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2.4 ULDs and Cargo Restraint Devices.
2.4.1 Restraints. Aircraft cargo restraint methods have two general categories: primary and supplemental.
2.4.1.1 Primary Restraint. Primary restraint is the restraint of the cargo payload to the aircraft structure through the CLS or directly to tiedown points approved in the WBM. This restraint secures cargo in the forward, aft, vertical, and lateral directions. Primary restraint is used to secure:
2.4.1.1.1 Cargo.
1. To a pallet using a WBM-authorized net as the primary restraint;
2. Within a container (the container is the primary restraint);
3. To the aircraft structure as special cargo (straps, ropes, etc., are the primary restraint); or
4. To the ULD (pallet) using straps or ropes, as the primary restraint is considered special cargo.
2.4.1.1.2 ULD. To the aircraft structure using the CLS, such as locks and side rails.
2.4.1.1.3 Other Aircraft Restraints Per WBM Provisions. Some airplane WBMs may provide for additional tiedown to the aircraft structure to restrain ULDs if the following conditions exist:
1. The ULD allowable weight may be limited either by restraint configurations or by missing and/or inoperative restraints; or
2. The ULD is loaded to a weight greater than allowable for the chosen loading position with all restraints operative, and a greater weight is allowed by the aircraft WBM with tiedown (e.g., the floor is more capable than the restraint system).
Note: See paragraph 2.8 for additional guidance.
2.4.1.2 Supplemental Restraint. Supplemental restraint is additional restraint that prevents shifting and is used to stabilize cargo to a pallet or container. When supplemental restraints are attached to a CLS or aircraft structure, it creates a parallel load path to the ULD and is therefore classified as special cargo (see paragraph 2.8 for additional guidance). An exception would be straps or ropes used to prevent shifts or stabilize cargo in a certified bulk compartment.
Operators may use supplemental straps at their discretion as long as the primary means of restraint has been complied with.
2.4.2 ULD Description. A ULD is a device for grouping, transferring, and restraining cargo for transit. It consists of a pallet with a net, or it may be a container. ULDs are defined in National Aerospace Standard (NAS) 3610, Cargo Unit Load Devices—Specification for;
2-12 Aerospace Standard (AS) 36100, Air Cargo Unit Load Devices—Performance Requirements and Test Parameters; and Technical Standard Order (TSO)-C90, Cargo Pallets, Nets and Containers (Unit Load Devices). The term “ULD” includes the equipment in paragraph 2.4.3 below.
Note: Cargo restrained on a pallet by straps is not a ULD.
2.4.3 Types of ULDs.
2.4.3.1 Background:
1. Authorized ULDs are defined in aircraft WBMs and require no further analysis.
2. Some ULD designs may exceed the structural capability of an aircraft. To preclude failures of the aircraft cargo restraint system, operators must meet the requirements of the aircraft WBM, as this is an operating limitation that is part of the AFM and must be complied with per §§ 91.9, 23.2620, and 25.1583.
2.4.3.2 Certified ULDs. A ULD meeting the requirements of TSO-C90; STC requirements, if applicable; or other FAA-approved certification standards. A certified ULD is structurally capable of restraining a load and/or protecting the aircraft systems and structure. Only ULDs that are authorized by the aircraft WBM (TC or STC) are authorized for use on that aircraft. To remain an authorized ULD for an aircraft, the ULD must be restrained by the aircraft’s CLS in accordance with the aircraft’s WBM, as an operating limitation contained in the AFM (per § 91.9). Examples of restraining ULDs by the aircraft’s CLS include pallet locks and side guides. A certified pallet and the corresponding certified net is a certified unit, as defined by the WBM.
2.4.3.3 Approved Cargo Pallet and Net (ULD). Most operator WBMs recognize a TSO cargo pallet and net combination as the primary restraint for unitized cargo. A cargo pallet net is the only restraint device that takes the shape of the cargo while restraining the load in all directions, so that the load is spread to the net fittings and pallet edge rails.
