Saturday, September 1, 2007
de Havilland Beaver
Sixty years in the sky de Havilland Beaver
The first production Beaver was delivered in early 1948. By the end of production, 1,631 Mk.I Beavers, one Mk.II prototype with an Alvis Leonides 500 hp engine and 60 Mk.III Turbo Beavers had been built. The U.S. military bought 968 Mk.I Beavers as U-20 utility aircraft. For years, Kenmore Air Harbor in Seattle, Wash., has done a lively business converting military Beavers to civilian configuration.
The prototype Beaver illustrates the durability of the type. The first Beaver, CF-FHB, made its first flight in August 1947. After flight-testing was completed, it was refurbished as a demonstrator. In June 1948, the airplane was sold to Central British Columbia Airways, which was in need of working aircraft. FHB then became a working air-taxi airplane. The prototype continued to fly for air-taxi operators until 1980, when it was purchased by a museum and retired. How many manufacturers can claim that a flight-test prototype of one of their aircraft was in continuous, day-to-day commercial service for 32 years?
So, what's it like to fly a Beaver? It can be a lot of fun and a lot of work. This is a big airplane by general aviation standards, with a 5,100-pound gross weight and 450 hp at full lope. The engine is supercharged, and the airplane can have six fuel tanks. These aren't terribly complex airplanes, but they're not that simple either.
Loading a Beaver can be a daunting task—the useful load can be close to 2,000 pounds, even on floats. The shape of the doors on a Beaver initially appears odd. The front doors are narrow, but after flying one, you realize that it's a functional shape. The aft doors were designed to facilitate the loading of 55-gallon barrels, either upright or on their sides. Each spring in Kodiak, I moved fuel from a vessel anchored in an ocean bay to one of our lake camps. Over the course of a few days, I'd move 70 barrels of avgas and Jet A and twenty 100-pound cylinders of propane from the boat into N765—three barrels at a time—then unload at the lake using a ramp. These are working airplanes designed for hard use.
Three fuel tanks occupy the forward belly of the airplane, which simplifies fueling. There's no need for the pilot to climb up on the wings to fuel. Many Beavers have wing tip tanks, but with 95 gallons in the belly tanks (35, 35 and 25 gallons), the tips (another 46 gallons) are rarely used. Fuel management requires planning to maintain center of gravity as fuel is burned.
The first procedure new Beaver pilots learn is engine starting. Radial engines require a few more steps than do opposed engines. Hydraulic lock is a possibility in a radial that hasn't been run for a bit. Oil can pool in the lower combustion chambers, and starting an engine in this case will create havoc.
The morning ritual starts by pulling that big propeller, by hand, through several blades to verify there's no hydraulic lock. Then give it five strokes of prime, engage the starter, count three to five blades, energize the boost coil and switch on the mags. Five cylinders are primed, so they fire first, then the others join in. This is accompanied by a cloud of smoke as the engine clears itself in preparation for the day's work. The sound of a radial engine coming to life has been known to bring tears to the eye of hardcore biker types. It's a sweet sound indeed.
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