SINGLE-POINT PRESSURE
REFUELING SYSTEM (SPPR)
General
The single-point pressure refueling system
enables wing and fuselage tanks to be filled
simultaneously through a single-point pressure
refueling adapter. A refueling truck or hydrant,
capable of delivering between 20 psi and 40
psi is required. On aircraft 45-157 and sub-
sequent and prior aircraft modified by SB 45-
28-2, pressure is limited to between 20 psi
and 55 psi.
SPPR Components
• SPPR Adapter Panel
The single-point pressure refueling adapter
panel (Figure 5-14), is located below the right
engine pylon. The panel contains the refuel-
ing adapter and a lever to open/close the
precheck valve.
• Refuel/Defuel Panel
The refuel/defuel panel is located just aft of
the adapter panel and contains a FUEL SYS,
PWR ON-OFF switch, a digital TOTAL FUEL
Q T Y i n d i c a t o r a D E F U E L , R E A DY- O F F
switch, and a defuel OFF and ready indicator
light (Figure 5-15). The READY position of
the defuel switch has an amber annunciator as-
sociated with it and the OFF position has a
green annunciator associated with it.
Although SPPR does not require electrical
power for operation, if it is desired to use the
TOTAL FUEL QTY indicator during refuel-
ing, the FUEL SYS switch must be placed to
the PWR ON position. Turning this switch on
also turns on the pylon light, if installed. Insure
that the DEFUEL switch is in the OFF posi-
tion before turning the FUEL SYS switch to
the PWR ON position. The refuel/defuel power
on/off switch is powered through the aircraft’s
rear hot bus.
• Refueling Shutoff Valve and Pilot
Valve
The refueling shutoff valve is a poppet-type
valve that is spring-loaded closed (Figure 5-
15). Fuel pressure fed through the refueling
adapter forces the shutoff valve open when re-
fueling is initiated. Fuel flows to the wing
tanks through the two transfer lines and also
into the fuselage tank. As the wings become
full, the back-pressure causes all of the re-
maining fuel to flow into the fuselage tank
until the tank becomes full or until the refuel-
ing is terminated at the desired amount of fuel.
Normally, the wing tanks will fill faster than
the fuselage tank and will overflow into the
fuselage tank, through the vent/expansion lines.
During refueling a small, controlled, amount
of fuel flows into a chamber on the down-
stream side of the shutoff valve. The fuel pres-
sure in this chamber must be continually
vented out through the pilot line and pilot
valve to keep the shutoff valve open. The pilot
valve has a float in it which causes the pilot
valve to close when the fuselage tank becomes
full. When the pilot valve closes, the fuel pres-
sure will backup in the pilot line and cause the
pressure to rise in the chamber on the back side
of the shutoff valve. When the pressure in the
chamber equals the pressure on the inlet side
of the shutoff valve, the spring in the shutoff
valve will cause the valve to close; thus, ter-
minating refueling.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
5-20
FOR TRAINING PURPOSES ONLY
FlightSafety
international
PRECHECK
VALVE
Figure 5-14. SPPR Adapter Panel
