BAC One-Eleven BAC One-Eleven The British Aircraft Corporation One-Eleven, also known as the BAC-111 or BAC 1-11, is a British short-range jet airliner used during the 1960s and 1970s. It was the second short-haul jet airliner to enter service, following the French Sud Aviation Caravelle. The aircraft was also produced under licence in Romania during the 1980s as the Rombac One-Eleven. The One-Eleven was conceived by Hunting Aircraft and developed by the British Aircraft Corporation when Hunting merged into BAC along with other British aircraft manufacturers in 1960. The One-Eleven was intended to replace the turboprop Vickers Viscount on short-range routes. The
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