On Tuesday, 8 March 2016 20:56:51 UTC+2, Steve Leonard wrote:
Another flaw with charging by time is those towpilots that want to "build time" or take longer to get back after the glider gets off, or keep on climbing even after the glider released, etc. No system will be perfect.

Going a bit OT now but:
Billing on time (Hobbs or stop watch) isn't perfect but it's the closest way to bill according to the operating cost of a tug. The more engine time on the tug the higher the fuel cost and the shorter the inspection/maintenance intervals.

We don't have problems with tug pilots trying to "build time" and in any case time based fees are a great deterrent to people dawdling. If the glider pilot get's a massive aerotow charge he will make sure that the tug pilot doesn't decide to do any short cross country flights at his expense again. With a height based fee structure a 2000 foot tow could take 5 minutes or 30 minutes depending on the tug pilot and in the end the club would carry the cost.

Time based also means that the glider pilot can release any time he has a thermal so quite often a 4 to 5 minute aerotow is all that is required and costs the glider pilot about $14 USD. Most tows are around 8 minutes long (~2000 feet AGL) and cost about $23 USD (and I'm at one of the more expensive clubs in South Africa).