This invention relates generally to aircraft power delivery systems. More particularly, the invention relates to a technique for protecting cables and cable assemblies, and for facilitating movement of such cables across pavement at a terminal or other location at which aircraft may be parked.
Most aircraft have multiple power delivery systems which are used during different periods of operation. That is, electrical systems of an aircraft that is flying or taxiing on a runway are powered by an auxiliary power unit (APU) which typically includes an internal engine coupled to a generator or alternator, much as in a car. On the other hand, an aircraft that is parked is generally powered by an external power source. These external sources can be mobile generator systems or power units built into a terminal, passenger boarding bridge, or hangar.
To supply power to a parked aircraft from an external power source, the aircraft must essentially be plugged into the power unit. As with most devices that must be plugged in for power, the aircraft is connected to the power supply unit via a power cord or cable. The cable or cable assembly is generally selected based upon the voltage and current requirements. By way of example, an industry standard has been developed for certain aircraft power cables to supply power at a rated 260 amps and 400 Hz.
As can be expected, power cords used to plug in an aircraft are significantly larger than a standard household power cable. For example, these cables can have outer diameters on the order of 1 to 2 inches. Alternatively, some of these power cords can actually include several smaller cables bundled together. In addition, because the aircraft cannot always be brought into close proximity with the external power supply units, some cables must be quite long. In the case of commercial aircraft, these cables generally must stretch from a loading gate, or other location where the plane is parked, across the tarmac to the terminal building, where the power supply unit is located, or to a mobile power supply.
It can be appreciated that these cables, due to their length and thickness, are often quite heavy. For example, a 260 amp, 400 Hz cable of the type mentioned above, that is 60 feet long, can weigh in excess of 130 pounds. Operators must move these cables across the paved surfaces of the tarmac and runways to stretch the cables from the power supply units to the aircraft. Dragging a long, heavy cable across paved surfaces can be quite difficult and inevitably leads to wear and degradation of the cable insulating jacket.
One solution to facilitate movement of the cables across paved surfaces has been to coat the cables with a slick insulating jacket. This slick coating enables the cables to slide more easily across the tarmac and runways. However, this solution does not address the problem of wear on the cables, and over time degradation of the slick insulating jacket makes even these cables very difficult to maneuver.
Therefore, it would be advantageous to have a system that allows for easy maneuverability of aircraft power cables across paved surfaces while also protecting the insulating jackets of the cables from wear.