Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 11,059
- Display Name
Display name:
Dan Thomas
That ignores the fact that the older a machine gets, the more likely it is to fail. These engines get (or should get) overhauled at reasonable intervals, and they should get overhauled in strict accordance with the manufacturer's instructions. Field overhauls sometimes fall short of that; I've seen it. It's scary. Even at that, the 25,000 airframe hours have no bearing on the engine's hours. None.I don't think this is true. There isn't some invisible presence that knows you've flown X hours and you're becoming "due" .. I go get in a rented airplane that's flown 25000 hours in its life engine failure free, that plane doesn't know if I am a zero hour brand new student or a 10,000 hr seasoned accident free aviator who's 'due' for an event. My statistical chance of an engine failure is the same every time I get in a plane
But I digress, back to the thread..
Control surface cables and pulleys wear out. Cables fray and will eventually fail if they're not inspected, and inspecting them involves removing lots of stuff sometimes, and so it gets pencil-whipped. Pulleys seize up. Hinge bracketry cracks. Engine controls are not usually replaced at engine overhaul, but they should be. I have seen one failed throttle cable and two failed carb heat cables. That 25,000-hour airplane you rent, if it has not been meticulously inspected, will have cracked airframe components. Every airframe design has its weak points.
I've had two engine failures. One was a broken crankshaft. The engine had been field-overhauled without the manufacturer-specified NDT during overhaul. The crank had cracked due to a long-ago propstrike. The other failed because its carb fell off due to no locking of the carb's retaining nuts. I later bought that airplane, and when I tore the fabric off the wings I found the rear spars of both wings cracked, one of them 3/4 of the way through, and that crack had been there a long time, judging by the wear of the wood in the crack due to movement. It could have come apart in flight in any real turbulence or spin recovery.
Stuff like that made me a careful mechanic and a skeptical pilot. As the Director of Maintenance for a flight school, the government flight-test personnel told me that our airplanes were the only flight-school airplanes in their whole region that they weren't afraid to get into.
Last edited: