Times have changed in aviation maintenance

[cliffy]

Here's a follow on to another thread about the FAA and a/c maintenance,

 

Years ago we didn't have too much concern with prop strikes. We measured the prop flange for run out (wobble) to determine if it was bent then bolted a new prop on and away we'd go. 

 

Now it's a different story. 

 

We have a Cessna 206 in our local hangar that had a hard landing and I mean hard. The tail cone was hit. the tail tie down ring folded back and the rear bulkhead bent. The nose gear was totaled but no firewall damage, the nose tire and wheel and fairing were trashed.AND one blade of the 3 blade prop touched the concrete causing the tip to show a gouge maybe 3/4 of an inch long and maybe less than 1/8 inch deep with the trailing edge of the tip bent aft about 4 degrees from true in a triangular shape about 1/2 inch in size. 

 

Needless to say the owner only wants the nose gear fixed and to file the prop tip. BUT that can't be done today!

 

With the way the prop strike AD reads today the engine and prop have to be torn down. Not even a ferry permit is allowed!

Going through tall grass that slows the prop down is considered applicable for tear down by this AD.

 

No shop or mechanic on our airport is willing to file the blade with good reason- LIABILITY-both for an accident afterward if something is wrong inside the engine and from the FAA for doing it against the AD. 

 

Oh I forgot to add, this is a brand new 206 with a full Garmin glass cockpit AND this is the second hard landing the owner has given it. The first was 5 months previous and $100,000 in cost for new wings! How's that for adding future liability to the issue!

[Bob_Belville]

Having gone through a prop strike recently, I am puzzled that an owner would not WANT the repairs done right. My insurance adjuster practically insisted on it and covered the cost w/o any deductible. In my case there was no effect on my renewal premium. I did lose the use of the plane for almost 3 months but happily it was in the dead of winter.  

[marks]

Cliffy,  do you really think it's a good idea to make the repair of this 206 nice and cheap so that this pilot can fly again quickly and take up passengers as well?  -  I don't think so.

[TonyPynes]

My experience with prop strikes mirror what was said here.

 

I hit a pot hole a few years ago...barely touched the surface with tips of blades-could have been filed easily....insurance company insisted...tear it down....no issues found...but I still felt better. Perhaps just inexperience on my part but i would insist again.

 

Then last year, gear up...hard hit of blades - curled and broke pieces off....(softest landing ever) mechanic who rebuilt plane said the crankshaft had a crack in it.

 

Hopefully I am done with props hitting hard objects. As I look for my next Mooney....J or K I would never buy one that had a prop strike without a teardown and inspection...I would need to see the reports and prob talk to the shop. Most on this board are more experienced than me and more knowledgeable...I am certain. In the past I understand it was common for glancing blows to be filed and sent back to work...like OP said times have changed.

[Marauder]

Having gone through a prop strike recently, I am puzzled that an owner would not WANT the repairs done right. My insurance adjuster practically insisted on it and covered the cost w/o any deductible. In my case there was no effect on my renewal premium. I did lose the use of the plane for almost 3 months but happily it was in the dead of winter.

Probably because this would be his second claim. The first $100k claim and this one would probably equal uninsurable.

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[Bob_Belville]

Probably because this would be his second claim. The first $100k claim and this one would probably equal uninsurable.

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Weak reasoning, IMNSHO. He should get the plane properly repaired then sell it and find another hobby before someone gets hurt. Cold? 

[Marauder]

Weak reasoning, IMNSHO. He should get the plane properly repaired then sell it and find another hobby before someone gets hurt. Cold?

I didn't say it was good reasoning, just that is probably what is going through his head. He just stuck his insurance with a $100k bill 5 months ago and he is going to do it again. You and I have been around GA long enough to know there are some people who should never be allowed to fly. But somehow, they manage to get their license. Sent using Tapatalk

[chrisk]

If money were no object, it would clearly be better to have the engine torn down and inspected after a prop strike.     And as long as your tearing it down to inspect it, maybe we should require an overhaul!     Perhaps, the question should be:  Does a tear down inspection after a prop strike make a SIGNIFICANT safety difference? 

 

If the cash was coming out of your pocket, would you pay for a tear down for any prop strike?  For an engine stoppage, I would.  On the other hand if I hit a blade of grass or a small bird I would not.  And if you don't think the engine slows down for just a single blade of grass, think again.  It's just a small, but measurable,  amount.   

[MooneyBob]

Bob B,

 

how did the prop strike happen? I just want to learn to avoid that.  I think you have mentioned somewhere else it was a pot hole? How big is the pot hole to cause the prop strike? High taxiing speed?

 

Thanks

[MooneyBob]

TonyP,

 

same question for you. How big/deep was the pot hole and taxiing speed that caused the strike?

 

Thanks

[flyboy0681]

The only attribute that I don't like about the Mooney is the 10 inch clearance between the tip of the prop and the concrete. 

