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 TM 9-1270-219-13&P
INTRODUCTION
Section
I.
GENERAL.
1.5.
S c o p e . This manual is for your use in operating
of
the
transducers
in
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
Subsystem,
Helicopter
Armament
(Air
Data
Subsystem).
Maintenance
Forms
and
Records. M a i n t e n a n c e
Quality
Assurance/Quality
Control
(QA/QC). To be
forms and records which you are required to use are listed
determined.
and explained in TM 38-750.
Reporting Equipment Improvement Recommend-
Storage.
Instructions
Administrative
for
ations
(EIR). ElR's will be prepared on SF Form 368,
storage
administrative
are
given
in
TM
740-90-1,
Reporting
Quality
Deficiencies.
Instructions
for
preparing
Administrative
Storage.
E l R ' s are provided in TM 38-750, the Army Maintenance
Management System. ElR's should be mailed directly to the
1-4.
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
Island
IL
61299
ATTN
DRSAR-MAO.
A
reply
will
be
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
TABULATED
DATA.
Section
II.
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
Unit)
and
an
Indicator,
Airspeed
and
Direction
(Low
t h e blades. If the tip path plane (TPP) is inclined to the
Airspeed
Indicator).
The
Sensor
Installation
is
also
horizontal
by
an
angle
(i)
the
helicopter
will
have
a
considered
to
be
part
of
the
Air
Data
Subsystem.
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 ( ∝ )
1-2.
For
additional
detail
in
locating
these
to the horizontal.
components
refer
to
TM-55-1520-236/239-10.
1-9.
Function of the Air Data Subsystem (ADS). T h e
b.
The
swivelling
probe
Airspeed
and
Direction
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
functions:
in the horizontal plane:
a.
To
enable
the
Fire
Control
Computer
to
adjust
rocket launch angle for the effects of rotor downwash.
cos
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
vertical
weight,
thrust,
irrespective
of
airspeed
three degrees.
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.
f(V),
ie. the horizontal
c.
Hence
cos
component of the airflow under a helicopter rotor is
c.
It
is
not
possible
for
the
conventional
air
data
function
of
horizontal
aircraft
compound
unique,
s y s t e m , employing a fixed pitot probe and a fixed static
velocity.
vent,
to
provide
the
information
required
for
these
functions.
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
flight
conditions.
the Air Data Subsystem is obtained from a swivelling probe
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