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Aviation History
1960
1960 - 0334.PDF
334 FLIGHT, 11 March I960 NORD-AVIATION 3400 ... by hydraulic hand-pump at the left of the seat and with an engage-ment button in its handle-tip) are spring-loaded to return when a toggle lever on the side shelf is pressed. The flaps are ratherslow to rise on the ground, because they are balanced to the air forces in flight. The flap indicator, of the slide type, is on one ofthe port cabin frame tubes. There was a gusty 15kt wind when I tried the Nord 3400; itproved the stability and responsiveness of the aeroplane, but perhaps rather over-emphasized the excellent STOL performance.Upon opening the throttle, with 35° flap and stick slightly for- ward, I found that the tail came up quickly and the 3400 lifted offthe ground in a level attitude after perhaps forty or fifty yards and at about 85km/hr (45kt) IAS. On raising the flaps acceleration ismarked, and slightly more aft trim is needed to maintain the best climb speed of 125km/hr (68kt) which gives some l,400ft/minand a steep gradient. Trimmed to level cruise, the 3400 proved unusually stable anddocile. The controls are not quite as light as one expects in a French aeroplane and the large span gives considerable inertia inroll, so that I found I tended to slip a bit when changing bank in vertically-banked figure eights. The marked ability to turn tightlyon a point, however, is best expressed in Lanvario's words, "she'll turn on a chimney-stack." The stub exhausts, debouching almostunder one's feet, make the cockpit rather noisy; but with a headset it was not unpleasant. Incidentally, an occasional "bleep" during The cabin of the Nord 3400, showing the steel-tube framework and light-metal panels. The windows on both sides open upward, the sfc» panels hinge downward (the port one gives stretcher ingress), and the seat swivels through 360°, locking forward or aft the tightest turns finally registered with me as the stall-warningindicator working through the intercom. Flaps up and throttled, the stall is innocuous and is preceded bylight buffeting. With nose fairly high and the stick well back th» 3400 can be held in a "mush," using rudder to pick up any tenldency for a wing to drop. With 35° flap the nose was lower and there was some pitching, but it could still be held in a mush withthe ailerons effective—and by no means sluggish. With flaps up the stall occurred at about 88km/hr (47kt) IAS, and with flaps at35° it was about 75km/hr (40kt)—even off the clock on one occasion. Although I did not try to prove it, I should think thatthe 3400 is virtually unstallable with power on and flap. The stall with full flap, 60°, is given as 72km/nr (39kt) IAS, 80km/hr (43kt)1 Ao. Approaching to land, it was necessary in the 15kt wind to comewell up to the threshold before throttling to 120km/hr (56.5kt) and lowering the flaps to 35°—limiting speed is 150km/hr (81kt)IAS. Slight rearward trim is then needed for comfort, but the elevator load is not heavy. At llOkm/hr (60kt) and half-flap theapproach was steeper than average. On the final stage, with 60° flap, at 95km/hr (51kt) in that wind the ground seemed to risealmost vertically. Nevertheless, with all controls responding crisply, even though feel was slight, it was not difficult to maintaina steady approach speed using a little power and 2,200 r.p.m. Closing the throttle over the hedge, there was comfortable time toround-out, and—as speed dropped rapidly to the touchdown at 70km/hr (38kt)—to get the tail down (the double slotted flaps at60° result in a large angular change) to a three-pointer. The under- carriage makes a positive contact with the ground and the aero-plane feels really there in one. The landing run seemed to be only fifty or sixty yards, on the runway and without brakes. NORD 3400 Powerplant: Potez 4D flat-four; dry weight, 4031b; take-off power, 240 h.p (4D30) or 260 h.p. (4D34) at 2,550 r.p.m. with specific consumption of 0.675; economical cruise rating, 130 h.p. at 2,000 r.p.m. at 7,500ft (4D30) or at 9,200ft (4D34) with specific consumption of 0.475. Dimensions: span, 43ft; length, 27ft 8in; height, lift 2in; tailplane span, lift lOin; track, 7ft 3in; gross wing area, 224 sq ft. Weights: empty equipped, 2,1151b; fuel (48 Imp gal), 353fb; crew, 3971b- disposable load, 1101b; maximum gross weight, 2,9751b. Performance (ISA, 4D30 engine unless otherwise stated): take-off ground run (4D34), 360ft; distance to 50ft (4D34), 770ft; initial climb, l,400ft/min at 2,400 r.p.m. (l,900ft/min with 4D34 at 2,550 r.p.m.); time to 13,000ft, 15min at 