Do not respond to the RPM audio and/or warn-
ing light illumination without first confirming en-
gine malfunction by one or more of the other
indications. Normal indications signify that the
engine is functioning properly and that there is a
tachometer generator failure or an open circuit
to the warning system, rather than an actual en-
gine malfunction.
b. F
light Characteristi cs:
(1) Control response with an engine inoperative
is similar to a descent with power.
(2) Airspeed above the minimum rate of de-
scent from autorotational glide characteristics chart (fig-
ure 9-2) will result in greater rates of descent but may
be used as necessary to extend glide distance.
(3) Airspeeds below minimum rate of descent
airspeeds will increase rate of descent and decrease
glide distance.
(4) Should the engine malfunction during a left
bank maneuver, right cyclic input to level the aircraft
must be made simultan eou sly with collective pitc h ad-
justment. If t he collective pitch is decreased without a
correspondin g right cyclic input, the helicopter will pitch
down and roll rate will in crease rapidly, resulting in a sig-
nificant loss of altitude.
c. P
artial Power Condition . Under partial power
conditions, the engine m ay operate smoothly at reduce d
power or it may operate erra tically with inter mittent
surges of power. In instances where a power loss is
experienced without accompanying power surging, the
helicopte r may be flown at reduced power to a suitable
landing area. Under this condition, the pilot should
always be prepared for a complete power loss. In
the event a partial power condition is accompanied by
erratic engine operation or power surging, and flight
is to be cont inued, the throttle may be adjusted in an
attempt to correct the surging condition. If flight is not
possible, close the throttle completely and complete an
autorotational landing.
d. C
omplete Power Los s. Under a complete
power loss condition, delay in recognition of the mal-
function, improper technique or excessive maneuvering
to reach a suita ble land ing area reduces the probability
of a safe autorotational landing. Flight conducted within
the avoid area of the chart (figure 9-3) exposes the
helicopter to a high probability of damage despite the
best efforts of the pilot.
e. L
ow Air speed and Low Altitud e. Under low al-
titude low airspeed conditions, the deceleration capabil-
ity is limited, and caution should be used to avoid strik-
ing the ground with the tail rotor. Initial collective re-
duction will vary after an engine malfunction, dependent
upon the altitude and airspeed at the time of the occur-
rence. For example, collective should not be decreased
when an engine failure occurs at a hover below 15 feet;
whereas, du ring cruise flight conditions, altitude and air-
speed are sufficient for a significant reduction in collec-
tive, thereby, allowing rotor RPM to be maintained in the
safe operating range during autorotational descent. The
rotor may o v e r speed and requ ire collective pitch ap pli-
cation to m a intain the RPM below the upper limit. Col-
lective should never be applied to reduce RPM below
normal limits for extending glide dis tance because of the
reduction in RPM available for use during autorotational
landing.
9-2 Change 14
TM 55-1520-228-10
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