Rounding up flight time

Shane Cassell

Shane Cassell

Well-Known Member
I have a question that I am unable to find any official answer to. The company I will be working for has a tachometer that displays flight time in hundredths. I don't really see the point in logging it in hundredths. If I were to have a flight that was say, 2.99 hours, could I round it up to 3.0 or a flight that was 2.57, could I round up to 2.6?
 
Although this doesn't directly answer your question, generally when using a hobbs, you round up whenever the next number starts to "show" This is how most flight schools charge for the airplane and how students log the time as well.

Remember that a tach is based on engine RPM, so it is not a accurate measure of time.

The general rule way of keeping time is just using the hobbs, or if not equipped, keep a timer once you begin to move under your own power for

When flying the jet, we have an "air hobbs" and since according to the FAA flight time is whenever you are moving for the purpose of flight, I write down when we "block out" and "block in" then convert it, and round the 100th up or down.

I don't think anyone is going to question the fact you rounded up, and added 36 seconds to your logbook (2.99 vs 3.0) from a tach.
 
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I also don't have a reference but I certainly think it's a widely used and accepted method to round up on the 10ths. I just looked and Interestingly enough I keep my logbook with the 10ths but my company records time in minutes. The difference over a year gave me an extra 2.2 hours last year. Hmmm. Maybe I'd better start doing this in the hundredths now… :)
 
There is no guidance except that you record flight time. How you arrive at that number is not dictated.

However, since you wrote "tachometer", the chances are you are shorting yourself a little flight time if you take the numbers from the tachometer. The tacometer is only accurate (more or less) when you are operating at a cruise RPM. So, all of the time when you are on the ground or at a reduced power on descent, your tachometer is not recording one minute for every flight time minute. To get the full benefit of the flight time you are actually accruing, you might want to record the clock time when it starts and the clock time when it ends and use that.

There is one other wrinkle you should consider. Let's look at the definition of Flight Time in Part 1 of the regulations:

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
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Note the part about "moves under its own power". So depending on the type of airplane you're flying, you might want to start the engines, check the oil pressures, and move forward to check the brakes. That way you have moved and flight time starts.
 
Shane Cassell said:
I have a question that I am unable to find any official answer to. The company I will be working for has a tachometer that displays flight time in hundredths. I don't really see the point in logging it in hundredths. If I were to have a flight that was say, 2.99 hours, could I round it up to 3.0 or a flight that was 2.57, could I round up to 2.6?
Click to expand...

Heck yes that's okay. Some guys round up to the next 10 hours.
 
With a tach, even the old "multiply by 1.2" rule of thumb can be pretty inaccurate, depending on the type of operation.

I write down the time for engine start, wheels up, and engine stop. Use that.

For stuff like glider tows, after looking at the averages for a few years, I do 0.1 per 1000' and it comes out pretty darn close. (Possibly is low on hot days, high on cold ones). Fly what you want, log what you need.
 
This is helpful. Thanks everyone. I wasn't thrilled about having to use a tach, but that's all the planes had and before this I didn't realize you could use a clock or timer.
 
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