Par 3.2.4 Page 57
3.2.4 Features of Cargo Restraint Systems.
3.2.4.1 Cargo Restraint System. The cargo restraint system installed in an aircraft is a critical design feature. The cargo restraint system is the primary means of ensuring the cargo loads introduced into the aircraft structure are properly distributed, and all items of mass are restrained from movement or from damaging critical aircraft systems when subjected to (1) flight, landing, and ground operational loads; and (2) loads resulting from emergency landing conditions.
3.2.4.2 Cargo Restraint System Inclusion. The cargo restraint system may include barriers, ULDs, nets, straps, chains, tiedowns, and floor locks. A cargo restraint system must have sufficient strength under the certification requirements to restrain the cargo safely and must ensure the cargo will not shift and block or reduce access to emergency exits, obstruct the flow of required fire retardants, and interfere with other design features, such as flight controls, that are critical to the safety of flight. The minimum requirements are defined in appropriate airworthiness standards.
3.2.4.3 Protection During Emergency Landings. An operator should determine whether (1) the cargo restraint system or (2) a barrier will protect all occupants from shifting cargo during emergency landings. This decision affects the aircraft’s structural requirements, ULDs, and cargo restraint system. Guidance and restraint system configurations are in the current editions of AC 25-5, Installation Approval on Transport Category Airplanes of Cargo Unit Load Devices Approved as Meeting the Criteria in NAS 3610; AC 25-18, Transport Category Aircrafts Modified for Cargo Service; and TSO-C90.
3.2.4.4 Appliances. The cargo restraint system and the devices used to restrain the cargo to the aircraft structure are appliances.
3.2.5 Ensuring the Integrity of a Cargo Restraint System. Even though the original design of a cargo restraint system may be in compliance with the applicable certification regulations, the installation of the system may not be adequately defined. Inspections of some aircrafts have revealed wrong part numbers of installed locks, missing locks, damaged equipment needing repair or replacement, and modifications made to the cargo restraint system that appeared to compromise its integrity. To maintain the integrity of the cargo restraint system, the operator should ensure that replacement parts are authorized for the cargo restraint system components on which they are installed. It is important also to note that the operating environment for cargo restraint systems is generally more severe than what most aircraft structures ensure. Many traditional marking methods are not permanent in this environment, and to enhance the integrity of its system, an operator should ensure that its cargo restraint system markings are permanent.
3.2.6 Fire Protection Design Features of Aircraft that are Essential to Operational Safety. While AC 25-18 discusses the various classes of cargo compartments and associated fire protection requirements, it is important to emphasize the dependence on the continued airworthiness of certain FAA-approved design features of cargo compartments essential to operational safety. For class A and B compartments, ensuring accessibility by a crewmember and availability of an authorized fire extinguisher are critical to safety in the event of hazardous quantities of smoke or fire. For the class C and E compartments, the functions of specific design features must be preserved to ensure operational safety. The integrity of the cargo compartment
Par 3.2.6 Page 58 liner must be maintained and the decompression features uncompromised because the liner often serves the dual purpose of fire and smoke containment while providing ventilation paths for decompression events. Smoke detectors for class C and E compartments and fire suppression equipment for Class C compartments are the essential equipment required for operational safety.
Therefore, it is imperative that care should be taken when loading bulk cargo in class B, C, and E cargo compartments to ensure that it does not block fire detection sensors and fire suppression agent nozzles.
3.2.7 Installing Accommodations for Supernumeraries on Aircraft Certificated Under Part 25.
3.2.7.1 Exemption Under 14 CFR Part 11. Part 25 doesn’t describe installing accommodations for supernumeraries, as detailed in 14 CFR part 121. A type certificate (TC) holder or an operator must petition for and receive an exemption under part 11 from the part 25 sections to install accommodations for supernumeraries. The FAA reviews each petition for exemption on its own merits. The enhanced capabilities of supernumeraries over passengers allow the FAA to issue an exemption in certain instances from selected type design requirements normally included for passenger safety. In all cases, however, the desired result is the retention of all passenger safety features to the maximum extent possible, when all factors are considered, and an overall level of safety for supernumeraries comparable to that afforded to passengers. Under part 11, the FAA grants an exemption if it finds the exemption is in the public interest and will provide a level of safety equivalent to that provided under the regulations.
