UNIT LOAD DEVICE
A unit load device (ULD) 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 delayed flights. Each ULD has its own packing list (or manifest) so that its contents can be tracked.
The IATA publishes ULD regulations and notes there are 900,000 in service worth more than one billion USD, averaging $1100 each.
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. Examples of common ULDs and their specifics are listed below.
|LD3-45||3.7 m³ / 131 ft³||114.3/45||153.4/60.4||156.2/61.5||243.6/95.8||Full||double||AKH||A320|
|LD2||3.5 m³ 124 ft³||162.6/64||119.4/47||156.2/61.5||Half||single||DPE||Boeing WB|
|LD3||4.5 m3 / 159 ft3||156.2/61.5||200.7/79||AKE||Airbus WB, Boeing WB, DC-10/MD-11, L-1011|
|LD1||5.0 m³ / 175 ft³||233.7/92||AKC||Boeing WB, MD-11|
|LD4||5.7 m3 (200 ft3)||243.8/96||243.8/96||Full||none||ALP||767, 777, 787|
|LD8 (2×LD2)||7.1 m3 / 252 ft3||317.5/125||double||DQF||767/787|
|LD11||7.2 m3 / 256 ft3||317.5/125||none||ALP||747, 777, 787, DC-10/MD-11|
|PLA pallet||7.1 m3 (250 ft3)||PLA||747, 777, 787|
|LD6 (2×LD3)||8.9 m3 / 316 ft3||406.4/160||double||ALF||747/777/787, DC-10/MD-11|
|LD26 (P1P base)||13.3 m3 (470 ft3)||223.5/88||AAF||747/777/787, DC-10/MD-11|
|LD7 winged pallet||14.0 m3 (495 ft3)||P1P||747, 777, 787, DC-10/MD-11|
|LD7/P1P pallet||10.5 m3 (370 ft3)||317.5/125||none||P1P||All Widebodies|
|LD9 (P1P base)||10.8 m3 (381 ft3)||AAP||Boeing WB, DC-10/MD-11|
|LD29 (P1P base)||14.4 m3 (510 ft3)||472.4/186||double||AAU||747|
|LD39 (P6P base)||15.9 m3 (560 ft3)||243.8/96||AMU||747|
|P6P pallet||11.5 m3 (407 ft3)||317.5/125||none||P6P||747, 767, 777, 787, DC-10, MD-11|
LD3s, LD6s, and LD11s will fit 787s, 777s, 747s, MD-11s, Il-86s, Il-96s, L-1011s and all Airbus wide-bodies. The 767 uses the smaller LD2s and LD8s because of its narrower fuselage. The less common LD1 is designed specifically for the 747, but LD3s are more commonly used in its place because of ubiquity (they have the same floor dimensions such that one LD3 takes the place of one LD1). LD3s with reduced height (1.143 metres (3.75 ft) instead of 1.63 metres (5.3 ft)) can also be loaded on the Airbus A320 family. LD7 pallets will fit 787s, 777s, 747s, late model 767s (with the big door), and Airbus wide-bodies.
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.
One of the design requirements of the 787 was that it use the LD3/6/11 family of ULDs to solve the wasted volume issue.
|A300-600||22 LD3||4 + 10 LD3||4 + 10 LD3||20||21|
|A310||15 LD3||3 + 7 LD3||3 + 7 LD3||15||16|
|B707-320C||no lower ULD||13||13|
|B727-100C||no lower ULD||8||8|
|B737-200C||no lower ULD||7||7|
|B737-300SF||no lower ULD||9|
|B737-400SF||no lower ULD||10 ½|
|B737-700C||no lower ULD||8||8|
|B737-800SF||no lower ULD||11 ½|
|B747 classic||30 LD1||28||28||36|
|B747-400||32 LD1||9 + 4 LD1||9 + 2 LD1||30||30|
|B747-8/8F||40 LD1||12 + 2 LD1||34|
|B757-200F||no lower ULD||15|
|B767-200||22 LD2||3 + 10 LD2||3 + 10 LD2|
|B767-300||30 LD2||4 + 14 LD2||4 + 14 LD2||14||16||26|
|B777-200||32 LD3||10 + 2 LD3||10||27|
|B777-300||44 LD3||14 + 2LD3||14|
|B777-9||48 LD3||16||14 + 4 LD3|
|B787-8||28 LD3||9||8 + 2 LD3|
|DC-8-55F||no lower ULD||13|
|DC-8-62/72F||no lower ULD||14|
|DC-8-61/63/71/73F||no lower ULD||18|
|DC-9-15F||no lower ULD||6|
|DC-9-32F||no lower ULD||8|
|MD-80SF||no lower ULD||8||8||12|
|DC-10||26 LD3||5 + 8 LD3||22||30|
|MD-11||32 LD3||6 + 14 LD3||26||26||34|
|L-1011||19 LD3||4 + 7 LD3|
The B727-200 had an option to hold 11 specific 45.5 in–92.4 in × 41.1 in × 43.4 in (1.16 m–2.35 m × 1.04 m × 1.10 m) base-full width x height x depth, 78 cu ft (2.2 m3) underfloor containers.
Aircraft loads can consist of containers, pallets, or a mix of ULD types, depending on requirements. In some aircraft the two types must be mixed as some compartments take only specific ULDs.
Container capacity of an aircraft is measured in positions. Each half-width container (LD1/LD2/LD3) in the aircraft it was designed for occupies one position. Typically, each row in a cargo compartment consists of two positions. Therefore, a full-width container (LD6/LD8/LD11) will take two positions. An LD6 or an LD11 can occupy the space of two LD3s. An LD8 takes the space of two LD2s.
Aircraft pallet capacity is measured by how many PMC-type LD7s 96 by 125 in (240 by 320 cm) can be stored. These pallets occupy approximately three LD3 positions (it occupies two positions of one row and half of the two positions of the following row) or four LD2 positions. PMCs can only be loaded in cargo compartments with large doors designed to accept them (small door compartments are container only).