Specifications

SECTION II
AIRPLANE AND SYSTEMS
MODEL 560
EJECTOR PUMPS
Four ejector pumps in each fuel cell utilize existing fuel pressure in conjunction with a venturi to
produce a high-volume flow. As high pressure fuel is forced through the ejector orifice, a low pressure area
is created at the pump inlet drawing in a comparatively large volume of fuel and pushing it out at low
pressure.
The primary ejector pump uses bypass fuel from the engine-driven pump as its motive flow source to
pick up fuel from the sump area and deliver it to the engine. Three transfer ejector pumps in each tank
operate similarly except that they use bypass fuel from the main supply line as a motive flow source. Their
function is to ensure a constant supply of fuel to the sump by scavenging from the lowest point in the cell.
CROSSFEED
Crossfeed is controlled by a selector on the left switch panel labeled L TANK, OFF, R TANK.
Crossfeed allows both engines to be supplied from one fuel cell.
Selecting either tank automatically turns on the electric boost pump in that cell, opens both crossfeed
valves and three seconds later closes the motive flow shutoff valve on the side not selected. Returning the
selector to OFF reverses the sequence. A green INTRANSIT light above the selector illuminates any time
the crossfeed valves are not fully closed or open, or do not coincide with switch position.
NOTE
When selecting crossfeed, it is important to allow sufficient time for the cycle of events
to be completed before returning the switch to OFF. Not allowing sufficient time can
interfere with the normal operation of the time delay relays resulting in loss of control
of the crossfeed system. If experienced, this condition can be corrected by placing
the battery switch in EMER and turning both generators off. After several seconds,
electrical power can be restored and crossfeed will function normally.
When crossfeed is selected, it is possible for a pressure spike to activate the fuel boost pump in the
tank opposite the one selected. If this occurs, both fuel boost pumps would be operating, causing equal
fuel pressures on both sides, preventing crossfeeding. When initiating system operation, monitor the FUEL
BOOST ON annunciator panel lights and if both illuminate, cycle the fuel boost switch for the nonselected
tank to OFF and back to NORM. This deactivates the boost pump in the tank not selected and allows
normal crossfeed.
Operationally, it is seldom necessary to balance the fuel load by crossfeeding unless single-engine
operations have been conducted or an uneven load was acquired during fueling. Maximum asymmetrical
fuel differential between fuel tanks for normal operations is 200 pounds. In an emergency, the maximum
asymmetrical fuel differential is 600 pounds.
Figure 2-9
EJECTOR PUMP
I 2-16 Configuration AA 56OMB-01