Vickers V-1000 the world's first jet-powered commercial transport aircraft, the Vickers Viscount, the world's first turboprop-powered commercial airliner, and the Bristol Britannia, a turboprop-powered aircraft capable of conducting routine transatlantic flights; all of these designs had their origins in the specifications laid out by the wartime Brabazon Committee. With these aircraft, Britain appeared to be on track to capturing a large slice of the global demand for civil aircraft for the foreseeable future. Meanwhile, the Royal Air Force (RAF) had been pursuing development of a new generation of strategic bombers, these being the Vickers Valiant, the Avro Vulcan, and the Handley Page
Turboprop Kaman's K-125 synchropter, which used a Boeing T50 turboshaft engine to power it on 11 December 1951. Compared to turbofans, turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly the same speed as small regional jet airliners but burn two-thirds of the fuel per passenger. However, compared to a turbojet (which can fly at high altitude for enhanced speed and fuel efficiency) a propeller aircraft has a lower ceiling. The most common application of turboprop engines in