TM 1-1520-238-108-18Change 10Section IV. FLIGHT CHARACTERISTICS8.32 FLIGHT CHARACTERISTICS - GENERAL.The safe maximum operating airspeed range is describedin Chapter 5, Section V.8.32.1 Transient Torque. The AH-64 exhibits a phe-nomenon (transient torque), that is most evident inmaneuvering flight. This is a result of the change in coeffi-cient of lift and drag between the advancing and retreatinghalf of the rotor system being applied by the pilot duringmanipulation of cyclic flight controls. In powered flight,engine torque changes manifested by the rotor systemare evidenced through the ECU/DECU’s response ofdirecting the HMU to provide either more or less fuel asappropriate in order to maintain NR. As airspeed, grossweight, and DA are increased the evidence of transienttorque becomes more pronounced. Pilots should coordi-nate lateral cyclic applications with the appropriate collec-tive application to prevent exceeding aircraft limitations.Examples of transient torque in forward flight:a. Left cyclic application: with a rapid application ofleft lateral cyclic, a rapid torque increase will occur fol-lowed by a decrease in torque.b. Right cyclic application: with rapid application ofright lateral cyclic, a torque decrease will occur followedby an even greater increase in torque when left lateralcyclic is rapidly applied from the right roll condition.c. Uncompensated rapid cyclic application couldresult in any of the following: dual or single engine over-torque, low rotor (NR), NP droop, or loss of altitude.8.33 STABILATOR OPERATION.The stabilator is normally operated in the automatic mode.However, the two additional modes available to the pilotcan improve helicopter flight characteristics during certainmaneuvers. These are:8.33.1 NOE/APPR Mode.If the pilot desires to improvehis over-the-nose visibility for landings or during NOEflight, the NOE/APPR mode may be engaged at any time.An additional benefit is improved forward speed control inNOE flight.8.33.2 Manual Mode.The manual mode of operation isuseful for positioning the stabilator to help minimize air-frame vibrations when hovering in crosswinds or tail-winds.8.34 SLOPE/ROUGH TERRAIN LANDING.CAUTIONCare shall be exercised when operatingthe helicopter on rough terrain. Damageto the underside antennas may result.For slope landings and all ground operations, avoid usingcombinations of excessive cyclic and low collective set-tings. Where minimum collective is used, maintain cyclicnear neutral position and avoid abrupt cyclic inputs. If cy-clic pitch is required, increase collective slightly to avoidhitting the droop stops and possible rotor-blade-to-fuse-lage contact.
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