I know that pilots log Hobbs time for flight time and mechanics use Tach time for "time in service".
So when my Operation Limitations Letter says that I must fly 40 hours in Phase I, is it tach or hobbs?
Big difference.
Anybody have any guidance on this?
There is no specific regulatory requirement for either. The easy and best answer is, use your watch (which in most cases comes pretty close to Hobbs time).
Cheers!
Joe
I am not a lawyer but I have played one on TV. Joe is right.
The recording of times in your personal logbook and journey log is based on the honour system. You record your times based on whatever device you choose. Depending on what avionics you possess, that can be your watch as Joe said or the digital device on your glass cockpit.
I would probably use the time that I log in my logbook, which by definition begins when the aircraft first moves under its own power with the intention of flight until it comes to a stop after landing.
The FAA doesn't recognize "hobbs" time or "tach" time as an official method of time keeping for any purpose. Those are considered estimates of flight time and time in service which are official FAA terms for recording pilot time and aircraft time as defined in Part 1 of regs.
If forced to make a ruling the most correct legal answer to your question would be "time in service" but either "hobbs" or "tach" would be an acceptable estimate of that time.
Marty is right. "flight time" is time from the time the aircraft first moves for the purpose of flight to the time it comes to rest. Specifically, it's to include taxi time.
Time in service (for the airframe) is time in the air.
Fortunately, the FAA will allow just about any reasonable way of determining the numbers. TIS is commonly done on light aircraft with a recording tach. I've not had a recording tach in 13 years. I have a hobbs that is connected to the gear switch (probably about the closest approximation you can get). Of course, I've got to add 4000 some hours to its reading to get the actual TIS (I used to have to add 3000 or so to the old tach).
My Hobbs actually shows more than my flight hours, as I've done some engine and taxi tests. It's the flight hours themselves, which I lazily use the Hobbs reading before and after flights to determine.
I went one further and made a unique column in my pilot's log book for the Nieuport, though I update the airframe log with every flight as well.
The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.
I would think "time in service" would include taxi time, as rolling on the ground can be just as hard on the airframe as flight loads.
Like Frank, I add a column to my pilot logbook for time in my own plane. I don't log flights separately in the aircraft logbook, so I used the pilot logs to add it up when I needed to make a maintenance entry (until I bought the Starduster, the first plane I've had in years with an hour recording tach). I get pilot time from the clock on the panel or GPS log.
The greatest stresses (normally encountered) on an air frame result from taxiing for take off and the take off roll.Originally Posted by Dana
As I stated, as far as the FAA is concerned time in service (For the aircraft) refers to the time it is in the air. Straight out of FAR 1.1.
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.
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