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

"Dick" wrote in message . com...
Nosegear failed during taxi and had a wooden prop strike on pavement. prop
is toast but wondering about the old C-85. consensus is leaning towards
everything okay if no vibration and tracks true upon startup of new,
balanced prop.

comments appreciated, Dick


A few years ago I met a guy loading a Champ (with a C-85) onto a
truck at a backcountry strip. He told me an amazing tale of his
crankshaft snapping in flight over some seriously rought terrain
(Great Bear Wilderness Area near 8U4). As it turns out, he had just
enough altitude to glide to the strip and made a safe landing.

I asked him if he knew why the crankshaft snapped and he had no
idea. While I was looking over the plane, I noticed that the metal
nosebowl had a small dent and asked about it. He told me that he'd
taxied into a snowbank several months earlier. When I asked if he'd
torn the engine down he replied that he'd hit the snow bank slowly at
idle, and was sure that the engine wasn't damaged. Supporting his
assumption was the fact that the plane had flown a whole 20 hrs.
without a problem since the prop strike.

Spontaneous crankshaft breakage doesn't happen very often. You be
the judge.

John Galban=====N4BQ (PA28-180)

John Galban wrote:

Spontaneous crankshaft breakage doesn't happen very often. You be
the judge.

John Galban=====N4BQ (PA28-180)

Sure they do. Just ask Amy Laboda.

flamesuit on

One more reason I like my rotary engine 8*)

INCOMING!!

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