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Aviation History
1963
1963 - 1806.PDF
FLIGHT International, 10 October 1963 615 blades for almost five years. Each blade is pressurized to lOlb/sq in during manufacture and then sealed. A small pop-out indicator by Walter Kidde is screwed into the root of the spar to provide a red warning aspect in the event of the air pressure inside the spar falling below a preset level. Ultimately Sikorsky believe that the US Services and Federal Aviation Agency may place such complete confidence in BIM that no blade so fitted will be removed unless an indication of air leakage has occurred. At present a typical S-61 blade life is 3,600hr, as noted later. A unique feature of these new Sikorsky rotors is that all blades are interchangeable, and are pre-tracked at the factory. In the SH- 3A the five blades are automatically folded to facilitate shipboard stowage. When the rotor is being folded, the No 1 blade is ranged straight aft and the pilot then operates the folding control which hydraulically unlatches the other four blades and folds them back wards so that the inner two lie alongside the centre blade and the remaining pair rotate about skewed hinges to lie alongside the rear fuselage. Similar power folding is provided for the complete tail- end, to reduce the stowed length from 72ft 5in to 46ft 6in. Unlike earlier machines the SH-3A has a main-rotor hub entirely of high-strength steel, which at once eliminates fatigue problems and reduces the bulk of the component parts. In the context of ASW operations it has a further advantage in improved resistance to corrosion. The hub and upper plate are fabricated in one piece, and the hub incorporates a gravity-feed oil system which lubricates the main rotor in flight. In the event of a main-rotor blade parting company with the hub all S-61s may continue to fly under complete control despite the resultant unbalanced centrifugal force of 60,0001b rotating around the hub. Ralph Lightfoot, Sikorsky chief engineer, confirmed to this journal that the remaining four blades automatically tend to respace themselves by rotating about their drag hinges, to fill the gap left by the missing blade. In fact he recalled that an experi mental S-58, with only four blades to start with, had been success fully landed after losing a complete blade during flight tests. The tail rotor—which Sikorsky call the "rotary rudder"—has five blades each comprising a solid, machined aluminium-alloy spar and honeycomb core with an aluminium-alloy skin wrapped round and bonded at the trailing edge. Over the outer 80 per cent of the leading edge a stainless abrasion strip is added, and root and tip are both sealed. Blades are again interchangeable, and mounted in a steel hub. Engine and transmission accessibility is everywhere exceptional. The main cowling panels form service platforms, and further platforms are provided next to the working transmission com ponents arranged outside the fuselage below simple fairings. Engine intakes are electrically de-iced, the drive torquemeters are integrated with the Sikorsky gearboxes, and the rotor brake on the front of the main gearbox can stop the dynamic components from hovering r.p.m. within 30 seconds. Ground accessory power may be provided by driving the accessory section of the main gearbox from No 1 (port) engine and locking-out the rotor drive. Fuel is carried in two 350 US gal flexible cells under the floor. Structurally the airframe is quite conventional, the ruling materials being aluminium alloys of the 7075 or 2024 series. The semi- monocoque hull is made proof against corrosion and sealed for amphibious operation. The big electronics door in the nose has an inflatable nylon seal. The SH-3A also has a wide funnel-like sonobuoy hole in the centre of the bottom, but the floor is above normal water level. The tailwheel is fixed, but the twin-wheel main gears retract into the stabilizing floats. Flight controls are fully powered, and integrated with the Hamilton Standard automatic stabilization equipment. The ASE, which has flown some 600,000hr in 800 helicopters, provides pitch, roll, yaw and altitude stabilization and enables missions to be accomplished "hands and feet off" even in IFR conditions. In the SH-3A the integrated flight system includes a Ryan APN-130 Doppler navigator and an APN-117 radar altimeter, together with a coupler to the Bendix AQS-10 sonar