Home> Maintaining your Continental  and Lycoming engine

A. Dialing the flange is where you rotate the crankshaft and measure how much bend there is at the flange. This ridiculous theory assumes that the only damage that could possibly occur to the engine is at the crankshaft flange. Your Continental crankshaft has a skin of glass hard nitrated steel; it is very strong but brittle, and like glass, it cracks before it bends. Lets also not forget that this three-inch piece of hardened steel is stronger than the one-inch thick aluminum bearing boss that holds the crankshaft in position?  The engine crankcase needs to be inspected for cracks also. You cannot do these inspections without disassembling the engine.

Sudden stoppage from idle may be more damaging than the prop strike at full power. For example, if your engine uses a gear driven alternator, and the engine stops in 90 degrees of rotation; the time to stop the rotor is .015 second. To stop the rotor this quickly imparts a tangent force on the rotor shaft of 874 pounds. Expect to find cracks on the crankshaft's alternator gear mounting flange. Those of us less clairvoyant than  your mechanic need to look inside the engine.

Another consideration; our shop did approximately 12 prop strike examinations per year over several decades. This valuable experience allowed us to talk to the pilot about the prop strike just as your mechanic has done. But unlike your mechanic, we then disassembled the engines and examined them using Magnaflux, Florescent Penetrant NDT and micrometer inspections. We were never able to predict before inspection which engines would be damaged and which ones would not.  Because of our shop experience, we know enough to know that we don't know if your engine was damaged.

 

	Crack cannot be detected without removing crankshaft from the engine. How could "dialing the flange" possibly detect this type of damage caused by sudden stoppage?
	Another suspect area for cracking caused by a propeller strike on Continental engines.
	Same area on the Lycoming crankshaft How can dialing the flange detect a crack on the rear surface of the crankshaft slinger?

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