© ISO 2016 Aircraft ground equipment — Nose gear towbarless towing vehicle (TLTV) — Design, testing and maintenance requirements — Part 1 Main line aircraft Matériels au sol pour aéronefs — Tracteur s[.]
General
4.1.1 Towbarless tow vehicles (TLTVs) shall comply with the applicable general requirements of ISO 6966-1.
4.1.2 Airframe manufacturers should provide information for each aircraft type which allows TLTV manufacturers or airlines to self-test or evaluate the towbarless tow vehicles themselves.
Refer to the airframe manufacturer’s documentation for evaluation requirements and detailed testing procedures that may be different from or additional to those contained in this document.
TLTV manufacturers are required to supply customers or regulatory agencies with a certificate of compliance or similar documentation This serves as proof that successful testing and evaluation of a specific tow vehicle and aircraft type combination has been conducted in accordance with this document and the relevant airframe manufacturer's guidelines.
This certificate permits the operation of vehicles on designated aircraft models and types It must be issued under a quality control program that complies with ISO 9001 or an equivalent industry standard.
Towing loads
The towing forces exerted by the TLTV on the aircraft's nose landing gear during acceleration or braking must be verified according to Clause 5 and/or Clause 6 These forces must not exceed the maximum limits established by the aircraft manufacturer at any time.
The TLTV is designed to accommodate various aircraft types, allowing for the use of preset towing load values for multiple aircraft types or sub-types within a specific Maximum Ramp Weight (MRW) range.
Each TLTV setting must adhere to the maximum limits established by the aircraft manufacturers for the specific types, sub-types, or families of designated aircraft Additionally, each TLTV setting requires individual verification.
Pick-up and holding system
4.3.1 The TLTV’s nose landing gear pick-up/release device should operate in a smooth and continuous manner.
To ensure optimal performance, it is crucial to avoid abrupt or oscillating loads during the pick-up and release sequence The design should focus on minimizing these loads, ensuring that the drag loads experienced during this phase remain significantly lower than the peak loads encountered in typical operations.
4.3.2 The maximum loads induced by pick-up and release sequences shall be measured either on an aircraft or on a fixture representative of the nose gear geometry.
The vertical load on the nose gear must match the fatigue justification load specified in the airframe manufacturer’s documentation Additionally, the maximum lift height of the nose gear should not surpass the limits outlined in the manufacturer's guidelines, if available.
Oversteering protection
4.4.1 The maximum angular or torsional load limits stated by the aircraft’s manufacturer in the event of oversteering shall not at any time be exceeded.
See aircraft manufacturer’s TLTV assessment criteria document.
4.4.2 This may be achieved either by oversteer protection built into the TLTV, or by an oversteer alerting system being provided.
Oversteer protection can be implemented through intrinsic design that prevents reaching or exceeding critical limits, or by utilizing a fail-safe system that guarantees these limits are not surpassed.
Oversteer alerting shall consist in an appropriate fail-safe warning system installed on the TLTV, providing the driver with unmistakable indication that one of the maximum limits was reached.
Testing of the TLTV oversteer protection and alerting systems must not be conducted on in-service aircraft to avoid potential damage to the NLG structure or steering system.
Such testing should be accomplished with a suitable ground testing device representative of the specific aircraft model for which the TLTV is intended or through appropriate numeric simulation demonstration.
Aircraft registered or operated under EASA CS-25 paragraph 25.745(d) and associated AMC 25.745(d) require TLTV manufacturers to provide a Declaration of Compliance for their oversteer protection or alerting systems This declaration must align with current International Standards and the criteria set by the aircraft manufacturer for each specific aircraft type Additionally, aircraft manufacturers are responsible for documenting the TLTV models that have been accepted for each aircraft type based on this Declaration of Compliance.
Nose wheels retention
The vehicle must securely hold the nose wheels to ensure that pitch-up of the aircraft does not result in the wheel disengaging from the pick-up device, regardless of the nose gear steering angle.
A positive wheel retention feature is essential to accommodate uneven loading on the nose gear during turning maneuvers, especially if the nose gear is canted When the gear is canted forward or aft, the vertical load on the inboard nose wheel increases while the load on the outboard nose wheel decreases This retention feature must enable tire displacement without adding extra loads to the nose gear.
The design of the holding device must ensure that it does not interfere with any part of the aircraft structure, including components such as torque links, weight and balance sensors, tires, and water spray deflectors This requirement applies across all wheel steering angles, adhering to the limits specified in the airframe manufacturer's documentation, as well as accommodating the complete range of shock strut extensions and tire deflections.
