MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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95-10-20
Page 203
Revision 7
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Neither this document nor any part hereof may be reproduced or transferred to
other documents or used or disclosed to others for manufacturing or any other
purpose except as specifically authorized in writing by MD Helicopters, Inc.
Copyright
©
1999 − 2016 by MD Helicopters, Inc.
G. Attitude Gyro Indicator
If the presentation of the attitude gyro
indicator does not correspond to the flight
attitude of the helicopter, check the operation
of the search radar, if installed. If the search
radar functions normally, the problem is
probably in the indicator or the wiring. But if
both indicator and gyro-related radar do not
function correctly, then the problem is prob­
ably in the gyro itself, or in wiring from the
gyro. Inspect case and connectors of gyro
indicator, including inspection for puncture or
substantial distortion. If such condition exists,
replace unit(s).
H. Input Voltage
Check for 28 Vdc at terminal board; if voltage
fails to meet specification, troubleshoot further
(Ref. Chap. 96).
I. Attitude Gyro Indicator Maintenance
Practices
(Ref. Sec. 95-00-00, Instruments Inspection
and Instruments Repair)
3. Attitude Gyro Indicator Replacement
A. Attitude Gyro Indicator Removal
(Ref. Figure 201)
(1). Check that all electrical power is OFF.
(2). Remove instrument panel hood and left
and right fairings.
(3). Remove screws from front of indicator.
(4). Disconnect electrical connector from
back of indicator. Remove clamp, then
remove indicator.
B. Attitude Gyro Indicator Installation
(Ref. Figure 201)
(1). Check that all electrical power is OFF.
(2). Position indicator in mounting position
in instrument panel and install clamp.
(3). Connect electrical connector to back of
indicator.
(4). Install screws to front of indicator.
(5). Install instrument panel hood and left
and right fairings.
4. Attitude Gyro Indicator Operational Check
Helicopter must be flown
under visual flight rules
(VFR) conditions at all times when
checking performance of flight instru­
ments.
(1). Verify internal/external lighting works
properly thru panel light dimmer
control.
(2). Check for proper operation of WARN­
ING FLAG with power applied/re­
moved.
(3). Verify that caging (Quick Erect)
operates properly, roll indicator must
align within 2 degrees.
(4). Verify that no objectionable radio or
ICS interference exists due to the gyro.
(5). Recheck magnetic/gyro magnetic
compass accuracy over compass rose
with attitude gyro operating.
(6). Perform a Precession check: Fly aircraft
in a coordinated turn of 180 degrees in
one minute, (15 to 20 degree angle of
bank) at 120 knots indicated air speed,
first in one direction and then in
another. Verify that any resulting bank
or pitch indicating error does not exceed
3 degrees. Note performance of indica­
tor; if indicator tends to flip over, or
does flip over and indicates an opposite
turn, or if when level flight is resumed
the indicator continues to show a
banked attitude, the gyro has precessed
excessively (has malfunctioned) and
must be replaced.
Fly aircraft 60 - 80 knots indi­
cated air speed when perform­
ing pitch and roll check.
(7). Perform a series of pitch and roll
maneuvers not to 20
°
degrees
and -20
°
degrees pitch (total excursion
40
°
degrees), and 60
°
left roll and 60
°
right roll (total excursion 120
°
degrees)
and note performance of attitude gyro
indicator responds appropriately and
does not tumble. If instrument indica­
tion fails to correspond to flown atti­
tudes of aircraft, troubleshoot. (Ref.
Attitude Gyro Indicator Troubleshoot­
ing).
WARNING
CAUTION