1979 deHavilland DHC-6-300 Twin Otter 8Q-MAQ (sn 611) Maldivian Air Taxi Photo taken January 2009 at "Picnic Island" (Republic of Maldives) while waiting for Japanese tourists to finish their lunch after they have done some snorkelling on this miniature island. Photo © Marcel Siegenthaler

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.

1969 Twin Otter DHC-6-200 N901ST (sn 208) CSC Chicagoland Skydiving Center Photo taken Aug. 2010 Hinckley Airport, IL - USA (0C2) Photo © Marcel Siegenthaler

A lineup of four Trans Maldivian Airways TMA - DHC-6 Twin Otter's @ the Male Seaplane Base. Photo taken Aug. 2008 Male International Airport, Republic of Maldives (MLE / VRMM) Photo © Marcel Siegenthaler

De Havilland Canada DHC-6-100 Twin Otter C-FASQ (sn 78) Arctic Sunwest Photo taken May 20, 2007 Whithorse Airport, YT Canada (YXY) Photo © AirplaneMart.com

De Havilland Canada DHC-6-300 Twin Otter 8Q-MAV (sn 732) Maldivian Air Taxi Photo taken October 07, 2008 Air to Air shot somewhere above the Lhaviyani Atoll, Republic of Maldives Photo © Marcel Siegenthaler

DeHavilland Canada DHC-6-100 Twin Otter 940 (sn 24) Fuerza Aerea De Chile / Chile Air Force Photo taken March 30, 2006 Santiago Arturo Merino Benitez (Pudahuel) Airport, Chile (SCL / SCEL) Photo Copyright & Thanks to Normando Carvalho Jr.

1968 De Havilland Canada DHC-6-200 Twin Otter N181CS (sn 181) Twotter waits for another load of jumpers. Operated by a local skydiving club at Lake Wales Airport. Photo taken April 25, 2007 Lake Walest, FL - USA (X07/KX07) Photo © AirplaneMart.com

de Havilland DHC-6-100 Twin Otter Floatplane 8Q-TMA Trans Maldivian Airways. Photo taken November 07, 2005 Dhuni Kolhu Island, Maldives Photo Copyright & Thanks to Miguel Cláudio

A de Havilland DHC-6 Twin Otter full motion, Level B, flight simulator at FlightSafety Toronto Photo © AirplaneMart.com

Cockpit View Of Maldivian Air Taxi DeHavilland DHC-6-300 Twin Otter 8Q-MAR Photo taken August 11, 2008 Male' International Airport Seaplane Base, Republic of Maldives (MLE) Photo © AirplaneMart.com

DeHavilland DHC-6 Twin Otter Upper Control Panel with Power Levers, Propeller Levers, Fuel Levers, Flap Handles 8Q-MAR Maldivian Air Taxi DeHavilland DHC-6-300 Twin Otter Photo taken August 11, 2008 Male' International Airport Seaplane Base, Republic of Maldives (MLE) Photo © AirplaneMart.com

DeHavilland DHC-6 Twin Otter Engine Pratt & Whitney PT6A-27 TurboProp Power Plant 8Q-MAR Maldivian Air Taxi DeHavilland DHC-6-300 Twin Otter Photo taken August 11, 2008 Male' International Airport Seaplane Base, Republic of Maldives (MLE) Photo © AirplaneMart.com

Design and development

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
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. 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. 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. Zimex Aviation of Switzerland will receive the first aircraft.

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

Announced orders
- Air Moorea (2)
- Air Seychelles (2)
- Loch Ard Otters (6 plus 6 options)
- Montenegro Charter Company (1)
- Maldivian Air Taxi
- Trans Maldivian Airways (5)
- United States Army Parachute Team (3)
- Zimex Aviation (1)

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 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 April 24–25, 2001, two Twin Otters performed the only winter flight to Amundsen-Scott South Pole Station to perform a medical evacuation.

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.

The Twin Otter has been popular with commercial skydiving operations. It is able to carry up to 22 skydivers to over 13,500 ft (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

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 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

