Crap! Can't fly to S37 tomorrow...

[RotaryWingBob]

We have a stuck exhaust valve on the R22 again, so it's not airworthy, and a partner has the Cherokee reserved.

Sorry Jim, Ed, et al...

Hope you have a successful fly-in

I swear the aviation gods don't want me to go to fly-ins which are organized by anybody else but Toby

 

[ScottM]

We have a stuck exhaust valve on the R22 again,

MMO time?

why does it keep getting stuck?

 

[RotaryWingBob]

MMO time?

why does it keep getting stuck?

I'll bite, what's MMO?

The shutdown sequence for a piston helicopter is more complicated than for a fixed wing because you're going from gobs of power (in a hover) directly to shutdown. So there has to be a cooling cycle so you don't shock cool the engine.

The POH calls for a cooling period at 70-75% RPM until the CHT gage drops. Then, reduce the throttle to idle, and begin to disengage the clutch, wait 30 seconds, mixture to cutoff, wait until clutch fully disengaged (light goes out), then all switches off.

I've been told that if you don't wait long enough at 75%, you can get a carbon buildup around the #1 and #2 exhaust valves. It may be that one of us is in too much of a hurry to shut the engine down.

I have an email in to Mark Boyer at Pocono Air asking him if we need to modify our shutdown procedure in light of this, for example, maybe allowing an extra 60 seconds after the CHT drop.

 

[ScottM]

I'll bite, what's MMO?

Marvel Mystert Oil. Lot of OWTs about it helping to stop sticky valves.

The shutdown sequence for a piston helicopter is more complicated than for a fixed wing because you're going from gobs of power (in a hover) directly to shutdown. So there has to be a cooling cycle so you don't shock cool the engine.

The POH calls for a cooling period at 70-75% RPM until the CHT gage drops. Then, reduce the throttle to idle, and begin to disengage the clutch, wait 30 seconds, mixture to cutoff, wait until clutch fully disengaged (light goes out), then all switches off.

I've been told that if you don't wait long enough at 75%, you can get a carbon buildup around the #1 and #2 exhaust valves. It may be that one of us is in too much of a hurry to shut the engine down.

I have an email in to Mark Boyer at Pocono Air asking him if we need to modify our shutdown procedure in light of this, for example, maybe allowing an extra 60 seconds after the CHT drop.

Thanks, rotors are whole different animal and I apreciate your post educating us fixed wing guys.

That make a lot of sense. Now I know why after I see helicopters land I see them sitting and just running their engines. I normally would be mildly annoyed at the noise and the potential for wake turbulance when I would need to taxi by.

 

[RotaryWingBob]

I normally would be mildly annoyed at the noise and the potential for wake turbulance when I would need to taxi by.

I try to be real careful about exposing other a/c to my rotor wash. Even in an R22 it's pretty strong if you're out of ground effect (skids a couple of feet high), and it's much stronger in an R44. And humongous in larger turbine helicopters.

That's the reason that most of us try to park well away from other aircraft, and will sidestep if we think we're too close to a fixed-wing taxiing or on the runway.

I suspect that a larger helicopter (including the R44) could possibly invert a 152 or other light high wing.