FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1945
1945 - 2003.PDF
392 FLIGHT OCTOBER IITH, 1945 TEST INSTRUMENTS investigating the transition of laminer into turbulent airflowover wings and airscrew blades. It is a chemical system which entails the wing or airscrew surface under consideration beingsensitised \>y a mist spray of potassium-iodide, starch and hypo, which becomes smooth and dry. A trail of weak chlorine islaid alongside a. trail of coloured smoke by an aircraft flying about one mile ahead, and the aircraft to be tested is flown byits pilot along the path of the coloured smoke, so ensuring that the machine flies through the trail of gas. Areas of turbulencecause a surface darkening of the chemical treatment and by so doing illustrate the position and area of breakdown. Thisis applicable not only to normal airflow characteristics, but also embraces boundary layer characteristics.In connection with the latter the small dimensions of the boundary layer on low drag wings enables the profile drag tobe measured in flight by means of a small vertical comb fitted behind the.trailing edge of the wing. The prongs of the combare pitot tubes, and the small size and weight of this installa- tion makes it particularly applicable. To enhance the efficiency of airscrews and so stave oil fora time their eventual eclipse by direct-reaction propulsion, an installation exhibited on a Spitfire incorporates a calibratedengine, and horizontal combs projecting from the nose immedi- ately behind the airscrew whereby a measurement of the totalhead can be made in order to determine airscrew efficiency. Special apparatus incorporated includes (i) total head combs;(ii) pitot-static head designed for high speed with large-bore tubes to reduce lag; (iii) differential pressure gauges with arange of 4m. w.g. and giving scale readings of 0.02 w.g.; (iv) underwing electrical thermometer connected to Tinsley re-flecting galvanometer giving lagless readings to \ deg. C.; (v) airscrew pitch indicator of Desynn type reading to aboutI deg. Readings are given on a grouped panel of dials and recorded by a high-speed Vinton camera. Structural Section In the structual section of the exhibition many of the instru-ments were electronic embodying photographic recording of the cathode oscillograph traces, and included vibrographs, reson-ance testing equipment and vibration recorders of various types. Of the strain recording equipment, a very interesting exhibitwas a 16-channel mobile recording set of de Havilland's which provides input connection for resistance strain gauges or electro-magnetic vibrographs, connected in two groups of 16 each from 32 input circuits. After amplification, the signals are appliedto the galvanometer unit of the recording camera. This exhibit included a de Havilland four-blade hydromatic airscrew towhich the "pineapple" hub strain gauge and cemented pick-ups on two blades were fitted, the whole being erected Excitation of model airscrew blade to give sand patterns according to type, location and area of particular strain. in a stand and the excitations recorded by the equipment.* Another very interesting exhibit was the six-channel cathode- ray oscillograph recording equipment which is likely to becomestandard for the industry, having been designed as standard for multi-channel recording during ground tests. It is made up ofa main tube and camera assembly which houses six cathode- ray tubes and the six amplifiers, and two racks housing pre-circuits and calibrating and timing gear. The equipment will measure steady and fluctuating strains by means of resonancewire strain gauges, and vibration amplitudes and velocities by means of genera tor-type pick-ups. Automatic calibration isprovided together with variable-frequency timing marks and provision for phasing marks. Range is quite wide, frequenciesfrom 0-10,000 cycles per second being recordable; this is all the more interesting when it is realised that great difficulty isexperienced in getting down toward zero frequencies. For indicating the strain distribution in airscrew bladesanother device employs a i/ioth scale model of the blade, which is set in forced vibration by an electro-magnetic exciterfed with AC of variable frequency from a 200-watt power amplifier driven from an audio-frequency oscillator. Fine sandis sprinkled on the model blade and is shaken into individual patterns according to the frequency of excitation. Although, for reasons of space, we have here given only abrief resume of some of the more interesting exhibits, the show was remarkably comprehensive and absolutely up to date. Theauthorities concerned are to be congratulated on having the foresight to recognise the great deal of good which can onlyaccrue from such a function. ONE-MAN ARMY WITH ATOMIC BOMBS A GRIM picture of a future war was painted by Air Vice-Marshal I). C. T. Bennett in an address on the atom bomb and civilisation to the London Institute of World Affairs lastweek. It it were wrongly used, he said, the Prime Minister ofEngland, sitting in a control room at 10, Downing Street, could declare war by releasing 6,000 atomic rockets on the enemy. " By pressing a button he would destroy every major towntn the country he was attacking," declared Vice-Marshal Ben- nett. This suggestion of a one-man army is no wild figmentof the imagination, but is possible with the knowledge avail- able to-day." Even if they were to live 5,oooit. under the ground theywould not really be safe, as bombs could be devised with enor- mous penetrative powers. All other weapons were out of date.The smallest atomic bomb would bring about as much destruc- tion as took months of struggle with the old weapons. Itwould mean a Passchendale every day. "The tragedy is that this new wenpon is fifing used in thegame of power politics," said the Air Vice-Marshal. "As long as it remains in the hands of one or two nationsI am quite sure we are heading for another war." They must see to it that the atomic bomb was handed overto an International Authority which would use atomic energy to make life easier " One scientist could make a little countrygreat in power by bringing about a little improvement of the atomic bomb, and he could destroy a great nation like theU.S.A. in five seconds," he said. "The whole balance of power has been upset by this discovery, and in future the bignations would no longer be all powerful." BOMBER COMMAND TRANSPORTS TROOPS SINCE August 1st, Lancasters of R.A.F. Bomber Commandhave been engaged in a regular transport service to and from Italy. About 60 aircraft a day are employed. To date, 44,000 troops have been brought to England and3,000 taken back. Some of the men were coming home on release and others were on a month's leave. The Lancasterscarry 20 passengers and land at Pomigliano and Bari in Italy. The journey from England takes between six and seven hours,and the air crews are given 24-hr, rest in Italy before returning. Three aircraft fly to Berlin each day taking air crew and afew of the grand staff to see the bomb damage and conveying Service personnel of the occupying forces who are going onleave. A.T.C. AN INTEGRAL PART OF THE R.A.F. AT all places visited, co-operation between the R.A.F.stations and the Air Training Corps was excellent, and the Air Training Corps is being regarded more and more as an 'Aintegral part of the R.A.F.," says Air Chief Marshal Sir Robert Brooke Popham in a report on Air Training Corps for 1945. Sir Robert and three other senior R.A.F. officers have justcompleted a series of inspections of stations where over 60,000 air cadets have been undergoing their week of annual trainingunder service conditions. The inspecting officers found that at most stations it wastaken as a compliment to the Corps that '' any failure on the part of the A.T.C. to live up to its high reputation for smart-ness and good discipline comes in for criticism" as though they were full members of the R.A.F.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
