S c o p e . This manual is for your use in operating
the Electronics Processor Unit (EPU) is carried out at depot
a n d maintaining the AH-1S Cobra Fire and Flight Air Data
level. Alignment check of the ADS LRUs is covered in
Chapter 5 of this manual.
Records. M a i n t e n a n c e
(QA/QC). To be
forms and records which you are required to use are listed
and explained in TM 38-750.
Reporting Equipment Improvement Recommend-
(EIR). ElR's will be prepared on SF Form 368,
E l R ' s are provided in TM 38-750, the Army Maintenance
Management System. ElR's should be mailed directly to the
D e s t r u c t i o n of A r m y Materiel to Prevent Enemy
US Army Armament Materiel Readiness Command, Rock
Use. Instructions for destruction of Army materiel to
f u r n i s h e d directly to you.
prevent enemy use will be prescribed in TM 750-244-2.
DESCRIPTION A N D
Components of the Fire and Flight Air Data Sub-
Airspeed and Direction Sensor mounted within the rotor
system, Helicopter Armament (Air Data Subsystem). T h e
downwash. The AADS senses pitot and static pressure and
Air Data Subsystem (ADS), figure 1-1, consists of three
the angle of the air flow relative to the helicopter fuselage
L R U s : a Detector. Wind Direction, Speed and Temperature
(Airspeed and Direction Sensor), a Processor, Signal, Fire
a. The helicopter rotor produces an induced flow
and Flight Air Data Subsystem (Electronics Processor
velocity (v), (v, fig. 1-3) perpendicular to the tip path of
t h e blades. If the tip path plane (TPP) is inclined to the
horizontal air velocity (v) and the local flow at a point (P)
Installation of the LRUs on the helicopter is shown in
under the rotor will be of speed (V) and direction ( ∝ )
to the horizontal.
Function of the Air Data Subsystem (ADS). T h e
ADS provides low airspeed information for two separate
Sensor is placed at P and will sense and ∝. B Y r e s o l v i n g
in the horizontal plane:
rocket launch angle for the effects of rotor downwash.
s in i
D e p e n d e n t on the weight, flight path and airspeed of the
The value of v. sin i is a repeatable function of horizontal
AH-1S, the rotor downwash will deflect rockets by about
speed, sideslip angle, center of gravity position, etc. and
b. To provide information to the pilot on horizontal
d e p e n d s only on ground proximity.
airspeed in forward, rearward and sideways flight which is
accurate to within 4 knots.
ie. the horizontal
component of the airflow under a helicopter rotor is
s y s t e m , employing a fixed pitot probe and a fixed static
d . In the hover the probe senses the induced flow
velocity (V) which is greater than 15 knots in all practical
Principles of Operation. The raw data required by
the Air Data Subsystem is obtained from a swivelling probe