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Touring Motor Gliders Association (TMGA)

static rpm drop


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Hi All,

I'm hoping that you can help me solve the following issue. Two days ago  at 10:00am on a 35 mile flight in my Phoenix the Rotax produced >5000rpm on before roll started on takeoff. On my return flight I noticed a max rpm of 4800rpm even after leveling off. I thought the density altitude could explain the difference as it was about 10 degrees warmer on my return flight. Yesterday I did a static runup on the ground in cooler air and found max rpm to be 4700-4800 rpm. There was the expected mag drop and increase when each mag was tested separately at 3000rpm. I plan to check for possible fuel contamination.

Do you guys have any other thoughts?


George Feldman N33GF

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  • 3 weeks later...
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Was the engine running smoothly at the reduced RPM? I've have the RPM drop 500 rpm a few times, but there was always extra vibration.

Could it be the RPM is correct but is being indicated incorrectly?

Try asking on the Rotax Owners group, too: https://www.rotax-owner.com/en/forum

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Eric thanks for this tip.

After my last post I flew the Phoenix around our pattern 1x and found that on the takeoff roll I was getting 5050rpm substantially higher than the 47-4800 I got on static run up. No discernible vibration at or below 3000 today when I flew 45 miles to my A&p for its annual. I will have him sync carbs and ck them.


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