Airtest – DHC-2 Beaver Floatplane

De Havilland DHC-2 Beaver Floatplane

Believe me, my young friend, there is nothing – absolutely nothing – half so much worth doing as simply messing about on floats.

Had Kenneth Grahame known about seaplanes when he wrote Wind in the Willows that is what Toad would have said. Despite the performance penalties and useful load restrictions caused by their weight, over the years floats have been fitted to almost every type of single engined lightplane and many twins. Flying off water takes different and rather greater skill to simple ground bound aviation and, while sometimes slightly less practical, it is always immensely rewarding and much more fun.

Since getting my seaplane rating a dozen years ago I have become a complete convert to aquatic aviation. Having sampled many types of floatplane, my favourite of all by far is the De Havilland Canada Beaver.

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De Havilland Canada was formed in Toronto in 1928 to assemble and service the company’s imported British products. In 1937 they started making specially ‘Canadianised’ Tiger Moths in their own right, eventually building 1500 of them. Later in the War they built 1135 Mosquitos before going on to produce 50 or so Fox Moths and then their own indigenous designs after the conflict ceased. Having wanted to begin with a bushplane tailor made for the unique requirements of their own rugged country, they were advised to start on a simpler trainer, so their first product was the DHC-1 Chipmunk. This turned out so popular that production was taken over by the English parent company leaving the ‘colonials’ to resume their original project.

Unlike so many manufacturers who are inclined to say “this is our aircraft, come and get it”, DHC wisely began their design process by polling over 80 bush operators throughout Canada, as well as a few in hotter climes, to see exactly what they wanted. What they did want was a spacious, easy to fly machine that was cheap, long lasting, simple to fix without the benefit of workshop facilities and had a half tonne payload with superlative short field performance.

It took the company less than a year to roll out its prototype DHC-2 and it was a runaway success right from the start. Over a 20 year production run nearly 1700 were eventually built and they have served reliably in 65 countries in every climate and on every continent (including Antarctica). Even today there are hundreds still flying, and at the head of Lake Washington in the Pacific Northwest of the USA, Kenmore Air Harbor rebuilds old airframes to as new standard to meet the unceasing demand for replacements. The high prices these fetch reflects the great value of these superb workhorses.

Because of the hostile environment for which they were built and in which they excel, Beavers are rarely seen by city folk. Yet hundreds of them still soldier on (Beaver away?) in the jungles, mountains, deserts and tundra of the world. The one I flew for this article now lives in Scotland, and I was introduced to it in the middle of a bleak European winter.

Believe me, it is not until you are standing with a bucket of icy water in one hand and a wet sponge in the other, looking four metres up at a grubby Beaver that you start to appreciate just what a big aeroplane it is. Well over nine metres long with a 14.6m span and stressed to 3.5g, it is a tribute to De Havilland Canada engineering skill that at 1600kg including floats the great lump nevertheless weighs little more than a Holden station wagon.

The front fuselage is an aluminium skinned steel tube cage, making its interior easily accessible for inspection and repair, while aft of the cabin the fuselage is of a stressed skin monocoque construction. Behind the rear seats a generous luggage area has hatches in its back wall to stow slim freight up to three metres long. Behind this are a separate smaller locker and the battery tray which slides out of the fuselage side. The 24 volt electrics come from an engine driven 1500 watt generator and can power an optional engine pre-heater. The semi cantilever two spar wing is made for good STOL performance with a NACA 64A high lift section, a high 9.2 aspect ratio and slotted flaps which, with the ailerons, add up to a quarter of the total 23.1m2 wing area. The ailerons droop down to 15° with the flaps to form full span trailing edge high lift devices. The all metal cantilever tail surfaces are supplemented by a triangular ventral fin and arrow shaped tailplane end plates to offset the destabilising effect of the floats.

Our test machine has long Wipline 6000 floats with integral lockers rather than the standard Edo 4930 units. (Float numbers indicate their maximum buoyancy in pounds and since, for safety, each is required to support double its displacement, a pair of ‘six thousands’ will accept a 6000lb/2725kg MTOW aeroplane.) A water rudder on each float is connected by cables to the rudder pedals.

