|Boeing image of the proposed Pelican|
|Role||Outsize cargo ground effect freight aircraft|
|Manufacturer||Boeing Phantom Works|
The Boeing Pelican ULTRA is intended as a large-capacity transport craft initially for military use, with possible subsequent availability as a commercial freighter serving the world's largest cargo centers. It is significantly larger and more capable than the biggest existing commercial airliners, commercial freighters, and military airlifters. The Pelican is not targeted for civilian transportation, but it can be converted to a commercial airliner transporting up to 3,000 passengers, although if factors other than payload weight are ignored (such as cabin area), the aircraft is able to transport the equivalent of 8,000 passengers (including carry-on items, luggage, seats, stowage bins, and other cabin furnishings).
The design process for what became the Pelican began in early 2000, when designers in the Phantom Works division of Boeing started working on solutions for the United States armed forces objective of moving thousands of troops, weapons, military equipment, and provisions to a war or battle scene within a month or less, ideally within four days (96 hours) instead of the three to six months (91 to 183 days) it required in the past. In particular, the Department of Defense had requested a vehicle of any mode (land, air, or sea) with the ability to move one million pounds (450,000 kilograms; 500 short tons; 450 metric tons) of cargo. Knowing that the United States Army was investigating large airships and airship-airplane hybrids, Boeing Phantom Works internally considered and rejected at least three known design iterations: a large blimp or dirigible airship, a smaller but wider airship that creates dynamic lift while in forward motion, and then back to a larger airship that flies at low altitude with wings spanning 700 feet (213 metres). It also looked at and discarded a fast oceangoing ship and a sea-based ground effect vehicle.
Boeing Phantom Works then selected a land-based ground effect vehicle as its solution, filing a patent in October 2001 that would form the basis for the Pelican, with a few exceptions such as a T-tail and upward-pointing winglets. The patent also listed open-ended fuselage compartment dimensions of at least 16 ft (4.9 m) high, 24 ft (7.3 m) wide, and 100 ft (30 m) long, with an aircraft wingspan of at least 300 ft (91 m). Its example fuselage length and wingspan of 420 ft (128 m) and 480 ft (146 m) would come close to the final Pelican configuration, though.
Initial artist drawings of the aircraft were made public in early 2002. In May 2002, Boeing filed a patent for variable sweep downward-pointing winglets applicable to ground effect vehicles in which a cylindrical fuselage was displayed, suggesting that a pressurized aircraft was seriously considered at the time. Meanwhile, the designers internally evaluated three different aircraft sizes with mean takeoff weights of 3,500,000, 6,000,000, and 9,900,000 pounds (1,800, 3,000, and 5,000 short tons; 1,600, 2,700, and 4,500 metric tons). The Pelican was then formally introduced to the public at the 2002 Farnborough International Airshow in July, but with few details. Boeing announced that the Pelican could fly up to 2,000 to 3,000 ft (610 to 914 m) in altitude and that the aircraft was being studied jointly with the US Defense Advanced Research Projects Agency (DARPA), but it warned that the aircraft's service entry would have to wait for at least 20 years.
In the September 2002 edition of its company news magazine, Boeing published an article highlighting the Pelican and revealing more of its final specifications, including a 500-foot wingspan (152 m), a wing area of over one acre (43,560 sq ft; 4,047 m2), a payload of 1,400 short tons (1,270 t) of cargo, an increased flight service ceiling of 20,000 ft (6,100 m) or more in altitude, and a range for a smaller payload of 6,500 to 10,000 nautical miles (7,480 to 11,500 miles; 12,000 to 18,500 kilometres), depending on the flight mode. In addition, it stated that the Pelican could move 17 M-1 Abrams tanks, and that the aircraft would be offered along with the C-17 Globemaster III transport, the CH-47 Chinook helicopter, and the Advanced Theater Transport as part of the company's mobility solution for the U.S. armed forces. This article attracted international media coverage, and as Boeing Phantom Works continued to mature the design (including selection of the mid-size vehicle option), additional details about the aircraft began to appear over the next year in newspaper, general science magazine, and aviation industry print publications.
According to Boeing, the Pelican aircraft technology was starting to gain followers among the decision makers evaluating the mobility initiatives within the Army and the Air Force. The market could support over 1,000 of this type of aircraft by 2020, Boeing asserted, if the military used this aircraft and if air transport's share of the transoceanic cargo shipping market increased to two percent from one percent (versus the current 99 percent for ocean shipping transport). Taking some market share from ocean shipping could occur, Boeing contended, because in comparison with traditional air cargo transports, the Pelican is less expensive and offers much more payload volume and weight.
