since 1940

Engine through-bolts loose. Loose thru bolts

2. Embedment (coming together) of the surfaces.

3. Crankcase fretting. If the crankcase has fretted enough to loosen the through-bolts then tightening the bolts may pinch the crankcase main bearings. Pinched main bearings can cause catastrophic engine failure.

 Before torquing the through- bolts perform a pull test of the propeller. After torquing perform another pull test to see if crankshaft rotation has stiffened.

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Disclaimer: sacskyranch.com contains abundant information relating to aircraft maintenance. The information provided  is not intended to supercede or supplement the F.A.A. approved  maintenance and/or operator’s manuals. Those F.A.A. approved manuals must be utilized when performing maintenance and/or operating aircraft.