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CHAPTER 3

FUEL SYSTEM

3.1.

State the major components of the fuel system and their functions.

1.

Fuel Cell – (91 gal new B & all C; 76 gal Old B)

2.

2 fuel boost pumps – Prevents vaporization in the fuel lines above 6000 ft PA by pressurizing the line at 4-30 psi.

3.

fuel quantity measuring system – 2 floats, 1 gauge calibrated in Gal.  Fuel Low Warning System: 20 Gal fuel low switch and Caution light

4.

Pressure Indicating system – Each fuel boost pump has a 3.5 psi pressure switch and they both are connected to Caution light.  A fuel pressure transducers located between fuel cell and fuel shutoff valve and sends a signal to the fuel pressure gauge.

5.

Shutoff Valve – 28 v dc shutoff valve with a thermal relief feature located just above fuel cap in main fuel supply line.  If DC power is lost it will stay in the last energize position.

6.

Airframe fuel filter – Impending Bypass function, trips caution light.

7.

Engine Fuel pump / Filter – Low pressure (4-30 psi) bypassable filter element filters fuel and delivers it to the pump which pressurizes the fuel (650-750 psi) and since it to the Ng fuel control unit.

3.1.1.

Identify the characteristics of the fuel cell.

Single bladder-type fuel cell, located below and aft of the passenger seat, is crash resistant, but not self-sealing.  

Capacity

91 Gal (late model B’s and all C’s)

76 Gal (early B’s BUNO 161XXX)

3.1.2.

Identify the methods used to re-fuel the fuel cell.

Early B’s – Gravity fueling only

Late C B’s and all C’s – Gravity and Pressure fueling.  (125 psi max press)

3.1.3.

State how the fuel boost pumps and their components work to supply fuel to the engine and information to the pilot.

Two pumps (4-30 psi), connected in parallel, energized anytime the 28 vdc boss is energized.  Each plant has a 3.5 psi pressure switch to indicate failure to a common FUEL PUMP Caution Light.

3.1.4.

Identify the various fuel pressure limitations and the associated operational restrictions.

Allowable fuel boost pump pressure limits are 4-30 psi.  Fuel pump light comes on when either pump pressure falls below 3.5 psi.  If one fuel boost pump fails the fuel pressure gauge will still read 4 – 30 psi, if both pumps fail the gauge will read 0 psi.  If either (or both) fuel pump(s) fail you must descend below 6000’ PA.  Minimum usable fuel becomes 20 gal.

3.1.4.1.

Identify the various pages, switches, etc., that relay pressure information, along with their limitations.

9

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