By the latter half of 2003, Boeing Phantom Works was showcasing the Pelican on its web site and in technology expositions, and in 2004 it continued low-key educational and evangelical promotion of the aircraft. At the 2004 Farnborough Air Show, Boeing announced that the Pelican had entered wind tunnel testing and that the aircraft's service ceiling was increased to 25,000 ft (7,600 m).
In a 2005 United States congressional report evaluating 11 proposed airlift and sealift platforms for military mobility, the Boeing Pelican was assessed as marginally feasible to enter service in 2016, ranking behind six platforms that were deemed feasible. The lower grade was due to the tremendous investment required to develop an operational product because of the scale of the aircraft and the use of high-risk technologies, which might prevent the aircraft from achieving technology readiness level (TRL) 5. With this assessment, the report essentially reaffirmed Boeing's previous concerns from 2003 about its ability to produce the aircraft for service by a 2015 timeframe.
Aside from a couple more Boeing patents, which were filed in mid-2005 and relate to cargo container handling and automatic altitude measurement, no other public announcements appear to have been made about the aircraft after the report was issued. Facing diminished odds of a large order from the aircraft's sole indispensable launch customer, Boeing quietly halted further development of the Pelican program.
Like the pelican water bird for which it is named, the concept aircraft can both skim over water and soar to heights above famous mountain peaks. Unlike previously built ground effect vehicles, the Pelican is not designed for contact with bodies of water, so although the aircraft cannot take off or land at sea, it can be designed to be lighter and more aerodynamic. It is a land-based ground effect vehicle that operates from conventional runways; during flight, it exits ground effect to climb a few thousand feet while the surface below the aircraft changes from ocean to solid ground, then enters descent to arrive at an airport like other airplanes.
In its most efficient flight mode, the Pelican flies in ground effect at 20 feet (6.1 metres) above the water with a cruise speed of 240 knots (276 miles per hour; 444 kilometres per hour). The aircraft can also cruise over land at 390 kn (449 mph; 722 km/h) with an altitude of 20,000 ft (6,100 m). At higher flight levels, the aircraft can attain nearly jet-like speeds in thinner air but consumes fuel faster than in ground effect mode, though the aircraft still performs at a fuel efficiency similar to a Boeing 747-400F aircraft freighter. The Pelican can fly to a height of 25,000 ft (7,600 m), so it can clear all of the world's highest mountain ranges except for the Himalayas.
At the maximum payload of 2,800,000 pounds (1,400 short tons; 1,270 metric tons), the aircraft can travel 3,000 nautical miles (3,450 miles; 5,560 kilometres), which is about the distance between New York City and London. Carrying a smaller payload of 1,500,000 pounds (750 short tons; 680 t), or slightly over half of the maximum payload, it can travel 10,000 nmi (11,500 mi; 18,500 km) in ground effect. This distance is greater than the listed range of any commercial airliner, and it is just short of the 10,800 nmi great-circle distance (12,400 mi; 20,000 km) between two antipodes, which theoretically represents nonstop range to anywhere on earth (ignoring geopolitical barriers, headwinds, and other factors). The aircraft can alternatively carry that payload at high altitude with a decreased range of about 6,500 nmi (7,480 mi; 12,000 km),  or approximately the distance between New York City and Shanghai.
A double-deck structure with a rectangular cross-section, the fuselage is 400 ft (122 m) long and is unpressurized except within the cockpit. It is capped in front by a large swing-nose door, which allows for loading and unloading cargo through both decks, and in back by conventional tailfin and tailplane stabilizers attached directly to the fuselage, instead of the heavier T-tail empennage that is typically used by other ground effect planes. The main deck has a cabin area that is 50 ft (15 m) wide and 200 ft (61 m) long, or half of the fuselage length.
The aircraft's wings are mounted to the fuselage in a high wing configuration, and they are mostly parallel to the ground in their inner sections. The wings droop downward in their outer sections to enhance ground effect, and they are hinged within the drooping sections to let the wings change shape for different types of operations; the wings fold slightly for takeoffs and landings, and they fold about 90 degrees to reduce clearance amounts during taxiing and ground operations. There are wingtips at the end of the folding wing sections. The wing area is more than one acre (44,000 square feet; 4,000 square metres; 0.40 hectares), and the wingspan is 500 ft (152 m), although the wingspan can be reduced to as small as 340 ft (104 m) when the wing is folded. Because of their unusually large thickness, the wings are designed to hold part of the overall payload, a feature that is unique in modern aircraft and only rarely had been implemented in previous-era aircraft, such as in the Junkers G.38.