It took us all day to get the months’ accumulation of gooey duck muck and seagull droppings off the airframe, and despite getting soaked lying in cold puddles of grimy water under the floats we never did remove all the khaki slime from their bottoms. But next day we were ready to take advantage of the high spring tide and fly. Manhandling the aeroplane down the slipway on an old flat bed trolley, five of us took just 20 minutes to get the big beast bobbing happily on the briny. Or rather it was bumping and grinding the heels of its expensive floats against the tarmac on a lee shore so we all clambered aboard as quickly as possible.

Rubber boots are advisable, but they were not absolutely necessary even in this exposed situation and we were each able to step onto the back of a float, walk forward along its non-slip top and climb the broad steps on their struts to enter the wide twin cabin doors. The Beaver’s interior is divided into two-seat cockpit and slightly lower 1.22m wide, 1.32m high main cabin in which were a pair of three-seat benches, the middle row having a split folding back for easy access to the rear ones.

Each door has a broad, bulged, bubble window, while the aft cabin walls have oversized fixed panes to give the rear passengers an excellent view. The slightly foreshortened cockpit is a little less sumptuous than the newly furnished cabin. Standard controls are a single wheel on a fixed left side only or ‘throw over’ yoke pivoting fore and aft on a centreline pillar but, as it is partly used for training, G-DHCB has twin control wheels at either end of a Y-shaped structure.

Along the top of the instrument panel are amber oil and fuel low pressure lights and the left to right mechanical flap indicator. Basic flying instruments include an old black and white artificial horizon and a standby compass mounted on the flat windscreens’ central pillar. Below the main array a full width sub-panel carries the rotary fuel selector, (fuel is carried in three underbelly tanks with triple fillers neatly recessed in a panel just behind the door on the left side of the fuselage and accessible from the floats) switches for magnetos, generator, fuel pumps and all the other electrical equipment. Both marine and aeronautical radios are mounted on the right.

The centre of the rounded grey coaming accommodates a high quadrant with man-sized throttle, pitch and mixture levers, each with its own friction knob. Engine and fuel gauges are set below with carb heat, wobble pump and emergency fuel and oil cutoff levers protruding beside the oil filler (which is in the cockpit by the copilot’s left knee so a frozen frontiersman can easily check it and top up). The pilots sit high on adjustable seats for the best panorama and their doors have vertically sliding Perspex windows and integral armrests. Between the front seats are the long pump handle for hydraulically shifting the flaps, their flipover direction selector (forward for down, back for up), and a neat custom made over centre water rudder retraction lever. (Many floatplanes only have a handle on the end of the wire which you have to hook on to some convenient protrusion.)

This Beaver still has its original inertia starter. This uses a comparatively weak electric motor to spin a small flywheel up to high rpm, when the stored energy rotates the engine. Getting the powerplant going with this is a multi-handed trick. You pump up the fuel pressure, prime, and raise the starter switch for 20 seconds to spin up the flywheel. When the whirring reaches peak pitch you flick the switch down to engage, listen for a quickly descending groan, count two blades, switch on the mags and hit the booster coil before the flywheel loses all its impetus.

If you get it right the engine will catch just as it slows almost to a halt and, to the accompaniment of a swirling grey cloud of oily smoke stage right, the hiccupping bass thumping will grow into the irregular, loping, lumpy grumble of a healthy Pratt 985. Except that this engine didn’t throw any smoke. Shooting a quick glance at the oil pressure gauge I raised an enquiring eyebrow. “It’s only done 13 hours”, replied Tony, the owner. So that’s why this Beaver’s belly was so clean!

Of course a seaplane has no brakes so as soon as the engine was going we were off! The 20 litres of oil takes about 10 minutes to warm up to the minimum 40°C, so we used the time taxying around the sheltered bay checking for debris and driftwood while surveying the area. Burbling innocuously around the moorings, buoys, isolated pilings and crazily speeding windsurfers we were rewarded with the occasional whiff of avgas mixed with salt spray and hot oil, as we towered over all the other waterway users except the supertankers.

Once our oil was warm we were able to do the run up at 1750rpm (and about 20kt/37km/h!) Then I turned into wind, selected carb air to cold, raised the water rudders and pumped down takeoff flap. Aiming to the right of a big black baulk of semi-submerged driftwood, I eased the wheel back and gently opened the throttle, revelling in the swelling thunder of the 15 litre Wasp Junior and the surging acceleration as the nose reared under its power. As American hotrodders say about engine capacity: “There just ain’t no substitute for cubes!”