Surface contact area between pick-up device and tire surface should be sufficient to preclude unacceptable tire loading (refer to tire manufacturer for bearing pressure specifications).
Safety
Pick-up, release and associated loads
4.6.2.1 During the loading sequence, safety equipment shall inhibit any movement of the loading device if the nose wheel is not properly positioned.
Positive clamping and correct positioning of the nose wheel shall be ensured.
4.6.2.2 When the positioning pick-up/release sequence involves a relative motion between the vehicle and the aircraft, only the vehicle shall be allowed to move (see 4.2).
The aircraft parking brake should be applied or wheels properly chocked during this phase TLTV design shall ensure that no loads higher than authorized are applied to the aircraft.
4.6.2.3 In order to avoid damage to the aircraft, the net load from all points of contact between the vehicle and nose gear tires shall be limited (on “X” axis) at a value lower than or equal to the operational limit.
Any single failure of the tow vehicle’s load limiting system shall not cause loads which exceed the maximum limits.
4.6.2.4 If the pick-up/release sequences are fully automatic, an emergency stop or deadman switch shall allow the operator to freeze the sequence at any time.
An automatic or manual system shall allow reversal of the sequence and restore the starting position.
Acceleration, deceleration and associated loads
4.6.3.1 If towing is attempted while aircraft brakes are applied or wheel chocks are in place, a safety device on the TLTV shall limit the maximum static force to the safety limit as defined in 4.6.3.2 a).
4.6.3.2 The vehicle’s maximum pulling and braking forces shall be limited to the maximum permissible nose landing gear loads of the aircraft (see airframe manufacturer’s documentation and FAR/EASA CS paragraph 25.509).
A primary maximum load limiter must be installed to restrict loads on the nose gear according to the airframe manufacturer's specifications, and it cannot be overridden; any activation of this limiter is a recordable event Additionally, a secondary operational load limiter may be implemented to reduce operational loads, which will inhibit further loading efforts if limits are exceeded during acceleration or deceleration, returning the engine to idle or the gearbox to neutral without braking This safety system can only be reset when the vehicle is stationary, and no record of such an event is required.
4.6.3.3 Control of the loads may be based either on a limitation of the acceleration/ deceleration or on a limitation of the tow force/brake force It may also be possible to control tow forces by controlling acceleration/deceleration.
Emergency braking
Incorporating an emergency braking system in the TLTV ensures that the braking or decelerating load remains within the maximum allowable limits of the nose landing gear, although it may surpass operational limits Additionally, it is crucial to safeguard the activation of the emergency braking system against accidental triggering.
Oversteer limits
4.6.5.1 Oversteer angular and torsional limits are not to be exceeded Oversteer testing should not be performed on the aircraft.
4.6.5.2 For European registered or operated aircraft, the EASA CS-25 [CS 25.745(d)] require oversteer alert or protection systems on the aircraft or the TLTV (see 4.6.6) If a TLTV is designed to meet EASA CS-
TLTV manufacturers must conduct testing to verify the vehicle oversteer limit alerting or protection functionality at an appropriate test facility It is essential for TLTV manufacturers or airplane operators to consult with the airframe manufacturer or local aviation regulatory authorities to ensure compliance with current regulations.
4.6.5.3 The maximum steering angle for conventional tow bar towing, as listed in the airframe manufacturer’s documentation, is applicable for nose gear towbarless towing, unless otherwise noted.
Airframe manufacturers may establish different maximum steering limits between conventional tow bar and towbarless towing due to the absence of shear protection provided by traditional tow bar connections.
Oversteer alerting and/or protection
4.6.6.1 The tractor shall be equipped with a fail-safe oversteer alerting/indication or protection system that a) activates an in-cab (red) warning light and audible alarm to indicate the maximum safety limit has been reached, and b) requires a specific recordable action to complete the pushback/towing operation, in order to make it unmistakable to the tow vehicle driver that an inspection of the nose landing gear by an authorized engineer shall be initiated.
4.6.6.2 In addition, it is desirable that the device activates an in-cab (amber) warning light and audible signal to indicate an operational limit has been reached The oversteer indication system shall allow sufficient time for the tow vehicle operator to take appropriate action to avoid reaching a safety limit. 4.6.6.3 The system shall be automatically activated when the airplane is coupled to the tow vehicle.
4.6.6.4 The oversteer indication and/or protection system shall be designed to protect the range of aircraft types that can be handled by the tow vehicle.
Oversteer is defined as exceeding maximum allowable steering angle or torsional load.
