Patent Application
20070040065
The present invention relates to an airborne mobile platform refueling boom having a flexible, pressure responsive end tube.
Aircraft refueling booms are well known in the art; however, each is associated with its share of limitations. For instance,
While overstressing of the boom may result while physically manipulating the boom during a refueling event, damage of the boom at the conclusion of refueling may also occur due to a fluid shock load. More specifically, if the maximum refueling pressure of the refueling boom is exceeded, then the boom may suffer the effects of “water-hammer” during receiver aircraft refueling. In order to lessen the effects of water-hammer, an internal fuel dynamic shock absorber bladder 40 is typically required in existing refueling booms. However, repairing and replacing such a bladder 40 is time consuming and expensive because removal of the entire refueling boom 10 is required for such a repair. Additionally, replacement or repair of the bladder 40 also results in the aircraft being out of service for an extended period of time since extensive repair hours are generally necessary. This aircraft downtime increases the overall cost of repair of the bladder 40 and the life-cycle cost of the refueling boom.
A need exists then for an aircraft refueling boom that does not suffer from the above limitations. This in turn, will result in a flexible aircraft refueling boom portion that is capable of accepting horizontal and vertical movements without subjecting the refueling boom to stressful loads during in-flight refueling maneuvering; a boom tube that is capable of expanding and absorbing shock loads attributable to fuel momentum pressure build up due to abrupt fuel starts and shut-offs to a receiver aircraft; a boom tube portion that can be quickly and easily removed from the aircraft and either repaired or replaced resulting in decreased aircraft downtime compared to existing refueling booms.
An airborne mobile platform refueling boom is disclosed. The refueling boom is typically used in connection with a refueling tanker aircraft, although the refueling boom could be employed with any form of refueling mobile platform, and is therefore not limited to use with just aircraft. In one embodiment the refueling boom utilizes an upper boom tube that connects to an aircraft underside, a lower boom tube that connects to the upper boom tube, and a removable flexible tube with a nozzle that is connected to the lower boom tube. The flexible tube is bendable to accommodate movement of the tanker aircraft relative to a receiver mobile aircraft during in-flight refueling of the receiver aircraft. Also, when the flexible tube bends, it signifies to a boom operator that the flexible tube is under a stress load. The flexible tube is also expandable about its longitudinal axis to absorb loading forces due to the conservation of momentum of the fuel being shut off or on during a refueling event. The expandable, flexible tube eliminates shock loads and pressure spikes in other areas of the refueling boom due to the expandability of the flexible tube.
A ruddervator is attached to the refueling boom to permit aerial control of the upper, lower and flexible tubes prior to and during refueling. The flexible tube is individually removable from the refueling boom, without removing the balance of the boom from the aircraft, to facilitate convenient and cost-effective maintenance. The removal of the flexible tube may be by a threaded connection, a push-on pull-off type connection, or other suitable mechanical quick disconnect method. In another embodiment, the entire refueling boom tube is either a rigid tube or a flexible, bendable hose with an additional end hose or tube that is expandable, resilient and equipped to be quickly connected and disconnected to the main refueling boom tube. A flexible, bendable and expandable tube eliminates the need for an internal shock bladder of prior art refueling booms.
The features, functions, and advantages can be achieved independently in various embodiments of the present invention or may be combined in yet other embodiments.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of various preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
An in-flight refueling boom according to the teachings of the present invention is generally depicted in
In an in-flight refueling operation, the refueling boom 100 is moved, known as “flying” the boom, by an operator, known as a “boomer”, in a vertical plane by manipulating control vanes 140, 145, referred to throughout the following discussion as “ruddervators” 140, 145. The control vanes 140, 145 are termed “ruddervators” 140, 145 because they act as a rudder and an elevator for maneuvering the refueling boom 100 when the refueling boom 100 is maneuvered into position over a receiver mobile platform, such as a receiver aircraft 200.
