Owing to the fact that a pilot must have altitude in order to get out of a nose dive, it is well not to try them near the ground. The pilot should be well strapped in so as not to be thrown forward on the controls. It is made by pulling the nose straight down. The engine should be shut off to minimize the strain on the machine. Many nose dives end in a zoom, and they were very common performances in air duels. A machine whose wings are not sufficiently strong may fold up like a book when levelled out at the end of a dive and crash. IMMELMAN TURN This stunt consists of completing the first half of a loop, then turning the machine completely about and facing the other direction. This manœuvre was named after the famous German ace. The engine can be cut out when the machine turns about and dives. The cart-wheel, boot-lacing, falling leaf, the roll and the barrel are all parts of this same stunt, and are often mistaken for one another. The cart-wheel is done by diving or getting up speed, then making the machine zoom. When the aeroplane is almost standing on its tail, but before it has lost flying speed and controllability, the rudder forces the ship into a bank in the same direction, forming a complete cart-wheel, coming out and facing the opposite direction. [Illustration: Diagram illustrating the reversal of position effected by a “loop.”] [Illustration: Diagram illustrating the execution of the so-called “Immelman turn.” 1. First position of the machines. 2. The forward machine preparing to turn over. 3. Partially over. 4. The forward machine upside down but still travelling forward. 5. Beginning the dive. 6. Completing the dive and straightening up.] The falling leaf is done by a modification of this manœuvre, causing the machine to fall over on one wing-tip, and then bringing it into control again, thus causing the machine to turn over like a leaf in the air. This is a hazardous manœuvre, and requires pulling the rudder violently from side to side. Upside-down flying and tail spinning is difficult except to certain types of machines; of course it cannot be done for any length, and usually terminates in a tail spin, when the machine descends like the threads of a screw. Naturally, there are air disturbances about a machine when performing these stunts, and bumps are frequent owing to that phenomena. They ought never to be tried by a novice close to the ground. They are, however, very spectacular, and for that reason often seen at aerodromes or flying exhibitions. Indeed, Lieutenant B. C. Maynard has a record of 318 consecutive loops. FORMATION FLYING