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de Havilland Canada DHC-6 Twin Otter

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DHC-6 Twin Otter
A West Coast Air Twin Otter floatplane
Role utility aircraft
Manufacturer de Havilland Canada
Viking Air - (400 series)
First flight May 20, 1965
Introduction 1966
Produced 1965–1988
2008–present
Number built 845

The DHC-6 Twin Otter is a Canadian 20-passenger STOL (Short Takeoff and Landing) utility aircraft developed by de Havilland Canada. The aircraft's fixed tricycle undercarriage, STOL abilities and high rate of climb have made it a successful cargo, regional passenger airliner and MEDEVAC aircraft. In addition, the Twin Otter has been popular with commercial skydiving operations.

Design and development

File:TWIN otter.jpg
Aerovias DAP DHC-6 Series 300 at Puerto Williams
A Twin Otter making a normal landing approach in Queensland.

Development of the aircraft began in 1964, with the first flight on May 20, 1965. A twin-engined replacement for the single-engined Otter had been planned by de Havilland Canada. Twin engines not only provided improved safety but also allowed for an increase in payload while retaining the renowned STOL qualities. 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 550 shp (410 kW) Pratt and Whitney Canada PT6A-20 propeller turbine engine in the early 1960s made the concept of a twin more feasible. To bush operators, the improved reliability of turboprop power and the improved performance of a twin-engined configuration made it an immediately popular alternative to the single engine, 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 number 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 to 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 550 shaft horsepower PT6A-20 engines.

In 1969, the 300 series was introduced, beginning with serial number 231. Both aircraft performance and payload were improved by fitting more powerful PT6A-27 engines. This was a 680 hp (510 kW) engine that was flat-rated to 620 hp (460 kW) 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 sub-variants (Series 310 for United Kingdom operators, Series 320 for Australian operators, etc.) sold before production ended in 1988.

New production

First flight of the Series 400 technical demonstrator by Viking Air, October 1, 2008

After series production ended, the remaining tooling was purchased by Viking Air of Victoria, British Columbia, which manufacture replacement parts for all of the out of production de Havilland Canada aircraft. On February 24, 2006 Viking purchased the type certificates from Bombardier Aerospace for all the out of production de Havilland DHC-1 through DHC-7 aircraft.[1] The ownership of the certificates gives Viking the exclusive right to manufacture new aircraft.

On July 17, 2006, at the Farnborough Air Show, Viking Air announced its intention to offer a "Series 400" Twin Otter. On April 2, 2007 Viking announced that with 27 orders and options in hand, it was restarting production of the Twin Otter with a more powerful Pratt & Whitney Canada PT6A-34/35 engine.[2] As of November 2007, 40 firm orders and 10 options have been taken and a new assembly plant has been established in Calgary, Alberta with customer deliveries commencing in the second quarter of 2010.[3][4] Zimex Aviation of Switzerland will receive the first aircraft.[5]

Major changes introduced with the Series 400 include Honeywell Primus Apex fully integrated avionics, deletion of the AC electrical system, deletion of the beta backup system, modernization of the electrical and lighting system, and use of composites for non-load-bearing structures such as doors.[6]

Announced orders

Operational history

de Havilland Canada DHC-6 Twin Otter on Beechey Island at seamen graves of John Franklin expedition (Nunavut, Canada) c. 1997. Note the "tundra tires."

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 including Canada and the United States, specifically Alaska. Many Twin Otters still serve in the far north, but they can also be found in Africa, Australia, Antarctica and other regions where bush planes are the optimum means of travel. Their versatility and maneuverability have made them popular in areas with difficult flying environments, including Papua New Guinea. In Norway, the Twin Otter paved the way for the network of short-field airports, connecting the rural areas with the larger towns with 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 (takeoff, flight and landing) per year.

