FUEL STORAGE Chap. 3 AIRCRAFT FUEL SYSTEMS

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1 UNIVERSITY OF SALENTO SCHOOL OF INDUSTRIAL ENGINEERING DEPT. OF ENGINEERING FOR INNOVATION Lecce-Brindisi (Italy) MASTER OF SCIENCE IN AEROSPACE ENGINEERING PROPULSION AND COMBUSTION FUEL STORAGE Chap. 3 AIRCRAFT FUEL SYSTEMS LECTURE NOTES AVAILABLE ON Prof. Eng. Antonio Ficarella University of Salento - antonio.ficarella@unisalento.it REVIEW R00 DATE 2012/02/01 FILE RESPONSIBLE propafuelsfuelstorager01.odp Antonio Ficarella antonio.ficarella@unisalento.it DISTRIBUTION LIST REPLACE MODIFICATIONS REPLACED BY 1/21

3 AIRCRAFT FUEL SYSTEMS LECTURE NOTES AVAILABLE ON http://www.ingegneriaindustriale.unisalento.it/scheda_docente/-/people/antonio.

2 FUEL STORAGE 2/21

3 3/21 management of ullage above the fuel tank venting integral tanks bladder tanks

4 TANK GEOMETRY AND LOCATION 4/21 between forward and aft wing spars fuel weight acts in opposition to wing lift lower wing bending aluminum wing reducing the magnitude of stress cycling (take-off and landing) wing cavity very thin large number of measurement probes bending and twisting of wing trapped air pockets impair the performance of engine pump if ullage is not allowed to breath as aircraft climb or descend vent system

cavity very thin large number of measurement probes bending and twisting of wing trapped air pockets

5 5/21 sealing compatible with the fuels bonding straps across all the pipe to prevent lightning arcing fuel slosh during aircraft acceleration

6 6/21 fuel inertial forces during hard landing helicopter auto-rotation landing fuel tanks within the fuselage between the wings empennage behind pressure bulkhead additional center tanks horizontal stabilizer (long-range aircraft) active CG control

the wings empennage behind pressure bulkhead additional

7 7/21

8 OPERATIONAL CONSIDERATION CG shift due to fuel storage 8/21 in swept wing aircraft fuel will migrate aft during climb reducing the stability divide the wing tanks into a semi-sealed compartments that allow fuel migration inboard check-valves small bleed holes allow fuel and air to migrate (small semi-sealed)

wing tanks into a semi-sealed compartments that allow fuel migration inboard

9 9/21 4-compartments solution fuel pump in inboard compartment more gauging probes

10 10/21

11 UNUSABLE FUEL 11/21 large tanks even a fraction of inch can represent a significant amount of fuel inaccessible to the pump variation in fuel surface due to acceleration forces use of two fuel pumps spare-mounted pump loss of suction pressure (high altitude)

variation in fuel surface due to acceleration forces use of two

12 COLLECTOR CELLS 12/21

13 FUEL TANK VENTING 13/21 aircraft transition between ground and cruise altitude refuel process spillage of fuel to outside vent box towards wing tip

14 14/21 scavenge pumps to prevent fuel build-up taxiing on the ground centrifugal force dihedral reduced due to weight of wing forward acceleration and pitch-up will force fuel aft and (swept wing) outboard forward deceleration and pitch-down will force fuel forward and (swept wing) inboard a vent must be positioned outboard and aft float actuated valves that closed vent line when fuel is present

wing) outboard forward deceleration and pitch-down will force fuel forward and (swept wing) inboard

15 15/21

16 16/21 flame arrestor direct lightning minimize probability of icing a secondary pressure relief provision (burst disk, relief valve) outside air inlet shaped scoop for dynamic air pressure recovery improve pump performance in hot/high conditions vapor evolution

valve) outside air inlet shaped scoop for dynamic air pressure

17 17/21 flexibility of wing structure may move the high point in the ullage to some mid-span position ullage bubble

18 18/21

19 VENT SYSTEM SIZING 19/21 emergency descending loss of cabin pressurization worse case for emptying conditions (maximum ullage)

20 MAINTENANCE CONSIDERATIONS 20/21 ACCESS access to fuel tanks major concern to stress engineering CONTAMINATION fuel contamination water loss of all propulsive power coalescing filtration systems dissolved water can be present (80 ppm) wing tank cold during high altitude cruise during descent large quantity of outside air come into the ullage water condenses microbial growth

filtration systems dissolved water can be present (80 ppm) wing tank cold during high

21 WATER MANAGEMENT 21/21 water readily absorbed by kerosene (fuel appears clear) water in suspension cooling of warm fuel water as fine droplets that can turn into ice free water (water condensing) water drain valves at tank low points it takes a log time (a day o more) due to kerosene viscosity and density for this water to settle to the bottom use small ejector pumps to suck fuel + water from tank sump and to deliver to the main pump small amounts of water can be consumed in the engine water detection sensor FUEL TANK INERTING SYSTEMS Nitrogen Enriched Air (NEA)

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