Published: 08/26/2013 PDF Flyer
The flurry of news reporting related to the NPRM and recently proposed AD on TITAN® 520/550 style cylinder heads has created a minor case of ’Crack Confusion’ in the marketplace. Piston engine aviation cylinders are subjected to enormous stress as they convert fuel and air into the power needed to turn the propeller. That stress, from heat and repeated pressure pulses, can result in cylinder head cracking. In fact, 75% of all cylinders at engine overhaul contain cracks that require welding.
There are 10 common cracks, the most common of which are the port walls and the spark plug bosses. The least common is the thread root fracture, which is the subject of the aforementioned proposed AD…
A recent review of 700 OEM cylinders in an FAA Certified Repair Station found that 75% of the cylinders had cracks. Those cracks were located:
...and words can be confusing. The NPRM is related to “head-to-barrel separations and cracked and leaking aluminum cylinder heads,” not the common cracks found in most every cylinder. The NPRM is related to head-to-barrel cracking as seen to the right.
Analysis of the 19 confirmed (not just reported) head-to-barrel separations by Airmotive Engineering Corp. can be summarized by the below progression:
Visit our NPRM page for additional information and to make comments on the docket.