I gave this subject some thought before I welded up (after eyeball engineering) the motor mount for my first S-7, which used a Subaru so I was on my own design wise. I ended up taking it to an old boy who used to weld in the aero space industry and on hydro electric turbine blades. He was a "pretty good welder" it was just in case I ever lost a blade. Never did and the mount worked great, losing a blade is right up there with mid air collisions and in-flight fires, NO FAIR!

Does this "sounding" test apply the same to constant speed and FP props?

Unfortunately, Ive got a consistent THUD on just one blade of my 11 year since overhaul, 800 hour McCauley 402, where the other two make the nice "dinnggg" sound. Blade looks fine.

I talked to an experienced IA mechanic who'd never heard of this procedure and was somewhat skeptical and suggested cycling the prop and retrying the sounding. Did just that and the sounding is exactly the same. The same blade makes a short "thud", while the others make the nice (almost music quality) ding when knocked. Any suggestions?

Excellent result from what could have been a catastrophic event. What a repair list though: New prop, new engine mounts and possibly a firewall rebuild, engine teardown and rebuild, new seat covers.........

4Whitey wrote:Does this "sounding" test apply the same to constant speed and FP props?

Unfortunately, Ive got a consistent THUD on just one blade of my 11 year since overhaul, 800 hour McCauley 402, where the other two make the nice "dinnggg" sound. Blade looks fine.

I talked to an experienced IA mechanic who'd never heard of this procedure and was somewhat skeptical and suggested cycling the prop and retrying the sounding. Did just that and the sounding is exactly the same. The same blade makes a short "thud", while the others make the nice (almost music quality) ding when knocked. Any suggestions?

Pull it and take it to a prop shop! Do it and have piece of mind.

kevbert wrote:A buddy of mine had been a helicopter mechanic in the army, and waiting for him to finish his airplane preflight inspection was like sitting at the dentist's office. It truly seemed to take forever.

One of his many procedures was to always rap each prop blade near the tip with his knuckles like he was knocking on a door and listen to the sound. One time we were renting a plane in Seattle, and after his usual obsessive-compulsive knocking on the prop, he looked over at me and said we were going to have to get another plane, because the prop was cracked. I was highly skeptical, so he had me rap each end, and sure enough, you could hear the difference. One blade had a ringing sound to it, and the other had a clunking sound with no ring. The local mechanic took off the spinner, scrubbed the prop near the hub with some dye and a brush, and eventually spotted a fatigue crack that was just getting started.

That was about fifteen years ago, and I have rapped my prop on every single preflight since then!

Great info, I will use this on my pre flights. Thanks

A pilot friend of mine relayed a story of a Britten Norman Islander that lost a blade on the takeoff roll in the Virgin Islands, according to him the blade came off and went through the top of the cabin ripping the engine controls out of the pilot’s hand, leaving him unharmed, but unable to shut it down, the engine that lost the blade ripped out of its mounts and the other continued to run wide open, making the plane spin off the runway and into the grass, wild ride! According to him the blade had been overhauled only a few hours prior to the failure, the investigation revieled that a small splinter of steel had been imbedded into the base of the blade during the cleaning process that started a stress riser near the hub end of the blade.

Does this "sounding" test apply the same to constant speed and FP props?

Unfortunately, Ive got a consistent THUD on just one blade of my 11 year since overhaul, 800 hour McCauley 402, where the other two make the nice "dinnggg" sound. Blade looks fine.

I talked to an experienced IA mechanic who'd never heard of this procedure and was somewhat skeptical and suggested cycling the prop and retrying the sounding. Did just that and the sounding is exactly the same. The same blade makes a short "thud", while the others make the nice (almost music quality) ding when knocked. Any suggestions?

