Prop Strike?

[Diana]

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?

 

[bbchien]

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?

Usually depends if there was an engine stoppage or not. For continentals, they recommend pulling the crank but they do not require it, provided there has been no stoppage.

Gives me the creeps!

 

[poadeleted20]

The engine manufacturers provide guidelines, but there are no FAA regs on the subject, other than those which make the guidelines mandatory for 135 and 121 operators. For Lycoming engines, see Lycoming Service Letter L163C, an unofficial copy of which you can find at http://www.prime-mover.org/Aviation/Bulletins/sl163.html and an official copy of which you can get faxed to you free by calling Lycoming at 570-323-6181 from 8 AM to 5 PM (Eastern Time) Monday – Friday.

Generally speaking, a teardown is recommended if any part of the prop came off or if the engine was stopped by whatever it hit ("sudden stoppage"). If the engine kept running and the prop is still in one piece, a teardown is more dependent on the judgement of the mechanic that examines it. Usually they'll check the prop track, and if it's still true, will not tear down the engine. Keep in mind that in most cases, the teardown is covered by insurance if you have an accidental prop strike, and the insurance company would rather pay for a precautionary teardown than the results of a later engine failure.

 

[wsuffa]

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?

Diana, the FAA issues a revised AD for certain Lycoming engines and prop strikes last year.

You can read that AD here (you'll have to scroll and read through the document to see it):

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/6139b2f6771070b186256ea60059a0a4/$FILE/SM2004-11.pdf

I didn't search for Continental.

Good luck.

bill

 

[Diana]

Diana, the FAA issues a revised AD for certain Lycoming engines and prop strikes last year.

You can read that AD here (you'll have to scroll and read through the document to see it):

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/6139b2f6771070b186256ea60059a0a4/$FILE/SM2004-11.pdf

I didn't search for Continental.

Good luck.

bill

Thanks Bill, Bruce, and Ron.

It was a Lycoming.

 

[poadeleted20]

Based on the AD definition of "prop strike" in paragraph (i)(1), if the prop had to be sent off for repair, it sounds like AD compliance is dictated.

 

[Skyport]

Diana-

Lycoming now considers anything that strikes the prop AND causes a drop in RPM's a "prop strike", that specifically includes tall grass and water.............

The more restrictive definition is due to increased concern for the integrity of the drive gear and pin on the rear of the crankshaft.

Tom-

 

[Diana]

Diana-

Lycoming now considers anything that strikes the prop AND causes a drop in RPM's a "prop strike", that specifically includes tall grass and water.............

Tom-

Thanks Tom. I wonder how much tall grass? I guess enough to cause a drop in RPM?

We had somebody taxi into our soybeans here one time, but they had throttled back by the time they got into the beans.

 

[Ed Guthrie]

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?

Lycoming? If so, yes, technically, it is a prop strike and requires a tear-down. I don't know much about Continentals.

 

[Tom-D]

The engine manufacturers provide guidelines, but there are no FAA regs on the subject, other than those which make the guidelines mandatory for 135 and 121 operators. For Lycoming engines, see Lycoming Service Letter L163C, an unofficial copy of which you can find at http://www.prime-mover.org/Aviation/Bulletins/sl163.html and an official copy of which you can get faxed to you free by calling Lycoming at 570-323-6181 from 8 AM to 5 PM (Eastern Time) Monday – Friday.

Generally speaking, a teardown is recommended if any part of the prop came off or if the engine was stopped by whatever it hit ("sudden stoppage"). If the engine kept running and the prop is still in one piece, a teardown is more dependent on the judgement of the mechanic that examines it. Usually they'll check the prop track, and if it's still true, will not tear down the engine. Keep in mind that in most cases, the teardown is covered by insurance if you have an accidental prop strike, and the insurance company would rather pay for a precautionary teardown than the results of a later engine failure.

Please read:

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

(b) This AD supersedes AD 91-14-22.

Applicability

(c) This AD applies to Lycoming Engines (formerly Textron Lycoming), direct-drive reciprocating engines (except O-145, O-320H, O-360E, LO-360E, LTO-360E, 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 has experienced a propeller strike as defined in paragraphs (i) and (j) of this AD, unless already done.

