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Aviation History
1983
1983 - 0063.PDF
nw>w..-V." Lined up for a formation take-off, the Pik-23 shows some sideview likeness to Valmet's L-70 Miltrainer As we levelled off from the climb only a light stick force showed itself—typical of all trim changes and forces throughout the flight. At 3,000ft a power setting of 2,400 r.p.m. produced a TAS of HOkt, which is not much to write home about on 180 h.p. but presumably results from the fine-pitch propeller used for optimum climb performance in glider-towing trials. Stability proved to be good longi tudinally, a lOkt displacement from the trimmed cruise damping out in under two cycles, and equally positive in yaw while never detracting from crisp handling. The rudder is classically the heaviest of all three controls, and the elevator is a frac tion lighter than the ailerons, which are well-tuned. There is barely a trace of ad verse yaw at all normal deflections and you can roll smartly into a 45° banked turn practically rudder-free. In stalling there was little aerodynamic warning, and the artificial warning light or horn will thus be an asset in glider towing, where you can often be dragged to within a few knots of the stall. The warning came on about 7kt before a light, wings-level break at 42kt in the clean, power-off, lg conditiion. Full flap and half power de layed both these figures by about 7kt. As the flaps go to the fully-down posi tion they cause a light nose-up trim change, and with a limit speed of 108kt you can then descend at quite a phenom- Sfe- FJ IGHT International, 8 January 1983 enal rate, up to more than 2000ft/min at this speed. With an attitude that looked around 45° the view was superb, and closed cowl flaps go a long way towards protecting the cylinder heads. Flaps retracted, I initially set up a con ventional circuit pattern at 2,200 r.p.m., which produced an average 95kt. Since this is well inside the flap speed, there was then no delay in starting a descent on base leg. If that's not enough, the Towmaster can add to it a good sideslip capability by modern standards, with plenty of rudder power to hold the steepest of slipping turns if need be. After that, the landing is very straightforward with a light stick force at the flare and precise control right down to the ground. From a later and more sedate approach at 65kt with full flap, a go-around produced a predictably low stick force and trim change. In handling, the Towmaster is like a breath of fresh air in comparison with many contemporary aeroplanes, and its many good points would almost be wasted as a pure glider tug. It has a lot to offer as a trainer, where 180 h.p. is probably too thirsty by civilian standards and a smaller engine would be needed. It would un doubtedly fly behind a smaller engine, al though some of the sparkling climb per formance would inevitably be lost. And if a stretched three/four-seater could be de veloped without detracting too much from the handling qualities, this really would be a modern, composite, practical design to be reckoned with. If the Towmaster is launched on the light aircraft market, Valmet will have to emphasise additional roles besides glider towing, since the latter is a relatively tiny and particularly cost-conscious segment of light aviation. But with its combination of a modern structure and many attractive qualities, the Pik-23 could well put Finland on the light aircraft map. S3 83
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