de Havilland Canada DHC-3 Otter
Single-engine, high-wing, short take-off and landing (STOL) aircraft, Canada

Archive Photos ¹

de Havilland Canada DHC-3 Otter (CF-ODU) on display (9/16/2003) at the Canadian Bushplane Heritage Centre, Sault Ste. Marie, Ontario, Canada (Photos by John Shupek)

Overview ²

• de Havilland Canada DHC-3 Otter
• Role: STOL utility transport
• Manufacturer: de Havilland Canada
• First flight: 12 December 1951
• Introduction: 1953
• Status: Active
• Produced: 1951-1967
• Number built: 466
• Unit cost: $136,800
• Developed from: DHC-2 Beaver
• Developed into: DHC-6 Twin Otter

The de Havilland Canada DHC-3 Otter is a Single-engine, high-wing, propeller-driven, short take-off and landing (STOL) aircraft developed by de Havilland Canada. It was conceived to be capable of performing the same roles as the earlier and highly successful Beaver, including as a bush plane, but is overall a larger aircraft.

Design and Development ²

The rugged Single-engine, high-wing, propeller-driven DHC-3 Otter was conceived in January 1951 by de Havilland Canada as a larger, more powerful version of its highly successful DHC-2 Beaver STOL utility transport. Dubbed the King Beaver during design, it would be the veritable one-ton truck to the Beaver’s half-ton role.

The Otter received Canadian certification in November 1952 and entered production shortly thereafter. Using the same overall configuration as the Beaver, the new, much heavier design incorporated a longer fuselage, greater-span wing, and cruciform tail. Seating in the main cabin expanded from six to 10 or 11. Power was supplied by a 450-kW (600 hp) Pratt & Whitney R-1340 geared radial. The version used in the Otter was geared for lower propeller revolutions and consequently lower airspeed. The electrical system was 28 volts D.C.

Like the Beaver, the Otter can be fitted with skis or floats. The Otter served as the basis for the very successful Twin Otter, which features two wing-mounted Pratt & Whitney Canada PT6 turboprops. A total of 466 Otters were manufactured.

Operational Use ²

The DHC-3/CC-123/CSR-123 Otter was used until 1980 by the Royal Canadian Air Force and its successor, the Air Command of the Canadian Forces. It was used in Search and Rescue, as the CSR denotes Canadian Search (and) Rescue (type 123) and as a light utility transport, CC denoting Canadian Cargo. During the Suez Crisis, the Canadian government decided to provide assistance to the United Nations Emergency Force and the Royal Canadian Navy carrier HMCS Magnificent carried 4 Otters from Halifax to Port Said in Egypt early in 1957, with all four flying off unassisted while the ship was at anchor. This was the only occasion when RCAF fixed wing aircraft operated from a Canadian warship. It was also operated on EDO floats on water and skis for winter operations on snow. The EDO floats also had wheels for use on runways (amphibious). It was used as army support dropping supplies by parachute, and also non-parachute low-speed, low-altitude air drops, to support the Canadian Army on maneuvers. In the end it was operated by the Primary Air Reserve in Montreal, Toronto, Edmonton and Winnipeg, with approximately 10 aircraft at each base, as well as by the RSU (Regular (Forces) Support Units) at those bases. It was usually flown with a single pilot (Commissioned Officer) in the left seat and a Technical Air Crewman (NCO) in the right seat. The Kiowa helicopter replaced it in Air Reserve squadrons.

Although the Otter found ready acceptance in bush airlines, as in a similar scenario to the DHC-2 Beaver, the United States Army soon became the largest operator of the aircraft (184 delivered as the U-1A Otter). Other military users included Australia, Canada, and India, but the primary role of the aircraft as a rugged bush plane continues to this day.

An Otter crossed the South Pole in 1957 (see Commonwealth Trans-Antarctic Expedition). The Otter is also popular in the skydiving community and can be found in many dropzones throughout the world.