4.6.6.5 An optional system may provide a structural fuse (or other reliable load limiting system) on the tow vehicle which will prevent the application of torsional loads on the nose landing gear that exceeds the airframe manufacturer’s specified maximum limit.
Testing operations
Snubbing and jerking
Snubbing and jerking effects or movements should be avoided during testing.
Vibrations
If severe or abnormal vibrations occur, testing should be discontinued and the cause determined.
Aircraft braking
Aircraft brakes should only be used in emergencies while being towed by a TLTV, as braking can exceed design loads and cause structural damage or nose gear collapse To prevent this, airlines should implement measures to avoid braking during normal towbarless towing Compliance with the carrier's or airframe manufacturer's maintenance manual and operational procedures is essential.
Stability
4.7.4.1 Attention shall be paid to aircraft stability Stability may be affected by aircraft type, mass, centre of gravity location, weather condition, runway roughness, and slope Stability shall be demonstrated by tests in accordance with the airframe manufacturer documentation.
4.7.4.2 The testing shall be conducted under maximum speed capability of the vehicle.
4.7.4.3 If a lateral instability is detected, a margin of 5 km/h (3 mph) shall be maintained between the speed at the beginning of instability and the maximum towing speed.
4.7.4.4 With minimal static load on the nose landing gear sufficient to move the airplane, no pitch oscillation of the aircraft shall occur, such that it would extend the shock absorber beyond the allowable strut extension in the ground mode.
4.7.4.5 Proper operational procedures shall be defined and followed to ensure vehicle and airplane stability.
Nose gear steering angle limit
The maximum steering angle for conventional tow bar towing, as specified in the airframe manufacturer’s documentation, is applicable for nose gear towbarless towing, unless otherwise noted.
Vehicle classification
The TLTV model will be categorized based on its intended application and will undergo testing accordingly It can be classified into three categories: a) category I for pushback only, b) category II for maintenance towing only, and c) category III for both pushback and maintenance towing.
Placarding
All limitations and warnings related to towing conditions must be clearly displayed in a location easily visible to the tow vehicle driver This includes the classification category as defined in section 4.9, the types of aircraft the TLTV is qualified to tow (if applicable), the maximum allowable speed, and the maximum allowable towing angle, among other important details.
General
5.1.1 No testing with an aircraft shall be performed if any requirement in Clause 4 is not met.
5.1.2 In case of a vehicle for which only partial qualification is required (e.g pushback only), the tests performed shall be appropriate to its category classification per 4.7.
5.1.3 Dynamic numeric simulation may be used instead of the specified tests, unless prohibited by airframe manufacturer’s documentation, and providing it guarantees at least equivalent results reliability.
Testing objectives
The primary objectives include measuring the maximum loads on the airframe during extreme conditions, such as maximum acceleration and braking, and ensuring that potential oversteer remains within the manufacturer’s specified limits Additionally, it is crucial to demonstrate the TLTV's ability to recognize steering angle or torsional load limits and alert the operator, although no actual aircraft testing will be conducted for oversteer indication or protection calibration due to damage risks Furthermore, the stability of the tow vehicle and aircraft combination must be verified across the full range of operational speeds, and the fatigue loads on the airframe from normal vehicle use during the intended operational category should be evaluated.
Aircraft configuration
5.3.1 Before any calibration or testing is accomplished, all landing gear shall be properly serviced as defined by the airframe manufacturer’s instructions.
Aircraft weights, including light and heavy gross weight, as well as the center of gravity (C.G.) position for testing, must comply with the calibration and test requirements outlined in sections 5.4 and 5.5, along with the specifications provided by the airframe manufacturer.
The airframe manufacturer (see Bibliography) should be consulted for any deviation from documented weights.
5.3.3 The aircraft shall be in the correct towing configuration as defined by the airframe manufacturer’s maintenance and operational documentation.
Calibration
General
5.4.1.1 Tests may be performed with an instrumented aircraft or an instrumented towing vehicle Calibration of both are discussed in this clause (see 5.5.1 for restrictions in the use of instrumented vehicles).
5.4.1.2 To measure fore and aft tow loads on the nose landing gear, strain gauges shall be installed at the nose gear locations (drag brace, torque arm, or other components) specified by the airframe manufacturer.
Calibration of the strain gauges is accomplished by pushing and pulling the nose gear with known tow loads.
5.4.1.3 To measure fore/aft and torsional tow loads on the TLTV, strain gauges shall be installed at vehicle locations specified by the vehicle manufacturer and shall be calibrated to a known tow load input.
5.4.1.4 Once the strain gauges have been calibrated, the aircraft can be towed with the TLTV and the tow loads can be determined directly from the strain measurements.
