ULD (unit load device)
Unit Loading Devices (ULD) are standardized containers in the airline industry, certified by the ICAO.
A unit load device is a pallet or container used to load luggage, freight, and mail on wide-body aircraft and specific narrow-body aircraft. It allows a large quantity of cargo to be bundled into a single unit. Since this leads to fewer units to load, it saves ground crews time and effort and helps prevent flight delays. Each ULD has its own packing list (or manifest) so that its contents can be tracked. [Clausen 1998, pp. 142-144;Kummer 2009, p. 113]
According to the different size of aircraft a lot of different ULD have been created which do not fit all in every aircraft model.
ULDs come in two forms: pallets and containers. ULD pallets are rugged sheets of aluminum with rims designed to lock onto cargo net lugs. ULD containers, also known as cans and pods, are closed containers made of aluminum or combination of aluminum (frame) and Lexan (walls), which, depending on the nature of the goods to be transported, may have built-in refrigeration units. [Clausen 1998, pp. 142-144]
The size of the aircraft fuselage limits the size of the ULD. The different measurements of different aircraft models of different aircraft manufacturer’s it means not every ULD fit perfectly into the freight compartment of the aircraft.
Unlike the ISO container, where ships are built “around” the measurements of an container the ULD is built on the availability of space in an aircraft body.
There are certain interchange abilities but mostly the space cannot be utilized fully. These are compromises not loose efficiency while handling the ULD on ground. Interchangeability of certain ULDs between LD3/6/11 aircraft and LD2/8 aircraft is possible when cargo needs to be quickly transferred to a connecting flight. Both LD2s and LD8s can be loaded in LD3/6/11 aircraft, but at the cost of using internal volume inefficiently (33 ft³ wasted per LD2). Only the LD3 of the LD3/6/11 family of ULDs can be loaded in a 767; it will occupy an entire row where two LD2s or one LD8 would otherwise have fit (90 ft³ wasted per LD3). Policies vary from airline to airline as to whether such transfers are allowed. [Clausen 1998, pp. 142-144; Kummer 2009, p. 113]
All ULDs are identified by their unique ULD number. A three-letter prefix identifies its type, followed by a 4 or 5 digit serial number (4 if prior to October 1, 1993; either 4 or 5 if post October 1, 1993) to uniquely identify it from others of the same type, and ending with a two character (alpha-numerical) suffix identifying the ULD's owner (if an airline, often the same as IATA designator codes).
See Standard Units