3.2.7.2 Accommodations for Supernumeraries. The FAA has granted exemptions from part 25 to allow operators to install accommodations for supernumeraries. In addition to persons necessary for the safe conduct of the flight, such as large animal handlers, exemptions have been granted for transporting personnel. The exemptions usually involve only a few supernumeraries and the accommodations located immediately aft of the flight deck, consistent with part 121, § 121.583. In granting the exemptions, the FAA has had concerns allowing accommodations for supernumeraries outside the flight deck. The FAA wants exemption holders to:
3.2.7.2.1 Provide a suitable means for preventing smoke penetration into this occupied area;
3.2.7.2.2 Find each occupant physically able;
3.2.7.2.3 Brief all occupants on emergency equipment and procedures;
3.2.7.2.4 Ensure occupant willingness to use the emergency equipment and means of emergency egress provided; and
3.2.7.2.5 Comply with any other requirements of the exemption.
3.2.7.3 Additional Concerns. The FAA may have additional concerns based on the particular aircraft configuration or other features and may require an exemption holder to provide palletized flightcrew rest facilities and access to the cargo compartment to care for live animals.
Par 3.2.7 Page 59
3.2.8 Modifications and Alterations That Could Impact W&B. While the impact of a modification or alteration may be evident with many changes to W&B, the impact of some modifications are not readily evident, such as the following:
3.2.8.1 A modification to incorporate a winglet may change the cargo loading limitation over the wing box;
3.2.8.2 The change in zero fuel weight may alter aircraft fore and aft CG limits;
3.2.8.3 The conversion of class D cargo compartments to class C may heighten the potential for damage to certain design features in the class C compartment intended to sense smoke and discharge a fire retardant when necessary; and
3.2.8.4 The addition of an auxiliary fuel tank depending on its installation might change zonal payload weight limits on the structure.
3.2.9 Design Elements That Could Affect the Cargo Location. The cargo aircraft design should accommodate uncertainties in cargo CG location expected within normal operational accuracies and tolerances. Loading personnel must consider the effect on structural loads from variations in cargo CG location in computing cargo restraint system and cargo deck loads.
Unless the CG of the cargo is actually measured, the assumed location of cargo CG is based on the envelope achieved in operation. This expected variation should be part of the design and is normally a CG position loading limitation on the aircraft. These limitations are normally selected so that they can be achieved by the application of loading procedures. Cargo loading procedures for bulk and nonbulk, such as cargo contained in a ULD, should be reviewed to ensure the cargo CG is within the assumed envelope to avoid safety issues with the cargo restraint system and the affected aircraft structure.
3.2.10 Design Approval Projects That Require ICAs. According to part 21, § 21.50(b), all design approval applicants must submit an ICA as part of the type design for approval.
3.2.11 Design Approvals. A design approval is any approved change or amendment of the type design granted by the FAA or its designees. A design approval defines or alters the approved configuration of an aircraft, aircraft engine, propeller, part, or appliance. The following are examples of design approvals and are subject to the requirements of § 21.50(b):
• TCs.
• Amended TCs.
• STCs.
• Amended STCs.
• Parts Manufacturer Approvals (PMA).
• TSO Authorizations.
• Major repairs and alterations approved by FAA Form 337, Major Repair and Alteration (Airframe, Powerplant, Propeller, or Appliance).
Par 3.2.11 Page 60 SECTION 3.3. UNIT LOAD DEVICES
3.3.1 Classification of ULDs. Certified ULDs, meaning containers or pallets/net combinations, are part of the aircraft cargo restraint system. TSO-C90 provides the certification requirements for ULD specification by reference to (1) National Aerospace Standard (NAS) 3610, Cargo Unit Load Devices—Specifications For, and (2) Aerospace Standard (AS) 36100, Cargo Handling Committee. This specification formally classifies ULDs for which certain strength capabilities have been demonstrated. But the specification also doesn’t approve the installation or use of the ULD where the protection of an aircraft’s systems and structure depends upon the integrity of the ULD. The vertical restraint configuration establishing the ULD type and strength capabilities are part of the classification of a ULD. As appropriate to the type design, the specification of ULDs compatible with a particular aircraft should be identified in the aircraft W&B or cargo loading document. This is the primary means for ensuring the proper ULDs are used in the operation of the aircraft.
NOTE: If an operator uses fire containment covers or fire-resistant containers for enhanced fire protection, the operator should provide instructions in its manual on the proper inspection, installation, storage, cleaning, and use of these products.
3.3.2 Using Certified Nets and Straps.
3.3.2.1 Net and Pallet Combinations. Net and pallet combinations are defined as ULDs by NAS 3610 and AS 36100, which also defines load capability for particular net and pallet combinations. If authorized for use, their arrangement and attachment to an aircraft structure, are identified in Original Equipment Manufacturer (OEM) reference documents. The strength capability of tiedown hardware should be provided, along with any limitations on use or acceptable configuration. The operator will have to obtain FAA approval for the proper use of nets if the OEM has not provided the information. Regardless, the lack of information may result in a failure by an operator to ensure proper restraint of the cargo and a possible unsafe condition.