The following procedure outlines how to calibrate the strain gauges.
Aircraft calibration
5.4.2.1 The calibration test shall be performed with known tow/torsional loads Using an X-Y plotter, the microstrain (X-axis) is plotted against the known tow load input (Y-axis) (see examples in Figure 1 and Figure 2) The slope of the line is the calibration factor.
5.4.2.2 Instrumentation requirements for calibration are as follows: a) nose gear measured output in microstrain; b) calibrated input tow load (kN); c) both the strain gauges and strain gauge circuits shall be temperature compensating Other compensating requirements such as bending of the drag brace/torque link may be specified by the aircraft manufacturer Selection of strain gauges, bonding material, gauge protection, etc., should take into account the type of material being gauged and any possible adverse conditions that could occur during testing.
5.4.2.3 Calibration a) Calibration tests may be accomplished at the “light” and “heavy” reference test weights for the particular aircraft model being tested, to be specified by the airframe manufacturer However, if calibration is to be done at only one weight, the “heavy” test weight (HGW) shall be used in order to be conservative. b) Calibration shall be performed with the aircraft and wheels placed on a level and smooth surface. c) Immediately prior to calibration testing, the nose gear strut extension shall be recorded. d) All calibration tests shall be performed with all main gear tires chocked and aircraft parking brake set. e) Using the known tow load input, the aircraft shall be pushed and pulled while plotting microstrain versus tow load Two push/pull tests shall be performed at 0° nose gear steering angle. f) For 0° nose gear steering angle, the calibration load shall be from 10 % to approximately 50 % but not to exceed 75 % of the aircraft limit tow load as specified by the airframe manufacturer If main gear tire slipping or skidding occurs, the calibration is not valid and shall be repeated. g) The calibration plots shall be linear If the two calibration plots at 0° steering angle differ by more than 5 %, appropriate action should be taken to improve measurement repeatability If any nonlinearities exist in the calibration plots, appropriate adjustments to the test instruments should be made. h) If the criteria through 5.4.2.3 g) above are satisfied, the relevant calibration factor may be used to convert strain gauge measurements directly to tow load during towbarless vehicle testing.
13 calibrated test towbar transducer a Y input. b X input.
Figure 2 — Example of calibration test results (load history example and velocity history example)
TLTV calibration
5.4.3.1 The calibration test shall be performed with a known tow/torsional load.
Using an X-Y plotter, the microstrain (X-axis) is plotted against the known tow load input (Y-axis) (see Figure 2) The slope of this line is the calibration factor.
5.4.3.2 Instrumentation requirements for calibration: the instrumentation requirements are to be specified by the vehicle manufacturer and shall be in accordance with current state of the art techniques.
5.4.3.3 Calibration a) The calibration procedure shall be specified in writing by the tow vehicle manufacturer. b) The calibration loads shall include loads from 10 % to 50 % of the aircraft limit load for which the aircraft qualification is requested, as specified by the airframe manufacturer. c) Influence of vertical and side loads, as defined by the airframe manufacturer’s documentation, shall be considered during calibration. d) The calibration plots shall be linear If the two calibration plots differ by more than 5 %, appropriate action should be taken to improve measurements repeatability If any nonlinearities exist in the calibration plots, appropriate adjustments to the test instruments should be made. e) If the criteria through 5.4.3.3 d) are satisfied, the relevant calibration factor may be used to convert strain gauge measurements directly to tow load during towbarless vehicle testing.
Oversteering calibration
Calibration of TLTV oversteer detection systems, whether for angular or torsional load, must be conducted in an appropriate test facility by the vehicle manufacturer It is crucial to avoid calibration on in-service aircraft due to the potential risk of damaging the nose landing gears or the aircraft structure The maximum allowable limits for calibration are specified in the documentation provided by the airframe manufacturer.
Testing procedures
General
5.5.1.1 Prior to the tests a) A check shall be performed on the clearances between any part of the aircraft and tow vehicle structural parts as described in 4.5.2 and provided in the test report. b) Instrumentation should be in a serviceable condition and all items should have a valid calibration certificate.
5.5.1.2 Tests may be performed with an instrumented aircraft and/or an instrumented towing vehicle.
Towing load measurements on the vehicle are restricted to cases where accurate tow load measurements are possible (example: where pick-up device geometry allows accurate measurements).
5.5.1.3 Once calibration of the nose gear or tow vehicle strain gauges is accomplished, towbarless towing tests can be performed and tow loads can be measured directly.
For any change in weight or C.G of the aircraft, the instrumentation should be “zeroed” just prior to testing.
