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Aviation History
1939
1939 - 1828.PDF
JUNE 15, 1939 CORRESPONDENCE The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, not necessarily for publication, must in all cases accompany letters. VISIBLE VORTICES Interesting—and Spectacular—Aerial Phenomena DURING the public demonstration of the new Martin Baker aircraft at Heston, an extremely interesting phenomenon could be observed. When the machine was pulled up into a zoom from a pro longed dive, a brilliant white streamer could be observed trail ing behind the wing tips for some 6 or 8 feet. This is usually attributed to the deposition of water droplets along the centre line of the trailing vortices. The circulation (and therefore the strength) of the vortices is directly proportional to the load factor. In this case, nearly every condition was favour able: i.e., the small span and blunt wing tips of the machine; the high speed; and the high load factor. The velocity at the centre of these tip vortices rose to such a figure that the resulting low pressure allowed water droplets to deposit out of the air. This phenomenon is fairly well known, but notice of it is believed to have appeared in print only twice, after the last National Air Eaces held at Los Angeles in 1936, and during one Hendon Display. In each case the circumstances were the same. For the purposes of record, the atmospheric conditions at this time were : — Barometric pressure (station level), 1,026.2 millibars. Humidity, 46 per cent. Temperature, 59.8° F. I hope this will prove of interest. COMMONWEALTH. Heston. [Possibly the only case on record of such phenomena being recorded photographically is recalled by a Flight picture of the Hampden—one of the earliest of that machine to be pub lished, and taken about three years ago. In this instance the vortices clearly traced the path of the airscrew blade tips. The photograph is reproduced again here.—ED.] SOME C.A.G. SUGGESTIONS Lower Week-end Rates : Landing Practice : The Wearing of Uniforms I HAVE recently seen it stated that "one has only to go round the clubs at week-ends to see the difference that the C.A.G. scheme has made to their flying times." Or words to that effect. Whilst I quite agree that the C.A.G. saved the clubs, I do not quite see eye to eye with the remark " week-ends." I will explain wnat 1 mean. When thn C.A.G. was first started, the Commissioners, in order to stop overcrowding, recommended that the week-end charges should be double those asked for mid-week flying. This was a very good thing at the time, as it gave the normal club pilot, whose only chance of flying usually lay at the week-ena, facilities to carry on as usual—which he most thank fully did. In due course, the clubs got the scheme well under way and, of course, increased their number of aeroplanes. The result is that during the week these machines, together with their attendant instructors, are kept very busy, but at week-ends both spend quite a fair percentage of time on the ground, owing to the fact that the C.A.G. members do not relish the idea of paying double what they do during the mid-week, and the normal club members are not enough to keep the increased fleet and personnel very busy. Therefore, with a view to increasing both the club flying times and the number of C.A.G. members trained, I would suggest that the Commissioners, or whoever are responsible for the matter, should consider reducing the week-end charges to something approximating those of the mid-week. It could be left to the management of the clubs themselves to see that the old member was not crowded out. After all, he can always hook his machine with the others. Another point which I think ought to be considered is that of the time allowed for the training of C.A.G. members. At the moment, their instructors have to decide whether or not an individual pupil is going to be any good after he has done something in the neighbourhood of six hours flying, with this result : By the time these six hours have elapsed, the pupil has reached the circuit and landing stage and is not yet very good at it. To perfect himself in this, the most difficult part OOT? The Flight photograph referred to in the Editorial footnote to "Commonwealth's" letter. The vortices visible at the airscrew tips have been very slightly touched-up for repro duction purposes, but they are just as clearly visible in the untouched original, and the picture is in no way "faked." of the flying instructional sequence, he needs a lot of con centrated practice, allied with calm weather, which latter is not very prevalent in this England of ours. Our Cag-pupil duly arrives at the aerodrome on a beauti fully fine morning, only to be told that it is not good enough for him to practice landings as the wind is a little gusty near the ground, and as his hours are already getting high he had better wait until the weather is calmer. So he waits, mean while seeing the "ordinary" club pupil, who is paying full rates and whose hours to go solo are, more or less, unlimited, carrying on as usual. Therefore, the Cag may be forgiven if he cultivates a slight inferiority complex which in itself will slow up his own aptitude for learning and he consequently takes longer (in flying hours) to go solo, as well as in time wasted during the days he has to wait for the "perfe.t" flying day. And when he has gone solo, what is the use of a pilot who can fly only in the calmest weather? It's not very nice for the poor Cag instructor either ; he has either to keep his pupil on the ground, or risk him being turned down by taking too long to go solo ! So another point for consideration seems to be that of the flying time allowed for a Civil Air Guard member to show signs of coming proficiency. Nowadays it is compulsory for Cag members in training to wear their uniforms, which, to my mind, is all to the good, despite the appellation, "Civil." But certain of us who have been flying for some years have taken the Instructors' En dorsement, and are busy training the young idea. As they mainly consist of Cag members, I always make a poirfc of wearing my unilorrn whilst flying. Strictly wrong, I believe, according to the book of words, but, nevertheless, it creates quite a good impression with the "boys." I think that those who wish to wear their uniforms whilst teaching the new members should be allowed to do so, and should wear some distinctive insignia to show their position. I've heard a lot about "starring " the more experienced, but so far have not seen any visible results ! CAG INSTRUCTOR. London, W.C.i. SOLO BEFORE DUAL A Common Experience for the Glider Pilot I WAS interested to read the entertaining article in Flight last week on the Cag who went solo before he flew dual. Such experience is, however, often the lot of the glider pilot, who goes solo from the earliest stages. Soaring flights of ten or twelve minutes are sometimes made by pupils whose previous total flying time is well under that figure. The late Eric Collins must have counted his solo hours in sailplanes by the score before he flew dual in a power plane. The instruction—I believe—continued for some forty-five minutes before he took off solo. Even so, there are some who say that the lesson lasted thirty minutes longer than necessary. London, W.8. MALCOLM LOGAN.
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