Flight, May 1935

PAN AMERICAN'S NEW AMPHIBIAN
High Performance and Interesting Construction of Fairchild Monoplane

   SIX Fairchild amphibians of a completely new type are soon to be placed in service by Pan American Airways on its route along the Amazon River from Para to Manaos, and in other sections of its system where the adaptability of the amphibian type is desirable. These machines were designed to meet Pan American's specification for a high-speed amphibian using a 650 h.p. engine, with a capacity of eight passengers, two pilots, and 1,000 lb. of mail and/or express goods, and a cruising range of 750 miles. The cruising speed of the new machines is 158 m.p.h. at 3,000 ft. and the maximum 184 m.p.h.
   The hull is of the semi-monocoque type, embodying five water-tight bulkheads, and a number of frames of flat sheet formed into Z-sections These frames are pierced out near the skin to allow the stringers to pass through between the water-tight bulkheads. Duralumin sheet is used for the side stringers, which are of Z-section, but the bottom stringers of the water planing surfaces are duralumin extrusions. A keel former rather than a heavy keelson is employed, the water loads being carried by the frames and bulkheads into the side skin. The chine spray strips, which are of duralumin extrusions, are actually structural members of the hull.

The Wing

   Riveted to the hull is the centre section of the cantilever wing. It is of two-spar construction, and carries two fuel tanks of 180 gallons total capacity .between the spars. The outboard panels are detachable, and also embody two spars, with thin sheet webs and flanges of duralumin extrusions. The top covering of the wing is in two layers, the inner one with corrugations running parallel to the spars, and the outer one of flat sheet riveted to these corrugations. By utilising the lower flange of the front spar as a rail for the undercarriage retracting trolley, a great deal of weight has been saved. The rear spar of the centre section does not run straight through the hull, but curves above it. Metal covering is used for the leading edge of the wing, but the trailing edge is fabric-covered.
   Metal-framed ailerons are used, statically and mass-balanced by lead weights carried on arms projecting forward from the hinge line and enclosed in the wing at all except large “up" aileron angles. The trailing-edge flaps are attached by slide fittings at their leading edges, and links close to their trailing edges. They are actuated by cables which are wound round a grooved drum in the hull and attached to the flap slide fittings, which move fore and aft on slide tracks upon the rear spar.
   All surfaces of the empennage have duralumin frameworks and fabric covering, with the exception of their nose pieces, which are covered with duralumin sheet beneath the fabric. Both fin and tailplane are braced to the hull by streamlined tie rods, and all control surfaces embody trimming "tabs."
   The undercarriage and tail wheel retract simultaneously, the landing gear structure being so designed that the wheels fold rearwards and upwards, rotating slightly around the axis of the shock absorbers, so that they lie flush with the undersurface of the wing when retracted. A spindle installed within the front spar flange operates a trunnion on the wheel trolley. When turned, this spindle causes the trolley to move inboard or outboard. The tail wheel retracts into a well on the underside of the hull aft of the second "step."
   By means of a parallelogram arrangement of struts the wing floats retract against the underside of the wing. A spindle and trunnion mechanism is used. A recess is provided between the spars, so that the float bracing struts are fully concealed within the wing, and a metal panel, attached to the outer struts, hides the entire float mechanism when the floats are retracted.
   Only one hand crank, one motor and a gear box are used to divert the driving power to the landing gear, flaps or floats, one at a time, when required. An electrical system, with hand cranks for emergency use, is employed.
   Welded chrome molybdenum steel tubing is used for the nacelle structure, which is carried above the wing. It is attached fo the centre section at three points - at the rear spar, and at two points on the front spar. The engine – a Pratt and Whitney "Hornet S4D1," giving 650 h.p. at 2,050 r.p.m. at 3,000 ft. - is supported by means of rubber bushings which allow it to move slightly in the direction of torque, but not in the fore and alt direction. An N.A.C.A. cowling is used. The rear portion of the nacelle can be used for storing baggage or equipment, while its forward portion houses the oil tank, oil cooler, engine controls and accessories.
   The first compartment of the hull, in the extreme bow, is employed for the storage of the anchor and other marine equipment. Aft of this is another compartment utilised for the stowage of baggage, mail and cargo, and accessible from the deck through a hatch. A water-tight door leads to the pilots' cockpit which is immediately behind, and is fitted with dual controls. The engine controls and electrical switches are attached to the roof, and the selecting lever, switch and hand crank for the retracting mechanism gear box are installed between and above the two seats.
   From the pilots' cockpit a water-tight door leads to the central cabin which has four adjustable chairs. A shelf near the cabin ceiling on the port side is used for the storage of lifebelts, and a companion shelf on the opposite side is used for stowing parcels. An emergency exit hatch is provided in the ceiling and leads on to the centre section of the wing. Another water-tight door leads to a second cabin which also has four chairs. Entrance and exit are made through a hatch door to the rear of the second cabin via a folding ladder on the outside of the machine and a fixed stairway within the cabin. The space opposite the stairway can be used for the storage of baggage. To the rear of the cabin is a toilet compartment with wash basin, mirror, etc. Each cabin has four large windows of shatter-proof glass and two electric dome lights. Ventilation and heating is effected by ducts which run alongside the upper part of the cabin walls, and the cabins are sound-proofed in accordance with the latest practice. The leading particulars of the machine are:-
   Dimensions Span, 56 ft.; length, 46 ft.; wing area, 485 sq ft.
   Weights. - Weight empty, 5,500 lb.; gross weight. 9,600 lb.
   Loadings. - Wing loading, 19,78 lb./sq. ft.; power loading, 14.76 lb./h.p.
   Performance. - Maximum speed (sea level), 171) m.p.h.; maximum speed (at 3,000 ft.), 184 m.p.h.; cruising speed (85 per cent, power), 158 m.p.h.; absolute ceiling, 20,000 ft.; stalling speed (without flaps), 68 m.p.h.; stalling speed (with flaps), 58 m.p.h.; range at cruising speed, 750 miles; take-off time (land) 16 sec.; take-off time (water), 36 sec.