STUDENT GUIDE T-39N/G NATOPS
UNIT ONE: ENGINES
REFERENCE: T-39 NATOPS MANUAL
Locate and operate T-39N/G aircraft systems, given a mission in a T-39 in accordance with
A.1.2 Recall the basic description, related systems, and operating limitations of the JT12A-8A gas
turbine engines in the T-39N/G.
NATOPS ONE: ENGINES
A. Pratt and Whitney JT 12A-8A.
1. A turbo jet engine mixes incoming air with fuel, ignites the mixture and creates thrust.
All incoming air passes through the combustion chambers.
2. Air is compressed by a single rotor, nine-stage, axial-flow compressor that is driven by a
two-stage reaction turbine.
& DC generators, oil pump, fuel control and engine driven fuel pump.
3. The air then passes into a can-annular combustion chamber.
a. The combustion chamber contains 8 burner cans in which the fuel is injected
through a single, dual orifice nozzle mounted at the inlet of each can.
b. Two igniters, one each in the No. 3 and No. 6 cans, ignite the fuel/air mixture.
Initially, this spreads to all burner cans through flame tubes, and is then self-
4. The hot expanding gas drives the two-stage turbine before being exhausted as thrust.
1. Rated at 3300# takeoff thrust at sea level.
2. Engine Pressure Ratio (EPR) is the primary reference for setting thrust, provided RPM
and EGT are not exceeded.
3. FF, EPR, oil pressure, and fuel quantity gauges need electrical power; RPM and EGT are
self-generating through the accessory gearbox.