|Bell D-2005/D-2022, D-246A, D-266|
1961 - project - 1966
Designs D-2005 and D-2022 were two operational variants of a four ducted-fan VTOL aircraft designed in 1959 and having a layout comparable to the X-22. They were intended to be used as assault transports for thirty soldiers.
Design D-246A was a tactical military transport using the tilting rotor principle. Propulsion was to be provided by two 2.200shp Lycoming T55-L-55 turboshafts driving two 12m three-blade rotors, but these rotors were not located at the wingtips. The tilting nacelles were designed with a fixed outboard wing panel with aileron so that this panel tilted with the rotor. Extra power in level flight would have been provided by four turbofans arranged in pairs in nacelles under the wing (these nacelles also housed the retractable main undercarriage). At the rear of the fuselage, a large cargo ramp would have permitted the loading of oversize loads and light vehicles in a 8.05m long cargo compartment.
In 1966, Bell submitted a composite research aircraft project to the US Army Aviation Materiel Laboratories at Fort Eustis, Virginia, for competitive evaluation. The Model 266, as it was known, used the tilting rotor principle. Streamlined nacelles at each wingtip contained two T64 engines as well as reduction gearboxes driving three-bladed semirigid rotors. Blades were of constant chord but tapered rapidly in thickness to provide maximum strength inboard and minimum drag outboard. Rotor hubs and controls were completely enclosed within a removable spinner fairing. Nacelle conversion was controlled by two synchronized, hydraulically-operated screw-jacks. A spanwise driveshaft interconnected the gearboxes so that one engine could drive both rotors.
A.J.Pelletier "Bell Aircraft since 1935", 1992
Technical data for Bell 246A
Span (excluding rotors): 19.50m, rotor diameter: 12.0m, length: 18.16m, height overall: 7.31m, wing area: 55.9m2, loaded weight: 17214kg, empty weight: 10254kg