5.5.1.4 During testing, the steering angle should not exceed steering angle limits specified by the airframe manufacturer.
5.5.1.5 All tests shall be performed on typical airport taxiways.
Data recording
5.5.2.1 During testing, the following data shall be recorded on a time-history chart (see example Figure 2): a) calibrated nose gear drag loads in units of force (kN) (Y-axis of chart); b) towing speed (km/h) (Y-axis of chart); c) time (seconds) (X-axis of chart).
5.5.2.2 Data should be recorded analogically or at a minimum sampling rate of 30 samples/second
5.5.2.3 The following data should be recorded prior to commencement of the tests: a) aircraft gross weight; b) aircraft Center of Gravity location; c) strut extension for all landing gear, for each gross weight tested (not applicable to in-service fatigue evaluation trials); d) runway surface conditions during testing [e.g dry runway, 24 °C (75 °F), etc.] (not applicable to in- service fatigue evaluation trials); e) aircraft model and registration or serial number.
Evaluation criteria
6.1.1 Tests shall be performed in order to evaluate the following conditions: a) normal condition testing; b) stability testing; c) extreme condition testing.
To reduce testing costs, complexity, and duration while ensuring comprehensive data collection, the testing program must align with the vehicle classification It is advisable to utilize test rigs that simulate the aircraft interface, particularly for static testing, and to employ these devices when necessary to prevent potential damage to the aircraft, such as during oversteering tests Additionally, trials should ideally be conducted during in-service aircraft handling operations.
Normal condition testing
Testing methods
Normal condition tests must be conducted based on the intended use and classification of the tow vehicle, whether for maintenance towing or pushback only These tests can be carried out through in-service trials or dedicated trials specifically designed for evaluation purposes.
Tests number
The number of tests should be specified by the airframe manufacturer If no specific number of tests is required, the numbers specified in 6.2.3, 6.2.4 and 6.2.5 shall apply.
Pushback
A total of 45 pushback trials will be conducted using three different tow vehicle drivers, with each driver performing 15 trials The pushback maneuvers will involve an aft tow with a turn, followed by a short push or tow to align the nose gear parallel to the taxiway Each pushback will be executed under operational flight departure conditions or in a way that simulates typical in-service conditions, including speed, starts, stops, turns, and distance, as determined by the drivers The tests will be carried out with the aircraft engines turned off, and data on aircraft gross weights, the number of drivers, and engine status will be meticulously recorded.
Maintenance towing
A total of 45 maintenance towing trials will be conducted by three different drivers, with each driver completing 15 trials Each trial consists of an individual start-stop cycle, performed under either operational maintenance towing conditions or simulated typical maintenance conditions, including standard speed, turns, and distance The towing vehicle will aim to reach and stabilize at approximately 80% of its maximum loaded speed between stops Trials will be executed using either the operational maintenance towing weights or the reference weights specified by the airframe manufacturer, with the qualification of the tractor limited to the highest weight tested.
Pick-up and release
Fifteen pick-up and release operations will be conducted using the same weights as those for pushback or maintenance towing, based on the intended use and classification of the tow vehicle If the operation is not fully automated, three different drivers will carry out the test Additionally, if an in-service trial is conducted, this phase may be integrated into the pushback and/or maintenance towing tests.
Test evaluation
The number of tests shall be specified by the airframe manufacturer If no specific of tests are required, the numbers as specified in 6.2.3, 6.2.4 and 6.2.5 shall apply.
The airframe manufacturer will define the test weight If the specified test weight is unattainable, tests may be conducted at a reduced weight The tow forces for evaluation will be calculated accordingly.
Ffinal is the force value for test evaluation;
Ftest is the actual measured force value;
STGW is the specified test gross weight;
ATGW is the actual test gross weight;
OWE is the operating weight empty.
Stability testing
6.3.1 These tests are to ensure TLTV-aircraft stability over the velocity range capability of the vehicle during typical runway conditions and towing operations.
6.3.2 The tests shall be performed under aircraft reference test weight and the maximum speed attainable by the aircraft and tow vehicle assembly.
6.3.3 Two trials under these conditions shall be performed, and their results recorded For each test, the required speed shall be attained and maintained for a minimum of 20 s.
6.3.4 For the range of speeds thus tested, the TLTV should not induce oscillation or vibration loads on the nose gear.
The tow vehicle must exhibit stability throughout its entire operational range, including during starts, stops, and turns For safety, turns may be executed at speeds lower than the specified test speed If data or the driver indicates any instabilities or oscillatory loads, the maximum speed of the tow vehicle should be restricted to at least 5 km/h (3 mph) below the speed at which the instability was observed.
