18.104.22.168 Underwing single point pressure servicing nozzle. An underwing single point
pressure servicing nozzle conforming to the functional and performance requirements of
MIL-N-5877 (designated type D-l), or a commercial aviation refueling nozzle capable of
connection to the International Standard bayonet adapter, shall be furnished for the 2-inch
servicing hose. The underwing nozzle assembly shall permit interchange with the nozzles
specified in 22.214.171.124 and 126.96.36.199 by utilizing a dry break coupling as specified in 188.8.131.52.
3.8.3 Pump. A power takeoff driven, self-priming, centrifugal, aircraft fuel dispensing
type pump shall be provided. The pump internal components shall be of nonferrous materials.
The pump shall be capable of producing a vacuum of not less than 18 inches of mercury (Hg)
when loading the tank from an outside source. The pump shall be so constructed and positioned
that fuel will not enter into any gearbox or transmission. A drain plug or valve shall be provided
for completely draining the pump.
184.108.40.206 Power takeoff interlock. A brake interlock shall be provided to prevent truck
movement while the power takeoff is engaged. The interlock shall be air operated.
3.8.4 Pumping system operation. The pumping system shall provide the pressure control
and flow rates specified herein. For overwing (open port) refueling, the flow rate shall be
controllable between zero and 100 gpm by the trigger control of the 1.5 inch overwing nozzle.
For pressure (underwing and closed-circuit) refueling, the pumping system shall provide for any
servicing rate between zero and the required nominal flow capability for the specified hose and
nozzle (as indicated in 220.127.116.11 and 18.104.22.168) based on the aircraft demand. The pumping system
shall exhibit no instability in pressure or flow rate under any operating condition. The vacuum
of the pump suction at the maximum refueling rate shall be not more than 7 inches Hg as the
tank approaches empty.
22.214.171.124 Overwing (open port) fuel servicing operations. The pumping system shall
function as follows:
(a) Refuel from the tank through the filter/separator, the contamination monitor, the
meter, the 2-inch servicing hose, and the 1.5 inch overwing nozzle at flow rates from
zero to 100 gpm. The flow rate shall be regulated on demand by control of the
trigger of the 1.5 inch overwing nozzle;
(b) Defuel from the aircraft through the 1.5 inch overwing nozzle, the 2-inch hose, the
meter, the filter/separator, the contamination monitor, and into the tank at flow rates
of not less than 60 gpm. (See 126.96.36.199 for nozzle extension required for deep tanks);
(c) Defuel from the aircraft through the speed ends (see 188.8.131.52), the 2.5 inch suction,
hoses (see 3.5.23), the suction stub (see 3.5.21), the filter/separator, the
contamination monitor and into the tank at flow rates up to 100 gpm.