Thursday, June 18, 2009

Rough Running Engine

While on an IFR training flight today (on the 3rd and final leg) we did the usual runup and the left mag was running rough. Assuming it was a fouled spark plug from our 10-minute delay we did the normal "clean up the plugs" drill with a lean mixture. No improvement. Did the lean drill again. No improvement. Did the drill even dice. The left mag was dropping 750 rpm when it was isolated.

So, we went over to Howard Aviation (we were at Bracket airport) and they were nice enough to get right on it for us. The troubleshooter thought he had found the problem with the spark plugs as they were gapped way, way too big and after regapping them the test equipment showed dramatic improvement. But, alas, after re-installation the engine was still not perfect. Much better, mind you, but not perfect. It dropped about 200 rpm.

Has to be a mag or a lead problem, the consensus was, and the mags are covered under warranty since they were brand new rebuilts when the engine was rebuilt about 120 hours ago.

Tomorrow we will continue with our trouble shooting. It was a long enough day today, that's for sure.

1 comment:

Bob Carpenter said...

I should note that the problem turned out to be a bad wire in one of the magnetos...fixed and returned to action.