MD Helicopters 369 Series, Manual

Page: 55 / 110

CSP−HMI−2
MD Helicopters, Inc
.
MAINTENANCE MANUAL
28−25−00
Page 1
Revision 39
ANTI − ICE/AIRFRAME FUEL FILTER
DESCRIPTION AND OPERATION
Table 1. Anti − Ice/Airframe Fuel Filter Effectivity
Installation Model & Production Number Features
369H90022 − BSC 369D, 003 and subsequent Helicopters equipped with slimline instrument panel.
369H90022 − 503 369E, 001 and subsequent Helicopters equipped with T − instrument panel.
369H90022 − 503 500N, 001 and subsequent Helicopters equipped with T − instrument panel.
600N98110 − 501 600N, 003 and subsequent Helicopters equipped with T − instrument panel.
NOTE: Anti − ice / airframe fuel filter is not certified for installation on C30 engine installation.
NOTE:
On the 600N helicopter, the airframe
fuel filter is not certified as an anti−ice fuel
filter. Throughout this section, the airframe
fuel filter will be refered to as an anti−ice
fuel filter.
1. Description
(1). The airframe mounted anti−ice fuel
filter is installed on the aft face of the
firewall upstream of the engine fuel
pump filter. The 10 micron, 500 square
inch disposable filter element strips ice
and other solids from the fuel before it
enters the engine fuel system.
2. Operation
(1). A flow pressure sensing switch in the
filter body furnished with all installa-
tions closes when flow differential
pressure across the filter drops to a
preset level.
(2). On the 369H90022−BSC installation,
pressure switch contact closure directs
28Vdc current across the S2 contacts of
the
FUEL FILTER relay K254 to
activate the RT170−277 time delay
relay (TDR). The TDR energizes relay
K254 after a two to five second delay,
closing switches S1, S2, and S3;
energizing the
FUEL FILTER caution
light, start pump and START PUMP
ON light.
(3). On 369H90022−503, −505 and
600N98110−501 fuel filter installations,
pressure switch closure only advises the
pilot of an impending or total fuel filter
blockage by lighting the
AIRFRAME
FILTER caution lamp in the caution/
warning panel. The pilot must manual-
ly set the
START PUMP switch ON to
pressurize the fuel system.
(4). On all installations, total filter blockage
forces a filter bypass valve in the filter
body open to second supply unfiltered
fuel to the engine.
(5). Pressing the FUEL FILTER caution
light/switch supplied with
369H90022−BSC installations resets
relay K254 and the time delay relay,
shuts down the start pump and
START
PUMP ON light and switches off the
FUEL FILTER caution light.
(6). The caution light dimmer switch on the
lower left control panel of −BSC
installations controls only
FUEL
FILTER caution light intensity with
DIM or BRT positions. FUEL FILTER
caution lamp test is executed with the
PRESS TO TST WARN LT switch on
the caution/warning light panel.
(7). On −503, −505 and −501 installations,
caution light intensities, including the
AIRFRAME FILTER light are
controlled through the WARN LT DIM
potentiometer on the pedestal switch
panel.
(8). Circuit protection is provided by the 7.5
ampere anti−ice FUEL FILTER circuit
breaker on the anti−ice fuel filter panel.