3.3.2.2 Tiedown Straps. Some approved cargo restraint systems use tiedown straps as a primary restraint means. These systems generally provide instructions for determining the quantity and arrangement of straps required to properly restrain the cargo. In many cases, the strap specification provided by the OEM may be only a required strap rating, such as “5,000-Pound Rated Straps.” In this situation, the operator must obtain FAA approval for the particular straps that it is using. The operator should have procedures (1) for selecting or defining straps that meet the requirements of the approved cargo restraint system, and ensuring that purchased or manufactured straps meet the OEM requirements; and (2) in place that ensure the continued airworthiness of the straps. The straps authorized by the operator should be uniquely identified, such as with a manufacturer part number, in the operator’s operating manuals, and should meet the minimum requirements of TSO-C172, Cargo Restraint Strap Assemblies.
3.3.2.3 Tiedown Strap Authorization. With cargo restraint systems that use tiedown straps as a primary means of restraint, typically the approval is for tiedown to the aircraft’s structure using installed tracks and fittings. These systems do not generally use straps to restrain cargo to pallets, nor does approval per TSO-C90 standards address this issue. If an operator uses straps as a
Par 3.3.1 Page 61 primary means of restraint to a TSO-C90 pallet, the process must be approved by the FAA. In obtaining approval from the aircraft certification office in accordance with Order 8110.4C, the operator must provide the data necessary to demonstrate compliance with the appropriate regulations, including:
3.3.2.3.1 Establishing strap rating requirements.
3.3.2.3.2 How to determine the appropriate quantity of straps and their arrangement.
In determining this, the operator must demonstrate that (a) the orientation of the straps secures the load for all loading conditions, (b) the loads in the straps do not exceed the strap rating, and
(c) the strap loads don’t exceed the capability of the pallet tiedown fittings or tracks. The operator must also demonstrate that using tiedown straps does not introduce loads into the pallet that would exceed the tested strength of the pallet with regard to distributing the load from the pallet tiedown to the cargo restraint system latches, or the strength of the latches.
3.3.2.3.3 Providing the limitations for using the straps. For example, a limitation might be that the use of the straps as a primary restraint of cargo to a TSO-C90 pallet may only be applicable to a single piece of cargo, or packaged or crated goods, where the cargo or package container is inherently strong enough to be restrained by straps or keep the contents from dispersing.
3.3.3 CG Offset Limits.
3.3.3.1 Not Adhering to CG Offset Limits. A ULD specification document such as NAS 3610 and AS 36100 specifies in part the CG offset for which a ULD should have demonstrated specific strengths. If the operator doesn’t adhere to the CG offset limits in operation, the operator may jeopardize the ULD’s restraint of the load and the aircraft’s ability to safely react to loads imposed by the ULD.
3.3.3.2 Floor Design. The design of the cargo floor and cargo restraint system is based on the assumption of loads applied to floor beams. Assumptions used in the floor design may not necessarily be the same as the ULD limits, and ULD CG offset limits for some aircrafts are more restrictive than the TSO-C90 limits. The floor loads should include the total distributed load of the cargo in the ULD and the CG offset that may apply.
3.3.3.3 Design Assumptions. If the designer of the aircraft structural system and CLSs has assumed only a limited CG offset to which the systems must react, the operator must ensure the loaded cargo is within these design assumptions. If an operator doesn’t adhere to the limitations of the design, the operator may impact the safety of operation.
Par 4.1.1 Page 63 CHAPTER 4. ADMINISTRATIVE INFORMATION
4.1.1 How to Obtain Copies of Publications.
4.1.1.1 A listing of the Codes of Federal Regulations (CFR) is in the current version of AC 00-44, Status of Federal Aviation Regulations, and a listing of all ACs is in the current version of AC 00.2, Advisory Circular Checklist and Status of Other FAA Publications.
4.1.1.2 Readers may view and print the CFRs, Aircraft Certification Service (AIR) and Flight Standards Service (AFS) ACs on the FAA’s Regulatory and Guidance Library (RGL) at http://rgl.faa.gov/.
