De Havilland Canada DHC-6 Twin Otter

infobox Aircraft
name = DHC-6 Twin Otter
type = utility aircraft
manufacturer = de Havilland Canada / Viking Air - (400 series)

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caption = A West Coast Air Twin Otter floatplane.
designer = Fred Buller and Dick Hiscocks
first flight = 20 May 1965
introduced = 1966
retired =
status =
primary user =
more users =
produced = 1965–1988, 2008-
number built = 844
unit cost =
developed from =
variants with their own articles =

The DHC-6 Twin Otter is a 20-passenger STOL (Short Takeoff and Landing) utility aircraft developed by de Havilland Canada. It has often been called the most successful aircraft program in Canada's history. The aircraft's fixed tricycle undercarriage, STOL abilities and relatively 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

Development of the aircraft began in 1964, with the first flight on 20 May 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 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 engine that was flat-rated to 620 hp 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.

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 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, rated for flight down to −75°C (−103°F), [ [http://www.nsf.gov/od/lpa/news/press/01/pr0129.htm NSF PR 01-29—Civilian Aircraft to Evacuate South Pole Patient] ] are a staple of Antarctic transportation. 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 April 24–25 2001, two Twin Otters performed the only winter flight to Amundsen-Scott South Pole Station to perform a medical evacuation. [ [http://www.70south.com/resources/evacuations/2001-southpole 2001—Doctor Evacuated from the South Pole] ] [ [http://www.usatoday.com/news/science/cold-science/doctor/2001-04-27-pilot.htm Pilot says pole flight wasn't his most challenging] ] [ [http://www.cbc.ca/news/story/2001/05/03/antarctic_bas_010503.html Pilots return after historic South Pole rescue] ] | url = [http://www.antarctica.ac.uk/living_and_working/aircraft_and_vehicles/aircraft/index.php Aircraft in Antarctica: British Antarctic Survey] Retrieved: 31 December 2007.]

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 the British Airways subsidiary airline, Loganair.

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

The Twin Otter has been popular with commercial skydiving operations. It is generally limited to carrying 22 [hauling loads of up to 22 skydivers to over 13,500' [http://www.skydiveorange.com/Otter.htm] ] jumpers (a relatively 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. The cadets affectionately call the aircraft the "'Twotter."

New production

After series production ended, the remaining tooling was purchased by Viking Air of Victoria which manufactures replacement parts for all of the out of production de Havilland Canada aircraft. On 24 February 2006, Viking purchased the type certificates from Bombardier Aerospace for all the out of production de Havilland DHC-1 through DHC-7 aircraft. [ [http://aiabc.com/artman/publish/printer_47.shtml Viking acquires DeHavilland type certificates] Press Release, 24 February 2006.] The ownership of the certificates gives Viking the exclusive right to manufacture new aircraft.

On 17 July 2006, at the Farnborough Air Show, Viking Air announced its intention to offer a "Series 400" Twin Otter. [ [http://www.vikingair.com/content.aspx?id=1742] Press Release 25 September 2008] Restarting the production would be dependent on the ability to realize enough initial orders.

In April 2007, Viking announced that it would restart production of the Twin Otter with a more powerful PT6A-34/35 engine. [ [http://www.flightglobal.com/Articles/2007/04/02/212989/viking-restarts-twin-otter-production.html Viking restarts Twin Otter production] ] At the time, Viking had 27 orders and options in hand. 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 with customer deliveries commencing summer 2009. [http://www.vikingair.com/content.aspx?id=392 News releases: Viking Air] ] The parts are made in Victoria, British Columbia then shipped to Calgary, Alberta for assembly. Zimex Aviation of Switzerland will receive the first aircraft. [ [http://www.zimex.ch/home/fleet/twin-otter.aspx Twin Otter - Zimex Aviation Ltd ] ]

On 25 September 2008, the Series 400 Technology Demonstrator achieved "power on" status in advance of an official rollout. [http://www.vikingair.com/content.aspx?id=1742] [http://www.canada.com/vancouversun/news/business/story.html?id=0b77b24c-42d4-45b4-a3d6-cf36ba3fdda9] First flight of the Series 400 technical demonstrator, C-FDHT, took place 1 October 2008 at Victoria Airport.Fact|date=October 2008 The next day, the aircraft departed Victoria for a ferry flight to Orlando, Florida, site of the 2008 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.Fact|date=October 2008

Orders

*Air Moorea (2)
*Air Seychelles (2}
*Loch Ard Otters (6 plus 6 options)
*Montenegro Charter Company (1) [ [http://www.aviation.ca/content/view/5968/1/ New Country Opens up for DHC-6 Twin Otter Series 400 ] ]
*Trans Maldivian Airways (5)
*United States Army Parachute Team (3) [ [http://www.vikingair.com/content.aspx?id=304 Viking Lands Three Orders for New Twin Otter Series 400 Aircraft from U.S. Army] ]
*Zimex Aviation (1)

Variants

;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. [http://www.vikingair.com/content.aspx?id=1742] ;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 98th Flying Training Squadron maintains threeFact|date=September 2007 UV-18s in its inventory as freefall parachuting training aircraft, and by the Academy Parachute Team, the Wings of Blue, for year-round parachuting operations.

