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Prop strike/gearbox check? Questions

Y

yankee-flyer

Well Known Member
Had an incident yesterday where the prop tips touched the runway. Did NOT break props, did NOT stop engine. One tip has maybe 1/16" abraded off, the other 1/16 to 1/8". One a standard category engine this would not be a problem but I've been told that Rotax requires that the gearbox be torn down and inspected and that this requires the engine be pulled and sent to an authorized facility.

1) is this in fact the case?

2) Is there a facility closer to Ohio than Lockwood>

3) suggestions??

THANKS!!

Wayne 120241
 
yankee-flyer said:
Had an incident yesterday where the prop tips touched the runway. Did NOT break props, did NOT stop engine. One tip has maybe 1/16" abraded off, the other 1/16 to 1/8". One a standard category engine this would not be a problem but I've been told that Rotax requires that the gearbox be torn down and inspected and that this requires the engine be pulled and sent to an authorized facility.
Click to expand...

Just to clarify, this would be considered a prop strike by Lycoming as well:

A propeller strike includes (ref. SB 533B):
Any incident, whether or not the engine is operating, where repair of the propeller is necessary.
 
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Hi Yankee,
As you have described this minor brush with the prop tips this wouldn't constitue a prop strike that would need a gearbox and crankshaft inspection. Just fix your prop.
 
RV12 Prop Strike

I forwarded this thread to a friend of mine (at Lock Haven) that is familiar with Rotax engines. His comment is as follows:

The damage to the prop tips definitely requires inspection of the gearbox, but this does NOT require pulling the engine. Remove the spinner, then the prop, and then the dozen or so bolts attaching the gearbox to the crankcase (note: this unfortunately requires a special tool, but there is a shop in Dayton, Dreams Come True Aviation, that has one, and they can probably pull the gearbox for you). Takes maybe 15 minutes. Send the gearbox to LEAF, and if all checks good, remount the gearbox (using the correct Loctite sealant) replace the bolts (tightened to the specified torque), replace the prop and spinner, wait 24 hours for the Loctite to cure, and you're good to go.

H. Paul Shuch
Director of Maintenance
AvSport of Lock Haven
(A factory authorized Rotax Independent Repair Centre)
Call me of you have questions:
570-419-1229

Jim Diehl RV7A
Based at Lock Haven, Pa.
 
I know Paul and he's a nice guy. I think he may have misspoke on this one.


Scuffing 1/16" to 1/8" off the blade tip with no slowing of the engine, no shattering of the prop, no stoppage of the engine doesn't require the initiation of the prop strike protocol. There would be nothing to check. You absolutely couldn't have twisted a crankshaft, bent the prop flange, tweaked the crankshaft end out of round or have damaged the gearbox under the circumstances you described in the first post. If all you did was scuff the tips 1/16" then none of that could have possibly happen with your composite prop. If you have a Sensenich prop and send it back to Sensenich they may be able to refurbish the prop. They would have to make that determination. Those blades can be shortened.
You can tear that gearbox down, but I'll bet money they find zero if all you did was scuff 1/16" off the tips.

If anyone thought there was enough force to damage a gearbox then there is enough force to cause further damage and the full prop strike inspection would need to be initiated.

So where would someone think any damage would occur?

If you had stopped the engine, splinterd or desentagraded the prop, slowed the engine significantly or had a Warp Drive prop involved in a destructive incident then it would require a prop flange runout, gearbox tear down and die penetrant test, bearing replacement, crankshaft runout and a crankshaft twist inspection.
 
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Free advice is worth what is paid for it....

Considering the consequences of a wrong decision for a diagnosis of an issue like this, is it worth second guessing what the Rotax documentation says?

The prop blades are pretty tough. If there was enough abrasion to remove 1/8 of material, I think there is a pretty good chance that some level of slowing took place.

A gear box inspection is not that big of deal... not doing one when you should have could be......
 
If you believe there is enough evidence to inspect a gearbox then there is sufficient evidence to do a full and proper prop strike inspection and not do half a job.

Free advice has many values. :)
 
I was not attempting to provide a comprehensive list of a prop strike inspection, so I simple said gear box because that is the majority of it.


The Rotax documentation does not match Sinks opinion.

Rotax describes a prop strike as any contact that requires repairs be made to the propeller.

They do not prescribe a full dis-assembly of the engine for prop strike inspection.

Just inspection of accessories, the gear box, and the power take-off end of the crank shaft .
 
