Arrow Tach and Actual Flying Time

fmmikefmmike
in General Discussion
I am the mechanic for the flying club I belong to. We have 5 Piper Cherokee's. One is a Arrow II (not turbo-charged) I am currently being checked out in the Arrow so I don't have alot of time in it. My club bills flying time by using the Tach. So when someone flys an Archer for lets say 1.5 hours, The Tach time is usually 1.0 or 1.2, so that's what we get billed for. However if you fly the Arrow for 1.5 hours that Tach would be 1.5 or sometimes a little more. So members are complaining that they are being billed for too much time in the Arrow. Everyone thinks there is something wrong with the Tach. We have done some checking and the Tach in the Arrow is the same one that goes in the Archers. Has anyone else experianced something like this? Is it normal? I am pretty sure it has something to do with the constant speed prop on the Arrow vs the fixed pitch on the Archer. Any ideas? ............

Comments

  • flyguydonflyguydon
    Likely they are flying at a higher RPM in the Arrow. TACH time is not "clock time". A tach will hardly move at idle and will go fastest at red line. Funny, but most planes used as rentals etc put in a HOBBS meter to track and bill time flown. They are "clock time" that counts any time where there is oil pressure (engine running).
  • Jim WellsJim Wells
    Be happy they're using Tach time and not Hobbs time. Like Flyguydon says, Hobbs time runs any time the engine is operating. My experience has been that Hobbs time runs about 10% higher than Tach time. Tach time is directly proportional to rpm and is a better representation of flight time. I guess you could save a little by running the Arrow at lower rpm and higher MP.
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