Introduction; Component Expedient Fixes - Bell OH-58A Technical Manual

BDAR FIXES S HALL BE USED ONLY IN COMBAT OR FOR TRAINING
(AUTHORIZED TRAINING FIXES ARE LISTED IN APPENDIX E.)
IN EITHER CASE, DAMAGES SHALL BE REPAIRED BY STANDARD
6-1. DESCRIPTION, POWER PLANT. The
power plant consists of a T63-A-700 on
the OH-58A and a T63-A-720 on the OH-58C
mounted between FS120.O and FS206.0,
Engine connections are
Figure 6-1.
provided for fuel, oil, electrical,
instrument, and engine control systems.
Major sections of the engine are the
air-inlet, compressor, combuster, tur-
bine, and power and accessory gearbox.
All BDAR repairs discussed in this
chapter are applicable to both engine
models.
6-2. ASSESSMENT PROCEDURES. Combat
damage to the engine usually requires
engine replacement.
This section has various
6-4. GENERAL.
which can restore the
expedient fixes
helicopter's mobility in the event of
Engine malfunctions
engine failure.
can be detected from the following
observations:
a. Abnormal oil pressure, temperature
readings, or warning lights.
Abnormal noises or high frequency
b.
vibrations.
c. Sudden loss of power.
CHAPTER 6
POWER PLANT
AT THE DISCRETION OF THE COMMANDER.
PROCEDURES AS SOON AS PRACTICABLE.
Section I.
The logic diagram,
Section II. COMPONENT EXPEDIENT FIXES

INTRODUCTION

Table 6-1, refers to BDAR repair proce-
dures which have been developed.
6-3. REPAIR PROCEDURE INDEX.
Air Bleed Valve Inoperative 6-5
Double-Check Valve
Inoperative . . . . . . . . 6-6
Oil Tank Punctured. . . . . . 6-7
Oil Lines (Rigid) Type
Repair. . . . . . . . . . . 9-7
Fuel, Oil, Pneumatic
Line Repair . . .
6-5. AIR BLEED VALVE
GENERAL INFORMATION:
start-up (or part-speed operation), the
compressor is susceptible to surge due
to high pressure build-up in the rear
stages. An air bleed valve is employed
to discharge the high-pressure air in
order to alleviate the stall condition.
The bleed valve is initially in the open
position and senses pressures between
the fifth stage and the scroll. Once
the stall region is overcome (usually
between 65 percent to 75 percent N1) and
scroll pressure is reached, the valve is
closed. Should the valve not close
correctly, excess air will be dumped at
the compressor and the required burner
pressure will not be obtained resulting
in engine abort.
TM 55-1520-228-BD
PARA.
. . . . . 9-8
INOPERATIVE.
During engine
6-1