Piper Navajo throttle sensitivity

ZeroPapaGolf

Well-Known Member
You guys who have some Navajo experience, what has been your experience regarding the throttle. On ours it seems like almost all the power is in the first inch of travel. That is, going from cruise power of 31" to approach power of 21", it's less than half an inch of movement. Is that pretty normal for a Ho? Kinda makes a 1"/minute reductions difficult. Attached is a photo at cruise power.


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Roger Roger

Paid to sleep, fly for fun
Sounds like perhaps an issue with something in the turbo control system, specifically that perhaps the differential pressure controller is not governing waste gate position so your UDP is running 40+ inches all the time instead of just MP+6 or so like its supposed to be at part throttle. Of course it's really odd that it would be common to both engines. So maybe something isn't hooked up right?
 

Patrick

Well-Known Member
Sounds like perhaps an issue with something in the turbo control system, specifically that perhaps the differential pressure controller is not governing waste gate position so your UDP is running 40+ inches all the time instead of just MP+6 or so like its supposed to be at part throttle. Of course it's really odd that it would be common to both engines. So maybe something isn't hooked up right?
This would make a lot of sense actually.
 

Hammertime

Well-Known Member
As stated above, maybe a linkage problem. However, remember that throttle sensitivity changes with altitude. at higher altitudes the higher power range of the throttle should be less sensitive. (e.g. from 50% travel to 100% travel should = a smaller change in MP). From what you are describing though, it sounds like you have the opposite problem. IDK anything about Navajo systems, but have your mechanic look at the throttle rigging on the carb/throttle body.
 

Patrick

Well-Known Member
As stated above, maybe a linkage problem. However, remember that throttle sensitivity changes with altitude. at higher altitudes the higher power range of the throttle should be less sensitive. (e.g. from 50% travel to 100% travel should = a smaller change in MP). From what you are describing though, it sounds like you have the opposite problem. IDK anything about Navajo systems, but have your mechanic look at the throttle rigging on the carb/throttle body.
Not exactly. What he's describing is likely the result of the engine making too much boost, too quickly, due to an issue in the turbo control system.
 

Romulus

Well-Known Member
There are guys on here with more ho time than I, but the dozen or so Navajos I have flown in the past 1000 hours arent like that. Sounds like something is rigged wrong.
 

TwoTwoLeft

o- - - - - - -l
The one I currently fly and the few others I've been in, I remember the throttles being sensitive. When stage cooling from 30" to 25" the throttles don't move much. IIRC the throttles seem to travel back about 1/3 of the way when reducing power from WOT to 40" for climb, down to 30" for cruise.
 
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