June 2002 Issue

Queries: 06/02

Excess Precession?
Iíve been flying a Mooney M-20J for 10 years and have noticed that the vacuum-driven heading indicator seems to precess at different rates at different times.†

Sometimes, Iíll reset every 10 minutes or so, other times more like every 20 minutes.† The airplane was new 10 years ago when I bought it, by the way, and the vacuum system is fine.

The vacuum doesnít vary according to the gauge and my mechanics say thereís nothing wrong with the instrument. Whatís your view?

-Paul D. Larsen
Fargo, North Dakota

You didnít mention if the heading indicator is an HSI. If it is and itís the slaved Century NSD-360 commonly found in Mooneys, we w...

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