(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.

 

[Skyport]

Diana-

So was it a nick from a rock that was thrown up, or a stone that was in dirt that the prop impacted? If the prop hit the dirt it's a prop strike, if the prop needs to be sent to a prop shop it's most assuredly a prop strike.

As far as tall grass or water we must define "sudden drop in RPM".....................

Tom-

 

[Tom-D]

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

With this in mind, and reading this--

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?


I would consider blending the blade within limits and leave it attached to the engine. Many A&Ps will not touch a prop, but in many cases they could save their customers a lot of bucks. using the guidance from AC 43,13.2B,


Continental does not Have an AD for prop strike, They leave it to the mechanic in the field.

 

[Diana]

So was it a nick from a rock that was thrown up, or a stone that was in dirt that the prop impacted? If the prop hit the dirt it's a prop strike, if the prop needs to be sent to a prop shop it's most assuredly a prop strike.

It seems that the prop went into the dirt. I think they are planning to ship the prop off.

As far as tall grass or water we must define "sudden drop in RPM".....................
Tom-

Ok, thanks Tom.

In this case it's not clear yet as to whether there was a drop in RPM at the time of the prop strike.

 

[Diana]

I would consider blending the blade within limits and leave it attached to the engine. Many A&Ps will not touch a prop, but in many cases they could save their customers a lot of bucks. using the guidance from AC 43,13.2B,

That was actually discussed. The owner opted to ship it off.

Wonder how much it costs to overhaul a prop (this is a Skyhawk)?

Continental does not Have an AD for prop strike, They leave it to the mechanic in the field.

I wonder why Continental has a different policy in this matter?

 

[Ed Guthrie]

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

With this in mind, and reading this--

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?


I would consider blending the blade within limits and leave it attached to the engine. Many A&Ps will not touch a prop, but in many cases they could save their customers a lot of bucks. using the guidance from AC 43,13.2B,


Continental does not Have an AD for prop strike, They leave it to the mechanic in the field.

Face with the situation at hand, a mechanic looking at a Lycoming engine and wishing to use judgement would suggest to the customer that the prop has reached overhaul calendar time/time in operation (whichever is appropriate).

 

[Ed Guthrie]

That was actually discussed. The owner opted to ship it off.

Wonder how much it costs to overhaul a prop (this is a Skyhawk)?


I wonder why Continental has a different policy in this matter?

Different corporate lawyer.

 

[Tom-D]

That was actually discussed. The owner opted to ship it off.

Wonder how much it costs to overhaul a prop (this is a Skyhawk)?


I wonder why Continental has a different policy in this matter?

"Wonder how much it costs to overhaul a prop (this is a Skyhawk)?"

It varies $400 and up. But the Prop is the lessor worry now. When the prop was removed for repair the AD kicks in. TheEngine is required to comply with the AD, It is not required to tear the complete engine down, but the accessory case must be removed and the AD complied with.(manditory replcement of the gear and dowel pin)

The other consideration is resale value. (Prop strike logged, no overhaul.) Tell your friend to be carefull fo what the Mechanic places in their log book. the pen could do more damaage than the ding in the prop.

 

[Skyport]

Diana-

Note that the sudden drop in RPM requirement is ONLY an issue when the prop strikes a "yielding" medium such as water or tall grass, after striking dirt it IS a prop strike, no questions asked.

I think the difference is because Lycoming has confirmed that the drive gear and dowel are known weak points after a prop strike. Proper installation AND torque is an important segment in the Service School. There have been confirmed cases of the gear being installed correctly, torqued correctly, but an overzealous mechanic slopped grease on the gear before installation, later after the grease cooked out the torque value was lost because the grease had left a void, and the dowel snapped.................and the engine failed.

Tom-

 

[wsuffa]

The other consideration is resale value. (Prop strike logged, no overhaul.) Tell your friend to be carefull fo what the Mechanic places in their log book. the pen could do more damaage than the ding in the prop.

One of the Lycoming Mandatory SB's requires that the prop strike be logged in the book regardless. I do not recall if that SB is incorporated in the AD.