2.4.3.4 Noncertified ULDs. A ULD that does not meet the TSO-C90 or TC/STC certification requirements.
2.4.3.5 Active ULDs. Active ULDs include powered systems, such as temperature control and fire suppression systems. Active ULDs use batteries of multiple types to power these systems, and the manufacturers frequently integrate electrical wiring, fans, and components that should be able to withstand the handling, loading, and transport environments. Active ULDs are intended to be operating during flight. Active ULDs are battery-powered in flight and are only recharged while on the ground. Commonly used active ULDs are temperature-controlled containers. These systems consist of a highly insulated
2-13 container with a battery-operated heating/cooling system integrated into the construction of the container.
2.4.3.5.1 Active ULD Operational Approval and Use. Using active ULDs that interface with the pilot or aircraft avionics or electronic systems likely requires an STC If you intend to deploy these containers in your fleet, you should understand and assess the hazards of active ULDs before carrying such devices.
Additionally, you should incorporate or reference the pertinent parts of the aircraft certification documents into your manual and have procedures to ensure the containers meet the handling and airworthiness requirements of the manufacturer. These may include:
• Required markings, placards, and labeling;
• ICAs, to include proposed limitations and restrictions necessary to safely carry the device on an aircraft; and
• Operating instructions for the device.
2.4.4 Other Restraint Devices.
2.4.4.1 Other Types of Cargo Restraint Devices. The operator may use cargo restraints such as straps, ropes, chains, and nets. The use of these types of restraints must not be contrary to aircraft manufacturer W&B documentation or STC holder documentation (per §§ 23.2620, 25.1583, and 43.13(c)). If the operator does not use an approved cargo pallet/net combination as the primary restraint, the operator’s manual should have policies and procedures to address this issue. For example, if a strap is used as the primary restraint, the cargo may be:
1. Loaded in an aircraft compartment that meets the type design for compartment restraint; or
2. Restrained by cargo straps or other authorized devices to the aircraft as described in the aircraft’s manual, an STC supplement, or a WBM.
2.4.4.2 Certified Restraint Straps. In TSO-C172, Cargo Restraint Strap Assemblies, the FAA describes the minimum performance standards (MPS) by which cargo restraint strap assemblies are pproved and identified with applicable TSO markings. Newer straps may have expiration dates marked on the straps.
2.4.5 Determining ULD Compatibility. It is critical to safety of flight for the operator to have procedures confirming that ULDs on board an aircraft are compatible with the aircraft, regardless of who owns the ULD. Not all ULDs are authorized as compatible with all aircraft, so an operator should have procedures for:
2.4.5.1 Authorization. Ensure ULDs are authorized for carriage on the specific aircraft by the DAH WBM.
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2.4.5.2 Communication. Inform employees and vendors loading aircraft converted from passenger to all-cargo by an STC that the aircraft could have different ULD requirements than other STC conversions or production aircraft configurations in the operator’s fleet.
2.4.5.3 Differences. Ensure personnel understand that compatibility, limits, or restrictions may exist between similar aircraft types with STC conversions, and that the aircraft may have been produced as a freighter by a TC holder.
The following list details examples of the differences:
1. Aircraft weight limits;
2. Cargo zone index changes (forward/aft body);
3. CG limits;
4. Forward and aft body structure loading limits;
5. Fuel index tables;
6. Individual compartment maximum loads;
7. Lateral cargo unbalances;
8. Main deck door opening variances;
9. Maximum allowable loads limited by restraint;
10. Maximum allowable weight limits (takeoff, landing, zero fuel, etc);
11. Maximum area load limits;
12. Maximum cargo zone load limits, including cumulative loads above and below deck;
13. Maximum cumulative load limits;
14. Maximum floor loading limits;
15. Maximum ramp weight limits;
16. Maximum ULD gross weight restrictions by aircraft position;
17. Mi ssing inoperative cargo restraint limits;
18. Reduced overwing zone capabilities;
19. ULD height restrictions;
20. Asymmetrical load limits; and
21. Zero fuel weight restrictions.
2.4.5.4 ULD Contour and Dimensions. Compare the size of the main and lower deck compartment door openings with the contour and dimensions of ULDs to be loaded. An operator must take into consideration any height restriction
2-15 within the aircraft cargo compartments if it is an operating limitation in the WBM (per § 91.9).
