how far past SMOH would you fly?

montanapilot

montanapilot

Well-Known Member
just browsing aircraft for sale sites and ran across these bad boys fresh from a flight school. Freakin scary I tell ya. Is this a common practice for flight schools to run engines this far past recomendations? Isn't that just askin for a lawsuit to run engines that far past TBO?

1973 Cessna 150-L
N-153DA S/N 15073786
Total Time: 9220 Hrs.
Engine: Continental 0-200-A
3800 Hrs. S.M.O.H. By D & B Engines *(TBO is 1800 by the way)
Compression: 76/80, 74/80, 76/80, 75/80
Last Annual: 04/01
Avionics: King KX-170B Nav Com
Narco AT-50A Transponder
Narco 31A ADF
Flight Com 403MC
Asking: $9750.00

1981 Cessna 172P
N-52272 S/N 17274474
Total Time: 5520 Hrs.
Engine: Lycoming 0-320-D2J
3269 Hrs. S.M.O.H. By Penn Yan Aero *(TBO 2000 by the way)
Compression: 70/80, 74/80, 75/80, 75/80
Last Annual: 07/02/04
Avionics: Bendix BX-2000 Transponder
Nav Com/Marker Beacon
Digital DME
Bendix ADF
Asking: $48,250.00
 
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3800 Hrs. S.M.O.H.[/b] By D & B Engines *(TBO is 1800 by the way)
Asking: $9750.00


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...with 2000 hours on the engine since it was supposed to be overhauled, I'm suprised they are even asking this much. That's crazy that they ran them that much over the TBO. Makes me glad that at the club I fly you can view the maintenance records online.

-BL
 
If an engine is flown a lot, I'd have no problem with taking it well over TBO. I once owned a 172 that we ran as an IFR trainer and it had 2500 hours SMOH when I sold it. It had good compressions and was burning about one quart every 8 hours. On the other hand, if a plane sits around and doesn't fly, low times on the engine don't mean much.

TBO's are a recommended by the manufacturer and are not regulatory in part 91 ops.

The 150 looked like a great buy until I saw the annual date. It's probably been sitting around a lot and the annual could get ugly. Depends on the condidition of the airframe, but it could still be a good deal.
 
There is never any reason for a pt 91 operator to overhaul their engine at TBO. TBO is just a number, like life expentancy. The actuall health of the engine is far more important. The # of hours it has run is completly irrealavant.

I personaly know a guy that flys pipeline patrol almost every day in a C-172 with 6000+ hrs on the engine. The compresion and oil consumption haven't changed in years. Oil anyilsis always comes back clean.

The absolute best thing you can do for any airplane is to fly it! I would be far more concerned about a low time airplane that had sat in a hanger for many years than I would be about a plane that flies regulary.

If the engine is running fine, then keep running it!
 
I was talking to a pilot today and it reminded me of this thread.

He asked about the differance between a "top overhaul" and a major one. He belived (as do many people) that a major overhaul was required at TBO. I said "Most people who need heart bypass surgery need it at 55-60, so I guess you should scheduale yourself for one"
wink.gif


This is the same logic used for figuring TBO. TBO is basicly the life expantcy of the engine. However, just as you wouldn't have surgery done unless it was called for. Neither should you tear your engine apart.

A top end overhaul is one that replaces the cylinders without opening the crankcase. The cylinders are the components that most often are the cause for the overhaul. They are subjected to the most thermal stresses. Particularly the exaust valves and seats. The exaust gases flowing past the valve are not much colder than a cutting torch. The cylinder barrels are steel, and the heads are aluminum, which becomes a problem as they heat up and expand at diffrent rates.

On the other hand the crank & camshaft do their thing surounded in nice oil which is routed through. This oil is cleaned in a filter and cooled before it touches the berings again. If you are performing oil anyalsis (and you should) this will give you warning before any berings go bad.

I personally wouldn't split the case on any engine that was showing no signs of abnormal metal in the oil. Regardless of the time on the clock. Changing cylinders as needed is sometimes nessacery, but opening up a crankcase is useually overkill unless you have a propstrike or metal from the bearings start showing up in the oil.

Note that this is only legal on aircraft that are operated under PT 91. If a plane is flown under pt 135 it's engines must be overhauled at TBO. However many 135 operators have been granted extensions and run past TBO under careful monitoring like oil anyilsis.

For the most part engines and everything else on airliners are only replaced "on condition". This translates to "fly it till it breaks, then we'll fix it"

There is no reason for pilots and owners of Cessnas or Pipers to hold themslves to a hingher standard and replace perfectly good engines.
 
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