Otters were used by Qantas, from 1958 to 1960 in Papua New Guinea. The Qantas aircraft were then transferred to Trans Australian Airlines (TAA) a major Australian domestic airline which operated the Otters in Papua New Guinea until 1966 when they were withdrawn from use. TAA was merged with Qantas in 1990.

Modifications ²

The most extensively modified Otter was RCAF Otter 3682. After initial service as a standard Search and Rescue aircraft it was used to explore the aerodynamic aspects of STOL. In 1958 it was fitted with flaps so outsized that, with their 45 degree droop, it became known as the Batwing Otter. In addition, its tail-wheel undercarriage was replaced with a high energy- absorption 4-wheel arrangement and a very high vertical tail. The next modification replaced the flaps with fully retractable flaps suitable for cruising flight and high drag was obtained with reverse thrust from a J85 turbojet installed in the fuselage behind the cockpit. The third configuration looked a lot like the future Twin Otter and was the first twin-PT6 fixed-wing installation to fly in May 1963 (A twin PT6-engined helicopter, the Kaman K-1125, had flown in April 1963). The piston engine in the nose was replaced with wing-mounted engines to blow over the flaps.

Stolairus Aviation of Kelowna, BC, has developed several modifications for the DHC-3 including a STOL Kit, which modifies the wing with a contoured leading edge and drooped wingtips for increased performance. Stolairus has also developed a 400 lb upgross kit which increases the gross weight of the DHC-3 to 8,367 lbs on floats.

Some aircraft were converted to turbine power using a PT6A, Walter 601 (manufactured in the Czech Republic), or Garrett/Honeywell TPE331-10, by Texas Turbine Conversions. The Walter M601E-11 Turbine Engine conversion is manufactured and installed by Stolairus Aviation.

A Polish Pezetel radial engine has also been fitted. Re-engined aircraft have been offered since the 1980s by Airtech Canada as the DHC-3/1000 using current-production 1,000 hp (745 kW) PZL ASz-62 IR radials.

Variants ²

• DHC-3 Otter: Single-engine STOL utility transport aircraft.
• CSR-123 Otter: STOL utility transport aircraft for the Royal Canadian Air Force.
• YU-1 Otter: Six test and evaluation aircraft for the U.S. Army.
• U-1A Otter: STOL utility transport aircraft for the US Army.
• UC-1 Otter: STOL utility transport aircraft for the United States Navy. Later redesignated U-1B Otter in 1962.
• DHC-3T Turbo-Otter: Otters fitted with either Pratt & Whitney Canada PT6A-27 or Pratt & Whitney Canada PT6A-34 turboprop engine.
• Airtech Canada DHC-3/1000 Otter: Conversions powered by PZL Kalisz ASz-62IR engines.
• Texas Turbines Super Otter: Turbine conversion powered by a 900 shp (671 kW) Garret TPE331 turboprop engine

Operators ²

Military Operators

• Argentina: Argentine Air Force: Former operator.
• Australia: Royal Australian Air Force: Two Otters (RAAF serial A100-1 and 2) were in service with the RAAF from 1961 to 1967. The aircraft were used for passenger and freight transport duties at the Weapons Research Establishment, Woomera, South Australia. No. 1 Air Trials Unit.
• Bangladesh: Bangladesh Air Force: Former operator.
• Burma: Burma Air Force.
• Canada: Royal Canadian Air Force.
• Chile: Chilean Air Force.
• Costa Rica: Air Surveillance Service.
• Ethiopia: Ethiopian Air Force.
• Ghana: Ghana Air Force.
• India: Indian Air Force.
• Indonesia: Indonesian Air Force.
• Khmer Republic: Khmer Air Force: Former operator.
• New Zealand: Royal New Zealand Air Force.
• Nicaragua: Nicaraguan Air Force.
• Nigeria:
• Norway: Royal Norwegian Air Force.
• Panama: Panamanian Public Forces.
• Paraguay: Paraguayan Air Force: One DHC-3 donated by Argentina.
• Philippines:
• Tanzania: Tanzanian Air Force.
• United Kingdom: Royal Air Force.
• United States: United States Air Force, United States Army.

