Exo Cruiser: Horten H IX (or Ho 229 or Gotha Go 229) Construction Details and Story

The Horten Ho 229 V.3 is Currently been Restored and Preserved

Horten Ho 229 (IX) V.3, June 2011

"Early in June 2011, staff of the Paul E. Garber Preservation, Restoration and Storage Facility slowly and carefully moved the center section of the Horten H IX V.3 all-wing jet fighter from storage into the restoration and preservation shop." /4/

General

"The H IX was a single seat fighter bomber of 16 m span with twin jet engines, being a further development of the H V and H VII designs. The following figure is a general arrangement drawing made from a wooden model found at Gottingen 1945 (Gotha, Friedrichroda), where the first two of the type were built." /6/

General arrangement drawing made from a wooden model found at Gottingen

"Four (actually 6) aircraft of the H IX type were started, designated V.1 to V.4 (V.6). V.1 was the prototype, designed as a single seater with twin B.M.W. 003 jets, which were not ready when the airframe was finished. It was accordingly completed as a glider (not reproducible) and extensively test flown." /6/

("V" - German word "Versuch" literally test or experiment)

V-1 was completed as a glider (no turbines)

"D.V.L. (Deutsche Versuchsanstalt für Luftfahrt) instrumented it for special directional damping tests to determine its suitability as a gun platform."

V.2 (later crashed)

"V.2 was completed (also at Gottingen) with two Jumo 004 units and did 2-hours flying before crashing during a single engine landing. The pilot (Ziller) apparently landed short after misjudging his approach. (Ziller was killed)"

V.3 was never flown (photo by Allied troops that captured the factory at Friedrichroda)

"V.3 was being built by Gotha at Friedrichsrodal as a prototype of the series production version (and later shipped to USA)."

V.4 (The V4 had received the engines and the works had begun to create the wood structure.)

"V.4 (V5 and V.6) did not get beyond the project stage. V.4 was to be a two-seater night fighter with an extended nose to house the extra man." /6/

V.5 (An American soldier standing by the side of the V5 prototype)

"In shape, the H IX was a pure wing with increased chord at the center to give sufficient thickness to house the pilot and the jet units, which were placed close together on either side." /6/

Gothaer Waggonfabrik

"Gothaer Waggonfabrik (Gotha, GWF) was a German manufacturer of rolling stock established in the late nineteenth century at Gotha. During the two world wars, the company expanded into aircraft building." /9/

Gotha logo

"February 24th and July 20th, 1944 the factory was 80% destrayed in air-raids. Nevertheless the production of Horten prototypes moved to Gotha, Friedrichroda in 1945. After the war 1949 the company was state owned using the name VEB Waggonbau Gotha." /10, 11, 12/

The Gothaer Waggonfabrik, AG, Gotha, Germany was bombed February 24th and July 20th, 1944. /11/

Northrop-built reproduction /1/

Video about Northrop's Ho 229 reproduction techniques

"After the war, Reimar Horten said he mixed charcoal dust in with the wood glue to absorb electromagnetic waves (radar), which he believed could shield the aircraft from detection by British early warning ground-based radar known as Chain Home. A jet-powered flying wing design such as the Horten Ho 229 will have a smaller radar cross-section than conventional contemporary twin-engine aircraft. This is because, with wings blended into the fuselage, there would be no large propeller disks or vertical and horizontal tail surfaces to provide a typical identifiable radar signature." /1/

Reimar und Walter Horten

"Reimar, Walter and Wolfram Horten were three brothers who were born and raised in the Germany of the early 20th century. Wolfram was killed (shot down) early in the World War II (20. May 1940) over Dünkirchen in a Heinkel He 111." /2/

The National Air and Space Museum (NASM) of the Smithsonian Institution holds the largest collection of historic aircraft and spacecraft in the world

"Engineers of the Northrop-Grumman Corporation had long been interested in the Ho 229, and several of them visited the Smithsonian Museum's facility in Silver Hill, Maryland in the early 1980s to study the V3 airframe. A team of engineers from Northrop-Grumman ran electromagnetic tests on the V3's multilayer wooden center-section nose cones. The cones are three quarters of an inch (19 mm) thick and made up of thin sheets of veneer. The team concluded that there was indeed some form of conducting element in the glue, as the radar signal slowed down considerably as it passed through the cone." /1/

