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Prop Problem


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Hey guys on my F model I have a new style prop which apparently is way better than the old fat ones. Anyways during takeoff and on the climb I immediately have to pull the power back because it goes past redline to around 2900rpm which is odd because I would think you want full prop and full power on a climb? I've been told it might just be the prop governor or what not but is it bad to run it over the redline?

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If it really is turning 2900 (and not just a bad tach) which is more than 5% and less than 10% overspeed you should read Lycoming's "Mandatory" SB: A logbook entry with any action is required. (For part 91 operations Mandatory may not mean mandatory. ADs are mandatory, SBs "depend".)

 

http://www.lycoming.com/Portals/0/techpublications/servicebulletins/SB%20369C%20%2804-18-2012%29/Engine%20Inspection%20after%20Overspeed.pdf

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I caught mine a few times at 2900 (M20C) and I would pull it back immediately to what was indicated as 2700 on the tach. A trip to LASAR and we put the optical tach reader on it using the prop, and turns out at the 2850 on tach, the prop is actually turning 2633 RPM. So my tach needs replacement here in near future. I checked it at different RPM levels on the tach and the higher the revs the bigget the split. So now I know it indicates 150 high above the 2350 redline mark and take it into account. I will get a new tach, just trying to figure out which way I want to go. Get an optical RPM reader and verify the prop RPM.  

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The iPhone does pretty good at determining rpm based on sound...

Use an rpm app to see how your actual rpm gauge is doing.

Know that there is a small oil cup on the back of the old tach. It gets lubed at annual...

The tach cable is known to wear out over the decades. Cheap to replace.

Best regards,

-a-

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In Canada a check of the tachometer accuracy is part of the Annual inspection. For those with caution or do not operate range marks on the tachometer this is very important.

Clarence

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