- Loganair Twin Otter in British Airways Livery at Barra Airport
- Aerolínea de Antioquía
- Aeronaves Alimentadoras (defunct)
- Aeroperlas
- Aerovías DAP
- Air Antilles Express
- Aircalin
- Airfast Indonesia
- Air Greenland
- Air Iceland
- Air Jamaica Express (defunct)
- Air Kenya
- Airlines PNG
- Air Madagascar
- Air Panama
- Air São Tomé and Príncipe
- AirSea Lines
- Air Serv International
- Air Seychelles
- Air Turks & Caicos
- Air Vanuatu
- Air Wisconsin
- Allegheny Commuter
- Aurigny Air Services (Guernsey, Channel Islands)
- Aviastar Mandiri
- British Antarctic Survey
- Carib Aviation
- Cayman Airways
- China Flying Dragon Aviation
- Continental Express
- CrownAir (San Juan, PR-USA)
- Crown Airways (Falls Creek, PA)
- Dorado Wings
- Eastern Metro Express/Metro Airlines (USVI)
- Frontier Airlines (1950–1986)
- Golden West Airlines
- Grand Canyon Airlines
- Harbourair (Malta)
- Isles of Scilly Skybus
- Kar-Air, Finland
- Loganair operating a franchise from FlyBe
- Maldivian Air Taxi - MAT (8Q-MAQ DHC-6-300 / 8Q-MAV DHC-6-300)
- Malmilento, Finland
- MASWings subsidiary of Malaysia Airlines
- Merpati Nusantara Airlines
- Nature Air
- Nepal Airlines
- Ozark Airlines
- Pakistan International Airlines (aircraft not in operation)
- Presidencia de la República del Paraguay
- Pilgrim Airlines
- Rocky Mountain Airways
- SAM Colombia
- Scenic Airlines
- Seaborne Airlines
- Skytrail Air Safaris
- Solomon Airlines
- Surinam Airways
- Trans Maldivian Airways - TMA (8Q-TMA - DHC-6-100)
- Volcanic Air Safaris
- Yemenia Airlines
- Yeti Airlines
- Widerøe
- Windward Islands Airways

Canada
- Adlair Aviation
- Air Inuit
- Air Labrador
- Arctic Sunwest (C-FASQ - DHC-6-100)
- Provincial Airlines
- Air Tindi
- Kenn Borek Air
- Nakina Air Service
- NorOntair
- North Cariboo Air
- North-Wright Airways (C-FNWL DHC-6-300)
- Transwest Air
- West Coast Air

Military operators

Afghanistan
Argentina
Australia
Benin
Canada - Canadian Forces - CC-138
Chile
Colombia
Dominican Republic
Ecuador
Ethiopia
France - French Air Force, French Army
Haiti
Jamaica
Malaysia
Nepal
Netherlands Antilles (Sint Maarten)
Norway (Retired from active service)
Panama - Panamanian Air Force (until 1988)
Paraguay - Paraguayan Air Force
Peru
Sudan
Switzerland
Uganda
United States - United States Air Force, United States Army, National Oceanic and Atmospheric Administration

Notable accidents and incidents

• On January 18, 1978 a Frontier Airlines DHC-6 crashed during a training flight in Pueblo, Colorado killing all three crew members.
• On November 18, 1978 a DHC-6 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.
• On July 31, 1981 a Panamanian Air Force (FAP-205) DHC-6 exploded during flight, killing all passengers and crew including General Omar Torrijos Herrera.
• On June 14, 1986 a Canadian Forces DHC-6 (cc13807) crashed on Mount Cox in Kananaskis, Alberta during a search and rescue operation, killing 3 military aircrew and 5 civilian spotters.
• On April 12, 1990 Widerøe Flight 839 crashed in the ocean outside Værøy, Norway due to wind, killing all the five people on board. Værøy Airport was closed following the accident.
• On April 22, 1992 a Perris Valley Skydiving DHC-6 lost power at Perris Valley Airport in California, crashing 200 feet past the runway, killing 14 skydivers and two crew on board; six skydivers survived.
• On January 10, 1995 Merpati Nusantara Airlines Flight 6715 went missing in bad weather, and is believed to have crashed into the Java Sea somewhere between Bima and Ruteng, Indonesia. 10 passengers and 4 crew were killed.
• On March 24, 2001 an Air Caraïbes DHC-6 crashed in the mountains near Gustaf III Airport on Saint Barthélemy in the French West Indies, killing 17 passengers, 2 crew and 1 person on the ground.
• On August 9, 2007 Air Moorea Flight 1121 crashed shortly after taking off from Moorea Témaé Airport in French Polynesia; the plane was bound for Tahiti. All 20 occupants, including 19 passengers and one crew member, were killed.
• On May 6, 2007 a French Air Force DHC-6 in support of the Multinational Force and Observers in the Sinai Peninsula crashed, killing one Canadian and eight French peacekeepers.
• On October 8, 2008 a Yeti Airlines DHC-6 impacted a mountaintop shortly before a landing attempt in Nepal near the airport in Lukla; 16 passengers and 3 crew died in the incident.
• On August 2, 2009 Merpati Nusantara Airlines Flight 9760 crashed in Indonesia about 37 kilometres (23 mi) south of Oksibil. All 16 people on board were killed.
• On August 11, 2009 Airlines PNG Flight 4684 crashed whilst en route from Port Moresby to Kokoda in Papua New Guinea, killing all 13 on board.

Specifications (DHC-6-300 series)

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
Maximum speed: 183 knots (210 mph (340 km/h))
Cruise speed: 143 kt (165 mph (266 km/h))
Range: 920 nautical miles (1,050 mi (1,690 km))
Service ceiling: 26,700 ft (8,140 m)
Rate of climb: 1,600 ft/min (8.1 m/s)