Converting a Private Piston Twin into a Commercial 703 Twin

[Dronepiper]

Hello!

I know commercial piston aircraft engines can be used past Airtime TBO (On Condition), but I heard from someone that there is a 10 year "hard limit" on piston engine overhauls for commercial aircraft. Is this true? Can you not just run it past 10 years and put it on condition? (Just like you would if you hit the TBO airtime?

What about commercial turboprop aircraft? Do they have a hard limit on overhauls?

Thanks!

[photofly]

Everything depends on the manufacturer's specified overhaul interval. For Lycoming and Teledyne Continental, there is a limit in terms of hours (1500/1700/2000 depending on the engine) as well as a 12 year (not 10 year) limit.

There is a ten year limit on variable pitch propellers - you may be thinking of that.

To operate an aircraft in a commercial service it will need an approved maintenance schedule. You must write that schedule based on the manufacturer's recommendation, and if you want to exceed the overhaul interval for any component (including the engine(s)) you need to be able to justify it. TC permits engines to run past recommended overhaul intervals via an approved "on-condition" program that includes things like oil monitoring and pulling a jug every 100 hours to inspect the bottom end.

CAR625 appendix C which is pre-approved as a maintenance schedule for privately operated aircraft includes this:

7. Engines

All piston and turbine engines installed in aeroplanes and helicopters operated pursuant to CAR 406, in large aircraft operated pursuant to CAR 604, and in aircraft operated pursuant to Part VII, shall be overhauled at the intervals recommended by the engine manufacturer, or in accordance with an alternative hard time interval or an engine on-condition maintenance program approved in accordance with Appendix D.

Information note:

No hard time, including calendar time, between overhauls need be observed in the case of small aircraft reciprocating engines in non-commercial private operation.

That last paragraph is noting that private piston planes are exempt from being forced to obey manufacturer calendar year and operating hours limits for engines. It doesn't apply to turbine engines.

There may be a grey area for turbine engines not operated under 406, 604 or part VII - but I can't imagine not complying with manufacturer's recommendations for overhaul on something as sophisticated as a turboprop engine.

[Heliian]

Hello!



What about commercial turboprop aircraft? Do they have a hard limit on overhauls?

Thanks!

Yes they do. It's calculated by airtime, flight/power cycles or calendar time depending on the engine. Most, if not all turbines contain life limited parts which also must be removed from service at the specified time with no exceptions or extensions.