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De Havilland Canada DHC-6 Twin Otter

 
Wikipedia: 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
Introduced 1966
Produced 1965–1988
2008–present
Number built 844
Unit cost $2,000,000 USD[1]

The DHC-6 Twin Otter is a 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.

Contents

Design and development

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 enhanced reliability of turboprop power and the enhanced 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.[2] 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.[3] 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 summer 2009.[4] Zimex Aviation of Switzerland will receive the first aircraft.[5]

On September 25, 2008, the Series 400 Technology Demonstrator achieved "power on" status in advance of an official rollout.[6][7] First flight of the Series 400 technical demonstrator, C-FDHT, took place October 1, 2008 at Victoria Airport.[8][9] 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.

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.[10]

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.[13] 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.[14][15][16][17]

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 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.

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[18] (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.

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 
Scheduled for customer deliveries mid-2009, 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[19] UV-18s in its inventory as freefall parachuting training aircraft,[20] 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
Flag of Nepal.svg Nepal
 Netherlands Antilles (Sint Maarten)
 Norway (Retired from active service)
 Panama
 Paraguay
  • Paraguayan Air Force
 Peru
 Sudan
 Switzerland
 Peru
 Uganda
 United States

Notable accidents and incidents

  • On November 18, 1978, a Twin Otter flown to Guyana to rescue Americans from the Jonestown cult was shot up by cultists and abandoned on the Port Kaituma airstrip.
  • On May 21, 1981 an Ecuadorian Air Force DHC-6 crashed into high ground in bad weather with the loss of all 18 on board.[21]
  • On July 31, 1981, a Panamanian Air Force (FAP-205) DHC-6 crashed, killing all passengers and crew including General Omar Torrijos Herrera.[22]
  • On April 12, 1990, a DHC-6 operated by Widerøe, crashed in the ocean outside værøy due to wind, killing all the five people on board, this is known as the Vaeroy accident.
  • On April 22, 1992, at Perris Valley, California, a DHC-6 operated by Perris Valley Aviation, lost power and crashed 200 ft past the runway, killing 14 skydivers and two crew on board, six skydivers survived.
  • 2007 Air Moorea de Havilland Canada DHC-6 Twin Otter crash killed all passengers and crew.
  • In May 2007, a DHC-6 operated by the French Air Force in support of the Multinational Force and Observers in the Sinai crashed, killing one Canadian and eight French peacekeepers.
  • On October 8, 2008, a Yeti Airlines de Havilland Twin Otter impacted a mountaintop shortly before a landing attempt in Nepal near the airport in Lukla; at least 18 people died in the incident.[23]
  • On August 2, 2009, a Merpati Nusantara Airlines DHC-6 crashed in Indonesia. An airborne search team saw the wreckage near Ampisibil village in Bintang Mountains Regency, at a height of 2,850 metres (9,400 ft). The site of the crash is about 37 kilometres (23 mi) south of Oksibil. All 16 people on board were dead.[24]
  • On August 11, 2009, a Twin Otter operated by Airlines PNG crashed whilst en route from Port Moresby to Kokoda in Papua New Guinea, killing all 13 on board.[25] See full article, Airlines PNG Flight CG4684.

Specifications (300 series)

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
  • Length: 51 ft 9 in (15.77 m)
  • Wingspan: 65 ft (19.8 m)
  • Height: 19 ft 6 in (5.9 m)
  • Wing area: 420 ft² (39 m²)
  • Empty weight: between 7,000 lb (3,200 kg) and 8,000 lb (3,628 kg)
  • Max takeoff weight: 12,500 lb (5,670 kg)
  • Powerplant: 2× Pratt & Whitney PT6A-27 turboprop engines, 620 hp - 680 hp (460 kW - 507 kW) each

Performance

See also

Related development

Comparable aircraft

References

Notes
  1. ^ http://www.fas.org/programs/ssp/man/uswpns/air/cargo/uv18a.html
  2. ^ Viking Acquires De Havilland Type Certificates February 24, 2006.
  3. ^ Viking restarts Twin Otter production April2, 2007.
  4. ^ a b c d e f News releases: Viking Air
  5. ^ Twin Otter - Zimex Aviation
  6. ^ Viking Twin Otter Series 400 Achieves Power On September 25, 2008
  7. ^ Twin Otter Shakes Its Wings Over Victoria Skies October 2, 2008
  8. ^ First Flight For New Twin Otter A "Boring" Success October 1, 2008.
  9. ^ Revived Twin Otter Makes First Flight October 8, 2008.
  10. ^ Updated Twin Otter Takes Off October 16, 2008.
  11. ^ New Country Opens up for DHC-6 Twin Otter Series 400 July 24, 2008. afhra.af.mil
  12. ^ Viking Lands Three Orders for New Twin Otter Series 400 Aircraft from U.S. Army March 18, 2008.
  13. ^ NSF PR 01-29 — Civilian Aircraft to Evacuate South Pole Patient
  14. ^ 2001—Doctor Evacuated from the South Pole
  15. ^ "Pilot says pole flight wasn't his most challenging." usatoday.com.
  16. ^ Pilots return after historic South Pole rescue
  17. ^ "Aircraft in Antarctica: British Antarctic Survey." antarctica.ac.uk. Retrieved: December 31, 2007.
  18. ^ "Skydive Orange Capacity and Altitude." skydiveorange.com. Retrieved: October 19, 2008.
  19. ^ "94 FTS Fact Sheet." afhra.af.mil. Retrieved: August 12, 2009.
  20. ^ [1] globalsecurity.org. Retrieved: August 12, 2009.
  21. ^ {"Bangs/Prangs." British Aviation Review, British Aviation Research Group. Volume 29, No. 9, September 1981, p. S402.
  22. ^ "24 years after the accident." Prensa.com. Retrieved: March 5, 2005.
  23. ^ "Yeti Airlines DHC-6 At Lukla Crashed On Runway." avherald.com, October 8, 2008. Retrieved: August 12, 2009.
  24. ^ [2]
  25. ^ "PNG Airlines crash." theaustralian.news.com. Retrieved: August 12, 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.

External links

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