Power Plant Instruments; Miscellaneous Instruments; Fuel Quantity Indicator; Voltmeter - Thrush Aircraft S2R–T660 Maintenance Manual

THRUSH AIRCRAFT INC - T660 TURBO THRUSH
AIRCRAFT MAINTENANCE MANUAL

POWER PLANT INSTRUMENTS

This group consists of the oil temperature gauge, oil pressure and fuel pressure gauge, ITT indicator, torque
indicator, propeller RPM indicator, percent gas generator speed indicator, and fuel quantity indicator. These
instruments are operated by fluid pressure, variation in electrical resistance created by a float operated
transmitter, variations in electrical resistance from a temperature probe, and by electrical variations from a
tach-generator. See Figure 8-1 for instrument markings.

MISCELLANEOUS INSTRUMENTS

FUEL QUANTITY INDICATOR

A fuel quantity indicator registers the amount of fuel in the system up to a maximum of 1 64 U.S. gallons. Fuel
from 165 to 230 U.S. gallons is un-gaugeable. The indicator is basically a millivoltmeter that receives input
signals from the fuel quantity transducers (liquid level senders). The face of the fuel quantity indicator is
marked in increments from empty to full. The indicator is used in conjunction with two float-operated variable-
resistance transducers, one installed in each tank. The full tank position of the transducer float produces a
minimum resistance through the transducer, permitting maximum current flow through the fuel quantity
indicator and maximum pointer deflection. As the fuel level of the tank is lowered, resistance in the transducer is
increased, producing a decreased current flow through the fuel quantity indicator and a small pointer
deflection. The fuel quantity indicating system is calibrated by adjusting the fuel quantity transducer float arms
and the indicator as outlined in Section V.

VOLTMETER

A voltmeter displays electrical system voltage when the master switch is on and allows the pilot to monitor bus
bar voltage. Normal voltmeter readings must be within the green arc (24.0 to 30.5 volts). Insufficient voltage or
overcharging is indicated by a lower red arc (minimum) 16.0 to 22.5 volts, and an upper red arc (maximum) 30.5
to 36.0 volts respectively. Continuous operation over 30.5 volts is detrimental to the life of the battery and
could cause loss of electrical power. A yellow arc from 22.5 to 24.0 volts indicates a caution range.

AMMETER

The ammeter displays current flow, in amperes, from the aircraft generator to the battery, or from the battery
to the electrical system. With the engine operating, the ammeter should indicate the on
8 – 7
Effective: 12/17/03