"In early 2008, Northrop-Grumman paired up television documentary producer Michael Jorgensen, and the National Geographic Channel to produce a documentary to determine whether the Ho 229 was, in fact, the world's first true "stealth" fighter-bomber. Northrop-Grumman built a full-size reproduction of the V3, incorporating a replica glue mixture (see below for details) in the nose section. After an expenditure of about US$ 250,000 and 2,500 man-hours, Northrop's Ho 229 reproduction was tested at the company's classified radar cross-section (RCS) test range at Tejon, California, where it was placed on a 15-meter (50 ft) articulating pole and exposed to electromagnetic energy sources from various angles, using the same three frequencies in the 20–50 MHz range used by the Chain Home in the mid-1940s." /1/

Tejon Ranch RCS Facility

"The Northrop facility goes by the name of Tejon Ranch (pronounced tay-on) or Tejon Ranch RCS Facility, and is sometimes referred to as the "Tehachapi Ranch." It is located in the foothills of the Tehachapi mountains, at the mouth of Little Oak Canyon, about 25 miles northwest of Lancaster, California, and 18 miles due west of the town of Rosamond. It is not under restricted airspace. Although publicly said to be a cattle ranch, no livestock are visible anywhere on the property. The long, wide surfaces said to be visible in aerial photos are not runways, though there are said to be white-painted diamond-shaped features on these surfaces. A white pylon is visible in the center of one diamond shape, and a pylon "rack" and antenna array are located near the main buildings." /5/

Wings of V.3

"RCS testing showed that a hypothetical Ho 229 approaching the English coast from France flying at 885 km/h (550 mph) at 15–30 metres (50–100 ft) above the water would have been visible at a distance of 80% that of a Bf 109. This implies an RCS of only 40% that of a Bf 109, from the front at the Chain Home frequencies. The most visible parts of the aircraft were the jet inlets and the cockpit, but caused no return through smaller dimensions than the CH wavelength. However, the speed of the aircraft, combined with the 20% advantage created by its stealth characteristics, would have made it a serious threat, able to begin an attack before defenses could be brought into play and continuing at a speed too fast for conventional fighter aircraft to nullify." /1/

The Horten Ho 229 replica in the San Diego Air and Space Museum

"With testing complete, the reproduction was donated by Northrop-Grumman to the San Diego Air and Space Museum. The television documentary, Hitler's Stealth Fighter (2009), produced by Myth Merchant Films featured the Northrop-Grumman full-scale Ho 229 model as well as CGI reconstructions depicting a fictional wartime scenario where Ho 229s were operational in both offensive and defensive roles." /1/

The Ho IX Twin Jet /3/

Hermann Göring was a veteran of World War I and an ace fighter pilot

"In a speech before representatives of the aircraft industry, Reichsmarshall Goering had announced that no new contracts would be given, unless the proposed aircraft could carry 1000 kg bombs, fly 1000 km /h, and have a penetration depth of 1000 km; penetration depth being defined as the total range."

MK-101 30mm aircraft cannon

"The Fighter Division requested that the aircraft also be fitted with 30 mm machine guns, something that would lessen the machine's efficiency as a bomber."

"We (Horten brothers) started drawing and calculating without a contract. Our plan was to build two full size prototypes. The initial penetration depth would only be 800 km, since the fuel proof glue necessary for the full wet wing, was not yet available. On the other hand, the smaller fuel load allowed a doubling of the bomb load, so we went ahead and submitted our proposal."

Horten H IX (Ho 229 or Gotha Go 229) V.3 cutaway

"A contract was awarded with the demand that the first flight be made in six months! Since the jet engine was not yet ready, the first machine would be a glider. The previously deactivated Air Force Command IX was reactivated, and ordered to proceed with the project. Fortunately, the preliminary work that we did without a contract, put us sufficiently ahead, so the six month deadline locked feasible."

"There were several reasons for choosing wood as the building material. Duraluminum required more energy to produce; over 3000 KWH, versus less than 3 KWH for wood per ton. The required labor for aluminum production was also much higher; 5000 hr/ton against 200 hr/ton for wood. In addition, aural was difficult to find, and skilled sheet metal workers in short supply. Unskilled workers could easier be trained to work with wood."

A triangular piece of spruce, sandwiched between two plywood sheets

"Typically, a nose rib was built from a triangular piece of spruce, sandwiched between two plywood sheets, all scrap wood. Production time: 10 minutes. After the glue dried, the rib was simply roused out along a master template in less that 5 minutes. The rest of the wing was built in a similar crude fashion, to pave the way for mass production by unskilled workers."

