engine to provide control in pitch, roll and yaw. The lift engines were said to be a useful safety feature in the event of failure of the main 'cruise' engines. Significant design information was gained from flight trials with the Dornier Do 31 aircraft being developed at the same time in Germany. The passenger cabin was conventional with five or six seats abreast, luggage and freight was to be loaded in pre-packed pallets and raised up into the lower fuselage using a system similar to the Douglas DC-8. Extensive wind tunnel testing with 1/10 scale models was carried out. Intended flight operations A conventional take-off and landing flight profile was shown to cover a "noise footprint" of 20 square miles (50 km2) in line with an airport's runway when using a limit of 90 decibels, by using an approach path of six degrees (double the normal angle) and a climb out path of 15 degrees the footprint could be reduced to 3 square miles (8 km2). This form of STOL operation was expected to be in place at British city airports by the late 1970s. To reduce the noise footprint further to a circle with a diameter of just 3,000 ft VTOL operations were expected to commence in the early 1980s. The suggested minimum noise take-off technique for the HS.141 was to use full power from the lift engines in a vertical climb to 250 ft (76 m) then reducing power to 83% to continue this climb to 1,000 ft (300 m). At this height the aircraft would transition into forward flight using vectored thrust from the lift engines and then accelerate and climb to 2,000 ft (600 m) using increasing thrust from the cruise engines. By this stage the aircraft would have reached an airspeed of 168 knots (310 km/h) and would be fully supported by its wings alone, the lift engines being shut down and covered by hinged doors. For an approach to a vertical landing the procedure was to be virtually reversed with the approach commencing at 2,000 ft (600 m) and 4 miles (6.4 km) from the landing point. Cancellation Despite the work and funds that Hawker Siddeley had expended, the lack of enthusiasm for civil VTOL operations combined with the cancellation of the lift engine development, doomed the project. Variants HS.141 "datum aeroplane" Basic variant. 102–119 passengers dependent on seat pitch. To have used 16