Superior XP-400 Service Bulletin

[BillL]

If you go back and look at the the crank failure on the Titan 400, and this one, it was a classic pressure induced fatigue of the inside fillet on the underside of the pin at TDC. Force on the rod at TDC tends to spread the cheeks against the main bearings.

Just because it was pressure induced, does not mean the crank fatigue strength was correct. There is a lot of processing that ensures the fillets are the toughest part of the crank.

If a chain breaks, either reduce the load or make the chain stronger.

[Tommy123]

[quote=N941WR;1320716]As they say in (auto) racing, an engine runs its best just before it blows up.

Good luck![/QUO

You just make that up?

[Chris Engler]

I have serial number 4 and spoke with Superior for a while today regarding the history and proposed fix. From my conversation and as stated in the SB, there is a history of detonation induced damage with some cranks. Superior's analysis has included finite element analysis of the crank based on recorded cylinder pressures while running at both 25 and 20 degrees of advance. At the 20 degree setting, pressures and resulting computed stresses were greatly reduced and resulted in an "infinite" fatigue life cycle for the crank.

The SB work will include ND testing of the crank, pistons, and rods, installation of new bearings and gaskets, and run time in the test cell. All shipping, shop labor, and parts associated with SB related issues will be covered by Superior. Turn around time is currently running 4-6 weeks from the time the engine arrives to the time they initiate the return shipping.

[N941WR]

Originally Posted by Tommy123

You just make that up?

Nope, it was a common saying back when I was racing.

[rv6ejguy]

Originally Posted by Chris Engler

I have serial number 4 and spoke with Superior for a while today regarding the history and proposed fix. From my conversation and as stated in the SB, there is a history of detonation induced damage with some cranks. Superior's analysis has included finite element analysis of the crank based on recorded cylinder pressures while running at both 25 and 20 degrees of advance. At the 20 degree setting, pressures and resulting computed stresses were greatly reduced and resulted in an "infinite" fatigue life cycle for the crank.

The SB work will include ND testing of the crank, pistons, and rods, installation of new bearings and gaskets, and run time in the test cell. All shipping, shop labor, and parts associated with SB related issues will be covered by Superior. Turn around time is currently running 4-6 weeks from the time the engine arrives to the time they initiate the return shipping.

Long term detonation would certainly explain failures and the 20 degree timing recommendation would do a lot to nix any detonation. From the discussion above, the design sounds a bit marginal IMO and if this was known for some time, why wasn't the lower timing setting mandated before?

[theduff]

They have 5 documented crank failures now. One occurred last week with an engine only running 20 degree timing. It’s being shipped to a reputable repair station for tear down. If your flying a 382 or 400 I would ground it. When people’s lives are at stake the only responsible thing we as members of this small community of experimental aviation can do is spread the word. I’m told they made 200 of these crankshafts and I wonder how many of the participants know of the risks they’re taking.

[KeithB]

My understanding is that most owners of XP-400s have been contacted by Superior (subject to the limits of owner records accuracy) by phone, and well before the SB was actually issued. I received a call (grounding my plane) on Dec 3 - I think the delays in the SB being issued were bureaucratic (legal review). I also had the advantage of being an hour+ drive from their facility. My engine was in their shop 4 days after the call and back in my hands 2 weeks later - probably a best case. The engine was installed before year end and I have 25 hours logged on it since the tear down - no issues.
I was treated very well by Superior and commend them for their customer service (I describe the experience as the best possible outcome from an unfortunate circumstance).

[BillL]

Anybody know how they got the extra 1/4" of stroke?? Is the rod pin the same diameter as the 4.375" stroke (360)? i.e. same rod bearings?

[rv6ejguy]

Originally Posted by theduff

They have 5 documented crank failures now. One occurred last week with an engine only running 20 degree timing.

Not good out of 200 cranks. It will cost a fortune to take 200 engines apart.

[F1R]

Originally Posted by rv6ejguy

Not good out of 200 cranks. It will cost a fortune to take 200 engines apart.

Just curious if the cranks were cast, forged or billet machined creations?