Aircraft

Horton Ho VII

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The H VII was projected in 1938 and the first of the type was built by Peschke at Minden in 1943. It bears a general resemblance to the modified H V in layout and control design and used the same outer wing panels: the span was the same (16m) the sweepback slightly greater (34 degrees) and aspect ratio 5.8 instead of 6.1. Its function seems to have been that of a high speed two-seater communications aeroplane and trainer for tailless pilots. Engines were Argus AS 10 C of 179kW / 240 hp.
Altogether two were completed and flown and a third was nearing completion at Minden when the district was occupied by the Allies. Two aircraft were damaged beyond repair and the third fell into Russian hands at Eilenburg.
Single stage elevon control was used on the H VII with 25% Frise nose and geared tab. Inboard of the elevons was a plain flap and in the middle trailing edge split flaps extending for the full width of the center section. Initially the graded flap angle principle was used, the part between the engines opening to 60 degrees, between the engine and the outer wing panels to 45 degrees, and the plain flap on the wing lowering to 20 degrees. When R.L.M. ordered the design in quantity however they asked for it to be simplified and for landing speed to be raised to give pilots more realistic training for high speed aircraft. The plain flap was accordingly locked up on the second aircraft and omitted altogether on the series production model.
Plug spoiler drag rudders of the H IV type were used on the first aircraft. These tended to suck open and had to be held closed by springs. They were not very satisfactory from the point of view of control forces and feel, and after about 10 flights they were scrapped and replaced by a new “trafficator” design. This was simply a bar which projected 40 cm in a spanwise direction from the wing tip when rudder was applied and retracted flush with the wing surface when not in use. Vent holes were cut to adjust aerodynamic balance. The vent holes allowed flow through the bar and deflected the flow sideways to generate a self-closing aerodynamic force. This was supplemented by a spring loading and the two components adjusted to give satisfactory feel on the rudder bar. This type of rudder was claimed to be cheap and easy to make and generally more satisfactory then previous designs.

The center section being of welded tube construction and the wings of single spar wooden construction with ply covering.
The undercarriage was a completely retractable four-wheel layout, the front wheel pair taking about 50% of the total weight when resting on level ground.
The constant speed airscrews were driven through extension shafts with a thrust ball bearing and rubber flexible coupling at the engine end and a self aligning ball bearing at the airscrew end mounted on a cantilever form the main structure.
Outer wing panels were of the same aerodynamic shape as those of the H V. At the center line the section was 16% thick with 1.8% camber (zero Cmo) graded to 8% symmetrical tip sections. Wing twist was 5 degrees; 2 degrees linearly and 3 degrees parabolically distributed. The aircraft trimmed with elevons neutral at 260 kph (CL = 0.16).

The following performance data were quoted by Reimar Horten from memory:
Flying weight (minimum) 2,900 kg
Flying weight with full equipment 3,200 kg
Engines 2 x 240 hp Argus AS 10 C (normally aspirated)
Sea level (crusing speed (180-200 hp per engine) 310 kph
Sea level (top speed) 340 kph
Normal take-off speed 110 kph
Ground run 250 meters
Sea level rate of climb at 180 kph (full power) 7 m/sec.
Ceiling 6,500 meters
CLmax = 1.2 no flaps
CLmax = 1.6 with all flaps
Delta CL due to plain flap was 0.1

Reimar Horten said that prior to the first flights at Scheidhauer on the H VII, his brother Walter had supervised the CG’ing of the aircraft and mistakenly put ballast in the nose because the measurements were made with a steel tape with 10 cm missing from the end. Scheidhauer’s commented that the aircraft had to be brought in at a minimum speed of 120 kph, with the stick nearly right back, if the nose was to be lifted for the hold off; the aircraft then floated (stick fully back) until 90 kph before touching down. Normal take-off procedure was to accelerate to 120 kph and then pull the stick back when the aircraft immediately took off and climbed away. Apparently it could be unstuck at 90 kph by pulling back hard but would not climb until 120 kph had been reached. It was impossible to stall the aircraft with the CG in this position; the general behavior was said to be “good natured”.
Walter flew the H VII (with the CG in its correct position) on 30-40 occasions, a total flying time of about 18 hours. (Scheidhauer’s time was also about 18 hours). Apparently the change in CG brought the approach speed down to about 100 kph and the aircraft could be touched down on the rear wheels. It was not certain that a complete stall could be produced in steady flight. With the stick fully back the aircraft sank on an even keel with fair lateral control. Lateral control was pleasant, the 25% Frise balance eliminated adverse yaw and virtually enabled flying on two controls.
Tests with the “trafficator” drag rudder showed that single engine flight could be maintained with half rudder and a little sideslip; turns could be made in level flight against the dead engine. On one test the pilot was carrying out a single engine approach when he realized that he had stopped the engine supplying the undercarriage hydraulics and could not lower the wheels. He was able to climb away, start the dead engine and made a normal landing.

