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Aviation History
1987
1987 - 1414.PDF
Alaska National Guard modifies Blackhawks ANCHORAGE The Alaska Army National Guard is upgrading its fleet of Sikorsky UH-60A Black- hawks to improve their effectiveness in low temperatures and Alaskan terrain. If the modifications are successful, they may be adopted as standard customer options. The parent unit for the Alaska Army Air Guard is the Army Aviation Support Facility (AASF) at Fort Richardson, Anchorage. This Unit oversees operations of the 1898th Assault Helicopter Unit with 28 Bell UH-1H Iroquouis, the 5th Scout Battalion with two UH-60A Blackhawks and one UV-18 Twin Otter, the 2067th Infantry Group with two UH-60s and one UV-18, plus a heavy-lift group with four CH-54 Skycranes. In addition, the Guard supports scout battalions in Juneau, Bethel, Nome, and Kotzebue, each with a pair of UH-lHs and a single Twin Otter. Logistics flights are made with a Beechcraft C-12 based at nearby Elmondorf AFB. The need to upgrade the Blackhawks stems from the vast distances in Alaska, the low temperatures, and poor landing conditions on powder snow and the bog-like tundra. To date, operations have largely been confined to hard- surfaced facilities within the Anchorage area, because the Blackhawk has neither the range nor the stability on soft ground to operate in typical Alaskan terrain. The lead programme was a lengthy evaluation of external fuel tanks. Trials were completed early this Spring, and the fuel tanks were then returned to Sikorsky. A second modification is the installation of a high output heater for the passenger cabin. The standard Black- hawk heater is effective in the cockpit area, but was found wanting in the rear passenger compartment, especially during winter operations when outside temperatures can drop to -25°C to -30°C and door seals lose their effectiveness. A new-model electric heater manufactured by General I Electric has been installed temporarily behind the rear cabin bulkhead. It produces 55,000 b.t.u. of heat for the passenger compartment and, if the trials prove successful, a more sophisticated ducting system will be installed on production aircraft. (On the Guard's UH-lHs a muff heater is installed around the engine exhaust.) The most demanding and time consuming of the three modifications programmes has been the development of suitable skis for the Black- hawk. This involved flight testing at Sikorsky's facility in West Palm Beach, Florida, and, more recently, snow trials in Alaska. Without skis most wheeled helicopters operating in Alaska will sink in the snow and soft terrain that covers most of the state. This presents a year-round hazard, particularly if a run- on landing or autorotation becomes necessary. The Guard's Sikorsky CH-54's feature three large balsa wood and glassfibre skis of 1960s design, weighing about 3001b each. These are relatively unstable in flight, and require constant repair to damage caused by landing the 47,0001b helicopter on rocky surfaces. The Blackhawk installation, which is more sophisticated, was developed by Landas Engineering of Anchorage, which has been making glassfibre skis under the Airglas name since the early 1960s. The design of the main Blackhawk skis is based on Airglas' rear ski for the Boeing CH-47 Chinook. Built in two parts and using glassfibre-reinforced poly ester, and epoxy, the hollow ski is 115in long and about 37'5in wide. The upper surface has been modified to accommodate the Black- hawk's undercarriage drag beam. The undersurface has a Teflon and urethane coating which is slick on snow. The installation of the skis was a challenge because the Blackhawk undercarriage was not designed from the outset to accept skis (unlike that of the CH-47). The proper angle of attack of the skis had to be maintained both when the helicopter was at rest on a prepared surface and when the oleos were extended, in the hover or forward flight. The design could not inhibit the use of a tow bar. The Airglas installation is a wheel ski arrangement where the main gear legs extend about 3in below the ski when the helicopter is on the ground at maximum gross weight. The ski attaches to the gear leg on extensions to either side of the main-wheel axles. A spring between the ski tip and the gear drag beam maintains the ski at a neutral angle when on the ground. In flight, as the oleo extends, a cable between the fuselage and the rear of the ski, working in concert with the spring at the tip, adjusts the ski to flight attitude. The tail ski, which is square in shape, is maintained at the proper angle of attack by a spring. To reduce wear on the ski during run-on landings, a small tailwheel has been installed on the ski. Similar wheels at the rear of the main skis keep these from dragging on the ground during taxiing. The complete installation of three skis and hardware weighs about 3801b. The main skis weigh 1691b each with hardware, and the tail ski weighs 421b. The contract for the proto type skis was let in late 1986, and delivery of the first skis to West Palm Beach followed in early 1987. The flight test programme in Florida required about 40hr flight time on a Blackhawk before the skis were shipped north to Alaska last May. While only four Black hawks are now active in Alaska, the Army National Guard and the regular Army expect to receive additional aircraft. At present the National Guard, rather than the Army, operates the most modern fleet within the State, equipped with modern naviga tion aids paid for by the State of Alaska. INTERNATIONAL, 8 August 1987 Israel shows laser bomb Israel Aircraft Industries has developed a laser-guided bomb called Guillotine. IAI says the weapon has a range of 30km from 40,000ft and the laser sensor features automatic search and lock-on to laser energy reflected from the target. The penetration angle is 45°, and it has a 2m circular error probability FL
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