Performance Proper performance tests were not done on V.2 before its crash and top speed figures were calculated values, checked by Messerschmitts. The following figures were remembered by Reimar Horten: Dimensions All Up Weight, Including Ammunition and Armor 8,500 kg (18,700 lbs.) All Up Weight, Excluding Ammunition and Armor 7,500 kg Wing Area 52 sq.m (566 sq.ft.) Wing Loading 33 lb./sq.ft. Fuel (I2 Crude Oil) 2,000 kg (4,400 lbs.) Performance at 7,500 kg (16,500 lbs.) Takeoff Run 500 m Takeoff Speed (10° Flap) 150 kph (95 mph) (Note: This corresponds to a CL of 1.30 which is the stated stalling CL of the aircraft.) Top Speed (at Sea Level) 950 kph (590 mph) (CDo estimated to be 0.011) Calculated ceiling was 16 km (52,000’). Engines would not work above 12 km as the burners went out. Rate of Climb at Sea Level 22 m/sec (4,300 ft/min) (Note: This has been checked roughly by observation.) In tests against the Me 262 speeds of 650-700 kph (400-430 mph) were obtained on about 2/3 throttle opening. This appears to be the only flight test figure available. Messerschmitt sent performance calculators to the Horten works to check their estimates. The method suggested by D.V.L. for getting the sweepback correction to compressibility drag was to take an area of 0.3 x the root chord squared at the center section as having no correction applied, and then apply full cosine correction over the outer wing. Sweepback angle was defined as that of the quarter chord locus. Test data was available for CDv. for zero sweepback. The Messerschmitt method was to base sweepback on the max t/c locus and to scale Mach number by the square root cos Ø. Stability and Control The H IX V.1 was flown by Walter Horten, Scheidhauer and Ziller. Scheidhauer did most of the flying (30 hours) at Oranienberg, Horten and Ziller flew for about 10 hours. D.V.L. instrumented the aircraft for drag and directional stability measurements. No drag results were obtained because of trouble with the instrument installation – apparently an incidence measuring pole was fitted which could be lowered in flight and glide path angle was obtained from the difference between attitude and incidence measurements. One day they landed without retracting the pole. Directional oscillation tests were completed successfully and an advance report was issued (10 pages of typescript) by Pinsker and Lugner fo D.V.L. The essence of the results was that the lateral oscillation was of abnormally long period – about 8 sec. At 250 kph and damped out in about 5 cycles. At low speeds the oscillation was of “dutch roll” type but at high speed very little banking occurred. Many fierce arguments took place at D.V.L. on desirable directional stability characteristics , the Hortens naturally joining the “long period” school of thought. They claimed that the long period would enable the pilot to damp out any directional swing with rudder and keep perfectly steady for shooting. It was found that by using both drag rudders simultaneously when aiming, the aircraft could be kept very steady with high damping of any residual oscillation. Lateral control was apparently quite good with very little adverse yaw. Longitudinal control and stability was more like a conventional aircraft than any of the preceding Horten types and there was complete absence of the longitudinal "wiggle" usually produced by flying through gusts. Tuft tests were done to check the stall but the photographs were not good enough for much to be learned. Handling was said to be good at the stall, the aircraft sinking on an even keel. There seems to be some doubt, however, as to whether a full stall had ever taken place since full tests with varying CG and yaw had not been done. Although the stick was pulled hard back, the CG may have been too far forward to give a genuine stall. Directional stability was said by Scheidhauer to be very good, as good as a normal aircraft. He did not discuss this statement in detail as he was obviously very hazy about what he meant by good stability and could give very little precise information about the type and period of the motion compared with normal aircraft. Scheidhauer had flown the Me 163 as a glider and was obviously very impressed with it; he was confident enough to do rolls and loops on his first flight. We asked him how the H IX V.1 compared with the 163; he was reluctant to give an answer and said the two were not comparable because of the difference in size. He finally admitted that he preferred the 163 which was more maneuverable, and a delight to fly (he called it “spielzeug”). The H IX V.2 with jet engines was flown only by Ziller and completed about 2 hours flying before its crash. This occurred after an engine failure – the pilot undershot, tried to stretch the glide and stalled. One wing must have dropped, for the aircraft went in sideways and Ziller was killed. Before the crash a demonstration had been given against an Me 262; Horten said the H IX proved faster and more maneuverable, with a steeper and faster climb. In spite of the crash, Horten thought the single engine performance satisfactory and said the close spacing of the jets made single engined flying relatively simple

johnbr, May 10, 2011
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