Twin Otters are a staple of Antarctic transportation.[9] 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 April 24–25, 2001, two Twin Otters performed the only winter flight to Amundsen-Scott South Pole Station to perform a medical evacuation.[10][11][12][13]

As of August 2006, a total of 584 Twin Otter aircraft (all variants) remain in service worldwide. Major operators include: Libyan Arab Airlines (16), Maldivian Air Taxi (17), Trans Maldivian Airways (15), Kenn Borek Air (33) and Scenic Airlines (11). Some 115 airlines operate smaller numbers of the aircraft including Yeti Airlines in Nepal, Malaysia Airlines which uses the Twin Otter exclusively for passenger and freight transportation to the Kelabit Highlands region in Sarawak, and in the United Kingdom the FlyBe francise operator Loganair which uses the aircraft to service the island of Barra in the Hebrides islands. This scheduled service is unique as the aircraft lands on the beach and the schedule is partly influenced by the tide tables. The Twin Otter is also used for landing at the world's shortest commercial runway on the Caribbean island of Saba, Netherlands Antilles.

Ontario's Ministry of Natural Resources is also a long-time operator of the Otter.

Transport Canada still owns three DHC-6 Twin Otters, but they now see very limited flying time, as their role in Coastal Surveillance has been replaced by a fleet of DHC-8 aircraft.[citation needed]

The Twin Otter has been popular with commercial skydiving operations. It is able to carry up to 22 skydivers to over 13,500 ft[14] (a large load compared to most other aircraft in the industry); presently, the Twin Otter is used in skydiving operations in many countries. The United States Air Force operates three Twin Otters for the United States Air Force Academy's skydiving team.

On September 25, 2008, the Series 400 Technology Demonstrator achieved "power on" status in advance of an official rollout.[15][16] First flight of the Series 400 technical demonstrator, C-FDHT, took place October 1, 2008 at Victoria Airport.[17][18] Two days later, the aircraft departed Victoria for a ferry flight to Orlando, Florida, site of the 2008 National Business Aviation Association (NBAA) Conference and exhibition. Viking expects the Series 400 to receive its type certificate from Transport Canada and the European Aviation Safety Agency prior to first delivery of the aircraft in the second quarter of 2010.[3]

The first new build Series 400 Twin Otter (sn 845), made its first flight on February 16, 2010 in Calgary, Alberta.[19]

Variants

de Havilland Canada DHC-300 Twin Otter on Bird Island, Seychelles.
DHC-6 Series 100
Twin-engined STOL utility transport aircraft, powered by two 550 shp (432 kW) Pratt & Whitney Canada PT6A20 turboprop engines.
DHC-6 Series 110
Variant of the Series 100 built to conform to BCAR (British Civil Air Regulations)
DHC-6 Series 200
Improved version.
DHC-6 Series 300
Twin-engined STOL utility transport aircraft, powered by two 620 shp (462 kW) Pratt & Whitney Canada PT6A-27 turboprop engines.
DHC-6 Series 300M
Multi-role military transport aircraft. Two of these were produced as 'proof of concept' demonstrators
DHC-6 Series 310
Variant of the Series 300 built to conform to BCAR (British Civil Air Regulations)
DHC-6 Series 320
Variant of the Series 300 built to conform to Australian Civil Air Regulations
DHC-6 Series 300M
Military version.
DHC-6 Series 300S
Six demonstrator aircraft fitted with 11 seats, wing spoilers and an anti-skid braking system.
DHC-6 Series 400
Originally scheduled for customer deliveries mid-2009, but now second quarter 2010,[3] powered by two Pratt & Whitney Canada PT6A-34 or optional PT6A-35 Hot & High Performance engines, and available on standard landing gear, straight floats, amphibious floats, skis, wheel skis, or intermediate flotation (Tundra) landing gear.
CC-138
Twin-engined STOL utility transport, search and rescue aircraft for the Canadian Forces.
UV-18A
Twin-engined STOL utility transport aircraft for the U.S. Army Alaska National Guard. Six built. It has been replaced by the C-23 Sherpa in US Army service.
UV-18B
Parachute training aircraft for the United States Air Force Academy. The United States Air Force Academy's 94th Flying Training Squadron maintains three[20] UV-18s in its inventory as freefall parachuting training aircraft,[21] and by the Academy Parachute Team, the Wings of Blue, for year-round parachuting operations.

