flyrotary@lancaironline.net Mailing List Archive

Hi Dave,

Thanks for the reports, I don't feel so lonesome {:>).

Regarding SAG - my analysis is that susceptibility to SAG is proportional to combustion chamber pressure at ignition and the condition of the plugs. The more pressure - the harder it is for the spark to jump the gap, so if your plugs are getting coated with lead/carbon, I would expect to see more SAG with More manifold pressure. Tracy and I have found the same thing (unturboed). At high power setting (higher manifold pressure) the problem becomes more aggravated. Reducing throttle setting helped - but, replacing (perhaps cleaning the spark plug center ceramic cone) is the cure. I must have a fortune in little-used spark plugs setting around waiting for me to have nothing else to do but clean spark plugs {:>).

I only use STEEL for my alternator arm - too much vibration there for aluminum (my opinion of course, but having had aluminum brake line fail - I'm a little leery of the stuff {:>)).

Yes, they do call this experimental for a good reason - never to the point where there is nothing to do.

I had one EFI pump fail early on - and it did fail suddenly - it was on the ground, but one moment it was pumping fuel and the next it was not. Interestingly enough the motor continued to humm and appeared to be turning - but no fuel got pumped. Wish I had taken it apart to find out what had failed.

----- Original Message -----

From: David Leonard

To: Rotary motors in aircraft

Sent: Sunday, September 04, 2005 10:53 PM

Subject: [FlyRotary] Another great flying day = another day of troubleshooting

After a great trip to Santa Paula I finally solved my "compressor surge" issue. Turns out that it was SAG (Spark plug induced Attention Getter) all along. Sigh..   Despite the fact that the plugs were only a handful of hours old, and they worked fine at MAPs in the N.A. range. I was convinced that my power drop issue was surge because it seemed directly related to pressure ratio...

I finally change out the spark plug and wala... no issue. Now i sort of wish I didn't cut off the waste-gate flapper.... oh well.

But life with an auto conversion seems never without an issue or two.

Went out to the plane yesterday ready for a flight but found a puddle of coolant underneath...  sigh...

turns out that my lower radiator cap went bad. Easy enough. Return the next day and install a new one. Give everything a good once over and discover a broken alternator tension arm!!!   Holy S*(^ !! Broken clean through but not displaced very far (hard to notice). From the looks of it, the thing has been broken for at least 20 flight hours!   Hmmm.

So I went home and made a new one - same design until I can come up with better materials and/or design. Looking at the old one there was the end of a hacksaw cut right where break occurred. I should have been more careful grinding it out.

So that is fixed for the time being and I went flying with a friend in an RV-8 with a 180h.p. and c/s prop. Except for initial acceleration on ground roll, I could out perform him in climb and cruise even with my f.p . prop.   :-) COOL!!!!

But then I found my next problem....

Return fuel flow started drooping. Where I normally see 30+ gph returned to the tank, I was seeing about 20gph. We landed for lunch and I searched for signs of a fuel leak - none. Fuel flow seem normal on the ground, as did fuel usage for the flight. hmmm.

On the way home the problem recurred, and flow continued to dwindle. at 4gph I turned on the aux pump and solved the problem. Sure was nice to have 2 of them.

I always pictured these pumps failing all of a sudden, but this one just sort of faded. Has anyone had experience with this? I will check the wiring and fuel filter... and report back. Only 150 hrs on this pump.... I hope the next one last longer....

--
Dave Leonard (just ordered a replacement pump from Tracy - but he is going away... sigh)
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html