Flight, February 1934

THE LATEST NORTHROPS
The "Victoria" and "Delta" Models

   THESE latest additions to the Northrop range of civil aircraft are similar in general design to the “Alphas" which carry the Los Angeles-New York night mail for Transcontinental & Western Air. The “Alpha" was described in FLIGHT for September 11, 1931. It is claimed by the makers that as the result of improvements in structural and aerodynamic design the new machines have a very much larger pay-load capacity and considerably improved performance for a given horsepower. Engine and airscrew noises are reduced to a minimum through the use of sound deadening insulation throughout the cabin, and vibration is absorbed by insulating the engine on rubber cushioned mountings. The machine can fly for long periods with the pilot's hands and feet off the controls. Full lateral control is maintained beyond the stalling point of the wing even with flaps down. The split trailing edge flaps effect a big reduction in landing speed and length of glide. With flaps in the "down" position the maximum lift of the aerofoil is increased by 35 per cent, and the drag by 300 per cent.
   Except where specifically stated, the following description will apply to both the "Victoria," which is intended for private service, and the "Delta" transport.
   The fuselage is of Northrop all-metal stressed skin monocoque construction with longitudinal stiffeners and oversize reinforcing rings forming a structure well able to withstand abuse on the ground and in the air; 24S.R.T. Alclad is used throughout. Permanent jigged assembly of the fuselage and centre section forms these into a rigid integral unit. The centre section is arranged to carry six fuel tanks of 340 gallons capacity, permitting long range operation without encroaching upon the valuable cargo space in the fuselage.
   An extremely clean cantilever type of landing gear is fitted. It has been proved that fixed undercarriages in which interference has been reduced to an absolute minimum add very little to the drag of the aircraft and avoid the extra weight and complication of retracting gear. The Northrop type gear probably reduces the top speed less than 6 m.p.h. The gear consists of four cantilever oleo pneumatic struts with a streamline fairing enclosing the entire assembly. All parts of the gear, including the fairing, are quickly detachable, making tyre changing and wheel inspection rapid operations. The track is 9 ft. Bendix internal expanding brakes are differentially controlled by rudder pedals and may be set by a parking lever in the cockpit. Floats or skis are easily substituted for the normal land undercarriage. A bulkhead at the junction of the wing and centre section distributes all the landing loads and provides a quick and simple attachment for float struts and bracing wires. For the skis special oleo struts are used, which are attached through rigid struts to the ordinary landing gear fitted in the centre section.
   The wing is of Northrop all-metal stressed-skin multicellular construction. All tension and compression loads are carried on the surface, only the shear loads being carried by internal webs. 24 S.R.T. Alclad is used throughout the wing. The ailerons are of the slotted type and are mounted on ball bearings. Control cables throughout the aircraft pass over ball-bearing pulleys. The empennage, like the wing, employs all-metal stressed-skin multicellular construction. Fin and tail plane are adjustable on the ground and fore and aft trim during flight is accomplished by the use of "Flettners" mounted on the elevators and controlled from the cockpit. The tail wheel is of the full swivelling type, but may be locked in the forward position from the cockpit.
   The cabin of the "Delta" provides accommodation for eight passengers and contains approximately 200 cu. ft. of space. The fully-upholstered seats are 19 in. wide, and individual windows, reading lights, ash-trays and ventilation controls are provided by each seat. A second heating and ventilation system controlled from the cockpit admits either heated air or air at "outside" temperature to the cabin. The door of the cabin is on the port side of the fuselage and an emergency exit is provided on the forward starboard side. A lavatory may be installed if one of the rear seats is omitted. Located aft of the cabin is a baggage compartment of 35 cu, ft. A large door is provided and the compartment is equipped with a dome light.
   Accommodation for six is usually provided in the cabin of the "Victoria." As the machine is intended for the owner-pilot, however, the cabin may be arranged to meet individual requirements, and several alternative arrangements are possible. The seats are usually 19 in. wide and such refinements as individual reading lights, ash-trays, lunch and card trays, ventilation control and assistance cords may be provided. The arrangement of the two forward seats permits the owner of the aircraft to fly the machine himself without separating from his guests. Dual controls are provided and the instrument board is mounted in rubber, which damps vibration at all periods of flight. The cabin is otherwise generally similar to that of the "Delta."
   The usual power plant for the "Victoria" is the Pratt & Whitney "Wasp," S.I.D.I., rated at 525 h.p. at 5,000 ft. This engine uses fuel of 80 octane number and if a lower octane fuel is desired there will be a decrease in performance due to smaller h.p. output. All engine controls, wing, fuel system and instrument leads have quickly-detachable connections, making possible the replacement of the entire power plant within 30 min. The oil tank, which is of 20 gallons capacity, is mounted on the engine-bearing members and forms a unit which is removable with the powerplant assembly. As a fixed-pitch airscrew does not possess satisfactory characteristics for both take off and speed in high-speed aircraft, a variable-pitch airscrew is usually fitted to the latest Northrop models. The "Delta," having a somewhat larger fuselage than the "Victoria" and carrying a larger load, is usually powered with the Wright "Cyclone" S.R.-1820 F-3 engine, of approximately 700 h.p., or the Pratt & Whitney "Hornet" of 660 h.p. may also be fitted.