Unit load device

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Unloading LD3 containers from a Boeing 747

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.

Types[edit]

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[1] 4.90 m3 (173 cu ft) 156 / 234 × 153 × 163 cm
(61.5 / 92 × 60.4 × 64 in)
contoured, half width
LD2[2] 3.40 m3 (120 cu ft) 119 / 156 × 153 × 163 cm
(47 / 61.5 × 60.4 × 64 in)
contoured, half width
LD3 4.50 m3 (159 cu ft) 156 / 201 × 153 × 163 cm
(61.5 / 79 × 60.4 × 64 in)
contoured, half width, dimension according to IATA
LD3-45 3.60 m3 (127 cu ft) 156 / 244 × 153 × 114.3 cm
(61.5 / 96 × 60.4 × 45 in) [3]
double contoured, full width, dimension according to IATA; for loading on Airbus A320 family
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) 318 × 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)
11.52 m3 (407 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[edit]

Cross-section of an Airbus A300 showing LD3 containers

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 (45 inch instead of 64 inch) 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 for it to use the LD3/6/11 family of ULDs to solve the wasted volume issue.

ULD capacity[edit]

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 in × 125 in) 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; Il = Ilyushin; F = freighter; ER = extended range; LR = long range
Aircraft Max Container Cap. Max Pallet Cap. Remarks
B727-100F none 8 pallets*[4] *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
B757-200F 13 SAAs* or 28 AYYs 14 PAGs *Position 14 is AYYs only
B747-100/200/300 30 LD1s[5] 5 pallets + 14 LD1s, or 9 pallets
B747-400 32 LD1s[1] 5 pallets + 16 LD1s, or 9 pallets + 2 LD1s
B747-400ER 26 LD1s[1] 4 pallets + 14 LD1s
B747-400F/ERF 32 LD1s (lower deck) + 30 pallets (main deck)[1] freighter aircraft, capacity includes all decks
B767-200 22 LD2s[2] 3 pallets + 10 LD2s[2]
B767-300 30 LD2s[2] 4 pallets + 14 LD2s[2]
B767-300ER 30 LD2s[2] 4 pallets + 14 LD2s[2]
B767-300F 24 pallets* (main deck) + 30 LD2s (lower deck)[2] *accepts 88" × 125" pallets only; freighter aircraft
B767-400ER 38 LD2s[2] 5 pallets + 18 LD2s
B777-200/200ER/200LR 32 LD3s[6] 10 pallets
B777F 30 LD3s + 27 pallets 37 pallets freighter aircraft, capacity includes all decks
B777-300/300ER 44 LD3s[6] 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
A319 4 LD3-45W + 1 LD3/40 Note LD3 height only 45"; add. cont. acc. IATA contour H
A320 7 LD3-45W Note LD3 height only 45"; add. cont. acc. IATA contour H
A320PF 10 pallets* (main deck) + 7 LD3-45W (lower deck) 10 AAZ (main deck) + 7 LD3-45W (lower deck) *accepts 88" × 125" pallets only; freighter aircraft equipped with fwd cargo 86×121" door
A321 10 LD3-45W Note LD3 heigh only 45"; add. cont. acc. IATA contour H
A321PF 13 pallets* (main deck) + 10 LD3-45W (lower deck) 13 AAZ (main deck) + 10 LD3-45W (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
A380F 59–71 LD3s 66 pallets freighter aircraft, capacity includes all decks A380F deck layout
MD-11 32 LD3s[7] 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
Il-86 16 LD3s  ?
Il-96 18 LD3s  ?
Maximum capacity shown does not reflect weight restrictions.
Actual number of ULDs loaded may be lower if aircraft is at its weight limit.

