FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1933
1933 - 0959.PDF
FLIGHT, NOVEMBER 9, 1933 Direction of Rotation. (b) T. ^^^dri _ Jr^Ki^i. V i /S> V'^ A Arrows*—-eindicate direction of flight. Diagram showing various wing forces acting under different conditions of flight. These are (a) horizontal flight ; (b) upward inclined flight ; (c) downward inclined flight ; (d) vertical ascent ; (e) vertical descent without 0 motor power. by the relative direction of flight to the horizon, the figures represent the condition of:—(a) Horizontal flight; ib) upward inclined flight; (c) downward inclined flight; [d) vertical ascent; (e) vertical descent without motor power, with the wings auto-rotating and continuing to produce sufficient lift forces. Dimensions and weights and tank capacities of the machine referred to above are as follows :— Dimensions—Length, 28 ft. ; height, 14 ft. ; span, 33 ft. Motor— 1 motor of 240 h.p. Tank capacity—Fuel, 80 gals. ; oil, 7 gals. Weights— Weight empty (structure weight, instruments, equipment for 3 persons) . . . . . . 1,500 lb. Useful load (fuel and oil, 3 persons) . . . . 600 ,, All-up weight (for vertical ascent). . . . .. 2,100 lb. If a little of the vertical ascent and of the hovering characteristic is sacrificed, the dead weight and disposable load may be increased as follows: — Minimum speed relative to air. Zero 13 m.p.h. = 19 ft. per sec. All-up weight. Useful load. 2,100 1b. 2,640 ,, 600 lb. 1,140 ,, Flying performance with 2,100 lb. All-up weight Horizontal speed at sea level : Full throttle 124 m.p.h. Engines throttled 25 per cent. . . 106 Minimum speed at sea level .. .. 0 Backward speed at sea level . . . . 19 Ceiling 14,800 ft. Ceiling when hovering without forward movement : with a wind of magnitude 2 (German scale), i.e., 19 ft. per sec 7,250 ., With no wind 1,640 ., With an all-up weight of 2,640 lb Horizontal speed Ceiling 118 m.p.h. 8,850 ft. Range figures : Weight empty Disposable load : Pilot Passenger Passenger Fuel and oil . . . . 1,500 176 165 '.'. 259 1,500 176 — 424 1,500 176 165 165 634 176 944 All-up weight Average cruising speed Range 2,100 2,100 115 115 254 425 2,640 2,640 ,, 112 112 m.p.h 650 965 miles The performance figures based on careful calculations are as above. The ceiling, when hovering so that the aircraft is stationary in relation to the ground, is considerably in creased if a wind is blowing. The maximum ceiling of the hovering machine in a wind of 19 ft. per second is some 7,500 ft. higher than the ceiling obtained when hovering in still air. These figures have been confirmed by the re volving wing reports from America, referred to earlier in this article, which state that hovering requires 60 per cent, more power than forward flight at 45 m.p.h., and when it was also found that the rate of climb vertically was increased from 700 ft. per minute when climbing vertically to 1,500 ft. per minute up an inclined path. Referring to the power requirements of revolving wings and assuming a certain all-up weight of the aircraft, the velocity of the downward accelerated airstream increases with the reduction of the size of the rotor and the space traversed by revolving wings, this increase resulting in a corresponding increase of the engine power required to hover and to fly forward. The earlier types of airwheels and revolving wings were either of impracticable pro portions or lacked certain structural and functional elements indispensable to proper working except with impossibly small power loading. The Rohrbach machine can, however, be confidently expected to achieve the following power loadings: — With ability to hover up to 11 lb. per h.p. With minimum air speed of 17 m.p.h., 17.6 lb. per h.p. With minimum air speed of 34 m.p.h., 24 lb. per h.p. Control System Lateral control is effected in the usual manner by lateral displacements of the control-stick, which, by means of a differential device of the wing oscillation control, product- different lift forces on the two wing sets. The directional control is operated through foot-levers or pedals, as usual. The controlling effect is obtained by- means of a differential device of the wing oscillation control, so that different propelling forces are produced on the two wing sets. It may be that a rudder connected to the same foot-levers allows a finer regulation of the directional control at high speeds. Practical trials will show whether such a special rudder is desirable or not. The flying attitude and the translational speed are con trolled (with a corresponding adjustment of the engine controls) by means of the wing oscillation control, through a displacement of the control-stick in a fore and aft direc tion, in the sense of the desired movement of the aircraft. It is impossible to " stall " the revolving wing aircraft. Calculations prove that at all flight speeds, including zero speed, the Rohrbach machine would have strong positive stability in pitch and in roll. In yaw there would be, if not a slight positive stability, at least a neutral condition. Efficiency An advantage of the revolving wing machine is that a mechanical transmission carries the engine power direct to the wings, avoiding the considerable aerodynamic losses of the usual airscrew. Even with an airscrew working under optimum conditions the gearing would show 10 per cent. to 15 per cent, better efficiency, a virtual gift of 50 h.p. to 75 h.p. in the case of a 500-h.p. machine. On the other hand, the aerodynamic drag of the shaft and of the plurality of spokes and struts necessarily produces a certain parasite drag and loss of power. Tests and calculations have shown, however, that this loss is comparatively small. A further important aspect of the matter is that the speed of the down.vash is low and that the actual aerodynamic angles of attack of the wings are always relatively small and close to the angles giving the greatest L/D values for the aerofoil. Consequently an overall efficiency or lift/drag ratio of 1:8 or 1:9 can be confidently expected in this type of aircraft. 1123 D 2
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
