ⓘ Boeing Pelican. In a 2005 United States congressional report evaluating 11 proposed airlift and sealift platforms for military mobility, the Boeing Pelican was ..

                                     

ⓘ Boeing Pelican

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 Boeings 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 aircrafts sole indispensable launch customer, Boeing quietly discontinued further development of the Pelican program.

                                     

1. Description

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 6 million pounds 2.7 million kilograms; 3.000 short tons; 2.700 metric tons. 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 120-foot wingspan 37 m could not produce enough lift to fly the large vehicle out of ground effect.

                                     

1.1. Description Flight characteristics

In its most efficient flight mode, the Pelican flies in ground effect at 20 to 50 feet 6.1 to 15.2 metres above the water, measured from the fixed structure the underside of the fuselage, though the aircraft distance can be reduced to 10 to 40 ft 3.0 to 12.2 m depending on its wingtip positioning. It has a cruise speed of 240 knots 276 miles per hour; 444 kilometres per hour, 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. Boeings 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 400 kn 460 mph; 741 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 worlds highest mountain ranges except for the Himalayas.

The aircraft takes off and lands at airfields differently from conventional airliners because of the Pelicans 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.

                                     

1.2. Description Fuselage

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. For military purposes, the upper deck is designed to carry troops or cargo containers, while the main deck has a height of 18 ft 4 in 5.6 m so that it can hold oversized vehicles such as tanks or helicopters.

                                     

1.3. Description Wings

The aircrafts wings are mounted to the fuselage in a high wing configuration, and they are unswept and mostly parallel to the ground in their inner sections. The wings droop downward in their outer sections to enhance ground effect, also having a slight backward sweep in the leading edge and forward sweep in the trailing edge. To let the aircraft change shape for different types of operations, the wings are hinged within the drooping sections, and the axis of rotation is parallel to the fuselage. The wings fold slightly for takeoffs and landings, and they fold about 90 degrees to reduce clearance amounts during taxiing and ground operations. At the ends of the folding wing sections, wingtips droop below the rest of the aircraft by up to 10 ft 3.0 m when the larger folding wing and the wingtip are in their normal positions. To avoid ground or water contact, the wingtips are hinged for active rotation, as the rotational axis is perpendicular to the direction of flight but not necessarily parallel to the ground. If a wingtip accidentally touches the ground or water, it minimizes the contact by passively swiveling upward and backward, with the clock position moving from six oclock to three oclock or nine oclock, depending on which side of the wing is viewed.

The wings have an area of more than one acre 44.000 square feet; 4.000 square metres; 0.40 hectares and a mean aerodynamic chord of 97 ft 29.6 m. 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. There are no leading edge devices or anti-icing systems, but the trailing edge has flaps that span the entire wing. The wings are designed with a large thickness-to-chord ratio to reduce aircraft weight and 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.



                                     

1.4. Description Power plant

The Pelican is powered by eight turboprop engines, which produce an output of 80.000 shaft horsepower 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. The new engines would probably be a hybrid derived from two General Electric GE engines: the LM6000 marine engine, an aeroderivative gas turbine based on the CF6-80C2 turbofan used on the Boeing 767 and other widebody aircraft that powers fast ferries, cargo ships, and stationary electrical generation plants, combined with a core based on the GE90 turbofan, which powers the Boeing 777 twin-engine widebody aircraft. The Pelicans many engines mitigate a single-engine loss scenario, so just as the Boeing 777-300ER can lift its 777.000 lb 352.000 kg; 388 short tons; 352 t maximum takeoff weight with just one of its two engines working, seven operational engines out of the eight total can provide enough power for the 7.7-times greater MTOW of the Pelican. The power plant converts about 38 percent of the fuels energy into thrust, a comparable engine efficiency to those in modern widebody aircraft.

