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The information disclosed herein is proprietary to MD Helicopters, Inc.Neither this document nor any part hereof may be reproduced or transferred toother documents or used or disclosed to others for manufacturing or any other

purpose except as specifically authorized in writing by MD Helicopters, Inc.Copyright19992013 by MD Helicopters, Inc

ENGINE AIR PARTICLE SEPARATOR

DESCRIPTION AND OPERATION

1. Description and Operation

(Ref. Figure 1)

(1). MDHI 369/500 helicopters may beequipped with an optional engine inletair particle separator filter installationin place of the standard engine air inletscreen.

(2). Later model helicopters are equippedwith a Aircraft Porous Media (APM)filter. Earlier 500D helicopters werefitted with a Donaldson particleseparator. The APM unit is equippedwith provisions for an optional mist

eliminator installation.(3). Both the APM and Donaldson particle

separators are installed inside the frontof the aft intake fairing above theplenum chamber and utilize the sameoperating principle. The particleseparator installation consists of vortextubes, a collection chamber, a nozzlemanifold, ejectors, flapper valve, sealsand attaching hardware. A scavenge airsystem is used to remove trappedparticles from the collection chamber

with engine bleed air. The scavenge airsystem consists of a solenoid air valve,tubes, an air pressure switch, SCAV

AIR circuit breaker switch, AIRFILTER CLOGGED caution light,wiring, and attaching hardware. An airbypass door system is included to allowthe particle separator to be bypassed inthe event the unit becomes clogged. Theair bypass door system includes ahinged plenum chamber door, doorlatches, door actuating forward and aftcables, cable return spring, two retain-

ers, three cable pulleys, adjustablecable stop, handle and attachinghardware.

(4). An optional mist eliminator may befitted to the back of APM separators tofilter liquid sprays out of engine inletair. Nine self retaining bolts secureearly mist eliminator installations tothe aft face of the particle separator.

Later installations feature a system ofclips that retain the mist eliminator insealed contact with the particle separa-

tor. The mist eliminator consists of awelded stainless steel frame and wiremesh screens on the fore and aft faces.

(5). Air drawn through the particle separa-tor by the engine passes through theparallel vortex tubes. Each tube isfitted with vanes and an opening to theparticle collection chamber. The vanesspin the incoming air so that centrifu-gal force separates heavier solid bitsfrom the air flow. A smaller diametertube directs particle free center vortex

tube air through the collection chamberrear plate into the plenum chamber.

When the scavenge air system isswitched ON, trapped particles aredrawn out of the collection chamber byscavenge air vacuum and dischargedoverboard through an opening in theright side of the aft inlet fairing of APMequipped helicopters and the left sideon Donaldson equipped machines. Thenozzle manifold is fitted with an enginebleed air inlet port and air jets todischarge contaminants. The ejector

assembly consists of a mounting flangewith tubes, duct assembly and flappervalve.

(6). The scavenge air system is suppliedcompressor bleed air controlled by thesolenoid air valve. Bleed air is deliveredto a ductmounted nozzlemanifoldthat ejects contaminants from theparticle separator. The electricallyactuated solenoid air valve is mountedon the left forward side of the Station124.00 bulkhead. The valve is con-

trolled by the SCAV AIR circuit breakerswitch on the instrument panel.

(7). An increase in plenum chambervacuum (reduced plenum chamberpressure) caused by reduced airflowthrough a clogged filter/mist eliminatoris sensed by a differential pressureswitch ported to the plenum chamberand particle separator inlet. Sufficient
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pressure differential causes the switchto close. Switch closure lights an AIRFILTER CLOGGED caution indicatoron the instrument panel. A cableactuated filter bypass door on theplenum chamber wall may be opened bythe pilot to allow the engine to operate

on unfiltered air.

(8). Pulling the FILTER BYPASS CON-TROL handle in the crew compartmentdisengages two door latches inside theengine air inlet aft fairing and opensthe door inward. A spring and two

retainers on the aft end of the forwardcable returns the handle to the stowedposition. An adjustable stop providesfor cable travel adjustment and airbypass door rigging.

On 500N installation, the FILTERBYPASS CONTROL handle in the crewcompartment disengages one door latchinside the air inlet aft fairing and opensthe door inward. Adjustment of thiscable installation is limited by reposi-tioning the cable assembly.

Table 1. Engine Air Particle Separator Configurations

Model Part Number Cabin Heat Principal Features

500N 500N901483500N901481

NoYes

APM filter with new pressure switch and Tpedestal electricalinstallation.

530FF 369H90148543369H90148541369H90148529369H90148527

NoYesNo

Yes

APM filter with generic wire harness and no cabin heatAPM filter with generic wire harness and cabin heatAPM filter with new pressure switch and Tpedestal electricalinstallation.

500E 369H90148545369H90148539369H90148537369H90148535369H90148521369H90148519

YesNoNo

YesNo

Yes

APM filter for C20R engine with generic wire harnessAPM filter for C20R engine with generic wire harnessAPM filter for C20B engine with generic wire harnessAPM filter for C20B engine with generic wire harnessAPM filter with Tpedestal electrical installation.

500D 369H90148

509369H90148507 NoYes APM filter with electrical controls bracket on side of slimline pedestal.

369H90148505369H90148503

NoYes

Donaldson filter with electrical controls bracket on side of slimlinepedestal. No mist eliminator option.

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G71-1000-1A

TYPICALFILTERFUNCTION

(VIEWL

OOKINGDOWN)

Figure 1. Particle Separator Operating Principle Early Type (Donaldson Unit)

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FILTERED

AIRTO

ENGINE

AIRINLET

CONTAMINATEDAIR

TOSCAVEN

GEEJECTOR

SWIRL

GUIDES

FILTERSCREEN

PLENUMCHAMBER

ACCESS(FILTER

BYPASS)DOOR

NORMALLYCLOSED

TOENGINE

AIRINLET

AIR

FILTER

CLOGD

INDICATOR

LIGHT

FILTERBY-PASSCON

TROL

PULLHANDLEFW

D

PULLHANDLE

SWIRLGUIDES FIL

TERTUBEDETAIL

VIEW

TYPICALFILTERFUNCTION

AIRPRESSURESWITCH

(PRESSUREACTIVATED)

SCAVEN

GEEJECTORNOZZLE

FLAPPERVALVE

AIRBLEEDSOLENOID

(SHUTOFF)VALVE

ENGINECOMPRESSORBLEEDAIR

SCAVAIROUTLET

AFTFAIRING

ENGINEAIRINLET

SWIRLGUIDES

FILTERTUBE

(SEEDETAILVIEW)

SCAV

AIR

OFF

ATMOSPHERICAIR

FILTEREDA

IR

CONTAMINA

TEDAIR

ENGINECOMPRESSORBLEEDAIR

MECHANICA

LACTUATION

ELECTRICA

LACTUATION

EJECTORMANIFOLD

LOCATEDONBOTTOM

OFPARTICLESEPARATOR

(VIEWLOOKINGDOWN)

EJECTOR

MANIFOLD

G71-1000-2

Figure 2. Particle Separator Operating Principle Current Type (APM Unit)

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