Extreme condition testing
Testing methods
Extreme condition tests must be conducted based on the intended use and classification of the tow vehicle, whether for maintenance or solely for pushback These tests should encompass both static testing and the measurement and assessment of loads during maximum acceleration and braking of the towbarless tow vehicle.
Static load tests
Four static load tests will be conducted, including: a) applying full aircraft brakes while the aircraft/tow vehicle is stationary on the taxiway; b) maintaining the brakes and quickly applying full vehicle power for 5 seconds, repeating this for two push and two pull tests, totaling four trials; c) conducting the tests at any aircraft weight under dry conditions to avoid abnormal sliding or wheel spinning.
If the subject TLTV and overload limiter devices have never been tested before, it is highly recommended to perform these tests with a simulated aircraft interface test rig.
Maximum acceleration and braking
Maximum acceleration and braking tests must be conducted by first accelerating the tow vehicle from a complete stop to the desired velocity using maximum power Once the target speed is achieved, it should be maintained until both the tow vehicle and aircraft stabilize, after which maximum braking should be applied until the aircraft comes to a full stop Additionally, push tests should be performed similarly to pull tests, with the aircraft being pushed aft instead of pulled forward, while following the same acceleration and braking procedures These tests are crucial for evaluating the vehicle's full capabilities, requiring drivers to brake and accelerate as forcefully as possible The sequence and details of the acceleration and braking trials are summarized in Table 1.
Table 1 — Acceleration/braking trials and sequence
Direction Pull tests Push tests
Oversteer testing
Testing of the TLTV oversteer indication and protection system must not be conducted on in-service aircraft to avoid potential damage to the nose landing structure or steering system Instead, testing should utilize an appropriate ground testing device that accurately represents the specific aircraft model for which the TLTV is designed However, if the TLTV oversteer limits are significantly lower than the maximum limits set by the airframe manufacturer, it is permissible to perform confirmation or confidence checks of these lower limits on an in-service aircraft.
General
This clause outlines the specific requirements and procedures for the inspection, maintenance, and calibration of towbarless tow vehicles (TLTV), focusing on their tractive force and steering protection systems or alerting devices, as necessary to safeguard the aircraft.
The TLTV aircraft's nose landing gear (NLG) tractive force and steering protection systems must be thoroughly inspected, maintained, tested, and calibrated according to the manufacturer's specifications This is essential to prevent potential damage to the NLG and steering system in the event of a failure or malfunction, ensuring compliance across all designated aircraft types that the TLTV is designed to support.
7.1.3 Inspection, maintenance and calibration schedules, any special tools and training requirements for the TLTV’s protection systems or alerting devices shall be available.
The aircraft NLG protection systems and alerting devices of the TLTV must be inspected, maintained, and calibrated according to the guidelines outlined in this document, as well as the maintenance manuals and schedules provided by the TLTV manufacturer.
The organization tasked with maintaining the TLTV must maintain documented records of inspections, maintenance, and calibration of each TLTV's aircraft NLG protection systems or alerting devices These records should be organized in maintained files and made available for review and audit by aircraft airworthiness regulatory authorities upon request.
7.1.6 Records should be kept for a minimum period of two years or in accordance with the requirements of the controlling aircraft airworthiness regulatory authority.
Maintenance manual
The maintenance manual for the TLTV manufacturer must include a dedicated section for the inspection, maintenance, and calibration of the aircraft's NLG steering and tractive force protection systems or alerting devices.
— detail the scope of the aircraft NLG steering and tractive force protection systems or alerting devices,
— list applicable equipment required to perform the inspection, calibration and maintenance tasks,
— list inspection, maintenance and calibration intervals,
— list all items to be checked/calibrated, and
— detail against each task full instructions on how the task/calibration should be carried out.
Requirements
7.3.1 The TLTV manufacturer shall publish inspection, calibration and maintenance checklists for each model of TLTV.
Each checklist must comprehensively outline its scope, include relevant reference documents, and specify the necessary equipment for inspection, calibration, and maintenance tasks It should detail the intervals for inspection, maintenance, and calibration based on hours run or calendar time, and enumerate all items to be checked or calibrated on the TLTV aircraft NLG steering and tractive force protection systems or alerting devices Additionally, the checklist must allow for the recording of the TLTV serial/chassis/fleet number and a task reference number, as well as document any defects and required actions Each checkable item must be signed off and dated by a qualified and authorized individual upon completion, and the finalized checklist should be signed off by the same individual and countersigned and dated by another authorized person once all tasks and actions are completed.