Although they have some handling similarities to tailwheel aircraft, floatplanes are rather different from tricycle landplanes. At the start of takeoff the stick is held fully back so that, as the aircraft accelerates, the floats’ bow waves build up to lift their fronts. The growing waves move aft, further raising the noses of the floats (and so, the aircraft) until a stable maximum pitchup position is reached and the speed stops increasing. This is called the hump phase. The floats’ noses are now lowered onto their bow waves, lifting their tails from the water and minimising drag by running along on their small middle portion, or step. The pitch attitude for this phase is critical, if the nose is over high or low too much of the floats are in the water and their drag will overcome available thrust.

I concentrated on keeping straight (easy) and feeling for the peak noseup pitch signifying we were ready to lift on to the step (more difficult). Perhaps this was because with two full tanks and six people aboard we were just short of the 2310kg max weight, or more likely, because I was trying not to overboost the engine, it had not quite developed its normal 36in and 2300rpm full power, but the long Wiplines seemed to have a much less clearly defined hump phase than others I have flown.

After a while we stopped accelerating. Now we could no longer clearly see where we were going past the raised nose, so I eased the yoke forward to lift us onto the step. The ideal pitch attitude was easy to maintain, being with the top of the cowling just below the horizon, and like this we quickly reached the 50kt (93km/h) lift off speed to part company with the viscous sea and curve easily away. We had run for only a few hundred metres. When empty the heartily throbbing R-985 will heave a Beaver straight up and into the air in as few feet. Pumping the flaps up to climb and retrimming with the dinky roof mounted trim wheels, I reduced power to 30 inches and 2000rpm, subjugating the normal 750ft per minute climb in the cause of good neighbourhood relations.

When I first flew a Beaver its manoeuvrability came as a shock. After all, this is a heavy, man-sized aircraft so one expects he-man control forces. Not a bit of it – I do not know if W J Jakimiuk who was responsible for the Chipmunk’s lovely qualities also contrived the Beaver’s agile handling but I should not be surprised if he did, for it flies like a smaller aeroplane with light forces and a roll rate much better than that long high aspect ratio wing might suggest. Nevertheless it is very stable in all axes, with none of the directional indecisiveness displayed by some floatplanes.

With such a big wing and the drag of all those struts mass balance weights and dangling bits of rope trailing in the slipstream, the Beaver was never meant to be a record breaker. Tony’s normal 95kt (175km/h) cruise speed at 28in and 1750rpm burns a fairly frugal (for this big engine) 80 litres per hour. This speed allows an absolute maximum endurance of five and a half hours, is quite adequate for getting places and ideal for sightseeing and pleasure flying. The view is excellent from all seats although the two passengers in the middle of the benches have to lean from side to side to make the most of it. Higher speeds are possible, up to De Havilland’s quoted maximum of 130kt (240km/h) but at the expense of the horrendous consumption of 130 litres per hour.

The photo session reinforced the Beaver’s manoeuvrability, but did highlight its inertia, even large power changes taking time to have an effect. The detail also invoked a new ‘first’ for me, that of flying formation in gumboots!

Cruising around in a seaplane is all very well but waterwork is always the most fun. Pumping down the flaps requires rather more muscle than retraction. Circuits are normally flown with climb or takeoff flap at 80kt (148km/h), reducing to 70kt (130km/h) with landing flap on final approach. Being seated well ahead of the leading edge it is easy to keep the landing area in sight and the descent angle is simply controlled with the throttle. Retaining a trickle of power through the flare reduces the rate of descent to near zero and the aircraft is gently lowered to the surface in the almost level planing attitude. Once down, gently close the throttle and bring the wheel back to your chest and, rearing its nose, the aeroplane slows in a shower of spray after a surprisingly short distance.

Of course if you want real STOL performance – to get in and out of a small lake or tightly winding river perhaps – this is the machine for it. Using full (48°) flap it glides like an autorotating helicopter with the cowling pointed well down towards the near shore. Touchdown can be made remarkably close to water edge trees provided some speed is kept in hand for a dynamic flare with a burst of power. The nose then has to be hauled well up to break the descent rather than the aeroplane. If you get it right the Beaver stops on a dime (but if you get it wrong, normally yielding water can be awfully hard!)

It is this flexibility and remarkable performance that makes the Beaver so versatile. No wonder there has never been a true replacement!