Tacho hours.

[Who has control?]

So how long IS a tacho hour??

Is there a fixed relationship between 1 hour on the tacho & one hour on the clock?

I'm looking at joining a group which quotes hourly rate in tacho hours and I want to get an idea of how much it will cost per hour.

[bertiethebadger]

A Tacho hour can be as long or as short as you make it. In brief, it is a measurement of the engines work rate.

If you fly economically, 1 Tacho hour cah be upto 1.4 chock-chock hours (in a Warrior). It's usually worth slowing down 10kts & saving .1 or .2 per hour.

BtB

[ppl172]

Tacho hour is better if you fly out of a busy airfield and have to wait holding on the ground quite a bit (low engine revs.. tach doesn't clock up as quick).

ppl172

[pistongone]

A tachohour is one hour in minutes at full power,usually around 2600rpm on most american engines in the lower power range!

[Hot Rod]

There is a fixed relation between the clock and the tach but that can differ from one tach to another (by construction).

It can usually be read somewhere on the tach, but not on the scale, have a look on the backside of it.

It should say something like "avg cruise 2292 rpm". That means that if you run the engine at 2292 rpm for one clock hour then the tach will show 1,0.

If you run it faster the tach will show more for one clock hour. Slower than 2292 rpm will show tacho less than 1,0 for one clock hour.

Overhaul on engine and other components is by airborne time, that is what you put in the airplane logbook, clock time between takeoff and landing.

Happy flying:D

[A and C]

check that it is a tacho hour and not an hour on a hobbs because that is another can of worms.

[Grim Reaper 14]

Can you expand those particular worms please? What are the differences between "hours", "tacho hours" and "hobbs hours"? :(

[Polar_stereographic]

Taco is a measure of how many times the engine turns, bit like an odometer on a car is a measure of how many times the wheels turn round. This is usualy a mechanical device.

A hobbs meter usualy starts running when typically either the electrics are turned on or oil pressure is registered. Note, this is irrespective of what the engine is doing. This is usualy an electrical device.

I heard of a hobbs meter on a twin wired up to start when the under carrige was raised. Also heard that a lot of people flew with the wheels down, not unsurprisingly.

HTH

PS

[Cyclic Hotline]

All my fixed-wing machines utilise an airspeed switch, which operates at 40 kts, enabled by the engine oil pressure switch. This ensures that all maintenance activities are related to flight time, and not hanging around on the ramp. There is also another system availalble with an integral tach wired into the gear warning system.

Obviously if you're trying to make money from your aircraft, the more you can charge for sitting at the ramp, the better. We are in the opposite situation, just wishing to base our maintenance operations around actual flight time.

We do not use a Hobbs meter, instead wiring the system directly into an Astrotech digital clock.

All our helicopters utilize a similar system, utilizing an engine oil pressure switch, coupled with squat switches or collective position switches.

Simple, Reliable, accurate.