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Aviation History
1943
1943 - 2115.PDF
AUGUST 26TH, 1943 FLIGHT *37 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. , SUPER-SONIC SPEEDS Can an A.S.I. Estimate Them ?S INCE an air speed indicator is a barometric or "pressure" instrument, calibrated (at least basically) in accordance with the "velocity squared" formula, it is difficult to see how super-sonic speeds can be estimated with such a device. From the point of view of recording air speed, the problems brought about by compression of the air at these velocities must be staggering, yet one hears of aircraft being dived at speeds up to 780 m.p.h. Surely, the figures mentioned are, to a large extent, arrived at by pure guesswork? "TOOLMAKER." DIHEDRAL Plea for Standardised Terms TN reference to your paragraph on "dihedral" in Flight, -«- August 12, it is suggested that terms in general use in ^viation circles be standardised from an international stand- )int. This would do much to eliminate friction, confusion and ^bigii in post-war commercial aviation in which inter- national airlines will predominate. For the word '' dihedral'' might possibly be substituted the term '' V-form '' without in any nay confusing the popular use of the V sign (V for Victory). Many international designers and constructors of aircraft'are already familiar with the expression "Vf" as denning the upward angle of a wing "V-form,from the horizontal. W. REGINALD DAINTY Hon. Capt., R.A.F. (R.N.), Ret.). M BOMBER ARMAMENT Losses Mostly Due to Night Fighters ? AY I intrude upon your columns again and reply to a pairof letters in Flight of July 15th? Mr. C. C. Cowen states that production of 0.303m. machine guns and the accessoriesis in full swing and that to change to larger calibre machine- guns would interfere with output. This is surely a very poorargument. If we pursued this policy in regard to aircraft types our Air Force would soon be equipped with second-rate aircraft.Jf we chose the 0.5m. machine gun for our revised arma- -jK~nt we would meet very few production "snags." The0.5m. machine gun is already in existence and has proved its worth in action. A fine example of the ease with whichan established product can be produced in another country is the Rolls-Royce Merlin aero engine. These are successfullyturned out in America with only a handful of British Rolls- Royce technicians present. Tho nose armament of the Halifax has been reduced to givebetter streamline form. Experience showed that nose attacks rarely develop. In the case of the Halifax II series IA thetotal armament is greater than on earlier versions. Since my last letter appeared in Flight, another variant ofthe magnificent Mosquito has been announced. This is a version of the Mark II and carries a bomb load of I.OOQ lb.in the rear sectioii of the bomb bay in addition to four 20 mm. cannons and four o.3o3in. machine guns. This is the firstannounced type of Mosquito which carries both bombs and armament. Imagine the value of this redoubtable weapon.Long range, high speed, heavy armament, bomb load, sturdy construction, magnificent flying qualities and manoeuvrabilityare all combined to form a war-winning aircraft of the highest quality. Are not low-level attacks by these aircraft as devas-tating as high-level attacks by the Americans? In the low-level attack the bombs can be placed on a smalltarget, causing grave dislocation and damage. This does not mean that I am running down the high-level attacks entirely. For area bombing of important targets with balloon barrages high-level attack is best, but if a smalltarget has to be plastered the low-level bomber will do the trick better. For such attacks the Mosquito and Typhoon are1 minently suitable for long and short ranges respectively. The low-level attack is immune from heavy anti-aircraft fire,and one who has seen a fast low-flying aircraft will realise the difficulties with which the ground light A.A. gunner hasto contend. I would now like to comment upon some points made by Mr. V. Redman. He puts forward his arguments very well,but there are one or two flaws. He says that if Fortresses attempted night raids into theRuhr they would have to fly singly and that their o.5in. machine guns would afford no protection against the manyGerman A.A. guns. This ignores the fact that the Luftwaffe puts many night fighters into the sky on the nights we makeheavy raids. These fighters take advantage of the light arma- ment of our bombers. It is remarkable that our losses are notgreater, but they could be still further reduced if our "heavies" had greater armament. I am prepared to warrantthat the majority of our night bomber losses are due to night fighters. It was stated in a London newspaper on July 15th that onthe previous day a secret debate on British heavy bomber armament had tajken place in the House of Lords. Thereforeit seems hopeful that something is being done about this vital question, but I would have felt happier if that debate hadbeen between leading British aircraft armament experts. A. T. HENSHAW. ELEMENTARY FLYING TRAINING Vertical and Horizontal Components WITH reference to Mr. N. Gilson's letter in your issue ofJuly 29th on climbing and gliding turns as explained in Elementary Flying Training, it would appear that the authorof that otherwise excellent handbook has not taken account of the direction of the vertical component of the relativeairflow. In any spiral turn an aircraft has a particular vertical velo-city and also a rotational velocity. Since the aircraft is rigid this means that each wing tip has the same vertical velocity,but that the outer tip has a higher horizontal velocity than the inner. Hence, the resultant airflow at the inner tip ismore sharply inclined to the horizontal than that at the outer tip, as shown in the following diagrams: — HORIZONTAL COMPONENT HORIZONTAL COMPONENT- VERHCAI COMPONENT OUTER TIP FIG I GLIDING TURN NOTE OUTER TIP INNER TIP FIG.2. CLIMBING TURN NOTE B=-A The writer of Elementary Flying Training has failed to realise that in a climbing turn the vertical component of the relative airflow is downward and in a gliding turn upward. In a climbing turn, then, the angle of attack is decreased at both tips, but most at the inner tip, hence the aircraft tends to roll on to the turn and must be held off. In a gliding turn the angle of attack is increased at both tips, again most at the inner tip, hence the aircraft tends to roll off the turn and must be held on. In each case the fact that the outer tip has a higher resultant velocity means that in any turn, flat or spiral, there is a tendency to roll on to the turn, which increases the above effect in the case of a climbing turn, and partly counteracts it in a gliding turn. To sum up, we have: (1) Gliding turn—hold on gently. (2) Climbing turn—hold off hard. (3) Flat turn—hold off gently. Hoping this,is a correct explanation. JAMES R. PALMER.
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