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From: (Nick Lappos)
Subject: Re: Particle Separator
Date: 29 Nov 1999
Newsgroups: rec.aviation.rotorcraft

In article <>, (RonPilotPI) wrote:
>>What is a particle separator?
>Sikorsky Aircraft used to refer to them at "EAPS" or Engine Air Particle
>Separator when they were first installed on several older Sikorsky ships such
>as the S-61, S-64, and H-53 series aircraft.
>Ron (Sikorsky fan)

In addition to the add-on type of separator described in the above posts, the
latest class of military engines, such as the T-700 and the T-800, have Inlet
Particle Separators (IPS for the acrynomically empowered) that have a swirl
effect on the inlet air to cause the same centrifugal separation described by
Helimech and Phil Slattery in other posts on this string.  These IPS are
light, and are quite effective without the drag and maintenance of the add-on
tube design, although the tubes are somewhat more effective (in terms of the
total percent and fineness of the particles separated).  The tube systems are
pretty poor in icing conditions, but then again, so am I.

The big issue with any filter is the power loss due to the drag on the inlet
air, which causes a suction at the inlet, and is felt by the engine as though
the aircraft is at a higher altitude.  This power loss is the real penalty for
a separator, since most helicopters use as much as 6 pounds of lift for each
horsepower installed.  If a separator uses 3% of the total engine power, and
there are 1000 horsepower being used, the net loss in lift and payload is 180
pounds, or 1 passenger.

Filters are sometimes used but the elements clog, and cause power loss, where
EAPS or IPS are self cleaning, and mostly maintenance free.

The power loss of not using some separator or filter is enormous, with as
little as 15 minutes hovering in sand capable of costing a permanent 5% loss
in power, due to eroding the compressor blades to new and interesting shapes.


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