Technologies of towbar towing of aircraft
Астрономия и авиация
Technologies of towbr towing of ircrft The purpose of work is fmiliriztion with the bsic technologicl fetures of ircrft towing nd pushbck procedure sfety of towing procedure lbour precution issues. Filure to do so cn result in dmge to the ircrft cncelltion of flight delys or disruption of trvel for our customers pssengers s well s potentil dngerous dmge to other ircrft or vehicles. Fmiliriztion with the equipment nd towbrs being used including prctice with the pushbck vehicle nd ttched towbr to chieve necessry control to follow...
Laboratory work 1.8.
Technologies of towbar towing of aircraft
The purpose of work is familiarization with the basic technological features of aircraft towing and pushback procedure, safety of towing procedure, labour precaution issues.
Brief theoretical data
Part I. TOWBARS DESIGN AND APPLICATION SAFETY
TRAINING REQUIREMENTS FOR PUSHBACK & TOW CERTIFICATION
Being certified to complete pushback & tow carries with it a great deal of responsibility. This process should never be taken lightly. As the pushback vehicle operator or headset communicator, you must be certain that the process is completed in a safe and efficient manner at all times. Failure to do so can result in damage to the aircraft, cancellation of a flight, delays or disruption of travel for our customers passengers, as well as potential & dangerous damage to other aircraft or vehicles. It requires coordination, teamwork and absolute attention to the proper
completion of the process.
- Familiarization with the equipment and towbars being used including practice with the pushback vehicle and attached towbar to achieve necessary control to follow pushback lines and arrive at the equivalent final positioning of an aircraft
- Several pushback and/or tows under direct supervision of a trainer
INTRODUCTION TO TOWBARS
Towbars are a mechanical device designed to connect the pushback unit to the aircraft for the purpose of pushing or towing the aircraft from one position to another. Each towbar is designed for a specific aircraft or in a few cases for a series of the same type of aircraft. Each towbar consists of a Ring connector at one end to connect to the towbar to the pushback unit, and a specially designed head to connect to the aircraft at the opposite end. Most towbars also have a hydraulic pump system designed to raise and lower the towbar to assist in positioning for connection. Some samples are listed below: All towbars have a locking device as part of the head
assembly to insure that the towbar does not inadvertently separate from the aircraft.
There also shear bolts that will break away in the instance of too much force or torque being applied to the aircraft. Some towbar examples are listed below:
The tow bar is a specially designed heavy metal bar with hitching attachments on both ends, used solely for the purpose of pushing or towing of aircraft. The bar is connected on one end to the pushback vehicle and on the other end to the nose wheel of the aircraft. The Head of the tow bar which is connected to the aircraft nose wheel is equipped with shear pins. These are designed to ensure that the aircraft nose wheel is protected from damage in the event of excessive stress being exerted due to exceeding the turn radius. They will also shear off if excess force is used in attempting to push or pull the aircraft. As is the case with most ramp equipment, there are different types of tow bars as well as different manufacturers.
NEVER cross over a tow bar while an aircraft is motion
Insure that the correct tow bar is being used before attempting to connect it to any aircraft.
Verify shear pins are present and intact prior to using tow bar
AIRBUS 320 TOWBAR
An Airbus 320 (A-320) towbar can be used on A-320 fam. aircraft (A319/320/321). To attach the towbar to the aircraft, remove the safety pin and lift the lever back to open the towbar head. After making contact, close the head by lowering the lever. Replace the safety pin to lock the head in the closed position after it has been attached to the aircraft.
The DC-9 Towbar may be used on the following aircraft: DC-9, MD-80, MD-83 and MD-88.
The towbar is attached to the aircraft by manually moving the towbar into the center of the nose gear connection. Then raise the towbar and insert the tow pin into the axle at each side of the nose gear. Be sure the spring loaded pin is locked into the gear.
BOEING 727 TOWBAR
The B-727 towbar can only be used on B-727 aircraft.
This towbar is attached to the aircraft by manually positioning the towbar to the center of the nose gear connection. Proper height is obtained by either releasing the hydraulic valve on the hydraulic hand pump to lower the towbar, or by pumping the hydraulic hand pump to raise the towbar (make sure the valve is closed). To attach the towbar to the aircraft, remove the safety pin and turn the handle in either direction to open the head. After making the connection, close the head by turning the handle back.
NOTE: Replace the safety pin to lock the head in the closed position.
BOEING 757 TOWBAR
The B-757 towbar can only be used on the B-757 aircraft. To attach the towbar to the aircraft, remove the safety pin and lift the lever back to open the head. After making contact, close the head by lowering the lever. Replace the safety pin to lock the head closed. After securing the connection to the nosewheel assembly, use the hydraulic pump to raise or lower the towbar to the desired position for connection to the pushback unit.
BOEING 747 TOWBAR
The B-747 towbar can only be used on the B-747 aircraft. This towbar is attached to the aircraft by aligning the towbar with the nose gear pins. Then manually push the towbar into the nose gear pins and lower the handle to lock the head. Use the hydraulic pump handle to raise or lower the towbar to position at correct height to attach to the pushback unit.
