The de Havilland Canada DHC-6 Twin Otter is a Canadian STOL (short takeoff and landing) utility aircraft developed by de Havilland Canada in the mid-1960s and still in production. It was built by De Havilland Canada from 1965 to 1988. In 2006, Viking Air purchased the type certificate and restarted production in 2008, before re-adopting the name De Havilland Canada. In 2023, DHC started production of the 300-G, an upgraded version of the Series 400 with Garmin avionics.
The aircraft's fixed tricycle undercarriage, STOL capabilities, twin turboprop engines and high rate of climb have made it a successful commuter airliner, typically seating 18–20 passengers, as well as a cargo and medical evacuation aircraft. The Twin Otter has also been popular with commercial skydiving operations and is used by the United States Army Parachute Team and the 98th Flying Training Squadron of the United States Air Force.
Design and development
Development of the aircraft began in 1964, with the first flight on 20 May 1965. A twin-engine replacement for the single-engine DHC-3 Otter retaining the DHC-3's STOL qualities, its design features included double-slotted trailing-edge flaps and ailerons that work in unison with the flaps to boost STOL performance. The availability of the Pratt & Whitney Canada PT6A-20 turboprop in the early 1960s made the concept of a twin feasible. A DHC-3 Otter with its piston engine replaced with two PT6A-4Power – The Pratt & Whitney Canada Story, Kenneth H. Sullivan and Larry Milberry, CANAV Books 1989, , p.146 engines had already flown in 1963. It had been extensively modified for STOL research. To bush plane operators, the improved reliability of turboprop power and the improved performance of a twin-engine configuration made it an immediately popular alternative to the piston-powered Otter which had been flying since 1951.
The first six aircraft produced were designated Series 1, indicating that they were prototype aircraft. The initial production run consisted of Series 100 aircraft, serial numbers seven to 115 inclusive. In 1968, Series 200 production began with serial number 116. Changes made at the beginning of Series 200 production included improving the STOL performance, adding a longer nose that was equipped with a larger baggage compartment (except for aircraft fitted with floats), and fitting a larger door to the rear baggage compartment. All Series 1, 100, and 200 aircraft and their variants (110, 210) were fitted with the PT6A-20 engines.
In 1969, the Series 300 was introduced, beginning with serial number 231. Both aircraft performance and payload were improved by fitting more powerful PT6A-27 engines. This was a engine that was flat rated to for use in the Series 300 Twin Otter. The Series 300 proved to be the most successful variant by far, with 614 Series 300 aircraft and their subvariants (Series 310 for United Kingdom operators, Series 320 for Australian operators, etc.) sold before production in Toronto by de Havilland Canada ended in 1988.
In 1972, its unit cost was US$680,000, In 1976, a new -300 would have cost $700,000 ($ million 31 years later) and is still worth more than $2.5 million in 2018 despite the -400 introduction, many years after the -300 production ceased. 844 had been produced by the time the first production end run ended in 1988.
New production
After Series 300 production ended, the remaining tooling was purchased by Viking Air of Victoria, British Columbia, which manufactures replacement parts for out-of-production de Havilland Canada aircraft. On 24 February 2006, Viking purchased the type certificates from Bombardier Aviation for all out-of-production de Havilland Canada aircraft (DHC-1 through DHC-7)."Viking Acquires De Havilland Type Certificates." aiabc.com, 24 February 2006. Retrieved: 15 May 2010. The ownership of the certificates gives Viking the exclusive right to manufacture new aircraft.
On 17 July 2006, at the Farnborough Airshow, Viking Air announced its intention to offer a Series 400 Twin Otter. On 2 April 2007, Viking announced that with 27 orders and options in hand, it was restarting production of the Twin Otter, equipped with more powerful Pratt & Whitney Canada PT6A-34 engines."Viking restarts Twin Otter production." flightglobal.com, 2 April 2007. Retrieved: 15 May 2010. As of November 2007, 40 firm orders and 10 options had been taken and a new final assembly plant was established in Calgary, Alberta.Sarsfield, Kate. "Viking Twin Otter Series 400 certification approaches." Flightglobal, 3 February 2010. Retrieved: 15 May 2010."News releases." Viking Air. Retrieved: 15 May 2010. Zimex Aviation of Switzerland received the first new production aircraft, serial number 845, in July 2010."Twin Otter – Zimex Aviation." zimex.ch. Retrieved: 15 May 2010. By mid-2014, Viking had built 55 new aircraft at its Calgary facility. The production rate as of summer 2014 was about 24 aircraft per year. In April 2015, Viking announced a reduction of the production rate to 18 aircraft per year. On 17 June 2015, Viking announced a partnership with a Chinese firm, Reignwood Aviation Group; the group would purchase 50 aircraft and become the exclusive supplier of new Series 400 Twin Otters in China.
Major changes introduced with the Series 400 include Honeywell Primus Apex fully integrated avionics, deletion of the AC electrical system, modernization of the electrical and lighting systems, and use of composites for non load-bearing structures such as doors.Phelps, Mark. "Updated Twin Otter Takes Off." flyingmag.com, 16 October 2008. Retrieved: 15 May 2010.
The 100th Series 400 Twin Otter (MSN 944) was displayed at the July 2017 EAA AirVenture Oshkosh. At the time 38% were operated as regional airliners, 31% were in military aviation use, 26% in industrial support and 5% were in private air charter. Seventy were on regular landing gear wheels, 18 were configured as straight or amphibious floatplanes, 10 had tundra tires and two had wheel skis.
