Citation Mustang Fuel

GENERALThe Citation Mustang fuel system includes twointegral wing fuel tanks, an automatic fuel dis-tribution system, and manual fuel transfer ca-pability (Figure 5-1). Each wing tank includesan integral engine feed bay. A primary ejector

pump and an electrically powered boost pumpprovide fuel to the respective engine. Switcheson the lower pilot tilt panel and CAS messageson the multifunction display (MFD) control andindicate fuel operation and transfer.

0

2

4 6

8

10

MAINFUEL

LBS X 100

CITATION MUSTANG OPERATING MANUAL

CHAPTER 5FUEL SYSTEM

510OM-00 5-1

INTRODUCTIONThis chapter presents information on the fuel system of the Citation Mustang. Integralfuel tanks in the left and right wings provide fuel storage. The fuel distribution systemprovides fuel to each engine from the corresponding wing tank. The fuel transfer sys-tem allows fuel to be transferred from one tank to the other. Crew alerting system (CAS)messages alert the pilot to fuel system emergency and abnormal situations.

Information in this chapter is provided for the airframe fuel system upstream of the high-pressure engine-driven fuel pump. For description and operation of the engine fuel sys-tem, refer to Chapter 7—“Powerplant.”


510OM-005-2

FUE

L

LBS

PP

H °C

1500

1000

500

CA

S

OIL

PR

ES

S L

O L

CA

BIN

ALT

T2 H

TR F

AIL

RW

/S O

’HE

AT

LW

/S A

/I FA

IL L

FUE

L P

RE

S L

O R

EN

G A

/I C

OLD

LC

AB

IN D

OO

RA

FT D

OO

RP

/S H

TR L

F/W

SH

UTO

FF R

FDR

FA

ILS

UR

FAC

E D

E-IC

ES

PD

BR

K E

XTE

ND

300

700

1040

950

13

400

F/W

SH

UTO

FF L

-RFU

EL

FLTR

BP

L-R

FUE

L LV

L LO

L-R

FUE

L P

RE

S L

O L

-RFU

EL

BO

OS

T L-

RFU

EL

BO

OS

T L-

RFU

EL

LO IN

OP

FUE

L TR

AN

SFE

R

MA

IN S

PA

R

MA

IN S

PA

R

FO

RW

AR

D S

PA

R

FO

RW

AR

D S

PA

R

RE

AR

SP

AR

RE

AR

SP

AR

LPLP

TS

VE

NT

SC

OO

P

OV

ER

BO

AR

DV

EN

T L

INE

VE

NT

VA

LVE

SU

RG

EV

EN

T L

INE

FU

EL

PR

OB

E

FU

EL

DR

AIN

FU

EL

FIL

LER

CA

P

ELE

CT

RIC

BO

OS

TP

UM

P

LEF

TS

UR

GE

TAN

K

LEF

T M

AIN

FU

EL

TAN

K

SC

AV

EN

GE

EJE

CT

OR

PU

MP

S

TE

MP

ER

AT

UR

ES

EN

SO

R

FLA

PP

ER

VA

LVE

PR

IMA

RY

EJE

CT

OR

PU

MP

FLO

W-R

ES

TR

ICT

OR

OR

IFIC

E

(TO

)(T

O)

(FR

OM

)(F

RO

M)

L E

NG

INE

FU

EL

SY

ST

EM

R E

NG

INE

FU

EL

SY

ST

EM

TR

AN

SF

ER

SH

UT

OF

FV

ALV

E

FIR

EW

ALL

SH

UT

OF

FV

ALV

E

FIR

EW

ALL

SH

UT

OF

FV

ALV

E

LOW

-P

RE

SS

UR

ES

WIT

CH

SU

RG

EV

EN

T L

INE

LE

GE

ND

FU

EL

INS

IDE

TA

NK

FR

OM

EN

GIN

E F

UE

LS

YS

TE

M

TO

EN

GIN

E F

UE

LS

YS

TE

M

LOW

-PR

ES

SU

RE

,H

IGH

-VO

LUM

E F

LOW

TR

AN

SF

ER

PR

ES

SU

RE

VE

NT

LIN

ES

GR

AV

ITY

SU

CT

ION

Fig

ure

5-1

. F

uel

Tan

k S

yste

m


510OM-00 5-3

FUEL STORAGEDESCRIPTIONThe left and right tanks each have a fuel capacityof 192.5 gallons (728.7 liters) for a total com-bined fuel capacity per aircraft of 385 gallons(1,457 liters). Refer to Table 5-1 for approxi-mate volumes and weights, or refer to theAirplane Flight Manual (AFM) for current data.The Citation Mustang fuel system does not re-quire the use of anti-icing additives.

