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Aviation History
1963
1963 - 1660.PDF
470 FLIGHT International, 12 September 1%3 In the Air ... nose-down attitude change with more increase in lift than drag. The landing-configuration stall was a modified version of the clean stall with artincial warning at 80 m.p.h., aerodynamic buzz at 70 and a rough nose-down pitch and g break at 65. The aircraft continued to hold height at a very reasonable nose-up attitude right up to the stall, but broke with the stick some way off the back Stop. When I held the stick in that position, the Twin "went down stairs" in short jerks without dropping a wing. When 1 brought the stick progressively back to the stop, the little swoops became more rapid and pronounced until the Twin broke completely and dropped its left wing again. Just above the stall I needed almost full left rudder to hold the nose straight against the lack of engine torque. Altogether the stalls were firm when they came, but excellent control remained till the last second, the aircraft did not sink before stalling and the aerodynamic warning was unmistakeable. This augured well for landing characteristics, indicating ability to make glide approaches unusually close to stalling speed. In fact the book gives a glide approach speed for short-field per formance of 83 m.p.h., keeping the Twin Comanche in the real light aircraft class, where it should be for its potential owners. Full aft trim with everything down and power off, at a probably a forward e.g., settled a speed of 85 m.p.h. at which there was very good aileron control and what felt like an ample g margin for rounding-out. I then applied 25in at 2,400 r.p.m. and was surprised at the mildness of the nose-up trim change. I could hold it easily with slight pressure from one hand. Some aeroplanes become semi-aerobatic under these conditions. And so to single-engined checks. First, I stabilized 140 m.p.h. with 20in and 2,400 r.p.m. at 2,300ft and throttled back the left engine with hands off the controls. There was a fair lurch, but not much more than in an Aztec at 75 per cent power—and the Aztec is particularly good on one engine. I then feathered the propeller, with immediate reduction of asymmetric forces. It went on turning for some seconds at this airspeed. I increased to 26in and 2,500 r.p.m. on the right engine and the speed settled at 135 m.p.h. with all forces relieved by three-quarters of the available rudder trim. The trimmer knob and indicator were, incidentally, rather stiff and distant, but the rudder forces always remained so light that lack of trimmer effectiveness was really no handicap. With light rudder forces, the importance of the trimmer is enor mously reduced. The Twin held height very easily at less than full power and was perfectly comfortable to fly. Increasing again to 2,700 r.p.m. and full throttle at 27in, the trimmer just held the rudder load. Slowing down, I found that almost full rudder was needed to hold straight at the recommended best single-engined rate of climb speed of 105 m.p.h.: below this, aileron was increasingly required to back up the rudder. Control forces were very light. At full power and 90 m.p.h. I was forced into cloud and made a 180° turn against the "good" engine on instruments. Firm control application was necessary to keep the turn going, but I was easily able to accelerate to 135 m.p.h. again without losing height. Next, I restarted the engine and tried to simulate an engine cut immediately after take-off—with lee-way for my unfamiliarity and Lord Kildare's nerves. I set up a full-power climb with flaps up and gear down at 88 m.p.h., 8 m.p.h. above minimum control speed, which gave a steep angle of climb. As we passed 2,500ft I throttled back the left engine, corrected hard for yaw and roll, selected gear up, started to increase speed towards 105 m.p.h. and then feathered the left propeller. At first, I needed a lot of aileron, but the relief from feathering was most marked and virtually instantaneous. I had taken Piper's claim that the propeller feathered in 3sec with a pinch of salt, particularly after fairly prolonged wind- milling when I feathered at 140 m.p.h. At the higher speeds the propeller will start windmilling slowly even after it has feathered and stopped, but at below 100 m.p.h. it really does stop almost instantly and the reduction of drag takes one quite by surprise at first. Conversely, restarting using the starter motor to get the propeller windmilling, is much more positive at 120 m.p.h. At 105 m.p.h. on the right engine, the Twin climbed quite positively and I gained another 1,000ft without any difficulty. In this instance, too, I did not bother to apply rudder trim at all and found no strain in holding the asymmetric force for several minutes. Because of the need for considerable anti-torque rudder in the climb and at minimum glide speeds, adverse yaw when reversing turns and because aileron was necessary to back up rudder at below 100 m.p.h. on one engine, I formed the opinion that the Twin Comanche could well have more powerful rudder and perhaps a better fin, but I have not yet found any support for this opinion amongst the instructors and airline pilots who have also flown the aircraft. I did find good damping of roll-induced yaw at low speeds with the controls free and the Twin Comanche undoubtedly performed well on one engine and was quite simple to handle under adverse conditions. It was vastly easier and more potent on one engine than a lightly loaded Gipsy Major Gemini. One need say no more. As a final check I throttled and then feathered the left engine during a full-power, clean climb at 100 m.p.h., a rather more likely after-take-off engine trouble case. There were no problems at all. The propeller again stopped instantly and the speed went easily beyond the single-engined climb speed before I had got around to chasing it. I left the gills closed all the time, but cylinder head temperature came nowhere near the top limit. By the time I had finished darting about on one engine, it was high time to return the aircraft to C.S.E. Aviation and I made only one landing, on the grass at Kidlington. Circuit and approach were plain sailing and the final descent at 90 m.p.h. with everything down and a trickle of power went easily despite a 90° cross-wind of at least lOkt. I throttled back high, at about 30ft, finding a progressive, manageable trim change. When I let the Twin down on to the grass the nosewheel instantly banged down, but a considerable backward wheel movement served to lift it off again immediately afterwards. Forward engines and rearward main- wheels seem to induce a firm nose-down rotation on touch-down, though there is enough elevator to relieve the load if the wheel is pulled back rapidly. A little practice would help. In addition, any rudder offset induces nosewheel steering angle and, because of the strong interconnection, a turn as soon as the nosewheel contacts the ground. Without a series of landings I cannot really comment on this behaviour. This kind of investigation must always give a slightly dour impression of an aircraft because, when pushing judiciously towards the corners of the handling envelope, one is inevitably looking at the seamy side of an aircraft, although one must know this to get the full measure of it. Though one could find fault with detailed aspects, I must say that the Twin Comanche impressed me enor mously during almost two hours' flying by its crisp, light handling, extremely rapid acceleration even under low power and outstanding quietness. An excellent aeroplane can be recognized in a few minutes, and nothing it does afterwards can erase that first flash of delight on initial acquaintance. Such was my first reaction to the Twin Comanche, and that is my memory of it now. It is outstanding in its field, the biggest step forward for years and a combination of performance, price and economy unique in the light twin field. The gorgeous "tiger shark" nacelle shape is undoubtedly one of the keys to the Twin Comanche's splendid performance
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