2.4.5.5 Approved ULD Limitations. Ensure approved ULD limitations are maintained in the manual. An operator should base these limitations on data from applicable aircraft WBMs or STC supplemental WBMs. The limitations should identify which ULDs are compatible with specific aircraft, and should be easily accessible by all responsible persons.
Note: The limitations section of the AFM or AFM supplement may include information from the aircraft WBM.
2.4.5.6 Authorized ULDs. Ensure the aircraft operator’s WBM states which ULDs may be carried aboard the aircraft on the main deck or lower lobes. In certain instances, particularly with an aircraft’s lower lobes, certain compartments ay be approved to carry bulk or restrained cargo, or both. The WBM should identify the ULDs by the type authorized to be carried aboard the aircraft, considering the aircraft and CLS capabilities.
2.4.5.7 Use of Noncertified ULDs. Ensure the operator does not use noncertified ULDs in any compartment of an all-cargo or combination aircraft, unless:
1. The ULDs are authorized by the WBM, or
2. Tiedown instructions describe how to restrain the ULDs as special cargo.
2.4.5.8 Un authorized Pallet and Net Combinations. Ensure employees and vendors do not combine unapproved nets and pallets.
2.4.6 Responsibilities for Maintenance and Repair of ULDs, Pallets, and Nets If Operator Owned (per §§ 121.363 and 135.413). Operators should maintain ULDs, pallets, and nets using a program based on component maintenance manual (CMM) requirements for TSO’d items. The operator should have a program to determine the serviceability of ULDs before they may be placed on board the aircraft. If an operator repairs these items, it should (1) do so per the CMM of the item, and (2) approve the item for return to service per its procedures authorized by its operations specifications (OpSpecs).
2.4.7 Responsibilities of an Operator for ULDs.
2.4.7.1 Receiving a ULD. When receiving a ULD, an operator who owns or leases its ULDs should have trained, qualified, and authorized personnel perform a serviceability check of the ULD using the operator’s procedures. The serviceability check should include processes, instructions, and guidelines to:
1. Check each ULD before it is put into service;
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2. Review the documentation for new and repaired ULDs, or make the documentation for new and repaired ULDs available upon request, to ensure the ULD is serviceable; and
3. Conduct a visual inspection of the ULD.
Note: The operator may designate a trained, authorized, and qualified person to conduct the checks.
2.4.7.2 Maintaining ULD Repair Records. Certified ULDs should be maintained to the TSO. Noncertified ULDs should be maintained to standard practices or the ULD manufacturer’s directions. The operator should ensure that a repair facility retains the records of those repairs. If an operator maintains its own ULDs, repair records retention should be in accordance with its accepted procedures authorized by OpSpecs issuance. An operator who maintains its own ULDs may maintain its own records or have repair vendors maintain the records, provided the operator can access them upon request within a reasonable period of time.
2.4.7.3 Procedures for Maintaining and Repairing ULDs. An operator that maintains its own certified and noncertified ULDs should have procedures in place to maintain those ULDs in accordance with CMMs and manufacturers’ instructions. If the operator marks its owned certified and noncertified ULD as complying with a TSO, then the operator should ensure that the ULD is maintained per the latest version of that TSO. The procedures should be the same for both certified and noncertified ULDs. The procedures should:
1. Clearly state the data supporting the maintenance and repair; and
2. Address how frequently the operator, ow ner, or repair vendor should check ULD tare weights and how updated ULD tare weights should be marked. The operator or owner should manage control of ULD tare weights by documenting them and retaining the documentation using operator or owner procedures.
2.4.7.4 Guidance for Repairing ULDs. An operator or owner should have procedures to ensure that:
1. Personnel who repair ULDs are trained, qualified, and authorized;
2. ULDs are repaired per the operator’s or owner’s maintenance program for ULDs;
3. The appropriate current data is available to repair the ULD, including operator or owner maintenance manuals, noncertified ULD manufacturer maintenance manuals, SBs, ADs, or certified ULD manufacturer CMMs;
4. The tare weight of each ULD is checked using the operator’s procedures;
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5. The new tare weight is marked on each ULD using the operator’s or owner’s procedures; and
6. ULD repair is per the operator’s, owner’s, or standard practices procedures, whether the operator or a repair vendor performs the repairs.