Each wing tank system (left wing and rightwing) includes:

• Main tank cavity

• Engine feed bay

• Venting system

• Tank filler

• Sump drain valves

• Scavenge pumps

• Fuel probes

• Flapper valves

COMPONENTS

Main Tank CavityEach main tank cavity (one in each wing, be-tween the forward and rear wing spars) is in-tegral to the wing. Holes in the main spar andribs allow fuel flow through the wing (Figure5-1). Flapper valves, attached to spar and ribholes, allow fuel flow inboard while inhibit-ing flow outboard.

Engine Feed BayAn engine feed bay is an integral part of eachwing tank. It is the lowest point in the fuel sys-tem, which is the location for fuel pickup (in-take) for the fuel distribution system. Eachfeed bay holds approximately 8 gallons and hasfour vent openings (ensures the bay maintainsfull capacity under all flight conditions).

Venting SystemThe venting system consists of a tank, ventlines, flapper, and float-controlled vent valve.A vent surge tank at the most outboard bay ofthe wing fuel tank collects fuel surges from themain tank and also provides a portion of therequired expansion space. The fuel travelsoutboard from the main tank through the surgevent line.

During climbs and maneuvers, air trapped inthe forward inboard area of the main tank es-capes through the climb vent line to vent intothe surge tank; this allows the main tank areato fill with fuel.

A float-controlled vent valve is connected tothe vent surge tank. When the fuel level is fullenough to raise the float, the valve closes,preventing fuel from overflowing into thesurge tank. When the fuel level is low, thevalve opens to provide venting. A flappervalve permits fuel to drain from the surge tankback into the main tank. If the vent surge tankfills, another vent line allows spillage over-board through the NACA scoop (Figure 5-2)under the wing. The vent lines normally allowair to enter or exit through the NACA scoop.The scoop does not require anti-icing.

Figure 5-2. NACA Scoop Fuel Vent

Table 5-1. FUEL SYSTEM CAPACITY

STANDARD (U.S.) METRIC

TotalCapacity Weight Volume Weight Volume Each 1,290 192.5 585 728.7 Tank pounds gallons kg liters

Both 2,580 385 1,170 1,457 Tanks pounds gallons kg liters


510OM-005-4

Tank FillerThe aircraft has one fuel tank filler assemblyon the upper surface of each wing, between themain spar and the aileron (Figure 5-3). Thefiller assembly consists of a flush-type capand a standpipe.

Sump Drain ValvesSump drain valves (Figure 5-4) are at the lowpoints in each wing where water can collect.In each wing, there is a sump drain in each ofthe following locations:

• Outboard and inboard of the landinggear (behind the main spar)

• In the engine feed bay

• Between the feed bay and the main spar

• Between the forward and main spars(forward of the feed bay)

When draining sumps, do not turn any tool inthe drain. The drain may lock open, resultingin fuel loss.

CONTROLS AND INDICATIONS

Fuel Quantity Gauging System The fuel quantity gauging system includes asignal conditioner and five fuel quantity probesin each wing. The left and right fuel quantitysignal conditioners gather data from their re-spective sides and convert the data into the ap-propr ia te s igna l s fo r the G1000 engineindicating crew alerting system (EICAS).

The EICAS uses the data for the FUEL quan-tity display, and for CAS messages to alert thepilot of a low fuel quantity level (in eitherwing) or a failure of the gauging system.

OPERATION

Fuel ServicingFuel servicing includes procedures necessary forfueling, and procedures used to check the fuelfor contamination or condensation. The fuel isserviced through the flush-type cap on the out-board section of either wing (Figure 5-5).

RefuelingRefuel in areas that permit the free move-ment of fire equipment. Follow approvedgrounding procedures for the airplane and

Figure 5-4. Sump Drain Valves

Figure 5-3. Fuel Tank Filler

Figure 5-5. Fuel Tank Servicing


510OM-00 5-5

the fueling equipment. There is one approvedgrounding point under the outboard end ofeach wing (Figure 5-6).

Refuel to the bottom of the standpipe to achievemaximum usable fuel for flight planning. If thefuel tank is filled above the bottom of thestandpipe, there may not be room for expan-sion, which can result in fuel spillage throughthe fuel vents.

Approved fuels and additives for operation ofthe aircraft are listed in the “Limitations” sec-tion of the AFM. Use of avgas is not approved.

DefuelingDefueling must be performed as a mainte-nance function.

FUEL DISTRIBUTION

DESCRIPTIONThe right side of the wing fuel system is iden-tical to the left side, except for a fuel transfervalve in the right tank and a fuel temperatureprobe in the left tank.