Calibration
Inspection, maintenance, and calibration of the TLTV aircraft's NLG steering and tractive force protection systems, as well as alerting devices, must be performed strictly following the manufacturer's checklist and maintenance instructions outlined in the maintenance manual.
The TLTV's aircraft NLG steering and tractive force protection systems must be calibrated according to the service intervals outlined in the manufacturer's maintenance manual These intervals may be extended if the aircraft is equipped with two parallel and independent systems that feature a permanent built-in cross-check, triggering an alarm in case of any discrepancies.
Calibration must be performed following the TLTV manufacturer's inspection, maintenance, and calibration checklist, utilizing the tools and equipment specified in the manufacturer's maintenance manual or appropriate alternatives.
7.4.4 Any tools used in the inspection maintenance and calibration tasks shall themselves be calibrated against known standards where applicable.
7.4.5 The qualified and authorized person performing the inspection, maintenance and calibration tasks shall sign off and date each task as it is completed on the maintenance checklist.
The checklist must be signed by the qualified individual conducting the inspection, maintenance, and calibration tasks, and it should be countersigned and dated by an authorized person once all tasks and actions have been finalized.
Special tools
7.5.1 The TLTV manufacturer shall list in his maintenance manuals and checklists any special tools that are required to perform the inspection, maintenance and calibration requirements.
7.5.2 Where appropriate, instructions regarding the calibration of the special tools shall be provided The re-calibration of any special tools shall be performed and recorded at specified intervals.
Training
Personnel responsible for the maintenance of the TLTV must receive proper training in the inspection, maintenance, and calibration of both the TLTV and the aircraft's nose landing gear (NLG) steering and tractive force protection systems or alerting devices.
7.6.2 The TLTV manufacturer shall be able to provide appropriate and formal training.
Maintenance records
Records of all inspections, maintenance, and calibration checks for the TLTV aircraft's NLG steering and tractive force protection systems, as well as alerting devices, must be maintained for at least two years Additionally, it is essential to keep other pertinent maintenance and inspection records.
7.7.2 Each task shall be signed off and dated when completed by the qualified and authorized person carrying out the task.
7.7.3 The completed and signed off maintenance record shall be counter-signed and dated by an authorized person.
7.7.4 The records shall be maintained in a manner that enables them to easily be presented for review and audit by the appropriate aircraft airworthiness regulatory authority when requested.
The TLTV's aircraft nose landing gear (NLG) tractive force and oversteering protection systems must be designed, inspected, maintained, tested, and calibrated according to the manufacturer's standards This ensures their effectiveness throughout the service life of the TLTV, safeguarding against potential damage to the aircraft's NLG or steering system in the event of a failure or malfunction.
Manufacturers must maintain comprehensive records of the TLTV model's design calculations and tests, known as the design file, which should be signed by qualified personnel Additionally, owners/operators are required to keep detailed maintenance files for each unit, documenting maintenance activities, periodic inspections, calibrations, and any modifications made.
The TLTV manufacturer must include in the maintenance manual a dedicated section detailing the inspection, maintenance, and calibration requirements for the aircraft's NLG tractive force and oversteering protection systems Additionally, the manual should provide checklists for these tasks, which must be signed and overseen by qualified maintenance personnel and documented in the unit's records It is also essential to identify any special tools needed, along with instructions for their calibration when necessary Furthermore, the training content required for maintenance staff responsible for these tasks and their supervision should be clearly outlined.
In the case of modifications to a TLTV, it is the responsibility of the TLTV manufacturer, owner/operator, or affected aircraft operator to assess whether these changes impact the loads on the aircraft, referencing the original design file If the modifications could potentially exceed the maximum limits outlined in section 4.1, a re-test must be conducted in accordance with Clause 5.
To ensure accountability and traceability in the design, testing, and monitoring of the TLTV model's aircraft protection functions, it is essential to implement a quality control program from the TLTV manufacturer that complies with ISO 9001 or a relevant industry standard.
The above recommendation is a regulatory requirement for aircraft registered or operated under EASA CS-25 Regulation CS-25.745(d), in accordance with Acceptable Means of Compliance AMC 25.745(d).
9.1 It shall remain possible throughout the operating life of any TLTV model
— to trace back the source data for any aircraft NLG steering system and tractive force protection or alerting devices calibration values published in the manufacturer’s maintenance manual,
— to update these in the event of a modification of source data, or if (an) additional aircraft type(s) is (are) to be designated for handling by the TLTV,
To enhance the aircraft's NLG steering system and tractive force protection against undetected damage, it is essential to analyze reported in-service incidents This analysis will help determine if modifications are necessary for the TLTV or the inspection, maintenance, and calibration procedures of the aircraft's NLG steering system and tractive force protection or alerting devices.
