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Citation II Fuel System

Citation II Fuel System. Dr. Barnhart. Intro/General- Airframe (to eng. Boost pump) Fuel System Info. Fuel system- divided into 2 identical halves normally supplying the respective engine but with x-feed capability. Fuel flow to engines done by elec. Boost pumps and an ejector pump.

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Citation II Fuel System

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  1. Citation IIFuel System Dr. Barnhart

  2. Intro/General- Airframe (to eng. Boost pump) Fuel System Info. • Fuel system- divided into 2 identical halves normally supplying the respective engine but with x-feed capability. • Fuel flow to engines done by elec. Boost pumps and an ejector pump. • Controlled by switches and a selector on the pilot’s IP.- monitored by colored annunciator lights and gauges

  3. Tanks • Wet wing- each tank is an integral part of the wing structure- all of the internal wing area fwd. of the rear spar except main gear well. • Holes in spars and ribs permit free fuel flow- baffles inoutboard ribs help prevent unporting. • Each tank- vent system, qty. probes, filler cap, sump drains, ejector pumps, and an elec. Boost pump- combined usable fuel qty. 5,008 lbs.

  4. Tank vents • Vent system- bottom of ea. Wing- maintains positive internal tank pressures & permits fuel overflow due to thermal expansion. • Filler assembly- tank adapter, standpipe, cap & chain to attach cap to adapter. • 6 quick drains per side & 1 filter drain (see fig. 5-2)

  5. Boost pumps • DC powered in each tank; supplies fuel to eng. Fuel pump & crossfeed fuel to opp. Engine. Can also feed both engines • Controlled by switches on pilot’s IP

  6. Ejector Pumps • 3 per wing- each powered by motive flow (venturi principle)- feeds eng. Driven pump • Receives motive fuel from eng. Fuel pump • 2 transfer ejectors operate on motive flow from primary ejector or boost pump and transfer fuel from lowest point in tank to sump

  7. Crossfeed Valve • 2 motor driven crossfeed valves- Normally Closed (NC) to isolate rt. And left sides of fuel sys. Why 2? Nobody knows. • Electrically operated by selector on pilot’s IP. Valve movement indicated by green INTRANSIT light near selector • When open, fuel can flow freely from one side to another.

  8. Filter • 1 each in fuel supply line of ea. Wing fuel sys. • Incorporates a diff. press. Sw.- illuminates FUEL FILT BYPASS annunciator to warn of impending bypass. If illuminates, check cause upon lndg.

  9. Firewall shutoff valves • Electrically operated motor driven shutoff valve- 1 in each fuel supply line • Controlled by ENG FIRE sw. on glareshield- normally closed only in event of eng. Fire. • When both fuel and hyd. Firewall valves closed- respective F/W SHUTOFF annunciator illuminates

  10. Firewall shutoff valves ctn. • *If an eng. Is shut down in flight for other than fire- valve must be left open and fuel boost operated to prevent damage to eng. Driven fuel pump.

  11. Motive Flow Shutoff Valve • One solenoid-operated motive flow shutoff valve in ea. Wing fuel sys.- controls motive flow from eng. Pump to ejector pump. • Valves Normally Open (NO) • During x-feed the valve of the tank not supplying fuel closes when crossfeed is selected- no direct indication of valve pos.

  12. Motive Flow Shutoff Valve ctn. • ON Un’s 0002 – 0405 not modified by a SB- a pr. Sw. is installed in motive-flow line btn. eng.-driven pump and primary ejector pump- terminates start seq. when 180 psi is sensed in motive flow line. • The SB removes the sw. and start seq. terminated by gen. speed sensor sw.

  13. Fuel System Controls • Located on pilot’s IP- LH and RH Fuel BOOST pump switches control the elec. Boost pumps. • Each sw. has 3 pos.- NORM-OFF-ON • During normal ops the NORM pos. is used- the boost pump operates automatically during eng. Start, crossfeed, or when low fuel press. Is sensed in eng. Fuel supply line (will not come on if throttle in idle cutoff)

  14. Fuel System Controls ctn. • In OFF- boost pump operates automatically for eng. Start and when crossfeed is selected from the tank • In ON, pump operates continuously

  15. Indicating System • Capacitance-probe indicating system- compensates for changes in fuel density due to temp. • Each tank has 5 probes supplying info. To the vertical tape gauges in cockpit. • Indicator operates on D.C.- power loss indicated by an OFF flag in instrument.

