Gipsy Major engine. The Chipmunk prototype first flew on 22 May 1946 in Toronto. DHC built 217 in Canada, and it was also produced under licence by de Havilland in the UK, which produced 1,000, and by OGMA in Portugal, which built an additional 66. The Chipmunk served with the RCAF, the Royal Air Force (RAF), and at least twelve other air forces. After being largely phased out by the RAF and RCAF in the 1950s and 1960s, surplus Chipmunks achieved widespread popularity for civil sport flying, competition aerobatics, aerial application, and glider towing. DHC-2 Beaver Developed in 1947 for bush flying, the DHC-2 Beaver was designed with input from Canada's bush pilots, who desired a rugged and highly versatile "aerial truck" that would reliably deliver short takeoff and landing (STOL) performance from unimproved airstrips with a half-ton load. An all-metal, high wing monoplane, the Beaver could be equipped with wheels, skis, or floats, and was originally powered by a single Pratt & Whitney R-985 Wasp Junior piston engine. The Beaver was soon adopted by the US Air Force (USAF) and US Army as a liaison aircraft, remaining in service well into the 1970s, and was also used by the militaries of numerous other nations, including Britain, Chile, and Colombia. With almost 1,700 built in a production run lasting two decades, civil Beavers continue plying their trade in many countries around the world. A turboprop conversion, the Turbo Beaver first flew in December 1963, featuring a Pratt & Whitney PT6A engine. The Turbo Beaver offered improved operating weights and STOL performance, along with a longer cabin, allowing maximum accommodation for 11 including the pilot. DHC offered turboprop conversion kits to upgrade piston-powered Beavers, and similar conversions have been performed by aftermarket companies. DHC-3 Otter A follow-on design to the Beaver—originally conceived in 1951 as the King Beaver—the DHC-3 Otter was designed for the same basic roles and is similar in layout, but is a substantially larger and heavier aircraft, a veritable "one-ton truck" that can seat up to eleven. The Otter was originally produced with a 450-kW (600-hp) Pratt & Whitney R-1340 Wasp radial engine, and like the Beaver, the Otter can be fitted with skis and floats; the Otter amphibian features unique four-unit retractable undercarriage, with the wheels retracting into the floats. The type's first flight was undertaken on 12 December 1951 and Canadian certification was awarded in November