Dupre,
It is quite common for NZ aircraft operators to charge their a/c out on an electric Hobbs meter. Obviously requiring electric power to operate, turning off the MASTER will stop the Hobbs meter working.
Years ago it used to be Tacho charging, but they worked out that the pilots were getting 15-20% more flight time than chargable tacho time, due lower rpm in circuits in particular. Then they went to the Hobbs which were from memory oil pressure operated (and increased the hourly rate to make up for the time not charged due insufficent oil pressure to activate the Hobbs) and came close to ripping off the student but not quite, so they then went to electric Hobbs which started charging from the moment you turned on the master (without altering the hourly rate I might add).
So for those students thinking that I'll get the ATIS etc before starting to save money...then you are mistaken.
They tried or are in the process of trying to use electric Hobbs for twins instead of airswitch Hobbs, which bodes the question about money sensitive students hurrying up things on the ground prior to getting airborne and possibly forgetting something critical.
As to how they found out - they (AFS) probably found a discrepency with the Tacho times (which is uneffected by electrical power) remembering he flew something like 2.7 hours and recorded only 1hr for charging, adding 15-20% to the tacho time will give you an approx. hobbs time, then they checked his logbook for the flight entry and he had obviously entered the full flight time.
S2K