This discussion of the Curtiss Robin appeared in "Aviation" magazine on May 21, 1928. Among other details, the article describes Bellanca-like lift struts equipped with airfoils to function as auxiliary lift surfaces. The later Curtiss-Robertson Robin's omitted these large airfoils from their lift struts. The Photographs which included several generic pictures of the Robin, a picture of Lindbergh beside the Robin, and pictures of the wind tunnel model, wing assy and testing of wing ribs were omitted. Note that the gross weight that the appeared on the TC (as described in the second article) is lower than that listed in the first article.
From "AVIATION" magazine, May 21, 1928.
New Commercial Monoplane Powered with an OX-5 has a High Speed of 99.7 M.P.H. and Lands at 40 M.P.H.
By ROBERT R. OSBORN
THE NEW Curtiss "Robin" has made its appearance, quite appropriately, in the springtime, and, like its namesake, promises to become more numerous in the fields as the summer wears on. It was unfortunate that flight tests on the new plane were not completed in time for it to be exhibited at the All-American Aircraft Show at Detroit, as, judging by the interest aroused by the announcement of the new plane and the literature describing it, the exhibit should have been a very popular one.
So far it has been flown extensively by "Casey" jones and Paul Boyd, both of the Curtiss organization, M.M. Merrill, manager of the Curtiss Flying Service, Col. Charles A. Lindbergh, Maj. W. B. Robertson and several of the flying service pilots. The immediate reaction of most of those who have flown it, or have seen it, seems to be to ask Major Robertson, of the Curtiss-Robertson Airplane Manufacturing Co., for the agency in some particular district. Major Robertson says he has enough requests for the agency so far that it seems one could be planced in every county in the United States, but no contracts have been signed, or will be signed, until the construction program is completely organized and the plane actually on a construction basis, so that definite promises of delivery can be made and kept. Everyone is well pleased with the plane, and its performance, appearance and unusual controllability and maneuverability, draw many compliments from all who have flown in it.
The Robin is a high wing monoplane with the airfoil section maintained across the top of the fuselage. The cabin is inset in this wing and as the top of the wing forms the top of the cabin, the depth of the section gives additional head-room. The lift truss is composed of two struts from the bottom of the cabin to a small auxiliary truss under the wing. These two main struts are each enclosed by ribs and a covering which form the same airfoil section as the main wing. These strut wings extend only to the auxiliary truss as they would interfere with the main wing beyond that point. The power plant is the 90 hp. Curtiss OX-5 engine. The Curtiss-Robertson Company is in the fortunate position of ownning 1150 of these engines and a large store of spare parts. The plane has also been analyzed structurally to take the new Curtiss "Challenger" air-cooled engine which develops 180 hp. The Robin seats a pilot and two passengers.
The ailerons are the usual unbalanced type, which have been found to give splendid lateral control. The rudder and stabilizer are not balanced but give full control at the stall with very low stick loads over the flying range. The stabilizer is readily adjusted by a lever at the pilot's left side.
By utilizing the wing lift truss as part of the landing gear truss, a light wide tread landing gear is obtained. By this arrangement the small angles between struts, which are necessary in most landing gear arrangements, and which cause greater structural weight and aerodynamic intereference, are eliminated. The steerable tail skid allows the pilot to handle the plane on the ground as well as any plane equipped with wheel brakes.
The plane was completely designed, and the first three or four are being built by The Curtiss Aeroplane and Motor Co., Inc., at Garden City, Long Island, N.Y. Production on a large scale will be taken to the newly constructed factory of the Curtiss-Robertson Airplane Manufacturing Co., at Anglum, near St.Louis, Mo. This factory, which is now completed, has been built new for the production of this airplane only, and therefore production should be smooth annd the planes turned out in satisfactory quantities.
Models of the airplane were tested in the Curtiss seven foot wind tunnel for aerodynamic qualities. The high performance of the plane is directly traceable to these tests as numerous wing and cabin arranngements were tested and the best one selected. Adequate control in any attitude of the plane was also insured by these tests.
Structural analysis was complete and the structure at every point has an additional margin of safety over the requirements of the Department of Commerce. The long experience of the Curtiss engineers in watching their designs in service conditions enabled them to make additional allowance for parts of the structure which are likely to get hard service, or for materials which tend to deteriorate with age and weathering. All materials are tested by sample, and numerous drop tests were made on the landing gear and tail skid, and complete load tests were made on control surfaces, ribs, beams and numerous fittings. The assurance is rather well estabilished that it is an aerodynamically and structurally safe airplane.
Following is a summary of the performance tests of the Curtiss flight test section. These trials took two weeks to complete and were run in exactly the same manner that a new plane for the Army or Navy is tested. All data is reduced to standard atmosphere.