Civil Operators

• Australia: Qantas, Trans Australia Airlines.
• Canada: Royal Canadian Mounted Police, Lamb Air, Harbour Air, Osprey Wings Ltd., Provincial Airlines, Air Saguenay, Vancouver Island Air, Bearskin Airlines (formerly).
• Philippines: Philippine Airlines (formerly).
• United States: Talkeetna Air Taxi, Kenmore Air, Northwest Seaplanes.
• Fiji: Pacific Island Air.
• New Zealand: Volcanic Air (Rotorua).

de Havilland Canada DHC-3 Otter Specifications ³

Type

• Single-engine nine/eleven-passenger General Utility Transport.

Wings

• High-wing braced monoplane.
• D.H. high-lift wing section.
• Aspect ratio: 8.97.
• Dihedral: 2°.
• All-metal structure.
• Single bracing strut on each side.
• Slotted insert ailerons.
• Double slotted flaps.
• Ailerons and flaps all-metal.
• Total aileron area: 26.3 ft² (2.44 m²).
• Total area of flaps: 98 ft² (9.10 m²).
• Gross swing area: 375 ft² (34.84 m²).

Fuselage

• Of conventional all-metal structure.

Tail Unit

• Cantilever monoplane type with tail plane halfway up fin which is integral with fuselage.
• All-metal structure.
• Total vertical areas: 60.2 ft² (5.6 m²).
• Total horizontal area: 84.0 ft² (7.8 m²).
• Span of tail: 21 ft 2 in (6.46 m).

Landing Gear

• Interchangeable wheels, floats or skis.
• Wheel has D.H. rubber-in-compression springing.
• Goodyear wheels and brakes.
• Track: 11 ft 2 in (3.42 m).
• Wheels interchangeable with D.H. skis or twin Edo 7170 all-metal single-step floats.
• Float base (C/L of floats): 10 ft 6 in (3.20 m).
• A combination wheel-ski landing-gear designed and manufactured by D.H. is available.
• The change from wheels to skis or vice versa is accomplished from the cockpit by hydraulic pump.

Power Plant

• One 600 hp Pratt & Whitney R-1340-S1H1-G or S3H1-G radial air-cooled engine driving a 3-blade Hamilton Standard Hydromatic airscrew 11 ft (3.35 m) diameter.
• Special exhaust system with four augmenter stacks.
• In these stacks exhaust gases produce suction strong enough to pull cooling air through engine and from behind engine accessories compartment while at the same time providing measurable amounts of thrust in cruising flight.
• Engine is effectively cooled during steep climbs when forward air speed is low and engine output near its maximum.
• Fuel tanks under cabin floor.
• Capacities: Front 61 Imp. gallons (230 L), middle (two cells) 85 Imp. gallons (386 L), rear 42 Imp. gallons (190 L).
• Total internal fuel capacity: 170 Imp. gallons (830 L).
• Oil capacity: 9 Imp. gallons (41 L).
• Oil dilution system.
• Remote control fire-extinguisher system in engine compartment.

Accommodation

• Pilot’s compartment seats two side-by-side, pilot (port) and co-pilot or passenger.
• Dual rudder pedals and W. type control column with throw-over wheel.
• Door on each side and one in bulkhead to cabin.
• Cabin is 16 ft 5 in (5.0 m) long, 5 ft 2 in (1.58 m) wide and 4 ft 11 in (1.5 m) high.
• Cabin divided by bulkhead into 12 ft 8 in (3.8 m) long main passenger or freight compartment and stowage compartment.
• Volume of main compartment 273 ft³ (7.6 m³), of stowage compartment 38 ft³ (1.06 m³).
• Doors on each side of main compartment 46.5 in (118 cm) wide on port, 30 in (76.2 cm) wide on starboard.
• Reinforced cargo door floor.
• Cargo drop hatch, camera hole or paratrooper exit in floor of stowage compartment.
• Standard seating accommodation: 9 folding seats for passengers in cabin, plus one in cockpit.
• Tenth seat and cabin available as optional extra.
• Alternatively, 6 stretchers and 4 passenger seats or 3 stretchers and 7 passenger seats.
• All seats quickly removable.