2.4.7.5 Use of a Repair Station/Vendor to Repair ULDs.
1. An operator or owner should ensure the availability of all necessary data and manuals for repairing its ULDs.
2. An operator or owner should conduct audits of contracted repair stations:
• For the vendor’s training program; and
• To ensure repair stations meet the operator’s or owner’s maintenance program requirements.
2.4.7.6 Returning a ULD to Service. An operator that owns ULDs should have procedures for repairing unserviceable ULDs and returning them to service.
As provided in §§ 121.363(b) and 135.413(b)(2), an operator remains responsible for the airworthiness of its aircraft, which may be impacted by the use of owned or leased ULDs, whether they are maintained in-house or by contract. Maintenance personnel should be appropriately trained and should return ULD equipment to service consistent with the applicable CMM or operator instructions. FAA-certificated repair stations operating under 14 CFR part 145 should return ULDs to service using the operator’s procedures.
2.4.7.6.1 Owners of certified and noncertified ULDs should have procedures established with repair entities that ensure repairs are conducted using the CMM or manufacturer’s procedures that ensure the ULD is returned to a serviceable condition.
2.4.7.6.2 An operator should use FAA-acceptable data if it decides not to follow the requirements of the manufacturer’s CMM. An operator may also choose to strictly follow the manufacturer’s maintenance procedures.
2.4.7.6.3 An operator should use its SMS to verify the performance and effectiveness of its ULD maintenance program, if applicable, and provide corrections to any deficiencies discovered in the program.
2.4.8 ULD and Restraint Damage Limits.
2.4.8.1 Identifying or Revising Damage Limits. It is important that the operator specify damage limits for ULDs and related restraint equipment.
2.4.8.2 Standardization of Damage Limits for ULDs. An operator may standardize damage limits for ULDs transported upon its aircraft. The operator should
2-18 apply the most restrictive damage limits categorized by the type of ULD, unless it has engineering data to support less restrictive damage limits.
2.4.8.3 Exceeding Allowable Damage Limits of a ULD. A ULD that exceeds allowable damage limits to the ULD base needs careful evaluation to determine if it is usable. A ULD with damage to its shell may be accepted for use by installing an authorized net over the shell, provided a pallet/net combination is authorized. A reduced-weight requirement may be necessary when an operator uses this procedure. The operator should develop procedures for using the damaged ULD with a net.
2.4.9 Establishing Usage Limits for Cargo Straps. Operators should ensure cargo strap assemblies are serviceable prior to use. If a cargo strap manufacturer does not provide damage limitations for its cargo straps, an operator should develop guidance to include, at a minimum, not using the strap if:
2.4.9.1 Buckle Latch Mechanism. A buckle latch mechanism will not lock or stay engaged. This allows the web to slip while under tension, or may result in the web binding or being out of alignment.
2.4.9.2 Mechanism Integrity. Attached mechanisms, fittings, hooks, or rings are bent, deformed, cracked, broken, or missing.
2.4.9.3 Webbing Integrity. Webbing is partially cut or torn, knotted, unraveling, or has loose or missing sewn stitches.
2.4.9.4 Environmental Conditions. The strap is deteriorated due to environmental conditions.
Note: TSO-C172 is available and provides a set of approved performance standards for manufacturing new cargo restraint straps.
Cargo restraint strap assemblies authorized under previous Technical Standard Order Authorization (TSOA) may still be manufactured under the provisions of its original approval.
2.4.10 Additional Procedures for Cargo Nets. If the operator owns or leases cargo nets, it should consider using additional procedures for cargo nets, such as:
1. Assigning a unique marking or serial number to nets and placarding that marking or number on the nets;
2. Placarding nets with their damage limits;
3. Attaching an identification tag to the operator’s nets; or
4. Ensuring proper storage when not in use to prevent damage.
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2.4.11 Temporary Repair on a Cargo Net.
