Hartzell HC-E3YR-7 Owner's Manual page 63

(7) The function of the Pressure Control Unit is to reduce
the governor supplied oil pressure of 270 to 300 PSI to
a lower oil pressure. Refer to Figure 2-2. One mode of
reduction is fixed and the second is variable. The two
modes of reduction are discussed in paragraphs
1.D.(7)(a) and 1.D.(7)(b).
(a) This adjustment supports governor control constant
DESCRIPTION AND OPERATION
Propeller Owner's Manual
speed operation. Initial adjustment of the Pressure
Control Unit requires that the plunger position
(length of extension from the pressure control unit
body) is limited by a restraining bolt or screw. This
is to limit the minimum (lower) oil pressure that
the Pressure Control Unit will reduce the governor
supplied oil pressure of 270 to 300 PSI. This
pressure must be high enough to make sure that
the governor will be able to supply enough oil
pressure to the propeller to reach low pitch during
normal constant speed operation (governed control).
Refer to Figure 2-3.
1 The minimum pressure adjustment is the lowest
pressure that the pressure control unit will
attenuate the governor supplied oil pressure
of 270 to 300 PSI. This lowest pressure for the
pressure control unit is conversely the maximum
pressure permitted by the pressure control unit
to reach the propeller during constant speed
operation between low pitch and high pitch.
Refer to Figure 2-3.
136
61-00-36
Page 2-15
Rev. 2 Feb/17