Four turboprop engines power the aircraft, and they are mounted to the leading edge of the inner sections of the wings. Producing an output of 60,000 to 80,000 shaft horsepower (45,000 to 60,000 kilowatts) each, the engines are about five times more powerful than the engines on turboprop or propfan-powered military transport aircraft such as the Airbus A400M (using Europrop TP400 engines) and the Antonov An-22 (Kuznetsov NK-12MA) and An-70 (Progress D-27). Each engine has eight-bladed contra-rotating propellers (four blades on the front propeller and four blades on the back propeller) that are 600 inches (50 ft; 15 m) in diameter, which dwarfs the turbofans of the GE9X powering Boeing's 777X twin-engine widebody aircraft, is at least about two and a half times the size of the propellers on the aforementioned turboprop/propfan engines, and is noticeably bigger than the largest marine ship propellers, although it is less than half as wide as the main rotors on the largest helicopters. The aircraft requires the most power during takeoff and climb; however, while cruising in ground effect, half of the engines can be turned off because of the smaller power requirements.
The aircraft can handle two layers of standard 20-foot long (6.1 m) intermodal shipping containers on its main deck because of its 18.3-foot height (5.6 m). The containers are arranged longitudinally within the fuselage in eight rows of five containers, followed by two rows of three containers, for a total of 46 containers in a layer. The upper deck only holds one container layer, but it allows access to the cargo area of the wings, each of which can hold 20 containers. Within a cumulative cargo area of 29,900 sq ft (2,780 m2; 0.69 acres; 0.278 ha), the entire aircraft can transport 178 containers, or the equivalent of a single-stacked, containerized freight train stretching over two-thirds of a mile (1.1 km) long.
The weight of the aircraft is distributed over two rows of 19 retractable, steerable landing gears mounted on each side underneath the length of the fuselage. Each landing gear contains two wheels, so the aircraft has 76 wheels total, which far exceeds the 32 wheels of the current largest cargo aircraft, the Antonov An-225. Its length and wingspan make the Pelican too big for the "80-meter box," the informal name of the maximum size specified in the International Civil Aviation Organization (ICAO) Aerodrome Reference Code that is used for airport planning purposes, but the aircraft's wheel arrangement may comply with the outer main gear wheel span portion of the code letter F standard (the same letter category as the Airbus A380 and the Boeing 747-8), based on the cabin width and depending on the exact placement of its wheels. While the Pelican may be too large to use most commercial airports, many military airfields are able to host aircraft that have the Pelican's large wingspan. The aircraft's weight might not damage airport pavements beyond the normal quantifiable airplane wear (takeoffs, landings, taxiing, and ground operations), but regular Pelican operation may result a type of seismic wave that leads to cracks in airport terminal buildings and eventually causes greater damage within months.
- Capacity: 3,000 passengers
- Payload: 2,800,000 lb (1,400 short tons; 1,270,000 kg; 1,270 t) 178 TEUs
- Length: 400 ft (122 m)
- Wingspan: 340 ft folded; 500 ft unfolded; effective wingspan of 804 ft in ground effect (104 m; 152 m; 245 m)
- Height: 18 ft 4 in (fuselage main deck interior) (5.6 m)
- Wing area: more than 43,560 sq ft (4,047 m2)
- Aspect ratio: 5.4 (effective AR of 15.8 in ground effect)
- Max. takeoff weight: 5,900,000 lb (2,950 short tons; 2,700,000 kg; 2,700 t)
- Cabin dimensions, main deck (height x width x length): 18.3 ft × 50 ft × 200 ft (5.6 m × 15.2 m × 61.0 m)
Cargo area: 29,900 sq ft (2,780 m2; 0.69 acres; 0.278 ha)
Mean aerodynamic chord: 100 ft (30.5 m)
- Powerplant: 4 × turboprop propfans, 60,000-80,000 shp (44,700–59,700 kW) each
- Propeller diameter: 50 ft (15.2 m; 600 in; 1,520 cm)
- Cruise speed: 240 knots (Mach 0.363; 276 mph; 444 km/h; 405 ft/s; 123 m/s) in ground effect; 390 knots (Mach 0.590; 449 mph; 722 km/h; 658 ft/s; 201 m/s) at 20,000 feet
- Range: at MTOW: 3,450 mi (5,560 km; 3,000 nmi)
at 1,500,000 pounds (750 short tons; 680,000 kg; 680 t) payload: 11,500 miles (18,500 km; 10,000 nmi) in ground effect, 7,480 miles (12,000 km; 6,500 nmi) at 20,000 feet
- Service ceiling: 25,000 ft (7,600 m)
- lift-to-drag: 21 (36 in ground effect)
Aircraft of comparable role, configuration and era
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