All TLTV operators will receive service bulletins, modifications to the TLTV, or updates to maintenance manuals, inspection, maintenance, and calibration procedures when warranted by relevant occurrences.
9.2 The responsibility for the traceability and monitoring functions defined in 9.1 should normally rest with the TLTV manufacturer.
When a TLTV is resold, the seller must provide the buyer with the relevant maintenance manuals and records, and inform the TLTV manufacturer about the sale Additionally, the buyer is responsible for registering with the TLTV manufacturer to receive important service bulletins, modifications, and updates to the maintenance manuals.
In the event that the TLTV manufacturer goes out of business, it is essential to transfer responsibility and all relevant documentation to the company that assumes control of the engineering, after-sales, or marketing functions for the TLTV product line.
If a company fails to assume the responsibilities specified in section 9.2 under the conditions described in section 9.4, the operators of the TLTV model(s) will be required to take action.
9.5.1 Designate an appointed holder of the functions defined in 9.1.
9.5.2 Ensure that the relevant files are duly transferred to the appointed holder designated at 8.5.1.
9.5.3 Inform of the foregoing all operators of aircraft handled by the concerned TLTV(s), who will in turn keep the controlling airworthiness regulatory authority informed as required.
10.1 All loads and their effects upon the aircraft shall remain within the requirements listed in this document or the applicable airframe manufacturer’s test documentation.
Any modification to the TLTV that notably impacts the loads on the aircraft must be assessed to establish whether the test program is entirely or partially invalidated, necessitating retesting.
The TLTV manufacturer or aircraft operator must assess if the modification impacts the loads on the aircraft and decide if partial or complete retesting of the modified TLTV is necessary.
Operating instructions shall be provided by the TLTV manufacturer, including but not necessarily limited to the following:
— classification/intended conditions of use;
— allowable aircraft types or sub-types (per TLTV setting if applicable);
— instructions for use, including nose landing gear pick-up and release sequences;
[1] ISO 9000, Quality management systems — Fundamentals and vocabulary
[2] ISO 9001, Quality management systems — Requirements
[3] SAE Aerospace Recommended Practice ARP 4853C, Specification for towbarless tow vehicles 3)
[4] SAE Aerospace Recommended Practice ARP 5283A, Nose gear towbarless tow vehicle basic test requirements 3)
[5] SAE Aerospace Recommended Practice ARP 5284B, TLTV — Aircraft NLG steering and tractive force protection systems or alerting devices — Inspection, maintenance and calibration requirements 3)
[6] SAE Aerospace Recommended Practice ARP 5285, Towbarless towing vehicle operating procedure 3)
[7] IATA Airport Handling Manual AHM 957, Functional specification for aircraft nose gear controlled towbarless tractor 4)
[8] AIRBUS document AM2250, Towbarless Towing Vehicle – Assessment Criteria 5)
[9] BOEING document D6-56872, Towbarless towing vehicle assessment criteria 6)
[10] BOMBARDIER Technical Report TRD-BA500-480, “Towbarless vehicules Qualification process and requirements” (Rev:–, 2015-05-03) 7)
[11] EMBRAER Report N° 000-CA-059, Towbarless tow vehicles approval testing procedures 8)
[12] Facility and equipment planning manuals for each aircraft type 9)
3) SAE standards and recommended practices can be obtained from: Society of Automotive Engineers, 400, Commonwealth Drive, Warrendale PA 15096-0001, U.S.A.
4) AHM 957 is part of the Airport Handling Manual, which can be obtained from: International Air Transport Association, Publications Assistant, 800 Place Victoria, P.O.Box 113, Montréal, Québec H4Z 1M1, Canada.
5) Can be obtained from: AIRBUS airport.compatibility@airbus.com?subject=Request%20for%20AM2250%20 -%20Towbarless%20Towing%20Vehicle%20-%20Assessment%20Criteria.
6) Can be obtained from: BOEING Commercial Airplane Group Customer Service and Material Support (CSMS), P.O.Box 3707, Seattle WA 98124, U.S.A.
7) Can be obtained from: BOMBARDIER Mirabel site, 13100 Henri-Fabre, Mirabel, Québec, Canada J7N 3C6, Tel.:
8) Can be obtained from: EMBRAER, VPI / DTE / GAL / LCS, P.O Box 8050, Av Brigadeiro Faria Lima 2170, 12227
901 Sao José dos Campos SP, Brasil.
9) Can be obtained from the individual airframe manufacturers concerned.