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Date: Mon, 22 May 2006 20:59:41 -0700
From:  <tonyslongez@cox.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Another case of heat-soaked coils?
Cc: John Slade <sladerj@bellsouth.net>
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---- John Slade <sladerj@bellsouth.net> wrote: 
> Yesterday I took a friend for a ride and the engine purred sweetly for 
> the entire trip. Looking back, the only thing different was that there 
> didn't seem to be an rpm drop when I disabled leading or trailing coils 
> during the runup.
> 
> Today all was normal during runup (except perhaps the coil disable 
> causing no rpm drop) and full power got me 5300 before I couldn't hold 
> it any more on the brakes. Take-off and climb were normal. On the 
> downwind I was showing 5800 rpm so I decide to coursen the prop. When I 
> did I felt a splutter. I reduced throttle and the engine ran normally. I 
> increased throttle. More splutter. I reduced throttle and it ran 
> normally at 4600. Any more throttle and all I got was reduced power & 
> popping and spitting. I circled the field trying mixture adjustments, 
> checking fuel pressure on both pumps, coil & injector defeat and 
> swapping to B computer. Nothing seemed to make any difference, so I landed.
> 
> The only change since the previous flight was that I'd replaced the 
> plugs with a clean set - not new - just clean. Suspecting a bad plug I 
> let the engine cool down a bit, then installed new ones. Later in the 
> day the engine ran fine during taxi and again reached 5300 on runup. 
> Acceleration seemed normal then, halfway through the takeoff roll, I 
> felt a splutter, so I aborted and rolled off the runway.
> 
> When I added power to taxi clear of the runway the spitting got much 
> worse. So bad, in fact that it seemed to be running on one rotor and 
> there was insufficient thrust to move the plane forward. I tried 
> adjusting mixture and defeating injectors & coils again and the engine 
> eventually stopped. I was able to restart, but had the same symptoms. 
> The rpm was fairly steady at 1100 or so, but this was the max rpm I 
> could get. The EM2 was flip flopping rpm readings 
> 2300...400...2100..800...every couple of seconds.
> 
> I called Tracy from right there on the taxiway. As always - he took the 
> call and listened to my unscientific whining. Thank you Tracy :)  
> Anyway, his best thought was that it sounded like it might be a coil 
> heat-soak problem. It definitely seems heat related, and my cowl has 
> been running a bit hotter since I installed the new T04 turbo.
> 
> I pushed (yes pushed) the plane back to the hangar, then tried turning 
> the prop to feel all six compression strokes. To my untrained arm 
> muscles the compressions all felt the same. I ordered 4 new coils and 
> will report if this corrects the problem. Whether it does or not, I see 
> a separate air duct for the coils in my future. The blow tube I 
> installed may not be providing enough cooling. I once tried installing a 
> temp sensor at the coils, but this sent other EM2 temp readings haywire 
> - induced current from the ignition? - so unfortunately I don't have 
> temp readings on the coils.
> 
> Anyone have additional thoughts on this?
> 

How about those heat stickers? they use on the Rotorway helicopter gear boxes and such I guess if the sticker gets over a certain temp it changes color or something like that.

Tony