Ho-VII
Engine: 2 x Argus As-10, 180kW
Max take-off weight: 2000 kg / 4409 lb
Empty weight: 1550 kg / 3417 lb
Wingspan: 16 m / 52 ft 6 in
Length: 7.5 m / 24 ft 7 in
Height: 2.5 m / 8 ft 2 in
Wing area: 44 sq.m / 473.61 sq ft
Max. Speed: 350 km/h / 217 mph
Crew: 2

Horton Ho VI

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In general layout of the Ho.VI was very similar to the H IV. The span was increased to 24 m (78.7’) accompanied by a decrease of 5% in wing area, giving an aspect ratio of 32.4.
The object in building the H VI was to achieve the most efficient high performance sailplane regardless of cost. Two were built and the first was tested late in 1944. It was performance tested by the relative sinking speed method previously described, using a calibrated H IV for the second glider. The Hortens were very pleased because it was better than the D 30 (same span and wing loading) over the whole speed range.
Aerodynamically there were no new features of special interest compared with the H IV. Wing sections and control systems remained the same. The structural design had to be refined in order to get sufficient bending strength in the very thin cantilever. The main spar was made up of laminations of plain wood and “bignefel” (a compressed impregnated wood) to give extra strength at the root, and a special wing root fitting using four taper pins in place of the normal two was devised to distribute the concentrated loads at the root. The torsion box design was modified also to increase the wing torsional stiffness, since at high speed it had been found that an unstable short period longitudinal oscillation, involving wing twist, could develop. The speed at which the damping of this oscillation became zero on the H VI was found to be about 180 kph.

The H VI is of interest only as a high performance sailplane for record breaking purposes. It is too costly and difficult to handle for general use.
The second aircraft of this type built was found intact near Horsfeld; the first aircraft was found destroyed near Gottingen, where it had been flying.

Ho-VI
Wingspan: 24.2 m / 79 ft 5 in
Wing area: 17.8sq.m
Empty weight: 330 kg / 728 lb
Gross Weight: 410kg
Payload: 80kg
Wing Load: 23kg/sq.m
Aspect ratio: 32.4 to 1
MinSink: 0.45 m/s 70 kph
L/DMax: 45 83.5 kph
Seats: 1

Horton Ho V

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The H V was designed form the outset as a powered aircraft using two Hirth H.M. 60 R motors driving oppositely rotating propellers through extension shafts. It has a span of 52.5 feet, aspect ratio of 6:1, and a quarter chord sweepback of 32 degrees. Engines were completely buried and drove propellers on extension shafts raised relative to the engine crankshaft and driven through a reduction gear. The undercarriage was of fixed tricycle type with castoring nose wheel and trousered main wheels. The nose wheel actually too 55% of the static weight when on level ground.
Three examples were built. The first, built at Ostheim in 1936 was constructed of plastic material with riveted sheet plastic covering. Pilot and passenger were contained entirely in the wing contour and the nose wheel was retractable. This aircraft crashed on its first flight, due mainly to its unorthodox waggle-tip control. The second version used more normal control methods and conventional construction, it was started in 1937 and flew successfully. In 1941 it was completely rebuilt as a single-seater, but retained the same control system.
In its original form the H V was fitted with waggle tip control in which the fore and aft sweep of the wing tips was geared to the stick, producing incidence change by a skew hinge arrangement. The aircraft crashed on it first flight due to the control taking charge after a bounce during landing. The reason for the accident was obscured by a failure of one engine but the control system was not regarded as satisfactory by the Hortens who later developed the idea further on an H III. They considered that damping is necessary to prevent the tips oscillating under suddenly applied acceleration (as occur during take off and landing).
The second aircraft in both its forms had a two stage elevon control rather similar to the H III. Maximum control deflections were as follows:

