Flight, January 1929
THE THADEN T-2
An American All-Metal Commercial Monoplane
ONE of several interesting new machines exhibited at the recent Los Angeles Aeronautical Exposition was the Thaden type T-2 all-metal monoplane constructed by the Thaden Metal
Aircraft Co., of San Francisco. The Thaden T-2 - which is the second type of machine produced by the company, the "Argonaut" T-1 being their first and larger model - is a three-four passenger full cantilever wing cabin monoplane powered with a "Comet" seven-cylinder air-cooled radial engine developing 150 h.p. at 1,800 r.p.m. Although similar in design to the "Argonaut," it differs mainly in having the full cantilever wing fitted with "flaps" on the trailing edge, which make it possible to vary the camber of the wing.
Duralumin is used almost entirely in its construction, and the fuselage is of the monocoque type. Multi-spar wing construction is employed in the plane producing an unusually rugged unit. The structure consists of five spars of the plate girder type, with corrugated duralumin sheathing which provides drag bracing for the wing. To speed up production on these units the company has developed several jigs of unusual design, including a large one for wing assembly.
Static tests on the completed wings have given proof of the sturdiness of this type of construction, and in one instance a load of 19,000 lb. was applied without any indication of failure, deformation of members or loosening of rivets. This load produced an extreme deflection of only 7 ins. at the wing tips.
With the exception of the leading edge of the wing, the window casings and a few tubular members, all parts of the 'plane's structure are of corrugated duralumin. A special die has been developed by the manufacturer to fair the corrugations into plane surfaces, producing an exceptionally smooth modulation and avoiding minor air turbulences set up by other types of transition plates. Duralumin plate fittings attached to the wing spars and to internal stiffening members of the fuselage are coupled by twelve 1/2-in. nickel steel bolts, producing an effective method of wing attachment.
The fuselage construction, which was first introduced in the "Argonaut," is as follows :- The engine mounting is of welded steel tubing, and is the only portion of the plane conforming to conventional practice. Shaped duralumin members extend from the rear of the engine mounting past all openings in the monocoque structure to the after end of the cabin. Abaft that point, the internal bracing is entirely transverse, provided by duralumin tube bulkheads riveted to the skin. These are placed closer together toward the tail to strengthen the shell against landing shocks transmitted through the tail skid. Bulkheads are also provided at the front and rear of the cabin, the forward one being cut out to allow easy access to the pilot's seat.
This type of fuselage has proved to be very rigid both in flight and in landing, and in one test a 1-ton weight was placed on the tail without the slightest deformation. The fuselage has a true airfoil section which is said to contribute to the lift.
The Thaden T-2 is, we believe, the first American machine to utilise wing flaps to produce variable camber. These flaps are of triangular section, duralumin sheathed, and occupy all of the trailing edge except the portion where the ailerons are attached. They are actuated by a wheel and worm gear built into the lower portion of the wing structure just above and to the right of the pilot's seat. In extreme upper position they conform with the normal curve of the wing and permit of maximum speed. Downward deflection results in increased lift and any intermediate position can be held firmly because of the worm gear arrangement. The flaps represent approximately 9 per cent, of the total lifting surface and decrease the landing speed by approximately 9 m.p.h.
Ailerons and other control surfaces are similar in construction to the flaps and are actuated by horns and steel cables operating over micarta sheaves. The rudder is 10 per cent, balanced, the stabiliser is adjustable in flight and the fin is adjustable on the ground. All control surfaces have been tested to 25 per cent, overload.
Ample height and full leg-room are afforded in the comfortable cabin which is furnished in automobile fashion, the pilot's section being lined with terne plate and the passenger compartment upholstered in mohair. Both are well insulated and the interior colour is steel gray throughout.
The length of the cabin, including pilot's compartment, is 8 ft., the width 3 ft. 4 ins., and the height 4 ft. Large, easily opened, plate-glass windows are provided on each side of the cabin. The forward end is almost entirely of glass, affording unusual visibility ahead, to the sides and below to a point inside and considerably to the rear of the wheels. A sliding glass panel over the pilot's seat provides visibility above and, while designed for an emergency exit, it is so conveniently located that it will probably be used by the pilot in preference to entering and leaving the plane through the cabin. The mounting on which this panel moves is such that the natural pressure of the air stream tends to hold the glass in place rather than to raise it.
A wide and comfortable lounge seat extending the full width of the cabin and accommodating two persons is placed at the rear. In the forward part a bucket seat is provided for the pilot at one side and at the other side a folding seat is placed, and may be used when it is desired to carry an extra passenger or a relief pilot. A large luggage compartment is built into the fuselage structure behind the cabin.
Conventional stick and rudder pedals are employed in the control system, and in production planes a second socket and an additional set of pedals will be provided for instructional and other purposes. There is, however, only one control for the wing flaps.
The usual fireproof bulkhead is inserted between the cabin and engine compartments and the engine mounting is so designed as to afford easy access to the rear of the power plant when it is necessary to adjust or repair carburettor, magneto or starter. The exhaust ring is sunk into the cowling to reduce parasitic resistance, but an air channel is provided around it to prevent overheating. Fuel supply of 40 gallons is carried in the two wing tanks over the fuselage and accessible through cover plates. An emergency tank of 10 gallons capacity feeds directly to the carburettor eliminating the necessity of a forced landing if the fuel supply from the main tanks is stopped.
The landing gear is of the split-axle type, built up of heat-treated chrome molybdenum steel tubing with Gruss shock absorbers inserted in the compression members. Bendix wheels and brake units are used and the brake control is so adjusted that either or both brakes may be applied at will. A leaf steel spring is used to absorb tail skid landing shock. The landing gear, tail skid, door handles and control horns are the only members protruding beyond the outline of the 'plane, all other units being streamlined into the structure.
The specifications furnished by the manufacturer are as follow :-
Span 39 ft.
Length o.a. 25 ft.
Height 7 ft. 9 in.
Chord (maximum) 8 ft.
Wing area (including flaps and ailerons) 226 sq. ft.
Flap area 21 1/2 sq. ft.
Aileron area 19 sq. ft.
Elevator and stabiliser area 30 1/2 sq. ft.
Rudder and fin area 11 1/4 sq. ft.
Power plant 150 h.p. "Comet.”
Fuel capacity 50 galls.
Oil capacity 6 galls.
Speed, maximum 121 m.p.h.
Cruising 90 m.p.h.
Landing, flaps up 55 m.p.h.
Landing, flaps down 46 m.p.h.
Rate of climb, sea level 800 ft. per min.
Service ceiling 16,000 ft.