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Service Bulletins 19-08-26 and 16-05-23 Published - Nose gear leg and fork

Interesting that we are changing out nose gear legs for a perceived weakness, but the one that breaks on overload failed at a different point. Scott, wouldn’t that support the preexisting flaw theory for this failure?
 
Interesting that we are changing out nose gear legs for a perceived weakness, but the one that breaks on overload failed at a different point. Scott, wouldn’t that support the preexisting flaw theory for this failure?

https://www.vansaircraft.com/wp-content/uploads/2021/01/SB-19-08-26-Rev-2-Nose-Gear-Replacement-.pdf

“ Synopsis: An RV-12 training aircraft with more than 1700 hours of accumulated flight time recently experienced a nose gear fatigue failure. This is the only reported instance; no other fatigue-related nose gear failures have been reported. The failure occurred in the nose gear leg at the point where the leg tube meets the lower attachment bracket, and was caused by a fatigue crack that propagated across the tube. The crack occurred at a location that is not visually inspectable. It is, therefore, strongly recommended that owners of RV-12/RV-12iS aircraft with the original style nose gear leg (WD-1201) replace that part with the available updated, reinforced leg - part number WD-1201-1.”…
 
Maybe a good idea to not install fiberglass fairing on the nose leg to allow better visual inspection that would normally be covered. When I installed the new nose leg I made decision not to reinstall the fairing. I also cut of the trailer tie down loop for cleaner appearance...
 
Interesting that we are changing out nose gear legs for a perceived weakness, but the one that breaks on overload failed at a different point. Scott, wouldn’t that support the preexisting flaw theory for this failure?

I don't even know how to respond other than say there is clearly a misunderstanding of the difference between a fatigue failure and a single event overload failure. Not to mention that the failure in this thread was in a totally different part of the nose gear leg.

The single instance failure of an RV-12 nose gear leg (as related to the location on the leg focused on in the S.B.) occurred on one that had 1700+ hrs in service at a flight school. It was a fatigue failure as a result of the high number of (flight school) flight hrs at a location that was determined to be vulnerable to fatigue (as detailed in the S.B.)

The failure that occurred as the subject of this thread was a pure overload failure and could happen to any RV-12, regardless of the hrs., if a landing is botched badly enough.
 
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I did sell my newer front landing leg to a Dr in St George, this fall, that had the original fork fail upon landing. It broke near the axle, somehow.

It, of course, was supposed to have been replaced several years ago when the Service Bulletin came out to do so, probably 2017 or 2018 ish?

He did order the fork from Van's, they had it in stock, but the front landing leg was on back order for months, so I sold him mine so his AP could get him back up and flying again.

Upon review of flightaware, there had been a pvt dirt field landing that occurred 2x before failing on tarmac at KSGU. I can't confirm or not if that was a consideration in the fork failure.

My point being, both fork and landing leg have had service bulletin upgrades, in this case the fork cracked and failed. Much. much less damage, overall to fix, but still, it could have been a lot worse for him, too.
 
I am curious if the Anti-Splat Nose Job 2 brace would have made any difference in the failure point or damage outcome for this overload failure. I presume the gearleg failed down (collapsed) vs the fold under failure, where it bends under and back if the nosewheel catches a rut or berm on landing.

John Salak
RV-12 N896HS
 
The nose leg in the accident aircraft failed not because of a design problem, but
because the airplane dove into the ground nose first. If the nose leg were made
stronger, then the complaint would be that the firewall was not made strong
enough. Try pole vaulting with a half inch plastic water pipe. It will fail in the
middle, not the ends. Same principle.
 
It's hard to tell which way the noseleg failed - I wasn't even in the country at the time! I suspect it tucked under. Here's a picture of the nosewheel. You can see the front end of the leg creased above the fork. You can also see a failed weld at the bottom of the fork.

https://www.dropbox.com/s/jw9yr5a6s0ipkar/Nosewheel.jpg?dl=0

I took a look at the Dynon statistics recorded on the flight. Unfortunately the D180 only records data every 5 seconds or so, which means that it is difficult to interpret what is happening just before encountering the ground. This data point is when the pitch angle went from zero to minus 24 degrees!

So just before this I spotted the following partameters:

Airspeed 56 kt
Groundspeed 60 kt
VSI minus 200 fpm
AOA +5 degrees
G force 1.06
RPM 2200

All of this looks pretty normal to me. The groundspeed was higher than the airspeed as the pilot landed downwind. There was some confusion about wind direction as this was the second or possibly even third attempt to land. It later transpired that the windsock was "jammed". Indeed at the instant the plane "landed" someone was up a ladder investigating the problem. He was almost hit by a propeller blade wizzing past his head!
 
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Noseleg report

Just to put this one to bed.

Scott was correct. Isn't he always :). This is the broken noseleg report from the UK Air Accidents Investigation Branch, addressed to my flying partner.


From: "Connor, Steve" <[email protected]>
Date: 8 February 2022 at 12:18:09 GMT
To: Bill E-mail <[email protected]>
Subject: G-RMPS nose leg Investigation


Bill,

After an examination by metallurgical forensic engineers under an optical microscope, the conclusion was that the leg failed in overload. There was no evidence of fatigue. So the evidence points to a hard landing sufficient to fracture the leg in overload. As a result, the investigation has been categorised as a Record Only and there will be no further investigation from me.

I hope you get the aircraft repaired and flying soon. At least you will have the opportunity to fit the upgraded nose leg recommended by VANS.

If you have any further questions, please ask.

Regards,

Steve Connor
Senior Inspector of Air Accidents (Engineering)
Air Accidents Investigation Branch
Farnborough House
Berkshire Copse Road
Aldershot
Hampshire
GU11 2HH
Tel +44 (0)1252 531530
Mob +44 (0)7802 212244
Fax +44 (0)1252 376999
[email protected]
 
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A tip for SB 19-08-026 compliers: I found that an approximately 16" length of 5/16" dia. wooden dowel was very useful in driving out the two lower AN 6 bolts. Any straight metal 5/16" dia rod or tube would do as well.

This makes it sound like you had the AN6-27 bolts inserted from the engine/cowling side with the castle nut inside the cockpit. Is this the correct direction for these bolts? I am doing my annual now and performing the nose gear leg replacement presently. I purchased a flying -12iS and these bolts are inserted from the cockpit side with the castle nuts on the engine side on mine. I want to put it back together correctly!
 
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