The outer control flaps had a 20% Frise nose and assymmetrically geared tabe to compensate the non linear moment characteristics of the nose balance. The inner flap pair had round noses.
Split trailing edge flaps were fitted to the center section, the flap between the engines lowering to 60 degrees and the part outboard to 45 degrees. The inner elevon flaps dropped to 30° when the center section flaps were lowered and still operated as elevons about this new zero position. The idea of using graded flap deflections originated from a hunch of the Hortens that the sudden discontinuity and greater spanwise flow with ungraded flaps might cause stability and control troubles. They later found that this fear was unfounded and gave up the graded deflection principle.
Rudder control on the second two aircraft was by split nose flaps on the H III pattern.
A great deal of flying was done on the second and third H V’s, including about twenty flights on the latter in 1943 by Prof. Stuper of A.V.A. Gottingen. The Hortens themselves had lost interest in the H V because later designs incorporated many improvements. Stuper has also flown the H IIId with Walter Mikron engine.
Tests at A.V.A. were undertaken at the request of D.V.L. who wanted information on single engine characteristics and an unbiased comparison between tailless and conventional handling qualities. Stuper’s comments were as follows:
Longitudinal dynamic stability was good and no fundamental different from a conventional aircraft could be noticed. In rough air he thought it had a more abrupt pitch response than normal, which was only a disadvantage if gun platform steadiness was needed. (Walter Horten thought this effect might be due to the low wing loading (6 lb/sq.ft.) on the H V and Stuper agreed that this might be so).
Lateral stability appeared satisfactory. No tendency to “dutch roll” instability was found and no arratic changes of heading due to low Nv and Yv were noticeable. Stuper was in fact expecting trouble from this source but failed completely to find any. He added that his impressions were purely qualitative as they had no time to instrument the aircraft.
Controls were light and effective, with the exception of the rudder, which was heavy and not effective enough. Aileron was heavier than the elevator “in the ratio 4:3”. With the stick back, aileron movement was restricted, which Stuper thought a bad point since plenty of aileron was useful in an approach in gusty weather. The aircraft was in trim virtually over the whole speed range without movement of the elevator trimmer. When flaps were lowered there was a slight nose heavy tendency which could easily be held.
Summing up, Stuper said that aileron and elevator control were quite normal but rudder control needed improvement.
Behavior at the stall (flaps down) was very satisfactory, the nose dropped gently and the aircraft gained speed. Wing dropping could be induced if the aircraft was stalled in a yawed attitude but normally the wings remained level and ailerons still effective, thought restricted in movement. The stall was reached with the stick not quite fully back; only one CG position was tested. Stalling speed was about 70 kph.
Flight on one engine was possible, without rudder, at 120 kph by flying with 10 degrees of bank and 80% aileron. Rudders were not used much because they were so heavy, although Walter Horten claimed that at 130 kph single engine flight could be maintained on rudder only (engine nearly at full power) if the pilot was strong enough.
Ground maneuvering was easy using throttles and wheel brakes. During take-off the aircraft could quite easily be kept straight until the drag rudders became effective, and flew itself off the ground without assistance from the pilot – in fact it made very little difference what the pilot did with the controls during take-off. There was no tendency to bounce during the ground run. R.L.M. require that for normal tricycles, it should be possible to left the nose wheel before take-off speed is reached; Walter Horten thought this was unnecessary if the aircraft would fly itself off. Landing was quite straightforward and normally the aircraft settled down on all wheels at once. Stuper thought it was not possible to land on the main wheels first because the ground incidence was too high.
Stuper had done some tests of take-off performance with flaps down, which resulted in his flying into a hanger and terminating the A.V.A.test programme. Apparently he landed and immediately (Walter Horten said not immediately) opened up to take-off again – after 530 meters he was 8 meters high and at that point entered the hanger. The airborne distance was about 150 meters.
Although the split flaps in front of the propellers caused poor thrust, there were apparently no vibration problems.
Summarizing his impressions on the H V, Stuper said that it was hardly fair to compare it with conventional aircraft with many years more development behind them but it was nevertheless, a good example of tailless design and a perfectly practical aeroplane – if anyone wanted tailless aeroplanes. His main suggestion for improvement was in the rudder control.

Ho-V
Wingspan: 16 m / 52 ft 6 in
Max. speed: 260 km/h / 162 mph

Horton H IV

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Ho.4b

The Ho IV was built primarily to investigate the effects of high aspect ratio. Two Ho IVs were built, one of which crashed after entering a spin.

Horton H IV Article

The span was the same as that of the H III but aspect ratio was increased from 10.7 to 21.1, and the control system further developed. In order to retain their finless wing layout and get the maximum aerodynamic efficiency, the pilot was put in a prone position with his body in a 27% thickness ratio egg and his knees and legs in a small leg well. The well also supported the rear skid (or wheel in the case of the H IVb).
An example of the HIV was found at Göttingen in good condition and was brought back to R.A.E. for test flying. It has completed 500 hours flying since its construction in 1942, including a cloud flight of 1-hour on instruments; such a flight demonstrates that stability and control and the comfort of the prone position must be satisfactory.

The three stage control flaps were all geared to the spectable type control wheel and operated on the same general principle as the earlier two flap control on the H III. The following table gives the (measured) flap movements corresponding to full control by the pilot.

