Anonymous

The following comment is from the perspective of a long-time pilot with a substantial background in aerospace engineering. The separation of a cylinder head in flight is not by any means, a minor occurrence. A cylinder separation is in fact a significant safety event that can cause either immediate, or a nearly immediate engine failure, which has been known to cause catastrophic loss of the aircraft, flight crew and passengers. The occurrence of a general aviation aircraft crash into homes in Florida in recent months past is an example of the damage that can occur when a GA aircraft hits the ground, for any reason. So, if it occurs over a populated area, it could also cause significant damage and loss of life on the ground. In this NPRM, the FAA already concedes that the failure and separation of some of these Superior cylinders have already resulted in forced landings of aircraft. I have been told by an Alaskan operator that some of the aircraft that had such cylinder failures were actually forced down in difficult terrain, such as on Alaskan beaches. I suggest that the FAA talk to the folks at Smokey Bay or Homer Air up in the Kenai Peninsula. The ocean water in locations like the Kenai Peninsula is always extremely cold and the threat of hypothermia to a downed pilot is a real one, even if one survives the initial crash. The proposed inspection every fifty hours therefore does not seem to be an adequate response for a potentially life-threatening problem that the FAA recognizes is caused by a known design deficiency. Discussion with the same Alaskan operator indicated that their belief was that the cylinder wall was considerably thinner than the OEM cylinders. It is not clear why these defective cylinders are not removed from service. The proposed FAA solution whereby you essentially are looking for cracks after they have developed will put the flying public at risk. If the crack has developed there is no logical evidence presented by the FAA that failure would not immediately result in a failure. The FAA’s assumption is that they will find cracks and then replace cylinders. I suspect they will only be investigating the cracks at the scene of the accident. The FAA offered no rational evidence to suggest why their proposed inspection intervals are adequate. It would have been helpful in evaluating their proposal to understand what data they used in proposing the 50 hour intervals. I assume such data is available and they should have presented it as part of this effort. If they are just making up numbers, that would be interesting as well…………. I recommend that the FAA rethink this NPRM and remove these cylinders from service prior to the TIS of the documented failures to prevent an avoidable, future catastrophic accident.