As the spinny thing turns...or suddenly stops

[ChemGuy]

Im looking at a single place exp (wood/fabric) with a C75 engine. Several years and 200+ hours ago the current owner doffed the landing and broke some stuff that normally hangs off the bottom of the fuse with black rubber things. At this time he also made the spinny thing on the front of the plane hit the ground. The spinny thing was wooden. It was landing so low power/idle.

Engine was dialed but not torn down. Low hanging stuff was rebuilt and plane has been flown over 200 tach hours since.

I know the horror stories (why there are inspection SB and AD's) but what is the collective thoughts on flying this thing as is? How much gamble is it that a cracked crank, con rod, gear tooth, etc would show up as a sudden stoppage of the spinny thing after 200+ hours?

The plane also had a crack found a few years ago in the main spar. They removed the fabric, removed some ribs and added a doubler to each side of the spar. These doublers total 2/3 of the orginal spar thickness. Replaced ribs and recovered. Plane has flown 200 odd hrs and several years since this.

POA thoughts on spar doublers like this?

I would plane to fly with a chute, (even if engine/wing wasnt ???) so there's that. I also fly in an area that is heavily covered by farm fields and a few forests, so Ive got that going for me....
Plus ive led a pretty danger heavy lifestyle...jumping out of planes with a rifle and explosives, racing motorcycles, etc.

Ok so now tell me why I should/shouldnt buy this NDH beauty...lol

 

[kyleb]

I'd evaluate the spar repair in accordance with 43.13 if it passes that test, I'd be happy with it.

The crank? No idea.

On the other hand, since it is an experimental, you could replace the spar and then disassemble the engine check the crank and reassemble the thing yourself.

 

[ChemGuy]

Yeah...im kind of leaning to something like that Kyle. Up here flying an open cockpit is only a 6-8 month gig. So i could fly it and then work on something (wing/engine) next winter.

 

[Clip4]

Bent crank or not, I would not fly an engine suffering a sudden stop without internal inspection.

 

[Tom-D]

Bent crank or not, I would not fly an engine suffering a sudden stop without internal inspection.

Your misconception is,, a wooden prop will not cause a quick stop, they simply shatter, then the engine simply stops because it does not have the inertial energy to carry it thru the next compression stroke.

 

[Tom-D]

The crank? No idea.

9999% of the time with a wooden prop there will be no damage, the only damage will occur when the prop shaft is bent, (prop Flange) It passed inspection by being dialed out to lass than .005" it's good to go.

 

[Tom-D]

POA thoughts on spar doublers like this?

Sounds like a typical spar repair, look for a 337. It should have one.

 

[Tom-D]

Ok so now tell me why I should/shouldn't buy this NDH beauty...lol

Get as smart as the seller on wooden rag bags, make up your own mind.

 

[kyleb]

Sounds like a typical spar repair, look for a 337. It should have one.

It's an experimental. No 337.

 

[Tom-D]

Sounds like a typical spar repair, look for a 337. It should have one.

It's an experimental. No 337.

YEP ! I missed that.

 

[brcase]

Bent crank or not, I would not fly an engine suffering a sudden stop without internal inspection.

This used to be common practice until the engine manufactures started requiring mandatory tear downs. (Not that many years ago) Dial the crank, if not bent put a new prop on and go fly it. I have quite a few hours behind engines that were just dialed out after a prop strike.

I suspect the mandatory tear downs are more of a marketing strategy than anything. Sure it is safer to check, but I haven’t see any data indicating how much safer. But it does sell engines and engine parts when the insurance company is paying for them.

Brian

 

[Tom-D]

This used to be common practice until the engine manufactures started requiring mandatory tear downs. (Not that many years ago) Dial the crank, if not bent put a new prop on and go fly it. I have quite a few hours behind engines that were just dialed out after a prop strike.

I suspect the mandatory tear downs are more of a marketing strategy than anything. Sure it is safer to check, but I haven’t see any data indicating how much safer. But it does sell engines and engine parts when the insurance company is paying for them.

Brian

75 horse, means a C-75 TCM. just a service bulletin that says when a prop must be removed for repair, the iron parts should be inspected.

 

[Clip4]

This used to be common practice until the engine manufactures started requiring mandatory tear downs. (Not that many years ago) Dial the crank, if not bent put a new prop on and go fly it. I have quite a few hours behind engines that were just dialed out after a prop strike.

I suspect the mandatory tear downs are more of a marketing strategy than anything. Sure it is safer to check, but I haven’t see any data indicating how much safer. But it does sell engines and engine parts when the insurance company is paying for them.