Wings

"The main box spar contained all cables and control rods, to free the remaining space in the wing for fuel. That, we planned to pump right into the wing itself, without tanks or bladders. To do this, we needed the fuel-proof glue, that could be used to coat the inside surfaces as well. The glue allowed additional gluing to dissolve and adhere to already coated surfaces, which greatly simplified construction."

Charcoal

"The skin was very thick: 17 mm, all plywood; three times the necessary strength. On the production aircraft, this would be replaced by two 1.5 mm plywood sheets, with a 12 mm layer of sawdust, charcoal and glue mix, sandwiched in between."

17 mm sandwich with 12 mm layer of radar absorbing material inside

"The charcoal in this much lighter skin would diffuse radar beams, and make the aircraft "invisible" on radar."

Sawdust

"Finally, should a 20 mm shell explode inside the wing, a relatively harmless hole would result, whereas a metal wing would balloon out and lose its lift."

"The H IX wing was designed with 3 geometric and 1.5 aerodynamic twist, to give it the desired bell shaped lift distribution with all controls neutral."

Different aileron (elevon) types

"The Frise-nose on the elevons had proven to be unsatisfactory, so we decided to use blunt nose elevons instead. The sharply enlarged wing root chord served mainly to eliminate the middle-effect. The maximum thickness line (T-4 line) therefore made a sharp bend in the middle, which resulted in the characteristic pointed tail. As this would affect stability, a test aircraft with large aspect ratio, that had the control surface far outside the test area, was needed. The H Vl would serve this purpose, while other preliminary tests were made with a H II and a H III."

Heinkel He 45

"The H IX V-1 took off right on schedule on March 1, 1944 in Gottingen. The small He 45 towplane barely got off the ground, so test pilot Scheidhauer released, and landed straight ahead, after only a short hop. Five days later, he was off again on a snow covered runway behind an infinitely more powerful He 111. He released at 12000 feet, made an uneventful glide back to the airport, then faced problems during landing when the drag chute did not function. As the end of the runway approached, he retracted the nose wheel, and skidded to a stop with only minor damage."

Heinkel He 111

"The second aircraft, scheduled to fly three months later, was awaiting its engines, promised in March. Several weeks passed, and then... Disaster!"

The engine diameter was 20 cm too large

"The engines arrived with an accessory section added to the case, making the cross section oval, and the diameter 20 cm greater! No one had bothered to inform us! Now, just six weeks before the first flight, we were faced with the problem of fitting an 80 cm engine into an aircraft with a 60 cm hole in the spar! It meant that the wing would have to be made thicker." (Junkers Jumo 004 had larger diameter than the BMW 003 turbine)

"To maintain the aerodynamic qualities of our design, we would have to increase the span from 16 to 21.3 meters, and the wing area from 42 m2 to 75 m2. Such an aircraft would never reach the targeted performance, even with higher engine thrust. We choose instead to do the best we could with patchwork modifications. The wings remained the same. Another root rib was added 40 cm outside the original, making the center section 0.8 m wider. The new airfoil was 13% thicker than before, and the bend in the T-4 line became much larger. The thicker center section lowered the critical Mach number to 0.75, or a maximum speed of 920 km/h."

Heinkel He 177 "Greif"

"The ratio of movement between the control column and the elevons could be reduced to by the pilot for high speed flight. A small high speed drag rudder was supplemented by a larger one that deployed after the smaller was fully extended. Many parts were scrounged from other aircraft left at the test facility in Gottingen. The nose wheel, for instance, came from the tail wheel of a He 177 heavy bomber. We were even able to use the strut and retract cylinder!"

"The men of Air Force Command IX did their utmost to complete the aircraft before the end of 1944, sometimes working more than 90 hours per week."

Lt. Erwin Ziller

"I remember that Lt. Erwin Ziller made the first flight about December 18th, 1944, but his log book indicates that the first flight occurred on February 2nd., 1945. I am quite sure the first flight of the H IX was also his first in a jet. Our leaders had little concern for such risks."

"Satisfied with the initial flight, the Air ministry ordered 40 aircraft to be built by the Goetha Waggonfabrik under the designation 8 -229."

Ziller in V.2

"It appears that the H IX V-2 had flown three or four times before tragedy struck on February 18th. The many versions of the story have a few things in common. The weather was overcast, the ground soft and muddy. The visibility marginal for a test flight, as Lt. Ziller took off, retracted the gear and disappeared. We received a report that one engine had failed, and that the H IX was returning to Oranienburg. Due to the low ceiling, a shallow approach to the airport was initiated. Since the hydraulic pump was on the dead engine, gear and flaps were extended by the emergency compressed air system. Once down, they could no. be retracted. To maintain his glide slope, Lt. Ziller added power. to overcome the extra drag, and found to his horror that he could" no longer maintain directional control; the fully developed drag rudder unable to overcome the asymmetrical thrust. Rather than lose control, he retarded the throttle to land short of the runway. The aircraft touched down in a field, slid into an embankment and flipped over, crushing its pilot."