Gross weight.................................2173 lb. Landing Speed................................40.0 m.p.h. High speed (sea level).......................99.7 m.p.h. 5,000 ft. ................................97.3 m.p.h. 10,000 ft. ...............................91.8 m.p.h. Service ceiling..............................12,750 ft. Absolute ceiling.............................16,650 ft. Take-off time, full load.....................7 to 9 sec. Climb to 5,000 ft. ..........................14.6 min. 10,000 ft. ...............................35.4 min. Service ceiling...........................57.0 min. Climb to 10 min. ............................3,700 ft.With 30 With 50 gal.gasoline gal.gasoline Endurance, full throttle.............3.7 hr. 6.1 hr. Range, full throttle.................370 mi. 608 mi. Endurance at 80% max r.p.m. .........6.2 hr. 10.7 hr. Range at 80% max r.p.m. .............490 mi. 850 mi.
General Characteristics-- Wing Loading..................................8.2 lb./sq.ft. Airfoil section...............................Curtiss-72 Load factor, high incidence 6.5 Dept. of Commerece requirement C.G. in per cent. of mean aerodynamic chord...33.5 Fuel consumption, full throttle...............49.0 lb./hr. Oil consumption, full throttle................3.0 lb./hr. Fuel consumption at 80% max. r.p.m. ..........29.1 lb./hr. Oil consumption at 80% max. r.p.m. ...........2.0 lb./hr. Fuel capacity .......50 U.S.gal. total, 30 gal. normal load Oil capacity .................................4 U.S. gal.
Dimensions-- Length, overall...........................25 ft., 8-1/2 in. Height, overall...........................7 ft., 4 in. Span, overall.............................41 ft., 0 in. Chord.....................................72 in., main wing 15 in., each lift strut Incidence.................................0 deg. Diehedral.................................1-1/2 deg. Sweepback.................................0 deg.
Areas-- Wing, including ailerons..................265 sq.ft. Aileorns, total...........................22 sq.ft. Horizontal tail area, total...............36.3 sq.ft. Vertical tail area, total.................15.2 sq.ft. Elevators, total..........................14.8 sq.ft. Rudder....................................9.8 sq.ft.
Among the unusual structural features of the new plane, and outstanding one is that the wing ribs are made entirely of the new Alclad metal (duralumin with a pure aluminium coating) and are pressed into shape from a single sheet. These ribs weight .40 lb each and take a properlay distributed load along the chord of 535 lb., without yielding. These ribs are placed on spruce spars having the normal type of drag bracing and wooden drag struts. The lift truss is arranged to prevent the warping of the wings from the aileron loads which is the cause of the poor lateral control noticed in many typed of monoplanes.
All of the control surfaces, including the fixed surfaces are made of small steel tubes welded to torque tubes of steel which were throughly tested.
The fuselage is entirely of welded, chrome-molydbenum high tensile steel, the Warren truss arrangement being used, eliminnating the use of brace wires.
The ribs for the airfoil section on the lift struts are made in the same way as are the main wing ribs, pressed from a sing sheet of Alclad.
Seats for the passengers are side-by-side and can be adjusted in a fore-and-aft direction readily. This allows a staggered seating arrangement, giving additional shoulder clearance and comfort. For instructing students a dual control can be fitted in the center, not part of the standard eequipment, and when that is used the two seats are lined up and the man at the aft control sits in the center of the fuselage.
A 25 gal. welded aluminum gas tank is set in each wing root and the engine may be fed by gravity from either tank.
The pilot has the usual stick and pedal control, and has a quick acting stabilizer adjustment at his left side. On the instrument board are mounted a tachometer, thermometer, oil gauge, altimeter and air speed indicator.
The interior is completly upholstered and pleasingly finished.
The wind tunnel tests on the Robin show ample control in all attitudes of the plane, and a natural stability which was completly checked by the full flight reports. The large diehedral of the lift strut wings and the small diehedral of the main wings added considerably to the natural pendulum stability of a high wing monoplane.
In spite of the fact that the cabin section of the fuselage is made square in section, both for the comfort and the visibility of the fliers, and for simplicity of construction, the plane showed the very surprising maximum lift drag ratio of ten.
According to Major Robertson the price of the plane will be about $4,000 complete. This will be for a plane ready to fly and complete in all details. Provision has been made in the structure for "extras" that the prospective owner might wish, such as dual control, wheel brakes, lights or additional instruments.
The Robin promised to be a very welcome and popular airplane for both the private owner and the commercial operator.
From "AVIATION", June 11, 1928.
WORD WAS recently received from the Aeronautics Branch, Department of Commerce, that the Curtiss Robin has been granted its airworthiness approved type certificate. The plane has been approved to carry a weight of 727 lb and as it weights 1,490 lb. empty, the gross weight is 2217 lb. The Robin, which was described in detail in the May 21 issue of AVIATION, is a closed cabin monoplane powered with a Curtiss OX-5 engine. The design was engineered by the Curtiss Aeroplane & Motor Co., Garden City, L.I.,N.Y., and is being put into production by the Curtiss Robertson Aircraft Mfg. Co. of Anglum, St. Louis County, Mo.