PUSHBACK A 330 / 340 (only 200/300 series)
The nose gears A330/340-200/300 are fitted with an overtorque indication system. If the tow angle limit of 60° should be exceeded, the red warning light in the center of the nose gear will flash up (see pictures below) as well as an alarm in the cockpit will be activated.
In case the overtorque indication has been activated, local aircraft maintenance must be advised immediately to check the nose gear for damage and reset the system.
To avoid potential damages keep in mind:
DO NOT EXCEED THE MAX. TOW ANGLE OF 60°
Part II. TOWING (PUSHBACK) PROCEDURE
GENERAL PUSHBACK INFORMATION
“Pushback” is the action of moving the aircraft from its position at the gate onto a taxi lane or taxiway in order for the aircraft to proceed under its own power. Individuals assigned to pushback or towing responsibilities must receive proper training, and be certified by an accredited instructor. (Refer to introduction) Please note that local station training or management personnel are responsible for securing the training on any individual carriers pushback/tow procedures that are different from those in this manual.
Make sure the emergency brake on the pushback unit is released before the pushback unit is moved. The brakes must be in good working condition before connecting the towbar.
Do not remove the aircrafts chocks before the aircraft is ready to depart and the passenger bridge is fully retracted.
After the connection of the towbar and pushback unit has been made, set the emergency brake. Again, do not remove the chocks.
Communicate with the headset operator and safety wing walkers to understand the direction the aircraft will be pushed back. Make sure the crew has been fully briefed on their individual duties during the pushback operation.
At departure, the passenger bridge must be fully retracted before you start the pushback procedure. You may remove the aircraft chocks only when all cargo and passenger doors are closed, passenger bridge and all ground equipment has been removed from the aircraft.
Now that you are ready to begin pushing back, confirm with flight crew via headset operator, or if you are also headset communicator, advise flight crew “Ready for pushback, release brakes.” Receive confirmation for the flight crew “Roger, brakes released.” Release the pushback emergency brake then gently & slowly step on the accelerator. Do not slam your foot down on the accelerator pedal. Do not make sharp turns as you may not be able to recover and may damage the aircraft. Do not exceed the towing turn angle which is marked by red lines on the nose gear or on the nose wheel doors.
For stations with wing walking:
At all times during the pushback, you must maintain eye contact with the wing walkers in attendance. Should you lose eye contact with the wing walkers, stop the pushback until eye contact is regained. Never attempt a pushback without the requested minimum of wing walkers.
NOTE: Wing walkers must have wands (daylight) or lights (night time) during the pushbacks. Before pushback begins, remind wing walkers that they have a similar responsibility to insure constant eye contact during the process. Further, that they must immediately signal for stop should the aircraft path of travel appear to be endangered by potential collision with any obstacles, particularly in the wing tip areas. Pushing back into any area that has potential obstacles at the rear of an aircraft requires that wing walkers are also diligent in monitoring the path of the aircraft tail and any hazards in that pathway.
Pushback operators and wing walkers need to be aware of, and take into account the phenomenon of Wing Growth” when maneuvering an aircraft through a turn. The outside wing tip in a turning movement will travel in an extended path and creates a potentially dangerous situation if not taken into account. Both the driver and the wing walkers need to be aware of this issue and plan for it in monitoring the projected pathway of the aircraft and its wing tips.
After the pushback is completed, the headset operator or flight crew will tell you to stop. Gently step on the brake pedal to bring the aircraft to a smooth and safe stop.
Violent stops can damage the towbar, the aircraft, or both.
Disconnect the towbar from the pushback unit first. Do not drop the towbar. Slowly back up the pushback unit, place the pin back into the hitch, disconnect the towbar from the aircraft and reconnect the towbar to the pushback unit. The bypass pin may then be safely removed from the nosewheel mechanism. The Pushback unit should be positioned so that it is visible to the cockpit crew prior to release of the aircraft, unless it is being re-positioned immediately to execute another pushback or otherwise completely removed from the area around the aircraft. Before driving away from the aircraft, visually check to make sure the headset operator has disengaged the nose gear by-pass mechanism, thereby restoring the hydraulic pressure to the nose gear steering.
Towbars are equipped with “shear pins” (bolts) designed to break, if over stressed, and before damage occurs to the aircraft nose gear.
IF THIS HAPPENS DO NOT PANIC!
You should ease off the accelerator and gently step on the brake until you have come to a smooth stop. Immediately advise the headset operator to tell the flight crew what has happened and for the flight crew to set the aircrafts brakes. Remove the broken towbar and wait for another one before continuing the pushback operation.
Never pushback an aircraft with a damaged or broken towbar. Prior to using a towbar, the pushback or tow operator should check for the condition of the following items:
1. Towbar ring hitch does not display fatigue, excess wear, cracks or distortion
2. Towbar is straight and all elements are correctly aligned
3. Towbar Head Assembly is correctly positioned and firmly attached to towbar
4. Towbar Head Assembly Locking device is in place and functions correctly
5. All shear bolts are present, no visible signs of damage
6. Hydraulic pump assembly functions properly including pressure release valve
7. All tires are inflated if appropriate, all wheel assemblies are functional
If towing an aircraft includes crossing an active taxiway or runway, you must have radio communication with the Airport Tower and receive permission from them to effect the crossing.
