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Aviation History
1962
1962 - 0728.PDF
726 FLIGHT International, 10 May 1962 HANOVER ROUND-UP... semi-military layout and finish, but a comfortable two-seat rear bench in pale grey had been added for the show. Apart from a widened fuselage and the adoption of Marbore 6 engines, giving 1,0601b thrust each, the CM. 191 is with very minor exceptions virtually a Magister in structure and handling charac teristics. Two main tanks in the fuselage together hold 315 Imp gal of either JP1 or JP4, giving an endurance ,of 3hr 20min; and these may be supplemented by tip-tanks together holding a further 55 Imp gal, raising endurance to 3hr 50min. A 98gal tank can replace the rear seats, increasing endurance to 5hr. All flight controls are mechanical, with geared tabs on the ailerons; and under carriage, flaps, airbrakes and wheelbrakes are hydraulic, with electrical selection. The canopy is electrically operated and con trolled by switches inside and outside the cabin. Pressure differential is a constant 5.71b/sq in above 10,000ft. A 3hr oxygen supply for four people is provided. Air is conditioned and flood flow is avail able for screen demisting, though it is rather noisy and windy. This prototype carried ARC-34 UHF radio, ADF and intercom and duplicated blind-flying instruments. Throttles, starters, tip-tank fuel-jettison, extinguisher buttons and de-icing pump were located on a central console, with the airbrake switch set in the throttle grip. The windscreen-canopy arch was broad and low, but interfered with visibility less than I had ex pected. Almost the entire wing, the near intake and the butterfly tail could be easily seen. Access was over the coarning with a single recessed foot-step. I found the scream of the Marbores obtrusive until the canopy seal was inflated. Taxying—steering with the very powerful toe-operated brakes—was quite easy. Elevator trim was centred with a stick-top button and 15° of flap lowered before take-off. Flap and undercarriage switches were differently shaped, but right next to each other. Alain Hisler, who demonstrated the Sipa Minijet in Britain some years ago and is now with Potez, made the take-off in the normal jet manner and climbed away with 22,000 r.p.m. at about 160kt. We levelled off at 3,000ft, below cloud, and throttled back to keep below 250kt. Normally, the cruising setting of 21,500 r.p.m. would give about 300kt at this height. I took over and flew at 220kt, making a few turns and renewing acquaintance with the extremely pleasant feel of a jet aircraft. I thought that the ailerons were already slightly heavy at this speed and might become excessively so at much higher i.a.s. The trimmer worked slowly and was powerful. Otherwise, the aircraft felt smooth and quite firm to fly. Application of airbrake caused slight roughness but no detectable trim change, the deceleration to 150kt being quite rapid. Throttled back at 190kt we descended at l,000ft/min. At below 150kt the controls were much lighter and the CM.191 was delightful to fly. We applied full power and Hisler throttled back one engine without warning. There was not the slightest swing and no residual stick forces or retrimming to do. This could not possibly be more innocuous. Brochure climb on one engine with tip-tanks full is 680ft/min. Twin-engined climb to 30,000ft at an intermediate gross weight of 6,6001b has been measured in flight tests as 20min. Rate of climb is then under 1,000ft/min. Extension by stages of the full 40° of flap caused gentle, normal trim changes. A comfortable GCA approach condition would be 120kt with some power and gear and 15° flap, giving a rate of Potez Heinkel CM.191 cockpit, a little austere in the prototype. Note the pole rectangles of the two drum horizons, here toppled descent of about 500ft/min. Under these conditions the CM.191 was absolutely straightforward to fly. I was using for the first time the SFENA electric drum horizon with blue and grey sky and Earth sectors, and I must admit that I found it slightly unnatural. One should be looking at the inside of the cylinder and not at the out side to get the true impression of pitch attitude. The Potez 840, which I flew later, had a drum horizon on one side and the Lear LIFE outside-in presentation on the other. Jacques Grangette, Potez chief test pilot, said he preferred the Lear. Having put the CM.191 into the final approach configuration I applied full power and found absolutely no trim change. It is easy to forget, after some time in piston-engined aeroplanes, how simple an aircraft can be with the pure thrust of the turbojet through the e.g., and no torque or trim effects. Hisler made the landing, approaching with flap and airbrakes extended together at 120kt. As we rounded-out I noticed how low the CM.191 sits on the ground. Brakes pulled us up very quickly and we taxied back to the exhibition area. It is very difficult to analyse the behaviour of a jet aircraft of this type, except that it is completely smooth and easy to fly. It would take some time to explore the full flight envelope up to maximum Mach number and top altitude. I have only the feeling that there is a good deal of work to do to give the cabin an acceptable executive decor, to quieten the air conditioning and make it less windy, to separate the flap and undercarriage switches and to attend to other small details. As a military machine the CM.191 is fully acceptable. It remains to be seen who buys it. Light Aircraft Equipment A sizeable section of Exhibition Hall A was devoted to equipment and accessories for light aircraft, inter esting among which were the wide variety of computers and air- Mercedes Benz displayed this prototype of their 1,000 h.p. PTL 6. A PTL 6 should fly in a Noratlas next year
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