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During an evaluation of 1794 Edward H Schwartz, of the Aircraft Laboratory, said, ‘Should a complete power failure or exhaus- tion of fuel occur, it would be impossible to make a forced landing. Whether sufficient controllability would exist even with ram-air at high forward speeds, to enable the pilot to establish favourable ejection conditions is questionable’. By December 1956 the engine test rig that represented about three-quarters of the aircraft had been completed and was undergoing tests at Malton. At this stage major concerns were being expressed by USAF scientists, who felt that the 140dB noise level produced by the Vipers was excessive and would create a totally unacceptable cockpit environment. Other problem areas concerned engine heating and temperatures in the special combustors that had been custom manufactured in Eng- land, and the suitability of various metals for exhaust system sections and the controllable outlet vents. Thermal fatigue within the propulsion system represented a substantial worry but new high temperature alloys were being developed during the mid-1950s and it Project 1794 fulfilled much the same role _ sonic cruise at 90,000ft (27,432m) for 37 min- seems likely that suitable materials would as the advanced Silver Bug aircraft, butit used —_ utes and, because the maximum weight was _ have been found. the more powerful and possibly more reliable 27,322 Ib (12,393kg) fully fuelled, a range of As with Silver Bug it was evident that pro- turbo-ramjet system. Estimated maximum 1,000 miles (1,609km) was anticipated. longed supersonic flight would heat the air- speed for the aircraft was Mach 3.5-4.0 witha —_ Dimensions of the 1794 aircraft were 35ft34in _ frame and skin to very high temperatures that service ceiling of 105,000ft (32,000m) and it (10.76m) in diameter and 7ft 84in (2.35m) might prove unacceptable. To cope with this had avery impressive rate of climb calculated _ from the lower surface to canopy top. some airframe parts would have been made at 3 minutes to 75,000ft (22,860m). The air- Project 1794 used six Armstrong Siddeley _ from temperature-resistant Nimonic (Nickel- craft was expected to attain Mach 2.25 super-_ Viper turbojets with their exhausts facing Chromium) alloys while the skin of the air- SI we Si —— Project 1794 fulfilled much the same role as the advanced Silver Bug aircraft, but it used the more powerful and possibly more reliable turbo-ramjet system. Estimated maximum speed for the aircraft was Mach 3.5-4.0 with a service ceiling of 105,000ft (32,000m) and it had avery impressive rate of climb calculated at 3 minutes to 75,000ft (22,860m). The air- craft was expected to attain Mach 2.25 super- sonic cruise at 90,000ft (27,432m) for 37 min- utes and, because the maximum weight was 27,322 lb (12,393kg) fully fuelled, a range of 1,000 miles (1,609km) was anticipated. Dimensions of the 1794 aircraft were 35ft 34in (10.76m) in diameter and 7ft 8%in (2.35m) from the lower surface to canopy top. Project 1794 used six Armstrong Siddeley Viper turbojets with their exhausts facing 68 inwards to drive two 8ft (2.44m)-diameter contra-rotating centrifugal impellers that powered the ramjet system. On their own the Viper turbojets produced 9,000Ib (40kKN) of static thrust, but as an overall system the ducted fan ramjet was expected to provide a variable range of thrust from 17,8001Ib to 32,750 Ib (79KN to 145kN). During the planned test flights the exhaust temperatures would have been initially restricted to 1,200°K, pro- viding a Mach 1.6 capability, but this would have been progressively uprated to 1,700°K, which was calculated to provide a speed of at least Mach 3.7 at extreme altitude. While there was probably some degree of redun- dancy in the propulsion system and the fail- ure of one turbojet might have been tolerable in an emergency, the aircraft was still totally dependent on engine power for stability and control. An early configuration for the MX 1794 aircraft. Avro Canada Avro Canada MX 1794 design evolution. via Bill Rose Secret Projects: Flying Saucer Aircraft