The engines are paired behind four sets of coaxial contra-rotating propellers that are positioned at the leading edge of the inner sections of the wings. A set of contra-rotating propellers has eight blades 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 GE90 turbofan, is at least about two and a half times the size of the propellers on the aforementioned turboprop and 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. While a single engine drives each set of contra-rotating propellers on some common propfan aircraft such as the An-22 and the Tupolev Tu-95 respectively the heaviest and fastest turboprop-powered aircraft in the world, the Pelican requires the two propellers within a contra-rotating propeller set to be matched with twin engines. This arrangement is due to the amount of power needed to lift the large aircraft off the ground and to ascend to and cruise at high altitude, but one of the engines in each engine pairing can be turned off while cruising in ground effect, as the paired engines are connected by a geared combiner gearbox so that one or both of the engines can turn the propellers.

                                     

1.5. Description Payload

The Pelican has a maximum payload weight of 2.800.000 pounds 1.400 short tons; 1.270 metric tons, which allows an army to transport 70 heavy expanded mobility tactical trucks HEMTTs or 52 M270 multiple launch rocket systems MLRSs. It can carry 17 M-1 Abrams tanks in five rows of three abreast and one row of two abreast. The Pelican can also move ten CH-47D Chinook helicopters, which only use about ten percent of the payload weight capacity and are confined to the main deck due to their vehicle size. While human transportation would typically be in the form of military troops, the aircraft can be used to transport 3.000 passengers as a commercial airliner, though the aircraft is able to ferry the equivalent of 8.000 passengers if factors other than payload weight are ignored such as cabin area.

As a cargo freighter, the Pelican is designed to handle the standard intermodal shipping containers used in shipping, rail, and trucking instead of the smaller unit load devices containers and pallets that dominate the air cargo industry. The aircraft is designed to handle two layers of containers on its main deck. 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 aligned parallel to the fuselage in two rows of ten abreast. Within a cumulative cargo area of 29.900 sq ft 2.780 m 2 ; 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. At the maximum payload weight, a Pelican aircraft holding the maximum number of containers will have an average gross weight of 15.700 lb 7.140 kg; 7.87 short tons; 7.14 t per container.



                                     

1.6. Description Range

At the maximum payload, the aircraft can travel 3.000 nautical miles 3.400 miles; 5.500 kilometres in ground effect, which is about the distance between New York City and London. Carrying a smaller payload of 1.500.000 lb 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, roughly the distance between Hong Kong and Buenos Aires, taking about 42 hours 1.7 days in travel time. This distance is greater than the worlds longest airline flights, 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. 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.

                                     

1.7. Description Ground accommodation

Unlike the typical tricycle undercarriage of most airliners, the undercarriage arrangement for the Pelican distributes the aircrafts weight on ground over two rows of 19 inline landing gears, which are mounted on each side directly under the length of the fuselage. Each landing gear row contains dual-wheel retractable landing gears distributed over about 180 ft 55 m in length, with an average center-to-center distance of 10 ft 3 m; 120 in; 3.048 mm between each inline landing gear. As the landing gear rows are spaced about 45 ft 14 m apart from each other, the Pelicans wheel span may meet the code letter F standard of the International Civil Aviation Organization ICAO Aerodrome Reference Code, which is used for airport planning purposes. While only the nose landing gear can be steered on most airliners, each landing gear on the Pelican is steerable, so the aircraft can more easily perform crosswind landings and complete turns at a smaller radius when it is on the ground.

The combined 76 aircraft tires on the Pelican far exceeds the 32 wheels of the current largest cargo aircraft, the Antonov An-225. The average load per wheel is 78.900 lb 35.800 kg; 39.5 short tons; 35.8 t, or meaningfully larger than the typical maximum design load of 66.000 lb 30.000 kg; 33 short tons; 30 t for large, long-range aircraft. Pavement loading from the Pelican may be comparatively low, though. Boeing claims that the aircrafts ground flotation characteristic, a measure tied to the grounds ability to keep a vehicle from sinking, at maximum takeoff weight is superior to that of the much-smaller McDonnell-Douglas DC-10, which imposes the most demanding flotation requirements among aircraft of its era. However, according to the designer of the Aerocon Dash 1.6 wingship a larger, sea-based ground effect vehicle that was investigated by DARPA a few years before the Pelican was proposed, regular Pelican operation at airports with high water tables underground may result in a type of seismic wave that leads to cracks in airport terminal buildings and eventually causes greater damage within months.