It will be seen that the outer flap works principally as up going aileron whereas the “climbing elevator” action comes mainly from the middle flap and “diving elevator” action from the inner flap. Down going aileron, needed to neutralize pitching moments, comes from the inner and middle flaps together.
The center and inner flaps were unbalanced, with round noses, the tip flaps Friese balanced with a skew hinge giving 39% balance at the inboard end and zero balance at the tip. This scheme gave the required aileron yawing moments without making the control flap at the tip vulnerable when a wing tip scraped the ground.
Drag rudders were of the upper and lower surface spoiler type placed immediately ahead of the outer control flap; the upper surface spoiler had a vented web. To open the rudders the pilot had to press with his toes, moving the foot from the ankle against a spring loading on the pedals which gave “feel” to the control. By pressing both feet together he could open both rudders simultaneously, thus giving extra drag for glide control. Rudder operation was said to cause no buffeting of the control flaps. The movement transmission from the pilot’s pedal included a cam plate cut to give no rudder movement for negative movement of the pilot’s foot (i.e., pressure on the opposite pedal) and an approximately linear relationship between pedal movement and rudder projection for positive movement (i.e., pressure on the pedal).
All controls were operated by push rods, the inner and central flaps and the drag rudders being moved by skew-hinge cantilevers. In the IVb the skew hinge principle was extended to the outer flap operation also. The method of operating the control flaps was simple to construct and eliminated all external control horns.
Longitudinal trim was obtained by an internal bungee “spring” which can be adjusted to take any out-of-balance aerodynamic loads on the elevator control.
There were no landing flaps by large spoiler type dive brakes were provided, which could be used to give variable drag for glide path control.
The H IV used reflexed cambered sections (zero Cmo) of R.A.F. 34 type, changing to assymetrical section at the wing tip.
The large wing dihedral of 5 percent was used to give adequate wing tip clearance. Reimar Horten considered that aerodynamically this might be on the large side but advisable for practical reasons. It should be remembered that both the H III and H IV have an abnormally low value for the lateral relative density Uso that unusual values of Lr and Nv would be permissible without dynamic instability resulting.
Performance was measured by flying the H IV against the D 30, a conventional high performance glider which had been carefully performance tested by D.V.L. to form a “standard”. The essence of the method was to two both aircraft up together and let them glide down from about 10,000’ at a series of speeds, measuring the relative height photographically, at intervals. From these tests the best gliding angle of the H IV was found to be 1 to 37 and the minimum sinking speed 1.7 ft/sec. Minimum sinking speed was slightly less than the D 30, but at high speeds the d 30 was better.
Scheidhauer, Horten’s chief test pilot, has done the majority of the flying in Horten IV’s (about 1000 hrs) and his comments are worth recording. He was a strong advocate of the prone position – in his own words “it has nothing but advantages.” All H IV controls he described as very light, he flew the glider with “two fingers”. The elevator was apparently rather sensitive compared with the aileron but not unpleasantly so. Aileron application produced no adverse yaw – a definite improvement after the II and III – and could reverse a 45 degree banked turn in 5 secs. at 70-90 mph, which is better than the average sailplane. Longitudinal stability he thought satisfactory but he commented on a “wiggle” which was produced by flying through gusts; this is apparently a sharper pitch response than for a conventional sailplane, but well damped, quite harmless and requiring no corrective action by the pilot. A true stall could not be produced with normal elevon adjustment because of increasing static stick fixed stability at the stall, which used up available elevator power before the wing tips were stalled. Spins could only be produced by applying full aileron and rudder with the stick hard back; recovery was easy.
Stability and controllability on tow were excellent. Scheidhauer described a competition in which a number of sailplanes were aero-towed form Grunau through the very turbulent air in the “standing wave” from a nearby mountain; the rough air had to be negotiated on tow to get to the area of rising currents. All the instructors from the school at Grunau were flying conventional sailplanes and broke their two lines without exception. Scheidhauer in his H IV managed to get through and soar in the standing wave. He attributed his success partly to his own skill and partly to the good controls of the H IV plus his ability to use the tip rudders together to check surging in the tow rope.
Take-off seems to present some problems to a pilot new to the aircraft. It seems that the short undercarriage base, responsive elevator and small wing tip clearance can produce a very erratic take-off if the pilot is not smooth and precise in his control movements.
Construction followed the normal Horten practice, but the wing panels were made with detachable tips of sheet clektron. This was necessary because the narrow chord at the tip made accurate construction in wood very difficult. The center section was of welded steel tube, with perspex nose and a large jettisonable access cover behind the main spar.
The front skid was retractable and fitted with a wheel which automatically dropped off as the skid retracted.
The pilot’s harness was modified from the original version, being a single broad strap passing under the buttocks. This was released by the same handle that jettisoned the access cover. The pilot’s parachute was stowed in a pocket on the cover and connected to the pilots harness by short straps. In this was the pilot was relieved of the weight of the pack, which would otherwise have caused some discomfort on a long flight.
Flying instruments included a low reading A.S.I. driven by a venturi, electrical turn and bank indicator, sensitive variometer, high reading variometer, altimeter and clock.
Oxygen equipment comprised two bottles, pressure gauges, reducing valve and economizer, and provision was made for electrically heated clothing. Ventilation was under the pilot’s control.
The pilot position could be adjusted for varying pilot size and a chin rest with adjustment for height was provided. The pilot was prevented from sliding forward by shoulder rests and the reaction of his thighs against the knee well. Comfort appeared to be satisfactory when we tried the bed but elbow and shoulder movement was restricted which constrained one to stay in the same position all the time.

