There is no gainsaying that stunt flying, or aerial acrobatics, was absolutely essential to the flying of scout and combat machines in the Great War, for in order to survive in the war in the air it was necessary for the pilot to be able to manœuvre and dodge about in the sky as easily as a fish in the water; otherwise, the flier would be shot down by a more agile machine or clever aviator. Clouds offered such excellent cover for aeroplanes to ambush unsuspecting novices, and decoys were often placed to induce some adventurous combat machine to dive down on the decoy, only to find that a formation of five or more aeroplanes were diving down on him. To escape from such a predicament required knowledge of all the manœuvres an aeroplane could possibly make. [Illustration: Diagram showing the stages of a “tail slide.” 1. Normal flying position. 2. Preparing to “stall.” 3, 4, 5. The machine falling by the head after being “stalled.” 6. Straightening up. (Alternatively it could have continued its dive.) The evolution of a “spinning dive.” 1. Stalling the machine. 2. The machine falling by the head. 3. Gyrations of a “spinning dive.” Diagram showing how an “aerial skid” is effected.] Moreover, every pilot ought to know how to perform these stunts even in peace-time flying, so that, if his engine stalls and he falls into a spinning nose dive, he will know just what to do in order to get out of it. The same is true of banking, side-slipping, etc. Finally, since an aeroplane moves through the air as a submarine passes through water, it should be designed so as to be able to take stresses from every quarter, so that if the machine loops or flies upside down a vital part will not break because the pressure is reversed. Stunting should never be performed less than 2,000 feet above the ground. It has been done by reckless pilots in exhibition flights countless times with impunity; nevertheless, many of the most daring and clever pilots have lost their lives just by taking such foolhardy chances. Altitude is absolutely essential to recover equipoise necessary to a safe landing, especially when a forced landing must be made. Eventually a law will be passed preventing, on pain of forfeiting of a license, looping, spinning, etc., below a certain altitude. The result will be a decrease in the number of flying casualties and a proportionate increase in the confidence of the public in the aeroplane as a safe and sane medium of aerial transportation. A VERTICAL BANK This term is applied to all turns or banks made at 45 degrees or over. With proper speed there is no particular danger in this manœuvre, and is performed by putting the rudder and control lever farther over than in an ordinary turn. To come out of a vertical bank is to give opposite rudder and to pull the control lever central again and slightly forward. When the machine continues around the circle it becomes a spiral. SPIRAL