Depending the local airport regulations, you might require an escort as well.
Check that the by-pass pin is installed or torque link disconnected on the aircraft nosewheel assembly prior to connecting the towbar to the aircraft.
After connecting the towbar to the aircraft, confirm the locking pin is secured (if applicable).
Always connect the towbar to the aircraft first and then to the pushback unit. Where applicable, use the hydraulic pump to raise the towbar to the correct height to be connected to the pushback unit.
Raise the towbar wheels before pushing out.
Never remove the aircrafts wheel chocks before all cargo doors, passenger doors are closed, the passenger bridge is retracted, and the aircraft is ready for push out.
Note: Handbrake must be set while the pushback unit is connected to the aircraft.
To briefly reinforce all of the proceeding steps, all of the elements listed below must have taken place before removing the aircraft chocks:
a. All aircraft bin and access panels must be closed and secured
b. Appropriate Pushback vehicle must be attached or mated to aircraft, and vehicle brakes or emergency brake must be engaged
c. All other GSE must have been removed from aircraft and repositioned outside of the “Circle of Safety”
d. Passenger access doors must be closed and secured
e. Aircraft Jet bridge or motorized/non motorized passenger stairs removed from aircraft vicinity.
f. Cockpit crew has indicated that aircraft is cleared for pushback and this information has been relayed to Pushback Operator or designated employee charged with overseeing pushback process.
g. Individual identified from item f. above has given appropriate signal to ramp crew to remove aircraft chocks.
During pushback, maintain eye contact with the wing walkers. If you lose eye contact, stop the pushback until eye contact is regained. Wing walkers have the same responsibility towards aircraft safety as does the pushback driver, and must signal immediately if aircraft is in any danger of collision with any obstacles.
Do not exceed the tow angle which is the red line on the nose gear wheel well doors.
Remember the phenomenon of “Wing Growth” on the outside wing during a turn.
After the pushback or towing is completed, lower the towbar wheels to support the towbar before disconnecting it from the pushback unit. REMEMBER, always disconnect from the pushback unit first and then from the aircraft. Do not drop the towbar. Employees that are connecting or disconnecting the towbar should never “Straddle” the towbar during this process. They must position themselves at the side of the towbar and maintain eye contact with the push back vehicle operator
After towbar is removed, confirm that the by-pass pin has been removed. Never remove a bypass pin while the towbar is connected. Severe injury or equipment damage can occur.
In general, the pushback operator must position the vehicle where it is clearly visible to the cockpit crew prior to releasing control of the aircraft to the pilot. Exception would be immediately leaving the area to position for the next pushback operation.
SPEED PUSHBACK AND TOWING
The towing speed is specified by the aircraft manufacturer, according to size and weight of the aircraft.
Please note that the towing speed must be adapted to the respective situation
(weather and ground conditions, visibility range etc.)
Always keep a safe distance!
Whenever towing an aircraft, keep a distance of at least 100 meters to the next aircraft ahead of you. In case of an abrupt and unexpected slow down of this aircraft you will need this distance to reduce the speed of the towed load in a safe way.
When towing an aircraft over and down sloping ramp or taxiway, you must reduce speed accordingly, in order to maintain sufficient braking capability in the event that you are required to stop the tow.
Pushback speed = walking pace
WINTER OPERATION TOWING AND PUSHBACK MAY REQUIRE A REDUCTION IN THE SPEED OF THE PROCESS
Low visibility due to fog or rain, but in particular snow and ice reduce the traction and stopping capability of the pushback vehicle, increasing the risk during pushback and towing operation.
When the apron is covered with snow or ice… drive slowly and act with appropriate caution apply the brake carefully never apply the brake in a turn do not make sharp or tight turns during pushback operations do not give the clearance for engine start up until pushback is completed do not push or tow an aircraft through a great deal of snow. Frozen snow can damage landing gears and engines
Pushback and Towing
Aircraft Pushback is the process of moving an aircraft in to, or off of the gate and into an identified area on the ramp to then to proceed under its own power to a taxiway for take off. This is accomplished through the use of an Aircraft Tractor designed specifically for this function. The most common type of tractors use a “Towbar” to connect to the aircraft nose wheel. Example of Swissport Conventional Tug in Manchester
Towing an aircraft also requires one of the aircraft tractors described previously. Towing may involve moving an aircraft into a gate, a remote site, hangar or re-positioning air aircraft from one gate to another. It may also entail using active taxiways on runways. Individuals assigned to these tasks must receive additional classroom and hands on training before being certified to accomplish this very critical task.
They may also need to receive training and licensing from local airport authorities. Part of that
training includes all of the communication requirements with cockpit and control towers in order to insure the safety of the aircraft being towed as well as coordinating movement on active taxiways or runways.
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