Prop Srike question

[Arthur]

I am aware of TC SB 96-11A and I have decided not to purchase  3 planes that had strikes and the engines were not torn down. I am also aware of a company that sells planes after a prop strike that clocks the prop and dye tests the parts of the engine that they can see with a scope.  I am not trying to make this about who does what. The SB says, " This damage can result in catastrophic engine failure.". The question I have is this is anyone aware of a case where the result of a prop strike and non tear down procedure was used to return the aircraft resulted in this failure? Or is this the type of statement that was generated due to liability concerns.

Secondly has anyone had their engine torn down and replaced in service without any changes to the engine caused by the Prop Strike or is some hidden damage discovered and parts replaced?

Prop Strike - Copy.pdf

[carusoam]

What part of the crank can crack and break, is it visible?

Kind of like looking for broken bones without an X-ray machine... so...

Yes and yes... (in reverse order)

1) Yes, somebody mangled the prop on one of my planes... tear down would have revealed nothing...proceeded to the next step anyways...

2) Yes, there is a sad story that goes with losing a prop... props departing airplanes have terrible side effects... a weight and balance issue immediately occurs, and may be very difficult or impossible to trim out... while in Land Now mode...

 

Rules have changed recently, defining what a prop strike is and how the inspection needs to be carried out...

The rules were changed based on actual data analysis...

The old procedure for using a micrometer to measure for run-out didn’t account for cracks and crack-propagation that actually occur...

 

it is easy to not buy into unknown risk...

it is tougher to spend money when the prop strike occurs on your watch...

 

One thing to look at is how long ago the prop strike occurred...  if it happened before the rules change and your seller isn’t hiding anything... the risk is lower...

If it happened recently, and no hours are on the engine and new prop, this is a do not touch... less then pricing as a run-out engine...

run-out engine’s still have useable expensive parts... an unknown crank issue is an expensive surprise when it becomes known...

 

When buying a used plane, You want to buy with as few risks as possible...  this is the reason NDH is important to some people...

Having unknowns can leave you with some unease...

Asking this question to your mechanic can be important... they are the person that is going to go through your logs to determine AW issues... this goes with the PPI... don’t send anything to a PPI that has a high chance of failure... that can be expensive...

Some planes are better for other people to own... some are better for first time buyers... some are in the middle...

PP thoughts only, not a mechanic...

Best regards,

-a-

[RobertGary1]

I asked Maxwell how he retrieves gear ups from remote airports. He said they just raise the plane, drop the gear and throw another prop on it and ferry it to his shop. I asked him if he worries about flying behind an engine that just had a prop strike and he said not at all. That's a ferry flight but maybe somewhat of a datapoint from the guy who has probably repaired more than anyone on earth.

 

-Robert

[Cody Stallings]

That’s a Good Question.

I know of one on a Citabria that failed 22hrs after a new Prop was installed.

It was nosed over on landing, bey little curl on the Prop tips.

Thats the only one that I personally can speak off.

However, I have heard about parts failing inspects(crankshafts) during tear down inspection after prop strikes.

There are plenty of people that don’t wanna incurr the cost associated with it.

When I was in the airplane buying market a few months ago, I was reviewing the logbooks on a perspective backward tail plane.

I noticed that two years into the airplanes life, the Propeller hub serial number changed(who would notice that other than me..lol).

At no point in the logs did it ever say anything had happened other than a lower cowl repair.

I backed away at that time.

That engine may run to TBO an beyond, but my wife an me aren’t going to be the people to try it.

[David Lloyd]

The AD involving prop strike on a Lycoming calls for replacement of the crank gear bolts.  It can be done with the engine still on some airplanes.  It is mandatory for any degree of prop strike.

I had a prop strike, called two shops and neither would do the AD without doing the Lycoming SB which is not mandatory.  The shops and Lycoming say the AD did not go far enough.  Insurance adjuster must have heard that before, no hesitation, they paid for the SB. Mags, bearings, a bunch of bolts were replaced.  Once the case is split for the inspection the shop will find other things to replace that had nothing to do with the prop strike.  A little corrosion on the cam, a spalled lifter, etc. the customer will be on the hook for.

The AD and SB have been out for several years.

