shrike wrote:
The O-470-7 is the equivalent of the E185-3 which has a TBO of 1500hrs*
The O-470-11 is basically a Continental E series engine with a modified accessory section.
The O-470-A etc, parallel valve engines use essentially the same cylinders and rotating parts, albeit with a flange for the prop instead of SAE splines. They also have a TBO of 1500hrs*.
So, a very supportable argument (the kind the FAA likes) could be made for a 1500hr TBO
*as per SIL98-9A
The O-470-7 and O-470-11 overhaul manual (T.O. 2R-0470-3) does not specify a TBO, although it does provide rather detailed inspection criteria (Better than most TCM manuals). I have a copy to hand as I type
One big difficulty is that TCM no longer supports any of the E-series, or parallel valve O-470 engines, making parts difficult to procure at best. Our shop has stopped doing overhauls on them for that very reason.
TBO is, as has been pointed out, a recommendation in most cases. The big killer of engines is not the time they spend working, but rather the time they spend sitting. I've seen 520's make 3600hrs with regular use (yes, it was worn out by then, but not as bad as it could have been), and I've seen O-300's need a complete overhaul at less than 100 (rusty from sitting, but oh so pretty on the outside)
This is exactly the information that I needed. Concise, accurate and to the point. Thanks very much for responding.
Best Regards
Steve