ENGINE
INSTRUMENTATION
GENERAL
The engine instruments are mounted in two
vertical rows on the center instrument panel
(see Figure 7-8). From top to bottom, these are:
•Pressure ratio
• Exhaust temperature
• Engine rpm
• Fuel flow
• Oil pressure
• Oil temperature
PRESSURE RATIO
Engine pressure ratio, or EPR, is an indication
of the ratio of engine inlet to exhaust gas pres-
sure and provides an indication of the amount
of thrust being produced by the engine.
The EPR system includes two probes in the ex-
haust system, four transducers (two for each
engine) on 23 models and 24 models through
24-180, and 25-003 through -024, and a probe
in the ram-air duct. On all other models, the
inlet air pressure is supplied from the copilot’s
pitot tube, and there is only one transducer per
engine. The inlet and exhaust pressure sig-
nals are sent to the appropriate EPR trans-
ducer where they are converted to electrical
signals, amplified, and sent to the EPR gages
on the center instrument panel.
The EPR system on models 23-003 through 24-
180 and 25-003 through 25-024 requires 26
volts AC. All other models require 115 volts AC.
EXHAUST TEMPERATURE
Exhaust temperature is sensed by eight thermo-
couples in the exhaust system and sent to a cock-
pit gage calibrated in degrees Celsius. The sys-
tem is self-generating and does not require an
electrical power supply.
Figure 7-13. Center Console
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