96-50 Annunciator Panel
A push-to-test button on the instrument panel should cause all segments on the annunciator
panel, as well as the ROTOR BRAKE light, to illuminate when depressed. The LOW FUEL
segment takes approximately two seconds before it illuminates due to a time delay in the
circuit. (The time delay prevents sloshing fuel from giving a false indication.) The EMU
segment takes approximately ten seconds to perform a self-test after the battery is switched
ON before it will illuminate. The test button may be used on the ground or in flight to verify
all circuits are functioning.
96-60 Low Rotor RPM Warning Unit Adjustment
The low rotor RPM warning unit is located inside the upper console, mounted to the left vertical
panel. Two magnets attached to the main gearbox tail rotor driveline output yoke provide an
RPM signal for the warning unit's gearbox-mounted Hall-effect senders. When the collective
is at least 0.2 to 0.4 inch (measured at grip) above the full down position and rotor RPM is
95% or less, the warning unit illuminates the Low RPM annunciator segment and sounds two
warning horns. Fully lowering the collective will silence both horns, but will not extinguish
the annunciator segment. The Low RPM annunciator segment and both horns must remain
off above 95% rotor RPM.
To make an adjustment, remove the plastic plug (from a 3/8-inch diameter hole) in the left-
vertical panel exterior. Adjust screw on back of warning unit (2 turns equals approximately
1% change).
96-70 Audio System
A five-place audio system is standard. An audio control panel allows control of communication
radios, intercom, and stereo-capable auxiliary audio (e.g. music) input.
The system has four modes of operation. In normal mode, all occupants hear incoming and
outgoing radio communications, intercom, and auxiliary audio. The pilot and copilot can both
transmit on the selected radio.
In crew mode, the pilot and copilot are isolated from rear seat occupants. The crew does not
hear rear seat intercom or auxiliary audio and rear seat occupants do not hear crew intercom
or radio communications.
In pilot isolate mode, the pilot is isolated from all other occupants. The copilot is grouped with
the rear seat occupants for intercom and auxiliary audio.
In emergency mode, the pilot transmits and receives on the number one radio only (regardless
of audio panel switch position). All other audio is disabled.
The first three modes are selectable via the audio control panel. Emergency mode occurs if
power to the panel is lost. In addition to the mode control, the audio panel has controls for
squelch, volume, and selection of transmit and receive radios. A detail description of these
controls can be found in the audio system operation manual.
Headset jacks are located in the ceiling near each seat. Pilot and copilot intercom and transmit
are controlled via trigger switches on the cyclic grips. The trigger has two detents; the first
detent activates the intercom and the second detent transmits. Additional intercom buttons
are located on the forward side of the rear seats and on the left forward floor. Intercom may
also be set to be voice activated. Auxiliary audio may be plugged in to a jack on the forward
face of the circuit breaker panel. In normal mode, auxiliary audio is automatically muted during
radio communication.
SEP 2012 R66 Maintenance Manual Chapter 96 Electrical System Page 96.7
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