A conventional takeoff and landing CTOL aircraft, the Pelican requires a takeoff runway length of 8.000 ft 2.400 m at MTOW, which is shorter than the listed distance required for the much-lighter Boeing 747-400F. For Pelican landings, a satisfactory airfield meets the desired runway length and width of 5.500 and 100 ft 1.676 and 30 m, respectively, and has a load classification number LCN of at least 30 if paved or 23 if unpaved. The aircraft may also be able to use a marginal airfield, which has a minimum runway length of 4.000 ft 1.219 m, width of 80 ft 24 m, and an LCN if known of 30 paved or 23 unpaved. A runway with an LCN of 30 can thus withstand the Pelican at lower weights, but it should not host some versions of the Boeing 737 narrowbody aircraft including the popular 737-800 nor most versions of the 777, regardless of whether the runway is long and wide enough to handle those other planes. Boeing maintains that many military airfields are able to host aircraft that have the Pelicans large wingspan, adding that in the conflict regions of Southwest Asia from the Fertile Crescent and the Arabian peninsula eastward to Pakistan, at least 323 airfields meet the satisfactory landing criteria, with additional airfields that can meet the marginal criteria or be restored to satisfactory or marginal. The aircrafts length and wingspan, however, make the Pelican too big for the "80-meter box," the informal name of the maximum size specified in the ICAO Aerodrome Reference Code.

The Pelican requires at the least a ramp or elevator to load and unload cargo. A more ideal setup is to build dedicated ground infrastructure at airports for transloading, such as cranes, railcars, and apron jacks, which approaches the sophistication of container terminal facilities used at the docks of major marine ports.



                                     

2. Specifications

General characteristics

  • Wing area: more than 43.560 sq ft 4.047 m 2
  • Max. takeoff weight: 6.000.000 lb 3.000 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
  • Length: 400 ft 122 m
  • Height: 18 ft 4 in fuselage main deck interior 5.6 m
  • Wingspan: 340 ft folded; 500 ft unfolded; effective wingspan of 850 ft in ground effect 104 m; 152 m; 259 m
  • Payload: 2.800.000 lb 1.400 short tons; 1.270.000 kg; 1.270 t
  • Wetted aspect ratio: 1.56
  • Fuel capacity: 2.200.000 lb 1.000.000 kg; 1.100 short tons; 1.000 t
  • Propeller diameter: 50 ft 15.2 m; 600 in; 1.520 cm
  • Mean aerodynamic chord: 97 ft 29.6 m
  • Propellers: four-bladed propellers, one per engine
  • Powerplant: eight × LM6000-GE90 hybrid turboprops, 80.000 shp 59.700 kW each
  • Cargo container capacity: 178 TEUs
  • Capacity: 3.000 passengers
  • Empty weight: 2.160.000 lb 980.000 kg; 1.080 short tons; 980 t
  • Aspect ratio: 5.4 effective AR of 15.8 in ground effect
  • Cargo area: 29.900 sq ft 2.780 m 2 ; 0.69 acres; 0.278 ha

Performance

  • Cruise speed: 240 knots 276 mph; 444 km/h; 405 ft/s; 123 m/s in ground effect; 400 knots 460 mph; 741 km/h; 675 ft/s; 206 m/s at 20.000 feet
  • 10.000 nmi 11.500 mi; 18.500 km in ground effect
  • At 1.400-short-ton payload 2.800.000 lb; 1.270.000 kg; 1.270 t in ground effect: 3.000 nmi 3.400 mi; 5.500 km
  • At 750-short-ton payload 1.500.000 lb; 680.000 kg; 680 t
  • Range
  • 6.500 nmi 7.480 mi; 12.000 km at 20.000 feet
  • At 1.110-short-ton allowable cargo load ACL 2.220.000 lb; 1.010.000 kg; 1.010 t in ground effect: 6.000 nmi 6.900 mi; 11.000 km
  • lift-to-drag: 21 36 in ground effect; 45 in ground effect with winglets in unswept position
  • Service ceiling: 25.000 ft 7.600 m

Armament

  • 10 CH-47D Chinook helicopters using only the main deck
  • 70 heavy expanded mobility tactical trucks HEMTTs
  • 52 M270 multiple launch rocket systems MLRSs
  • 17 M-1 Abrams tanks