The R-985 Powered de Havilland Beaver: Arguably the Best Bush Plane Ever

With a big, nine-cylinder Pratt & Whitney strapped to the front, this 5,100-pound workhorse boasts a useful load of around 2,000 pounds, and it’s built to operate out of short and rough airstrips.

As the de Havilland Beaver departs the ground, the smile will be on the face of the pilot. Every time you lift off, it seems like a miracle that such a big, heavy plane can get off the ground so quickly, even with a heavy load.

By Crista Worthy with Steve Burak

Arguably the best bush plane ever built, the de Havilland Beaver celebrated 70 years in the sky in August 2017. Here in Idaho where most of our friends tool around the backcountry on a weekly basis, it’s always the Beaver that draws the most attention. Seeing one fly by, low and slow up the canyon, as you stand on an airstrip beside the Middle Fork of the Salmon River, is sure to make your day. Harrison Ford owns about a dozen airplanes and has often said that if he could keep only one, it would be the Beaver. With a big, nine-cylinder Pratt & Whitney strapped to the front, this 5,100-pound workhorse boasts a useful load of around 2,000 pounds (exact numbers depend on how it’s configured inside, among other things), and it’s built to operate out of short and rough airstrips. Strap on skis or floats and you have the ultimate adventure airplane.

Officially known as the de Havilland Canada DHC-2 MkI Beaver, the aircraft was meticulously designed as a purpose-built bush airplane capable of carrying heavy loads into confined, and sometimes rough, areas. Conceived and built in Downsview, Ontario, Canada, much of the Beaver’s early flight testing was done on floats.

The Beaver made its initial flight in August 1947, and the first production Beaver was delivered soon thereafter, in early 1948. By the time production ended in 1967, approximately 1,650 Mk.I Beavers has been built, in addition to a single Mk.II prototype with a 500-hp Alvis Leonides engine, and 60 Mk.III turbo Beavers.

History of the de Havilland Beaver

After the close of World War II, de Havilland turned its attention to civilian aviation. They hired famous bush pilot Punch Dickins as their sales director. Dickins solicited suggestions for new aircraft from working pilots and received an overwhelming number of requests for a tough and powerful STOL (short takeoff and landing) aircraft, capable of being flown on wheels, skis, or floats, that could haul large and awkward loads into remote areas. Speed was not a priority, so long at the new airplane would be “faster than a dog sled.”

From Airliners.net

In September of 1946 de Havilland hired five engineers to develop the new aircraft: Phil Garratt, Jaki Jakimiuk, Dick Hiscocks, Fred Buller, and Jim Houston. The team came up with an all-metal design that relied on steel from the engine to the firewall, heavy aluminum truss frames with panels and doors throughout the front seat area, lighter trusses toward the rear, and all monocoque construction aft. Since all de Havilland Canada airplanes were named after animals, the company christened the new model the Beaver, after the hardworking mammal.

The Engine of the de Havilland Beaver

Because de Havilland was then a British-owned company, the airplane was initially designed for a British engine, most likely the inline 330-hp Gipsy. To maintain STOL performance, the wing was huge. But when Pratt & Whitney Canada offered to supply war surplus 450-hp, nine-cylinder radial R-985 Wasp Junior engines at a low price, the DHC-2 got the big wing and a more powerful engine, keys to its exceptional STOL performance for an aircraft that weighs over 5,000 pounds.

In 1949 the U.S. Army began searching for a new utility aircraft and chose the Beaver over the lower-performance Cessna 195. The outbreak of the Korean War led to hundreds of U.S. military orders and was followed by orders from around the globe.

De Havilland adapted the Mk.I to turbine power when it created the Mk.III Beaver, strapping a Pratt & Whitney PT6 up front. The turbine necessitated a number of modifications to the fuselage: the additional horsepower was managed by a larger vertical fin and rudder, while the potential change in CG was mitigated by a 28-inch extension to the fuselage behind the pilot’s seat.

Recent Developments for the de Havilland Beaver

In 1987 the Canadian Engineering Centennial Board named the DHC-2 one of the top ten Canadian engineering achievements of the 20th century.

Viking Air of Victoria, British Columbia, Canada, purchased the remaining tooling and manufactures replacement parts for many early de Havilland aircraft. In 2006, Bombardier Aerospace sold the type certificates for all the original de Havilland designs to Viking, giving it the exclusive right to manufacture new de Havilland Beavers. Using existing airframes only, Viking now sells a remanufactured and rebuilt DHC-2T Turbo Beaver upgraded with a Pratt & Whitney Canada PT6A-34 680-hp turboprop engine, a gross weight increase to 6,000 pounds, and 2,450-pound useful load. Viking also builds its own DHC-6 Series 400 Twin Otter, manufactured from a completely new airframe.

Getting Ready to Fly the de Havilland Beaver

The designers of the de Havilland Beaver could have chosen the inline 330-hp Gipsy engine, but instead went with the huge 450-hp, nine-cylinder Pratt & Whitney R-985 Wasp Junior radial engine. It’s mounted vertically to provide loading flexibility, which is why the Beaver has that big round nose. The large interior console that rises between the pilot and co-pilot’s feet? That’s the 6-gallon engine oil tank. The filler cap sits on the right, beside the co-pilot’s left knee, and can theoretically be filled in flight, although Steve says he hasn’t personally tried that.

The supercharged engine is thirsty, for both oil and fuel. When I asked Steve what his gph fuel burn usually is, he answered, “If you have to ask, you can’t afford it!” (Most burn about 22–28 gph.) Beavers have multiple fuel tanks. Three of them hold 95 gallons in the forward belly (25, 35, and 35 gallons). The nice thing about their location is that you don’t need a ladder to fill them. Some Beavers have tip tanks which add up to another 46 gallons.

The Beaver is not an airplane you just jump into in a big hurry and take off. That radial needs a little TLC to keep you happily aloft for years to come. Any radial is subject to something called hydraulic lock, where the oil pools in lower combustion chambers, especially if the aircraft has been sitting for a long time. Starting that engine might be a bit like trying to run when you’re knee deep in quicksand.

To prevent catastrophe, after ensuring the magnetos aren’t live, you slowly pull the prop through by hand at least 6 blades. Next, you’ll prime five cylinders, engage the starter, count as five blades move by and then switch on the mags. After the five primed cylinders fire, the other four come on line with a cloud of smoke and that unmistakable sound of a Beaver getting ready to fly. It’s not ready yet, though. The prudent pilot will taxi slowly to an appropriate location, if not already there, and always wait until the engine is thoroughly warmed up and oil temperature reaches 140, which can take 10–15 minutes.

Read the rest at Disciples of Flight.

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