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H, L, PITT
'
-
2,111,481
MEANS FOR CONTROLLING AEROPLANES WHEN IN FLIGHT
Filed Dec. 3, 1936
6
3 Sheets-Sheet l‘
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H. L. PITT
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2,111,481
MEANS FOR CONTROLLING AEROPLANES WHEN IN FLIGHT
I Filed Dec. 3, 1956
M. 4.
3 Sheets-Sheet_ 2
March 15, 1938.
H_ L_ PITT
2,111,481
PQEANS FOR CONTROLLING AEROPLANES WHEN IN FL‘IGHT
Filed Dec. 3, 1936
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3 Sheets-Sheet 3
Patented Mar. 1 5, 1938
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2,111,481
MEANS FOR CONTROLLING AEROPLANES
WHEN IN FLIGHT
'
Hubert Lewellen Pitt, Westcli?e-on-Sea, England
Application December 3, 1936, Serial No. 114,084
In Great Britain October '7, 1935
10 Claims.
(Cl. 244-42)
In known aircraft, directional and lateral con~
trol is achieved by the use of one or more vertical
at the wing tip and negative pressure or an in
crease of lift, according to the degree of open-7
rudders and ailerons hinged on the wings and
acting in opposite directions to each other; that
is to say, when one aileron is up the other is
down. These two control surfaces have to be
correlated, bythe skill of the pilot, in order to
achieve‘ correct turn and bank. Further, the
drag caused bylthe ailerons is greatest on that
10 wing which, being at the outside of the circular
path is travelling the faster, thereby inefficiently
resisting the ‘desired motion, and causing a
tendency for the aeroplane to spin at or near
the stalling point, These disadvantages are
15 present in aeroplanes with or without tails, if
having the usual control surfaces.
A prior proposal has been made to construct,
ing of the ori?ce by the control surface and the
relative velocity of the airstream caused to flow
through the ori?ce and past the control surface,
and thereby effecting a redistribution of pressure
between the lower and upper wing surfaces
through the ori?ce in which the control surface
is disposed.
The said angle Which the aXiS 0f the Control
Surface makes With the longitudinal axis of the
aircraft is measured from the longitudinal axis
outwards towards the front of the aircraft.
The term “SOIid” used above in connection with
the construction of the control surface means
that there is no passage for the air to flow
through the control surface and that the'air is
forced to flow over the upper and lower surfaces
0f the Control Surface. The term’ does not, of
Course, eXelude a Control Surface having a hollow
interior. Reference is made. above to the control surface not being greater in area than half
the area of the Wing. In the case of a continu
0115 Wing not interrupted by the fuselage the
expression “area of the wing” means the area
of that portion of the wing projecting outwards
each wing of an aeroplane of an Outer frame,
an inner frame and a single surface within the
20 inner frame, the construction being such that
the inner frame and single surface could be
turned in company about an axis at a, right angle
to the longitudinal axis of the aeroplane. The
inner frame and single surface together form the
25 major portion of the wing,
The disadvantage of any arrangement in
which a control surface is pivoted in an ori?ce
in a wing with its axis either at a right, angle
to the longitudinal axis of the aeroplane or par30 allel thereto is that forces will be produced which.
' will act with much greater effect about one par-
ticular axis than about another,
To overcome all the above mentioned disadvantages, according to the present invention I
provide an aeroplane comprising control surfaces,
each of which is not greater in area than half
the area of the wing and is mounted in an
ori?ce formed in the wing between the leading
and trailing edges of the latter, the control sur40 face being solid in construction and adapted to
be turned relatively to said ori?ce on an axis
which is directed forwardly and inclined to the
longitudinal axis of the aircraft at an angle
which is less than 90° to said axis, said control
‘i5 surface also being so constructed and arranged
that when turned from its inoperative position,
its leading edge projects downwards and forwards towards the leading edge of the wing
whilst its trailing edge projects upwards and
v
o0 rearwards; whereby air from the underside of
the wing is caused to flow both over the top surface and over the underside of the control surface rearwards or mainly rearwards and upwards through the orifice in the wing, thereby
causing either a destruction of lift, pressure loss
5
10
15
20
25
011 the port OI" Starboard Side as the case may he
beyond the adjacent outer surface or the level of
the adjacent outer surface of the fuselage‘.
When the Control Surface Opens the Ori?ce 30
through the Wing, it is adapted to Cause a rear
ward flow of the airstream from the high pres
sure area beneath the leading edge to the low
pressure area above the wing, so that Whatever
may be the forward and dOWHWM‘d Velocity of 35
the aircraft the Velocity of the air ?OW through
the ori?ce and, therefore, in front and behind
the control surface, must be at least as great or
greater since pressure equalization Will acceler
ate the flow from high to low pressure This 40
ensures that the Worse the‘ tendency for the wine
to stall, the more the ihelihetieh for this Pres
sure equalization to check all potential oscilla
tion about any axis even in vertical descent.
The said control surfaces have therefore as their 45
main object the simpli?ed and safe control of
the aeroplane, which is thus rendered substan
tially fool proof and enabled to descend and
ascend at an angle of ?ight path much steeper
than would otherwise be possible. Thus the 50
aeroplane can enter a very con?ned space almost
vertically under complete and unskilled control.