system. Although on February 7, 1962, an SH-3A gained a world helicopter speed record at 210.6 m.p.h., the specification performance in US Navy operation is limited by the stringent hovering require ments of the ASW mission, a fact which also applies to the CSS-2s of the Royal Canadian Navy. These restrictions do not apply to the S-61 A (CH-3B) utility transport, in which the sonar and wea pons are replaced by up to 25 troop seats, the automatic blade folding is removed and the floor is stressed for cargo. President Kennedy uses a special VH-3A with wide-view windows and an individually constructed chair so comfortable that he has had a similar one installed in the White House. The VH-3As and some CH-3Bs have a fairing over the main-rotor hub to improve airflow in the hover. The first real helicopter airliner was the S-61L, which received FAA certification in November 1961 and entered service with Los Angeles Airways the following January. The reduced density of the passenger payload required the insertion of an extra 50in into the fuselage, with baggage door to starboard. This makes room for 28 passenger seats at 34in pitch, with a large window at each seat row, plus pilot, co-pilot and cabin attendant, 5001b of luggage and racks for coats and hats. The S-61L is not amphibious, for there is no water area on the LA Airways routes; the undercarriage is fixed. Amphibious capability is restored in the S-61N, ordered by Mitsubishi in Japan, Pakistan International and British European Airways, and subject of the main cutaway illustration. The floats and retractable main gear reduce the available payload to 27 passengers, and the water-sealing eliminates the slide-out baggage pod under the forward fuselage of the S-61L. At the same time, flight characteristics have been improved by increasing the height and area of the tail pylon. Operations by LA Airways indicate a d.o.c. of approximately 7c per seat-mile over stages up to about 200 miles. This is consider- HELICOPTERS Dimensions (ft-in) (continued) Main wheel track 10-0 12-0 9-0 12-0 6-0 il-0 11—0 19-9 12-0 !4-0 14-0 8-0 19-9 13-0 13-0 13-0 14-0 13-4 12-2 12-2 19-9 13-0 Cabin length 7-3 8-4 7-0 8-4 7-7 10-0 10-0 30-4 12-10 12-10 12-10 7-7 n.a. 23-11 19-3 31-11 31-11 25-10 14-0 14-0 n.a. 30-0 Cabin width — 3-11 3-11 3-8 4-8 4-6 5-2 5-2 7-9 5-0 5-0 5-0 4-6 n.a. 6-6 6-4, 6-6 6-6 6-6 5-4 5-4 n.a. 7-6 Empty equipped 2,010 3.781 2,034 4,050 1,825 4,950 5,250 20,831 7,750 7,900 8,275 2,200 19,613 9,911 11,194 11,333 11,576 11,248 5,083 4,840 17,688 20,950 Weights (lb) Useful load 530 1.115 589 1,450 875 2,250 2,250 10,169 5,250 5,100 4,725 1,360 11.587 9,089 6,574 7,667 7,424 8,072 3,017 3,060 20,312 12,534 Normal gross 1,290 2,540 4,896 2,623 5.500 2,700 7,200 7,500 31,000 13,000 13,000 13,000 3.560 31,200 19,000 17,768 19,000 19,000 19,320 8,100 7,900 38,000 33,484 Max gross — 5,381 2,904 .— — 7,900 7,950 — 13,600 14,000 14,000 .— 34,500 21,500 19,100 22,000 8,300 High speed SL, NRP(kt) 52 71 78 87 90 96 88 97 113 106 106 105 127 113 138 129 127 127 143 95 88 102 170 Performance (normal gross, standard day) Cruise SL, (kt) 43 56 69 65 74 79 74 79 100 84 84 84 120 100 126 — 122 122 126 85 80 95 150 climb SL, NRP (ft/min) 650 870 780 1,000 1,050 700 1,020 910 1,100 1,100 1,100 750 910 1,500 1,550 1,300 1,300 1,960 1,080 1,140 1,400 1,820 one-eng climb SL, TOP (ft/min) n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 50 n.a. n.a. n.a. n.a. 50 170 270 120 120 100 n.a. n.a. 350 200 Hover fl In ground effect 5,000 2,600 6,400 5,800 4,500 4,900 4,900 4,900 8,500 3,300 9,000 — 6,700 6,700 6,200 12,200 6,600 9,700 11,500 ceiling t) Out of ground effect 500 1,400 1,500 3,100 1,100 2,000 2,300 1,100 2,400 2,400 2,400 7,000 800 5,000 6,000 3,600 3,600 3,700 7,100 4,600 4,700 7.200 Service ceiling (ft) 8,000 14,100 10,000 13,500 12,000 9,800 10,500 8,700 9,500 9,500 9,500 16,000 10,800 12,800 10,200 11,500 11,500 12,000 11,200 6.600 10,500 16,700 Cruise fuel (lb/hr) 72 220 78 168 96 222 258 1,500 528 528 528 330 1,500 1,175 1,090 1,130 1.130 1.200 429 370 3,460 2,070 Range 10% reserve (n.m.) 200 200 100 240 266 400 \ 360 / 145 215 1 215 V 255 J 220 230 470 "I 465 240 y 240 425 I 412 \ 401 / 150 245 No. of »/c built 1 131 65 229 220 95 1,290 156 1,575 2 1 195 28 3 — Approx flight time (hr) I02| 50,100 51.000 34,700 198,000 32,600 2.1m 120,000 1.75m 100 300 90,000 30,000 500 —
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