COMPONENTS

Electric Boost PumpsElectric boost pumps are used for:

• Engine starting

• Low fuel supply pressure

• Fuel transfer

A 28-VDC boost pump is in each engine feedbay. Either boost pump can be controlled au-tomatically or manually. Circuit protectionfor the boost pumps is in the aft J-box.

Primary Ejector Pumps The primary ejector pump is submerged infuel in each engine feed bay (Figure 5-7). Thepump utilizes a small jet of high-pressure“motive flow” fuel (from the respective enginefuel pumps). The fuel passes through a ven-turi, pulls a larger low-pressure flow of fuelfrom the feed bay, and pumps it back to the en-gine. Some of the resulting flow also providesmotive flow to the scavenge ejector pumps. Theprimary ejector pump has no moving parts. Itoperates whenever motive flow is available.

Scavenge Ejector PumpsA scavenge ejector pump constantly trans-fers fuel from the forward and outboard areasof each tank to its engine feed bay. This en-sures the engine feed bay is full and the pri-mary ejector and electric boost pump aresubmerged in fuel until the wing tank is nearlyempty and the fuel level is drained in the feedbay. Each scavenge ejector pump receiveslow-pressure motive flow from the same side

Figure 5-6. Grounding Point

INLET

OUTPUT

SUCTION

EJECTOR PUMPMOTIVE FLOW

Figure 5-7. Primary Ejector Pump


510OM-005-6

primary ejector pump or (when operating)the same side electric boost pump.

Fuel Transfer ValveThere is a fuel transfer valve in the right en-gine feed bay. It opens or closes to allow flowbetween left and right wing tanks. It is normallyclosed. The valve is a direct-acting solenoidvalve, controlled by the FUEL TRANSFERselector on the lower instrument tilt panel(Figure 5-8). The valve works with the boostpump on the side from which fuel is beingtransferred. When fuel transfer is commandedby the pilot, the valve opens and the boostpump is energized. Fuel is pumped from the en-gine feed bay into the opposite engine feedbay through a small opening that limits thetransfer flow. Circuit protection for the trans-fer valve is provided by the L and R FUELCONTROL circuit breakers in the aft J-box.The fuel transfer valve is not powered when thebattery switch is in the EMER position.

Firewall Shutoff ValvesFirewall shutoff valves for each engine are inthe respective aft wing fairing (between thewing and fuselage). In the event of a fire, thevalves shut off fuel flow to the respective en-gine on pilot command. The valves can be

commanded closed by the FADEC in the eventthe normal shutdown valve fails. Circuit pro-tection for the shutoff valves are provided bythe L FEED BUS #2 and R FEED BUS #2,through the respective L and R FIREWALLCUTOFF circuit breakers on the aft J-box.

Refer to Chapter 8—“Fire Protection” formore information on the firewall shutoff valvesand their operation.

Fuel Pressure SwitchesPressure switches are in the engine fuel sup-ply lines adjacent to each engine. The switchesdeactivate at 6.4 psig (maximum) and reacti-vate when the engine fuel supply pressuredrops below 4.65 psig. When fuel pressuredrops below this limit, the amber FUEL PRESLO L-R message appears.

Fuel Flow TransmitterA fuel flow transmitter is on each engine fuelsupply line. The transmitter sends a 0-5 volt ana-log signal to the G1000 system, which trans-lates the signal to pounds/kilograms per hour.

CONTROLS AND INDICATIONSThe pilot controls the fuel system with the Land R FUEL BOOST switches and the FUELTRANSFER selector. Fuel indications are dis-played on the MFD in the EICAS window,which is displayed in two columns on the leftside. In the event of MFD failure or revision,the EICAS section is shown in a single-columnformat on whichever displays are in rever-sionary mode.

FUEL BOOST SwitchesThe FUEL BOOST switches are on the lowerinstrument tilt panel (Figure 5-8). Each switch(L and R) has three positions: ON, OFF, andNORM.

The switches manually control the respectiveboost pumps in the ON and OFF positions. Inthe NORM position, boost pump operation isautomatically controlled.

Figure 5-8. Fuel Controls

FUEL TRANSFER SelectorA FUEL TRANSFER selector (Figure 5-8) onthe lower left instrument tilt panel controls the(normally closed) fuel transfer valve.

The selector has three positions: L TANK,OFF, and R TANK.

The selector opens the fuel transfer valve andenergizes the supply side fuel boost pump,which allows fuel to be pumped to the se-lected engine feed bay from the opposite en-gine feed bay.

Fuel is transferred at approximately 10 ppm(4.5 kg per minute). Rate varies with engine(s)fuel flow.