Superficially the IVb resembles the IV very closely but the aerodynamic changes were a fundamental experiment. The Hortens intended to produce a laminar flow sailplane with superlative high speed performance – in this they were partially successful but they sacrificed too much on the stability and control to make the venture a real success. Production had been started, prematurely, at the rate of about two a month.
Wing sections were derived from the Mustang section which had been measured by D.V.L. for captured aircraft and tunnel tested. The Hortens were excited by the low tunnel drag figures and designed the H IVb to exploit them. The root section was the original Mustang profile, changing to an uncambered section with the same fairing shape but reduced thickness at the tip. Wing twist was reduced (compared with the IV) to 5.6 degrees to get the greatest spanwise extent of laminar flow, and sweepback reduced to 2 degrees to get the CG farther back relative to the mean chord (this was necessary because the aerodynamic center of the basic wing section was farther aft). It is interesting that although Cmo was not zero for the root section, the high aspec ratio enabled the glider to be designed to trim, elevons neutral, at the required top speed (140 mph) without needing excessive twist.
The wing structure ahead of the main spar was a ply sandwich monocoque with Tronal filling. Tronal was an expanded wook with specific gravity 0.1 to 0.09, invented by a Dr. Barschfeld of Dynamit A.G., Troisdorf (near Cologne). The sandwich was made up on molds, with outer ply 1 mm thick and inner ply .8 mm; the filling was 20mm at the root tapering to 5 mm at the tip. The nose sections were stuck onto the front of the main spar with supporting ribs every 2 meters. Between the main and rear spars normal ply covering was used, insufficient Tronal being unavailable for sandwich construction all over.
Waviness in a chordwise direction was not controlled or measured. Sag (spanwise) between ribs had been measured on the IV and eliminted on the IVb. Special care was taken to kep dust off the wings; wing dust covers were made and all handling was done with gloves on.
Control circuit mechanism remained the same except for the outer flaps which were also operated by a skew hinge lever on the IVb. The dive brakes were moved back to the rear spar to suit the revised wing structure
No transition measurements were made on the IVb, but it was flown against a calibrated IV and the following relative sinking speeds measured.

The change of section raised the stalling speed from 45 kph on the IV and to 60 kph on the IVb.
The handling characteristics were very unsatisfactory. A wing tip stall occurred followed by wing dropping and spinning. The first aircraft crashed for this reason after the pilot got into trouble in a cloud. An attempt was made to improve matters on the second glider by clipping the span from 20.25 meters to 18.5 meters but results were disappointing. As a cure on the final design a reversion to the old H IV tip section was proposed, the theory being that section stalling characteristics were bad due to the sharp nose radius. Partial breakaway behind the maximum thickness point was suggested, aggravated by spanwise boundary layer drift which rendered the elevon ineffective. Horten thought the small wing tip Reynolds number made the use of low drag sections inadvisable.

Professor Dezso George-Falvy of Mississippi State University in a German Horten Ho IV glider – one of two to survive the Second World War. (1960)

Horten H IV
Wing span: 20.3m
Wing area: 18.9sq.m
Empty Weight: 250kg
Payload: 80kg
Gross Weight: 330kg
Wing Load: 17.5kg/sq.m
Aspect ratio: 21.8
L/DMax: 37 73 kph
MinSink: 0.5 m/s 60 kph
Seats: 1

Horten IV b
Wing span: 20.3m
Wing area: 18.9sq.m
Empty Weight: 270kg
Payload: 80kg
Gross Weight: 350kg
Wing Load: 18.5kg/sq.m
Aspect ratio: 21.8
L/DMax: 40
Seats: 1

