1. * GB780074 (A)
Description: GB780074 (A) ? 1957-07-31
Aeroplane stabilizer
Description of GB780074 (A)
PATENT SPECIFICATION
u Haf> Date of Application and filing Complete
Specification: July 27, 1954.
Complete Specification Published: July 31, 1957.
Index at acceptance:-Class 4, C4, D5.
International Classification:-BU4d.
COMPLETE SPECIFICATION
Aeroplane Stabilizer I, MAXIMILIAN CHARLES JANISCH, of Village
Gladebeck 41, Sandkreis Gottingen, Germany, a German Citizen, do
hereby declare the invention, for which I pray that a patent may be
granted to me, and the method by which it is to be performed, to be
particularly described in and by the following statement: -
This invention relates to the stabilising of aeroplanes.
Many of the accidents which occur to aeroplanes are thought probably
to be due to insufficient stability because the centre of gravity of
the system is too high. As is well known, if an aeroplane flies on a
curved path, the speed of the outer wing, and thus the lift produced
by it, is greater than that of the inner wing. This difference in lift
gives rise to a rolling moment, i.e., causes the aeroplane to turn
about its longitudinal axis, which is larger, the larger is the
difference in lift of the two wings. This.difference increases as the
radius of curvature of the flight path decreases. If the turn is made
so small that the outer wing has double the speed of the inner wing,
the air pressure on and thus the lift produced by the outer wing
becomes 22, i.e., four times that of the inner wing. If the rolling
moment becomes so large that the wings are turned too far out of the
horizontal, the wings lose their lift and the aeroplane may stall and
crash. In favourable conditions the pilot may be able to effect a
recovery but in some conditions this is difficult if not, impossible.
In all aeroplanes the stabilising moment tending to restore the

2. aeroplane into the proper position is too small because the centre of
gravity of the system is too high. The more this centre of gravity can
be displaced downwards by some kind of device, the greater becomes the
distance between the centre of gravity and the centre of pressure,
i.e., the point through which passes the resultant of the aerodynamic
forces on the wings, and the greater the [Price 3/6] 780,074 No.
21881/54.
radius of action of the restoring moment. The position is similar to
that in an ordinary kite, the centre of gravity of which is displaced
substantially downwards by providing it with a long tail of string
having paper strips 50 spaced along and secured to it. Accordingly, I
propose to provide an aeroplane with a stabilising weight which is
suspended below the aeroplane to displace the centre of gravity
downwards to such an extent that the radius 55 of action of the
restoring moment is such as always to turn the aeroplane back into the
horizontal position.
As most accidents happen on take-off and landing, because pilots are
liable to fly round 60 the airfield at too short a radius of turn, the
stabilising weight is preferably made so as to be capable of being
raised and lowered.
Moreover, in order that a turn of too small a radius should not be
made, the angle by 65 which the rudder may be moved by the pilot is
preferably restricted by means of a stop (the precise value may be
determined by experiment).
The above and other features of the invention are illustrated in the
accompanying diagrammatic drawing which is a front elevation
illustrating by way of example one way of carrying it into effect.
Referring to the drawing, 1 and 2 are the 75 port and starboard wings
of the high-wing monoplane illustrated, and 3.its fuselage or body. 4
is the stabilising weight which is suspended on two flexible wire
ropes or cables 5 and 6, the lower ends of which are 80 secured to
eyes on the weight 4. The two cables 5 and 6 pass up to the tips of
the port and starboard wings 1 and 2, at which tip each cable passes
over a roller or pulley 7 and 8 respectively. Thence, the cables pass
85 to the drum of a winch 9, which is conveniently arranged in the
pilot's compartment.
and on which drum they can be wound up or from which they be unwound,
the drum 9 being driven by an electric motor (not 90 780,074 shown)
supplied with operating current from a generator driven by the main
power plant of the aeroplane. In good weather the stabilising weight 4
is raised until it lies close against and under the fuselage 3 of the
aeroplane, as shown in the upper position 4' in the drawing, when
40-50 meters of the cable wire is wound up on the drum on each side.
The centre of gravity of the system, which has been displaced

3. downwards by the stabilising weight 4, is assumed to be at G in the
drawing. F is the centre of pressure through which acts the resultant
of the aerodynamic forces on the wings. If the aeroplane rolls or
turns about its longitudinal axis by the angle p as shown, F moves to
F, and a couple is produced. The forces producing the couple are the
total weight P acting from above downwardly through G; and, acting
upwards from below through F1, the supporting counter-force R of the
same magnitude as the resultant of the lift forces.
The restoring or righting stability moment depends on the one hand on
the total weight of the aeroplane or the lift R, and on the other hand
on the distance of the centre of gravity G (which has been displaced
downwards by means of the stabilising weight) from the point of action
of R (the resultant of the aerodynamic forces) at F and the sine
multiplied by the cosine of the angle of tilt.
As, at constant speed, the lift R supporting the aeroplane becomes
rapidly smaller with increasing angle of tilt, the angle of tilt is
the dangerous factor to which the pilot must pay attention. With a
maximum rotation or tilt of 90 (a right angle) out of the horizontal,
R becomes zero as there is no longer a lift component. The aeroplane
capsizes over the wing-tip. The resultant R of the aerodynamic forces
on the wings acts at F and is situated at the under-edge of the wing.
The centre of gravity G of the system (total weight) moves downwards
when the stabilising weight is lowered.
According to the principle:
If in a system of weights one of them is displaced, the position of
the centre of gravity of the system changes and the path of the centre
of gravity of the system is parallel to the path of the displaced
weight. The relation between the paths is the reverse of that of the
weights, that is, the path of the centre of gravity of the system is
related to the path of the displaced weight as the displaced weight is
related to the total weight.
If the stabilising weight is lowered down to about 30 meters and if
the stabilising weight is from 1% to 2%, of the total aeroplane
weight, then the displacement of the overall centre of gravity would
correspond at 1% to 300 mm, at 2% to 600 mm. If it is let down to 50
meters, there results a displacement at 1% of 50 cm, at 2% of 1 meter.
The difference is therefore quite considerable and completely
justifies the introduction of the stabiliser for reasons of safety.
Crashing or even capsizing of the aeroplane as a result of loss of
stability can no longer take place because of the considerable
downward 70 displacement of the centre of gravity of the system and
the increase in stability thus effected. As, in the event of a
relatively large angle of tipping. the wire of the stabilising weight
on the downwardly-inclined 75 side becomes loose, double the

4. downwardlydirected force is exerted on the wing which has been moved
upwards, and this gives a further substantial increase in the
stability moment. 80 The stabilising weight should be lowered shortly
after take-off and shortly before landing. During ordinary flight it
should be lowered only if the weather is stormy, or there are rain or
snow squalls, or if it is 85 foggy. Otherwise, it is kept drawn up
close to the body or fuselage of the aeroplane so that during calm
weather it does not offer a resistance which would substantially
decrease the speed of the aeroplane. 90 In order to prevent the
aeroplane from crashing on a rising slope of a hill, the stabilising
weight is provided with an electric alarm device, including a
contact-operating member on the weight. such that when the 95 lowered
weight comes against the slope (the weight will meet the slope in
advance, because it hangs down by 40-50 meters) the contact member is
moved to close a circuit, as a result of which an alarm bell arranged
100 near the pilot's seat sounds, or a warning light lights up. The
weight may be provided with several contact-operating members
distributed around it so that at least one is operated in whichever
direction the weight 105 strikes the obstruction.
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