Bent prop:Dial vs Teardown

[Jerry Cochran]

Thanks,
That's from one of the best authorities for sure.. Gotta love the net and VAF.

Jerry

[breister]

Originally Posted by Danger Will Robinson

I found this page.

http://www.mattituck.com/articles/ss.htm

It's Matitucks opinion on this.

Wow - that's more generous than I would have thought. So, unless the prop stops in "one revolution or less" the FAA does not consider it "sudden stoppage."

I can envisage circumstances where the engine rotates several times, striking the prop "a little" each time but not stopping for several revolutions.

Makes you scared to think of what might be out there on the used market...

[Danger Will Robinson]

Engine Sudden Stoppage

What is a prop strike? Is it a sudden engine stoppage regardless of the cause? Is it an occasion when a prop blade strikes a foreign object and the engine continues to run? Is it hitting a rock or other loose object with a prop blade while operating on a runway or taxiway? Is it when something or someone impacts a prop blade when the engine isn't running?

The only pertinent F.A.A. definition that I have been able to find is in Advisory Circular 43.13-1A. It defines a sudden engine stoppage as; stopping an engine in one revolution or less for any reason, be it from propeller impact or from an engine failure of some sort. Both Continental and Lycoming engine manufacturer's have service literature that explains the desired course of action after accidental propeller damage. They also define what their interpretation of a propeller strike is in that literature.

T.C.M.'s Service Bulletin 96-11, in a nutshell, says that if a propeller must be removed from the aircraft to be repaired following a propeller blade impact of any sort or if the engine physically lost R.P.M.'s from the incident, then the engine has experienced a propeller strike and it should be removed from service and completely disassembled and thoroughly inspected for damage from the incident.

Textron Lycoming, in their Service Bulletin 533A, takes the approach that the safest procedure is to take the engine apart for inspection following any incident involving propeller blade damage. However, they have the caveat that the inspecting mechanic may override that position and return the engine to service without disassembly and inspection if he feels that it is the prudent and responsible thing to do.

Textron Lycoming has also published Service Bulletin 475C which requires, in the event that the engine has experienced a propeller strike, inspection and possible rework of the accessory gear train as well as the rear of the engine's crankshaft. Compliance with this service bulletin is mandatory in the eyes of the F.A.A. by A.D. note 2004-10-14, if and only if, the engine has experienced a propeller strike as defined in the context of the A.D.. It should be noted that to comply with A.D. note 2004-10-14, the engine does not need to be completely disassembled and that access to the accessory gear train can be accomplished, in most cases, with the engine still installed in the aircraft.

What this all boils down to is that in the case of any accidental damage to a propeller installed on a aircraft operating under Part 91 of the F.A.R.'s, it is up to the inspecting technician to determine if the engine should continue in service without total disassembly and inspection. A Textron Lycoming engine, that is being operated on a Part 91 aircraft, that had a propeller strike, must comply with A.D. note 2004-10-14 and Service Bulletin 475C at a minimum.

Teledyne Continental powered aircraft operating under Part 135 of the F.A.R.'s, that have to comply with all manufacturers service bulletins, would have to comply with Service Bulletin 96-11 requiring total disassembly and inspection after any incident that required removal of the propeller for repairs or if the engine physically lost R.P.M.'s during the incident. An aircraft, operating under the same regulations, that is powered by a Textron Lycoming engine, would have to comply with Service Bulletin 475C after a propeller strike of any kind and would also have to comply with A.D. note 2004-10-14. On these Textron Lycoming powered aircraft, it is the responsibility of the inspecting technician to determine if the engine should be removed from service for disassembly and inspection.

These are the legal requirements as I see them. There may be other additional requirements mandated by insurance policies or engine manufacturer's and or overhauler's warranties. Either may require additional inspection requirements but neither may negate the inspections required by the F.A.R.'s. Never allow an insurance adjuster to dictate the inspection requirements after an incident. Always rely on the inspecting technician, applicable service data and the F.A.R.'s to dictate how thorough an inspection is necessary to continue the engine in service.

