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