Impressive Three-point Take-off Most Vivid Beaver Flight Feature
By Ronald A. Keith
THE Beaver bushplane was conceived as a specialist, with the accent on quick take-off and climb. Even this aircraft's impressive advance billing, however, did not prepare the writer for its surprising agility in getting off and up. We flew the Canadian-designed product after it had passed all approval tests and just as the first production model of its kind emerged from the de Havilland factory.
The Beaver's outlines began to take shape in November, 1946. It was in response to the overwhelming vote of operators, consulted in a Canada-wide survey of customer preferences, that the designers sketched in the high-lift wing, the ample flaps and the aileron flap arrangement. These features have combined to give exceptional take-off performance.
We found nothing particularly sensational in the Beaver's routine airborne activity. It is pleasantly light on the controls. There is certainly nothing wrong with the inherent stability. It trims to fly hands off with ease.
The cockpit comfort and visibility are all that could be expected in this type. The large side windows give an exceptional sweep of visibility from the rear seats. The cabin noise level is high enough to be bothersome after a period of time.
But these and other noteworthy characteristics are secondary to the Beaver's quite exceptional ability to get into flight in a hurry.
We flew on wheels. There were three of us in the aircraft. The wind was about 10 mph and we were using paved runways.
On our first take-off we advanced the throttle to deliver 36 in. of boost and 2,300 rpm. The Beaver rolled for 10 seconds then simply lifted off from the three-point attitude.
With 80 mph on the clock we were showing 1,000 fpm, increasing to 1,250 fpm as the flaps came up to 15 deg. The angle of climb was most impressive.
Before describing the flight characteristics in further detail, however, let us get somewhat better acquainted with this aircraft on the ground. The simplest way of doing this is to follow through with the cockpit sequence.
The pilot seats are reached by direct entry through necessarily narrow doors on either side. These, of course are in addition to the large cargo doors which are wide enough to roll a gas drum in on its side.
The pilot's seat is adjustable by operation of a small crank between the knees. It slides the seat forward and up or back and down on inclined mounts.
The large and easily-operated toe brakes are hydraulic. The small plunger below the lower left corner of the panel applies the parking brakes.
Starting our inspection of the cockpit at the base of the control column, we find the flap selector on the floor beside the seat. The hydraulic wobble pump is here too. The elevator trim wheel and indication is on the roof directly above this position.
Crossing to the left Wall we find the flap position indicator near the roof just behind the window. Instead of being graduated in degrees, the indicator is marked for four positions: Up; Climb (15 deg.); Take-off (30 deg.); and Landing (45 deg.). The primer is on the floor near the pilot's door.
The instrument panel layout is quite evident from the illustration on the opposite page. The starter and magneto switches are on the small panel just above the parking brake at the lower left.
Above this, at the left of the flight instrument section is the fuel cock with which the front, centre or rear tank can be selected. Above this is the oil dilution switch, with the master switch up near the base of the windscreen.
The flight panel has: air speed indicator, compass, rate of climb, altimeter, directional gyro and turn and bank. There is an aperture directly below this panel where the P-4 type compass can be installed if desired.
Beside this but not visible in the picture is the fire warning light with the guard-protected switch or operating the integral fire-extinguishing apparatus in the engine. There is also a hand-operated fire extinguisher on the floor ahead of the pilot seat.
Butterfly Tension Control
The vertical centre panel is surmounted by three levers. The throttle is centred with the pitch control on the left and the mixture lever on the right. Forward movement gives fine pitch and rich mixture.
Below each of these levers is a butterfly nut for tension control. Immediately below these we find the engine instruments: tachometer, boost; fuel and oil temperature and pressure (on one dial); fuel contents gauges (three on one dial); carburetor mixture temperature; and cylinder head temperature.
The four levers at the base of this central panel are, left to right, carburetor heat; fuel wobble pump; cabin air; and emergency fuel and oil shut-off.
On the right panel we find the electrical switches and the radio controls.
In a series of take-offs from the paved runway, the Beaver justified the enthusiasm encountered in every pilot who has flown the plane to date. The aircraft gets off most quickly from the three-point attitude. If you get the tail up, the take-off is about 30 per cent longer.
The Company test pilots testify that on wheels in zero Wind with full load they can get the Beaver off with a run of only 650 ft. Under similar wind and load conditions, the seaplane version will unstick to clear a 50-ft. obstacle in 1,165 ft.
George Neal, D-H test pilot flew with the writer on this demonstration, reports that he has taken off from the runway in five seconds with a 25 mph wind. He gets off in eight seconds, in 10 seconds with full load and dead calm.
In the climb, the boost normally is reduced to 30 inches and 2,000 rpm. Flaps are decreased to 14 deg. or to zero as desired.
For clearing obstacles, a much steeper angle of ascent can be achieved by climbing at 60 mph. Under these conditions we found the Beaver to be next-of-kin to the helicopter.
At 3,000 ft. we throttled back to 26 inches and 1,700 rpm. in auto. lean mixture. As we trimmed for cruising the ASI settled at 130 mph. The cabin is no sound-proof chamber but otherwise the flying comfort is more than one has any right to anticipate in a bushplane. The control system is well balanced, the feel being light but firm.
The elevator trim control, at roof-1evel between the seats is a wheel type rotating backward for nose-up forward for nose-down. Thus, unlike the crank kind of trim, it functions in the logical plane and direction, ruling out any possibility of confusion in an emergency.
Our only criticism of the cockpit design concerns the rather awkward location of the flap selector lever, on the floor between the seats, and the flap position indicator, above and behind the pilots left shoulder.
If some kind of flap indication could be located on the instrument it would be much better than the present position which diverts the attention, even though momentarily, back over the shoulder while in the traffic circuit.
The Beaver trims easily for hands-off flight. The test pilots advise that this applies to any loading condition within the normal c of g. travel.
Flying with two in front and one in the centre seating position, we find that with the throttle and stick fully back the Beaver refused to stall. With 60 mph on the ASI, we were mushing steadily but the nose did not drop appreciably.
Under the same conditions with 30 deg. Of flap, the ASI showed 50 mph and we were losing 700 fpm altitude but retained aileron control and found no shudder, no tendency to drop either wing or nose.
We were told that the aircraft will only achieve a definite stall when loaded for extreme aft centre of gravity. In this case it drops the nose and sometimes falls off on the right wing.
The landing approach was made at 70 mph with full (45-deg.) flap. Although the nose was well down, our rate of descent with throttle back was only 800 fpm. Side slipping is recommended when required with this aircraft. Because of the considerable change of attitude from the nose-down glide at 70 mph to the landing position, some prefer to approach at 75 or 80 mph, which simplifies the round-out.
The Beaver is exceptionally easy to land. Even when leveled out considerable too high, it simply mushes down to the runway. The unusually wide track (122 in.) and the smooth hydraulic toes to brakes eliminate any difficulties in the landing run or taxiing.
Canadian Aviation, April 1948, p. 28-29, 68, 78