Time in service: A nifty G3X EIS benefit

[PT20J]

 14 CFR Part 1 defines "Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing." In other words "maintenance time" is "flight time." (This is entirely different than Pilot Time.)

Unfortunately, neither of my M20Js provided a means to accumulate this time. The 1994 had an electronic tach connected to a Hobbs meter that supposedly read real time at 2500 rpm (though I've never seen that documented anywhere). This means that I was accumulating unnecessary maintenance time while taxiing, running up, waiting for clearance, etc. The 1978 was worse because it's mechanical recording tachometer read real time at 2300 rpm, so cruising at 2500 rpm, the maintenance clock was ticking faster than actual time.

A Part-135 operator I once flew for solved the problem by installing air-activated Hobbs meters. Really, doing this would quickly pay for itself, and I was thinking of doing so. But then when planning my G3X Touch installation, I discovered that the EIS includes two timers, Engine Time and Total Time, which can each be programmed in various ways. I set the Engine Time to begin recording at 300 rpm and read real time at 2500 rpm so that it should record as the Mooney Hobbs/Tach. I set Total Time to read flight time (determined by the G3X using GPS and airspeed). I'm using this total time for maintenance records from now on.

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