4.1.2 Additional Information. For information concerning this AC, contact the Air Carrier Maintenance Branch (AFS-330) at (202) 267-1675. Submit direct comments regarding this AC to:
Federal Aviation Administration Headquarters Air Carrier Maintenance Branch, AFS-330 5th Floor, 950 L’Enfant Plaza SW Washington, D.C. 20024
Appendix A APPENDIX A. RELATED REGULATIONS A.1 Title 14 of the Code of Federal Regulations (14 CFR) Part 21, Certification Procedures for Products and Parts. Part 21, Subpart E, Supplemental Type Certificates.
Part 21, Subpart K, Parts Manufacturer Approvals. Part 21, Subpart O, Technical Standard Order Approvals.
A.1.1 Section 21.21, Issue of type certificate: normal, utility, acrobatic, commuter, and transport category aircraft; manned free balloons; special classes of aircraft; aircraft engines;
propellers.
A.1.2 Section 21.50, Instructions for Continued Airworthiness and Manufacturer’s Maintenance Manuals Having Airworthiness Limitations Sections.
A.1.3 Section 21.101, Designation of Applicable Regulations.
A.1.4 Section 21.303, Application.
A.2 Part 25, Airworthiness Standards: Transportation Category Airplanes.
A.2.1 Section 25.23, Load Distribution Limits.
A.2.2 Section 25.301, Loads.
A.2.3 Section 25.787, Stowage Compartments.
A.2.4 Section 25.851, Fire Extinguishers.
A.2.5 Section 25.853, Compartment Interiors.
A.2.6 Section 25.855, Cargo or Baggage Compartments.
A.2.7 Section 25.857, Cargo Compartment Classification.
A.2.8 Section 25.858, Cargo or Baggage Compartment Smoke or Fire Detection Systems.
A.2.9 Section 25.1301, Function and Installation A.2.10 Section 25.1309, Equipment, Systems, and Installation.
A.2.11 Section 25.1519, Weight, Center of Gravity, and Weight Distribution.
A.2.12 Section 25.1529, Instructions for Continued Airworthiness.
A.2.13 Section 25.1581, General.
A.2.14 Section 25.1583(c), Operating Limitations, Weight and Loading Distribution.
A.2.15 Section 25.1721, Protection of EWIS.
Appendix 1
Page 2 A.2.16 Appendix F to Part 25.
A.2.17 Appendix H to Part 25—Instructions for Continued Airworthiness.
A.3 Part 43, Maintenance, Preventive Maintenance, Rebuilding, and Alteration.
A.4 Part 45, § 45.15, Marking requirements for PMA articles, TSO articles, and critical parts.
A.5 Part 119, Certification: Air Carriers and Commercial Operators.
A.5.1 Section 119.49, Contents of Operations Specifications.
A.5.2 Section 119.55, Obtaining deviation authority to perform operations under a U.S. military contract.
A.6 Part 121, Operating Requirements: Domestic, Flag, and Supplemental Operations.
Part 121, Subpart G, Manual Requirements.
A.6.1 Section 121.153, Aircraft Requirements: General.
A.6.2 Section 121.363, Responsibility for Airworthiness.
A.6.3 Section 121.367, Maintenance, Preventive Maintenance, and Alteration Programs.
A.6.4 Section 121.373, Continuing Analysis and Surveillance.
A.6.5 Section 121.375, Maintenance and Preventive Maintenance Training Programs.
A.6.6 Section 121.419, Pilots and Flight Engineers: Initial, Transition, and Upgrade Ground Training.
A.6.7 Section 121.422, Aircraft Dispatchers: Initial and Transition Ground Training.
A.6.8 Section 121.693, Load Manifest: All Certificate Holders.
A.6.9 Section 121.1001 – 1007 (Subpart Z), Hazardous Materials Training Program; and Appendix O, Hazardous Materials Training Requirements for Certificate Holders.
A.7 Part 145, Repair Stations.
A.8 Part 234, Airline Service Quality Performance Reports. Section 234.13, Reports by Air Carriers on Incidents Involving Animals During Air Transport.
A.9 Part 382, Nondiscrimination on the Basis of Disability in Air Travel.
Section 382.55(a)(1), Miscellaneous Provisions.
A.10 Title 49 of the Code of Federal Regulations (49 CFR), Transportation, Subtitle B – Other Regulations Relating to Transportation, Chapter I—Pipeline and Hazardous
Appendix A Page 3 (and 4) Materials Safety Administration, Department of Transportation, Subchapter C— Hazardous Materials Regulations, as applicable.
A.11 Related International Regulations.
A.11.1 ICAO Technical Instructions for the Safe Transport of Dangerous Goods by Air.
A.11.2 ICAO Safety Management Manual (SMM).