Unit Load Devices (ULD) are used as containers for baggage and cargo carried in the holds of appropriately sized and equipped aircraft. They are secured so that they cannot move within the hold while in flight.
ULD Identification
A unique mix of letters and numbers should be used to identify containers and pallets. The IATA standard method consists of three leading letters, four or five digits, and two trailing letters. The three leading letters (for example, AKE, PMC) identify the kind of ULD, the four or five digits are a unique number assigned by the operator, and the two trailing letters reveal a two-letter ICAO code indicating the owner, which might be an airline (for example, BA) or a ULD leasing firm (for example, JG). The IATA ULD Technical Manual contains complete data on the coding standards. ULDs may additionally have a bar code that replicates the visible IATA-standard code.
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Certification of ULD
Most containers, pallets, and nets must be approved for use (“certified”) by the airworthiness authority for the nation in which the manufacturer is situated. Currently, the two most popular certification standards are:
- Technical Standards Order (TSO) C90c of the FAA
- ETSO C90c of the EASA
Other nations, such as China and Australia, have equivalent criteria for ULD certification.
To get clearance or certification from the authorities, the designer must submit calculations and test data demonstrating that the ULD can bear the loads necessary while being restrained in the way specified in the TSO requirements. These loads are exceptionally high in order to demonstrate that the design is capable of restricting the contents of the laden ULD during extreme flying circumstances, such as:
The upload test on an LD3 container demands the LD3 structure to withstand a weight of 9826 lbs in the upward direction while being constrained by just four points at the base for three seconds.
For 3 seconds, a cargo net for a PMC pallet must survive an upload of over 57000 lbs.
Certified and Non Certified ULD
There are several exceptions to the rule that the vast majority of ULD are developed and sold as certified ULD. The initial letter of their identifying code can be used to identify these:
| Certified container | A |
| Non Certified container | D |
| Certified pallet | P |
| Non-certified pallet | F |
All aircraft with holds that are insufficiently strong to contain their contents during harsh flying circumstances and rely on the ULD being fastened to the floor of the hold must utilize certified ULD.
Non-certified ULD may be used in an aircraft with a hold construction capable of withstanding the forces imposed by the contents during harsh flying circumstances.
The B767 Series is an example of this, since it not only has holds intended to handle these stresses, but it also has a container base size that is specific to the aircraft type (units known as DPE (LD2), DQP (LD4), and DQF (LD8)).
Storage of empty ULD
Empty containers should always be placed in appropriate container racking, which should be configured to allow for simple transfer to dollies or other handling equipment without the need of a forklift. Outdoor racking should be designed to keep containers from blowing away in high winds. Empty containers should be piled only if suitable training and controls are in place and the containers are meant to be lifted by forklift.
They should never be left on the ground, even if empty, with the exception of a ULD that is authorized for forklift handling.
Empty pallets may be stored in stacks, taking care that:
Cargo nets are not harmed during the stacking/unstacking operation if they are connected.
- Pallet stacks are appropriately built up on a “base pallet” for transfer to another place by land or air, with appropriate spacing material between the bottom of the pallet stack and the “base pallet,” and attached to the base pallet by tie down straps.
- When removing pallets designated for fork lift truck handling from a stack, the fork tines must not damage the pallet edge rails.
Nets can be permanently connected to a pallet (by locking the fittings in place along one side) or fully detachable. If they are detachable, they should be kept dry.
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Storage of loaded ULD
Loaded ULD must always be stored on a suitable transfer vehicle such as:
- a Dolly
- a slave pallet
- Container racking
- within a Cargo terminal ULD handling and storage system
- on a purpose-built road vehicle or railway wagon
And it should only be transported using specialized equipment equipped with rollers/ball mats or other equivalent support/transfer systems. Specifications for most of these equipment may be found in the IATA Airport Handling Manual.
Above is our brief introduction to ULD and things you should know about it.
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