If recommended becomes hard limits, there will be no more air shows with vintage aircraft, no more movies with period aircraft and no more historic fly-ins. Many of these aircraft run orphaned or discontinued engines that can not be overhauled to spec even if you wanted to.
My aircraft runs Lycoming GO-435's. All the geared GO, GSO and IGSO (and there are plenty of those around) are unsupported by Lycoming and have been for decades. I think it's the same with the Continental geared ones.
The gearbox parts are no longer available and the factory supply was bought by one company who charges an arm and a leg for them. Last quote I got from this firm was $40,000 per engine, which is madness. If you take away the gearbox, it's just a normal O-435 that costs about $20,000 to overhaul, but they can charge whatever they want for that gearbox overhaul cause they're sitting on the parts. And when these parts dry up, there is no longer a possibility to overhaul to factory specs. Thankfully, most things can be overhauled and as an owner you are allowed to manufacture your own replacement parts for part 91 ops, so this can be sidestepped. The reality is this is how all these Helio Couriers, Stinsons, Aero Commanders, Republic Sea Bee's, Bell 47's keep flying. Sure, some of them get sent off for complete overhauls by deep pocketed owners where such an option exists, but most get patched, repaired and tweaked to run for years. Many, many engines can not be sent off to anyone, especially the older rotary ones.
Tons of other aircraft would be grounded if TBO was a hard limit. Alvis Leonides? Gipsy Majors? Wright Cyclones? P&W radials? Franklin's? Rolls Royce Merlins? Gnome's? Blackburns? It would all come to a screeching halt eventually, so although it might make sense in a bureaucrats eye and under the guise of "safety", be careful what you wish for.
Last edited by AdamFrisch; 1st May 2011 at 22:56.