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AERODYNAMICS REVIEW. This is a basic review of aerodynamic factors listed in the Primary Instructor Pilot MOI. DYNAMIC ROLLOVER.
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AERODYNAMICS REVIEW This is a basic review of aerodynamic factors listed in the Primary Instructor Pilot MOI.
DYNAMIC ROLLOVER Dynamic rollover is the occurrence of a rolling motion; while any part of the landing gear is acting as a pivot, which causes the aircraft to exceed a critical angle, roll over, and recovery is impossible.
SETTLING WITH POWER Settling with power is a condition of powered flight in which the helicopter settles in its own downwash. Conditions conducive to settling with power are a vertical or near-vertical descent of at least 300 feet per minute, low forward speed and using some of the available engine power (20-100 percent )with insufficient power to retard the sink rate. Normally, increasing airspeed is the preferred method of recovery. Usually less altitude is lost by this method than by the method of lowering collective. The two methods may be combined if altitude permits.
DISSYMMETRY OF LIFT In forward flight, the combined effects of the differential airflow across the advancing and retreating blades and the three no-lift areas on the retreating blade result in a dissymmetry of lift potential between the advancing and retreating halves of the rotor disk. Blade flapping alone or in conjunction with cyclic feathering can eliminate dissymmetry of lift and allow the pilot to maneuver the helicopter.
TRANSLATING TENDENCY The tendency of the single-rotor helicopter to move laterally during hovering flight. It is compensated for by one or more of the following: Flight-control rigging. Transmission tilted slightly to the left. Collective pitch control system. Pilot inputs to control drift.
TRANSVERSE FLOW EFFECT Because of coning and the forward tilt of the rotor system, there is a differential airflow across the front and rear halves of the rotor disk.
RETREATING BLADE STALL A stall of the retreating blade that begins at or near the tip because of high angles of attack required to compensate for dissymmetry of lift and the three no-lift areas. Conditions most likely to produce blade stall are: High blade loading (high gross weight). Low rotor RPM. High density altitude. Steep or abrupt turns. Turbulent air. Recover from blade stall Reduce power. Reduce airspeed. Reduce the severity of the maneuver. Increase RPM. Check pedal trim.
TOTAL AERODYNAMIC FORCE As airflow flows around an airfoil, a pressure differential develops between the upper and lower surfaces. The differential, combined with the resistance of the air to the passage of the airfoil, creates a force on the airfoil. This force, is known as total aerodynamic force, is represented by a vector. Total aerodynamic force acts at the center of pressure on the airfoil and is normally inclined up and to the rear.
TOTAL AERODYNAMIC FORCE Total aerodynamic force may be divided into two components called lift and drag. Lift acts on the airfoil in a direction perpendicular to the relative wind. Drag acts on the airfoil in a direction parallel to the relative wind and is the force that opposes the motion of the airfoil through the air.
AIRFLOW IN FORWARD FLIGHT Differential velocities around the rotor systems as a result of forward speed
CONCLUSON This has been a review of the items listed in the Primary Instructor Pilot MOI. Please address any questions you have by reviewing Fundamentals Of Flight, FM 1-203 (dated October 1988) or speaking to one of the Primary MOI/QC instructors.
