2006-10-26 06:42:21 · 9 answers · asked by LESLIE M 1 in Cars & Transportation ➔ Aircraft
One for the rotor system (transmission, main rotor, and tail rotor in percent RPM).
One or two for the engine.
A sprag clutch allows the rotor to travel faster than the engine on all helicopters during autorotation and shut down.
Piston and single shaft turbine helicopters have a centrifugal clutch that unloads the engine at low RPM for easier starts.
2006-10-26 14:11:01 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The engine and the rotor are not physically linked. The rotor gets it's power from the power turbin which is mounted behind the engine but not connected to the engine itself. So rotor speed and engine RPM are two different animals. Typically the engine should be running between 95 and 100% RPM at all times. The rotor speed will vary with the amount of collective applied. Collective is the amount of pitch on the blades.
2006-10-26 18:37:42 · answer #2 · answered by CatLady 2 · 1⤊ 2⤋
Some do & some don't, it depends on the model & design of the helicopter. Two Tach's means there are two engines. Many helicopters have a separate engine for the tail rotor, as well as an engine for the main rotor.
2006-10-27 06:56:00 · answer #3 · answered by No More 7 · 0⤊ 2⤋
One tach provides a measurement of the Engine speed and the other provides the Rotor speed.
2006-10-26 06:49:34 · answer #4 · answered by iav8_eh 4 · 0⤊ 0⤋
As stated above, one for engine speed and one for rotor speed. Many turbine helicopters have three. Ng for compressor (gas producer) speed, Nf for the free power turbine speed, and Nr for main rotor speed.
2006-10-26 10:39:10 · answer #5 · answered by WildBill846 2 · 2⤊ 0⤋
Because the tail rotor spins at a different speed than the main rotor?
2006-10-26 06:49:40 · answer #6 · answered by jbtascam 5 · 0⤊ 1⤋
main engine speed ,then main rotor speed,some helicopters have two engines
2006-10-29 09:32:00 · answer #7 · answered by drivingfast2 2 · 0⤊ 0⤋
One for the engine and one for the rotor.
2006-10-26 09:19:54 · answer #8 · answered by Bostonian In MO 7 · 1⤊ 0⤋
one for the engine, one for the blades.
2006-10-26 06:49:38 · answer #9 · answered by wrf3k 5 · 0⤊ 0⤋