Legal question

[whankinson]

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?

[Joda]

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).

[Floatsflyer]

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.

[Gil]

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.

[martymayes]

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.

[FlyingRon]

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).

[Frank Giger]

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.

[Dana]

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.

[jethro99]

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.

[FlyingRon]

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.

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.

[FlyingRon]

The greatest stresses (normally encountered) on an air frame result from taxiing for take off and the take off roll.

Bunk. I ain't ever seen an airframe bent or blown tire takeoff on taxiout or takeoff, but I've seen plenty on landing. Frankly, you shouldn't be "stressing" the airframe in any of those modes of operation. Hour limits are way more involved than that. You're probably one of those people who thinks the engine wear is a direct functions of the number of revolutions the engine has turned.

[martymayes]

The greatest stresses (normally encountered) on an air frame result from taxiing for take off and the take off roll.

Is that why some planes can takeoff at a higher weight than they can land at? Oh, wait a minute........

[whankinson]

OK folks. Somebody please answer my question.

Like I said, I know what flight time (Hobbs) and time in service (Tach) are.

14CFR 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.
Flight time means:
(1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing; or
(2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.

My question is: which one does the FAA want me to use to satisfy the Operation Limitations of an AB Experimental aircraft?

Anybody know of someone in "EAA legal" that could answer this?

Thanks.

[FlyingRon]

Like I said, I know what flight time (Hobbs) and time in service (Tach) are.
Apparently not, because HOBBS and TACH do not necessarily read either one of those.

The FAA wants you to use time in service. flight time only applies to pilot logbooks.

[Joda]

My question is: which one does the FAA want me to use to satisfy the Operation Limitations of an AB Experimental aircraft?

Anybody know of someone in "EAA legal" that could answer this?

There has never been a legal interpretation on this, so there is no specific answer. I know from experience that the FAA has no problem with using one's own watch to record this time, just like they accept that method when recording flight time in your logbook. This would be more equivalent to Hobbs time rather than tach time, but you could use whichever one is easiest for you to keep track of.

Happy flying...safely!

[martymayes]

Apparently not, because HOBBS and TACH do not necessarily read either one of those.

The FAA wants you to use time in service. flight time only applies to pilot logbooks.



x2. The most correct answer is “time in service”

[Frank Giger]

I am personally just amazed that someone is that keen to follow the rules so scrupulously.

Since neither Hobbs or Tach time are required to be recorded in the first place, it's on the honor system and always has been. Egregious fudging is not in the best interest of the pilot/owner of the aircraft, so it's not very common. This is why log books are so valuable when buying or selling an aircraft or engine...without them any claims of the amount of service rise to the level of rumor.

Frank "What number is the big hand on?" Giger

[martymayes]

I amazed how much confusion can be generated over a brand name. I wonder if the workers at the Hobbs hour meter company use Hobbs time for lunch break and clock time for work? Or maybe vise versa?

If the plane has a Datcon brand hourmeter, does one log Datcon time?

[lnuss]

Seems to me, Marty, that hobbs meter, like kleenex, has become a commodity name.

[martymayes]

Seems to me, Marty, that hobbs meter, like kleenex, has become a commodity name.

lol, great example Larry. All this discussion makes me thirsty, think I’ll have a Coke! One of those root beer flavored cokes!

[rwanttaja]

lol, great example Larry. All this discussion makes me thirsty, think I’ll have a Coke! One of those root beer flavored cokes!

Afterwards, you can use the cans to practice assembling aluminum structures using Pop (tm) rivets, while you drink coffee from a Thermos (tm). If you drop it, let it hit the Linoleum (tm) rather than your foot, or you'll have to take Aspirin (tm). (The last two lost their trademark protection.)

Ron "I dropped a firecracker in the kitchen and got linoleum blown apart" Wanttaja

[Bill Berson]

The FAA doesn't dictate that exact time be required. Because there is no exact time, even an atomic clock is not exact.
So I just round off to a convenient number like all my instructors did.