Superior Air Parts announces it is implementing an immediate and mandatory buy-back program for all XP-382 and XP-400 experimental engines
The company is contacting each XP-382 and XP-400 series experimental engine owner to arrange to immediately buy-back their engine.
https://newsline.kitplanes.com/2019/02/28/superior-buying-back-all-xp-400-and-xp-382-engines/
There are some good threads on the XP engines on VAF, but I thought we might have some discussion here. These engines have wide applicability outside the RV community, but are specifically intended for the homebuilt community because of their lack of certification.
Judging by the VAF threads, it appears that the engines are experiencing detonation, which is drastically shortening the service life of the crankshaft.
Here is the materials report from a fatal RV-8 accident involving the fracturing of an XP-400 crank (.pdf link).
I'm hoping that Ross and Billski will offer some insights into this situation.
[Edit add] One interesting thing I see in the materials report is that the crank appears to have mounting ears for a pendulum-type damper between the #3 and #4 rod bearing journal, but nothing between the #1 and #2 journals. Not to confuse symmetry with balance, but what might be the rationale for that location for the damper?