V, VI, and VII
H V was designed form the
outset as a powered aircraft using two Hirth H.M. 60 R motors driving
oppositely rotating propellers. 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 (Fig.
13c) as a single-seater, but
retained the same control system.
In its original form the H V was fitted with waggle tip control (Fig.
26) in which the fore and aft sweep of the wing tips was geared to the
stick, producing incidence change by a skew hinge arrangement similar to
the illustrated in Figs. 26 & 27.
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
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:
Control Column Port Starboard
Position Outer Inner Outer Inner
Fully left -20 -2 +20 +2
Fully forward +5 +30 +30 +5
Fully back -40 -5 -5 -40
The outer control flaps had a 20% Frise nose and asymmetrically 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 centre section, the flap
between the engines lowering to 60° and the part outboard to 45°. The
inner elevon flaps dropped to 30° when the centre 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
Rudder control on the second two aircraft was by split nose flaps on the H
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. We questioned him extensively about his impressions of the
aircraft (Sept. 21, 1945), because it was the most recent Horten product
he had flown. 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 erratic 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
Summing up, Stuper said that aileron and elevator control were quite
normal but rudder control needed improvement.
Behaviour 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.
Single Engine Flight
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.
Landing and Take-off
Ground manoeuvring 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
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 ti 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
In general layout of this aircraft 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
The second aircraft of this type to built was found intact near Horsfeld; the first aircraft was found destroyed neat Gottingen,
where it had been flying.
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 240 hp.
shows the general arrangement.
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 centre
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. 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.
This followed normal Horten practice, the centre section being of welded
tube construction and the wings of single spar wooden construction with
The undercarriage was a completely retractable four-wheel layout, the
front wheel pair taking about 50% of the total weight when resting on
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 centre 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
= 1.6 with all flaps
Delta CL due to plain flap was 0.1
Reimar Horten told us that prior to the first flights 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 comments to us
were 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
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 behaviour
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
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