Advanced time keeping
I did look at a few options when moving from the take off to landing charging via the log books.
The Hobbs run by the master switch just encourages people to rush, both checks and not letting the engine get warm before take off.
Hobbs run by an airspeed switch was an option but cost to install was an issue.
GPS glider loggers are an interesting idea but instatalation was an issue.
There was a very interesting option of a combined GPS logger that sent the flight info via the mobile phone network to the club accounting system, for this system the providers charged a small fee for each transaction, while being the best system technically and one that I would have fitted if I was running 20 aircraft the administration costs for three aircraft did not justify the cost. But as an aircraft owner the prospect of the charge for the flight being extracted by direct debit from the pilots bank account milliseconds after the master switch is turned off is very attractive !
In the end aircraft engine Tacho time won the day with those who use the aircraft consideratly being at a slight advantage with those flying at high power paying more, with no installation costs this seems to have solved the problems of HH:MM arithmetic errors by replacing it with decimal arithmetic.