A few notes on flying this bird that you should keep in mind:
Ground effect
Ground effect is a condition of improved performance found when hovering near the ground. The effect begins to occur when hovering at an altitude equal to approximately the radius of the main rotor (5-10 m for most helicopters) and increases as altitude decreases.
The improved lift and airfoil efficiency while operating in ground effect is due to a number of effects. First, and most importantly, the main rotor-tip vortex is reduced. When operating in the ground effect, the downward and outward airflow reduces the vortex. A vortex is an airflow rotating around an axis or center. This makes the outward portion of the main rotor blade more efficient. Reducing the vortex also reduces the turbulence caused by recirculation of the vortex.
The second important factor is a reduction in the downwash airflow velocity by the ground, which produces a zone of increased air pressure below the helicopter. This affects the rotor system and increases lift. The maximum lift coefficient produced by
ground effect at zero altitude is 1.2.
Translational lift
The efficiency of the hovering rotor system is improved by each knot of incoming wind gained by forward motion of the helicopter or by a surface headwind. As the helicopter moves forward, fresh air enters in an amount sufficient to relieve the hovering air-supply problem and improve performance. At approximately 40 km/h, the rotor system receives enough free, undisturbed air to eliminate the air supply problem. At this time, lift noticeably improves and the helicopter begins to climb. This distinct change is referred to as translational lift. At the instant of translational lift, and as the hovering air supply pattern is broken, dissymmetry of lift is created.
As airspeed increases, translational lift continues to improve up to the speed that is used for best climb. In forward flight, air passing through the rear portion of the rotor disc has a higher downwash velocity than the air passing through the forward portion. This is known as transverse flow effect. This effect, in combination with gyroscopic precession, causes the rotor to tilt sideward and results in vibration that is most noticeable on entry into effective translation.
Autopilot:
The four-channel electrical-hydraulical autopilot system is designed to stabilize the helicopter in roll, pitch, heading, altitude, and airspeed. The autopilot is a system, receiving information about changes in angular positions of the helicopter, barometric altitude and instrumental airspeed. It has four independent autopilot channels, controlling corresponding helicopter’s controls:
yaw channel – tail rotor pitch;
roll channel – swashplate in lateral direction;
pitch channel- swashplate in longitudinal direction;
altitude channel – main rotor pitch;
When the altitude channel is engaged, the pitch channel receives correction signals from the airspeed correction unit to stabilize the airspeed. The four autopilot channels (roll, pitch, yaw, altitude) provide:
stabilization of helicopter’s position in three axes (longitudinal, lateral,vertical);
stabilization of altitude, during sustained level flight and hover;
stabilization of indicated airspeed.
In case of automatic helicopter stabilization, the actuating rods of the combined hydraulic boosters can move themselves within 20% of their full travel range, wherein control sticks (cyclics) do not move and are hold in the same fixed positions by the spring load mechanism. Collectives are hold by the friction mechanism. Limitation of 20% (by design of steering units/ control actuators) of full travel range of is needed to provide flight safety in case of autopilot failure, because the most of the failures are accompanied with appearance of an one-way signal on the autopilot output and, as a result, fast reaction of the actuator units.
At the same time, this limited operating range of actuator units using autopilot signals is sufficient for compensation of real-life distrubances, affecting helicopter and for stabilization of angular positions of the helicopter. The pilot may intervene at any time while the autopilot is engaged. When pilot intervene roll or pitch, it is necessary to remove impact of signals from angular and angular velocity sensors on hydraulic boosters of roll and pitch channels. For this purpose the compensation sensors, kinematically connected with lateral and longitudinal controls, which provide signals, equal to ones received from attitude indicator, but with opposite sign, are installed. In other words, when pilot moves cyclic, the reference value of roll and pitch (which autopilot will maintain) is constantly being updated. In this way pilot controls helicopter’s roll and pitch, without disengaging autopilot, which is constantly trying to maintain helicopter’s position, given by the pilot. For the pilot, to control yaw, on the pedals are triggers and microswitches, which, when pressed, enable alignment mode for yaw channel. When maneuver is finished and pedals are released, the autopilot for yaw channel engages automatically.
Trim:
After pressing the MISC_1 trimmer button, the cyclic remains in the same position, where it was at this moment, and the following changes in joystick’s position have no impact on cyclic, until player return his joystick to the center position (with some margin). After that deflection of the joystick will be added to the current position of cyclic (latest trimmed position). To reset cyclic trimmer, player must use the MISC_2 button.
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Topic: Hip & Hind Progress - 3d artist help needed (Read 17886 times)