Operators/Former Operators

Civil operators

*Air Antilles Express
*Adlair Aviation
*Aerolinea de Antioquia (ADA)
*Aircalin
*Airfast Indonesia
*Air Greenland
*Air Iceland
*Air Kenya
*Air Labrador
*Air Madagascar
*Aeroperlas
*Aerovias DAP
*Air Panama
*Air São Tomé and Príncipe
*AirSea Lines
*Air Seychelles
*Air Turks & Caicos
*Air Vanuatu
*Aviastar Mandiri
*British Antarctic Survey
*Carib Aviation
*Cayman Airways
*China Flying Dragon Aviation
*CrownAir (San Juan, PR-USA)
*Crown Airways (Falls Creek, PA)
*Dorado Wings
*Eastern Metro Express/Metro Airlines (USVI)
*Grand Canyon Airlines
*Isles of Scilly Skybus
*Kar-Air, Finland
*Kenn Borek Air
*Loganair operating a franchise from British Airways
*Maldivian Air Taxi
*Malmilento, Finland
*MASWings subsidiary of Malaysia Airlines
*Merpati Nusantara Airlines
*Nature Air
*Nepal Airlines
*NorOntair
*North-Wright Airways
*Pilgrim Airlines
*Scenic Airlines
*Seaborne Airlines
*Solomon Airlines
*Trans Maldivian Airways
*Transwest Air
*Yemenia Airlines
*Yeti Airlines
*West Coast Air
*Widerøe
*Windward Islands Airways

Military operators

; AFG; ARG; AUS; BEN ; CAN
* Canadian Forces - CC-138; CHL ; COL; DOM; ECU; ETH ; FRA
* French Air Force
* French Army; HTI; JAM; MAS; NPL; ANT (Sint Maarten); NOR (Retired from active service); PAN
*Panamanian Air Force (until 1988); PRY; PER; SDN; SUI; PER; UGA; USA
* United States Air Force
* United States Army

Notable accidents and incidents

* In, 1981, a Panamanian Air Force (FAP-205) DHC-6 crashed, killing all passengers and crew including General Omar Torrijos.Fact|date=October 2008
* 2007 Air Moorea de Havilland Canada DHC-6 Twin Otter crash killed all passengers and crew.
* On 8 October 2008, a 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. [http://www.avherald.com/h?article=40df1dd9&opt=0]

pecifications (300 series)

aircraft specifications
plane or copter?= plane
jet or prop?= prop
ref=
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 main= 51 ft 9 in
length alt= 15.77 m
span main= 65 ft
span alt= 19.8 m
height main= 19 ft 6 in
height alt= 5.9 m
area main= 420 ft²
area alt= 39 m²
airfoil=
empty weight main= between 7,000 lb (3,363 kg) and 8,000 lb
empty weight alt= 3,628 kg
loaded weight main=
loaded weight alt=
useful load main=
useful load alt=
max takeoff weight main= 12,500 lb
max takeoff weight alt= 5,670 kg
more general=
engine (prop)= Pratt & Whitney PT6A-27
type of prop=turboprop engines
number of props=2
power main= 620 hp - 680 hp
power alt= 460 kW - 507 kW
power original=
max speed main= 183 knots
max speed alt= 210 mph, 338 km/h
cruise speed main= 143 kt
cruise speed alt= 165 mph 265 km/h
never exceed speed main=
never exceed speed alt=
stall speed main=
stall speed alt=
range main= 920 nautical miles
range alt= 1,050 mi, 1,705 km
ceiling main=26,700 ft
ceiling alt= 8,140 m
climb rate main= 1600 ft/min
climb rate alt= 8.1 m/s
loading main=
loading alt=
thrust/weight=
power/mass main=
power/mass alt=
more performance=
armament=
avionics=

ee also

aircontent
related=
* de Havilland Canada DHC-3 Otter
* de Havilland Canada Dash 7
similar aircraft=
* Antonov An-2
* Antonov An-28
* Britten-Norman Islander
* Britten-Norman Trislander
* Fairchild Dornier 228
* GAF Nomad
* Harbin Y-12
* IAI Arava
* LET L-410
* Shorts SC.7 Skyvan
lists=
see also=

References

Notes

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

* [http://www.vikingair.com Viking Air]
* [http://www.bush-planes.com Bush planes]
* [http://media.libsyn.com/media/airspeed/AirspeedListenOtter.mp3 Ambient cabin audio of a skydiver load in a Twin Otter to 15,000 feet and back again]
* [http://media.libsyn.com/media/airspeed/AirspeedOtter2.mp3 Cockpit intercom audio of a skydiver load in a Twin Otter, including demonstration of flight characteristics]