(11)
If the engines have been run on the contaminated fuel, apply the procedure described above and replace the engine fuel filters and clean the filter bowls.
(12)
If the engine has been subjected to continuous or long-term exposure to fuel contaminated with dye, a thorough inspection of the engine fuel system and components, including fuel nozzles and turbine blades should be conducted. The individual engine and APU manufacturers should be consulted for appropriate procedures for the equipment.
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INTEGRAL FUEL TANKS -DESCRIPTION AND OPERATION
1. General
A. The integral fuel tanks provide all the fuel supply storage capacity. Tanks No. 1 and 2 are located in the interspar area of each wing. Tank No. 1 is contained entirely in the left wing and tank No. 2 entirely in the right wing. The center tank is contained entirely within the fuselage. It is a box section formed by the extension of the front and rear spar and the upper and lower wing skin. Two beams span the center section to form three separate cavities (Fig. 1).
B. The sealed structure of the wing and center section provides the fluid tight boundary of the integral fuel tanks. This is accomplished by a close fit of metal to metal parts and through the use of wing skin, spars, ribs, stiffeners, stringers, and doublers as the periphery of the tanks, and applying sealing materials at areas where these members join. Sealing materials are generally synthetic rubber; either in molded form (O-rings, gaskets, etc.), or in an uncured state (for brush or gun application). Use of sealant is held to a minimum to avoid excess weight.
C. The wing ribs and spanwise beams in the integral tanks act as baffle plates to prevent excessive fuel surges. Two of the wing ribs in tanks l and 2 contain a series of baffle check valves to prevent fuel flow away from the fuel boost pumps. The spanwise beams in the center section contain fuel flow equalizing holes to allow a free flow of fuel between the beams.
D. Fuel tanks 1 and 2 are each fitted with an overwing filler port. The center tank being located in the fuselage does not have a gravity fill port.
E. The low points in integral tanks are fitted with fuel sump drain valves to permit draining accumulated water from the fuel tanks and for draining fuel from the sumps when a tank is defueled.
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F. Located within the fuel tanks are the fuel lines, pumps, valves, vents, drains and sensing equipment required for operation and monitoring of the fuel system. Access to the interior of the fuel tanks is provided through removable access panels. The access panels for tanks 1 and 2 are in the wing lower skin. Access openings in the tank ribs are provided for areas not accessible directly through the tank access panels.
G. The wing center section is divided into three cavities by spanwise beams. The cavities are numbered 1, 2 and 3 starting with the forward cavity and going aft. An access panel in the bottom skin of No. 1 cavity provides access to wing center section cavity. Man-size openings in the spanwise beams provide access between cavities.
H. The wing center cavity has a secondary external barrier coating on the upper panel and front spar to prevent fuel vapor from entering the pressurized section of the fuselage. Fuel tanks use the sealed structure of the wing to maintain a fuel boundary. This is accomplished primarily by close metal to metal fit of all parts, by sealed fasteners, and by the application of sealing compound to the structure. Optimum sealing is made possible by the use of open section stiffeners throughout the wing which eliminate blind areas. Fillet sealing is used at the spars, fuel vent ducts, and skin splice stringers. Rivet seals are achieved by control and orientation of the driven head.
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2. Fuel Tank Access Panels
A. Access to equipment located inside fuel tanks is provided by removable access panels, located between the wing ribs, in the wing lower skin. For ease in identifying the panels, and also referencing them throughout this chapter, they are numbered consecutively from the wing root outboard. The panels in the wing lower skin are numbered 1 thru 14 and one panel is located in wing center section.
B. The fuel tank access panels are cast aluminum or on airplanes incorporating SB 28-1064 and/or SB 28-1078, panels 2 and 3 and/or 1, 4, 5, 6 are high impact resistant aluminum honeycomb. Cast and impact resistant panels are not interchangeable. The panels are mounted inside the tank. The panels are installed by inserting screws through a clamp ring on the outside, flush with wing panel and threading the screws into captive nuts in the access panel. A molded rubber seal ring, fitted into a groove in the panel seal face provides a static-type fluid seal between the access panel and the wing skin.
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