Pratt & Whitney Rzeszów S.A.
MAINTENANCE MANUAL
PZL-10W ENGINE
73-22-01
1992.08.28
Page 10
Export Control Classification: PL/UE 9E999
The bypass
jet
cooperates with It.
The fuel pressures are delivered to the diaphragm chambers: to the lower - from behind the bypass jet, to the
upper - from behind the metering needle. Therefore the equal pressure drops on the bypass jet and the
metering needle are maintained (counting the spring force). It makes possible to control the metered fuel
capacity in accordance to the expression:
Q
f
= C * Q
b
( 1 0 ) Starting and acceleration corrector.
The starting and acceleration corrector consists of the assemblies as follows:
slide pair;
diaphragm assembly;
adjusting assembly.
The fuel pressure proportional to the observed rotational speed of the compressor turbine is delivered to the
spring chamber above the diaphragm. When the force resulting from acting of the fuel on the diaphragm will
exceed the value created by the spring tension, then the controlling slide i motion of the slide pair occurs. The
flow orifice of the valve changes in accordance to the slide window shape. The bypass fuel capacity and
consequently the pressure drop on the metering needle changes. The fuel capacity in the metered fuel main
will be controlled according to the assumed characteristic:
Q
f
= C * Q
b
p
3
The R4 screw adjustment causes the spring tension change.
( 1 1 )
Emergency rotational speed limiter of the compressor turbine.
The emergency rotational speed limiter of the compressor turbine consists of the slide, piston assembly and
adjusting screw. The mutual position of the piston and adjusting screw is fixed by the spring situated between
them. The slide of the emergency limiter of the compressor turbine rotational speed cooperates with the
controlling slide of the starting and acceleration corrector creating together with it the second slide pair
controlling the bypass fuel capacity. The controlling slide edge begins to close the shaped hollow in the
controlling slide of the starting and acceleration corrector at the rotational speed increase of the compressor
turbine (and full opened flow hollow of the starting and acceleration corrector). The fuel flow in the bypass line
decreases, limiting the fuel capacity in the metered fuel main. The limitation of the rotational speed of the
compressor turbine occurs.