Horton H III

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In 1938, with this official backing, the Hortens set up a facility at Berlin’s Tempelhof Airport, where they constructed the Ho III sailplane.
The first H III was built at Templehof Berlin in 1938 and the second (H IIIb) was built by Peschke Flugzeugban, also in Berlin. The main change from H II were increase span (20 m), reduce sweepback (23degrees) and modified lateral controls. The outer wing panels this time had three movable flaps. The innermost was again a landing flap, but the outer pair were geared so that the outer flap had a large range of upward deflection and, only slight downward movement and, the inner flap large downward movement and slight upward movement. This arrangement reduced unfavorable yawing moments due to aileron by making use of differential aileron movement, but avoided the change in longitudinal trim by the opposing differential of the inner flap pair. In high speed flight the nose down trim was provided mainly by the inner elevon section moving downwards, the outer flap deflecting only slightly; this had the advantage of relieving the tips of torsional loads at high speed. Aerodynamic balance was again by geared tab on sub types IIIa and b, but on IIId, f, and g the outer flap had a 20% Friese nose: out of balance aerodynamic loads on the elevators were trimmed by a rubber bungee trimmer.

Ho.IIId

Drag rudder design remained the same as for the H II.

The H III seems to have been a successful and useful type, for 14 were built altogether and several different sub-types developed. Production of some of the sub-types was still going on in 1945. The following variations on the original theme were produced:

IIIa – Original design

IIIb – Similar, but with outer elevon flap not extending to the wing tip.

IIIc –

Same as IIIa but with a fixed front plane. One of these was built, for the 1938 Rhon contest. Very little flying experience was obtained. The idea was to improve CLmax.

IIId – Standard wings fitted to a special center section with 32 hp Volkswagen engine and folding propeller. The idea was to produce a high performance sailplane with auxiliary engine for takeoff and climb, which could be shut off for soaring without impairing the performance as a sailplane.
Center sections (Opel engine with gear drive) were being produced at Tubingen at the rate of two a month. 12 partly finished were in the workshop in June 1945. Finished parts were sent to the Wornberg and assembled with wings made at Darnsdorf.
Performance with power was stated to be:
Ground run: 70 meters
Rate of climb: 2 m/sec.
Cruising speed: 110 kph
Max. speed: 130 kph
The engine installation was take straight from the Volkswagen complete with exhaust system and electric starter; it weighed 240 lbs.

IIIe – H III glider with waggle tips. On this aircraft, remains of which were found at Gottingen, the tips were operated directly by the pilot.

IIIf –

Same as the IIIb, but with prone position for the pilot. A specimen of this type was found at Gut Nierstein with modified controls. The outer flap had a Frise nose, (as on H IV), spoiler type drag rudders were fitted in place of the usual leading edge split flaps, and H IV type dive brakes installed.
The prone piloting position eliminated the need for the head fairing used on the other H III’s and gave the pilot a much better view.

IIIg – Special two-seater center section with tandem seats. Specimens were found at Zimmern and Hernberg. This type was used for training purposes.

H IIIh / Ho-229 – One built in 1944.

No independent opinions are available on the flying qualities of the H III series, but Reimar Horten was insistent that it was a very straightforward aircraft from the pilots point of view. He stated that any glider pilot with five hours experience could be safely sent off solo in an H III.

Horten H III a
Wing span: 20.4m
Wing area: 36sq.m
Empty Weight: 220kg
Payload: 80kg
Gross Weight: 300kg
Wing Load: 8.3kg/sq.m
Aspect ratio: 11.6
L/DMax: 28 60 kph
MinSink: 0.48 m/s 45 kph
Seats: 1

Horten H III c
Wing span: 20.4m
Wing area: 36sq.m
Empty Weight: 220kg
Payload: 80kg
Gross Weight: 300kg
Wing Load: 8.3kg/sq.m
Aspect ratio: 11.6
L/DMax: 28 60 kph
MinSink: 0.48 m/s 45 kph
Seats: 1

Horten H III f
Wing span: 20.5m
Wing area: 37.5sq.m
Empty Weight: 280kg
Payload: 80kg
Gross Weight: 360kg
Wing Load: 9.6kg/sq.m
Aspect ratio: 11.1
L/DMax: 28 63 kph
MinSink: 0.52 m/s 47 kph
Seats: 1

H IIIh
Wingspan 54 ft.
Length 16.4 ft.
Height 5.4 ft.
Empty weight 586 lb
Loaded weight 807 lb
Wing area 344 sq. ft.
Wing loading 2.25 lb/sq. ft.
Glide ratio 24:1
Aspect ratio 8.48
Max speed 143 mph
Best glide 45 mph

Horton Ho II Habicht

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The Horton Ho.2 was of the same general layout as the H I but with sweepback increased from 19 degrees to 26 degrees and the lateral and longitudinal control combined in an elevon. Inboard flaps extending from elevon to center section were used to increase maximum lift and drag for landing.
The first version was completed as a glider and the second fitted with a 60kW / 80 hp Hirth engine driving a pusher propeller in 1935. In this aircraft the pilot was seated in a reclining position and completely contained in the wing contour; a maximum level speed of 210 kph was achieved. This was tested in 1938 by Hanna Reitsch and attracted the attention of Ernst Udet, Director of the Technical Department of the German Air Ministry, who made funds available for further development.