Fuel Quantity IndicationThe aircraft has a passive capacitance-typefuel quantity system. The system consists of:

• Independent dual-channel digital signalconditioner (in the left aft wing fairing)

• Five fuel probes in each wing tank

• EICAS displays

Fuel quantity is displayed on the G1000 GDU1500 MFD “AUX” page and in the left EICAScolumn of the MFD (Figure 5-9). Quantitycan be displayed in either pounds or kilo-

grams. Fuel tank levels are displayed with awhite pointer on a white scale on the fuel dis-play and by green digits just below the scale.In reversionary mode, only the digits are dis-played (Figure 5-10).

Total aircraft fuel is the sum of the fuel quan-tities displayed for each tank. This value is dis-played below the individual tank quantities ingreen digits. Total fuel quantity is displayedin the same units as the fuel tank levels. Invaliddata is displayed by a red X or white dashes.

Fuel Temperature IndicationThe fuel temperature probe is inside the leftside engine feed bay. The probe temperatureappears in the fuel display. Fuel tank temper-ature is displayed as green digits (in °C) belowthe fuel flow (see Figure 5-9). If invalid datais received, a red X is displayed. The temper-ature displayed is invalid if below –70°C(–94°F) or above 99°C (210°F).

Fuel Flow IndicationFuel flow is displayed digitally below thetotal fuel display. The digits are green and aredisplayed in pounds per hour (PPH) or kilo-grams per hour (KGH). Invalid data displaysas a red X.


510OM-00 5-7

Figure 5-9. Fuel Display in MFD (EICAS Normal Mode)

Figure 5-10. Alternate Fuel Display(EICAS Reversionary Mode)

CAS MessagesF/W SHUTOFF L-RThe engine fire-warning and fire-extinguishingsystems allow the crew to detect and suppressfires in the aircraft engine compartments. Whenthe red L–R ENGINE FIRE lights are pressed,the appropriate fuel shutoff valve closes and theamber F/W SHUTOFF L or R message appearson the EICAS (Figure 5-11). This message mayalso appear after engine shutdown if the nor-mal engine shutdown valve fails.

FUEL FLTR BP L-R If the fuel filter becomes clogged, the bypassvalve allows unfiltered fuel to enter the en-gines. Before the bypass valve is opened, a sig-nal is sent to the EICAS system to indicate animpending bypass, which displays the amberFUEL FLTR BP L-R message (Figure 5-11).Refer to the Chapter 7—“Powerplant” formore information.

FUEL LVL LO L-R The amber FUEL LVL LO L-R message indi-cates that fuel level is low in the indicated wingtank. Each signal conditioner channel sendsan ARINC discrete signal (low fuel level warn-ing) to the EICAS system when the respectivewing usable fuel quantity is less than approx-imately 170 pounds (25 gallons) (Figure 5-11).

FUEL LO INOP L-R The white FUEL LO INOP L-R message in-dicates the amber FUEL LVL LO L-R messageis not operational and cannot provide reliableindication of low fuel level.

In some situations, if the fuel quantity gaug-ing system fails (indicated by a red X on ei-ther fuel quantity EICAS display), there maystill be sufficient reliable data for the systemto determine whether or not fuel level isbelow 170 pounds (25 gallons). In this situ-ation, the FUEL LVL LO L-R message isstill useable as a minimum indication of fuellevel (appearing only when fuel level is below170 pounds in either tank). However, if thereis not sufficient reliable data to determine thatfuel level is above or below 170 pounds, theFUEL LO INOP L-R message appears, indi-cating which tank cannot supply valid data tocontrol the FUEL LVL LO L-R message.

FUEL PRES LO L-R When the fuel-supply pressure to an enginedrops below the activation point, its pressureswitch closes. The fuel pressure switch com-pletes an electrical circuit, which displays therespective amber FUEL PRES LO L-R message.If the boost switch(es) is in the NORM position,the boost pump(s) automatically energizes.

FUEL TRANSFER The FUEL TRANSFER selector, when in theL TANK or R TANK position, completes anelectrical circuit that automatically energizesthe electric fuel boost pump in the oppositetank and opens the fuel transfer valve. This ac-tivates the white FUEL TRANSFER messageand either the L or R FUEL BOOST whiteCAS message, assuming the boost switches arein the NORM position.

FUEL BOOST L-R The FUEL BOOST L-R message is presentanytime the boost pumps are on. The messageis usually white.


