Aircraft cargo handling
Wire harnesses for aircraft cargo loading systems
Powered cargo loading systems move containers and pallets through a freighter's main deck or a passenger aircraft's lower hold. Their wiring is aircraft wiring, with everything that implies.
What is wired in a cargo loading system
A powered cargo handling system typically combines:
- Power drive units (PDUs), the motorised rollers set into the floor that move unit load devices (ULDs) along the deck;
- control panels at the cargo door and along the compartment, used by the loaders;
- sensors that report ULD position and whether locks and restraints are engaged;
- the power and data harnesses connecting them, running beneath the floor alongside structure, drains and other systems.
The environment is harsh even by aircraft standards: spilled liquids, debris, vibration, cold soaks, and maintenance access that means connectors are disturbed more often than elsewhere on the airframe.
The rules that apply
| Reference | What it covers |
|---|---|
| 14 CFR Part 25, Subpart H (EASA CS-25 equivalent) | Electrical wiring interconnection systems (EWIS) on transport-category aircraft, including separation, protection, identification and flammability. |
| SAE AS50881 | Wiring for aerospace vehicles: wire selection, routing, clamping, bend radius, identification and protection. |
| SAE AS22759 family | Fluoropolymer-insulated aerospace wire, widely used in airframe harnesses. |
| MIL-DTL-38999 and similar | Circular connectors common in harsh-environment aerospace harnesses. The aircraft or equipment maker's parts list governs. |
| IPC/WHMA-A-620, Class 3 | Workmanship and acceptance criteria for the harness itself. |
| AS9100 / AS9102 | The aerospace quality system and first article inspection requirements usually flowed down to harness suppliers. |
Approval matters as much as workmanship
A harness that meets every workmanship criterion is still not an airworthy part on its own. Parts for type-certificated aircraft are normally produced under the type-certificate holder's production approval, through its approved supply chain, or under a separate approval such as a Parts Manufacturer Approval (PMA). Installation needs approved data. Before sourcing, establish where your harness sits in that chain and which approvals and flowdowns your supplier must work under. Ground-support equipment and test rigs are usually outside these rules, but often borrow the same workmanship standards.
Build details worth specifying
- Protection under the floor: conduit or sleeving where the harness passes fluid-exposed areas, and drip loops where connectors could collect liquid.
- Connector sealing and backshells suited to frequent disconnection during maintenance.
- Wire identification at the intervals your data requires, legible for the life of the aircraft.
- Separation between power and signal runs, and from other systems as the EWIS rules require.
- Test records per serial number: continuity, insulation resistance and dielectric withstanding voltage as specified, kept with the build traceability.
For the environmental side of the specification, see how to specify transport cables. For choosing a supplier who can work under aerospace flowdowns, see Best Cable Mfg's supplier guide.
Last reviewed 2026-09-17