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Aviation History
1937
1937 - 0430.PDF
168 FLIGHT. FEBRUARY 18, 1937. Private Flying SOUTH COAST . • — , . Better weather enabled the Club to do over 40 hr. flying last week. This is a record since last summer. An informal dance is being held at the Club on Saturday next, the 20th. EASTBOURNE Two " A " licences were taken during the month of January by Miss Strodle and Mr. Eric Ellis, and the number of hours ilown for the month amounted to 41 hr. 5 min., despite the very unfavour able weather conditions. Since 1933 some thirty-four " A licences have been taken under the instruction of Capt. H. A. Love and there is a total membership of 180. Improvements are now being carried out, including extensions to the clubhouse and additional hangar accommodation. NORTHAMPTONSHIRE During January members of the Northamptonshire Aero Club flew twenty-nine hours. Miss B. E. Benson has gone solo and is now making headway for her " A " licence. Mr. J. W. Wilkinson, who has his " A " licence for Autogiros, has now done all' the tests for the fixed-wing type of aircraft. Mr. Gallagher has also completed his tests for a licence to fly ultra-light aircraft. The next Club dance will be held on March 5, and the annual general meeting will be held in the clubhouse on FViday, March 12, at 7 p.m. New members welcomed during the month include Miss J. K. Bull, Mr. and Mrs. Woodman, and Messrs. G. S. Bull, H. G. White, and the Hon. A. Ycrney Cave. CINQUE PORTS New members joining the Club last week were Mr. Knight, from the Small Arms School, in order to obtain his " A " licence, while Mr. Brand went down Lympne for final polish on the Club's Tiger Moths before going to Hendon for his " B " tests; he also intends to do his night flight with the Club. Messrs. J. A. Reid and J. C. BrHwr have successfully completed the tests for their " B " licences. A foreign visitor during the week was Mr. Provost with friends from Belgium in the former's Leopard Moth. He is off to the Egyptian Rally and wanted a special check on his machine before starting. Another visitor was Mr. G. Gardner, who landed at Lympne on Friday about midday, having been to Paris and back that morning in his new Beechcraft at an average speed somewhere in the neighbour of 190 m.p.h. Biickers for Zurich T HREE Bucker Jungmeisters should by now have left for the International Aerobatic Contest at Zurich. Each is fitted with S.H.14A (presumably Siemens) engine. Incidentally, the Dornier Co. have obtained a licence to build the Jungman at Altenrhein, in Switzerland. Not at all Technical FOR some reason or other the annual D.H. Technical School ball always provides one of the very best opportunities for certain sections of the flying fraternity to get together. This year the event coincided with the A.I.D. dinner and there were certain notable absentees, but the number of guests (self-made and otherwise) was so satisfactorily enormous that these absentees were only noticed towards the end of a very pleasant evening. Incidentally, the entertainer, who, among a number of other light-fingered tricks with cards and so forth, managed to remove a guest's braces without his knowledge, would be a useful addition to any aircraft factory. He could, for instance, remove the bugs from some new type without the knowledge of the design staff—who usually doubt the presence of these small insects. COMPASS ERRORS EXPLAINED The Why and Wherefore of the Various False Indications ATOT every instructor and compass expert will agree with the pitching and acceleration error explanations given in this short article The whole subject, however, is one which is rarely dealt with in useful detail, and the explanations are at least interesting. DURING straight and level flight at a constant airspeed, the magnetic compass" will always give accurate indica tions, but any departure from these conditions may, as every pilot knows, cause the compass to give false read ings. These errors are caused by alterations in the machine's course, speed or attitude, and a brief description of the forces to which the air compass needle system is subject will simplify the explanation of these errors. In Britain, if a magnetic needle is suspended at its centre by a thread it will not lie in a horizontal position, but its northern end will dip down. In the Southern Hemisphere the other end would dip, and at the Equator the needle would be horizontal. The amount of dip increases as the needle approaches the magnetic poles of the earth. When a compass needle is mounted so that it already lies in a horizontal position the vertical force is always acting upon it, and it will dip at the first opportunity. In addition to this vertical force, there is the horizontal force which is used for direction-finding. This directive force, as it is called, is also variable, being greatest at the Equator and least at the magnetic"poles. The vertical force is overcome in the case of normal com passes by suspending the needles so that they are below the pivot point, making the system pendulous. Gravity then neutralises the force so long as the needle system is not tilted. When a machine is turned in flight an error is produced, and the extent of this error depends upon the direction in which the turn is made and the amount of bank applied to the machine. It is at a maximum on steep turns through North or South, and at a, minimum on slow flat turns through East or West. The reason for this is simple. In a normal turn the machine is banked and the compass and its needles also bank. This means that the needles are tilted out of the horizontal, so that their North ends are pulled downwards by the earth's vertical force and the needles rotate around the pivot. Consider a turn from North-west through North to North east, i.e., to the right. The aeroplane is banked, port wing high and the north ends of the needles move downwards, also to the right. If machine and needles turn at the same rate, as m a normally banked turn, then no turn will be shown on the compass. In a very steep turn the needles will even turn faster than the machine, and a turn in the wrong direction will appear to be being made. If the turn is made without bank a similar effect is produced, for the needle system skids out wards from the pivot and tilts, with the high side on the outside of the turn as in a banked turn. A turn in the correct direc tion is shown, but it appears to be of a small amount. On all northerly turns, in fact, the compass appears to be sluggish. On southerly turns the opposite effect appears and the com pass quickly responds to the slightest movement of the controls, always showing a greater turn than that being made. The cause is exactly the same as for northerly turns, i.e., the tilting of the needle system. Consider a turn from South-west through South to South-east, i.e., to the left. The aircraft is banked and immediately the North ends of the needles are drawn down wards, showing an apparent turn to South—in the correct direction. Similar reasoning to that used for northerly turning error shows that on all southerly turns the compass over estimates the turn. Acceleration and Pitching Errors due to a change of speed are most pronounced when steering East or West by compass, and are negligible on northerly or southerly courses. Consider what happens when a machine, which is flying East, increases its speed. Because 01 its inertia, the needle system swings backwards away from the pivot. It tilts with the higher side aft. The vertical magnetic force draws the North ends of the needles down, so they swing to the right, or to East, which makes the machine appear to be turning to North. A reduction of speed will have the oppo site effect—an apparent turn to South being shown. On westerly courses similar effects are observed—acceleration caus ing an apparent turn towards North and vice versa. Pitching error is also observed for the most part on f^™^ or westerly courses. When the nose of a machine rises trie needle system is momentarily tilted out of the horizontal ana the North ends of the needles are dragged downwards towarus the tail. An apparent turn towards South is registered, simuai to that caused by a reduction in speed. When the nose_ laiis, or the machine goes into a glide, the opposite effect is snow . The fact that acceleration and pitching downwards (orue celeration and pitching upwards) cause errors in tne s . direction means that when these occur simultaneously effect is very great and a very big error may arise. These errors occur only at a time of change—cftan_e course, of speed, or of attitude. When steady conditions ar resumed, the compass will always register correct!>"' yRAY
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