Continuing with the description of the refueling boom 100,
Continuing with reference to
At the end of the flexible refueling tube 180 opposite to the connection portion 170, is a nozzle 190. The nozzle 190 permits the flexible refueling tube 180 to lock into the receiver aircraft 200 to transfer fuel to the receiver aircraft 200. The receiver aircraft 200 has a receiver area 215 that contains a nozzle receiver 210, also known as a nozzle dock, for securely receiving the nozzle 190. The flexible refueling tube 180 permits the nozzle 190 to remain in the nozzle receiver 210 even when the tanker aircraft 110 is moving vertically to the extent permissible according to the flexible limit of the flexible refueling tube 180. That is, an advantage of the flexible refueling tube 180 is that either the tanker aircraft 110 or the receiver aircraft 200 can move in a vertical plane while refueling is taking place without jeopardizing the integrity of the refueling operation. Furthermore, the tanker aircraft 110 may also move laterally, or horizontally, since the flexible refueling tube 180 permits movement in both planes. This is a significant advantage over prior art refueling booms that normally have very limited horizontal movement capabilities. Additionally, the flexible refueling tube 180 will permit movement from the nozzle receiver 210 location in nearly any direction. To elaborate, once the nozzle 190 is connected to the nozzle receiver 210, the tanker aircraft 110 is free to move laterally relative to the original longitudinal hook-up axis of the refueling boom 100. Finally, because the flexible refueling tube 180 is flexible, curvilinear motion of the tanker aircraft relative to the nozzle receiver 210 is also possible.
Although various directions of motion are permitted by the flexible refueling tube 180, one advantage of the flexible refueling tube 180 over existing refueling tubes is the ability of a boomer to visually witness the bending and subsequently eliminate the bending by flying the boom to a different position relative to the nozzle receiver 210. Because of such an advantage, the flexible refueling tube 180 also eliminates the need for sensors used in conjunction with a conventional automatic load alleviation system (ALAS) (not shown) on the tanker aircraft 110. An optional ALAS monitors stresses and loading in existing refueling booms during in flight refueling since such stresses and loading can not be accurately gauged by the naked eye by simply viewing a rigid tube.
When the fuel flow is shut off during refueling, the fuel pressure spike resulting from the momentum of the fuel mass is absorbed and reduced by the expansion of the flexible refueling tube 180. As depicted in
A fuel valve that quickly closes, depending upon valve size and system conditions, may cause an abrupt stoppage of fuel flow that generates a fuel pressure spike or acoustic wave in the refueling boom 100. The fuel pressure spike can be a multitude of times higher than the fuel system working pressure during steady-state refueling. The expandable, flexible refueling tube 180 will expand like a balloon in accordance with the pressure changes in such a re-fueling event when a valve is suddenly opened or closed, relative to the steady-state flow. For instance, steady-state refueling pressure is normally below 55 psi; however, the spike pressure in the refueling boom 100, which results when a valve is suddenly opened or closed, may approach 240 psi. The pressure at which the expandable, flexible refueling tube 180 may begin to expand may be just above 55 psi. Of course the actual fuel pressure at which the expandable, flexible tube 180 may begin to expand may vary with the material used for the expandable, flexible refueling tube 180.
When the fuel pressure exceeds 55 psi, for example, a boom operator will be able to visually witness the physical expansion of the expandable, flexible refueling tube 180. The expandable, flexible refueling tube 180 can be made of any rubber or rubber-like material that is suitable for the transfer of liquid aircraft fuel. As such, an advantage of the expandable, flexible tube 180 is the elimination of the need for a separate internal bladder that is typically used with existing refueling booms. This also eliminates the need to remove a traditional boom from an aircraft to replace such a bladder, and furthermore, permits quick and easy connection of a replacement expandable, flexible refueling tube 180 according to the present invention.
Continuing with reference to
A general advantage of the second embodiment is the total overall flexibility of the refueling boom tube 400 when the upper boom tube 410 is connected to the lower boom tube 430. Another advantage is that the refueling boom tube 400 gains even greater flexibility than existing boom tubes, and the refueling boom 10 of the first embodiment, because both sections of the refueling boom tube 400 are flexible. This permits greater variation in the relative positions of the airborne mobile platforms during a refueling operation.
While various preferred embodiments have been described, those skilled in the art will recognize modifications or variations that might be made without departing from the inventive concept. The examples illustrate the invention and are not intended to limit it. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