 

[ArtVandelay]

I asked Maxwell how he retrieves gear ups from remote airports. He said they just raise the plane, drop the gear and throw another prop on it and ferry it to his shop. I asked him if he worries about flying behind an engine that just had a prop strike and he said not at all. That's a ferry flight but maybe somewhat of a datapoint from the guy who has probably repaired more than anyone on earth.   -Robert

 

 

I’m betting that 99% gear ups are at engine idle power, so limited abuse of which the prop takes most of it.A few years back there was a video of a twin engine plane landing with gear up and then go full power and flying back home.

Found it:

 https://youtu.be/sgdSflSCTQM

Tom

 

 

[Frank B.]

Based on my experience Lycoming crankshafts will bend because of a prop strike and you can detect that bend using a dial indicator.

Continental crankshafts will crack or break off at the flange. Dye penetrant / NDI will find cracks if they exist 

SB’s are just that, service bulletins and NOT AD,s. It is my understanding that SB’s are not mandatory compliance for part 91 operations.

Poll the members of this forum and see how many of their planes have had a prop strike and also see how many of those who have had prop strikes are flying around behind an engine that only had a dial indicator check or a flange dye penetrant test.

While there may have been failures after prop strikes even though they were run out with a dial indicator or had a flange dye penetrant test I am personally now aware of any.

Having owned multiple Mooney’s since 1987 that had prop strike history in their past I have never felt uncomfortable flying them even thought they never had the complete SB’s complied with.

Disclaimer: I am only a private pilot and NOT an AP Mech or IA.

[Steve W]

1 hour ago, David Lloyd said:

Once the case is split for the inspection the shop will find other things to replace that had nothing to do with the prop strike.  A little corrosion on the cam, a spalled lifter, etc. the customer will be on the hook for.

 

And that's how my prop strike on a 1200 hour engine became a full overhaul. (Well, not corrosion, but other items)

 

[steingar]

I still feel awful about this, but will post to assist my fellow Mooney pilots.  Please be gentle.  When I struck my prop the engine was at idle.  Indeed, that was my problem, a little squirt of power would have saved the situation.  The crank shaft was destroyed and required replacement.

 

I wouldn't fly behind anything that suffered a prop strike and was not appropriately addressed.  I cannot even fathom why someone wouldn't do so, since the insurance will happily pay for it. Better to pay for the engine teardown than the funeral of the pilot, I guess.

[Sixstring2k]

3 hours ago, carusoam said:

What part of the crank can crack and break, is it visible?

Kind of like looking for broken bones without an X-ray machine... so...

Yes and yes... (in reverse order)

1) Yes, somebody mangled the prop on one of my planes... tear down would have revealed nothing...proceeded to the next step anyways...

2) Yes, there is a sad story that goes with losing a prop... props departing airplanes have terrible side effects... a weight and balance issue immediately occurs, and may be very difficult or impossible to trim out... while in Land Now mode...

 

Rules have changed recently, defining what a prop strike is and how the inspection needs to be carried out...

The rules were changed based on actual data analysis...

The old procedure for using a micrometer to measure for run-out didn’t account for cracks and crack-propagation that actually occur...

 

it is easy to not buy into unknown risk...

it is tougher to spend money when the prop strike occurs on your watch...

 

.

 

When buying a used plane, You want to buy with as few risks as possible...  this is the reason NDH is important to some people...

Having unknowns can leave you with some unease...

Asking this question to your mechanic can be important... they are the person that is going to go through your logs to determine AW issues... this goes with the PPI... don’t send anything to a PPI that has a high chance of failure... that can be expensive...

Some planes are better for other people to own... some are better for first time buyers... some are in the middle...

PP thoughts only, not a mechanic...

Best regards,

-a-

What do you mean by NDH?  This is very interesting thread.

[kpaul]

38 minutes ago, Sixstring2k said:

What do you mean by NDH?  This is very interesting thread.

NDH=No Damage History

[carusoam]

The abbreviation for...

No

Dammage

History

you will see this used in for sale ads.

very meaningful to some...

kind of meaningful to others...

not too meaningful to some with aviation mechanical backgrounds... who are looking for a project...

