
VUOFlyer said:
I'm back with another question. Let say's when pulling back the prop during run-up, you notice no increase in manifold pressure. Would I then take that as a sign of a possible faulty MP gauge or a issue with the induction system?
Click to expand...

that or you're moving the prop control too fast
 
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