The finding of K5, signifying the fifth hangar in K lines, afforded no difficulty. Already the machine was out, four or five mechanics being busily engaged in tuning-up the engine and testing the controls under the observant eye of a young officer, who, apparently bored stiff with the whole performance, was smoking a cigarette and fondling a terrier pup--but one of the small army of mascots maintained by the Averleigh T.D.S. Lieutenant Rippondene, Derek's instructor, was in appearance an overgrown schoolboy. As a matter of fact he was just twenty, and had been flying at the front for more than two years, until a piece of shrapnel had put a temporary stop to his activities in strafing the Boche. Until he could prevail upon a normally adamant Medical Board to allow him to cross the Channel again, he was being employed as flight-instructor to the quirks of Averleigh Flying School. He was full-faced, and showed a decided tendency towards corpulence. In his flying-helmet and leather coat he strongly resembled a jovial friar, and it would have been difficult to realize that those podgy hands were capable of keeping a shrapnel-torn "'bus" under absolute control. On one occasion he had been beset by five Huns, yet, according to the testimony of his observer, "the old merchant was grinning from ear to ear during the whole strafe". "Hop in!" was the Lieutenant's greeting, much in the manner of a motorist offering a youngster a lift on the road. Derek obeyed, clambering into the fuselage of the double-seater "Dromedary" by means of metal-shod niches in the side of the khaki-painted body. The instructor, throwing aside quite two-thirds of the original length of the cigarette, followed, and, dropping into his seat like a crab retiring to its lair, drew on a pair of gauntlets. "Right-o!" he continued. "Tell 'em to swing her." "Contact, sir--contact off," was the continued slogan of the air mechanic, as he strove to swing the large two-bladed propeller, or "prop." as it is invariably termed in the R.A.F. Nothing of the desired nature resulting, Derek turned and looked enquiringly at his instructor. Rippondene's face was wreathed in smiles, for his pupil had forgotten an elementary task. "You're doing the job, George--not I," he remarked. "Carry on, and make a move." At the next swing of the propeller the engine fired. Only the skids under the landing prevented the Dromedary from rolling forward over the ground. Now was the time for Derek to put weeks of theoretical instruction to the test. A touch of the throttle and the powerful engine roared "all out", the vast and seemingly slender fabric of the 'bus quivering under the strain, while the tyro pilot was almost beaten backwards against the coaming of the seat by the terrific blast from the rapidly-revolving prop.