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Major Overhaul
There have been a few questions in this ng lately about a "major overhaul". We
all have TSMOH (time since major overhaul) as an annual inspection calculation in the logbooks. Let's say that I tore an engine down to the last lockwasher, inspected each component by whatever approved standard I wished, replaced each part that did not meet service limits with an approved part, reassembled the engine in accordance with approved data and techniques, ran the engine up and checked each parameter for proper operation (oil pressure, temperature, fuel flow, etc.), and returned the engine to service. Could I sign off that engine as a "major overhaul". Probably not. The work, if it to be signed off as a "major overhaul" must be done in STRICT accordance with the manufacturer's overhaul procedure. 1. If the manufacturer's overhaul manual specified dye penetrant inspection and I chose the much better and more conclusive X-ray inspection of a part, it is not a major overhaul. 2. If I chose not to replace a part that had not reached service limits (or new limits, for that matter) and the manual specified that the part had to be replaced at each overhaul, it is not a major overhaul. 3. If I reassembled the engine in accordance with approved data and techniques and they differed from the manual, it is not a major overhaul. 4. If I ran the engine up and measured each operating parameter and the manual specified a different method of testing and break-in, it is not a major overhaul. (This is the one that gets most would-be overhaulers...if the manual specified a test stand and a propeller club and I used the airframe and a real propeller, it is not a major overhaul. If the manual specified a Rootytooty Model AJ3 flow meter and I used the AJ4 version, it is not a major overhaul.) STRICT accordance with the overhaul manual. Jim Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
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