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Aviation History
1960
1960 - 0653.PDF
653FLIGHT, 13 May 1960 PORTER and PROSPECTOR in the Air Nos 121 and 122 of the Series* I HAVE a feeling that the Swiss-built Pilatus Porter will berated one of the most successful designs of the decade. Thereare already a number of testimonials from a wide variety ofagencies which confirm this opinion and my own experience of the aircraft leaves me in no doubt at all. I saw the prototype atthe Paris Show last year, looking very ugly and chunky. I saw it again at Thruxton in December and flew with it while someair-to-air photographs were taken. Most recently I saw it per- forming in direct comparison with Dornier Do 27 and Prospectorat Hanover and finally had the chance to fly it myself. As I men- tioned in my initial report on Hanover, the Porter beat all theother types in STOL performance in identical wind and ground conditions—and the other types are no chickens. In Flight for January 1 we described the special features of thePorter, noting its large cabin, versatile loading arrangements, excellent construction and general layout. Let me add here thatofficial trials employing ordinary pilots have shown that the air- craft significantly improved on its brochure performance; and itcan operate from Swiss glaciers at heights and in conditions which stop the Piper Super Cubs. Its permissible e.g. travel is from10 to 36 per cent of s.m.c.—a remarkable spread—and tailplane incidence is adjustable so that full load at aft e.g. may be trimmed By MARK LAMBERT "FLIGHT" PHOTOGRAPHS out in a glide with full flaps extended. One feature which con-tributes greatly to its STOL capability is the large wing of 306.8 sq ft area, which allows a 12.91b/sq ft wing loading. Powerloading, with the Lycoming supercharged GSO-480-B1A6 engine of 340 h.p., is 11.71b/h.p. Maximum take-off weight is 3,9701b,at which the Porter has achieved an average take-off run in still air at sea level of 120m. Incidentally, five Porters are now flying and a first productionbatch is under way. The first machine was bought by Hermann Geiger, the Swiss alpine pilot, who has described it as the bestalpine aircraft yet produced. The second was at Hanover for demonstrations. The third is now in Nepal, where it has landedfour peopleon the north-east saddle of Daulaghiri at almost 19,000ft. The fourth and fifth are bespoke respectively for a customer inMontreux and the Zurich aero club. Cockpit layout is distinctive, the pilot's seat being well forwardunder the blown windscreen and the leading-edge of the wing at about eye level. The whole floor is flat and linoleum-covered andthere is a wide shelf across the width of the cabin level with the bottom of the instrument panel. It covers a cross-bracing strutfor the mainwheel oleos, but it also serves other purposes, and I was able to use it as a desk for writing notes. The two aircraft tested (Porter to the right) were at the recent Hanover Air Show With a suction pump and 24V electrical system, full instru-mentation and radio may be fitted: dual control is also possible, but Pilatus point out that this is hardly likely to be required. Throttle and pitch levers are on the left wall of the cockpit,and tailplane trimming and flap winding handles are concentrically mounted in the centre of the roof. Position of the double-slottedflaps is indicated by a red-and-white-striped rod which emerges from the left leading-edge of the wing. Both handles have robustand simple chain-drive actuation. Toe-pedals operate the hydraulic wheel brakes independently and the tailwheel may be set lockedcentral, free or connected for steering. In operation, only the steerable setting need be used, the wheel unlocking of its ownaccord to allow castoring for tight turns. Steering is re-engaged simply by feeling for the spring lock with the rudder bar. Bothwings can be clearly seen by the pilot and the engine obstructs forward view relatively little. Engine-starting is electric, using animpulse magneto setting on one of the magnetos. When I flew, Herr Bbhme, Pilatus test pilot, sat beside me andgave instructions about engine settings and other procedures. Taxying was very easy, though the throttle had to be treatedrespectfully in order to avoid overloading the supercharged engine. We had one passenger in the back and the e.g. was at about14 per cent—near the forward limit. For take-off I set trim neutral, flaps at 30deg, pitch fully fine and applied full power against thebrakes. On releasing brake we rolled forward, pushing to lift the tail and pulled off as soon as the a.s.i. passed 70km/hr. We woundin flaps almost immediately and settled into the best rate of climb, clean, at 130km/hr. There was no noticeable swing on thetake-off run. During the climb I got an impression of light responsivenesswhich is exceptional for this kind of aircraft. The noise level was fairly high, though not as high as it would have been withoutthat great augmenter exhaust pipe. I had previously noticed that the Porter sounded surprisingly quiet from outside. At 700m I levelled off, set 70 per cent power with 1.1 atm boostand 2,600 r.p.m. and the speed settled at an indicated 170km/hr, giving an r.a.s. of about 114 m.p.h. On trying some turns 1noticed exceptionally good harmonization between rudder and ailerons with a very good rate of roll and light stick forces. Later-ally the Porter was neutrally stable and longitudinally it produced a few slow oscillations after being disturbed from trimmed speed.I could make reasonably true turns with either rudder or aileron alone, and reversals from one steep turn to the other required onlya little rudder. The aircraft would fly hands-off quite happily— indeed, I realized as the flight progressed that the Porter is ahands-off aeroplane and can be comfortably trimmed in any flight condition. For a specialized type with a large slab wingand bluff fuselage these handling characteristics were surprisingly good. [Continued overleaf *The last numbered article in thisseries was that on the Auster DA (No 118, in "Flight" for last week);but brief handling articles on the Nord 1110 and Sikorsky S-62 at theHanover show, also published last week, brought the number of aircrafttested by staff members to 120. These reports on the Porter andProspector increase the total to 122. • • . the pilot's seat being well forward under the blown windscreen and the leading-edge of the wing at about eye level"
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