In 2019, Viking started making plastic components for the Twin Otter by 3D printer to help reduce cost. Twin Otter production was suspended in 2019 during the COVID-19 pandemic. In July 2022, DHC announced that it was reviewing the program and supply chain, with a decision on when to resume production expected "in the near future". In 2023, its equipped price was $7.25M.
In June 2023, Viking, now operating as De Havilland Canada, started production of the new DHC-6 Classic 300-G.
On 20 March 2026, De Havilland Canada delivered its 1000th DHC-6 Twin Otter produced and delivered aircraft to SATENA, a regional government-owned airline of Colombia.
Operational history
Twin Otters could be delivered directly from the factory with floats, skis, or tricycle landing gear fittings, making them adaptable bush planes for remote and northern areas. Areas including Canada and the United States, (specifically Alaska) had much of the demand. Many Twin Otters still serve in the Arctic and subarctic, but they can also be found in Africa, Australia, Asia, Antarctica, and other regions where bush planes are the optimum means of travel. Their versatility and manoeuvrability have made them popular in areas with difficult flying environments such as Papua New Guinea. In Norway, the Twin Otter paved the way for the network of short-field airports, connecting rural areas with larger towns. The Twin Otter showed outstanding reliability, and remained in service until 2000 on certain routes. Widerøe of Norway was, at one time, the world's largest operator of Twin Otters. During one period of its tenure in Norway, the Twin Otter fleet achieved over 96,000 cycles (take-off, flight, and landing) per year.
A number of commuter airlines in the United States got their start by operating Twin Otters in scheduled passenger operations. Houston Metro Airlines (which later changed its name to Metro Airlines) constructed their own STOLport airstrip with a passenger terminal and maintenance hangar in Clear Lake City, Texas, near the Johnson Space Center. The Clear Lake City STOLport was specifically designed for Twin Otter operations. According to the February 1976 edition of the Official Airline Guide, Houston Metro operated 22 round-trip flights every weekday at this time between Clear Lake City (CLC) and Houston Intercontinental Airport, now George Bush Intercontinental Airport, in a scheduled passenger airline shuttle operation.North American Official Airline Guide (OAG), February 1976 edition Houston Metro had agreements in place for connecting passenger feed services with Continental Airlines and Eastern Air Lines at Houston Intercontinental, with this major airport having a dedicated STOL landing area at the time specifically for Twin Otter flight operations. The Clear Lake City STOLport is no longer in existence.
The Walt Disney World resort in Florida was also served with scheduled airline flights operated with Twin Otter aircraft. The Walt Disney World Airport, also known as the Lake Buena Vista STOLport, was a private airfield constructed by The Walt Disney Company with Twin Otter operations in mind. In the early 1970s, Shawnee Airlines operated scheduled Twin Otter flights between the Disney resort and nearby Orlando Jetport, now Orlando International Airport, as well as to Tampa International Airport. This service by Shawnee Airlines is mentioned in the "Air Commuter Section" of the 6 September 1972 Eastern Air Lines system timetable as a connecting service to and from Eastern flights. This STOL airfield is no longer in use.
Another commuter airline in the United States, Rocky Mountain Airways, operated Twin Otters from the Lake County Airport in Leadville, Colorado. At an elevation of above mean sea level, this airport is the highest airfield in the United States ever to have received scheduled passenger airline service, thus demonstrating the wide-ranging flight capabilities of the Twin Otter. Rocky Mountain Airways went on to become the worldwide launch customer for the larger, four-engine de Havilland Canada Dash 7 STOL turboprop, but continued to operate the Twin Otter, as well.
Larger scheduled passenger airlines based in the United States, Canada, Mexico, the Caribbean and Australia, particularly jetliner operators, also flew Twin Otters, with the aircraft providing connecting feeder service for these airlines. Jet aircraft operators which also flew the Twin Otter included Aeronaves de Mexico, Air BC, Alaska Airlines, ALM Antillean Airlines, Ansett Airlines, Cayman Airways, Frontier Airlines, LIAT, Norcanair, Nordair, Ozark Air Lines, Pacific Western Airlines, Quebecair, South Pacific Island Airways, Time Air, Transair, Trans Australia Airlines (TAA), Wardair and Wien Air Alaska. airline system timetables airline system timetables & OAG flight guides In many cases, the excellent operating economics of the Twin Otter allowed airlines large and small to provide scheduled passenger flights to communities that most likely would otherwise never have received air service.
Twin Otters are also a staple of Antarctic transportation."NSF PR 01-29 — Civilian Aircraft to Evacuate South Pole Patient" nsf.gov. Retrieved: 15 May 2010. Four Twin Otters are employed by the British Antarctic Survey on research and supply flights, and several are employed by the United States Antarctic Program via contract with Kenn Borek Air. On 24–25 April 2001, two Twin Otters performed the first winter flight to Amundsen–Scott South Pole Station to perform a medical evacuation."2001—Doctor Evacuated from the South Pole." www.70south.com. Retrieved: 15 May 2010.Williams, Jeff. "Pilot says pole flight wasn't his most challenging." usatoday.com."Pilots return after historic South Pole rescue."cbc.ca/news. Retrieved: 15 May 2010."Aircraft in Antarctica: British Antarctic Survey." antarctica.ac.uk. Retrieved: 31 December 2007.