Best regards,

-a-

[Bob_Belville]

I've had to have my IO360 torn down for prop strikes twice. Both times paid for by the insurance company. In both cases it was a good thing that the engine got disassembled. The first time the cam and lifters needed replacement, the 2nd time, less than a year later, the cam and lifters needed replacement again and the case and crank were replaced or overhauled. I can't say that the prop strike caused any engine damage. I paid for the cams/lifters as well as overhauling cylinders/pistons but I piggybacked that work on the R&R and tear down paid by insurance which also paid for new mags and vacuum pumps.

[jetdriven]

4 hours ago, Frank B. said:

Based on my experience Lycoming crankshafts will bend because of a prop strike and you can detect that bend using a dial indicator.

Continental crankshafts will crack or break off at the flange. Dye penetrant / NDI will find cracks if they exist 

SB’s are just that, service bulletins and NOT AD,s. It is my understanding that SB’s are not mandatory compliance for part 91 operations.

Poll the members of this forum and see how many of their planes have had a prop strike and also see how many of those who have had prop strikes are flying around behind an engine that only had a dial indicator check or a flange dye penetrant test.

While there may have been failures after prop strikes even though they were run out with a dial indicator or had a flange dye penetrant test I am personally now aware of any.

Having owned multiple Mooney’s since 1987 that had prop strike history in their past I have never felt uncomfortable flying them even thought they never had the complete SB’s complied with.

Disclaimer: I am only a private pilot and NOT an AP Mech or IA.

How do you detect cracks in the intersection of the crank throw  and the rod journal or main journal?  These are caused by torsional overstress from prop strikes.  also what about the counterweight damage or the hanger pins getting sheared  from counterweights ? You can’t dye pen that or inspect it. 

Edited January 4, 2019 by jetdriven

[Guest]

6 hours ago, Arthur said:

I am aware of TC SB 96-11A and I have decided not to purchase  3 planes that had strikes and the engines were not torn down. I am also aware of a company that sells planes after a prop strike that clocks the prop and dye tests the parts of the engine that they can see with a scope.  I am not trying to make this about who does what. The SB says, " This damage can result in catastrophic engine failure.". The question I have is this is anyone aware of a case where the result of a prop strike and non tear down procedure was used to return the aircraft resulted in this failure? Or is this the type of statement that was generated due to liability concerns.

Secondly has anyone had their engine torn down and replaced in service without any changes to the engine caused by the Prop Strike or is some hidden damage discovered and parts replaced?

Prop Strike - Copy.pdf

Lycoming crankshafts tend to be tougher than Continental cranks and as a result are more prone to cracking. We had a Navion owner nearby who had a prop strike, replaced the prop dialed the crank and flew on happily until the crank failed leading to a double fatality.  Another local plane with a Continental suffered a prop strike when conventional wisdom was dial the crank and fly on, it to broke on take off.  He made a 180, landed down wind and survived.

The owners of the planes you declined got bad advise in not doing the job correctly, you are right to decline them, unless you can buy them with enough room to replace the engine with a factory overhaul which has no core defect penalty.

Clarence

[Frank B.]

Just now, jetdriven said:

How do you detect cracks in the intersection of the crank throw  and the rod journal or main journal?  These are caused by torsional overstress from prop strikes. You can’t dye pen that or inspect it. 

There can always ... obviously, be an exception, but this is so far out of the norm. If it was typical there would be an AD concerning tear down and inspection vs a SB. Again, I would love to see a poll of members who are flying behind prop strike engines and have no concerns. 

[0TreeLemur]

5 hours ago, ArtVandelay said:

Found it:

https://youtu.be/sgdSflSCTQM

Tom

 

 

I cannot find the NTSB after-action report for this one.  I found an interview with the then 85-year Aerostar superstar that required a shovel to believe on Youtube.  Incredulous- I'd like to see if maybe my B.S. detector is flawed and the PIC was actually telling the truth about the chain of events.... 

[jaylw314]

My own aircraft had some kind of gear-down prop strike 20 years ago.  The logs show the engine inspected per AD and a new prop installed.  There was no indication or record I could find of anything in the crankcase being replaced, and it flew for another 10+ years before the rebuilt engine was installed. 

