Hobbs time and Tach time & hourly flying prices in Europe

I retrieved a good description of the difference between Hobbs and Tach time which I like to share over here

Hobbs Time
Hobbs time Cessna

In most planes, the Hobbs clock is started and stopped based on an oil pressure switch, so it starts when the engine starts, and stops when the engine is shut-down. While it’s running, it just ticks off a tenth of an hour every 6 minutes, based on “regular wall clock time”. So a tenth of idling on the ramp is the same as a tenth at cruise.
My Belgian flying club Limburgse Vleugels (Zwartberg, EBZW) bills its members Hobbs time.
The current hourly rates are:
Cessna’s 152: 120€/hour
Cessna 172 (classic): 150€/hour
Cessna 172 SP with G1000: 180€/hour
Mooney M20J: 210€/hour

Tach Time
Tach time Cessna

The tach clock isn’t really a clock at all, it doesn’t actually measure time, it really measures engine revolutions. But it’s calibrated such that a tenth of an hour of tach time is clicked off when the engine is at cruise RPM for 6 minutes. In other words, if the plane is at cruise RPM, the tach clock will be clicking off tenths of an hour at the same rate as the Hobbs clock, and the same as the watch on your wrist. But if the engine is idling at an RPM speed that’s half of what cruise RPM is, then the tach clock will be running at half the speed of the Hobbs clock.
My Luxembourg flying club AéroSport (ELLX) bills its members Tach time.
The current hourly rates are:
Cessna 172 (classic): 149,3€/hour
Cessna 172 SP with G1000: 180,07€/hour
Piper PA28: 149,31€/hour
Cessna 182 Q: 241€/hour
Cessna 182 RG: 281,77€/hour
Twin Engine Piper PA44: 327,6€/hour
Relation
So, for the tach clock, less “time” is clocked when the plane is idling on the ramp, or flying at low RPM. For short flights (where ramp idling time is a significant percentage of total time), and flights where you’re doing a lot of pattern work (and thus operating at low RPM), tach time will be significantly less than Hobbs time, which is the case in Luxembourg. In general, one can say that when I fly an hour on a Cessna 172 classic in Luxembourg, I have 0,9 Tach time, meaning that I have to pay 135€ for the plane, whereas in Zwartberg, the same flight will cost me 150€. But with the due landing fee of 6€ in Luxembourg (as we use the intl. airport), we end up paying 141€ for flying an hour in Luxembourg

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