Prop Strike Query

"D. Reid" wrote in message ...
Well..lets review the facts.
Prop strike during taxi. My bet is engine was throttled back to idle.

Wooden prop involved. Yes...wood absorbs a tremendous amount of stress. A
high rpm out of balance condition was most unlikely and sudden stoppage was
most unlikely as well. My guess is...the engine just "spooled down" under
resistance of the prop being "ground away" (sorry...but no pun intended).

So..Being as we are discussing this subject in "rec.aviation.homebuilt" I'm
going on the surmise that the subject A/C is a non-certified engine.

What would I do? I would NOT tear the engine down. For starters. Lyc and
Cont WANT you to do this...not merely for safety sake...BUT because they
want to sell you rebuild parts and componets. Think about. Here you have a
totally dissasembled engine laying on your shop bench and in ALL probablity
checks out just fine. ADMIT it...are you going to put the engine back
together with the same parts that came out of it? Not likely. (what is the
worse that can happen in THIS instance???...a bent prop flange!!!...and
thats about ALL !!! So...if its bent it could be cracked...ok, I'll buy
that. Only thing left to do...CHECK IT OUT !!!...but you dont have to tear
the engine down to do it !!!

Think you broke a crank???...not likely...bent a rod?...probably not.

Here's what you do.
Do a runout measurement of the crank/prop flange (on a C-85 I think .006 is
the max runout). If it's less than that...do a dye penetrant check on the
accessable areas around the flange...if it checks good...install a fresh
prop and go FLY !!!...I WOULD! If the dye check, shows a crack...well your
screwed.

A decent, honest shop should charge about 3 bills max to do this! Of course
YOU have to supply the prop. :-)

Dont assume the worse...but DO take steps to rule it out.

Hope this helps.

Runout doesn't tell the whole story. The crank may have bent
enough to crack (doesn't take much) and sprung back to within limits.
Wooden props would have a hard time of bending it enough, though,
especially at idle.
Small Continental cranks have a habit of cracking between the
first and second rod journals (numbered from the back of the engine).
Don't know why.

Dan