[carusoam]

59 minutes ago, Frank B. said:

There can always ... obviously, be an exception, but this is so far out of the norm. If it was typical there would be an AD concerning tear down and inspection vs a SB. Again, I would love to see a poll of members who are flying behind prop strike engines and have no concerns. 

I would love to let this one go...

You have people with experience saying no inspection=Serious risk of people dying...

engine manufacturers have given guidance on how to properly handle prop strikes...

Yes, of course some prop strikes don’t lead to any further damage...

What are you going to get from a poll that says some people are flying without following proper guidance?

There are always going to be people that are unable to follow good guidance, and are willing to take on risk...

Or are you looking for the number of people that tear down an engine to find nothing?

What are you looking to find out?

Just Wondering...

-a-

 

[jetdriven]

 

I think the majority of prop strikes cause no crank damage. But how do you know?  You now have an unknown quantity.  A good friend of mine has a lycoming engine shut down at night. She crashed on a city street. The crank gear came loose. Suspected a previous prop strike unreported. 

Insurance companies never hesitate to pay for a TDI on an insured plane. If the owner didn’t do it, ask why?  Did they not have insurance or did they pocket the money?  Neither owner I would trust buying from and flying my family in it. 

Edited January 5, 2019 by jetdriven

[Bolter]

8 hours ago, Arthur said:

I am aware of TC SB 96-11A and I have decided not to purchase  3 planes that had strikes and the engines were not torn down. I am also aware of a company that sells planes after a prop strike that clocks the prop and dye tests the parts of the engine that they can see with a scope.  I am not trying to make this about who does what. The SB says, " This damage can result in catastrophic engine failure.". The question I have is this is anyone aware of a case where the result of a prop strike and non tear down procedure was used to return the aircraft resulted in this failure? Or is this the type of statement that was generated due to liability concerns.

Secondly has anyone had their engine torn down and replaced in service without any changes to the engine caused by the Prop Strike or is some hidden damage discovered and parts replaced?

Prop Strike - Copy.pdf

Specific example of prop strike leading to eventual failure.  Cracks take time to propogate.  This is why I think a ferry flight is safe, but the engine/crank are still a high risk to ignore for the long term.  

NTSB Identification: ERA10LA175

14 CFR Part 91: General Aviation

Accident occurred Monday, March 15, 2010 in Hilton Head Island, SC

Probable Cause Approval Date: 06/27/2011

Aircraft: SMITH EDWARD I LANCAIR IV-P, registration: N9JE

Injuries: 1 Fatal, 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

**This report was modified on 8/8/13. Please see the docket for this accident to view the original report.**

The pilot stated that while in cruise flight he observed the instrument panel begin to vibrate heavily and oil begin to cover the wind screen before hearing a loud "bang." The engine then lost power as oil continued to obscure the wind screen. The pilot had no forward visibility and could not maintain the airplane's altitude. He elected to make an emergency landing on a nearby beach and during the landing the airplane struck and killed a pedestrian. Examination of the airplane revealed that the propeller assembly separated from the crankshaft and was missing. The propeller assembly and propeller flange were not recovered. An examination by the NTSB Materials Laboratory of the crankshaft revealed that the aft face of the fracture contained crack arrest marks. The fracture of the crankshaft was caused by multiple-origin fatigue cracks that emanated at the aft relief radius for the propeller flange. The records for this engine and airplane do not show an entry of a propeller strike. However, multiple-origin fatigue cracks that extend nearly 50% around the circumference of the aft relief radius for the propeller flange suggest that the propeller had struck an object prior to fracture of the crankshaft. In the absence of material anomalies, the fatigue cracking appears likely to have been caused by external impact stress, such as a propeller strike.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

• A loss of engine power due to the failure of the crankshaft as a result of a previous propeller strike.

[Jim F]

Back in the day I did a tear down on a O-360 from a 172RG that came in for an overhaul cut to a oil leak from the nose seal that they could not fix.  After the tear down I found a crack on the crank ~240 degrees around the crank.  It would not have been long before the prop popped off.  Think about it. 

Jim

[jackn]

[bill98]

9 minutes ago, jackn said:

Why does Beechtalk have a picture of a Piper Arrow posted?thought those guys only cared about planes with V Tails

[Sixstring2k]

3 hours ago, kpaul said:

NDH=No Damage History

Thank you.