MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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1999 − 2016 by MD Helicopters, Inc.
PITOT − STATIC SYSTEM
MAINTENANCE PRACTICES
1. Pitot − Static System
(Ref. Figure 201 for 369D helicopters,
Figure 202 for 369E/FF helicopters,
Figure 203 - 500/600N helicopters) The
pitot-static system consists of a pitot tube
assembly, a static pressure port installation
and interconnecting tubing and fittings. The
pitot tube, in the lower center of the canopy
panel, is connected to the airspeed indicator by
a nylon line. The static pressure port for the
369D/E/FF series helicopter is located in the
aft end of the engine air intake fairing. The
static pressure ports for the 500/600N series
helicopter are located in the forward canopy
side structure. The ports are connected to the
altimeter. A spring-loaded drain valve is
located at the static line low point aft of
station 127.00 and forward of the instrument
panel on the 369D/E/FF series helicopters. The
static ports are the low point of the system on
the 500/600N, they do not require a drain
valve. A static source crossover line intercon­
nects the altimeter and airspeed indicators.
Do not blow air through pitot-
static system lines without dis­
connecting altimeter and airspeed indicator.
This may result in distortion or rupture of
instrument diaphragm.
2. Pitot − Static System Troubleshooting
(Ref. Table 201)
3. Static Pressure Tube Rework to Minimize
Altimeter Needle Oscillation
(Ref. Figure 204) The hardware connecting the
crossover tube between the altimeter and
airspeed indicators may be reworked to reduce
altimeter indicator needle bounce. The rework
consists primarily of removing the existing
369H6610-3 plug from the connector at the
airspeed indicator and installing a new
369H6610-23 plug in the existing tee at the
altimeter indicator.
(1). Check that all electric power is off.
(2). Remove instrument panel fairing and
hood.
(3). Disconnect drain tube from 369H6628
tee at altimeter indicator.
(4). Press-fit new 369H6610-23 plug into
tee as shown. Reconnect drain tube to
tee (Ref. view B).
(5). Disconnect crossover tube from connec­
tor at airspeed indicator.
(6). Remove existing -3 plug from
369H6610-11 or -21 union assembly.
(7). Reconnect crossover tube to connector
at airspeed indicator.
(8). Reinstall instrument panel fairing and
hood.
(9). Perform flight test to check instrument
operation (Ref. PFM).
A. Weight and Balance Data
Weight and balance are not affected.
4. Pitot Tube Assembly Replacement
(Ref. Figure 201 for 369D helicopters,
Figure 202 for 369E/FF helicopters)
(1). (Slim-Line instrument panels only)
Remove instrument panel fairings and
cover panel from left side to lower
instrument panel support assembly.
(2). (L/H command T-Panels only) Remove
instrument panel fairings.
(3). Remove hardware attaching pitot tube
assembly to structure.
(4). Disconnect pitot line from back of
airspeed indicator, slide aluminum
head end of tube from canopy panel
grommet and remove assembly.
(5). Insert replacement pitot tube assembly
head into place in canopy panel grom­
met and connect pitot line to elbow at
back of airspeed indicator.
(6). Secure tube to structure with removed
hardware.
(7). Check that pitot tube head is aligned
parallel to longitudinal centerline of
helicopter.
CAUTION