FAA Maintenance Alerts

Lycoming: O-360A4M; Cylinder Separation; ATA 8530
A mechanic states, “The pilot experienced a noticeable pop sound in the engine compartment, followed by roughness. The engine oil pressure started to deteriorate and the pilot elected to shut down the engine, stopping the propeller from turning by putting the aircraft (Cessna 172N) in a nose high attitude. He managed to glide to a major airport and successfully dead-stick land without accident. Investigation showed the number one cylinder head had separated from the barrel.... This cylinder was replaced 206 hours earlier—when the engine was overhauled. The cylinder was purchased new from ECI in San Antonio, Texas. The popular name is Titan Cerminil (P/N AEL 65102). A new Titan cylinder was installed. The engine ran normally with no adverse problems noted. The separation of the cylinder is thought to be (caused by) stress cracking due to threads cut in the cylinder head having little or no radius in the valley of the threads—thereby setting up stress risers. Separation tear marks belie earlier cracking that eventually led to total fracture of the head assembly.” (The SDRS data base provides 341 records for the 8530 JASC code, 10 of which specify cylinder separation.)

AC 43-16A December 2007 Page 10
Lycoming: O-320-D36; Leaking Carburetor Float; ATA 7322
“On shutdown (this aircraft’s engine) RPM increased 400 RPM,” writes an unidentified submitter. “At idle the engine would (run) at 600 RPM, drop to 300 RPM, then die. Upon opening the carburetor (I found) one half of the white plastic float was 80 per cent full of fuel—it did not leak out over night.” (Precision Airmotive carburetor, P/N LW 15986-85; float P/N 30-804. The SDRS database reports at least four fuel-laden carburetor floats.)

Lycoming: O-360-J2A; Broken Rocker Arm; ATA 8530
A mechanic working a Robinson R22 Beta II provides a short description and two photographs of this engine’s defect. “The number four cylinder intake rocker arm cracked and split into two pieces (P/N 17F19357). The probable cause (for its failure) is aggressive machining of the rocker arm and/or the rocker arm incorrectly contacting the keeper spring assembly. MORE