Pratt & Whitney Rzeszów S.A.
MAINTENANCE MANUAL
PZL-10W ENGINE
73-22-01
1992.08.28
Page 6
Export Control Classification: PL/UE 9E999
The 2.5 min. OEI rating is engaged by the pilot in the cockpit The signal of the OEI rating engaging
is supplied to the electromagnet of the OEI parameter valve of the fuel metering pump. The
electromagnet engaging causes an opening of the additional metered fuel main in the fuel metering
pump. The total fuel capacity delivered to the combustion chamber increases. Simultaneously the
emergency limiter of the compressor turbine rotational speed shifts
to the higher limitation
parameters.
NOTE:
1.
The engaging
of
the 30 min, and 2.5 min. OEI rating is possible only in the case
when one from the pair of cooperating
engines
would be shutdown.
2.
In the case of one of two engines failure, the 30 min. OEI rating is automatically
engaged, and the parameters of the operating engine result from the actual power
demand by the helicopter main and tail rotors.
The separate function of the fuel metering pump is to deliver the starting fuel to the starting injectors
during the engine starting.
The fuel to the starting injectors is delivered from the starting fuel main. It begins behind the
metering needle. The starting fuel valve is a starting fuel metering assy.
The delivery control of the starting fuel is automatic - it is performed by the electric signal delivered
to the starting fuel electromagnet by a relay box and electronic limiter unit in the helicopter system.
C.
Description and operation of the assemblies of the fuel metering pump (Dwg 1).
(1)
Pressure assembly.
(a)
Coarse fuel filter.
It is situated in the inlet of the fuel metering pump. It is the grid filter designed
to separate random particles from the fuel.
(b)
Centrifugal pump.
It is driven by two gears. The driving gear is mounted on the splines of the
driven gear of the gear pump.
(c)
Gear pump.
It consists of two gears with the equal teeth number, installed in the pump case. It is
driven by the torque shaft from the engine accessory drive box. The pump drive is
sealed by a graphite seal and rubber sealing ring. The space between these seals is
connected to the drainage.