After the extent of the inspection has been determined, it is important, as with any major repairs that are accomplished on your aircraft, to find out exactly what is included in the estimate to repair your engine following a prop strike. Are the minimum legal requirements being met? Is the engine being completely disassembled and inspected? What other services or inspections are being performed at the same time as the inspection? If the engine is being disassembled does the estimate include testing after reassembly? Are any of the engine's accessories inspected and if so to what extent? Are there any hidden costs? After finding out the answer to these questions, it's time to discuss with your insurance company what they will pay for and what they won't, before it's a big surprise after the inspection has been completed. Many insurance companies will not pay for any inspection requirements unless damage from the incident is found during that inspection. Others will pay for all costs for the inspection and for any parts needed due to the incident. Still others will only pay for the labor to do the job and will not pay for any parts.

Finding out what needs to be done and whether that agrees with what you feel should be done, who's going to do it and who is going to pay for it, should help make the experience of a prop strike as painless as possible.
by Mahlon Russell

Send your questions, to Mahlon at mrussell@continentalmotors.aero

[john.schwaner]

1. After a prop strike there is rightful concern about the airworthiness of the engine. This concern can only be answered by inspection and not by hope, prayer, or opinion.

2. Having a shop that has performed approximately 1 prop strike inspection each month for some 20 years, I still cannot tell you which prop strikes cause damage and which ones don't without an inspection. This has taught me that the preceived "severity" of the propeller strike is not a criteria for deciding which engines should be inspected and which ones need no inspection.

3. I personally didn't tear down my engine after I hit the towbar with the propeller and sent it flying across the airport. But then we did one on a Navajo that hit a plastic caution cone that had damage -

4. Engine mounts can also be damaged. That said, my opinion is based on my personal experience and others have views that conflict with mine based on their experience and judgement. I could be wrong.

I have spend many year pondering how to inspect the engine without tearing it down and I have never come up with an adequate method. Your question as to signs to look for - I don't know.

[PCHunt]

John's $0.02 is worth a lot more than 2 cents, IMHO !

[NDrv8r]

I started my project in 2009 with an IO360-A1B6 that came off of a acrosport that had a gear failure, and consequently a prop strike.

The prop flange dialed .003. The drive pin and other accessory case parts looked great. I figured I was good to go.

I built up the empenage in Nov 2009 and then I couldn't get more kit parts till march of 2010. I decided what the heck, I'll pull the steel parts and send them in. Long story short, the forward thrust flange was cracked 1/3 of the way around. Was it cracked at the same time as the prop strike? I dunno, but I'm sure glad I found out about it then rather than when I was flying.

I'm gonna have to go with the inspect it advice.

[pierre smith]

Is there any other noise-making device in your airplane more important to have going than the one in the front?

C'mon guys...tear it down!


Best,

[DEWATSON]

Thirty years ago when I was poorer than I am now (I'm still poor), I flew a Cherokee 140. I kept it tied down outside with ropes that passed through old aircraft tires for markers. The front strut on the airplane was low which put the propeller tips closer to the ground. One afternoon while parking the airplane after a flight, the propeller hit the tailwheel tiedown marker and pitched it across the airport. The engine kept running, but the impact put a small dent in the leading edge of one blade. Like I said, I was poorer then, so I had the local A & P dial the crankshaft and we pulled the propeller off for repair. When it came back, we replaced it and I flew that airplane forever before it was sold. Absolutely no problems at all.........BUT I SURE WOULDN"T DO THAT NOW...........ALWAYS TEAR IT DOWN!!!!!!!! Pierre is spot on. It isn't worth the risk. If the propeller left the airplane at 8,500 feet, you would gladly pay for a dozen teardowns not to be in the fix you would be in at that particular time.