May it be Rotary Wing (Helicopter) or Fixed-Wing (Airplane), a key weakness that has been present for any aircraft is its very limited ability to perform ground maneuvering independently. That is why to aid aircraft maneuvering on the ground, equipment such as Towbar and Tow Tug are used to maneuver the aircraft.
Aircraft ground maneuvering is achieved by connecting an approved type of towbar usually to the nose landing gear of the aircraft. The type of towbar used on this operation is unique to each type of aircraft to ensure that the towbar specification and limitation meets and exceeds the weight and stress that pushing or pulling the specific aircraft will produce.
On the other end of the towbar, the tow ring allows the Towbar to be connected and secured to the Tow Tug. The Tug-Towbar-Aircraft connection allows the maneuvering of the aircraft on the ground to be controlled by the Tow Tug Operator independently. This ensures that the movement of aircraft is safe from collisions and taxiway excursion as the larger the aircraft gets, the visibility of the pilots on the ground markings decreases and the difficulty for maneuvering greatly increases.
Whenever it is not possible to connect the towbar to the nose landing gear due to a defect in the aircraft, it is possible to connect two separate towbar to each Main Landing Gear to enable ground maneuvering.
Aircraft towing and Push back are performed due to different reasons. The most common scenario is the Push back of aircraft from the apron every time the aircraft is set to depart. This procedure is also applicable whenever the Ground Controller commands that engine starting is only allowed at specific locations due to exhaust or noise restriction.
Towing is most commonly performed whenever the aircraft is required to change location such as unplanned replacement of an aircraft assigned to a flight with a reserve aircraft due to defect, positioning of aircraft on approved locations wherein engine run-up maintenance can be performed, towing of aircraft to/from maintenance hangars or bay and rescuing of aircraft that are unable to move due to accident either in the runway or taxiway.
As towbars are an expensive investment for Air Operators or Ground Service Providers, it is a must that the GSE Department ensure that equipment such as the towbar has an Annual maintenance plan and is strictly implemented through successful completion of upkeep and maintenance servicing.
Perhaps the most important part of a towbar that is easily disregarded because of its small size is the Shear Bolt. It is considered as the first line of defense whenever the tension or the pulling force between the Tug and the Aircraft exceeds its limitation. It prevents the tow bar from snapping into two and damaging the aircraft or worse causing injury to the ground servicing crew. It is strongly suggested that when it comes to this component, progressive preventive maintenance should be performed. This means that the Shear Bolt should be replaced once it has reached a specified accumulated day that it has been installed or after it has been used for a specific amount of frequency.
Body of the Towbar
Another important component to be inspected of damages, such as nicks, dents, crack, and/or deformation, is the body of the Towbar itself. Remember that the smallest damage would eventually get bigger as the stress applied during usage causes the material to further weaken until it reaches the point of total material failure.
The towhead which is the component that connects and holds the tow bar body to the nose landing gear attachment point requires an inspection to make sure that the whole component is free from cracks, deformation or corrosion. As it is the only component of the towbar with direct contact with the aircraft structure, the possibility of corrosion in the towbar be transferred to the aircraft structure itself and cause an inevitable aircraft unserviceability should not be disregarded.
The oleo-pneumatic pump and tire carriage also requires frequent inspection and servicing to make sure that any damage or defect is serviced before it gets worse. The oleo-pneumatic pump requires oil servicing to make sure that during operations, the wheel carriage retracts or deploys without any difficulty. The pump itself needs to be serviced by replacing worn-out seals that can cause a fluid leak.
Nitrogen Pressure of the Oleo-pneumatic Pump
Last but not the least, the nitrogen pressure of the oleo-pneumatic pump and the wheel needs to be measured and serviced once found deficient to ensure that the continuous use of the Towbar is safe and would not cause an accident or delay. It is strongly recommended to use Nitrogen on these components as it is more stable than pressured oxygen and most importantly, it is less flammable.
We understand that not all organizations are equipped with the right manpower, experience or equipment to properly service the towbars. Improper servicing can result in further towbar damage or failure during aircraft ground operation which can result in very expensive aircraft damage or cause a personal injury, which is why it is important to consult organizations that provide professional towbar servicing and maintenance.
e2b calibration is a 17025 accredited calibration laboratory employing ASQ certified technicians located in northeast Ohio. We pride ourselves in offering on-site calibrations throughout the United States as well as a wide variety of GSE service offerings including, but not limited to extensive towbar maintenance. For more information contact e2b calibration.
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