  16. Annunciator Lights • 5 annunciator lights • Amber F/W SHUTOFF- illuminates when BOTH fuel and hyd. Firewall shutoff valves fully closed when ENG FIRE switchlight depressed. • Depressing the light a 2nd time opens the shutoff valves and turns off the F/W SHUTOFF light.

  17. Annunciator Lights ctn. • Amber FUEL PRESS LO- comes on when fuel pr. Drops below 5 psi, goes out @ 7 psi. • Amber FUEL LEVEL LO- actuated by a float sw. when usable fuel drops to approx. 169 – 219 lbs. • Amber FUEL BOOST ON- comes on anytime boost pump energized

  18. Annunciator Lights ctn. • A diff. pr. Of approx. 4 psi across either fuel filter the FUEL FLTR BYPASS lt. • Green INTRANSIT lights illuminate when power is applied to open or close crossfeed valves- goes out when valve is fully opened or closed.

  19. Fuel System Normal Operation • With FUEL BOOST switch in NORM- depressing an engine START button energizes the fuel boost pump. • Fuel then flows from manual shutoff valve – fuel filter – firewall shutoff valve – engine driven fuel pump.

  20. Fuel System Normal Operation ctn. • When start seq. terminates- motive flow from eng. Pump is directed through the primary ejector pump which provides fuel back to eng. Pump. • From primary ejector fuel is also supplied to 2 transfer ejector which transfer fuel from the tank low spots to the main sump.

  21. Fuel System Normal Operation ctn. • Crossfeed valves closed- each side supplies its own engine. • Firewall shutoff valve N.O. and can be closed by depressing ENG FIRE sw. • If fuel press. Is too low- FUEL PRESS LO light comes on- if FUEL BOOST is in NORM- boost pump energized (verify the FUEL BOOST ON light comes on). If press. Builds back light goes out but pump stays on.

  22. Fuel Crossfeed Operation • Either engine can be supplied from opposite tank or both engines from one tank. • I.E.- placing crossfeed selector in LH TANK electrically opens both crossfeed valves (grn. IN TRANSIT light during movement)- boost pump in left tank is energized (L FUEL BOOST ON annunciator). 3 sec. later the ft. motive-flow shutoff valve energizes closed (time delay to allow crossfeed valves to open & stabilize fuel press. Prior to shutting off rt. Eng. Motive-flow.

  23. Fuel Crossfeed Operation ctn. • In this case- left tank boost press. Gives fuel to left eng. And rt. Eng. Via open crossfeed valves. • Since motive flow shutoff valve in rt. System is closed- motive flow from rt. Eng. Pump cannot flow to primary ejector in rt. Tank. Therefore no fuel press. From rt. Tank can oppose x-feed pr. From left tank- both eng. Fed from left tank.

  24. Fuel Crossfeed Operation ctn. • Some fuel crossfed from left to right is directed to transfer ejectors in rt. Tank. Therefore left tank fuel is also being transferred to rt. Tank • Transfer rate = 600pph • Monitor FUEL QTY. for balancing • To verify crossfeed- monitor fuel qty. to observe qty. decreasing in tank selected and qty. increasing in opp. Tank.

  25. Fuel Crossfeed Operation ctn. • To terminate x-feed & return to normal- move x-feed selector to OFF • This opens the rt. Motive-flow shutoff valve. A few sec. later boost pump is shut off and both x-feed valves close (IN TRANSIT light on during movement) • System is now restored to normal.

  26. Fuel Crossfeed Operation ctn. • If electrical failure occurs during x-feed- both crossfeed valves fail in the position at time of pwr. Loss. • Motive-flow valve fails open. • If both engines operating, x-feed ceases since ea. Eng. Output is equal.

  27. Fuel Crossfeed Operation ctn. • If both FUEL BOOST ON annunciators come on when x-feed selected, both boost pumps are energized- x-feed cannot occur. • Try cycling the FUEL BOOST pump sw. for nonselected tank to ON then back to NORM- should de-energize pump in tank not selected and allow x-feed ops.

  28. Fuel Servicing • Consists of: fueling, adding anti-icing/microbial additives (mandatory in Citation II- .10 and .15% by volume), checking for contaminants and condensation. • Approved fuels: Kerosene Jet A, JP-S, Jet A-1, JP-8, Jet A-2, Jet B, JP-4, AV Gas (50 hours max. or 3,500 gal. btn. Overhauls)

  29. Av Gas • Previous av-gas limits apply if: • Fuel temp. </= 32C • Max. OAT (takeoff) is 32C • Boost pumps are operating • Hours entered in log- 1 hr. = 70 gal. • Max. operating altitude- 18,000 ft.

  30. THE END

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