User manual

DodoSim 206 FSX User Manual

Page 65

cushion the final touchdown. When performed incorrectly and the collective is lowered too far, the

helicopter can end up oscillating in altitude as the pilot over-controls by first decreasing collective and

then reapplying it.

Note that at high altitude the helicopter may not have enough power to hover without over-torquing.

Always ensure you have adequate excess thrust required for hovering before landing. Alternatively, a

running take off can be attempted where the terrain permits, allowing the helicopter to reach

translational lift speeds, (see 4.1.4.1”Transition from the Hover into Forward Flight”), before becoming

fully airborne. Anti-torque input, (left pedal), also consumes engine power. To escape an enclosed

space such as a small clearing, it is possible to gain approximately 5% more available torque by

reducing the power consumed by the tail by reducing the left pedal input to perform a right turn.

4.1.3.3 Using the Anti-Torque “Rudder” Pedals

The primary function of the tail rotor is to oppose the twisting “torque” force generated when the engine

turns the rotors that tries to turn the fuselage in the opposite direction. Since there is no aerodynamic

opposition to this applied by the vertical stabiliser during a hover, the pilot must oppose the torque-

induced yaw using significant left pedal input to increase the pitch of the tail rotor blades and generate

equal and opposing thrust to the torque action.

Complicating matters even further, as the pilot adjusts the collective lever to maintain constant height,

the torque-induced yaw strength changes accordingly and the pilot must simultaneously adjust his

countering pedal input if the aircraft is to remain pointing in a constant direction. Until this response is

perfected, holding a steady heading whilst increasing or decreasing altitude with the collective will be

difficult. Additionally, pedal input also changes the load on the engine, which in turn increases or

decreases the torque. An increase in left pedal input consumes power and the helicopter will descend,

so the pilot must increase collective slightly to compensate and vice-versa.

Due to the faster speed and lower inertia of the tail rotor blades, response to pedal input is a lot more

immediate than that for the main rotor’s collective pitch. Precise and smooth pedal control is required.

Over-controlling the tail will result in jerky heading changes and sickness in your passengers.

Pilot Information: Aggressive use of the pedals may result in wear to the tail rotor gearbox and may

eventually result in a failure, where all tail rotor thrust is lost and you are unable to counter torque-

induced yaw at low speeds.

As the forward airspeed increases, the vertical stabiliser develops aerodynamic forces which opposes

the torque-induce yaw, and so the pilot can slowly relax his pedal input to the point where little or none

is required at normal cruising speeds.

4.1.3.4 Dealing with Wind

Like the brass cockerels often seen adorning church spires, helicopters like to “weathervane” into the

wind. Holding a steady heading away from the direction of the wind in a hover can be a difficult task.

More or less pedal input than normal will be necessary to maintain heading and in very strong winds the

helicopter may completely lack the tail authority (thrust) to do this.

Performing a spot turn in wind requires careful co-ordination of the controls.

Pilot Information: Hovering should be avoided in side or rear winds greater than 17 Knots.

4.1.4 Forward Flight

4.1.4.1 Transition from the Hover into Forward Flight

To transition from the hover into forward flight, the cyclic must be pushed forward to deflect part of the

rotor thrust. Since in a steady hover the rotor is generating exactly enough thrust to maintain a constant

height, if some of this thrust is now deflected to provide forward acceleration, the remaining thrust is