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Aviation History
1955
1955 - 0526.PDF
526 FLIGHT, 22 April 1955 Gleaming in the warm South African sunshine, the Bri- tannia is seen on take-off at Johan- nesburg. The ten wheels are already beginning to retract. BRITANNIA'S JOHANNESBURG TRIALS Phase One of the Tropical Tests: Encouraging Preliminary Report '"TROPICAL trials of the first production Britannia were rounded• -*• off in fine style on April 14th, when G-ANBA returned non- stop from Khartoum to Filton. Despite a headwind componentof nearly 60 m.pii., the aircraft covered the 3,150 miles in 10 hr 55 min at an average speed of 290 m.pJi. Considerable satisfaction with both phases of the trials—high-altitude tests at Johannesburg and high-temperature trials at Khartoum—has befl! expressed by the Bristol Aeroplane Co.Full analysis of all the performance measurements made in Africa will take some weeks to complete. The company has, however,issued a preliminary statement on the Johannesburg trials which gives a good idea both of the nature of the tests and of theBritannia's response. From the trials viewpoint, the Bristol report notes, weatherconditions were excellent: winds were very light and temperatures were comfortably on the high side, averaging 1 SAC+18 deg C(73 deg F). "Each morning," it continues, "a briefing meeting was held at 9.30 and at this it was decided exactly what was to bedone. The aircraft generally took-off at about 11.30, and due to the finely accurate flying of W/C. Gibb the programme wasexecuted efficiently, with despatch and without the necessity for second and third attempts." The daily pattern of trials at Jan Smuts, which is 5,500ft abovesea level, was substantially constant, the only changing factor being the progressive increase in the aircraft's weight. The programmewas as tabulated at the foot of this page. Bristol's statement explains that the power-cut points for thethree-engine take-off and accelerate/stop cases differed in that for the former the starboard outer engine was cut (by HP fuel cock)at low speed, i.e., circa 125 m.p.h., whereas for the start/stops the aircraft was accelerated to high speed, circa 155 m.p.h., before theengine was cut. It also observes that after an accelerate/ stop— which is the full simulation of an emergency condition—it wouldbe permissible to renew the brakes, and continues: "It says much, therefore, for the Dunlop brakes, wheels, tyres and Maxaret anti-skid system that five accelerate/stops (one at 147,400 lb and with only partial reverse thrust from the propellers, and one at150,000 lb), plus a set of six landing tests, plus 13 high-weight (130,000-149,000 lb) landings, plus all the other normal landingswere made before it was thought necessary to change the brakes. An advantage of the Maxaret system is that it ensures even tyrewear all round the circumference; the wear of individual tyres may vary among themselves, but the wear on any one tyre iseven." As an instance of typical landing performance, the followingis cited: with the aircraft at 116,000 lb (i.e., 1,100 lb over the normal maximum landing weight) the measured distance fromclearing 50ft to standstill was 3,400ft. The Britannia was, in fact, on one occasion landed at 149,000 lb—34,000 1b over thenormal maximum. Bristols agree that "Perfect weather condi- tions and knowledgeable handling contributed much to this," butadd that "even so it also says a good deal not only for the British Messier undercarriage, but for the quality of the structureas a whole." Another set of figures is quoted as an indication of the standardof the aircraft's performance: "In an accelerate/stop trial at the 150,000 lb maximum all-up weight of the Mk 100, with an ambienttemperature of 1SAC + 18 deg C (73 deg F) and at a power-cut speed of 155 m.pii., the measured start-to-stop distance was but7,530ft. The quality of the results obtained throughout the accelerate/ stop trials was somewhat better than had been expectedand this is almost certainly ascribable to the fact that the de Havilland reversing airscrews proved to be more effective thanhad been previously realized." Johanneihurg Trial* Programme March 1*th.—Four full-power take-offs at 112,000-124,000 Ib; three three-engine take-offs at 114,000- 123,000 Ib; one accelerate/stop at 110,000 Ib; fourlandings at 110,000-120,000 Ib. March 17th.—Three full-power take-offs at132,000-140,000 Ib; three three-engine take-offs at 132,000-137.500 Ib; two accelerate/stops at 138,000and 141,0001b. March 18th.—Two full-power take-offs at 144,000-146,000 Ib; one three-engine take-off at 145,000 Ib; one accelerate/stop at 147,400 Ib (with only partialreverse-thrust braking), March 20th.—Two full-power take-offs at 149,000-150,000 Ib; two three-engine take-offs at 150,000 Ib; one accelerate/stop at 150,000 Ib. March 22nd.—Two full-power low-speed take-offsat 135,000-137,000 Ib; one accelerate/stop (superfine pitch), 137,000 Ib; four landings at 114,000-120,000 Ib. Local interest in G-ANBA at Jan Smuts Air- port, Johannesburg, where the Britannia's unusual low external noise-level caused it to be dubbed "the whispering giant."
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