Operators/Former Operators

Civil operators

Loganair Twin Otter in British Airways Livery at Barra Airport
 Canada

Military operators

Twin Otter taking off from a gravel airstrip near Sila Lodge at Wager Bay (Ukkusiksalik National Park, Nunavut, Canada)
 Afghanistan
 Argentina
 Australia
 Benin
 Canada
 Chile
 Colombia
 Dominican Republic
 Ecuador
 Ethiopia
 France
 Haiti
 Jamaica
 Malaysia
 Nepal
 Netherlands Antilles (Sint Maarten)
 Norway (Retired from active service)
 Panama
 Philippines

Philippine Air Force

 Paraguay
  • Paraguayan Air Force
 Peru
 Sudan
 Switzerland
 Peru
 Uganda
 United States

Notable accidents and incidents

Specifications (300 series)

Orthographically projected diagram of the de Havilland Canada DHC-6 Twin Otter.
Orthographically projected diagram of the de Havilland Canada DHC-6 Twin Otter.

General characteristics

  • Crew: Minimum one, commonly two. (A flight attendant must be on board if there are more than 19 passengers)
  • Capacity: 19 or 20 passengers

Performance

See also

Related development

Aircraft of comparable role, configuration, and era

References

Notes
  1. ^ Viking Acquires De Havilland Type Certificates February 24, 2006.
  2. ^ Viking restarts Twin Otter production April2, 2007.
  3. ^ a b c Sarsfield, Kate (February 3, 2010). "Viking Twin Otter Series 400 certification approaches". Flightglobal. Retrieved February 3, 2010.
  4. ^ a b c d e f News releases: Viking Air
  5. ^ Twin Otter - Zimex Aviation
  6. ^ Updated Twin Otter Takes Off October 16, 2008.
  7. ^ New Country Opens up for DHC-6 Twin Otter Series 400 July 24, 2008. afhra.af.mil
  8. ^ Viking Lands Three Orders for New Twin Otter Series 400 Aircraft from U.S. Army March 18, 2008.
  9. ^ NSF PR 01-29 — Civilian Aircraft to Evacuate South Pole Patient
  10. ^ 2001—Doctor Evacuated from the South Pole
  11. ^ "Pilot says pole flight wasn't his most challenging." usatoday.com.
  12. ^ Pilots return after historic South Pole rescue
  13. ^ "Aircraft in Antarctica: British Antarctic Survey." antarctica.ac.uk. Retrieved: December 31, 2007.
  14. ^ "Skydive Orange Capacity and Altitude." skydiveorange.com. Retrieved: October 19, 2008.
  15. ^ Viking Twin Otter Series 400 Achieves Power On September 25, 2008
  16. ^ Twin Otter Shakes Its Wings Over Victoria Skies October 2, 2008
  17. ^ First Flight For New Twin Otter A "Boring" Success October 1, 2008.
  18. ^ Revived Twin Otter Makes First Flight October 8, 2008.
  19. ^ Twin Otter Series 400 completes maiden sortie
  20. ^ "94 FTS Fact Sheet." afhra.af.mil. Retrieved: August 12, 2009.
  21. ^ [1] globalsecurity.org. Retrieved: August 12, 2009.
  22. ^ "Bangs/Prangs." British Aviation Review, British Aviation Research Group. Volume 29, No. 9, September 1981, p. S402.
  23. ^ Prensa: 24 years after the accident Retrieved: March 5, 2005
  24. ^ NTSB: Perris Valley Aviation Services DHC-6 17 February 1994
  25. ^ Aviation Safety: Merpati Nusantara Airlines Flight 6715 Retrieved 15 December 2009
  26. ^ Bnet: Family sues Air Caraibes over crash on St Bathelemy 9 May 2001
  27. ^ CBS News: 20 Thought Dead In Pacific Plane Crash 9 August 2007
  28. ^ Aviation Safety: Accident description: L'Armée de L'Air 742/CB Retrieved 15 December 2009
  29. ^ BBC News retrieved 08 October 2008
  30. ^ Aviation Herald: Merpati DHC6 aircraft impacted mountain 16 October 2009
  31. ^ The Australian: Mixed weather reported before PNG plane crashed 12 August 2009
Bibliography
  • Hotson, Fred W. The de Havilland Canada Story. Toronto: CANAV Books, 1983. ISBN 0-07-549483-3.
  • Rossiter, Sean. Otter & Twin Otter: The Universal Airplanes. Vancouver: Douglas & McIntyre, 1998. ISBN 1-55054-637-6.
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