C2 CRH LFO Pages 2/9/01 12:55 PM Page 25
Fuel System
Fuel System
Citation; CI; CII; CII-627
J-BOX
IN TRANSIT
CROSSFEED
VALVE
LH RH TRANSFER
TANK OFF TANK EJECTOR PUMPS
1 LH RH 1
ENG ENG
CROSSFEED LINE
FUEL LOW
FUEL LOW FUEL FLTR LEVEL
LEVEL R FUEL
L FUEL BYPASS LEVEL LO
LEVEL LO LH RH
LH RH
FUEL FLTR
BYPASS
LH RH
MOTIVE FLOW
SHUT
LH ENGINE RH ENGINE
3000 O FIRE FIRE LH MAIN DC BUS RH MAIN DC BUS
F PUSH PUSH
2700 F
2400
F 2100
F LH RH
U
1800
U
L FUEL R FUEL BOOST BOOST
E E
L PRESS LO PRESS LO
L 1500 15 15
Q 1200 Q
T T FUEL LOW
900
Y Y PRESS
600
300 LH RH FUEL BOOST
L R
0 FUEL CANNISTER
LBS UNITS 550-SUB, SII LH ON RH
O
ENGINE-DRIVEN F
F
MOTIVE FLOW VALVE 2000 O
FUEL PUMP AND NORM NORM
F FUEL CONTROL UNIT
5,008 LBS TOTAL 1800 F
F
F
C0/C1 - 800 LBS MAX IMBALANCE FLOW TRANSMITTER U 1600 U
C2 - 600 LBS MAX IMBALANCE E E
1400
FUEL L L
OIL COOLER 1200
F F
PRIMARY EJECTOR OR L 1000 L L FUEL R FUEL
BOOST PUMP FLOW FLOW DIVIDER O
O 800 BOOST ON BOOST ON
W W
TRANSFER EJECTOR FLOW 600
AUTOMATIC SHUTOFF
400
L R FUEL
ENGINE-DRIVEN PUMP 200 BOOST ON
MOTIVE FLOW 1 WITH MOTIVE FLOW PRESSURE
SWITCH (THE MOTIVE FLOW LH ENGINE 0 RH ENGINE LH RH
PRESSURE SWITCH TERMINATES LBS/HR
ENGINE-DRIVEN PUMP
HIGH PRESS FLOW THE START SEQUENCE AT UNITS 550-SUB, SII
APPROXIMATELY 30 TO 40% N2 ON
EPA RETURN UNITS 002 TO 405 W/O SB550-28-1)
Citation I/II/SII For training only 4F-1
May 1998
C2 CRH LFO Pages 2/9/01 12:55 PM Page 26
4F-2 For training only Citation I/II/SII
July 1999
Fuel System
Fuel System
Citation SII
TRANSFER PUMPS PRIMARY
(EJECTOR) MANUAL
EJECTOR SHUTOFF
FUEL PUMP VALVE
(MAINTENANCE)
INTRANSIT
CROSSFEED
VALVE
LH RH
TANK OFF TANK
FUEL LEFT WING TANK RIGHT WING TANK
PROBES (6) 431 GALLONS 431 GALLONS
LH RH
BOOST ENG ENG BOOST
PUMP PUMP
FUEL
FUEL LOW FILTER
LEVEL TEMPERATURE FUEL LOW
185LBS COMPENSATOR FLOAT SWITCH (185 LBS)
LEVEL
LH RH FUEL FLTR
BYPASS LH RH 185LBS
FUEL TEMP COMPENSATOR
LH RH
MOTIVE FLOW
SHUTOFF VALVE CROSSFEED LINE
(NORMALLY OPEN) RH CROSSOVER BUS RH MAIN DC BUS
LH ENGINE RH ENGINE
FIRE FIRE
PUSH PUSH EPA RETURN FUEL BOOST
FIREWALL
3000 O
F
SHUTOFF LH ON RH
2700 F VALVE O
2400 F
F F F
2100 FUEL LOW
U U NORM NORM
E 1800 E PRESS FUEL CANISTER
L 1500 L
LH RH
Q 1200 Q
T T MOTIVE FLOW VALVE
Y 900
Y LOW PRESSURE SWITCH
600
300 FUEL
L R 2000 O BOOST ON
0 F FUEL
F 1800 F
F RETURN LINE
LBS LH RH
U 1600 U PRIMARY EJECTOR OR
FLOW TRANSMITTER E 1400
E BOOST PUMP FLOW
L L
5,816 LBS TOTAL 1200 ENGINE-DRIVEN
200 LBS MAX IMBALANCE OIL COOLER F F PUMP & FUEL TRANSFER EJECTOR FLOW
L 1000 L CONTROL UNIT
O 800 O ENGINE-DRIVEN PUMP
FLOW DIVIDER W
600
W MOTIVE FLOW
AUTOMATIC SHUTOFF L 400
R ENGINE-DRIVEN PUMP
200
HIGH PRESS FLOW
LH ENGINE 0 RH ENGINE
LBS/HR EPA RETURN
Citation I/II/SII For training only 4F-3
May 1998
4F-4 For training only Citation I/II/SII
June 1997
Fuel Storage
