Oh io540, nothing works for you unless it's full of silicon and costs thousands of pounds. One wonders how people got along in the old days.

How about using a marker pen and a stick of wood. After a little bit of work you can even throw the marker pen away. This will allow you to work out how much fuel you start off with and how much fuel you have finish with. Use some mental arithmentic (remember that??) to calculate the difference and bingo, you know how much fuel you used.

I know you will find objections to this simple solution, but they are all easily worked around.

My club charges chocks off to chocks on but, if we experience a taxy/take-off delay, we are told to report it to the club and they adjust the time accordingly. I've done it once, after holding for commercial traffic at Bournemouth. That seems like a fair policy, so long as it is not abused.

HH

Tach time only works for group operated aircraft.
For Commercial operations (pay for hire) hobbs is the way to go.
Hobbs time is equal to clock time while tacho time is not.
Tach time varies with engine load.
You pay for the time you have the aircraft running under it's own power under your control, it's that simple.
You don't complain about being stuck in traffic with a rental car do you?
You bring it back 2 hrs late, you pay for another half day.
That's their rules.
Right, no transponder, no radio, no Nav...and a tacho time higher then Hobbs...big FLAG

Too many sources of time can make us uncertain about which is correct.

Years ago when I first started sailing from the UK to Europe I set one clock to GMT,one to "Eurotime" and one to British summer time.
Boy and did I get into a real muddle,all trips after that I set time on main clock to GMT and used that for all navigation,set wrist watch to local time.
Lister:)

At My school we Log the Hobbs time and them -0.2 to allow for taxi and checks etc so

1.2 on the Hobbs gets charged at 1.0 to the student!