Unit load device

The "LD3-45" unit loading device

A unit load device, or 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.

Types

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.

Volume indicated is internal volume.

Container type	Volume	Linear dimensions (base width / overall width × depth × height)	Remarks
LD1	4.90 m3 (173 cu ft)	156 / 234 × 153 × 163 cm (61.5 / 92 × 60.4 × 64 in)	contoured, half width
LD2	3.40 m3 (120 cu ft)	119 / 156 × 153 × 163 cm (47 / 61.5 × 60.4 × 64 in)	contoured, half width
LD3	4.33 m3 (153 cu ft)	164 / 201 × 153 × 163 cm (64.5 / 79 × 60.4 × 64 in)	contoured, half width
LD6	8.95 m3 (316 cu ft)	318 / 407 × 153 × 163 cm (125 / 160 × 60.4 × 64 in)	contoured, full width, equivalent to 2 LD3s
LD8	6.88 m3 (243 cu ft)	244 / 318 × 153 × 163 cm (96 / 125 × 60.4 × 64 in)	contoured, full width, equivalent to 2 LD2s; DQF-prefix
LD11	7.16 m3 (253 cu ft)	1318 × 153 × 163 cm (125 × 60.4 × 64 in)	same as LD-6 but without contours; rectangular
Pallet type	Volume	Linear dimensions	Remarks
LD8	6.88 m3 (243 cu ft)	153 × 244 cm (60 × 96 in)	same floor dimensions as container variant; FQA-prefix
LD11	7.16 m3 (253 cu ft)	153 × 318 cm (60.4 × 125 in)	same floor dimensions as container variant; FLA- and PLA-prefixes
LD7 (2 pallet variants)	10.8 m3 (381 cu ft) 11.8 m3 (417 cu ft)	224 × 318 cm (88 × 125 in) 244 × 318 cm (96 × 125 in)	PAG- and P1P-prefixes PMC- and P6P-prefixes

Pallet volumes shown are built 64 in tall for lower deck loading. Height limit for main deck depends on aircraft type.

Aircraft compatibility

LD-3 Unit load devices

LD3s, LD6s, and LD11s will fit 787s, 777s, 747s, MD-11s, 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). 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 767's replacement, the 787, was for it to use the LD3/6/11 family of ULDs to solve the wasted volume issue.

ULD capacity

Aircraft loads can consist of containers, pallets, or a mix of ULD types, depending on requirements. The table below indicates the maximum capacity of an aircraft for all-container and all-pallet configurations. 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" × 125") 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).

A = Airbus; B = Boeing; L = Lockheed; MD = McDonnell-Douglas; F = freighter; ER = extended range; LR = long range

Aircraft	Max Container Cap.	Max Pallet Cap.	Remarks
B727-100F	none	8 pallets*	*88" × 125" pallets only; the 727 is a narrow-body
B727-200F	none	12 pallets*	*88" × 125" pallets only; the 727 is a narrow-body
B727-200C (combi)	none	11 pallets*	*88" × 125" pallets only; the 727 is a narrow-body
B747-100/200/300	30 LD1s	5 pallets + 14 LD1s
B747-400	32 LD1s	5 pallets + 14 LD1s
B747-400ER	26 LD1s	4 pallets + 14 LD1s
B747-400F/ERF	32 LD1s (lower deck) + 30 pallets (main deck)		freighter aircraft, capacity includes all decks
B767-200	22 LD2s	3 pallets + 10 LD2s
B767-300	30 LD2s	4 pallets + 14 LD2s
B767-300ER	30 LD2s	4 pallets + 14 LD2s
B767-300F	24 pallets* (main deck) + 30 LD2s (lower deck)		*accepts 88" × 125" pallets only; freighter aircraft
B767-400ER	38 LD2s	5 pallets + 18 LD2s
B777-200/200LR/ER	32 LD3s	10 pallets
B777F	30 LD3s + 27 pallets	37 pallets	freighter aircraft, capacity includes all decks
B777-300/300ER	44 LD3s	14 pallets
B787-8/-3	28 LD3s	9 pallets
B787-9	36 LD3s	11 pallets
A300B2/B4	20 LD3s	?
A300-600	22 LD3s	4 pallets + 10 LD3s
A300-600F	41 LD3s	25 pallets	freighter aircraft, capacity includes all decks A300-600F deck layout
A310	14 LD3s	3 pallets
A320PF	10 pallets* (main deck) + 7 LD-3-45W (lower deck)	10 AAZ (main deck) + 7 LD-3-45W (lower deck)	*accepts 88" × 125" pallets only; freighter aircraft equipped with fwd cargo 86×121" door
A321PF	13 pallets* (main deck) + 10 LD-3-45W (lower deck)	13 AAZ (main deck) + 10 LD-3-45W (lower deck)	*accepts 88" × 125" pallets only; freighter aircraft equipped with fwd cargo 86×121" door
A330-200	23 pallets or 26 LD3s	8 pallets + 2 LD3s
A330-200F	9 AMA containers + 4 pallets (main deck) + 26 LD3 (lower deck)	22 pallets (main deck) + 8 pallets + 2 LD3 (lower deck)	freighter aircraft, capacity includes all decks A330-200F deck layout
A330-300	32 LD3s	11 pallets
A340-200	26 LD3s	9 pallets
A340-300	32 LD3s	11 pallets
A340-500	30 LD3s	10 pallets
A340-600	42 LD3s	14 pallets
A380-800	38 LD3s	13 pallets
A380-800F	59–71 LD3s	66 pallets	freighter aircraft, capacity includes all decks A380-800F deck layout
MD-11F	32 LD3s	26 pallets
L-1011	16 LD3s	none	all series except 500 (250/200/150/100/50/1 series)
L-1011-500	19 LD3s	4 pallets*	*if equipped with fwd cargo 104" door

Maximum capacity shown does not reflect weight restrictions.
Actual number of ULDs loaded may be lower if aircraft is at its weight limit.

