The Boeing Pelican ULTRA (Ultra Large Transport Aircraft) was a proposed ground effect fixed-wing aircraft under study by Boeing Phantom Works in the early 2000s.
Development 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.
Internal deliberation 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 faster, such as successfully deploying an Army brigade of 3,000 troops and of equipment within instead of the 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 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 . 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 with high drooping wings as its solution. It applied for a patent in October 2001 on a ground effect airplane that would form the basis for the Pelican, aside from some eventually omitted design elements such as a T-tail, upward-pointing (positive dihedral) winglets, an additional middle row of landing gears, and a loading ramp at the back of the fuselage. The patent also listed open-ended fuselage compartment dimensions of at least high, wide, and long, with an aircraft wingspan of at least . Its example fuselage length and wingspan of and 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 applied for a patent on variable-sweep, downward-pointing (negative dihedral, or anhedral) winglets to help ground effect vehicles avoid water contact while minimizing aerodynamic drag; the patent drawings show a cylindrical fuselage, which may indicate that a pressurized aircraft was considered at the time, although the final Pelican design has an unpressurized fuselage. The next month, without explicitly naming Boeing as the aircraft originator, the Army cited the Pelican as an emerging technology to improve strategic responsiveness in its 2002 Transformation Roadmap. In July, a U.S. Transportation Command team lead at Scott Air Force Base mentioned the Pelican as a practical solution for moving troops and equipment over long distances. Meanwhile, the designers evaluated three different aircraft sizes with mean takeoff weights of and wingspans of , respectively.
Public introduction The Pelican was formally introduced to the public at the 2002 Farnborough International Airshow in July, but with few specifics. As described in its physical form, the aircraft mostly resembled future versions of the Pelican, except that the winglets were reverted to upward-pointing to maximize lift. Boeing announced that the Pelican could fly up to in altitude and that the wingspan was limited by a so that it could be used on existing runways and taxiways. Both parameters were drastically smaller than the Pelican's eventual final specifications, however, and although Boeing's original patent called for a folding wing, news reports did not mention a folding mechanism, so it was unclear whether the stated wingspan represented an unfoldable, unfolded, or folded width. On the other hand, Boeing mentioned a theoretical Pelican payload of up to , which was much larger than the final specified maximum payload and was actually about equal to the final maximum takeoff weight. While Boeing said that the U.S. Army was evaluating the Pelican in war games as a solution to "beat ships across the ocean," and that the company was jointly studying the aircraft with the U.S. Defense Advanced Research Projects Agency (DARPA), it noted that full concept studies would not begin for another 5–8 years, and the aircraft would have to wait for at least 20 years before entering service.
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 , a wing area of over , a payload of of cargo, an increased flight service ceiling of or more in altitude, and a range for a smaller payload of , 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 and research conferences. In November 2002, Boeing also applied for a patent on an automated system for controlling large, multiple-wheel steering aircraft (such as the Pelican) during ground maneuvers, crosswind landings, and crosswind takeoffs.
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, and the Navy also showed interest though it was directing its attention more toward hybrid ultra-large airships (HULAs). 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, contended Boeing, because in comparison with traditional air cargo transports, the Pelican is less expensive and offers much more payload volume and weight. Boeing stated that the Pelican's continued development could depend on a positive result in the U.S. Army's Advanced Mobility Concepts Study (AMCS), which would describe the future mobility concepts and capabilities needed by the armed forces in years 2015 to 2020.
By the latter half of 2003, Boeing Phantom Works was showcasing the Pelican on its web site and in technology expositions. The U.S. Army published the AMCS report in December 2003, but the Pelican was not among the list of the eight most promising future mobility platforms for evaluation. Despite this setback, Boeing in 2004 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 .
Project stoppage 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 about its ability to produce the aircraft for service by a 2015 timeframe.
Though Boeing filed a couple of patent applications in mid-2005 relating 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. By April 2006, a report on Boeing internal documents showed that its long-term aircraft focus was primarily about low-cost and environmentally efficient passenger planes of conventional size, and there was no mention of the Boeing Pelican. Facing diminished odds of a large order from the U.S. armed forces, which collectively represented the aircraft's sole indispensable launch customer, Boeing quietly discontinued further development of the Pelican program.
Design Like the pelican water bird for which it is named, the concept aircraft can both skim over water and soar to heights above mountain peaks. However, 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. The aircraft is a land-based ground effect vehicle that operates from conventional runways despite having an enormous maximum takeoff weight (MTOW) of . During flight, the Pelican 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. This capability differentiates the aircraft from some previously built ground effect vehicles such as the Caspian Sea Monster, whose relatively narrow could not produce enough lift to fly the large vehicle out of ground effect.
Flight characteristics In its most efficient flight mode, the Pelican flies in ground effect at above the water, measured from the fixed structure (the underside of the fuselage), though the aircraft distance can be reduced to depending on its wingtip positioning. It has a cruise speed of , which lets it skim above 90 percent of the ocean about 90 percent of the time before high waves force it to fly out of ground effect. Boeing's ocean wave studies during 2000 revealed that north–south aircraft routes and many east–west routes worked very well in ground effect, with flights at latitude between 30 degrees north and 30 degrees south being very efficient, while polar routes were more challenging. The aircraft can also cruise over land at with an altitude of . 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 , so it can clear all of the world's highest mountain ranges except for the Himalayas.
The aircraft takes off and lands at airfields differently from conventional airliners because of the Pelican's unusual landing gear configuration. A typical aircraft pitches its nose up right before final liftoff or touchdown, but the Pelican appears to have little or no rotation. Like the Boeing B-52 Stratofortress strategic bomber, the Pelican seems to levitate on or off the ground.
Fuselage