When do you start logging time on your engine?

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skeeter_ca

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I was just letting my mind wander the other day and out pops a question. When do you start logging time for your engine in your homebuilt? Does it start the first time you crank it over or after initial starting, bugs worked out and running good ready for flight?

:)
 

Topaz

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Hours is hours. When the crank starts turning, so does the Hobbs meter. The parts that are wearing don't care whether it's on a test stand or flying in an airplane.
 

JamesAero

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That's true for most rental aircraft, but most corporate aircraft have the Hobbs meter connected to a "weight on wheels" switch. The only time charged against the airframe or engine(s) is flight time.
 

Topaz

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That's true for most rental aircraft, but most corporate aircraft have the Hobbs meter connected to a "weight on wheels" switch. The only time charged against the airframe or engine(s) is flight time.
I'd imagine, in that scenario, that the maintenance team has some other means of determining total-time on the engines.
 

Dan Thomas

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That's true for most rental aircraft, but most corporate aircraft have the Hobbs meter connected to a "weight on wheels" switch. The only time charged against the airframe or engine(s) is flight time.
For light aircraft in Canada, the government requires that only the air time (off the ground) counts toward the lives of components like engines, propellers, airframes and their various bits. An engine that is started and warmed up suffers a bit of wear before the oil reaches everything, but it's relatively minor compared the stresses and heat an engine in flight endures. A more accurate measurement would be both air time and the number of starts.

A homebuilder that spends a lot of time testing his engine at high power on the ground might want to record those hours. Ground running at higher power levels generates a lot of heat that sometimes isn't taken away nearly as well as it would be in flight. And it's breathing dirtier air, too.

The owner that runs his engine on the ground for a few minutes "to circulate the oil" and then shuts it down and puts it away until next time is ruining his engine. One of the byproducts of combustion is water vapor, and some of that gets past the rings and into the crankcase, where it condenses and mixes with the oil and form acids over time that eat the engine up from the inside. It takes a half-hour or more at 180°F oil temp to boil off the water accumulated during start and warmup and the best way to do it is to fly it. Watch out for "low-time" engines that were last rebuilt 30 years ago. They might have had such treatment in the form of really short flights.

The operators of large aircraft have to count the number of starts of turbine engines, the number of takeoff/landing cycles, the number of pressurization cycles, and air time. Gets pretty complicated, and any one of those things can time an aircraft or engine out before the other numbers get even close.

A recording tachometer is often used by some folks. It measures hours based on some median RPM, and a renter can get more time for his money by cruising at a lower RPM.

Dan
 

Lucrum

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I'd imagine, in that scenario, that the maintenance team has some other means of determining total-time on the engines.
Not that I'm aware of, although generally if you go to T.O. power you're supposed to count that as an additional cycle on the engine. Even if you never left the ground. I doubt all of them get recorded.
 

skeeter_ca

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All the planes i rented you started paying as soon as the engine started.

But as for testing, do/did anyone of you guys run the hour meter before the first flight during testing and log it?
 

Dan Thomas

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All the planes i rented you started paying as soon as the engine started.

That's normal. It's called Flight Time, at least in Canada, where flight time is defined as the time between engine start and engine shutdown where there is intention to fly. Air Time is the time off the ground. Flight time is what the pilot is credited with in his logbook.

Dan
 

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