[Bob_Belville]

Here's the thread, several pages, concerning the prop strike I had last fall. The "pot hole" was small, there are pics, it pretty unlucky event. I was moving slowly across a paved ramp. But... it turned out OK. The engine tear down revealed no damage to the crank or case but exposed corrosion to the cam shaft. I got most of a major o'haul for the cost of the cam and lifter parts since there was no extra labor. Saved me thousands. The engine has 700 hours on a factory reman. It was always hangered but the previous owner had not flown it regularly.

 

http://mooneyspace.com/topic/10273-prop-strike-today-october-8-2013/?hl=%2Bprop+%2Bstrike

[Joe Zuffoletto]

That 206 owner needs to leave the flying to someone else. Seriously.

 

Or at least the landings!

[MooneyBob]

Here's the thread, several pages, concerning the prop strike I had last fall. The "pot hole" was small, there are pics, it pretty unlucky event. I was moving slowly across a paved ramp. But... it turned out OK. The engine tear down revealed no damage to the crank or case but exposed corrosion to the cam shaft. I got most of a major o'haul for the cost of the cam and lifter parts since there was no extra labor. Saved me thousands. The engine has 700 hours on a factory reman. It was always hangered but the previous owner had not flown it regularly.

 

http://mooneyspace.com/topic/10273-prop-strike-today-october-8-2013/?hl=%2Bprop+%2Bstrike

Thanks Bob

[cliffy]

Marks, I hope I never inferred that the owner should do anything but a tear down. IT IS MANDATORY BY AD PERIOD! That was my point. 

It makes no difference what the prop hits, if it slows down or shows injury the engine MUST be torn down and no filing of gouge marks is allowed on the prop.

If the prop sucks a rock up and dings the blade that is allowable damage to repair. No filing of the tips of the blades is allowed per AD.  

Marauder has it correct- he doesn't want to report it to his insurance because they would cancel him and he doesn't want to spend the money for a tear down. 

Yes, some people should do other things rather than fly airplanes. Yes, I too have about 100 hrs in 206s. Very easy to land. 

[Guest]

The AD 2004-10-14, does not require a complete tear down the way I read it. It says that you must remove and inspect the crankshaft, the alignment dowel, the counter bore for the gear, the retaining bolt, and the gear all in accordance with Lycoming s/b 475C. Common industry practice is a complete dis assembly for inspection.

The AD is to general in its scope, if the engine experiences a real sudden stop which damages the prop beyond repair it makes sense to do a complete inspection. If the prop touches you hangar door, or your tow bar while cranking a lesser inspection should be sufficient, but that's not how it's written.

Clarence

[Bob_Belville]

The AD 2004-10-14, does not require a complete tear down the way I read it. It says that you must remove and inspect the crankshaft, the alignment dowel, the counter bore for the gear, the retaining bolt, and the gear all in accordance with Lycoming s/b 475C. Common industry practice is a complete dis assembly for inspection.

The AD is to general in its scope, if the engine experiences a real sudden stop which damages the prop beyond repair it makes sense to do a complete inspection. If the prop touches you hangar door, or your tow bar while cranking a lesser inspection should be sufficient, but that's not how it's written.

Clarence

We thoroughly went around on this when the tip of the prop "grazed" the tarmac in October while taxiing @ 1500 rpm or less. The blades turned out to be repairable so the prop was overhauled, not replaced. The crank shaft and the crankcase had to be sent to shops in OK to be tested and checked. Both passed muster. That of course required engine removal and disassembly. The mags had to be replaced (overhauled). The cylinders were inspected and were in spec so only new rings were included. The camshaft and lifters were replaced, not due to strike damage but corrosion, so I paid for those parts. (The engine shop was not happy with the clearance on 2 of the lifters. Both the bore and the lifter dims were in spec but the lifters were near the min and the bore was near the max so he bored the case and got the clearance tighter. He has had some issues with low oil pressure in the past due to what he considers sloppy specs on lifters.)

 

The A&P/IA, the engine shop, and the insurance company were all very experienced with prop strikes and were in complete agreement as to what had to be done. It certainly suited me.  

[cliffy]

M20Doc- How do you remove the crankshaft without completely tearing down the engine?

 

Not criticizing, just at a loss to understand what you are saying on how to do it. 

 

The crankcase has to be split open to remove the crankshaft for inspection. That essentially is a complete tear down. 

[Hector]

TonyP,

same question for you. How big/deep was the pot hole and taxiing speed that caused the strike?

Thanks

MooneyBob, one advantage of your three bladed prop is that is has more ground clearance than the two bladed props.

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[scottfromiowa]

MooneyBob, one advantage of your three bladed prop is that is has more ground clearance than the two bladed props.

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NOPE. Rehash. Same clearance. I had the ruler to check. I lost that bet.

[Hector]

NOPE. Rehash. Same clearance. I had the ruler to check. I lost that bet.