Equipment

• A 28-volt electrical system charged by a 50 or 100 amp. generator is provided.
• Navigation lights.
• Controllable-intensity instrument lights.
• A 250-what sealed-beam landing-light in the port wing leading-edge.
• Cabin lights are provided.
• Racks in the stowage compartment give accessible installation to the battery and to the radio and navigation equipment specified by the operator.

Dimensions

• Span: 58 ft 0 in (17.69 m).
• Length (landplane and seaplane): 41 ft 10 in (12.80 m).
• Height (landplane): 12 ft 7 in (3.83 m).
• Height (seaplane): 15 ft 0 in (4.57 m).

Weights

• Weight empty (landplane): 4,094 lbs (1,860 kg).
• Weight empty (seaplane): 4,526 lbs (2,055 kg).
• Weight empty (fixed skis): 4,332 lbs (1,970 kg).
• Weight empty (wheel/ski gear): 4,400 lbs (2,000 kg).
• Weight loaded (landplane): 8,000 lbs (3,630 kg).
• Weight loaded (seaplane): 7,967 lbs (3,613 kg).

Performance (Landplane)

• Maximum true level speed (600 hp): 160 mph (257 km/h) at 5,000 ft (1,525 m).
• True cruising speed (400 hp): 138 mph (222 km/h) at 5,000 ft (1,525 m).
• Rate of climb (600 hp): 850 ft/min (260 m/min).
• Service ceiling (S1H1-G engine): 18,800 ft (5,730 m).
• Service ceiling (S3H1-G engine): 17,400 ft (5,300 m).
• Maximum range (full tanks): 960 miles (1,545 km) at 5,000 ft (1,525 m).
• Maximum endurance: 9.8 hours at 5,000 ft (1,525 m).
• Take-off distance to 50 ft (15.25 m) (no-wind): 1,302 ft (397 m).
• Landing distance from 50 ft (15.25 m): 1,225 ft (374 m).

Performance (Seaplane)

• Maximum true level speed (600 hp): 153 mph (245 km/h) at 5,000 ft (1,525 m).
• True cruising speed (400 hp): 120 mph (207 km/h) at 5,000 ft (1,525 m).
• Rate of climb (600 hp): 750 ft/min (229 m/min).
• Service ceiling (S1H1-G engine): 17,900 ft (5,450 m).
• Service ceiling (S3H1-G engine): 16,400 ft (5,000 m).
• Maximum range (full tanks): 863 miles (1,385 km) at 5,000 ft (1,525 m).
• Maximum endurance: 8.8 hours at 5,000 ft (1,525 m).
• Take-off distance to 50 ft (15.25 m): 1,980 ft (605 m).
• Landing distance from 50 ft (15.25 m): 1,510 ft (460 m).

Performance (Skiplane)

• Maximum true level speed (600 hp): 158 mph (254 km/h) at 5,000 ft (1,525 m).
• True cruising speed (400 hp): 133 mph (214 km/h) at 5,000 ft (1,525 m).
• Rate of climb (600 hp): 800 ft/min (244 m/min).
• Service ceiling (S1H1-G engine): 17,100 ft (5,200 m).
• Service ceiling (S3H1-G engine): 18,600 ft (5,670 m).
• Note: Range and endurance include allowances for 10 minutes warm-up, take-off, climb to 5,000 ft (1,525 m) and fuel for 45 minutes at cruise power in reserve.

References

1. Shupek, John. The Skytamer Photo Archive, photos by John Shupek, (Skytamer.com)
2. Wikipedia, the free encyclopedia. de Havilland Canada DHC-3 Otter
3. Bridgman, Leonard. Jane’s All the Worlds Aircraft 1956-57, London: Jane’s All the World’s Aircraft Publishing Co. Ltd., pgs. 116-117.