7 - 4 6 . MARKINGS FOR HELICOPTERS
b. NON CALIBRATED ROTOR SCALE. To locate
a.
a particular rotor speed on a universal type dual
(1) ROTOR.
tachometer on which the rotor scale is not
calibrated, use the following procedure.
(2) GREEN ARC. Indicates rotor rpm range
during powered flight. The bottom of this arc
(1) Find the speed on the engine scale cor-
describes minimum rotor rpm for continuous
responding to the desired rotor speed point by
flight. The top of this arc indicates maximum
multiplying the desired rotor speed by the engine
rotor rpm with power.
rotor gear ratio of the particular aircraft.
(3) RED RADIAL. Indicates maximum per-
(2) Draw a line from the engine speed point
missible autorotative rpm.
on the engine scale, as determined above, to the
center of the dial. The point where this line
(4) RED ARC OR RADIAL. May be used to
crosses the rotor scale is the desired rpm point on
show regions of prohibited operation because of
that scale.
dangerous vibration or similar reasons.
(3) The above procedure can be used to
(5) ENGINE.
locate any point on the rotor scale. The reverse of
this procedure can be used to determine the rpm
(6) RED RADIAL. Indicates maximum rpm.
value of any point marked on the rotor scale.
