What is the equivalent of Hobbs and Tach in a Jet or Turbine Aircraft?
In all of our jets, we have two hobbs meters. One is active from left engine start and the other goes active when the weight of the aircraft leaves the wheels. Neither of these are used for logging our flight time. We do that "chock-to-chock", ie as soon as the chocks are pulled and we start moving to when the chocks are put back in the wheels.

The regs say you can log flight time from when "the aircraft moves under it's own power for the purpose of flight":


  Flight time means:
  (1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing; or
  (2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.