510OM-005-8

CAS

F/W SHUTOFF L-RFUEL FLTR BP L-RFUEL LVL LO L-RFUEL PRES LO L-RFUEL BOOST LFUEL BOOST RFUEL LO INOPFUEL TRANSFER

Figure 5-11. CAS Messages

The white FUEL BOOST L-R message ap-pears when the pilot commands the fuel boostpump on (by selecting the FUEL TRANSFERselector to L TANK or R TANK, by selectingeither FUEL BOOST switch to ON, or bypressing a start button).

The amber FUEL BOOST L-R message ap-pears when the corresponding fuel boost pumpis energized automatically in response to lowfuel pressure. This is only possible when ei-ther FUEL BOOST switch is selected toNORM.

ENGINE FIRE LightIn the event of an engine fire, the fire detec-tor in the engine compartment illuminates thered L or R ENGINE FIRE light (Figure 5-12).Pushing the light (which has an integral push-button switch) closes the corresponding fire-wall shutoff valve, which shuts off the fuel flowto the engine and illuminates the amber F/WSHUTOFF L-R message. For details, refer toChapter 8—“Fire Protection.”

OPERATION

Normal OperationDuring normal operation of the fuel system,the L and R FUEL BOOST pump switches arein the NORM position. In this position, eachboost pump operates automatically:

• During engine s tart—White FUELBOOST L-R message appears.

• During fuel transfer operation—WhiteFUEL TRANSFER and white FUELBOOST L-R messages appear.

• When low fuel pressure is sensed in theengine fuel supply l ine—An amberFUEL PRES LO L-R message appearsfor a moment, followed quickly by anamber FUEL BOOST L-R message. Asthe boost pump quickly increases thefuel pressure, the amber FUEL PRESLO L-R message extinguishes quickly;it may not even be seen by the pilot.

If the throttle is OFF, the boost pumps do notenergize automatically in a low fuel pressurecondition, even though the boost pump switchis in the NORM position. When the switch isOFF, the boost pump does not operate. In theON position, the pump operates continuously.

Wi th t he L and R FUEL BOOST pumpswitches in the NORM position, pressing anENGINE START button energizes the corre-sponding fuel boost pump. This moves fuelfrom the wing tank engine feed bay on that sidethrough the firewall shutoff valve to the engine-driven fuel pump on the respective engine.

When the engine start terminates, the boostpump is deenergized and the white FUELBOOST L-R message disappears from theCAS window.

During normal operation, each engine is sup-plied with fuel from the primary ejector pumpin the engine feed bay of each tank. The elec-tric boost pump (when energized automati-cally or by pilot command) may augment theoperation of the ejector pump.


510OM-00 5-9

Figure 5-12. ENGINE FIRE and BOTTLEARMED Lights

Fuel Transfer System OperationUsing the fuel transfer system, fuel is trans-ferred from the wing tank engine feed bay tothe opposite wing tank engine feed bay. Thearrow on the FUEL TRANSFER selectorpoints to the wing tank where transfer fuel isdirected.

Rotating the FUEL TRANSFER selector knobfrom the OFF position to the R TANK position:

1. Energizes the left tank electric boostpump. This displays the white FUELBOOST L message if the boost pumpswitch is in the ON or NORM position. (Ifthe boost pump is set to OFF, there is noflow and no FUEL BOOST L message.)

2. Energizes the fuel transfer valve open.The white FUEL TRANSFER messageis displayed. The left tank boost pumppressure supplies fuel from the left wingtank engine feed bay through the opentransfer valve and into the right wing tankengine feed bay.

Check that the FUEL BOOST L-R message in-dicates only the correct boost pump is ener-gized. If both boost pumps are energized, fueltransfer does not occur. To deenergize thepump in the nonselected tank, cycle its L orR FUEL BOOST switch to OFF, then ON,then NORM, and leave in NORM position.

To verify fuel transfer, monitor the fuel quan-tity white tape pointers or the digital indica-tors (see Figure 5-9). Fuel normally transfersto the selected tank at approximately 10 ppm(600 pph). Maximum normal fuel imbalanceis 200 pounds. Maximum emergency fuel im-balance is 600 pounds.

To terminate fuel transfer and return the sys-tem to normal operation, rotate the fuel trans-fer selector to OFF. The electric boost pumpdeenergizes (if the FUEL BOOST switch is inthe NORM position), the white FUEL TRANS-FER message disappears, and the fuel trans-fer valve spring-loads closed.

If electrical power fails during fuel transfer op-eration, the fuel transfer solenoid valve returnsto the closed position, preventing fuel transfer.

EMERGENCY/ABNORMALFor specific information on emergency/abnor-mal procedures, refer to the appropriate ab-breviated checklists or the FAA-approved AFM.


510OM-005-10

Documents

Citation Mustang Fuel