2.4.11.1 Using Temporary Restraints. An operator must repair a cargo using temporary restraints in accordance with the AFM/WBM, and should have provisions for:
1. The net CMM authoring use;
2. A process in its manual system addressing the use and limits of temporary restraints; and
3. Personnel who install the temporary restraints are trained, qualified, and authorized.
2.4.11.2 Purpose. Temporary restraints are typically installed for the purpose of addressing items such as:
1. Using a bridge strap to bridge cut (or otherwise damaged) ropes, or missing or damaged fittings;
2. Installing temporary fittings and hooks to compensate for damaged or missing fittings, using equipment manufacturer or operator procedures; or
3. Installing net corner and supplemental lashing lines.
2.4.12 Performing Serviceability Checks on ULDs or Other Cargo Restraint Devices. An operator should perform a serviceability check for damage before using ULDs and other restraint devices (e.g., single and double stud rings, straps, and pallet couplers) for movement or buildup, and should conduct a final serviceability check before loading cargo aboard the aircraft.
2.4.12.1 Purpose. Serviceability checks are not intended to determine a ULD’s airworthiness. Instead, they ensure the ULD or other restraint devices do not have obvious damage greater than their damage limits. An operator should not use ULDs or other restraint devices with damage greater than damage limits specified.
2.4.12.2 Individuals Who May Perform Serviceability Checks. Personnel who perform serviceability checks do not have to be FAA-certificated mechanics or repairmen. Operators should train, qualify, and authorize personnel to perform serviceability checks. Operator procedures should identify who performs these checks and when the checks are performed.
2.4.12.3 ULDs That Fail a Serviceability Check. An operator should have a procedure for clearly marking or identifying ULDs and other restraint devices that fail serviceability checks. The method for identifying failed equipment should clearly distinguish these items from serviceable equipment so the operator or cargo loading vendor does not inadvertently place failed equipment into service. A procedure should be in place for individuals to
2-20 report damage to persons responsible for maintaining the ULD. If transporting unserviceable ULDs to a place where repairs are available, the operator should determine the method of transportation in accordance with the AFM/WBM.
Note: The operator may correct clerical, data entry, or other error of omission resulting in misidentifying or removing a ULD from service, and have the ULD returned to service. The operator should have a procedure in its manual system for identifying and correcting such errors.
2.5 Cargo Weigh Scales.
2.5.1 Ensuring the Weight of Loaded Cargo is Accurate. An operator must ensure the weight of cargo loaded aboard its aircraft is accurately described in the load manifest (per §§ 121.693 and 135.443). The operator’s W&B program should account for allowed tolerances to maintain approved W&B limitations.
2.5.2 Ensuring Weigh Scales Are Accurate. An operator should have a program to periodically check the accuracy of scales used for weighing cargo. The operator should conduct a periodic functional check using the weight recommended by the scale manufacturer for a periodic functional check. As an alternative, use weights simulating a typical load placed on the operator’s aircraft. Periodic function and calibration checks should be performed in accordance with the operator’s procedures and timeframes. Frequent checks and periodic calibrations ensure an operator accurately weighs the cargo loaded on its aircraft.
2.5.3 Ensuring Weigh Scales Are Calibrated. An operator should conduct periodic calibration of scales to ensure they are appropriately serviced and accurate to a known standard using an interval recommended by the scale manufacturer. Calibration records should show that scales are calibrated using a standard established by appropriate country, state, or local government regulations. Such standards could include the National Institute of Standards and Technology (NIST), an equivalent standard acceptable to the FAA, or standards recommended by the scale manufacturer.
Note: For more information on the standards provided by NIST, visit NIST’s website at https://www.nist.gov/.
2.5.4 Maintaining Records of Calibration Checks. An operator should keep a record of its scale calibrations, with the following criteria:
1. The records should be in the English language. If the records are not in the English language, operators should have the records translated, when necessary. If the operator cannot provide an English language interpretation of operator records, that operator should allow those individuals using the scales to inspect the scales and perform a functional check onsite to ensure scale accuracy.
