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Aviation History
1960
1960 - 1307.PDF
FLIGHT, 12 August 1960 217 Outstanding in the standard class were the Polish Foka (upper photo araph) which attained consistently high daily placings, and the Standard Austria, this year's winner of the OSTIV prize armrests. These side-rests also accommodate minor controls.1 The aircraft carries no airbrakes in the wing, but depends instead on a "one-shot" parachute which can be extended orjettisoned. This seems satisfactory for Polish potato-fields, mar- ginal for German beetroot-fields, and probably pretty useless forEnglish cabbage-patches. The cockpit canopy did not appear to be very clever—the angleof sight is too flat for good visibility, and an optical flat is moulded in to improve the situation. The cover slides forward about 3inand hinges up at the front. Space for instruments, which are fitted in a pedestal between the pilots' shins, seems ratherrestricted. Two rather curious instruments were observed; one was either an artificial horizon working only in roll or (moreprobably) a turn-and-slip with presentation turned through 90°; the other was a thermal-detector ammeter. The thermal detector,employing a removable element at each wingtip, was said to measure the temperature gradient across the span. The swept fin and rudder represented basically good modernstyling, with the aft location of the tailplane giving a long moment-arm in addition. The sweep also increases the momentarm of the fin and rudder. Rather a gimmick, but an elegant one. The wing has a long, parallel centre-section with flaps, andshort, tapered outer panels with ailerons. Rigging appeared to be fairly easy, but was usually carried out rather gently. The claimedL/D from flight tests was 35. Elfe M (Switzerland). First seen in 1956 at St. Yan, the Elfe was possibly responsible for starting the swept-fin fashion, but now looks less elegant when compared with the 1960 Polish air- craft. The wing now seems less inclined to extreme deflections than at St. Yan. STANDARD CLASS Foka (Poland). Superficially similar to the Zefir, althoughdesigned by a different man. It has been suggested that the similarity is partly due t6 the standardizing effect of the Polishdesign system. The Poles believe the Foka to be a more mature design than Zefir, and claim an L/D ratio of 34 for the standard-class machine. To comply with the standard-class rules the aircraft has awheel, skid and conventional airbrakes. The wheel is well aft and the sailplane sits on its skid even when unladen. The Fokareally behaves like a skidded aircraft with the wheel available for ground-handling.The straight-tapered wing looks more elegant than that of the Zefir. The cockpit cover slides forward. One of the two speci-mens at Butzweiler had an all-moulded Perspex canopy with practically no forward visibility at all. The other example, theone flown in the championships, used a bent conical sheet for the forward section—a great improvement. The cockpit layoutwas similar to that of the Zefir. Both machines had small ground incidence, but this seemed acceptable with the use of powerfultug aircraft. In-flight handling characteristics were reported by British pilots to be good. Standard Austria (Austria). This sailplane was the winner ofthe OSTIV prize. It has an elegant fuselage (but small ground- clearance) and an all-moving vee-tail similar to that of the K-l.Its spinning behaviour is not known. The wing is a rather com- plicated structure in wood. The cockpit is well-finished with aneat canopy which avoids extremely flat angles. Rigging qualities were excellent and the wing-fuselage intersection was good.Fauvette (France). Rather similar in theme to the Austria, but using a sandwich structure, the Fauvette does not seem to haveachieved its anticipated popularity, perhaps because the perform- ance it not as good as hoped. The vee-tail has separate movingsurfaces. Main merit of the design is its simplicity and lightness, resulting in extremely easy ground-handling. Ka-6 (W. Germany). OSTIV prize-winner in 1958, this type is now very popular. It is a good, straightforward aircraft with no particularly unconventional features. Its main merits are good controls (particularly ailerons), good low-speed performance and excellent rigging. The snags appear to be a lack of fore-and-aft stability, and a peculiar bed-spring attached to the stick for trimming. Two examples at Butzweiler had all-moving tails. It was not clear how stick-free stability was provided. Schweizer 1-23H (USA). A conventional Schweizer 1-23G, cropped to 15 metres and fitted with speed-limiting brakes (which seemed amateurish in design) instead of spoilers. Of all-metal construction, the 1-23 is a good "cooking" glider which generally worked well. Forward visibility is poor, however, due to the high front fuselage. CONCLUSIONS 1. Fuselages are becoming more slender to reduce their drag.This is mostly done by eliminating deep bilges and partly by reclining the pilot somewhat (but not necessarily very much).English gliders tend to look like double-decker buses in com- parison. Nicholas Goodhart had some four inches of headroomto spare in the Olympia 419. There seems no reason why we in this country should not make slimmer fuselages, even with littlealteration to the seating. 2. There is an increasing tendency to use long cockpit-coversgiving bad forward visibility. English sailplanes look rather too blunt and bulbous although their visibility is excellent. Acompromise seems indicated. 3. Cockpit interiors in foreign sailplanes are generally muchbetter in finish than the British ones. A spray of cockpit green and some cheap moquette on the cushion is really no longeradequate. 4. Many of the foreign aircraft seemed to have smaller tail-planes than ours. A small tail will give reduced profile drag— but the e.g. is further forward to give adequate static margins,and hence there is an increased down-load on tail in most condi- tions of flight, i.e. more tail-induced drag (and slightly more wing-induced drag). Some calculations on a typical standard-class glider indicate that these effects (dragwise) largely cancel out, andtail size has very little effect on performance. The optimum tail volume coefficient, on this basis, appears to be about 0.5, but theloss in max L/D in going to 0.7 (about Skylark value) is only one per cent. Left, the West German Schleicher Ka-6 achieved five out of the first six standard-class places. Right, the American Schweizer 1-23H
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