PT6 Question

[Maynard]

My question is, is it harmful to add torque to the engine when the props are in feather? (on the ground) I know the front and back ends are separate units, but not sure on effects.
'Cheers'
Maynard

[iflyforpie]

I'm not sure if it's harmful but it certainly wouldn't be useful

[Troubleshot]

careful of the exhaust heat, if it is a twin your could melt windows.

[Maynard]

Here is a typical scenario...
You start up for whatever reason, you need to keep the props in feather (for a short time) but you need to get your gens online. So, is it ok to push up the torque; and ng to 70% to get the generators on while its in feather?

[GA MX Trainer Dude]

The max limits for torque should be in the checklist for the aircraft.

The -42 in the Beech 200 has a 1100 lbs/ft limit under 1600 rpm

I don't remember any problems with exceeding torque at 70%ng with the prop in feather.


I seem to remember 1000 for the -27 in the DHC-6 - but don't have the info at hand right now so that may be incorrect.

Can't think of too many reasons you would want to run in feather for very long - gets pretty hot with no airflow and don't forget you will get high oil temps with no flow through the oil cooler and high generator temps for the same reason. You can cook the generator after a start and then asking it to produce lots of amps with the only cooling flow coming from the tiny little fan on the starter generator.

MX

[GA MX Trainer Dude]

I forgot to add that the max torque allowed in feather is actually a prop limitation - not really a limitation for the engine. Engine really doesn't care what it is attached to - but prop blades have a tendancy to bend in feather with too much torque!!!

MX

[brownbear]

YES, there is limits. Your operating manuals should say what they are. For a Twin otter it is like 17 psi of torque. All for the prop. There is also a limit for the duration in feather above 32 degrees(or whatever it is) limiting feather to 1 minute(actually anything not forward, reverse included). The wing gets smoking hot.

70% ng is too high in feather. There is no need for that. Just go to fine.

Since you mention 70% I bet its on a Beech. High idle.

Your T5(ITT) will spike if the NG is too low. The extra RPM keeps the temp down. The HP required to turn the generator is what puts on extra fuel to hold the selected rpm(ng). When it's turning at 65% or so it is negated. When the load comes down it can be returned to idle.