Brian

The Top 10 Leading Causes of Fatal General Aviation Accidents 2001-2016:

1. Loss of Control Inflight
2. Controlled Flight Into Terrain
3. System Component Failure – Powerplant
4. Fuel Related
5. Unknown or Undetermined
6. System Component Failure – Non-Powerplant
7. Unintended Flight In IMC
8. Midair Collisions
9. Low-Altitude Operations
10. Other

 

[Tom-D]

The Top 10 Leading Causes of Fatal General Aviation Accidents 2001-2016:

1. Loss of Control Inflight
2. Controlled Flight Into Terrain
3. System Component Failure – Powerplant
4. Fuel Related
5. Unknown or Undetermined
6. System Component Failure – Non-Powerplant
7. Unintended Flight In IMC
8. Midair Collisions
9. Low-Altitude Operations
10. Other

Total engine failures nation wide all engines. I'd bet there isn't a C-75 in the mix.
Specially after a wooden prop strike. Stromberg carb maybe.

 

[Clip4]

Total engine failures nation wide all engines. I'd bet there isn't a C-75 in the mix.
Specially after a wooden prop strike. Stromberg carb maybe.

Your life to wager, but unfortunately the lives of the people on the surface and passengers are not yours to wager.

 

[brcase]

The Top 10 Leading Causes of Fatal General Aviation Accidents 2001-2016:

1. Loss of Control Inflight
2. Controlled Flight Into Terrain
3. System Component Failure – Powerplant
4. Fuel Related
5. Unknown or Undetermined
6. System Component Failure – Non-Powerplant
7. Unintended Flight In IMC
8. Midair Collisions
9. Low-Altitude Operations
10. Other

Here is the number I am sure you don't have. But is pretty well know than newly overhauled/new engines have a higher failure rate than ones that have been in service for some time. (my google search showed 1st 500 hrs the most likely).
Are you more likely to have a mechanical engine failure in the 1st 100 hours after a low rpm prop strike or during the 1st 100 hours of an overhauled engine? 50 hrs? 500hrs?
https://blog.aopa.org/aopa/2014/03/13/do-tbos-make-sense/

Brian

 

[JAWS]

Federal law does not require a tear down inspection on either Lycoming nor Continental engines. There are service bulletins from both manufacturers however that recommend inspection. Why is it that people continue to perceive that there is a federal requirement mandating an inspection?

Lycoming does however have an AD against most of their engines that must be complied with which requires the removal of the accessory case cover to inspect the crankshaft accessory drive gear and the dowel for it that is in the crankshaft.

Do not confuse this with what is prudent to do. As mentioned by pervious posters even a prop strike that is viewed as minor can cause bigger problems than you think. I have a friend who has a little Continental engine on his Cub that suffered a prop strike with a wood prop. The prop shattered, and it was perceived that the engine would be ok. Upon closer inspection, it was not ok, and it was a good idea it came apart because it needed a new crank.

mondtster, Sep 28, 2016
#8

Prop strike on Continental
Discussion in 'Maintenance Bay' started by kevmor99, Sep 28, 2016.

 

[Clip4]

Here is the number I am sure you don't have. But is pretty well know than newly overhauled/new engines have a higher failure rate than ones that have been in service for some time. (my google search showed 1st 500 hrs the most likely).
Are you more likely to have a mechanical engine failure in the 1st 100 hours after a low rpm prop strike or during the 1st 100 hours of an overhauled engine? 50 hrs? 500hrs?
https://blog.aopa.org/aopa/2014/03/13/do-tbos-make-sense/

Brian

Thanks for the link to the totally unsubstantiated editorial. Anyone who flys behind an engine subject to a sudden stoppage without a tear down inspection is nuts.

 

[chemgeek]

This used to be common practice until the engine manufactures started requiring mandatory tear downs. (Not that many years ago) Dial the crank, if not bent put a new prop on and go fly it. I have quite a few hours behind engines that were just dialed out after a prop strike.

I suspect the mandatory tear downs are more of a marketing strategy than anything. Sure it is safer to check, but I haven’t see any data indicating how much safer. But it does sell engines and engine parts when the insurance company is paying for them.

Brian

Insurance companies willingly pay for teardowns after prop strikes. What do their actuaries know that operators don't? If insurance companies didn't think it was cost effective, they wouldn't do it.

 

[pigpenracing]

Thanks for the link to the totally unsubstantiated editorial. Anyone who flys behind an engine subject to a sudden stoppage without a tear down inspection is nuts.

