July 1, 2004

Somethings Not Right

magneto.jpgAfter a great cross-country night flight I was anxious to get back in the plane. My CFI and I headed out to the run-up area next to the runway to do our pre-flight checklist. The airplane has two sets of magnetos which provide the spark for the engine's spark plugs. There are right and left magnetos to provide a redundancy. While the plane can fly with just one set, you would not want to initiate a flight with only one set functioning. Prior to take-off you check to ensure that both sets work on their own just in case one set fails during flight.

To test the magnetos you run the engine up to about 1700 RPM (for the Cessna 152) and then you go from using both to using each individually. You should not see more than a 100 RPM drop when you go from both magnetos to just one nor should there be more than a 50 RPM difference between RPM level each displayed individually.

Unfortunately, last night the left magneto kept dropping dramatically. This is often caused by a carbon build which is in turn caused from the fuel mixture not being leaned properly in flight. The built up carbon can often be burned off by running the engine at a higher RPM for a short period of time. My CFI and I have done that several times in the past. Today, however, it did not solve the problem. in fact, the problem became worse.

Sadly, we decided to scrub the flight. We took the plane back in and talked to the mechanics. They mentioned the spark plugs probably need to be cleaned or replaced. I am hoping they can get that taken care of today so I can fly tonight.

It is tough to miss out on a night of flying but obviously the smart decision.

Posted by at July 1, 2004 12:02 AM

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