Fuel Tank Access Door for Aircraft

This invention relates to a fluid tight closure for an aperture, and more particularly, to a fuel tank access door for aircraft.

The fuel tank access doors used so far to gain access into the fuel tanks in the wings of aircraft, for inspection, present manufacturing and operational difficulties. Since the wings of aircraft are three-dimensionally curved, at least in its bottom skin where the fuel tank access doors are located, and since the wings are dynamic members undergoing twisting and bending movements in flight, the metal doors used so far have to be carefully machined. There has resulted that the fuel tank access doors used so far have been rather expensive to make particularly since such doors have to be leakproof despite all the aforementined adverse requirements. Another disadvantage of those metal doors is that they cannot readily be made of sheet metal and their manufacturing cost is therefore rather high. This is particularly noticeable since each aircraft is provided with a plurality of such fuel tank access doors.

It is a general object of the present invention to provide a fluid tight closure that meets the aforementioned requirements and avoids the aforementioned disadvantages of a fuel tank access door for aircraft.

It is a more specific object of the present invention to provide a fluid tight closure particularly adapted to form a fuel tank access door that is made at least in part of graphite/epoxy or fiberglass material to produce a light weight closure or door.

It is another object of the present invention to provide a fluid tight closure for a fuel tank, in particular for an aircraft, that is made partly of graphite/epoxy and partly of fiberglass material and is of fail-safe and low cost construction.

It is a further object of the present invention to provide a fluid tight closure for a fuel tank, in particular for an aircraft, that is made of graphite/epoxy material and ply construction, has sufficient flexibility to be made flat and be sufficiently bendable to conform to a curved outline such as of a wing, upon installation.

The above and other objects and advantages of the present invention will be better understood with reference to the following detailed description of a preferred embodiment thereof which is illustrated by way of example, in the accompanying drawing; in which:

FIG. 1 is a plan view of a fuel tank access door according to the present invention in position in the lower skin of a wing for an aircraft;

FIG. 2 is a longitudinal cross section as seen along line 2--2 in FIG. 1; and

FIG. 3 is an enlarged detailed view taken at 3 in FIG. 2 of a portion of one panel forming the door.

The illustrated fuel tank access door 1, forms a fluid tight closure, for an access aperture 2 in the lower skin 3 of a wing for an aircraft. As is well known, there is a plurality of fuel tank access doors in the wings of the modern aircraft. The fuel tank access door comprises an inner door panel 4 and an outer door panel 5. Each of the door panels 4 and 5 is laminated using plys of graphite/epoxy material such as the pre-impregnated or prepreg cloth No. 5208 marketed by Narmco.

The inner door panel 4 and outer door panel 5 are made with a rim portion 6 and 7 respectively that are complementarily transversely profiled relative to each other and to the edge portion 8 extending along the periphery of the access aperture 2. Thus, the rim portions 6 and 7 are arranged to engage each other and to sealingly clamp against the inner and outer faces respectively of the edge portion 2. A sealing ring 9 is engaged in a recess of the rim portion 6 to extend peripherally of the latter and provide sealing between this rim portion 6 and the edge portion 2. The inner and outer door panels 4 and 5 are formed with a flat central portion 10 and 11 respectively bordered by the corresponding rim portion 6 or 7.

The inner and outer door panels 4 and 5 are fastened in operatively clamping position by means of dome shaped nuts 12 and screws 13. The nuts 12 are secured to the inner door panel 4 on the inner side thereof. The screws 13 extend through the rim portions 7 and 6 to thread into the dome shaped nuts. Thus they clamp the panels 4 and 5 toward engagement of the central portions 10 and 11 with each other and of the rim portions 6 and 7 with each other and with the edge portion 2. The nuts 12 and screws 13 are sealed around for fluid tight connection.

Each door panel 4,5 is made of ply construction, with graphite/epoxy material as shown in FIG. 3 for the outher door panel 5. In this instance, the central portion 10,11 is made of only two plys while the rim portions 6, 7 have more plys. The plys are laid one over the other and cured at the required pressure and temperture to produce bonding by the epoxy. Such curing process is known in the art. In this particular instance good results are obtained by curing at 10 to 15 psi pressure and 260.degree. F., for about 60 minutes, thereafter at 100 psi and 350.degree. F. for 2 to 4 hours, followed by cooling down to 140.degree. F. under pressure.

The rim portions may be otherwise built up such as by molding of chopped fibers in resin.

The outer panel can also be made of other suitable materials such as of aluminum. Similarly, the inner door is made of fiberglass/resin material but can be instead made of suitable non-conducting materials.

The conductive layer on the outer door may be dispensed with if the material of the outer door is found to have sufficient inherent conductivity.