Identification[edit]

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 after 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.[8]

Common prefixes[edit]

A string of LD3 containers with AKE prefix
An LD3-45 container with AKH prefix
  • AAA: LD7 container (88" x 125"), 81" tall, contoured for maindeck narrow-body
  • AAD: LD7 container (88" x 125"), 96" tall, contoured for maindeck wide-body (aka A1)
  • AAF:[9] LD26 container
  • AAP:[9] LD9
  • AAU:[9] LD29 container
  • AAY: LD7 container (88" x 125"), 81" tall, contoured for maindeck wide-body and narrow-body (aka A2)
  • AAZ: LD7 container (88" x 125"), 64" tall, contoured for maindeck wide-body and narrow-body and any belly (aka L9)
  • AGA:[9] M2 container
  • AKC:[9] LD1 without forklift holes
  • AKE:[9] LD3 without forklift holes/half ALF
  • AKH, AKW: LD3-45 mainly for A320/321, 45" tall, same base as AKE, extensions on both sides
  • AKN:[9] LD3 with forklift holes
  • ALB:[9] LD4 with forklift holes
  • ALD: LD11 container (aka L11)
  • ALF:[9] LD6 without forklift holes
  • ALP:[9] LD11 without forklift holes
  • ALP:[9] LD4 without forklift holes
  • AMA:[9] M1 container
  • AMD:[9] M1H container
  • AMJ: LD7 container (96" x 125"), 96" tall, contoured for main deck wide-body (aka M1)
  • AMU:[9] LD39 container contour similar to ALF, but deeper and bigger extensions. biggest lower-deck container
  • AVY:[9] LD1 with forklift holes
  • AWC:[9] LD6 with forklift holes
  • AYY:[9] Demi, a half-width contoured container typically used for the main deck
  • AYX:[9] AYY with fittings to connect a fire extinguisher so as to carry Dangerous Goods
  • DPE:[9] LD2 without forklift holes
  • DPN:[9] LD2 with forklift holes
  • DQF:[9] LD8 with forklift holes
  • FLA:[9] LD11 pallet
  • FQA: LD8 pallet (same floor dimensions as DQF)
  • HMA:[9] Horse stall
  • KMA:[9] Sheep and goat pen
  • P1P:[9] LD7, large pallet (88" x 125"), folding wings for overhang
  • PAD:[9] LD7, large pallet (88" x 125"), flat
  • PGA:[9] M6, large pallet (96" x 238.5"), freighter main deck only
  • PLA:[9] LD11 pallet
  • PMC: LD7, large pallet (96" x 125")
  • QKE: LD3 same as AKE but made of KEVLAR and designed to be bombproof. No forklift holes.
  • RAP:[9] LD9 with refrigeration unit
  • RAU:[9] LD29 container with refrigeration unit
  • RKN:[9] LD3 with refrigeration unit
  • RWB:[9] LD11 with refrigeration unit
  • SAA: Full-sized version of the AYY
  • SAX: Full-sized version of the AYX
  • VRA:[9] M6, large pallet (96" x 196"), twin car rack
  • XAW:[9] LD7, large pallet (88" x 125"), fixed wings for overhang
  • XKC: LD3 without forklift holes/half ALF

Position 1 letter identifies ULD category (certification, ULD type, thermal units);[8]
Position 2 letter identifies standard base dimensions:[8]
Position 3 letter identifies contour, forklift holes, and other miscellaneous information.[8]

Main-deck ULDs[edit]

On the main deck of cargo planes are 79 to 96 inches (2,007 to 2,438 mm) tall ULDs with footprints similar to those of 88 inches (2,235 mm) or 96 inches (2,438 mm) wide pallets and 62 inches (1,575 mm) or 125 inches (3,175 mm) long. A 62-inch (1,575 mm) wide x 88-inch (2,235 mm) tall ULD is half the volume of a 125-inch (3,175 mm) x 88 inch pallet. The 20 foot pallet is 238 inches (6,045 mm) long and 96 inches (2,438 mm) wide. 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.

There are several common types of contoured main deck ULDs, that are contoured (curved to fit in the plane's body) 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), 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 plane's 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.

See also[edit]

References[edit]

External links[edit]