Flight, January 26, 1939

A YANK at RANTHAM
First North American “Basic” Trainer Delivered to the R.A.F. : The Harvard Described

   A GREAT 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 subjected 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 undercarriage 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.9 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 forward to their next flight. It is possible that the Harvard handled more sweetly under normal flying conditions without 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-9 "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-9B is known as the NJ-1. 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 immediately 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 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 electrically energised), and on opening the throttle the combined 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 monoplane which has already attracted the attention of practically everyone in Grantham.
   A large number of neatly arranged controls and instruments are displayed in the Harvard cockpit, and the traditional American ingenuity and thoroughness in this 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 equipment 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 boo 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 11:1, and for continuous cruising about 14:1. The take-off boost registered in inches of mercury above zero is 36in. The normal boost is 32.5in., 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 hydraulic selector valve then starts the movement. This same valve also operates the flaps in a similar manner.
   Three indicator devices are used in connection with the landing wheels. As usual, an electric horn sounds if the throttle is closed below 1,000 r.p.m. with the wheels up. A switch is, however, provided to cut out this warning in case it is desired to close the throttle during flight, and in this case the circuit is automatically reinstated to normal working order on raising the engine speed to about 1,200 r.p.m. Red and green warning lights appear on the panel, these having an intensity control so that bulbs powerful enough to show in daylight do not dazzle at night. Two small indicators painted red on one side and green on the other give a further visual indication of the position of the wheels to supplement the lights. To prevent accidental retraction the control lever must first be pulled upwards before it will move rearwards.
   In the case of an emergency lowering of the wheels, the bottom catches may not engage until the aircraft is rocked laterally. If this expedient fails an emergency plate at the forward end of the lever quadrant is moved aside and the lever pushed forward an extra two inches or so to operate the lock manually.
   Split trailing-edge flaps are attached to centre and outer wing sections. These are fitted with indicators and have an operation lever of square section on the same quadrant as the landing wheels. They may not be lowered at speeds exceeding 126 m.p.h., and for take-off are normally set at about 15 deg.
   Several heating and cooling devices are fitted. The cockpit has a warm air supply pipe, the induction air intake has a hot-cold control lever, permitting very fine adjustment in order to combat possible icing-up; the main oil tank can be almost entirely short-circuited to help in quick warming up of the engine, following a cold start; the pitot head, attached well out on the starboard wing, is electrically heated; and finally, the two emergency venturis for the instruments are placed on the starboard side of the fuselage behind the exhaust outlet.
   In addition to the cockpit heater the pilot’s comfort is further considered. The rudder pedals move horizontally and are adjustable for position; the brake pedals combined with the rudder controls are very light in operation; a telephonic intercommunication system is provided; the seat has a wide range of adjustment for height; and located centrally in front of the control column is a large locker for maps, cards, etc.
   Port and starboard fuel tanks are fitted, each holding 42.6 gallons, of which the port tank has 15.8 gal. held in reserve. The single petrol cock, placed on the port side of the cockpit, has four positions: "off," "right on," "left on," "reserve." A red warning light connected with the fuel pressure system indicates the need to change over tanks, and two fuel gauges on the floor, one each side of the pilot’s seat, have individual illumination, controlled by a switch on the main panel. The endurance at cruising speed (65 per cent, power at rated altitude) is about 3.95 hours. At top speed this is reduced to just over 2 hours.
   Valuable training in the use of a mixture control will form part of the course on Harvards, and an exhaust-gas analyser, a cylinder temperature thermometer and a boost gauge will all have to be used intelligently in conjunction with the mixture, throttle and airscrew controls. Complete blind- and night-flying equipment is fitted.
   A master locking device is interconnected with all flying controls, the position being set to cause the machine to nose over into the ground if the throttle should be inadvertently pushed open when no one is at the controls. A parking brake is also provided.
   In view of the growing complexity of the modern military aircraft the following instructions (as received from America) are not without interest.
   Assuming the fuel and oil tanks to be full and cylinders free of excess oil, the starting operations are: -
   Preliminaries. - (1) Put on parking brakes. (2) Turn on left fuel tank. (2) Carburetter control heat on full cold. (4) Airscrew control coarse. (5) Mixture control full rich. (6) Throttle half-inch open. (7) Fuel hand pumped to 3 lb. pressure [descriptively termed “wobbling-up the gas”]. (8) Four to six strokes of priming pump. (9) Contact. (10) Press rear end of starter pedal to energise starter, (11) Press forward end of starter pedal to engage starter.
   Warming-up. - Minimum oil temperature for take-off, 40 deg. C.; maximum cylinder temperature on the ground 260 deg. C. (1) Adjust throttle to give 500 to 600 r.p.m., holding this until 50 lb. oil pressure is obtained. (2) Airscrew in fine pitch. (3) Throttle to 1,000 r.p.m. (4) Mixture full rich.
   Take-off. - Items to be observed: (1) Fuel on. (2) Controls unlocked. (3) Mixture control rich. (4) Airscrew fine. (5) Flap position (15 deg. for maximum obstacle clearance). (6) Elevator tabs neutral. (7) Carburetter heater cold.
   It is usual to turn on the right-hand tank after about 5 minutes’ flight, possibly to ensure that a brimming tank does not lose fuel due to expansion on reaching high altitudes.
   Landing. - Items to be observed: (1) Mixture control rich. (2) Landing gear down. (3) Flaps down. (4) Airscrew fine. (5) Carburetter heater cold.
   Stopping the Engine. - (Carburetter has an “idle cutoff” (or slow-running cut-out) device when mixture is at full lean). - (1) Set airscrew control at coarse pitch. (2) Idle engine at about 600 r.p.m. (3) Set mixture at full lean (weak). (4) Turn off ignition switch after the engine ceases to fire.
   Figures for the Harvard are: Span, 42ft.; length, 27ft. 6in.; height, 8ft. 9in.; wing area, 255 sq. ft.; wing loading, 20.1 lb./sq. ft.; power loading, 9.68 Ib./b.h.p.; all-up weight, 5,130 lb.; maximum speed, 210 m.p.h. at 2,000ft.; cruising speed, 190 m.p.h. at 11,000ft.; cruising range (consumption. 23 gall./hr. approx.), 750 miles; service ceiling, 23,500ft.; climb to 10,000ft., 11.6 min.