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Aviation History
1939
1939 - 0208.PDF
84 FLIGHT. JANUARY 26, 1939 A YANK at AGREAT many opinions have been aired recently on the subject of American aircraft and engines for the R.A.F.; the behaviour and performance of the first Harvard trainer, which has been delivered to No. 12 Flying Training School, Grantham, will therefore be sub jected to a very critical examination. The Harvard is the name given, for R.A.F. service, to the two-seater trainer built by North American Aviation, Inc., of Inglewood, California. Two hundred have been ordered. More Harvards are at present being assembled in this country, but delivery is temporarily held up as Mr. Burton, the American test pilot who passes them out, is unwell. Several minor modifications have been made to this machine as compared with its American prototype, but the main differences lie in the provision of a retractable under carriage and the fitting of a 530 h.p. Pratt and Whitney Wasp engine. There have been whisperings about the fixed leading- edge slots which are now fitted to the Harvard, but which were not to be found in the earlier North American B.T.g as used, by the U.S. Army Air Corps. It seems, however, that the flying characteristics of the type were never vicious, and it speaks well for the machine that while, even now, it " stalls on the clock " without over-much warning, those pilots who have so far tried the machine are looking for ward to their next flight. It is possible that the Harvard handled more sweetly under normal flying conditions with out the slots. The "eyebrow" slots, as they are called in America, are a quite recent addition and were devised by the Army Air Corps Material Division. The first order for some hundred BT-o. '' basic '' trainers for the U.S. Army Air Corps was completed in 1936, and at the present time another much larger order for slightly modified types is being executed for the U.S. Army and Navy. The Navy version of BT-gB is known as the NJ-i. The latest mark in the States is for Basic Combat or Fighter training. This machine has a Wasp engine and retractable undercarriage and resembles the Harvard more closely than do the rest. A.V.-M. L. A. Pattinson, Commanding Officer of No. 23 Training Group, said that some twenty-six of these machines are to be delivered to No. 12 F.T.S. at Grantham, to be used in the first place for training fighter pilots in their second (or advanced) term at the school. A normal course at this and the other Flying Training Schools follows imme diately after the ab initio training, and is usually divided into two terms of about thirteen weeks with fourteen days break between. Grantham's equipment up to date has consisted of flapped Ansons (camouflaged, with undersurfaces painted "training yellow"), but these are soon to be replaced for First North American "Basic" Trainer Delivered to the R.A.F. : The Harvard Described Although of reasonably small dimensions, the Harvard has commodious cockpits and, indeed, many other charac teristics found in larger and faster types. " Flight " photograph pilot training by Airspeed Oxfords in addition to the Harvards. As will be seen from the photographs, the Harvard is a low-wing tandem two-seater monoplane. It is of metal covered, welded steel-tube construction with fabric-covered control surfaces. The cantilever wing, made up in five sections, is built round a single spar. Both rudder and elevator are fitted with tabs which are adjustable from wheels in the cockpit. The undercarriage legs fold inward and upward. Armament consists of a Browning gun and a camera gun. In view of unsuitable weather conditions, the Harvard was not flown at the time of Flight's visit to Grantham. A creditable start from cold, using the hand-operated energy starter was, however, made (the starter can also be elec trically energised), and on opening the throttle the com bined phons emanating from engine and airscrew—at close quarters noisy to the point of being painful—seemed to justify the widespread comments concerning a yellow mono plane which has already attracted the attention of prac tically everyone in Grantham. A large number of neatly arranged controls and instru ments are displayed in the Harvard cockpit, and the traditional American ingenuity and thoroughness in tins class of work is apparent. Most controls and instruments are duplicated in the rear cockpit. A pilot passed out as thoroughly conversant with the Harvard and its equip ment should be ready to cope with any British Service type. The Power Plant The Wasp S3H1 9-cylinder direct-drive radial-engine is supercharged for moderate altitudes, and for take-off gives 600 h.p. at 2,250 r.p.m. The normal output at 5,000ft., with a crankshaft speed of 2,200 r.p.m., is 550 h.p. For take-off the mixture is set at full rich; for maximum level flight the air-fuel ratio is about If, 1, and for continuous cruising about 14: 1. The take-off boost registered in inches of mercury above zero is 36m. The normal boost is 32.5m., using 87-octane fuel. A Hamilton two-bladed 9ft. constant-speed airscrew is fitted, the master control being placed on the same quadrant as the throttle and mixture levers. These three, located on the port side of the cockpit, are all interconnected. The setting of the airscrew blades ranges from 27 deg. in coarse pitch to 11 deg. in fine. Three alternative methods of lowering the undercarriage are provided : the normal hydraulic system, a hand pump, and a lever which releases the catch of the top position lock and lets the wheels drop down and out. For normal operation the up or down position is selected on the main lever and momentary depression of a push button on the
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