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Aviation History
1947
1947 - 0347.PDF
MARCH 13TH, 1947 FLIGHT 229 Ice on the leading edge of the starboard tailplane. The uppe 0> indicator is free but the horn balance is heavily coated. A large " cabbage'' has formed on the starboard elevator ho rn. momentary high load is consideredacceptable. There is no doubt that a thoroughpractical research into icing should have been carried out some years ago by oneof the national establishments. Figures have hitherto been mainly theoretical;A.R.B. estimated flo\j? requirements, now to be modified, are an example whichmay be compared with T.K.S. recom- mended fluid flows and the quantitiesrecently found to be necessary for the Viking in practice. Various calculatedand tested flow figures are given below. All are expressed in pt/hr/sq ft (or inthe case of airscrews pt/hr/ft run), and the two columns, recommended low andhigh rates of flow. (1) Flow estimated by A.R.B. (to prevent severe icing at -5 deg C and -20 cleg C). Wing and tail 0.18 0.0 Airscrew 0.33 • 0.83 (2) Calculated Fluid Required (K.AE. Theory). ' Winy 1.53 4.00 Tail 1.6 3.0 (3) Fluid Rates and Duration (Original System. Normal and Emergency flow). Wings o. 2 1.0 Tailplane and fin 0.2 1.0 Airscrew 0.33 1.65 Tank capacity 15.4 gal. Duration 2hr 50mm or 34mm. One pump and T.K.S. Controller giving "normal" or "emer- gency." (5 x normal) flow. One tank (15.4 gal) in starboard inner wing. (4) Fluid Rates and Duration (System as Flight Tested). Wings 1.0 Tailplane and fin 2.0 Airscrew 0.83 Tank capacity 73.8 gal. Duration 3hr i3min. One pump and T.K.S. Con- troller. Two tanks. Original (15.4 gal) and nacelle tank (starboard, originally used for fuel) 58 gal = 73 gal. (5) Fluid Rates and Duration (Final. Scheme, European Aircraft). Wings 1.0 2.0 Tailplane and fin 2.0 4.0 * 8.0 16.0 :ew 0.S3 1.66 Elements in each horn gap and on leadinger'gc of fin horn and starboard horn. Tank • capacity 73.8 gal. Duration 2hr 54mm or'In 27mm. (Duration with 30.8 gal, ihr 15mm or ohr 37mm.) Two pumps andspecial controller giving full flow from either or both pumps. Not coupled to ice detector.Pump failure warning device. It must be stressed that in the Vikingtests icing conditions were carefully ^arched out, and the aircraft was thenflown around in the area for long periods t(1 collect ice. Only under exceptional cirrumstances would an aircraft remainin icing conditions for as long as an hour v. hen operating over European routes. In that the normal flow of de-icing fluid was found to be inadequate, various measures were tried. These were: (a) An increased average flow over thewhole aircraft. (b) Recalibration of delivery pumps tointensify local flow over tailplanes. (c) Addition of a second fluid pump asa standby and for emergency delivery increase. «.. For quick de-icing it was found to be 5SMIN Stages and times for the build-up of iceformations on tailplane leading edges in medium icing conditions. essential to prime the system before theflight, and it then took about 30 seconds for the fluid to begin to appear on clearelements, and about 1 minute from under ice. Within five minutes of the systembeing started the last nodules were dis- appearing. Stages are illustrated. Most of the tests were conducted innormal icing conditions, and an average rate of build-up was one inch in 20minutes, although on one occasion of severe icing one inch formed in 3 minutes. The extraordinary cabbage formationon the elevator horn has been drawn in its various stages of formation. Beingentirely stalled, the iced horn had no effect on the elevators except as a massbalance. Broad conclusions formed from testresults were: (1) The Viking as tested was safe even if the de-icing systemfailed. The increased T.K.S. flow rates are not, therefore, particular to theViking. (2) The prescribed flow rates were not adequate for European condi-tions. (3) When modified-as indicated, de-icing was satisfactory, and there wereno adverse aerodynamic effects. Additional conclusions were that theoriginal " normal " flow (2 x T.K.S. recommended rate) did not remove sub- stantial ice formations, but that it wouldprevent some icing in rnild ice conditions. The aircraft was also.found to fly safelyon one engine(starboard engine cut) when carrying ice, and on test climbed at120 ft/min at about 32,000 1b A.U.W. • It should be mentioned that no troublewas at any time experienced with the fin or rudder. However, in keeping withother tail surfaces, their flow will be doubled. For ice prevention the modifiedT.K.S. system is now satisfactory. Temporary measures to increase thede-icing fluid capacity on the European Vikings have necessitated the use of onenacelle fuel tank of 58 gallons capacity. As soon as new de-icing fluid tanks canbe made and fitted, the nacelle fuel tank will revert to its original purpose.! Vikings for non-European services will probably carry 31 gal of fluid. Airscrew icing gave no trouble at anytime, and no ice was seen on newly- feathered blades. That ice did form onthe blades, however, was proved by dents in the fuselage opposite their tips, andby the considerable hammering noise it .made on impact. Engine icing also gave no trouble, andthe internal hot-air, intake worked well. Use of hot air for landing has, however,been incorporated in Viking landing drill. This has little effect on power cutput. Rssvfmptloji of Operation Speaking at a recent conference, "Mr.G. d'Erlanger, managing director of B.E.A., said that numbers of Vikingswould be back in service by April 20th. The modifications had to be incorporatedin all B.E.A.'s Vikings, the production line had to be got going again, B.E.A.'spilots had to be checked-out again alter four months off Vikings, more provingflights would be made as a precaution, and, finally, agents and the public hadto be notified of time-table changes. It is chiefly due to the excellent com-bined team work on the part of Vickers and B.E.A. that the problems have beensatisfactorily solved in a few months. Many pessimists predicted a year's workfor solution. On the first two test flights, made onJanuary 25th and 26th with short-nosed Viking G-AHPG, Capt. James and Capt.Summers, chief pilots of B.E.A. and Vickers respectively, Mr. Edwards, chiefdesigner, Mr. Black of the Air Registra- tion Board, and Radio Officer Cox ofB.E.A. flew. Capt. James and his radio officer flew on every subsequent occa-sion, but were, on occasions, accom- panied by W/C. Lowdell, Vickers testpilot, Mr. Richards, also ot Vickers, and 1st Officer Crawford of B.E.A.
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