Ignorant is bliss as it is not your mechanics airplane. Why even think about not checking the prop? Is your ASS not very important to you? It looks like you have kids??!! .
Get the damn thing checked!!
Did you not read these posts!!
Rant OVER
GT

delete

Looks like there is an extension on the prop??!!
Broke the case two top motor mounts!!Looks like the bolt broke on the bottom!!
I am building a Glastar and putting a 0-360 in it, I have a 0-320 cowling for it, with the 320 it used 2 spacers(5") I think for W&B, I am cutting back my cowl 2 1/2 inches as cowl is that much to long. Going from 0-320fp to a 0-360 CS so will need all the weight saving on that end I can get!
Constant speed on an extension, Harmonic's could exaggerate fast?
There is out there some where where a guy doing aerobatics in a swift lost a blade then the engine coming out of a loop, coming down vertical, he was able to get it on the ground, if he had been horizontal he would have been way back in the CG and never would have made it!
I do have an extra seat for when he gets in the air again!!
GT

Wow, that's some $HiT! Congrats on the landing.
I had an instructor tell me he fixes the engine to the fuselage somehow with a cable. Has anyone ever done that? It seems like a dangling engine with a wild prop wouldn't be much better than a lawn dart, but maybe it's worth it? Or would it just break the cable too?

I have a cable running through the motor mount and back around my firewall in my kitfox. There was a kitfox that shed a blade and the only thing holding the engine on was the battery cables.

M6RV6 wrote:Get the damn thing checked!!
Did you not read these posts!!
Rant OVER
GT

M6RV6 wrote:
Get the damn thing checked!!
Did you not read these posts!!
Rant OVER
GT


GT your rant is much appreciated. I am a conservative owner and have maintained this 206 with an open check book. I talked to an experienced AP-IA and another IA who is a prop shop owner. Neither had heard of this and the first AP suggested that a constant speed prop is assembled with shims that could affect the sound you get when you thunk on the end, so this may not be a reliable test.

I had the prop dye penned and visually inspected by another AP-IA although he didnt remove the blade from the hub, nor the paint. Nothing found.

Prop shop owner says he'd fly it until I can conveniently schedule down time, then OH the prop, due to age not due to dull sounding of one blade. Says if there's no obvious crack or fluid leaking from hub it's likely OK for now.

None of these three mechanics have ever heard of this "sounding" test, I'm not saying its not legit, I'm saying based on the professionals I've spoken to, none of them know if this is a legit test for a prop. If I took everything I read on the web or in forums as gospel I'd be a paranoid wreck. I plan to OH the prop soon, but not tomorrow.

Does anyone know if the sounding test is reliable for finding cracks on CONSTANT SPEED PROPS? Thank you.

Eric
Hope all goes well!

I had the prop dye penned and visually inspected by another AP-IA although he didnt remove the blade from the hub, nor the paint. Nothing found.

You can't due a dye check over the paint!!

the first AP suggested that a constant speed prop is assembled with shims that could affect the sound you get when you thunk on the end, so this may not be a reliable test.

So whats wrong with the shims that 2 out of 3 are different?
If you want to cover your Ass and have a little more warm fuzzy, get an eddy current done, some props require it every 100 hours.
And yes I appreciate your wariness of believing anything you read on the internet. Especially here!

Glad your questioning it, means you are paying attention and care about your bird and family! THANKS
I have been around a lot of metal?? a solid piece always rings!
My $.02
GT

wyomingiswindy wrote: ......... I had an instructor tell me he fixes the engine to the fuselage somehow with a cable. Has anyone ever done that? It seems like a dangling engine with a wild prop wouldn't be much better than a lawn dart, but............

I belive some Reno racers install a "safety cable" like that. A dangling engine might give you some crazy aerodynamics & no power, but at least your CG wouldn't suddenly be so far aft that you'd go into a fatal tailslide.

4Whitey wrote:

M6RV6 wrote:Get the damn thing checked!!
Did you not read these posts!!
Rant OVER
GT

GT your rant is much appreciated. I am a conservative owner and have maintained this 206 with an open check book. I talked to an experienced AP-IA and another IA who is a prop shop owner. Neither had heard of this and the first AP suggested that a constant speed prop is assembled with shims that could affect the sound you get when you thunk on the end, so this may not be a reliable test.

I had the prop dye penned and visually inspected by another AP-IA although he didnt remove the blade from the hub, nor the paint. Nothing found.