2. The operator should establish procedures to maintain the records.
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2.5.5 Performing Functional Checks on Scales Used for Weighing Cargo.
2.5.5.1 Procedures. An operator should have procedures to functionally check scales used for weighing cargo between scale calibrations. A functional check should consist of field-testing the scale’s accuracy within the tolerance of the scale manufacturer, or within a tolerance of ±1 percent, whichever is more restrictive, using an item of known weight.
2.5.5.2 Frequency. At a minimum, the operator should ensure that functional checks are performed at intervals specified in (1) the operator’s procedures, or (2) the scale manufacturer’s recommendations. The operator also should conduct the functional checks at intervals commensurate with the frequency of scale use, and conduct functional checks more often for scales used more frequently.
2.5.5.3 Recordkeeping. An operator should record completion of functional checks.
The operator should maintain functional check records using accepted procedures. These records should include:
1. The identification number of the scale;
2. The date and time of the functional check;
3. The name or the initials of the person who performed the functional check;
4. The applied known weight of the item used for the functional check;
5. Instructions to ensure that the test load is completely free from all contaminants or any damage;
6. The scale’s indication of the applied known weight; and
7. The difference between the applied known weight and the registered weight.
Note: If the registered weight recorded for the item of an applied known weight is outside the tolerances specified for the scale in the operator’s procedures, the operator should not use the scale until the scale is inspected and calibrated. The operator should apply the scale variance to the total weight of the cargo being weighed.
2.5.6 Items for Which an Operator Should Know the Tare Weight. Personnel weighing cargo should know the weight of equipment such as dollies, slave frames, containers, and carts that are not being shipped on the aircraft but are only being used to facilitate loading of the aircraft. An operator should determine the tare weight of this equipment by weighing it on a calibrated scale.
2.5.7 Reweighing Loading Equipment for Tare Weight After Maintenance, Repair, or Modification. Immediately after any repair, maintenance, or modification of equipment such as dollies, slave frames, containers, and carts, the operator should provide a new tare
2-22 weight by reweighing the equipment. Operators should establish a method to communicate new tare weights to loading personnel before using the equipment to weigh cargo on a scale. This method may be in the form of the operator communicating the tare weight by stenciling it on the equipment or by providing notices to operator loading personnel.
2.6 Operations for Cargo Handling and Aircraft Loading and Unloading.
2.6.1 Overview. This section explains how to apply the content in paragraph 2.4 to an air carrier’s cargo operations.
2.6.1.1 Procedures. An operator should have procedures in its manual system for ULDs, cargo requiring unique or special handling, special cargo, cargo buildup, loading and unloading, and restraining cargo. The procedures should include bulk loading and unloading of cargo, whether the cargo is compartment-restrained or restrained by other devices, if the operator permits.
The procedures should use the operator’s WBM and DAH/STC WBM.
2.6.2 Operator Procedures on ULD Buildup and Cargo Restraint. An operator’s procedures covering ULD buildup and cargo restraint should address:
2.6.2.1 ULD CG Limits. Procedures should address maintaining the longitudinal, lateral, and vertical CG limits of a built-up ULD. The operator should consider the following guidelines when developing the procedures:
1. Place sturdier, heavier, and larger cargo pieces on the bottom of the load and evenly distribute them over the length and width of the pallet base.
2. Place smaller, lighter, and fragile cargo pieces on top and evenly distribute them from the center over the length and width of the ULD.
3. Level off the cargo in the ULD when less than full.
4. Interlock or overlap small pieces when practical.
2.6.2.2 Voided Space in ULDs. To minimize voided space within a ULD and between cargo pieces, the operator should consider using the following:
1. Supplemental restraint devices to restrain cargo within a container when less than full.
2. Dunnage in voided spaces. See Appendix C, Definitions Related to Air Cargo Operations, paragraph C.12.
2.6.2.3 Cargo Contours. The operator should have procedures for contouring cargo loads for the aircraft’s interior dimensions when using a pallet/net combination, pallet/strap combination, or other restraint methods/devices.
The operator should consider using techniques such as contour templates or