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Figure 1-12. AADS Dimensions.
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TM-9-1270-219-13-P Fire and Flight Air Data Subsystem Helicopter Armament: XM 143 PN 03-004-02 Manual
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Figure 1-13. AADS Block Diagram.
TM 9-1270-219-13&P
AADS
Functional
Description. The
angle
Unit
contains
two
c.
The
Pressure
Transducer
resolvers which measure the head movement in pitch and
e l e c t r i c a l f o r c e b a l a n c e t r a n s d u c e r s secured to a support
y a w are fed with a 400 Hz reference signal from the EPU
f r a m e by means of grommets and bolts, together with a
The
outputs
are
fed
to
the
EPU.
pneumatic connector, a printed circuit board assembly
containing the transducer control electronics and a 54-pin
connector.
a.
Sampling
of
the
resolver
output
signals
is
p e r f o r m e d in the EPU, where the outputs give sine and
d.
The
Analog
Interface
Unit
circuit
card
is
cosine values of the AADS yaw and pitch angles with
connected to the motherboard on the Chassis by a 54-pin
respect to the helicopter.
connector, and the Central Processor Unit circuit card is
c o n n e c t e d with a 90-pin connector.
b. Temperature measurements from the resistive ATS
are made in the EPU, where the constant current source
a n d differential amplifier circuits associated with the ATS
e. The Power Supply Unit consists of a machined
are located.
cast chassis which acts as a heat sink for all dissipating
components, and supports two printed circuit boards and
a 20-pin connector.
c . AADS monitoring is carried out by the EPU and
includes out-of-range tests and sine, cosine compatability
testing. AADS failures are displayed on the EPU front
panel by a ADS BITE indicator.
EPU Functional Description. Airflow pressure
data
are
received
from
the
AADS,
and
converted
into
electronic
data
by
the
Pressure
Transducer
Unit.
Airflow
angle and temperature data are demodulated and monitored
E P U P h y s i c a l D e s c r i p t i o n . The EPU (fig. 1-14)
by
the
Analog
Interface
Unit,
which
also
contains
the
contains seven Shop Replaceable Units, replaceable at
R a d a r Altitude input interface and the A to D converter.
AVIM level. The seven units are the Chassis, Front Panel
All
calculations
and
system
control
functions
are
carried
Assembly, Rear Cover, Pressure Transducer Unit (PTU),
out
by
the
Central
Processor
Unit,
which
is
a
Analog Interface Unit (AIU), Central Processor Unit (CPU)
microprocessor based computing system. Input power from
and Power Supply Unit (PSU). See figure 1-15.
t h e h e l i c o p t e r 28 V d c su p p l y is con v e r t e d a n d re g u l a t e d
into the system voltage requirements by the Power Supply
Unit. A block diagram of the EPU is shown in figure FO-1.
a . An exploded view of the EPU is shown in figure
1 - 1 5 and the dimensions of the unit are shown in figure
The
chassis
and
front
and
rear
covers
are
of
a. P r e s s u r e
Transducer
Unit
(PTU). T h e
PTU
a l u m i n i u m and the unit is secured in the helicopter by
contains two Electrical Force Balance (EFB) transducers
f o u r bolts through cast metal feet. Removal of the rear
t o m e a s u r e t h e S t a t i c ( Ps )
and
Pitot-Static
( Pt- Ps )
cover gives accesss to the PTU, AIU, CPU and PSU. These
pressures. A typical transducer is shown in figure 1-17.
SRUs plug into the motherboard, which is part of the
With their associated control electronics they are capable
front panel assembly, using two part keyed connectors.
of measuring very low pressures with great accuracy. The
When these four SRUs have been removed, the front panel
transducers are temperature-sensitive, and each transducer
assembly, containing the BITE panel and connectors as
characteristic
stored
in
a
temperature
has
its
well as the motherboard, may be removed.
programmable read only memory (PROM) located on the
P T U printed circuit card.
b . All electrical and pneumatic connections are made
(1) Operation of EFB Transducer. The low mass beam
via the front panel. Static and pitot lines are connected to
of each transducer (figure 1-18) is supported by four
standard pneumatic connectors and electrical connections
flexible leaf springs which form a frictionless pivot, whose
are
made
by
a
66-pin
connector.
The
BITE
panel
is
axis is aligned with and attached to a rotary pick-off. The
l o c a t e d on the front panel and contains the LRU BITE
far end of the beam is connected to both a precision
indicators, SELF TEST indicator lamp and switch and
bellows and a forcer coil which sits centrally in a stable
RESET
switch.
1-14

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