View Full Version : Turboprop PT6 general questions

Central Scrutinizer
18th Apr 2023, 11:29
Hi all,

I have a couple questions regarding normal procedures and habits for a PT6-66 turboprop engine which I couldn't answer from my aircraft's AFM:

1) During engine start, the AFM says to advance the condition lever (CL) to Ground Idle once the NG reaches 13%. I've seen other pilots wait until a higher NG value. Is 13% a minimum, an optimum? Is it better to wait until a higher NG value at all, until the NG reaches a maximum and stabilizes before injecting the fuel or does it matter at all?
2) For cross starting of the second engine, AFM says to move the CL of the running engine to Flight Idle first. I've seen other pilots leave the running engine's CL at Ground Idle and simply advance the Power Lever (PL) instead. I'd rather follow what the AFM says but why do other pilots advance the PL instead of the CL? Does it make any difference?
3) Might sound like stupid questions but I can't find it anywhere on the AFM: is "exercising" the PL and CL with the engines shutdown bad in any way? What about bringing the PL back into the reverse range? Not like I need or want to do this but not sure if doing it would be bad.
4) Is it bad in any way to use reverse on landing with the CL not in the max rpm position? Max rpm would be 2000 but sometimes we use 1800 for noise abatament. In this case, should reverse not be used? Or not be used fully?
5) During the engine run up checks, AFM says "advance CL to MAX RPM and PL to obtain 2000 RPM" then test the prop overspeed governors, then "Check propeller governing to minimum RPM by retarding CL". Does this mean retard the CL to get 1800 RPM (the bottom of the normal operating range), or to retard it all the way to ground idle?

19th Apr 2023, 21:53
#1 the check valves on the min flow circuit pressurise/open around 12% n1 higher rpm gives a bigger initial spurt due to higher pressure

#2 it is an electrical limitation to have a higher n1 for power/cooling cl to max should meet that minimum.many cl's rigging is off not meeting min N1 for hi draw generator ops. Easier to just push up rather than get it rerigged
#3 pulling TO below are idle with engine off is good way to bend linkages in the beta block setup. Prop levers are fine.
#4. Cond lever not in max rpm during reverse operations. The main reason for this is during stol applications to reduce the time for beta reverse application. Been a while, but if I remember it
The overspend governs 106% in forward range and 96% in reverse.

5.wrt the runup. You push up throttle lever to 2000 , and reset speeder spring on the HOG from 106%(2120?) To about 1835. Then check that the main prop gov is actually attached to the prop levers by bringing the prop levers back and governing according. A check of manual feather is required before each flight. I would start the turn and at idle feather, also nice not to blast the terminal/handler

Throttle lever TL
Prop levers PL
Condition levers Cl

Pm if questions