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de Havilland Canada DHC-6 Twin Otter

History of de Havilland Canada DHC-6 Twin Otter

The

de Havilland Canada DHC-6 "Twin Otter" twin-turboprop utility platform was launched in 1966 and by mid-2018 had more than 960 in service and production worldwide. The series grew from the early single-engine DHC-3 Otter (detailed elsewhere on this page) that arrived in 1953, and has managed to remain active in the skies to this day (2018) - the aircraft itself is a Species pre-evolution DHC-2 "Beaver" (also described elsewhere on this page).

DHC-6 continues to be produced by operators from Algeria and Australia to Venezuela and Yemen - both at the civilian and military market level.

The Twin Otter uses a shoulder-mounted fuselage to support the wings to achieve lift for short periods of time. Powerful Pratt & Whitney Canada turboprops are mounted on each wing of the main aircraft, providing excellent ground clearance for its rotating propeller blades. The cockpit offers two side-by-side seats, facing the nose as usual, giving the crew a good view of the surrounding/coming terrain. The fuselage is board-side and contains a window-lined passenger cabin. The rear wing is slightly tapered and is capped by a vertical fin with the horizontal plane centered on it.

The fixed tricycle landing gear is used for ground work and also provides strong performance on rough terrain, making the Twin Otter a very versatile machine (landing on dirt airfields, sand, etc.). Other forms replace the wheeled landing gear with two floats to allow operation (takeoff/landing) on ??water, allowing the aircraft to operate almost anywhere in the world.

Work on the Twin Otters began in 1964 when de Havilland Canada was looking for a successor to its own DHC-3. The DHC-3 framework and proven lineage were used in the general composition of the newer DHC-6, and the first flight in prototype form was recorded on May 20, 1965.

A key difference between the DHC-3 and the DHC-6 is the latter's wing-mounted twin-turboprop engine layout - while the DHC-3 has only one engine in the nose.

Six aircraft were built for the experimental program, known as "Series 1", and production began with the seventh in 1965. Known as the "100 Series" aircraft, these examples were completed with 108 examples powered by 2 x Pratt & Whitney Canada PT6A20 turboprops.

The "Series 110" became a branch of the series and was adapted for use in British civil airspace.

For 1968, a revised/upgraded model was introduced as the "200 Series", introducing a redesigned nose and overall improved performance as well as other more subtle structural changes (including larger fuselage cargo/access doors) .

In 1969, from this work (aircraft 231 and above) the "300 series" was born and converted to a PWC PT6A-27 series turboprop with a power of 680 hp. Produced in 1988, a total of 614 units were delivered to various customers around the world. The "300S Series" name was applied to the 11 examples that drove a new 11-seat standard with an anti-skid system and wing-mounted spoilers. These were eventually restored to their original 300 series form. The "300M Series" were two aircraft that were proposed as military transport aircraft, but due to little market interest, they were also reverted to their original 300 Series form.

The '310 series' are 300 series aircraft modified for use in UK civil airspace, with the '320 series' a close second, but with the Australian market in mind.

Viking Air of Victoria, BC (the company was founded in 1970) then purchased the existing DHC-6 production line (and all associated machinery and manufacturing space) and acquired the rights to earlier de Havilland Canada aircraft from DHC started 1983-1. They then introduced the "400 Series" Twin Otters in mid-2010 with 2 Pratt & Whitney Canada PT6A-34 engines and variable landing gear options (including floats and skis).

The "400S Series" was developed as a lighter, purpose-built seaplane derivative, a design that was subsequently introduced in 2017.

In addition to the designated civilian DHC-6 platform, there are several notable military market variants: the CC-138 based on the 300 series design is used by the Canadian Armed Forces in search and rescue (SAR) roles. The UV-18A was The Alaska National Guard used it for some time, while the UV-18B was used by the U.S. Air Force Academy as a parachute trainer platform.

The UV-18Cs are three 400 series aircraft acquired by the U.S. Army in 2013.

Although DHC-6 originated in the 1960s, it is still flown in large numbers today (2018).