Wow, stand corrected then! I'm surprised. Thought the blades would be a little shorter given your swinging three of them.

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[Bob_Belville]

MooneyBob, one advantage of your three bladed prop is that is has more ground clearance than the two bladed props.

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Are you sure about that? My scimitar HC-C2YR-1BFP/F7497 is 74" and weighs 62-64# according to the link below.

The Hartzell HC-C3YR-1RF/F7282 3-bladed prop is also 74" and weighs 71#.

Both props can be reduced in diameter, The scimitar to 72.5, the 3 blade to 73.

www.hartzellprop.com/top_prop_details.php?id=104

   

Perhaps other 3 blade props can be smaller... 

[Hector]

Are you sure about that? My scimitar HC-C2YR-1BFP/F7497 is 74" and weighs 62-64# according to the link below.

The Hartzell HC-C3YR-1RF/F7282 3-bladed prop is also 74" and weighs 71#.

Both props can be reduced in diameter, The scimitar to 72.5, the 3 blade to 73.

www.hartzellprop.com/top_prop_details.php?id=104

Perhaps other 3 blade props can be smaller...

Yeap, Scott beat you to the punch Bob. For some reason I thought the approved three bladed props for the Mooney were a little shorter than the two bladed props

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[Bob_Belville]

Yeap, Scott beat you to the punch Bob. For some reason I thought the approved three bladed props for the Mooney were a little shorter than the two bladed props

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Yeah but I provided actual data. 

[Guest]

No critisism taken, I assume that we are talking about the same AD?

The crankshaft need not be removed, if you pull the accessory cover you can satisfy requirements for the AD. Paragraph (f) covers it. Removal would only be required if it did not pass the inspection requirements.

Clarence

2004-10-14 Lycoming Engines (formerly Textron Lycoming): Amendment 39-13644. Docket No. 89-ANE-10-AD. Supersedes AD 91-14-22, Amendment 39-6916.

Effective Date

(a) This AD becomes effective June 25, 2004.

Affected ADs

( This AD supersedes AD 91-14-22.

Applicability

© This AD applies to Lycoming Engines (formerly Textron Lycoming), direct-drive reciprocating engines (except O-145, O-320-H, O-360-E, LO-360-E, LTO-360-E, TO-360-E, O-435, and TIO-541 series engines).

Unsafe Condition

(d) This AD results from a change to the definition of a propeller strike or sudden stoppage. The actions specified in this AD are intended to prevent loosening or failure of the crankshaft gear retaining bolt, which may cause sudden engine failure.

Compliance

(e) Compliance with this AD is required as indicated before further flight if the engine experiences a propeller strike after the effective date of this AD, as defined in paragraphs (i) and (j) of this AD.

(f) Inspect, and if necessary repair, the crankshaft counter bored recess, the alignment dowel, the bolt hole threads, and the crankshaft gear for wear, galling, corrosion, and fretting in accordance with steps 1 through 5 of Lycoming Mandatory Service Bulletin (MSB) No. 475C, dated January 30, 2003.

(g) Remove the existing gear retaining bolt and lockplate from service, and install a new bolt and lockplate, in accordance with steps 6 and 7 of Lycoming MSB No. 475C, dated January 30, 2003.

Prohibition of Retaining Bolt and Lockplate

(h) Do not install the gear retaining bolt and lockplate that were removed in paragraph (g) of this AD, into any engine.

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.

(j) The preceding definitions include situations where an aircraft is stationary and the landing gear collapses causing one or more blades to be substantially bent, or where a hanger door (or other object) strikes the propeller blade. These cases should be handled as sudden stoppages because of potentially severe side loading on the crankshaft flange, front bearing, and seal.

Alternative Methods of Compliance

(k) The Manager, New York Aircraft Certification Office, has the authority to approve alternative methods of compliance for this AD if requested using the procedures found in 14 CFR 39.19.

Material Incorporated by Reference

(l) You must use Lycoming MSB No. 475C, dated January 30, 2003, to perform the inspections and repairs required by this AD. The Director of the Federal Register approved the incorporation by reference of this service bulletin in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. You can get a copy from Lycoming Engines, 652 Oliver Street, Williamsport, PA 17701, U.S.A; telephone (570) 323-6181; fax (570) 327-7101. You can review copies at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html .

Related Information

(m) None.

Issued in Burlington, Massachusetts, on May 12, 2004.

Peter A. White,

Acting Manager, Engine and Propeller Directorate,

Aircraft Certification Service.

[FR Doc. 04-11406 Filed 5-20-04; 8:45 am]

BILLING CODE 4910-13-P

CORRECTION: [Federal Register: June 28, 2004 (Volume 69, Number 123); Page 36007;

www.access.gpo.gov/su_docs/aces/aces140.html] Go to the attached "pdf" for full correction text. This copy reflects the correction.