The cockpit did not offer any protection for the pilot if it flipped over

"The Third US Army Corps reached the Goetha plant on April 14th 1945. Here they found the H IX V.3 intact and nearly completed, and also the V.4, V.5 and V.6 in various stages of completion."

Possible later picture of the V.1

"The Ninth US Armored Division found the H IX V.1 in good condition near Leipzig. Its fate is unknown."

V.3, 1945

"The H IX V.3 was later 1945 shipped to USA, and is now in the Smithsonian collection, awaiting restoration." /3/

V.3, 2011

"Early in June 2011 the center section was slowly and carefully moved from storage into the restoration and preservation shop." /4/

Aerodynamic Design

"The H IX started as a private venture and the Hortens were very anxious to avoid failure so they avoided aerodynamic experiments wherever possible. A lower sweepback was used than on the H V and H VII and laminar flow wing sections were avoided as a potential source of trouble. Wing section at the junction with the center sections was 14% thick with maximum thickness at 30% and 1.8% zero Cmo camber line (Cmo, pitching moment coefficient). At the centerline thickness was increased locally to 16% to house the crew. The tip section was symmetrical and 8% thick. Horten also believed that since the compressibility cosine correction to drag was based on the sweepback of the maximum thickness line, the ordinary section would show little disadvantage." /6/

Large front landing gear carried 40% of the load, it retracted behind the pilot

"Wing twist was fixed by consideration of the critical Mach number of the underside of the tip section at top speed. This gave a maximum washout of 1.8°. Having fixed this, the CG was located to give trim at CL = 0.3 with elevons neutral. In deciding twist for high speed aircraft, CD values were considered in relation to local CL at operational top speed and altitude (10 km in the case of the H IX). Twist was arranged to give minimum overall drag consistent with trim requirements. The wing planform was designed to give a stall commencing at 0.3 to 0.4 of the semi-span." /6/

The center section (fuselage) was made of welded steel tube frame covered with plywood

Structure

"Wing structure comprised a main spar and one auxiliary spar of wooden construction with ply covering."

V.3 wing

"The center section ("fuselage") was built up from welded steel tube."

The welded steel tube center section of V.3

"Wing tips were all metal. The undercarriage was completely retractable and of tricycle type the front wheel folding backwards and the main wheels inwards."

V.2 landing gears

"The nose wheel was castering and centered with a roller cam. When resting on the ground, wing incidence was 7° and the nose wheel took about 40% of the total weight." /6/

Engine Installation

"The jet engines (BMW 003 or Junkers Jumo 004) were installed at -2° to the root chord and exhausted on the upper surface of the wing at 70% back from the nose."

"To protect the wings the surface was covered with metal plates aft of the jet pipe and cold air bled from the lower surface of the wing by a forward facing duct and introduced between the jet and the wing surface. The installation angle was such that in high speed flight the jest were parallel to the direction of flight." /6/

BMW 003 jet engine

"Specifications (BMW 003A-1)

Type: Non-afterburning turbojet

Length: 3,530 mm (139 in)

Diameter: 690 mm (27 in)

Dry weight: 562 kg (1,240 lb)

Compressor: 7-stage axial compressor

Combustors: Annular

Turbine: Single-stage

Fuel type: 87 Octane petrol

Maximum thrust: 800 kgf (7.8 kN; 1,760 lbf) at 9,500 rpm

Specific fuel consumption: 14.4 kg/(kN·h) (1.44 lb/(lbf·h))

Thrust-to-weight ratio: 13.9 N/kg (1.42)"

Hermann Östrich

"The BMW 003 began development as a project of the Brandenburgische Motorenwerke (The Brandenburg Motor Works, known as "Bramo ") under the direction of Hermann Östrich and assigned the RLM designation 109-003 (using the RLM's "109-" prefix, common to all jet and rocket engine projects). Bramo was also developing another turbojet, the 109-002. In 1939, BMW bought out Bramo, and in the acquisition, obtained both engine projects. The 109-002 had a very sophisticated contra-rotating compressor design intended to eliminate torque, but was abandoned in favour of the simpler engine, which in the end proved to have enough development problems of its own."