 

[Stache]

There is a FAR that covers propeller strikes Section 43.13(a) follow the current manufacture maintenance manual and 43.13(b) the propeller has to be at least equal to its original or properly altered condition.



What all this means if you slow the propeller RPM in one revolution it is considered a propeller strike reference AC 43.13-1b and manufacturers maintenance manual or service instructions. Continental says split the case halves and perform an inspection. Lycoming says to remove the accessory cover and inspect the gears/bolts in accordance with service instructions and AD’s.



No matter what engine you have always check the manufacture maintenance manual to see what they want done to their engine. As for propeller all an A&P can do is remove small nick and stuff as long as the propeller is still with in the service limits length, cord and damage limits.



If you have a constant-speed propeller I would recommend having it removed and inspected by a propeller Repair Station. There are things that break inside the hubs that cannot be repaired or found by you’re A&P. This will always mean a complete NDI inspection.



Stache

 

[sere]

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?

If it was in Alaska they don't even know there is such a term. LOL

 

[Henning]

What are your thoughts? Somebody I know had a prop strike with a nick in the prop (it might have hit a rock in the soft dirt). The prop will be sent off. Are there regs or guidelines about the need to tear the engine down in a case like this?

The technical answer, they have to follow the manufacturers guidelines for a propstrike AT A MINIMUM.

To figure the actual amount of work Above and Beyond that you do, requires some figuring, and it's dependant on the shock load sent through the rotating and reciprocating mass. If it was a choke through some dirt or sand or grass and it just kinda did a lawnmower into the deep grass thing, I'm not going to worry about much more than what is stated for the manual. OTOH if that prop hits something solid for a good KERCHUNK or a dead stop, I'm doing a major. The shock loads involved are staggaring even on an O-200, and that shock transmitts itself through everything rotating and reciprocating in that engine. Metals, especially castings, do not react well to shock, and small cracks form, nothing you catch looking at it, sometimes even hidden like in rod bolts, rods are designed to handle high loads in power mode, but are very weak in the decelleration mode. The end damages of a strike may not manifest themselves for quite a few hours, do you want to risk where it is they may manifest themselves. It is very easy to get an overhaul out of the insurance company on a prop strike.

 

[gismo]

It seems that the prop went into the dirt. I think they are planning to ship the prop off.


Ok, thanks Tom.

In this case it's not clear yet as to whether there was a drop in RPM at the time of the prop strike.

If it went into the dirt, I'd expect a pretty noticable drop in RPM. If you just sucked up a rock, chances are you wouldn't see any drop at all.

 

[Tom-D]

One of the Lycoming Mandatory SB's requires that the prop strike be logged in the book regardless. I do not recall if that SB is incorporated in the AD.

Service bulletins are not mandatory in part 91 BUT that AD is.

 

[Tom-D]

If it went into the dirt, I'd expect a pretty noticable drop in RPM. If you just sucked up a rock, chances are you wouldn't see any drop at all.

That's the whole thing, WE don't know how badly this prop was damaged. WE don't know if it meets criteria for a strike or not.

BUT WE do know it was removed for repair due to damage while running, that kicks in the Lycoming AD.

This engine MUST HAVE THE AD COMPLIED WITH.

 

[Diana]

Thanks everybody for your input. I appreciate your sharing your knowledge. It's always good to learn from you guys; you're a wonderful collective resource.

 

[Henning]

That's the whole thing, WE don't know how badly this prop was damaged. WE don't know if it meets criteria for a strike or not.

BUT WE do know it was removed for repair due to damage while running, that kicks in the Lycoming AD.

This engine MUST HAVE THE AD COMPLIED WITH.

Yep, plain and simple, otherwise from now on they'll be flying an unairworthy aircraft. The AD may suck in the opinions of some, but the AD is there, and unless someone does the prop repair without a papertrail, you are going to have problems.

 

[wsuffa]

Service bulletins are not mandatory in part 91 BUT that AD is.

Agree, but...

The FAA sometimes incorporates Service Bulletins into the AD. As always, you have to read the AD to be sure.

 

[Tom-D]

Agree, but...

The FAA sometimes incorporates Service Bulletins into the AD. As always, you have to read the AD to be sure.

Yes there is an embedded SB in AD 2004-10-14

it reads

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.