Identification

All ULDs are identified by their 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). For example, AKN 12345 DL means that the ULD is a forkliftable LD3 with the unique number 12345 and its owner is Delta Air Lines.

Common prefixes

• AVY: LD1 with forklift holes
• AKC: LD1 without forklift holes
• DPN: LD2 with forklift holes
• DPE: LD2 without forklift holes
• AKN: LD3 with forklift holes
• AKE: LD3 without forklift holes
• QKE: LD3 same as AKE but made of KEVLAR and designed to be bombproof. Has no forklift holes
• RKN: LD3 with refrigeration unit
• ALB: LD4 with forklift holes
• ALP: LD4 without forklift holes
• AWC: LD6 with forklift holes
• ALF: LD6 without forklift holes
• PAD: LD7, large pallet (88" x 125"), flat
• P1P: LD7, large pallet (88" x 125"), folding wings for overhang
• XAW: LD7, large pallet (88" x 125"), fixed wings for overhang
• PMC: LD7, large pallet (96" x 125")
• DQF: LD8 with forklift holes
• FQA: LD8 pallet (same floor dimensions as DQF)
• AAP: LD9
• RAP: LD9 with refrigeration unit
• ALP: LD11 without forklift holes
• RWB: LD11 with refrigeration unit
• FLA: LD11 pallet
• PLA: LD11 pallet
• AAF: LD26 container
• AAU: LD29 container
• RAU: LD29 container with refrigeration unit
• AMU: LD39 container contour similar to ALF, but deeper and bigger extensions. biggest lower-deck container
• AKH, AKW: LD3-45 mainly for A320/321, same base as AKE, extensions on both sides, 45 inches high
• AMA: M1 container
• AMD: M1H container
• AGA: M2 container
• PGA: M6, large pallet, 96 by 238.5 inches. freighter main deck only
• VRA: M6, large pallet, 96 by 196 inches. Twin car rack
• HMA: Horse stall
• KMA: Sheep and goat pen

Position 1 letter identifies ULD category (certification, ULD type, thermal units);
Position 2 letter identifies standard base dimensions:;
Position 3 letter identifies contour, forklift holes, and other miscellaneous information.

Miscellaneous info

• LD3s and LD2s occupy half the width of the cargo bin of the aircraft they are designed for, therefore are loaded two at a time, side-by-side. LD6s and LD8s are, respectively, their full width counterparts and can only be loaded one at a time.
• LD2s and LD8s are ULDs designed specifically for one type of aircraft, the 767. This is because the 767 has a narrower fuselage than other wide-body aircraft.
• LD1s are ULDs designed specifically for the 747. But LD3s are more commonly used in its place because of ubiquity.
• LD7s inexplicably come in two different floor dimensions.
• Maximum height for all ULDs is 64" for lower deck of aircraft.
• The most common form of ULD damage are holes in container walls from improper forklifting.

Main Deck ULDs

On the main deck of cargo planes are tall ULDs (79 to 96 inches tall, 2006mm to 2438mm tall) with footprints similar to those of pallets 88 or 96 inches wide (2235mm or 2438mm wide) and 62 or 125 inches long (3175mm long). A 62 inch x 88 inch tall ULD is half the volume of a 125 inch x 88 inch pallet. The 20 foot pallet is 238 inches long and 96 inches wide.

There several common types of contoured main deck ULDs, that are contoured (curved to fit in the plane) to provide as much cargo volume as possible. Initially ULD contouring was simply a triangle removed from one or two corners of the profile of the ULD, such as the common LD3 and LD6. Main deck ULDs use curves for the contoured shape to truly maximize cargo volume. Upper deck ULDs are just like lower deck ULDs that are either the full width of the plane with two corners of the profile removed (lower deck LD6 lower, and upper deck AYY), or that container is cut in half, down the center line of the plane, (lower deck LD3 and upper deck AAX).

Main Deck ULDs and pallets are not only taller than lower deck ULDs, they are frequently two or four times longer. They are usually organized like an LD6, using the width of the plane and missing two profile corners, or two very long LD3s, stored in parallel to use the planes width and each missing one profile corner, but often twice or four times as long from planes nose to tail.

Many air cargo companies use main deck ULDs that have both features called dual-profile, so that on small planes such as the Boeing 727, they are stored widthwise and have two corners contoured, and on the bigger Boeing 767, they can be rotated 90 degrees and shipped in parallel like LD3s, so that only one corner is contoured when being used like an LD3. This greatly simplifies transportation of cargo containers at slight cost of cargo volume.

What the actual dimensions of contoured upper deck ULDs are is very hard to know, because most manufacturers only profile width, length and height data.

See also

• 463L master pallet, used for military airdrops
• Norsk Hydro, parent company of Hydro Nordisk, a manufacturer of ULDs
• Rio Tinto Alcan, formerly Alusuisse, a manufacturer of ULDs

External links

• Air Freight Container Specifications
• Hydro Nordisk, manufacturer of ULDs
• Satco, Inc., manufacturer of ULDs