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Aviation History
1964
1964 - 1467.PDF
814 FLIGHT International, 14 May 1964 GLIDING 1964 Flying the SZD FOKA . . . to check that the controls can actually be reached and, if necessary, to indulge in a second approximation. The controls come fairly readily to hand for most sizes of pilots, although adjusting the altimeter presents some problems. Apart from the primary controls they are all labelled in the standard Polish fashion, with neat self-explanatory pictures. The harness is not entirely satisfactory, but then nobody seems to have invented a really secure way of stopping a supine pilot from sliding forwards. At this juncture you waggle the controls and find them gratifyingly free from friction except that the ailerons have a springy feel, due to some rather nasty sheet-rubber sealing. Closing the canopy has an air of finality; it just misses scalping you. One's reaction is then of slight alarm: you are a pretty tight fit, and the machine is obviously designed for stalwart chaps who find sandwiches, cigarettes and light liquid refreshment superfluous. There is no room for them. Folding maps will obviously be trying, rather like dealing with a newspaper in a rush-hour tube-train. The for- ward view consists largely of one's feet and the instruments, with the outside world only vaguely visible through the canopy, whose flat angle accentuates any imperfections in the moulding. Also, it has a joint in just the wrong place. The view in directions other than directly forwards is quite good, and the sarcophagous sen- sation is greatly alleviated by the sundry ventilating arrangements. Take-off Tricks After the usual initial routines, you start the take-off run behind a dimly visible tug and immediately become acutely aware of the undercarriage. This seems to be basically designed for its native land where, as Philip Wills once said, you go on gliding until you run aground on a sandy potato field. It consists of a front skid and a wheel so far aft that the machine is resting firmly on the skid with the cockpit empty. Even on Lasham's fair-to-middling surface you get a very rough ride, and your first reaction is to pray that you will get airborne before being beaten senseless on the roof. In fact there are two tricks which go a long way to mitigate this ordeal: (a) get strapped in very tightly and indulge in a Charles Atlas-type exercise of the stomach muscles to keep your head firmly on the headrest, a technique which comes with practice, and (b) hold the stick right back until what is known in polite circles as "rotation speed" comes up. The second piece of advice needs qualification for, unless you do some swift juggling with the stick just after rotation, you are likely to become airborne rather prematurely, mostly propped-up by the tug's slipstream and all set to give a convincing but brief imitation of a winch launch. Again, with very little practice, the technique becomes easy. As the speed increases after take-off, you come to realize that the forward view is better than you thought, although it does pay to fly a bit lower than usual behind the tug. The tow presents no problems, and all the controls are quite light and positive. Off tow, one settles down to a more dignified speed to explore the Foka's characteristics. Fore-and-aft it is quite light. The characteristics vary less than one would expect with changing e.g. position and, despite the low forces, it is always convincingly stable and free from "twitch." The ailerons are reasonably light but not startlingly so, perhaps due to that unfortunate rubber sealing. They heavy-up somewhat at high speeds. The rate of roll is excellent. The rudder is nicely harmonized and, all told, is it a very pleasant glider. The stall is roughly what you would expect: some buffet starts at about 68-70 km/hr and control is lost at about 65 km/hr, usually by a wing dropping in quite a pronounced fashion. If the pilot takes no recovery action, the glider tries to do a spin or a spiral dive, depending on the e.g. position, but recovery is quite easy before such a situation develops. A genuine spin involves quite spectacular sensations: the attitude is steeply nose-down so that you are almost standing upright; the rate of rotation is high—about 2.5 sec per turn, which sounds more impressive when expressed as 24 r.p.m.; the view, moreover, becomes the envy of any Cinerama addict. It is gratifying to record that recovery is straightforward and very prompt. Close-up of Foka during rigging, showing wing mainspar socket As one would expect, sensations of g are noticeably reduced by the reclining attitude and, whilst loops are entirely straightforward, one does have to remember not to pull too hard at entry since much of the usual jowl-drooping sensation is absent. Gliders are essentially devices for using atmospheric energy to fly far, fast, and sometimes high. Ultimately, they are judged by their performance rather than by their masochistic capability. The desig- ner was clearly aiming at a lot of performance under fairly strong thermal conditions, and this he has undoubtedly achieved. The Poles claim to quote genuine measured performances, and there is certainly no reason to disbelieve their stated best glide ratio of 1 ; 32. Many another manufacturer would have thrown out some good round figure like I : 40. With a relatively high wing loading (61b per sq ft) the best speed for circling in thermals is about 80 km/hr. This makes for rather bigger circles than those usual in this country so far, and the Foka tends to get out-climbed by machines such as the Skylark 3 or Olympia 419. But it pays to rush off between thermals at surpris- ingly high speeds (150 km/hr or so), and it is in this phase of flight that the high wing-loading yields gains in reasonably strong conditions. It is not really a machine for an afternoon's dreamy hill-soaring in weak lift, but it is a formidable contender in terms of average cross-country speed. The Poles seem to have achieved the knack of extracting sur- prising amounts of performance even in weak thermals, a technique which our Dart pilots will need to cultivate. When circling in thermals, the poor forward view is not the embarrassment one might suppose, since you are more interested in looking sideways at the opposition in the same thermal. Eventually comes the approach and landing, when it becomes apparent that the Foka really is a fairly hot ship over the hedge. The airbrakes are of the DFS variety, cunningly designed to fit into the thinnish wing. So, despite the fairly high approach speed, the effective brakes and the high skid-friction permit reasonably short arrivals. The brakes have rather more sucking-out tendency than we like on British gliders but, when this feature is appreciated, present no undue difficulty. Because of the small rigging incidence of the wing on the fuselage, it is quite easy to make a tail-down, one-point landing. The glider then flops gently on to the wheel and skid, promptly coming to a grinding halt. As on take-off, it pays to brace one's body to avoid violent contact with the roof. It is during approach and landing that the poor forward visibility becomes rather obtrusive, and one could imagine that in rain it would be quite unpleasant. Judging the hold-off is fairly easy, but it would be difficult to see an unexpected hazard, such as an electric fence, at a late stage in the approach. The cockpit cover slides forwards to open, and therefore has a separate jettison knob for emergency use. One member of the Lasham Test Group thought it might be useful to check the func- tioning of this control, and gave it a smart pull to break the locking wire. It turned out to be very effective indeed: not only did the front of the canopy come off as intended, but an interesting array of little springs, plungers and washers were sprayed over the sur- rounding grass. In brief, the Foka is undoubtedly a trend-setter in terms of good design, low profile drag and high wing-loading. Many pilots would argue that the low-drag aspect has been pursued rather too far, to the detriment of pilot efficiency, but perhaps the above account paints slightly too lurid a picture. Certainly it represents first impressions, but it is also fair to say that one feels increasingly at home on further acquaintance. Other designers have pursued the "pencil" theme even further, to an extent which has caused OSTTV to recommend a minimum cockpit height for the standard class in World Championships. Finally, I believe that later production machines have better canopy and aileron sealing arrangements.
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