Horten I, II & III

Horten I

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 centre 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°.

Horten II

This aircraft was of the same general layout as the H I but with sweepback increased from 19° to 26° and the lateral and longitudinal control combined in an elevon. Inboard flaps extending from elevon to centre section were used to increase maximum lift and drag for landing.

The first version was completed as a glider and the second fitted with an 80 hp Hirth engine driving a pusher propeller. 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. Subsequently there more gliders were built, the last being completed in 1937 after which the type was abandoned in favour 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 centre 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.

Appendix II (below) is a translation of Hanna Reitsch’s report on one of the H II gliders. It is clear from this 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° 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.

Appendix II
Flight Tests of the Horten II

The following is a translation of a German report on the flying characteristics of the Horten II and prepared by the well known Hanna Reitsch.

Flight Tests of the Horten II, D-11-187 on the 17.11.38 at Ranesdorf

The Horten II was tested by Hanna Reitsch (D.P.S. Darmstadt) at the request of General Udet.

The type tested was built in 1934 and has since been followed and improved by the types H III, H IV and H V. (The Horten III was successfully flown in 1938 Rhoen competitions and obtained a height of 8,000 meters (26,000’); it was destroyed in a hail storm but was flown again in 1939. The H IV and H V were completed in December 1938. The following report on the flying characteristics must not, therefore, be regarded as representing the present stage of development of tailless aircraft by the Horten brothers. The flying qualities do not correspond to present day designs. The following should however be noted: it possesses great static longitudinal stability and complete safety in relation to the spin.

Flying Characteristics

Since the builders of the Horten II did not have available sufficient raw materials for its manufacture, the resultant construction has made the testing very difficult. For lack of ball bearings the control surfaces are so heavy that measurements of stability cannot be carried out.

(A) Cockpit

(i) Comfort. Not exceptional.
(ii) View. View is bad since the edges of the cockpit hood cut off the view at eye level.
(iii) Entry and exit. Only possible for athletes.
(iv) Parachute arrangements. Satisfactory.
(v) Arrangement of the instruments. Not very satisfactory.
(vi) Arrangement and operation of the retractable undercarriage. Only possible for long armed pilots.
(vii) Friction of the control surfaces. Unsatisfactory

(B) Takeoff and Landing Characteristics


The carrying out of the normal takeoff technique is not recommended because of the long run that results. The takeoff is best carried out with fully back control column until the aeroplane rises from the ground without change of incidence. When two or three meters height is reached the control column may be put so forward so that the aeroplane attains a normal flying attitude. It is thought the long takeoff which otherwise results is caused by the unsatisfactory arrangement of the undercarriage.


Landing, even on a small field, is easily made by means of the landing flaps and use of the drag rudders on both sides so that they act as dive brakes. Landing run is normal.

(C) Balance and Stability

Balance and stability could not be adequately tested because the central column would remain in any position in which it was put because of friction. Static longitudinal stability is good.

(D) Controllability and Control Forces

Longitudinal Control

The motion is strongly damped. Loads are normal.

Lateral Control

The response is inadequate and unpleasant due to a large negative yawing moment which appears when the controls are displaced. The control forces could not be accurately judged due to the friction and also buffeting on the central column by gusts. This fluttering of the ailerons is probably caused by the lack of static balance of the central surfaces. The over balance of the controls also gives a feeling of lateral instability which however does no appear in calm air.

Directional Control

There are upper and lower surface spoilers on the outboard wing. When they are operated a response occurs suddenly. Operation of the directional control suddenly slows down the inner wing and the aeroplane turns immediately about both the vertical ad the longitudinal axes.
The relations between the forces on the three controls is not satisfactory.

(E) Turning Flight

Turns are only possible with difficulty. That is to say they are impossible with ailerons alone and can only be made using the drag rudder.


If strong drag rudder movement is applied, manoeuvrability is good. The true bank can not be easily obtained (it must be noted that the test pilot could not retract the undercarriage and this would adversely influence the banking properties.

(F) Side Slip

Side slipping cannot be carried out on the Horten II.

(G) Characteristics in the stalled flying condition

The aeroplane cannot by any sort of control movements be made to drop the wing or to spin. With the control column pulled right back the machine pitches slightly forward and sinks without reaching a speed of more than 90 kph. (This is a great help in blind flying when the instruments are iced up.)


The above failings are to be taken up with the Horten brothers with regard to further developments of the machine.

Darmstadt Airfield 12.11.38

Horten III

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 (23°) 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 unfavourable 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.

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 (Fig. 2)

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

IIIc Type (a), 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 centre 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.
Fig. 4a, Fig. 4b and Fig 4c show some views of the power H III construction with a belt drive to the propeller.

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. The scheme is sketched in Fig. 26. 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 by the writer 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 centre section with tandem seats. Specimens were found at Zimmern and Hernberg. This type was used for training purposes.

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 a H III.