Each wing tank extends from the wing root to the wing tip. The
tanks include all internal wing area forward of the rear spar
except for the inboard leading edge and the area above the
wheel well. Gaps in the forward wing spar and ribs allow fuel to
flow inboard. One-way flapper valves restrict fuel flow to pre-
vent sudden weight and balance shifts during maneuvering. An
overwing filler cap near each wing tip allows gravity fueling of
the tanks. Total wing tank usable capacity varies with aircraft
model (see Table 4F-1).
Each tank’s venting system consists of an underwing air scoop,
float valve, check valves, and a vent line that extends from the
wing tip to the inboard tank area. During maneuvering the float
valve closes to prevent fuel loss and the check valves open to
vent the tank. Units 001 to 213 with SB 21-9, units 425 and
subsequent, Citation II, and Citation SII aircraft: each wing
tank has a vent surge tank that captures fuel vented during fuel
expansion. After the fuel tank level drops, fuel siphons from the
surge tank back into the wing tank.
Aircraft Usable U.S. Gallons Total
Each Tank Total Pounds1
Citation 001 to 040 w/o SB 21-9 268 536 3618
Citation 041 to 213 2/o SB 21-9 272 544 3672
Citation/Citation I 214 and sub. 282 564 3806
Citation II 371 742 5008
Citation SII 431 862 5818
1 6.75 lbs/gallon
Table 4F-1; Fuel Storage
Citation I/II/SII For training only 4F-5
June 1997
An internal sump area in each wing tank’s inboard section con-
tains an electric boost pump, primary ejector pump, and quick
drains used for water and sediment removal. The Citation and
Citation I have five drains; the Citation II units 2 to 59 and SII
have six drains, and the Citation II units 60 and subsequent
have four drains. Each wing tank also has two or three (SII)
transfer pumps that move fuel from the main tank area into the
sump area.
Fuel Indicating
Capacitance type fuel probes in the wing tanks drive the verti-
cal tape FUEL QTY indicator. The system operates on 28V from
the DC electrical system. The Citation and Citation I have four
fuel probes per wing; the Citation II has five probes per wing,
and the Citation SII has six probes per wing.
A float switch in each wing tank illuminates its respective FUEL
LEVEL LO or FUEL LOW LEVEL (SII) annunciator when 170
(Citation/Citation I), 169 (Citation II) or 185 (Citation SII) lbs
remain in the associated tank.
Fuel Distribution
During engine start after the start button is pressed, the electric
boost pump supplies positive fuel feed to the engine-driven
pump. Fuel flows from the sump area through a check valve,
manual shutoff valve, fuel filter, and firewall shutoff valve. If the
fuel filter begins clogging, a differential pressure switch closes
at 3.75 PSID to illuminate the FUEL FILT BYPASS annunciator.