Well call me nuts..
I bought a Christen Eagle a few years back with the same deal.... It was a composite prop strike... The crank was dialed. Airframe rebuilt and it is still flying. Don't overthink things.
A wood or composite prop will break and not tear up a steel crank.
Now if it was a metal prop that hit pavement that would be a whole completely different story.
I flew the crap out of the plane and pulled lots of G's. I never once thought about that crank.
I did have another Eagle with a 540 that the crank broke in half for no apparent reason. It never had a prop strike.
You never know.....
Sounds like this is a cheap little plane to toot around in. It would cost more for the engine teardown and rebuild than the plane is worth....

 

[Tom-D]

Anyone who flys behind an engine subject to a sudden stoppage without a tear down inspection is nuts.

unsubstantiated personal opinion.

 

[Tom-D]

Insurance companies willingly pay for teardowns after prop strikes.

don't forget they are pro-rated to TBO.

 

[ChemGuy]

I figured this would turn into a every stoppage must be torn down vs the meh...ive done it and seen it done and its fine.

The biggest thing to me about the strike was it was 5 or 6 years ago and over 200hrs since. But i have read reports of failure happaneing after a lot of hours following a strike or something similar. So while i feel the chances of the crank or rod coming from together due to a crack caused by the strike are very small, its a non-zero number.

I asked myself...what if it was 500hrs or a 1000hrs ago....and i got the same answer...its probably fine.

I do appreciate the input...and as pigpen pointed out...even if i disassembled/re-assembled the engine the cost of inspections, parts, etc would come very close to the cost of the plane. Although going thru the motor would definitely be on the list, i would probably fly it this year and then see where its at.

 

[Clip4]

unsubstantiated personal opinion.

If I ever had first hand knowledge some idiot returned a sudden prop stopped engine to service by dialing the crank and installing a new prop, I would dial the FAA so they could get involved.

 

[Eric Stoltz]

If I ever had first hand knowledge some idiot returned a sudden prop stopped engine to service by dialing the crank and installing a new prop, I would dial the FAA so they could get involved.

Team work makes the dream work!

 

[Tom-D]

If I ever had first hand knowledge some idiot returned a sudden prop stopped engine to service by dialing the crank and installing a new prop, I would dial the FAA so they could get involved.

The biggest thing you refuse to believe, is that this C-75 wasn't quick stopped, a wooden prop will not do that.

Plus there is no FAR rule that requires a quick stopped engine be torn down, So what would you expect the FAA to do?

There is realism and your beliefs never the two to meet.

 

[Tom-D]

This used to be common practice until the engine manufactures started requiring mandatory tear downs.

Brian

Show me where the manufacturers have such a rule?

 

[kyleb]

If I ever had first hand knowledge some idiot returned a sudden prop stopped engine to service by dialing the crank and installing a new prop, I would dial the FAA so they could get involved.

There's a new sheriff in town... Gonna be cracking down on some of the nefarious activities been goin' on around here.

 

[Clip4]

There's a new sheriff in town... Gonna be cracking down on some of the nefarious activities been goin' on around here.

No, not at all. Fortuneatly I seldom run into the 1% who insist on flying junk and putting lives at risk doing so.

 

[Tom-D]

No, not at all. Fortuneatly I seldom run into the 1% who insist on flying junk and putting lives at risk doing so.

Lots more than 1%, there are a whole multitude of engines that dialed and returned to service.
It is a well practiced routine in all of GA.
Your beliefs are more the 1%.

 

[Clip4]

The biggest thing you refuse to believe, is that this C-75 wasn't quick stopped, a wooden prop will not do that.

Plus there is no FAR rule that requires a quick stopped engine be torn down, So what would you expect the FAA to do?

There is realism and your beliefs never the two to meet.

Watched several people die in engine failure accidents over the years, being too cheap to perform proper maint. was a factor in all but on of them.

 

[Tom-D]

Watched several people die in engine failure accidents over the years, being too cheap to perform proper maint. was a factor in all but on of them.

You forgot to answer the question.

The issue is, dialing a crank flange is proper maintenance.

 

[bflynn]

If I ever had first hand knowledge some idiot returned a sudden prop stopped engine to service by dialing the crank and installing a new prop, I would dial the FAA so they could get involved.

You’re the one who ratted out Bryan, aren’t you?

 

[kyleb]

You’re the one who ratted out Bryan, aren’t you?

Speaking of Bryan, where'd he go?

 

[Kenny Phillips]

Insurance companies willingly pay for teardowns after prop strikes. What do their actuaries know that operators don't? If insurance companies didn't think it was cost effective, they wouldn't do it.

