Logging Flight time from Tach Time

[juredd1]

My 152 had a hobbs meter in it and the best I can recall that is what I was instructed to use when logging my flight time. However the 170 does not have a hobbs meter. During my recent flight instruction my CFI said the tach only reads the correct hours at 2400RPM's or something along those lines so he took the tach time x 1.2 to get his billable hours and the hours put in my log book.

Does this sound right or do you all just use the time straight off the tach to log flight hours?

Justin

[bagarre]

The tach reads 1hour fairly accurately at 2400 RPM...if your tach reads 2400 RPM accurately. It's not uncommon for a tach to be 100 or so off.

Did you fly 20% of your lesson at 1200 RPM? 'Cuz adding 20% to the bill seems pretty convenient for HIM.

Tell your instructor to buy a watch and keep a pencil and paper in the cockpit.

[cessna170bdriver]

1.2 sounds a bit steep, especially if it happens to be cross country. I set my panel clock to 12:00 on first start of the day, then log what it says at the end of the day. (Electric clock wired to main bus through a fuse; comes on with the master switch.) Some only log time separated from their shadow, but I log the time I'm responsible for the operation of the airplane, essentially what would be Hobbs time if I had one.

[KS170A]

Two methods I would consider:
1 (what I actually do in my 170) Zero out my GPS flight timer as soon as I turn it on, then reference it just before I shut it down. You could use a kitchen timer, watch, or any other method and achieve the same result.

2 (what I use in turbine airplanes I fly since the Hobbs is tied in to the weight-on-wheels switch, thus tracking actual air time, not pilot time): Add .2 to the recorded time.

What I have found in my 170 is that since I typically cruise at 2500 RPM (indicated...have not verified its accuracy), my tach time and elapsed time on the GPS timer is very close on 1-hr+ flights. In an earlier post, I had posted the design 1:1 recording speed, but it's in the neighborhood of 2400-2450. There again, that depends on the tach's accuracy. I find that using a timer from start-up to shut-down is the easiest for me. MULTIPLYING the tach by 1.2 does not necessarily accurately reflect flight time, unless that's what the instructor wants to charge (and you've agreed to pay) for his services (and his lesson planning that he should be doing before your lesson, etc).

[GAHorn]

As for CFI-Billable instruction-time....it doesn't matter what he uses as long as it's consistent .....and YOU know upon what/which standard the instruction-time is based....and agree to it. (If I charge you $50/hr based upon my wristwatch from the time we shake hands until we say "GoodBye"... or $60/hr based upon your tach time...or $55/hr based upon 1.2 times your tach time...what possible difference does that matter??? as long as we have agreed upon it and we use the same standard each time????

As for your logbook...Yes, the tach reads slightly slow at low RPM....then reads slightly high during high RPM (such as climb) and it tends to average-out and be close enough "for gov't work" such as logbooks for most people.

But, legally-speaking.... the FLIGHT TIME begins when the aircraft FIRST MOVES UNDER IT'S OWN POWER for the purposes of flight and ends when the aircraft COMES TO A STOP at the end of the flight. This is the standard used by the insurance company and the standard used by investigators. Most professional pilots, if queried in a serious question, will log ALL the actual time spent airborne and HALF the time spent taxying.

Guess what? ....that just about equals within 10% plus/minus the tach-time....(which is what I log personally for pilot time in my own airplane.)
At work, I log as Flight time the amount actually detected by the flight-timer which is connected to the landing gear "squat switch"....(time actually airborne)..although that cheats my logbook very slightly, I quit my concern about my total flight time a few thousand hours ago.

If I were your instructor, we'd agree and shake hands on my clock beginning at the moment we greet each other until we end the lesson. This keeps us both on task, keeps us ON-TIME, and ON-SUBJECT in order for you to feel you got your moneys-worth. If YOU are late more than twice, I will warn you that next-lesson begins at the agreed meeting-time. And if I'm late, (has virtually never happened) I give an equal amount of time without-charge.

For illustration-purposes only (I'm not soliciting):
I charge $50/hr for primary instruction and $75/hr for advanced, and $700-$1000 plus expenses (depending upon model) for each days work as a contract-pilot of your medum jet or turbo-prop. My first flight-lesson is free if afterward you don't agree it was well worth it.

[Bruce Fenstermacher]

Tachometers are built to log 100% at many RPMs not just 2400. For example you could have a tach which is geared to be 100% accurate at 2300 RPM and another that looks exactly the same might be geared for 2450. Most tachs are marked on the back with a stamp what RPM they are calibrated for.

In a helicopter in the Army flight time started when you increased power with the intent to fly. You don't actually have to get airborne and the helicopter may never move and you can be logging time.

[juredd1]

Thanks for the info.

I didn't think that it sounded right as your on the ground before take off 5-10 minutes and then you should be reading pretty close to the right time after that point. We did have a lot of touch and goes and in the pattern and maybe it makes some sense there but there was also a lot of cross country as well.

Nothing was discussed about this prior to training and only mentioned as we started our first instruction flight. I was 1450 miles from home and had to get my sign off to fly it back home. I was kind of in a tight spot and had no room to irritate my instructor nor did I have a backup CFI waiting. Nor did I really consider it an issue at the time, I was happy if I got my sign off in 9 hours and it's logged as 10 I don't care. So maybe it cost me an extra $50.

As George mentioned I am find with Tach time, much easier for me if the insurance and other interested parties are good with that standard. I was just trying to figure out an honest number to log in the books.

By the way I was only late once and he hinted on it enough so that the next morning I she was fueled up setting on the taxiway (airpark and the airplane was housed at the end of the taxiway) and I was setting on one main with my one leg crossed. He smiled as he arrived for instruction, I think he got a kick out of that. He understood then that I got his point and his time was important to me.

Thanks again,
Justin

[GAHorn]

... You don't actually have to get airborne and the helicopter may never move and you can be logging time.

That explains a lot.

Justin,
For convenience, many instructors use the aircraft time-piece to account for billing purposes. In most cases, that is heavily in-favor of the client, but few folks raise the issue.
Think for a moment about a 1-hour period of instructional-flight: (1)The CFI first briefed the client on the purpose of the lesson, the actual manuevers to be attempted, the techniques to be used to correctly accomplish the excersise, and the standard to be used for evaluation of the successful outcome. (2) The aircraft preflight is performed. (3) The engine startup and pre-takeoff checks are accomplished. (4) The actual flight commences, the lesson experienced, and the return-flight, landing, taxi-in, tie-down is accomplished with the tach/hobbs running. (5) The de-briefing and critique is completed.
Items (1), (2), (3), and (5) can easily equal or exceed the "flight" recorded by the time-piece. Yet it is most likely that most of the "education" of the lesson actually occured when the time-piece was not operating.

Instructors usually take that into consideration when they set their instructional-rate, but it is possible the client may not realize that the entire period is what defines the instructional experience, and that client may become disenchanted without realizing that most instructors give far more than that for-which the client is charged.

Try that with your doctor or attorney (who rarely co-shares the personal-risk of the activity.)