FLT TIMEs do not total to FLIGHT

[jdubner]

Dynon support: I'm not sure I can articulate this clearly but I wonder if you would look at the algorithm for logging flight time on the Engine screen.  There seems to be a rounding issue in which the total of all flights' FLT TIME values  do not add up to the value in the FLIGHT field.  I use FLT TIME to log each flight but over time I see a difference in my log's total and the FLIGHT total.  And it isn't my arithmetic <g>.

For instance (and I have screen shots I can send to illustrate this), back when I had 14.9 hours showing in the FLIGHT field, an additional 20 minute flight (shown as 20 in FLT TIME) increased FLIGHT to 15.3, for a change of 0.4.  But 20 minutes should be a 0.3 and that's what I logged -- see this snippet of AFTO Form 781:

Perhaps the FLIGHT number is more accurate but it is not a total of the individual FLT TIMEs and therefore not consistent.  Would you consider having FLIGHT show a total of each displayed FLT TIME value and not a total of HH:MM:SS converted to hours?  Or alternately, allow me to reset FLIGHT periodically to agree with the sum of the FLT TIMEs (and my log)?

Does this make any sense?

Thanks,
Joe

 

[dynonsupport]

They really aren't supposed to add up, and I think you want it this way.

Remember the old days when you rented a plane with a mechanical HOBBS meter? You got in and it said 123.4 hours, so you wrote down 123.4 in the logbook. You started the plane, and 20 seconds later is said 123.5 hours. Ugh. The guy before you got a free 2 minutes and 40 seconds of time that you just paid for. Do it right, and you can get it back when you land, or maybe you lose another 2:40 again...

This is because the timer only shows 1/10th hour resolution, but behind the scenes it has 1 second resolution, and doesn't forget where it is when the plane is shut off.

Our two flight timers are actually separate timers. FLT TIME resets to zero every takeoff, but FLIGHT doesn't reset ever and works like an old mechanical hobbs.

In the simplest case, I could take 1,000 2 minute flights, and FLT TIME will always be zero. But FLIGHT will be 2,000 minutes, or 33.3 hours, because it doesn't forget the 2 minute flight. If I turn the power off to a HOBBS meter every 2 minutes, that doesn't prevent it from ever gaining time, just like landing doesn't reset FLIGHT if it was not exactly at 123.4 hours.

So, the two timers will never line up, and that's by design. If you want them to line up, you need to log flight time as FLIGHT before you take off, and FLIGHT when you land and use the difference.

One other thing, FLIGHT is based on airspeed, so if you taxi fast, you may be triggering FLIGHT on the ground some and running it up if you taxi fast or there is a lot of wind.

 

[vlittle]

And to translate to ICAO terminology:

Dynon FLT Time = ICAO Air Time. Transport Canada nailed me on this one.

Vern

 

[jdubner]

They really aren't supposed to add up, and I think you want it this way.

Thanks for explaining this.  In my background I used the aforementioned Form 781 to calculate time based on observed T/O and landing (there were no Hobbs meters) so I never gave this issue a thought.  But I'll adapt -- either field will be good enough.  I don't care about logging time for a new rating and the FLIGHT time will be better for my maintenance schedule anyway.

However, I would like to avoid having the FLIGHT field read abnormally high by taxiing too fast into a headwind   Can you tell me a speed to remain below?

Thanks,
Joe