helicopter Forward Flight

helicopter Forward Flight

•  In steady forward flight with no change in airspeed or vertical speed, the four forces of lift, thrust, drag, and weight must be in balance.
• Once the tip-path plane is tilted forward, the total lift-thrust force is also tilted forward. This resultant lift-thrust force can be resolved into two components—lift acting vertically upward and thrust acting horizontally in the direction of flight.
•  In addition, to lift and thrust, there is the weight (the downward acting force) and drag (the force opposing the motion of an airfoil through the air).
•  In straight-and-level (constant heading and at a constant altitude), unaccelerated forward flight, lift equals weight, and thrust equal drag.

• If lift exceeds weight, the helicopter accelerates vertically until the forces are in balance; if the thrust is less than drag, the helicopter slows until the forces are in balance.
•  As the helicopter moves forward, it begins to lose altitude because the lift is lost as thrust is diverted forward.
• However, as the helicopter begins to accelerate, the rotor system becomes more efficient due to the increased airflow. The result is excess power over that which is required to hover.
• Continued acceleration causes an even larger increase in airflow through the rotor disk and more excess power. In order to maintain unaccelerated flight, the pilot must not make any changes in power or in cyclic movement. Any such changes would cause the helicopter to climb or descend.
•  Once the straight-and-level flight is obtained, the pilot should make note of the power (torque setting) required and not make major adjustments to the flight controls.