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Aviation History
1925
1925 - 0040.PDF
JANUARY 2?, 1925 can only be described as exceptionally good, the more so asthe two seats are arranged side by side in order to make the machine more " sociable " for touring and especiallysuitable for school work. As already mentioned, in designing the " Dongo," Hen-Rotter desired to afford the occupants a good view, and at the same time he wanted to keep the machine as efficient aspossible so as to get a good performance with small power output. By choosing a very narrow chord and heavily stag-gering the planes, he was able to avoid any cut-out in the trailing edge of the top plane, a feature of most " orthodox "biplanes and one which in the opinion of the designer of the " Dongo " is detrimental to efficiency. The pronouncedstagger (very nearly equal to the chord) has further been employed to give longitudinal stability by setting the topplane at a positive angle of incidence of 2 degrees and the bottom plane at 0 degree incidence. It is claimed that by thisarrangement sudden stalling is avoided. The safety of the occupants is thought to be assured by thestrong steel-tube cabane upon which the top centre-section is mounted. Should the machine turn over on the ground,it is thought that this cabane would stand up to any reason- able shock. Incidentally, it might be mentioned that thecabane is provided with means of altering both the angle of incidence and the stagger. The single inter-plane struts are of " K," or rather of " X 'formation, the main strut running from bottom front to top rear spar, and the diagonal members of the built-up strutrunning to rear and front spars respectively. The lift bracing is in the form of a single steel tube on each side, working bothin tension and in compression, twisting stresses being taken by the inter-plane struts. Ailerons are provided on thebottom plane only, and are stated to have proved to give ample controllability. The fuselage is of the fiat-sided type, with rounded topand bottom fairings, and as already mentioned, the occupants sit side by side, so that the fuselage is necessarily somewhatwide (3 ft. 11 in.). Dual controls are provided, the set on one side being readily removable. An engine of 60 h.p. hadbeen contemplated, but as one was not available when the machine was finished a larger engine of the rotary type wasinstalled and was throttled down from 1,250 r.p.m. to 1,050 r.p.m., in order to represent the engine for which the machinewas designed. At the reduced revolutions, this engine and airscrew combination was estimated to give exactly the equi-valent of the -60 h.p. engine, although the extra weight naturally affected the performance somewhat adversely. The rotary engine is mounted on an all-steel structure inthe nose of the machine, and the engine housing is separated from the cockpit by two fireproof bulkheads. The carburettor,oil pump, etc., are placed in the space between these two bulk- heads, and as the air intakes are taken outside the cowling,while the space between bulkheads is well ventilated, there should be very small risk of fire. The petrol tank is placed ia the deck fairing, aft of the rear fireproof bulkhead and abovethe cockpit. It gives a sufficient head of petrol to enable direct gravity feed to be employed.The undercarriage is of fairly normal type, but the wheels are placed rather farther forward than normal in order toreduce the risk of nosing over. In spite of this fact, the tail is stated to come up quickly on opening out the engine,owing probably to the effective tail of high aspect ratio. The forward wheel position might be expected to give the machinea tendency to pitch and bounce somewhat, but we understand that no trouble of this sort has been experienced. 14- 13 12 II iO 9 8 1 Ca 1 i1 r I 1 I J 6I ( t t f-J , _ o -4 -5- -7- > '1 7~ /,r 0° 64 42s .8% A / [*525 b" 1 * 2 4 -6 -8 10 1-2 I A. 1-6 16 20 Cw VECTOR DIAGRAM OF THE FEIRO "DONGO " :The maximum L/D ratio occurs at an angle of — J degree and has a value of nearly 16. The main dimensions of the Feiro " Dongo " are : Length o.a., 6-2 m. (20 ft. 4 in.) ; span, upper plane, 11-5 m. (37 ft. 9 in.) ; span lower plane, 10-5 m. (34 ft. 5£ in.) ; total wing area, 15 sq. m. (161$ sq. ft.). Weight, empty, 450 kgs. (990 lbs.) ; useful load, 240 kgs. (528 lbs.) ; total" loaded weight, 690 kgs. (1,518 lbs.). Weight per sq. ft., 9-4 lbs. ; weight per h.p. (on 60 b.h.p.), 25-3 lbs. On a test flight, with this loading the " Dongo " got " unstuck " at a speed of 75 km./h. (46-8 m.p.h.) and reached an altitude of 1,000 m. (3,280 ft.) in 5 minutes 40 seconds. The top speed is 165 km./h. (103 m.p.b,) SPAN-TOP- ...37-8%.SPAN - BOTTOM- 34- 5V LENGTH 20'--4." WING AREA . !6I-4-5QFT o i a 3AS67e9u rterr FEIRO "DONGO" SCHOOL MACHINE ROTARY ENGINE A HUNGARIAN SCHOOL MACHINE : General arrangement drawings, to scale, of the Feiro "Dongo." - : . ,..40 . . . . . ... , .. , ..-••
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