Subsequently there more gliders were built, the last being completed in 1937 after which the type was abandoned in favor of the H III.
The root wing section was change from the 20% symmetrical H I type, to a 20% section with reflexed camberline (zero Cmo) changing along the span to a symmetrical tip section. A balance tab was fitted to lighten the controls which were all pushrod operated.
The structure was in three parts, as in all subsequent Horten designs. The center section being the welded tube and the outer panels of wood with a D-nose spar. The wheel undercarriage had brakes and the front wheel was retractable. Drag rudders consisted of lending edge flaps (as on the Horten III) opening against a spring.

From a translation of Hanna Reitsch’s report on one of the H II gliders, it is clear that lateral and directional control were still only partially satisfactory although characteristics at the stall were excellent. This feature is remarkable, for although a wing twist of 8 degrees was used the effect of the high taper and sweepback might be expected to overpower the beneficial effect of twist in delaying the tip stall.

Ho.II
Wing span: 16.5m
Wing area: 32sq.m
Empty Weight: 220kg
Payload: 80kg
Gross Weight: 300kg
Wing Load: 9.4kg/sq.m
Aspect ratio: 8.5
L/DMax: 24 72 kph
MinSink: 0.7 m/s 60 kph
Seats: 1

Ho-IIM
Engine: 1 x Hirth ÍÌ60R, 60kW
Max take-off weight: 450 kg / 992 lb
Empty weight: 330 kg / 728 lb

Ho-IIM

Horton Ho I

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Reimar and Walter Horten started out with models, then progressing to gliders and eventually to powered aircraft. Their first tailless design, the Ho I sailplane. This was built at Bonn during the year 1931-1932 and had a flying life of about 7 hours.
It had a span of 40 ft. and a wing loading of 2 lb/sq.ft. The control system comprised a control flap giving elevator control and normal ailerons at the wing tip. Directional control was by leading edge drag rudder at the wing tip.
All the control flaps were hinged at the upper surface with a circular arc lower leading edge forming a seal with the wing. There was no aerodynamic balance.
The wing section was symmetrical throughout and thick enough (25% C) at the center section to house most of the pilots body. His head projected from the upper surface and was faired by a perspex cockpit cover. A rubber mounted skid formed the undercarriage.
The control system was unsatisfactory and was changed on subsequent aircraft. It seems to have been impossible to stop a slow speed turn by use of ailerons alone and the drag rudder, which at first was on the lower surface only, was ineffective and caused a nose down pitching moment. When an upper surface flap was added to cure this the braking action became too fierce and springs had to be incorporated to make the control heavier. Reference was made to a yawing tendency at low speed which could result in an uncontrollable turn through 360°.
The Ho I sailplane, won a prize at the 1934 Rhon soaring competitions, but the brothers were not satisfied with its performance and burned it.

Ho.1b

Ho.1
Wing Span: 12.4m
Wing Area: 21sq.m
Aspect ratio: 7.3
Empty Weight: 120kg
Payload: 90kg
Gross Weight: 210kg
Wing Load: 10kg/sq.m
L/DMax: 21 @ 72 kph
MinSink: 0.80 m/s 60 kph
Seats: 1

Horten H I b
Wing span: 12.4m
Wing area: 21sq.m
Empty Weight: 120kg
Payload: 90kg
Gross Weight: 210kg
Wing Load: 10kg/sq.m
Aspect ratio: 7.3
L/DMax: 21 72 kph
MinSink: 0.8 m/s 60 kph
Seats: 1

Horten Gebruder

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Walter and Reimar Horten conducted flying-wing experiments prewar, building a series of tailless high-performance gliders. The Horten Ho V and Ho VI were both powered aircraft, leading to the turbojet-powered Ho IX flown in the summer of 1944. Before being destroyed in a landing accident after only a few hours flight, it had been flown at a speed of 800km/h. This was developed by Gothaer Waggonfabrik as the Gotha Go 229 V3 single-seat fighter, but the Gothaer works were captured by advancing U.S. forces before this prototype was completed.

Horton Aircraft HW-X-26-52 Wingless

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The Horton Wingless aircraft was invented by William Horton of Huntington Beach, California in 1952. He called the strange-looking plane “wingless” because he claimed the entire craft was a simple air foil with vertical fins and utilized all surfaces for lift. Unfortunately, Horton did not have the money to develop it, but was able to get into a partnership with billionaire Howard Hughes and Harlow Curtis.

