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Aviation History
1944
1944 - 0567.PDF
/ MARCH I6TH, 1944 FLIGHT 293 CORRESPONDENCE The Editor does not hold himsell responsible for the views expressed by correspondents. The names and addresses of the writers. not necessarily for publication, must in all cases accompativ Utters. JET PROPULSION OF AIRCRAFT A Fourth " Dimension " Y OUR editorial note (Flight, February 24th) to Stuart Watts letter is, I suggest, incorrect. " Action and reaction must be opposite and equal" is the oldest of the Newtonian laws. Therefore, the jet must act on both aircraft and atmosphere. Stuart Watts' explanation of a punctured balloon is not correct; the reason that it would travel in the opposite direc tion even in a vacuum is that individual molecules would gradually slow up and thus form an abutment to the succeed ing ones. This would continue until the balance was reached and thus thrust it forward. S. H.-A. [We suggest to this correspondent that if this view were correct, a rocket would not work in a vacuum.—ED.] Gunpowder as a Fuel ? THERE is a lot of "joy" in gunpowder, so-one notes from your very helpful articles on jet and rocket propulsion. And your obedient servant lias had one of his rare bright flashes Clearly, gunpowder is useful fuel for direct reaction pro pulsion, since, by its literally colossal expansion upon com- •(ftistion, it makes available large amounts of energy in brief units of time—in short, it can do a lot of work. Now the following assumption is the basis of the brilliant flash—namely, that the expansion of a pound of gunpowder is considerably greater than the expansion of a pound of spirit fuel (duly mixed with air). If this assumption be wrong— and a poor memory aided by no reference book may well make it so—then may this letter be consigned forthwith to the " mis conceptions " file. But if it be true, why not gunpowder for "joy" in orthodox aircraft (or, for that matter, midget sub marines or any other engine-propelled contraption) ? Thus, a series of charges (small or large, to suit all tastes) fired into a '' pressure tank,'' whence the gases can be allowed to gush forth at any convenient rate through any convenient type of pipeline to drive any convenient type of engine, turbine or reciprocating.. The gunpowder charges could be bell-fed, like bullets, and fired every time the pressure in the '' lank '' falls below a desired figure by a simple pressure-valve trip-lever. For the rest, it works as though the medium were steam. The advantages seem numerous:— (1) Providing tile aforesaid basic assumption is true, very great saving in fuel weight. (2) Entire independence of atmosphere—i.e., no super charger to lug around the sky (weight) or to drive (power). (3) Providing the previous flight did not terminate through exhaustion of the pressure in the tank, "starting up" is instantaneous: you just turn on the tap. (4) The "mixture" is entirely nou-flam (as Wardour Street would have it), and there is no reason why the "ammunition," firing mechanism and pressure tank should not be 'way back in the part of an aircraft which ^_ usually survives a crash—at any rate, away from the "" hot engine oil—that prime aid of Satan. Since orthodox forms of propulsion in the air are bound to endure a couple of decades more at least, the idea seems better ever ' time it is reviewed: so much so that the odour of a rat is apparent in the fact that it is not already in general use. Though one can think of none, it seems there is a snag some where. Is there? "DRIVER." FINNED TUBES Many Advantageous Uses T NOTICED with interest your suggestion in Flight, February -*- 17th, of a gas turbine power plaat, and with reference to previous correspondence I add my observations. I believe it to be to our advantage to make use of ribbed cooling surfaces in the construction of air ducts and other heat exchanger problems. The exchangers can be so designed, in tubular form, that the medium to be treated is guided over the external fins, and the acting agent through the bore of the tube. The process can, of course, be reversed. The drawing shows the type of tubes indicated. Again, for de-icing, finned tubes are admirably suited, when applied in the same manner as suggested years ago. With regard to your item headed "Ju88 Gadgetry," in " Here and There " of the same issue, the answer to the query is that the type of fastening used is the most simple and positive both from the angle of application and production. I designed exactly the same thing in 1938, the patent ua applied for, and I suggest more use of this type of fastening. J. F. HEXDKIK RENAKD. THE WORLD'S BEST AIRCRAFT A Pardonable Error M AY I use a little of your space to criticise Mr. Masefield's choice of the world's best aircraft ? First, it must be remembered that while we Britishers hold back information on new types, the Americans tell the work I about them before even the prototype has flown. To take one example. In the category of high-altitude fighter he has compared the Mustang II with the Spitfire IX unfairly because the Spitfire IX is of the same period a's the Warhawk and the Mustang I, to which it was superior. The Mustang II should be compared with the new British fighters, the names of which cannot be given for security reasons, which are definitely better than the Spitfire IX and Typhoon, and consequently tin- Mustang II. Similarly, in the low-altitude category I ani convinced thai the clipped-wing Spitfire IX would out-manoeuvre the Mustang 1; in fact I have seen it doing so. Then I feel sure that the Typhoon IB would make a bettei show as a fighter-bomber than the Lightning. Both carry 1,000 lb. of bombs, and the Typhoon is superior in fire power, speed and manoeuvrability. Fourthly, he does not even mention the York in the long range transport class. Although it is probably no better than those mentioned, T think that it is at least equal to them. Any way, I consider the Constellation superior to the Skymaster. Why Mr. Masefield does not consider the night-lDterceptoi worthy of inclusion is indeed a puzzle to me. Also, if that class were included, I certainly consider the Mosquito 11 superior to the Beaufighter. The latter is a fine aircraft, but is not fast enough for present-day requirements. The Messer schmitt 210 and 410 could easily outpace it, and the Junkers 18.S and the Dornier 217 would give it a good chase. Taken all round, though, Mr. Masefield's article is a good one, and as everybody feels a certain amount of patriotism we cannot blame him for including more American types than British. R. E. GREGORY. [Our correspondent makes a pardonable mistake in sup posing Mr. Masefield to be a patriotic American; he is British -ED.] TYPHOONS v. JUNGMANNS Fighter Pilots Not Criticised W E are sorry to see that apparently "Junior" (Flight. March 2nd) had a spasm of short-sightedness when read ing Ian S. Alexander's letter on the subject of " Typhoons and Tungmanns " (Flight, January 20th). How also could he have missed seeing the words "sordid necessity" at the head o) the said letter? How else could he have overlooked the entire second paragraph in which the writer plainly stated that unfair as it may seem, training machines should not be spared? Mr. Alexander's letter conveyed to us no criticism of the Typhoon pilots, but merely of the newspapers', and B.B.C.'s, treatment of the incident. With regard to "Chief Test Pilot's" letter (Flight. February 3rd) on the same subject, we bow to his superiot knowledge, but we would make two observations. First, is
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