At 4.75 PSID, the fuel filter bypass valve opens to route fuel
around the filter.
After the engine starts, the electric boost pump de-energizes;
the primary ejector pump supplies fuel from the sump area to
the engine-driven pump. With the engine-driven pump operat-
ing, the primary ejector pump receives motive flow fuel through
the motive flow valve and open motive flow shutoff valve.
4F-6 For training only Citation I/II/SII
June 1997
Fuel System
On Citation/Citation I units 001 to 660 without SB 28-7 and
Citation II units 2 to 405 without SB 28-1, a motive flow pres-
sure switch in the primary ejector pump supply line controls elec-
tric boost pump operation. On Citation/Citation I units 001 to
660 with SB 28-7, Citation I units 661 and subsequent,
Citation II units 2 to 405 with SB 28-1, Citation II units 406
and subsequent, and Citation SII aircraft, the generator con-
trol unit (GCU) controls electric boost pump operation during
engine start.
If fuel pressure in the supply line drops below approximately 5
PSI, a pressure switch illuminates the FUEL PRESS LO or LOW
FUEL PRESS annunciator. The electric boost pump then ener-
gizes to supply fuel from the sump area to the engine-driven fuel
pump. If the annunciator remains illuminated then the electric
boost pump is inoperative. Check that the fuel boost pump CB is
in and the fuel boost pump switch is on.
Placing the boost pump switch in ON, regardless of throttle lever
position and fuel pressure, supplies power to the electric boost
pump from the Left and Right Main DC buses. On the SII air-
craft, the Right Main DC bus is the only power source. During
boost pump operation, the respective FUEL BOOST ON annun-
ciator illuminates.
Placing the crossfeed switch in LH TANK or RH TANK cross
feeds fuel from one tank to both engines. The selected tank’s
electric boost pump operates, both crossfeed valves open, and
fuel flows to both engines from the selected tank. After three sec-
onds of operation, the opposite motive flow shutoff valve closes.
The green INTRANSIT light illuminates during crossfeed valve
operation and when the crossfeed valves position does not
agree with crossfeed switch position.
Citation I/II/SII For training only 4F-7
June 1997
Defueling
The fuel tanks can be defueled by suction, force-draining, or
transfer (crossfeed). The suction method draws fuel from the
tank through the overwing filler cap. Force-draining uses the
electric boost pump to draw fuel and pump it under pressure
through the disconnected fuel feed line at the engine’s fuel con-
trol unit. Finally, the transfer method uses the crossfeed valves
to drain fuel from one tank and move it to the opposite tank.
4F-8 For training only Citation I/II/SII
June 1997
Fuel System
Fuel System
Power Source Motive flow ejector pump
Motive flow fuel
Distribution Crossfeed manifold
Fuel transfer motive flow
Motive flow manifold
Wing tank to respective engine (L/R) via
engine manifold
Control ENGINE START (L/R) switches
ENG FIRE switchlights (L/R)
FUEL BOOST switches (L/R)
LH TANK/RH TANK crossfeed selector
STARTER DISENGAGE switches (L/R)
Throttles
Fuel control unit (fuel cutoff)
Monitor Annunciators
FIREWALL SHUTOFF (L/R)
FUEL BOOST ON (L/R)
FUEL FILTER BYPASS (L/R)
FUEL LOW LEVEL (L/R)
FUEL LOW PRESS (L/R)
Crossfeed INTRANSIT light
FUEL FLOW gage
FUEL QTY gage
Protection Circuit breakers
Prist
Fuel filters
Fuel firewall shutoff valves
Motive flow shutoff valve
.07 emergency cutoff
Citation I/II/SII For training only 4F-9
June 1997
4F-10 For training only Citation I/II/SII
June 1997