The aircraft was a welded steel frame covered with a fabric skin and powered by two Pratt and Whitney R985 radial engines. Instead of a long high aspect ratio wing the fuselage was to create the lift and tip plates which he called ‘sealers’ were to tip losses that otherwise plague such airfoils. Essentially it was a highly-modified Cessna UC-78 with a more airfoil-shaped fuselage than wing.

Registered N39C, the aircraft logged around 160 hrs of flight time before Bill Horton had a falling out with Hughes. Horton was railroaded to prison.

Although this innovative prototype flew successfully, no backers were attracted. The venture failed not because the airplane didn’t fly, but because Hughes wanted to take full credit for the patents and production rights, which Horton refused to allow. Hughes sued Horton which effectively stopped any further development of the aircraft. Hughes managed to have the prototype and partially-constructed production version moved to the bone yard at the south end of the Orange Co airport and deliberately burned.

Horton Aircraft Corporation

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Horton Aircraft was organized in 1952 for the purpose of engaging in the business of manufacturing and selling a so-called “Horton Wingless Airplane.” Its only asset was said to be a patent issued to William E. Horton, its president, with respect to the wingless plane and assigned by him to the company. Horton had agreed to assign the patent rights to the company for 500,000 shares of its stock, and to build and sell a model of the plane to the company for an additional 200,000 shares. The company’s entire personnel consisted of three directors, including Horton; and it had more than 800 stockholders. The first registration statement filed April 26, 1955, proposed the public offering of 400,000 shares by the company and 100,000 shares held by Horton, at $1 per share or the market price, whichever was higher. The second, filed October 18, 1956, proposed the public offering of 100,000 shares held by Horton at $25 per share.

The aircraft was designed and built by Bill Horton in a three way partnership with Howard Hughes and Harlow Curtice of General Motors. Horton had a falling out with Hughes.

The Securities and Exchange Commission announced the issuance of a “stop order” decision suspending the effectiveness of two registration statements filed by Horton Aircraft Corporation, of Las Vegas, Nevada, because of false and misleading representations contained in the registration statements, which proposed the public offering of 500,000 and 100,000 shares, respectively, of Horton Aircraft stock.

According to the Commission’s decision, Horton “had no patent rights or patent he could validly assign” to the company and it was at least doubtful whether he could legally sell a model of the wingless plane to the company because of a June, 1954 court decision upholding the validity of an earlier assignment to another company of Horton’s interest in his “invention” of the wingless plane. Furthermore, the Commission ruled that false and misleading statements were made in the registration statement with respect to the nature and performance of the wingless plane. The plane was represented as having no wings and it was stated that a model constructed by Horton in 1954 had been test-flown continuously and its performance had equalled Horton’s expectations.

The Commission found that the wingless plane in fact had wings which extended about 8 feet from the fuselage and had a depth of 5 to 6 feet, and that these wings, although retractable had never been retracted in flight. “The registration statements should have disclosed,” the Commission stated, “that the Horton plane, which was remodelled from a standard airplane, has in general performed in a manner inferior to that of a conventional plane Horton has used as a basis for comparison, that his plane admittedly was not built to fly any distance and the test flights were short, the longest flight being about 150 miles, that the maximum speed of the plane was about one-half that of another plane using the same motors, and that it had never been tested for range or load-carrying capacity. The second registration statement should have further disclosed that the prototype has not been test flown since it crashed in landing in June, 1955.

Moreover, the statement that the plane’s performance has equalled Horton’s expectations is misleading in view of statements made in brochures and form letters which Horton caused to be prepared and circulated by registrant in connection with previous sales of unregistered stock. Those statements, which were false and misleading, were to the effect that Horton’s development of the Horton Wingless Plane is comparable to the achievements of the Wright brothers, Leonardo da Vinci, Sikorsky, Billy Mitchell, and Charles Lindbergh; that his plane is one of the greatest aeronautical engineering achievements of all ages and the greatest advance in aviation since the advent of flying; that it can carry 100% greater payload over 100% greater range and is faster and easier to control than any other plane, and can carry twice the load at half the cost of any other plane; and that the Horton Wingless Jumbo Transport plane will carry 4,000 persons a distance of 25,000 miles non-stop) at 60,000 feet altitude, at speeds of over 400 miles per hour.”

The Commission also found false and misleading the disclosures in the registration statements with respect to past stock sales without prior registration, the selling costs of the proposed offerings, and the proposed use of the proceeds of the financing, as well as the implications that the $25 per share price of the second offering was based upon and related to some reasonable valuation of the stock.

Horton Aircraft and Horton were permanently enjoined by the United States District Court in Los Angeles in September, 1954 from making false and misleading statements in the sale of Horton Aircraft stock. Horton was convicted on March 8, 1957, of fraud in the sale of Horton Aircraft stock and sentenced to 3 years’ imprisonment followed by 5 years’ probation.