Logging Tach Time
I have searched around a bit and seen this touched on before, but I am still not entirely clear on the best way for me to log my flight time in the aircraft I am currently flying.
The aircraft is a Mooney M20C (Mark21) which does not have a Hobbs meter (the way I always used to track time) and only Tach time. I realize I could probably note time at startup/shutdown and log time off a wrist watch that way, however I do tend to forget those types of things and would greatly prefer to go off an installed device.
Nearly everything I have seen says that Tach Time will nearly always be *less* than what a Hobbs meter would read...since ground operations count slow on the Tach, and times at high RPM (climbout) aren't often enough to offset the lost ground time. I have timed several flights with a watch (startup - shutdown) to compare to the logged Tach time and have found that my Tach time has been *higher* than what an installed Hobbs would have read.
A couple examples...
Tach: 2.87 Time: 2.56
Tach: 2.56 Time: 2.43
Tach: 1.60 Time: 1.53
Tach: 2.92 Time: 2.66
Tach: 3.38 Time: 3.13
Tach: 1.02 Time: 1.00
I have a bunch of other flights I am waiting to log, but those are the only ones I have accurate wristwatch comparisons.
I do operate at somewhat high power settings as the increased speed is worth the added fuel costs for the flights being taken. The aircraft is set to 25"/2500RPM for climbout and 25/2500 for cruise flight if able (generally flown at altitudes where 25" can not be maintained, so Full Throttle/2500RPM is used)
So...what would be the recommended times to enter in a log book?