Tugs and Tractors in the aviation industry are called pushback vehicles, operated to maneuver an aircraft from its parking position, usually from an airport gate. IATA defines aircraft pushback operation as “rearward moving of an aircraft from a parking position to a taxi position using specialized ground support equipment.” Pushback operation is often considered a critical airport procedure carried out by Tugs and Tractors, unique low-profile vehicles to facilitate aircraft movement in the taxiways.
The operation is called Push “back” because the Tug driver does the steering, not by the aircraft pilot, since the pilot cannot see what is behind the aircraft. A Towing mechanism with a bypass pin is installed into the nose gear to disconnect it from the aircraft’s standard steering mechanism to connect tug to the plane. Once the pushback operation is completed, the towbar is disconnected, and any bypass pin is removed, following which the aircraft can taxi forward under its power.
Aircraft tugs are classified into several types. However, for the selection of tug, the following classifications can be considered:
Towing capacity is the tugs’ ability to pull or push a certain aircraft weight and is primarily dependent on the amount of traction generated by the tug. Eagle, a market leader in manufacturing GSE (ground support equipment), supplies tugs of different tow capacities as described below:
Small and lightweight airplanes are maneuvered by the ground staff using the aircraft’s nose or tail wheel. However, for heavier commercial and military aircraft, external power drives are necessary. Most commercial tugs are powered by IC (internal combustion) engines or electric/battery-powered mechanisms. Few tugs also operate on gas-powered mechanisms.
Preventative maintenance (PM) is a proactive technique that follows a defined maintenance routine to assess all the tug and tow components before their breakdown, avoiding downtime losses and unexpected repairs.
Tug maintenance schedule includes repair and inspection of the following components:
|Sr.No||TUG COMPONENT||PARTS TO INSPECT||MAINTENANCE ACTIVITY|
|1||Engine Housing||Cylinder block and head||Inspection for wear and surface crack|
|2||Engine Gas distribution system||Air intake, inlet valves, Exhaust systems, exhaust valves||Inspection of Valve timings and piston rings|
|3||Shafts||Engine crankshaft and camshafts||Vibration readings (linear or torsional) as per ISO 10816|
|4||Lubrication and cooling systems||Lube oil filter, oil quality, pump, and sump||Inspection of lube oil pressure for every use. Lab oil analysis at 50 running hours, pump vibration analysis, oil sump accumulation, and filter inspection at every oil change interval|
|5||Lubrication and cooling systems||Water jackets and pumps||Vibration analysis of pump and leakages or contamination of oil or coolant|
|6||Electrical system||ECU, Sensors, Actuating mechanism, and alternator||Functioning of DC components, alternator, emergency lights. Sensors (MPU Speed sensors), governor actuation, and alternator slip|
|7||Transmission and Differential||Gearbox, Clutch, and Differential gears||Inspection of gearbox vibration levels, gear teeth wear, clutch efficiency, and differential gear damages|
|8||Wheels and Brakes||Tires, axle, and brakes||Tire pressure, damage, axle bolts, brake actuation, and efficiency check|
|9||Steering and Chassis||Steering wheel, connection with axle, chassis, and suspension||Inspection of steering angle at full load, tug suspension, and connection lag with axle|
|10||Hydraulic systems||Plunger, oil pressure and level, leakages, and valves||Inspection of oil level, pressure leakages due to hose damage|
In addition to tug components, towing and tow bar mechanism PM (preventative maintenance) shall also be carried out as described below:
In addition to the PM inspections mentioned above, operational checks should also be followed daily as the OEM (Eagle) recommended.
Although establishing and adhering to a PM program requires stringent control measures, they often prove beneficial for the aircraft operator in the long run. Following are few direct and indirect benefits of the Tug PM program:
e2b calibration offers industry-leading consultancy and certified PM services for your aircraft tugs. Our labs are ISO/IEC accredited and operated by a team of qualified experts providing training and consultancy services on Tugs maintenance and inspection. Our verifiable services are unmatched in the industry. Contact e2b calibration for all your equipment calibration needs.