True now, true 21 years ago when I Q-tipped a propeller. Just a ringing sound, engine never stopped. Got another prop after the local mechanic dialed the crank, flew it back home, but my partner was worried. A quick call to the insurance company and we had a TDI, no extra charge. No internal damage, but I paid for new rings and bearings, even though it was only 300 SMOH, because it was open.

 

[wanttaja]

The Top 10 Leading Causes of Fatal General Aviation Accidents 2001-2016:
1. Loss of Control Inflight
2. Controlled Flight Into Terrain
3. System Component Failure – Powerplant
4. Fuel Related
5. Unknown or Undetermined
6. System Component Failure – Non-Powerplant
7. Unintended Flight In IMC
8. Midair Collisions
9. Low-Altitude Operations
10. Other

I looked at the fatal Cessna 172 accidents from 1998 to 2015, and my results were different. This list does not include accidents that occur during instruction.
_Rating_|____________Cause___________|_Percent_|
____1___|______Pilot Miscontrol______|__21.6%__|
____2___|______Midair Collision______|__17.1%__|
____3___|_________VFR to IFR_________|__14.4%__|
____4___|___Manuevering at low alt___|__12.3%__|
____5___|_______Disorientation_______|___5.5%__|
____6___|________Undetermined________|___4.8%__|
____7___|__Loss of Control (Unknown)_|___3.1%__|
____8___|_Undetermined Loss of Power_|___2.4%__|
____9___|_______Fuel Exhaustion______|___2.1%__|
___10___|______Maintenance Error_____|___1.4%__|
___11___|______Engine Mechanical_____|___1.4%__|
___12___|______Other Mechanical______|___0.7%__|

In my data, for the Cessna 172 fatalities at least, mechanical issues don't even appear until well down the list.

Ron Wanttaja

 

[Clip4]

You forgot to answer the question.

The issue is, dialing a crank flange is proper maintenance.

Said the guy trying to get a red tagged crank back in service.

 

[Tom-D]

Said the guy trying to get a red tagged crank back in service.

Knowing the legality of doing some thing is not trying to place it in service.
Now you are grasping trying to make me look bad, when you are the one that has the wrong concept.
You still haven't answer the question of, what you expect the FAA to do when no rules have been broken.

 

[Cap'n Jack]

The biggest thing you refuse to believe, is that this C-75 wasn't quick stopped, a wooden prop will not do that.

Plus there is no FAR rule that requires a quick stopped engine be torn down, So what would you expect the FAA to do?

There is realism and your beliefs never the two to meet.

Your misconception is,, a wooden prop will not cause a quick stop, they simply shatter, then the engine simply stops because it does not have the inertial energy to carry it thru the next compression stroke.

https://www.federalregister.gov/doc...y-textron-lycoming-direct-drive-reciprocating

Definition of Propeller Strike
(i) For the purposes of this AD, a propeller strike is defined as follows:

(1) Any incident, whether or not the engine is operating, that requires repair to the propeller other than minor dressing of the blades.



(2) Any incident during engine operation in which the propeller impacts a solid object that causes a drop in revolutions per minute (RPM) and also requires structural repair of the propeller (incidents requiring only paint touch-up are not included). This is not restricted to propeller strikes against the ground.


(3) A sudden RPM drop while impacting water, tall grass, or similar yielding medium, where propeller damage is not normally incurred.

I'm pretty sure the RPM drops while a wooden propeller is being broken.

Why isn't it prudent to perform the inspection? Even on a Continental?

In fact, you seem to have changed your mind on this:

The deffination of a prop strike is different on Lycomings than Continentals, Lycoming says any time a prop strikes any thing that will cause a loss of RPM it is a prop strike.

Continental says any time a prop must be removed for repair, it's considered a prop strike.

OTOH, the prop in original post wasn't removed for repair, it was removed for replacement and that means the engine is OK.

 

[Tom-D]

https://www.federalregister.gov/doc...y-textron-lycoming-direct-drive-reciprocating


I'm pretty sure the RPM drops while a wooden propeller is being broken.

Why isn't it prudent to perform the inspection? Even on a Continental?

In fact, you seem to have changed your mind on this:

OTOH, the prop in original post wasn't removed for repair, it was removed for replacement and that means the engine is OK.

What's the difference between prudent and legal?

Using the Lycoming AD description of a Prop strike, for a C-75, Now there is a laugh
Now what's a real laugh, we went from 1920 something to present and neither major manufacturers having come out with a mandatory requirement requiring the tear down because of a prop strike.
and the FAA hasn't changed their rules on the subject ever.

Yet many go around screaming it must be torn down.
Seems the people in the know don't agree.