Prop shop owner says he'd fly it until I can conveniently schedule down time, then OH the prop, due to age not due to dull sounding of one blade. Says if there's no obvious crack or fluid leaking from hub it's likely OK for now.

None of these three mechanics have ever heard of this "sounding" test, I'm not saying its not legit, I'm saying based on the professionals I've spoken to, none of them know if this is a legit test for a prop. If I took everything I read on the web or in forums as gospel I'd be a paranoid wreck. I plan to OH the prop soon, but not tomorrow.

Does anyone know if the sounding test is reliable for finding cracks on CONSTANT SPEED PROPS? Thank you.

I would have to ask why it seems to work on two out of three blades. Have you tried it on another similar prop? I have been aware of the ring test as applied to cranks and castings most of my life, suspending the part by a rope and smacking it, it should ring if it does not its cracked, works every time without fail, as for a prop blade in a hub, I just don’t know, I find it unlikely that there could be a crack in the blade and not in the paint, preventing a dye penetrant test from showing it, (I’m open to correction on that statement) but then what if the crack is in on the hub end where you can’t see it?

172heavy wrote: but then what if the crack is in on the hub end where you can’t see it?

172heavy that's the $1,000,000 question. All things considered, Its probably time for an OH.

hotrod150 wrote:

wyomingiswindy wrote: ......... I had an instructor tell me he fixes the engine to the fuselage somehow with a cable. Has anyone ever done that? It seems like a dangling engine with a wild prop wouldn't be much better than a lawn dart, but............

I belive some Reno racers install a "safety cable" like that. A dangling engine might give you some crazy aerodynamics & no power, but at least your CG wouldn't suddenly be so far aft that you'd go into a fatal tailslide.

I believe that this is required in the Biplane and F1 classes at reno. There is also a vid on youtube of Dave Morss losing a prop in a lancair 4 during race... I'll look for it.

I decided better play this one safe. I sent my prop in for an overhaul yesterday. I'll let the forum know if they find anything related to the dull sounding blade.

Here's an update to my "dull" sounding prop blade:

I sent my Mac402 to be overhauled because of the dull sounding blade and it had been 11 years. Just heard from the prop shop yesterday. NO CRACKS found anywhere. The dull blade was signifigantly thinner than the other two, and as I remember this blade had a big rock ding filed out of it a few years back. Maybe the cause for the dull sound, maybe not?

John Frank of the Cessnas Pilots Association tells me this is not a reliable way to detect a crack on a constant speed prop. I suspect it only works on a fixed pitch prop.

After the prop was sent in for overhaul, I started thinking (this usually means I'm about to spend some cash).
1. Overhauled Prop can be sold easily.
2. I sure like those smooth, fast, light MT props.
3. Prop de-ice would give me more options when flying in the clouds.

So I spent some cash.....
Overhauled the McCauley.
Sold it back to the prop shop for a fair price.
My new, de-iced MT prop should be here by the end of the week.

I'm chomping at the bit to fly it!

The airframe side of the electric deice will be installed this Fall

Back in the mid eighties, a Navajo crew from Canada were making a night approach to Fort Yukon with a load of passengers. Loud bang, big vibration, then nothing. Right engine shut down due to failure. Crew assumed it was a simple engine failure. Airplane wouldn't maintain altitude. CoPilot looked out with flashlight, and right engine was GONE. Still couldn't figure out why the plane wouldn't maintain altitude on one.

They wound up belly landing on a gravel bar on the Porcupine River (middle of winter, so all frozen), did a really nice job. And, had called in an emergency.

Turns out the right engine had come off the mounts, but was being held suspended behind and below the wing by wiring, plumbing, etc. Lots of drag in that configuration.

The Native Corp went upriver and towed the thing down to FYU, but the entire airframe was pretty much junk as I recall, from the vibration.

I've had one prop tip depart a plane, and it was impressive when three inches of blade left suddenly. Power back and shut down, and fortunately a nice gravel bar to land on.....

Vibration from imbalance is amazing.

MTV