FAA Publishes AD On Superior Crankshafts (Updated)


Some 257 four-cylinder Superior and Lycoming engines are now subject to a new airworthiness directive requiring crankshaft replacement within 25 hours. A Notice of Proposed Rulemaking was published in February but the new AD goes into effect on Jan. 15, 2021. The engines include Superior’s own IO-360 and O-360s as well as certain Lycoming 360-series models that may have had the crankshaft installed as a replacement part. The AD lists specific serial numbers for the parts, which were delivered between 2012 and 2014.

Superior has responded to the AD, saying that it has assembled a team of engineers and metallurgists to work with the FAA and AOPA to develop an “alternate means of compliance,” or AMOC, for the AD “at a significantly lower cost” than replacing the crankshaft. “We are very confident that the FAA will approve the proposed AMOC prior to the A.D.’s assigned active date of January 15, 2021,” Superior said in a statement. “Superior’s primary goal, in this unfortunate situation, and always is the safety of our customers and their passengers. We feel that delivering an affordable alternate means of meeting the AD’s requirements, that also encourages early compliance is a major step in that direction.” Superior will release more details on the AMOC as soon an agreement is reached.  

According to the FAA, the AD “was prompted by three crankshaft assembly failures that resulted in the loss of engine power and immediate or emergency landings. The FAA is issuing this AD to prevent failure of the crankshaft assembly. The unsafe condition, if not addressed, could result in failure of the engine, in-flight shutdown, and loss of the airplane.” The accidents happened between March 2017 and October 2018, and all were in training aircraft.

The FAA says that crankshaft failures resulted from “residual white layer formation, also known as a compound layer, on certain crankshaft assemblies as a result of improper manufacturing by a third-party vendor.” Superior, however, disputed the FAA’s findings, saying that the cranks had proper material and heat treatment, and that the fatigue fractures noted in the three broken cranks were not consistent with a too-thick “white layer.” 

“As supported by the reports, the FAA finds that white layer contributed to the early crack initiation and, on all failed crankshaft assemblies, exceeded OEM specifications,” the agency said. Superior also contended that the engines had been subjected to “misuse, abuse, or lack of lubrication,” but the FAA also rejected that argument. 

Superior has not said what it will do for owners of the affected engines, nor is it clear that replacement crankshafts will be immediately available. In general, engine shops are reporting shortages of certain critical parts due to COVID-19 slowdowns. It’s also worth noting that the AD applies to certified aircraft and not, explicitly, experimental/amateur-built aircraft, which have been touched by the issue. However, most builders are expected to abide by the terms of the AD and seek replacement crankshafts even if they aren’t legally required to. 

Marc Cook
KITPLANES Editor in Chief Marc Cook has been in aviation journalism for more than 30 years. He is a 4000-hour instrument-rated, multi-engine pilot with experience in nearly 150 types. He’s completed two kit aircraft, an Aero Designs Pulsar XP and a Glasair Sportsman 2+2, and currently flies a 2002 GlaStar.

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  1. > “the $14,821 compliance cost per [SE] airplane is minimal.”

    Wow. The only good thing I can say is if you’re not flying, wait until corona is over since there’s a likely chance that your crankshaft is already pitted. (See Mike Busch’s engine videos.)

  2. Superior is taking the low road in blaming owners. I will certainly never do business with them after hearing their comments about it. How can you trust a company that points fingers at its own customers? I sure as hell don’t.