STUDENT GUIDE T-39N/G NATOPS
g. On 1st engine start, EGT, RPM, and fuel flow are available, remaining engine
instruments available once generator on line. Oil Pressure is avail on a cart start but not
with BATT start.
7. Hot Start Characteristics
a. Rapid rise through 475 (not to exceed) or reaching 525.
b. Other factors for hot start include initiating start at a low battery state or low rpm
c. Fuel flow over 600# per hour resulting in improper fuel-air ratio
d. Engine rpm hanging up and failing to accelerate to idle rpm in a normal manner after
8. AIRSTART switch
a. LH ON, RH ON
b. Provides ignition to both igniters.
c. May have to reset DC generator if engine RPM decays below 40%.
d. Airstart switch must be OFF before gen will come on-line.
e. Use starter button to assist airstart if rpm < 10-20% instead of AIRSTART switch.
f. Airstart envelope - max alt 29,000 ft / min airspeed 160 KIAS (see fig 5-4).
G. Bleed Air
1. Fourth-stage interstage bleed valve cycles to preclude compressor instability at low thrust
a. This is known as the bleed strap, and it should close above 80 + 1% rpm. If the bleed
strap does not close, the resulting possibility is undesirable stress in the compressor
section of the engine.
2. High pressure 9th-stage bleed air is for airframes use (pressurization, anti-ice).
3. Bleed air valves controlled by FIRE pull handles and Cabin Air Selector switch.
4. With both engines at the same EPR setting, an interstage bleed valve stuck in the open
position above 80% +1 will be indicated by a higher RPM, EGT, and FF.
H. Fire and overheat detection
1. Continuous element alarm to detect fire (forward engine pod) or overheat (aft engine
2. Detection of fire or overheat results in red light in the FIRE pull handle and an (loud)
alarm bell, accompanied by master caution lights.
3. Limit the fire test to once in any 10 minute period.