Junkers Jumo 004 jet engine

"Turbojet, Junkers Jumo 004 B

Junkers Flugzeug- und Motorenwerke AG, Dessau, Germany, 1944

The first large-scale production of turbojets began with the Jumo 004B at the end of 1943. The development of the 004 engine was directed by Anselm Franz in Dessau from 1939 onwards. Series-production of Jumo 004A engine, designed for test purposes, started in sommer 1942.

8-stage axial-flow compressor, single stage turbine, 6 combustion chambers

Static thrust: 8.9 kN

Number of revolutions: 8700 rpm

Fuel consumption 1273 kg/h

Specific consumption 143 kg/kNh

Air flow: 21.2 kg/s

Compression ratio: 3.1"

Dr. Ing. Anselm Franz

"Dr. Ing. Anselm Franz, director of the gas turbine engine development at Junkers in Germany from 1940 to 1945 came to the US with Operation "Paperclip" in 1946 and became vice president and assistant general director at AVCO Corp. Lycoming Division in Connecticut were he continued his management efforts developing gas turbine engines. Most of the Lycoming gas turbine engines were designed by Franz and his team of engineers."

"Dr. Anselm Franz was place in charge of developing a new gas turbine engine for helicopters in 1952. The result was the T53, a light, powerful design that became Lycoming's most popular engine. T53s later drove the Bell UH-1 Huey and AH-1 Cobra helicopters and Grumman OV-1 Mohawk reconnaissance aircraft." /15/

Control System

V.3 Controls

"Lateral and longitudinal control was by single stage elevon control flap with 25% Frise nose and compensating geared tap balance. (This system was also used on the Horten VII)."

V.3 cockpit

"The pilots control column was fitted with a variable hinge point gadget, and by shifting the whole stick up about 2” the mechanical advantage could be doubled on the elevons for high-speed flight." /6/

Drag rudders in V.2

"Directional control was by drag rudders. These were in two sections, slight movements of the rudder bar opening the small (outboard) section and giving sufficient control for high speed. At low speeds when courser control was necessary the large movement also opened the second spoiler, which started moving when the small one was fully open. By pressing both feet at once, both sets of spoilers could be operated simultaneously; this was stated to be a good method of steadying the aircraft on a target when aiming guns."

V.1 cockpit

"The Hortens stated that the spoilers caused no buffeting and claimed an operating force of 1 kg for full rudder, with very little variation in speed. The operating mechanism is illustrated in the following figure. A change was made from the original Horten VII parallel link system to improve the control force characteristics. With the new system, aerodynamic forces could be closely balanced by correct venting of the spoiler web, leading the main control load to be supplied by a spring. The cover plate of the spoilers was spring loaded to form an effective seal with the rudders closed; this device was used on most Horten spoiler and dive brake designs." /6/

V-3 Drag rudder

"On further models of the H IX it was proposed to fit the “trafficator” type rudder tried experimentally on the H VII." (Possible due to the "one engine out" crash of V.2?) /6/

V.3 Control System

"Landing flaps consisted of plain trailing edge flaps (in four sections) on the wings, with a 3% chord lower surface spoiler running right across the center section, which functioned as a glide path control. The outer pair of plain flaps lowered 27° and the inner pair 30° – 35° on the glider version V.1. On V.2 mechanical trouble prevented the inner pair operating and all flying was done with the outer pair only." /6/

Center section spoiler

"The center section spoiler could be used as a high speed brake and gave 1/3 g at 950 km/h. No dive recovery flap was considered necessary." /6/

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:" /6/

Dimensions /6/

All Up Weight, Incl. Ammunition and Armor 8,500 kg (18,700 lbs.)
All Up Weight, Excl. 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 km/h (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 km/h (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 km/h (400-430 mph) were obtained on about 2/3 throttle opening. This appears to be the only flight test figure available." /6/

"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." /6/

"The Messerschmitt method was to base sweepback on the max t/c locus and to scale Mach number by the square root cos Ø." /6/

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." /6/

Heinz Scheidhauer, pilot of Horten IX V.1 (Göttingen 1944)

"D.V.L. (Deutsche Versuchsanstalt für Luftfahrt) 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." /6/

"The essence of the results was that the lateral oscillation was of abnormally long period – about 8 sec. At 250 km/h 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." /6/

"Lateral control was apparently quite good with very little adverse yaw." /6/

"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." /6/

"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." /6/

Me 163 Komet

"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 Horten 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”)." /6/

"The Horten 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." /6/

"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." /6/

Video about Horten glider tests 1935