|Bell Model 240 UTTAS|
1972 - project
In October 1965, a Qualitative Material Development Objective was approved by the DoD for what became known as the Utility Tactical Transport Aircraft System (UTTAS) in order to replace the ageing UH-1. The specification called for an aircraft able to carry a crew of three and eleven troops, a 3150kg slung load, at a cruising speed of 270-320km/h. Other requirements included a 2.3-2.8m/s vertical climb rate, a 2.3 hours endurance, and a 1500m single-engine ceiling. Requests for proposals were issued to the US industry on 5 January, 1972, submissions being made in due course by Bell, Boeing-Vertol and Sikorsky. The three companies submitted five proposals and Boeing-Vertol and Sikorsky were selected to proceed to prototype construction, contracts being placed on 30 August, 1972.
Bell's proposal was the Model 240, a twin-engine, fourteen-seat helicopter, larger than the UH-1, with four-blade main and tail rotors. Among the most significant design features were the two 1500shp General Electric T700-GE-700 turboshafts, a fail-safe modular transmission, a four-bladed swept-tip gimbaled rotor with a new Wortmann aerofoil for enhanced aerodynamic efficiency.
A.J.Pelletier "Bell Aircraft since 1935", 1992