Originally Posted by
Tinstaafl
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I don't know why many operators don't make use of weight-on-wheels switches - when available - or fit an airswitch to activate a Hobbs recorder. It makes determining TIS sooo much easier.
Charging for the aircraft use is up to the operator. Any method that the users will bear is fair game, although using the same Hobbs that tracks TIS makes things easy. It also removes the price pressure of the user to rush warming & conducting pre-takeoff checks. If renting 'wet' then adding an allowance for fuel used during start & taxi takes care of the - slight - additional cost from that part of the plane's use. Admittedly the catch is that it adds motivation to run the engine hard, but a price penalty based on tacho difference soon stops that behaviour, as do excess fuel consumption surcharges.
Our (Cubair at Redhill) aircraft use Hobbs meters attached to an air switch to record takeoff to landing time. We charge takeoff to landing plus 0.2 (ie 12 mins) to cover taxy time. This system has all the advantages mentioned above but also keeps the headline hourly rate comparable to organisations that charge block to block. Students and renters sometimes log more time than they pay for.