Bell OH-58A Technical Manual page 124

TM 55-1520-228-BD
POWER PLANT
LIMITATIONS: Revised engine start
procedure.
Blocking of the air bleed valve
will render the engine highly
susceptible to surge which could
result in catastrophic damage
to the engine.
PERSONNEL/TIME REQUIRED:
1 Soldier
. 30 Minutes
MATERIALS/TOOLS REQUIRED:
Sheet Metal, 2 X 3 In.,
Thickness 0.032
Sheet Metal Snips
PROCEDURAL STEPS:
1.
Manufacture a blocking plate, Figure
6-2.
2. Loosen three bolts which secure
bleed valve to compressor manifold.
3. Slide blocking plate between bleed
valve and mounting flange.
4. Retighten three bolts which secure
bleed valve to compressor manifold.
Blocking of air bleed valve could
result in catastrophic damage to
The following revi-
the engine.
sions must be incorporated.
5. Complete normal engine start proce-
dure except for the following:
NOTE
Bring engine up to 60 percent N1
and hold for a minimum of two min-
utes. A gradual acceleration is
required to avoid a stall condition.
6-4
a. When increasing fuel to the
engine, grasp the throttle firmly with
both hands and accelerate engine slowly.
b. Monitor TOT and N1 gauges for
possible stall readings.
NOTE
Stall usually occurs between 65
percent and 75 percent N1.
c. If stall is present, TOT will rise
rapidly and N1 RPMs will fluctuate
between 65 percent and 75 percent.
If gauges indicate a stall is pre-
sent, do not overreact. A quick
shutdown of engine will decrease N1
RPMs reducing pressure at the inlet
causing the fire to come forward
through the engine.
d. If gauges indicate stall, hold the
throttle firmly.
RPM, slowly decrease throttle fuel demand.
If stall condition is overcome,
engine must now be run in full
power operation.
6. If engine start is achieved, N1 must
be maintained above 80 percent. Reduc-
tion to part-speed operation could in-
troduce possible stall implications
resulting in engine flameout without
auto-relight capability.
7. Record BDAR action taken. When
mission is complete, as soon as
practical, repair the equipment/system
using standard maintenance procedures.
If N1 does not pickup