TM 1-1520-238-10
8-18
Change 10
Section IV. FLIGHT CHARACTERISTICS
8.32 FLIGHT CHARACTERISTICS - GENERAL.
The safe maximum operating airspeed range is described
in Chapter 5, Section V.
8.32.1 Transient Torque. The AH-64 exhibits a phe-
nomenon (transient torque), that is most evident in
maneuvering flight. This is a result of the change in coeffi-
cient of lift and drag between the advancing and retreating
half of the rotor system being applied by the pilot during
manipulation of cyclic flight controls. In powered flight,
engine torque changes manifested by the rotor system
are evidenced through the ECU/DECU’s response of
directing the HMU to provide either more or less fuel as
appropriate in order to maintain NR. As airspeed, gross
weight, and DA are increased the evidence of transient
torque 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 of
left lateral cyclic, a rapid torque increase will occur fol-
lowed by a decrease in torque.
b. Right cyclic application: with rapid application of
right lateral cyclic, a torque decrease will occur followed
by an even greater increase in torque when left lateral
cyclic is rapidly applied from the right roll condition.
c. Uncompensated rapid cyclic application could
result 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 pilot
can improve helicopter flight characteristics during certain
maneuvers. These are:
8.33.1 NOE/APPR Mode.
If the pilot desires to improve
his over-the-nose visibility for landings or during NOE
flight, the NOE/APPR mode may be engaged at any time.
An additional benefit is improved forward speed control in
NOE flight.
8.33.2 Manual Mode.
The manual mode of operation is
useful for positioning the stabilator to help minimize air-
frame vibrations when hovering in crosswinds or tail-
winds.
8.34 SLOPE/ROUGH TERRAIN LANDING.
CAUTION
Care shall be exercised when operating
the helicopter on rough terrain. Damage
to the underside antennas may result.
For slope landings and all ground operations, avoid using
combinations of excessive cyclic and low collective set-
tings. Where minimum collective is used, maintain cyclic
near neutral position and avoid abrupt cyclic inputs. If cy-
clic pitch is required, increase collective slightly to avoid
hitting the droop stops and possible rotor-blade-to-fuse-
lage contact.
