FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1942
1942 - 0471.PDF
FEBRUARY 26TK, 1942 FLIGHT 181 1 Correspondence 7'hc Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers, • , not necessarily jor publication, must in all cases accompany letters. RANGE AND FUEL ECONOMY More Performance Equations ' I 'HE power factor question seems to have given rise to suffi- 1 cient confusion to warrant an attempt to get to the bottom of it. The powiir required for level flight is usually written --w B.H.P'. = — *T 550 D being drag and \ airspeed. Substitution from the ordinary formula? gives B.H.P. - £2- . —= C*,a 550 VsiP from which it is clear that power required varies inversely as V2ICD. - It is easily seen that this is not the same as L3,2/D, for the latter is (CLStpV*)»< r 3/2 r Vsip CDSjpV2 If V were regarded as a constant, unaffected by changes of C,., then L3,2/D would indeed be proportional to CL3'2/CD, and its maximum would indicate the attitude requiring least power equally well. But, of course, V is a function of CL, in level flight, and so we get T 3/2 r , _ D " C„ Z L Putting Vw for VL, wc see that L3'2/D is proportional to C/CJ, or tor L/D. This simply amounts to saying that L3'2/D = L/DVT = L/DVW" which is saying the same thing in different ways. Another approach is _to manipulate the horse-power formula until it reads , L3'2 55oVsC.Jp We might be tempted to suppose that this means that power varies inversely as L3/2/D, but unfortunately &, is also present, and the one is dependent on the other. The conclusion is that CL3'S/CD is the real power factor, L3,2/D having no particular significance in this connection. W. E. HICK. NO NATIONAL MONOPOLY American Public Being Misled "VTOTJR Editorial in the February 5th issue of Flight in reply -*• to some recent American claims for the marked superiority JjE their aircraft will, I feel sure, be received favourably 'throughout the British aircraft industry. The particular article in the December issue of Aviation mast have given rise to some amused astonishment over here. It is unfortunate, in my opinion, that you did not see fit to quote the passage which infers that because more Halifaxes than Fortresses have been lost, then Halifaxes must be in ferior. The author attributes the discrepancy to the high flying capabilities of the Fortress, whereas the truthful explanation is so obvious that you probably thought it un worthy of comment. However, it would have served to emphasise the species of argument on which the whole article was based. Incidentally, in all fairness, there is a misprint m the extract, "Me 109 Fs have engaged the Fortresses in combat at 40,000ft. . . ." This height should read 30,000ft.," according to the original in my possession. The statements quoted by you, and many others which have not passed unnoticed, contrast strangely with one made by the President of the United Aircraft Corporation in a lec ture to business men in Boston last Octobef, to the effect |j»at " Americans have an ingrained idea that everything fijD'ign is better than the domestic." Needless to say, that he continues with the assertion that the Fortresses in the R-A.F, are the " backbone of the long-range striking force." , I am also reminded of a recent advertisement in American journals which leaves the impression that one particular type of single-seater fightei has played, and is playing, a vital part lr > maintaining air supremacy over this island, when, in fact, it can hardly yet have reached operational status in the R.A.F. The American public are definitely being misled by such examples of high-pressure publicity. Surely there is one able writer in this country, well versed in matters aeronautical, who can spare the time to attempt, at least, to impress upon our cousins Over the water that, although conditions prevent us from disclosing details of our latest types, the R.A.F. dues employ some aircraft entirely of British design which have creditable performances and have even proved their worth in battle. A. ANDREWS. THE IDEAL FIGHTER Why Twin Tail Booms ? MAY I point out to your correspondent who suggested a D-23 tandem-engine-type fighter that the extra drag of two tail booms would be abolished, and all the other advan tages retained, with one exception, if a conventional aircraft using contra-props were adopted? The exception is that in this case the wheels could not be retracted into the booms; but I doubt if they could anyway, in the size of boom considered. Remember, the Fokker Company could not manage it! I feel the artist responsible for the prone-position aircrait (appropriately on page " g," Flight, February 12th) is much nearer the mark; but why twin tails? Both the Beaufighter and the Me 210 are, ,1 believe, single-finned; or go the whole hog and make it a tailless, as Gunter is reported to have done with the new Heinkel, and as Northrop has done in America. SIMPLICATE. Vulnerability UPON reading "2/Lt. R.A.'s" remarks on the "Ideal Fighter" in your issue for February 12th, it seemed to me that his criticism is a little one-sided. He stresses the magnitude of the complication of the airscrew gear through which the tail stresses must be carried, and the controls pass. But I think this is not as great as he makes out. In his version of the ideal fighter there is still vulnerability, from tail attack, to the rear engine, which he points out as a fault in central airscrews, and " buried " engines. He has not. as he admits, solved the problem of baling out, as there is still a rear airscrew. As for the pilot being exposed, does it matter much to the pilot whether he is trapped between the rear engine and some hard obstacle, or the rear engine and the front one, in the event of a rough forced landing? As for flying on one engine, or fighting, the former may be possible if the rear engine failed, but if the forward one failed the balance would be so much upset as to make flying, let alone fighting, very difficult. There are several other disadvantages: — (1) Great increase of weight, which would offset any advan tage in speed, since the fuel and the extra engine would mean such an increase the wings would have to be built larger to keep the loading anything like reasonable, consequently causing a lengthening of the tail booms and loss of speed. (2) Phenomenally small undercarriage units would be needed for stowage in the booms, since the main armament, and the tail unit controls, would have to pass there, causing much com- .plication. The fuel, armament and undercarriage are all out board, which would lessen manoeuvrability. The pilot's morale has not been increased by adopting his design rather than the "central airscrew" system. I do not think there are grounds for saying that the nose would cave in; if the nose of a machine can be built to hold .1 heavy engine in place for a crash landing, surely it could resist the same forces without the engine? A single sheet of armour plating is the best method of protecting the pilot, rather than introducing another engine to do so. The only advantage would seem to be that the radiators are, in his version, in the slip-stream, which suggests he has made the hand fit the glove rather than vice versa. He omits the disadvantage of a central airscrew—that the blades would be very difficult to feather. It seems to me that the disadvantages of the tandem layout offset any advantages gained. JUSTIN GREAI.Y.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
