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Aviation History
1954
1954 - 1393.PDF
616 FLIGHT, 14 May 1954 TANK STALKER . . . the bumpy conditions. French R/T. procedure was strange to me and I used a mixture of French and English, ably assisted by M. Noetinger in the control tower. "Roger" in my best Parisian accent seemed to come quite naturally— and was understood. Taxying was delightfully easy: the view over the nose virtually unimpaired and the toe-operated hydraulic brakes extremely effective and comfortable to operate. The engine responded instandy and smoothly. At the marshalling point I checked trim neutral, throtde friction nut not fitted, mixture not used, pitch auto, fuel on and sufficient for 1£ hours, flaps 15 deg, instruments (horizon and D.I.) uncaged, harness tight, door closed, hood not fitted. I got a "green" from the caravan, lined up for take-off and opened the throttle against the brakes. I released the brakes and the machine surged smoothly forward and flew itself off after about 150 yards. Although die controls were completely strange, I found them light and responsive. There was no swing at all during die take-off run, but the trimmer might have been better set a litde nose-heavy. In adjusting it I found that the wheel was perhaps a litde low-geared. The best rate of climb, which seemed to be attained at about 170 km/hr (105 m.p.h.), was a litde over l,500ft/min. I levelled off at about 1,200ft and maintained power to try the maximum level speed. The A.S.I, setded. at 350 km/hr (215 m.p.h.) widi very litde trim-change. Normal turns could be initiated widiout use of rudder. In steep turns it was necessary to use full power to avoid losing height and speed. The latter, particularly, fell off rapidly unless full power was maintained. Level cruising speed at 75 per cent power was about 220 km/hr (135 m.ph.). The view from the cockpit in all directions is excellent; die nose is narrower than might appear and offers very little obstruction to forward view. The control column is long and comfortably placed and there is ample room in which to move it about. The whole cockpit, in fact, is spacious and unobstructed. The windscreen is narrow, giving good pro tection to the face while not unduly restricting visibility. Since the propeller is behind the pilot die airstream was much less than I had expected. I next tried a slow run widi 20 deg of flap at 115 km/hr (71 m.p.h.). This was close to what I had been told was die stalling speed, but control—both lateral and fore-and-aft— was still good, diough just a litde sloppier. Since no com pass was installed, because of the interference it would suffer from the heavy armour plating, I stayed close to the airfield (presumably a Desynn or gyromagnetic compass will later be fitted). But die area was hilly and, bearing in mind the all-up weight of the machine, I did not attempt to stall at diat altitude—about 700 m (2,100ft) indicated over hills about 800ft high. I was later told, however, that the stall is docile and occurs a little below 90 km/hr (55 m.p.h.) indicated and that full aileron control is maintained throughout. For the same reasons I did not try to flick the 75 out of a steep turn, but though I executed Rate 4 turns I could detect no tendency to stall or flick. Performance under diese conditions is good —an important feature for low-level flying. I next made a dummy approach with 35 degrees of flap to assess the angle of glide. This turned out to be steeper than I expected; when I levelled out for a low run I also found that a good deal of power was required to maintain level flight with flaps down. In fact, the flaps are extremely effective. I then climbed away to a safe height and retracted die flaps, noticing a definite sink as I did so. The flap switch comes easily to hand but the motor is perhaps a little slow; it takes perhaps ten seconds to raise full flap. I was now beginning to enjoy the Potez 75. It was emi nently simple and responsive, and had die air not been so bumpy I should have indulged in some low flying; although I had only been airborne for some ten minutes I felt quite confident in the machine despite die fact that I was still conscious of being in sole charge of a first prototype. Having already assessed control at 115 km/hr (71 m.p.h.) I made my approach with a trickle of power and 40 degrees of flap at 150 km/hr (92 m.p.h.). The descent was steep and the visibility excellent. Despite a fairly strong wind about 20 degrees off the runway I had no trouble in dodging a series of ground markers and touching down next to the caravan. As was only to be expected from the Potez 75's undercarriage, the touch-down was positive and die brakes could be applied instandy and vigorously. The cross-wind caused a slight swing to develop after touch-down, but it was held on die brakes without difficulty. After turning off I tried one fast taxying run at about 50 m.p.h. and experienced for myself the magnificent control on the ground. Taxying was, in fact, reminiscent of driving a high-powered sports car and it was all too tempting to try a three-wheel drift. Perhaps the only complaints one could make about the machine are that the dirotde lever is rather far forward and die trim wheel on the wrong side. If the door could be replaced by recessed steps in the side of the fuselage, die throttle could be moved back slighdy and die trim wheel fitted on the left. These, however, are not serious faults. I was told, incidentally, that it is intended to fit an armoured glass bubble canopy for the pilot to protect him from stray sniping from the ground. I would here repeat that the machine is not to be regarded purely as an aircraft, but as a missile-launcher for the army. The whole project is, therefore, a "weapons system" (to use the American term), the machine and die missiles being as inseparable as a field gun and its shells. Extensive trials have already shown diat the Potez 75 may yet prove to be as effective as a previous "75," the famous French field gun. One cannot help feeling that in die event of war there would be an immediate demand for the Potez 75 as an army anti-tank vehicle. It is true to say that the machine is simple enough for the average private pilot to use effectively. With the missile armament for which it is planned it would cer tainly prove a most effective weapon against enemy armour —in fact, the sort of machine which might have suited the German, Stuka pilot, Ernst Rudel, literally down to the ground. POTEZ 7S (Potez B-D3Z, 480 h.p. for take-off; rated power, 350 h.p.) Di mentions:— Wing span 42.98ft (f 3.10 m) Length 30ft (9.76 m) Height 8.9ft (2.70 m) Weights:— Disposable load (inc. missiles and 300 rounds of 0.5in ammunition) 1,320 1b. (600 kg) All-up weight 5.280 lb. (2.400 kg) Wing loading 21.3 Ib/sq ft (106 kg/m2) Power loading 11 Ib./h.p. (4.2 kc/h.p.) Performance (at 5,280 lb all-up weight):— Max. speed (fully loaded) 171 m.p.h. (275 km/hr) Cruising speed at 75 per cent rated power ... ... 140 m.p.h. (225 km/hr) Max. rate of climb 1,570 ft/min (8 m/sec) Take-off run 190 yd (f75 m) Landing run 180 yd (f 65 m) To clear 15 m obstacle from take-off 515 yd (470 m) To land over 15 m obstacle 300 yd (275 m) Landing speed ... ... "... ... ... ... 68 m.p.h. (11C kmlhr) Range 435 miles (700 km)
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