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Aviation History
1995
1995 - 0030.PDF
FLIGHT TEST Bell with bite The AH-1W SuperCobra is the basis of the Bell/ GEC-Marconi Venom Cobra, a candidate for the British Army attack helicopter PETER GRAY/DALLAS My first pull-up in to the hover in the Bell AH-1W SuperCobra combat helicopter was adequate, but not completely satis factory, so I landed and tried again. In every helicopter one has not flown before, the first pull-up presents several challenges. You have to try to outguess the aircraft's attitude in both pitch and roll and try to keep it straight as it breaks ground, so as not to lurch sideways, for wards, or backwards, or yaw. The front cockpit of the SuperCobra provides additional challenges because the floor-mounted cyclic stick and collective lever are absent. There is a 150mm stalk (or "stubby") on a shelf on the right-hand cockpit wall, instead of the cyclic stick, and a second 150mm stick, with two twist-grip throttles, representing the collective lever on a similar shelf on the left- hand side. This is moved fore and aft, instead of up and down, which is more usual. Both shelves are padded, which allows the pilot's arms to be comfortable and relaxed. This arrangement makes room for the SuperCobra cockpit presents additional challenges weapon-sighting and firing systems which take centre place in the front-gunner's cockpit. The cyclic stubby has no trim-release switch or "coolie-hat" trim to help centralise it. INITIAL TAKE-OFFS Watched by Bell's chief production test pilot, John Honaker, in the rear cockpit, I pulled the collective sidestick slowly towards me, lightly grasping both throttles — my left arm was bal anced on the cushioned shelf. I waited expec tantly, with my right hand poised around the cyclic side-arm. As we lifted off, we drifted slightly to the left, but the heading and height were good, so I was not too unhappy with the results. Despite the strangeness of the controls and their feel, I was able to contain the subsequent hover to within a metre or two with satisfactory pitch, roll, height and heading control, which was just as well, since we were on the main apron at Bell's Fort Worth, Texas, plant, surrounded by expensive machinery. I was not satisfied with my first attempt, so I performed my first landing and had another go. With the advantage of hindsight, I was able to achieve a near vertical take-off on my sec ond attempt because of the AH-lW's good handling qualities and design. We used 75% of the available power, giving us a healthy power margin, which is vital for nap-of-the-earth low flying — 50ft (20m) and below. Although our weight was 660kg less than the maximum operating weight of 6,700kg, at 1,500ft density altitude, the two General Electric 1,2 lOkW (1,625shp)T700- 401 engines still had plenty of power in hand at gross maximum weight up to altitude. We also had extremely impressive single-engine per formance, as I was soon to find out. Because vibration-free perfor mance is so important in attack helicopters, to allow accurate target sighting, tracking and weapons firing, I assessed it care fully throughout the whole flight envelope. Two-bladed machines are renowned for high vibration levels, compared with their multi-bladed equivalents. The SuperCobra is remarkably smooth in the hover and all hov ering manoeuvres. Bell has developed strut-and-weight mechanical vibration suppres sion system called Vibrex. The canopy transparency is divided by the thinnest of struts, giving superb all-round visibility. This, too, is important for the job to be done. The Cobra's many predecessors date back to 1962. For helicopter enthusiasts, it ranks as one of the world's great helicopter designs. Many modifications have been made since then and there are many more to come. The AH-1W is one of the latest versions. GEC- Marconi is offering a variant of it to the British Army in the form of the Cobra Venom. PRE-FLIGHT CONSIDERATIONS After a thorough ground briefing which included a week's groundschool in 90min, Honaker showed me round the aircraft. Approaching from the front, I noted the typically thin Cobra fuse lage, the non-reflective, laser-sight-resistant paint (both designed to avoid detection), the three-barrelled 20mm cannon under the nose, die sighting system on the nose, die two 3.25m- span stub wings, with one empty'TOW launcher installed on each, and the cable cutters — no matter which way the wire goes, up or down, the FLIGHT INTERNATIONAL 4 -10 January 1995
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