AIRBUS INDUSTRIE A300 TOWING

Transcription

1 TOWING 1. General The A-300B is designed with means for conventional tractor towing. Two tow fittings are provided on the nose gear, one at the front and one at the rear (ref. Figs. 1) The front fitting serves for forward pulling or rearward pushing, with the tractor placed forward of the nose gear in either case. The rear fitting serves for rearward pulling, with the tractor placed aft of the nose gear, under the fuselage (ref. Figs. 2 and 3). Towing is also possible from the main gears, both forward and rearward, using a conventional tractor and a cable with two specific fittings which attach to lugs on the main gear bogie beams. 2. Approximate Towing Loads Aircraft towing forces cannot be accurately calculated. They can only be established through experience or testing. For the A-300B, as for most aircraft, the following maximum values have been set - Breakaway on dry level concrete: 6% x W - To maintain rolling on level surface: 3% x W -Breakaway on slope: 6% x W +,1% x W per 1% slope - To maintain rolling on slope : 3% x W + 1% x W per 1% slope NOTE: - In all above formulae, W = gross airplane weight. -When the aircraft is pushed rearward with the engines idling, the engine thrust resistance must be added to the above formulae values. Moreover, the following coefficients of friction between the tow tractor tires and the ground have been adopted

2 - Dry concrete or asphalt: Wet asphalt: Wet concrete: Hard snow: Ice: 0;05 The tractor drawbar pull required under various conditions, as well as the traction wheel loading necessary to prevent slippage are shown graphically in Fig. 6. As an example, the dotted line represents an aircraft weighing 290,000 lb (131,542 kg) being pushed rearward on wet concrete up a 2% slope, with the engines stopped. As shown by the graph, such conditions require a 19,500 lb (8,845 kg) drawbar pull and a. minimum 33,000 lb (13,745 kg) load on the traction wheels. If the aircraft is being towed or pushed against engines idling, a 24,050 lb (10,900 kg) drawbar pull and a minimum 42,350 lb (19,190 kg) load on the traction wheels would be required. 3. Limit Loads and Angles The limit towing loads and angles are shown in Fig. 6. Whatever towing arrangement used, the steering angle allowed on each side of the aircraft centerline is only 95 when control lever on the interphone box is disengaged and locked in this position with a special pin. If the lever is not locked, the angle is limited to 65 on each side of the centerline. The torque links cannot be disconnected to obtain a greater steering angle. The steering angle is limited to 40 in case of rearward pulling using rear fitting, with the tractor under the fuselage, and the engines idling. This is reduce possibility of fan ingestion (Ref. Fig. 2).

3 4.Tow Tractor The ATA Ground Equipment Subcommittee has developed a Technical Specification for the design of a tow tractor to handle aircraft weighing up to 600,000 lb. This document was used by representatives of European Airlines in preparing their specification for a "so-called" Category II tractor. It is obvious that any tractor built to that specification will fully meet the A-300 requirements. 5. Nose Gear Tow Bar A. Towing by Nose Gear Front Fitting A conventional type tow bar is provided ; it is equipped with a damping system to protect the nose gear against jerks, and with towing shear pins for gear protection against excessive loads. Shearing of a towing pin will be indicated by an aural warning if it occurs while the aircraft is being pushed rearward. B. Towing by Nose Gear Rear Fitting The tow bar used in this instance is similar to the preceding one; it differs by its length which is limited to 2500 mm (98.43 in.) and by the absence of an aural warning device. 6. Towing by Main Gears (Ref. Fig. 4) Forward or rearward towing by the main landing gears uses two fork-shaped fittings and a cable. The two fittings, which are specific tools, attach to lugs provided: atop each end of the gear bogie beam. The front lug also serves for pitch damper attachment. The cable which links the two fittings to the tractor, via a pulley, is approximately 50 m (165 ft) long. This length is sufficient for the tractor to be - placed ahead of the nose gear during forward towing.

4 The two fitting/cable set is provided with a safety shear pin calibrated to 3060 mdan ( lbf/ft) 7. Landing Gear Downlock Ground Safety Pins If required, all three gears may be mechanically locked in the "down" position during towing by inserting ground safety pins in the nose gear telescopic drag strut and in main gear locking rods (ref. Fig. 7). 8. Electrical Power Requirements during Towing When the aircraft is on tow the following listed items need an electrical ground supply. This should be taken from an alternator mounted on the tractor and connected to the ground power receptacle. ITEM LOAD Navigation lights KVA Collisions lights KVA Interphone KVA V. H. P KVA Galleys (optional) KVA Fuselage interior lighting KVA Inertial platform KVA The supply must be 400 c. p. s. (Hz) three phase, at 200/115 Volts.

5

6

7

8

9

10

11