2,550 r.p.m. or 18min at 2,400 r.p.m.; max speed, 124kt at 2,400 r.p.m. at 4,250ft; economical cruise, 108kt at 2,000 r.p.m. at 9,000ft; range, 600 miles; minimum speed, approximately 40kt; distance from 50ft, 950ft; ground run, 330ft. HELICOPTERS IN THE BUILDING TRADE TN conjunction with the contractors building a school at Yeovil,*• H. Hoskins Ltd, and Westland Aircraft Ltd, experiments were recently made by Concrete Ltd, in the use of a helicopter for posi-tioning "Bison" pre-stressed concrete purlins weighing about 15 cwt each. A director of the specialist contractors, D. W. Wood, BA,MBIM, AMiProdE, has since prepared an informative paper on the subject, some abstracts of which appear below. The experiment was carried out in two stages; an investigation intothe practicability of fixing precast units directly on to their wall or beam bearings; and, an exercise in precision lifting and handling into positionat ground level. Whilst fixing helicopter-suspended precast units on to 4iin widebearings at second floor level, without scaffolding, it was found that there was not sufficient purchase to enable men standing on the wall to guidethe units on to their bearings, added difficulties being due to the unusual working conditions, i.e., presence of a down-draught of gale force setup by the helicopter blades, and a torque reaction effect on the purlin due to a spinning component in the down-draught.Exercises carried out at ground level proved to be more promising and focussed attention upon certain basic principles of precise loadhandling by helicopter. Precast units were picked up by helicopter from a lorry, and carried about 100yd across soft muddy ground, whichthe lorry had been unable to cross. The helicopter-suspended precast units were then, without much difficulty, placed upon prepared ground-level bearings to an accuracy of lin. Total cycle time to pick-up from lorry, Precast Unit No. traverse 100yd, and fix into required position, with accuracy of 1in min 1 5.82 3 3 4.74 6 5 36 3.8 Six precast units were placed on to their bearings in this way, thetotal cycle times per unit being as given in the table in Column 1. There is general agreement that, with trained operators at groundlevel, an average cycle time of 4min could be achieved over any distance up to 250yd between lorry and fixing site. The experiment clearly showed that it is a practical proposition tofix precast units by means of a helicopter but adequate preparations must be made beforehand. These include the following: (1) Provisionof a good working platform alongside the bearings, for use of the ground crew when placing a unit in position by means of guide ropes. (2) Specialarrangements to prevent the units sliding between the bearings, if slightly twisted due to the torque effect of the helicopter blades or if slightlyout of position on first placing. (3) Correct briefing of the pilot, his observer and the ground crew, who must have worked together withunits on the ground for a short period before attempting to fix units on to their actual bearings. (4) Provision of adequate protective clothingfor the ground crew, i.e., close-fitting overalls, goggles and berets, as used by Army and Navy personnel under similar conditions. Clearly, the use of a helicopter must be more expensive than employ-ment of the more traditional methods. However, there are circum- stances where advantages could be gained by using a helicopter. Atypical example would be where the architect particularly wanted a clear span on a building and where access conditions precluded entry of long-wheelbase lorries carrying precast slabs more than 30ft. long. Hollow precast purlins 33ft long weigh about 1 ton each and such purlins couldbe fixed by helicopter at a rate of not less than twelve per hour. Twelve such purlins at 4ft centres would cover a roof area of very nearly1,500 sq ft, so that the purlins for a roof of 3,000 sq ft could be fixed in about two hours. ' ' It is obvious that at present there are no agreed prices for such opera- •tions but, in the not-too-distant future one can foresee helicopter hiring companies offering to carry out precast slab handling and fixing opera-tions for a hire charge of, say, £150 per half-day, or Is per square foot for the example quoted. Often, the cost of an adequate service roadover difficult ground conditions would come to more than the £150 in question. In such circumstances the architect and client might well beprepared to pay this amount to secure the tremendous advantage of a long dear-span building.
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