The Deltoid Pumpkin Seed

The AEREON 26 was an experimental aircraft developed to investigate lifting body design with a view to using its shape to create hybrid designs, part airship, part conventional aircraft. It was powered by a piston engine, driving a pusher propeller, and generated lift through the aerodynamics of its lozenge-shaped fuselage.

Although results of flight tests conducted in 1971 were promising, funding for larger and semi-buoyant aircraft was not forthcoming at the time. The story of the test program was recounted by John McPhee in his book ''The Deltoid Pumpkin Seed'' (). This aircraft has a special place in UFO and conspiracy lore, since enthusiasts have drawn parallels between the shape of this aircraft and some reported UFOs from around the same era.

Background

The AEREON Corporation, established in 1959, at first concentrated on the construction of a prototype three-hull hybrid airship, the ''AEREON III''. Completed in 1965, the prototype was lost during taxiing tests the following year, without having flown.

Following the destruction of the ''AEREON III'', the firm sought "a new and better solution." AEREON's Monroe Drew and John Fitzpatrick employed German physicist Jürgen Bock, formerly of the Max Planck Institute for Nuclear Physics, Heidelberg, Germany, and the U.S. Army's Aberdeen Proving Ground, to develop a list of parameters that would be fed into a computer at the General Electric Space Center, Valley Forge, Pennsylvania, in order to determine "the optimum configuration for enclosing maximum volume without too much penalty of drag." ''AEREON 26s deltoid configuration, "a shrewd and practical compromise between an airfoil and a sphere," was the result of these efforts.

Rubber-powered and gasoline-engined models of the configuration were flown and wind tunnel tests conducted before testing of the ''26'' itself began.

Description

Structure and form

According to a paper delivered to the Interagency Workshop on Lighter than Air Vehicles in 1974 by AEREON president William Miller, the 26's shape—dubbed an "aerobody"—was "a lifting-body icof deltoid planform, elliptical cross-sections, and a fineness ratio of 4:5." Among the advantages claimed for this hull form were proximity of the aerodynamic center, center of buoyancy, and center of gravity and a minimal need for trim-control devices, thus facilitating the transportation of "a full range of tonnages at various speeds without major trim requirements."

In McPhee's words, the craft was "a triangle with a deep belly and a vaulting back" or a "delta" when seen from above and a "fat and tremendous pumpkin seed" from the side (hence "deltoid pumpkin seed").

The 26's structure was composed of aluminum tubes (salvaged from the wrecked ''AEREON III''), joined using heli-arc welding and covered with aircraft cloth and aluminum sheet.

Propulsion

The 26 was powered by a single engine, mounted above the trailing edge and driving a pusher propeller. Although the 26 inherited the engine of the ''AEREON III''—apparently a four-cylinder McCulloch of —it appears to have had three different propellers over the course of the test program. After the aircraft experienced difficulty in getting out of ground effect, "a propeller of a different pitch" was fitted. This second propeller was a "virtually unique" example, made of lemonwood, that had been used by Igor Bensen in an unsuccessful attempt on the autogyro speed record. After further testing indicated the 26 to be underpowered, a third propeller was carved to order from yellow birch by Sensenich Propeller and fitted in time for the 26's second series of flight tests in 1971.

The engine's lifespan also had a significant influence on the program; it was "just a drone-aircraft engine, and an old one at that" and had already been used for 12 hours of its 25-hour design life.

Construction and assembly

The 26 was assembled (like its predecessor) by veteran U.S. Navy airship rigger Everett Linkenhoker. Initial construction was in two portions, in "a small shop near Lakehurst, New Jersey, where they were joined together. The aircraft was initially housed in a timber-and-sheetrock box within a hangar at the airport, for reasons of secrecy. Initial taxiing tests were conducted at Red Lion, again under conditions of secrecy. Subsequently, the aircraft was transported by road to the National Aviation Facilities Experimental Center (NAFEC) near Atlantic City for flight testing.

Flying history

The 26 made its first flight, piloted by John Olcott (later president of the National Business Aviation Association), at NAFEC on September 7, 1970. However, as discussed above, it was initially unable to climb out of ground effect. By September 28, following the replacement of the propeller and the removal of some items, the 26 was capable of reaching an altitude of but appeared underpowered. The aircraft was returned to Red Lion before being hauled back to NAFEC on February 24, 1971, following the fitting of vortex generators

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