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Resale

Hi Wayne,
Just a little off-topic but remember that how you handle the event will be scrutinized carefully by any potential buyer should you decide to sell your -12 in the future. When I was searching for my -4, I turned down two otherwise decent planes because they'd had prop strikes and the owner hadn't followed the manufacturers recommended procedures. Not saying you have to follow their recommendations but, at a minimum, I'd carefully document the path that you do follow to help with the resale process.

And, don't forget that the first thing many RV buyers do is search VAF for information about the seller and their airplane(s).

Good luck,
Randy
 
In the line maintenance course the instructor demonstrated the crankshaft deformation check. It was pretty simple. He said his shop charges $700 to do the check, but he said the customers never complain when it comes out satisfactory!
 
Hi Yankee,
If you want to do a complete prop strike inspection by all means go for it. You evidently believe that scuffing a tip didn't cause any damage more than a scuff and you said it wouldn't be an issue in GA aircraft and I agree.


Our manuals for the most part are cut and dry, but not all issues or situations are. They are written for both untrained and trained personnel. This is where 20+ years experience comes to play. The manuals are written as guide lines and not always rule. Certainly some things are hard and fast fact, but some aren't. Untrained tend to go strictly by the manual and trained long time Rotax mechanics use them in many situations as both guidelines and fact. Knowing when to apply what takes years of experience and usually many Rotax classes. There are gray areas and some written for CYA instances. I see many prop strikes per year and if Yankee really only scuffed 1/16" the thickness of a nickel with a light composite prop then he'll be good.
There is no substitute for experience even with the manuals. There are some things in them that are actually wrong and we have been working for a change. That's one reason we have manual revisions that have been going on since the 912 was first produced.

I still stand by the comment that if you think there was enough force to cause damage for a gearbox inspection then there is sufficient evidence to do the entire prop strike protocol. It should be all in and not just part way. Half way is no better than not at all if you believe there was sufficient evidence and damage to warrant a prop strike inspection.


Common sense and experience must be included as nothing is exactly the same as in the manual for many issues. Case in point. RV12's at this point in time and low fuel pressure. The solution isn't in the manuals.
 
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Sink said:
Common sense and experience must be included as nothing is exactly the same as in the manual for many issues.
Click to expand...

I whole heartily agree.

The problem is that anyone with experience, that is giving advice in this thread hasn't actually seen the damage (there haven't even been any photos posted to look at...... So that experience is of little value since the decision is falling back to the OP's judgment of how bad the damage is.

In a case like that, I feel no one is doing him any favors, other than to be conservative.

Once again, all in with the recommended inspection is not much more than removing the gear box....... (it's in the manual)




Sink said:
Case in point. RV12's at this point in time and low fuel pressure. The solution isn't in the manuals.
Click to expand...

I am not sure what relevance this has to the discussion in this thread.......
In the prop strike instance you are saying don't follow the manual, even though it has a published recommendation.
Here you are quoting a problem that you say isn't in the manual.
?
?
?
 
I think this discussion is about peace of mind. If anything out of the ordinary happens to my engine I get out the books and see what is required. Then I get the gut wrench over the effort required, and eventually bite the bullet and do it. The only way you will put this to bed is to do the prop strike checks regardless of what a PITA they are.
 
I'm a little curious to the circumstance around the PS. seems that a gear or tire failure or possibly a hole in the runway surface would cause a minimal strike. If the OP doesn't want to share, that's fine, just curious as to how it happened.
 
rvbuilder2002 said:
I can't say for certain, but my guess would be it is probably THIS
Click to expand...

Probably. But the decription included in that entry " AIRCRAFT LANDED AT GREEN COUNTY AIRPORT, DAYTON AND THE HAND NOSE WHEEL SEPARTED FROM AIRCRAFT, DEPARTED AND, ON LANDING STRUCK THE PROP, MORAINE, OH" is so vague as to be pretty useless. Unless Wayne wants to share more details ( his choice) details of this incident are pretty much pure speculation. The description above makes it sound like the nosewheel is what the prop struck, but that is not what Wayne said in his original post.

Regardless of advice as to "common sense" etc., and not knowing every detail of the incident or damage, I would lean toward the conservative approach, and follow the Rotax procedures as outlined in their manuals. JMHO.
 
Break the chain

When something really bad happens it is usually a chain of events.

don't take any chances ( check everything )

Break the chain

My view

Joe dallas
 
Thanks for all the input

Didn't mean to start a controversy. I'm "going by the book" and gearbox will go off to Lockwood tomorrow. THANKS guys

Wayne
 
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