When both movable surfaces are actuated in
unison, the effect is to cause a tendency for the
rear portions of the wing, which are behind the 55
2
2,111,481
centre of gravity of the aeroplane, to drop, thus
creating an increase in the real angle of attack,
and to increase the sinking speed, whereby the
true angle of descent or glide can be varied with
out danger of stalling. Further, the pro?le drag
and the induced drag caused by the air-brake
action of the control surface and the boundary
layer separation when the control surfaces are
in the raised position creates additional drag and
In addition, the true
10 reduces the landing speed.
angle of attack of the wings and the landing
speed can be increased and decreased, respec
?eeting surface towards the Wing tip. As men
tioned above, the area of the control should not be
greater than half that of the wing and probably
about one-third will be the maximum proportion,
although this will depend upon individual re C7
quirements.
The control surfaces can be connected by
means of suitable mechanism to a steering wheel,
for example, in such manner that each of the
surfaces can be operated independently or both 10
simultaneously, as desired.
Several constructional forms of the invention
tively, at the moment before the aeroplane con
are shown diagrammatically and by way of ex
tacts with the ground, although, nevertheless,
ample on the accompanying sheets of drawings,
whereonz
15 the aeroplane still maintains a horizontal, or ap
proximately horizontal, attitude about the lat
eral axis at whatever angle of attack or sinking
speed.
.
When the control surfaces are operated inde
20 pendently, the drag and loss of lift occur on one
Fig. 1 is a fragmentary plan view of one of the
wings of an aeroplane of the tail-less type, with
the control surface mounted thereon;
Fig. 2 is a front View corresponding to Fig. l but
showing diagrammatically the control surface in
wing only and this, together with the turning
its raised or operative position;
moment caused by the angle of inclination of
the axis of the movable control surface to the
?ight path causes the desired directional con
trol with the required bank. If the axis of the
Figs. 3 to '7 are diagrammatic plan views of
modi?ed control surfaces, all of which are asym
metrical about their axes; but all of which have
a common feature of the front portion descending
through the wing and the rear portion upwards;
Fig, 8 is a diagrammatic end view of a further
variation in which the control surface is divided
in active position;
Fig. 9 is a diagrammatic plan View of a control
surface which is symmetrical or substantially
movable control surface is such as to constitute
a fully or partially balanced surface and the
lower part projects through and below the wing,
the down pressures of the air acting on that
30 part of the surface which sinks through the
wing when the control surface is operative tend
to reduce the operating loads for the control
surface and are therefore advantageous.
In a
turn and bank, therefore, the ?ve factors which
come into operation are loss of lift, induced
drag, pro?le drag, turning moment and down
pressure on the control surface, and all these
forces act on the inner wing only.
The control surfaces can be actuated by one
40 operating means only (e, g. a steering wheel)
and each surface performs the complete function
of two control surfaces on known aeroplanes, viz.
ailerons and rudder, and part of the function of
the elevator, in so far as variation in glide and
attack angle at landing is concerned.
The movable control surfaces may be so con
structed and arranged that when the surfaces
are in their inoperative positions, part or the
whole of their upper and lower surfaces form part
of the pro?le curvature of the upper and lower
wing surface, respectively, although the said up
per and lower surfaces could also be above or
below the wing surfaces. The control surfaces
are preferably nicely accommodated in ori?ces
formed in the wings.
When a control surface is
in its operative position, the leading part thereof
will project downwardly out of the ori?ce in the
wing whilst its trailing part will project upwardly
out of said ori?ce.
In plan view, the control surfaces may be of
many shapes. For example, they may be pear
shaped, with their smaller ends directed towards
the leading edges. The said surfaces may be
hinged on a central or noncentral axis and may
be fully or partially balanced, the said axis being
arranged preferably between 45° to 70° to the line
of flight or central axis fore and aft. In cross
section, said surfaces may conform to the cross
section of that part of the wing in which they are
?tted. If the control surfaces are centrally
hinged or fully balanced, the forward part of a
surface could be made to expose an ori?ce in the
wing as it descended below the surface and thus
be subject to down pressure whilst the other half
of the surface would rise so as to present a de
'
symmetrical about its axis;
Fig. 10 is a plan view of an aeroplane of the
tail-less type and shows a control surface of one
constructional form mounted on one of the wings
and a control surface of another constructional
form ?tted to the other wing.
In the constructional form of the invention
shown in Fig. 1 as applied to an aeroplane of the
tail-less type having swept-back wings, each wing
40
l is provided with a control surface 2 (hereinafter
called a “burbler”) which is pear-shaped in plan
and each burbler is pivotally arranged in a simi
larly-shaped ori?ce 3 formed towards the tip 4
of the wing. Each burbler is partially balanced
about a forwardly directed axis A-B which is
arranged at a suitable angle C (e. g. of from 45°
to 70°) to the line of ?ight X—X of the aircraft
or to the longitudinal axis thereof, the burbler
axis A—B in this instance being conveniently
inclined upwardly from its inner end to its outer
end as regarded from the front and as shown in
Fig. 2 although of course, in front elevation this
axis may take any angle as desired.
Each burbler is also asymmetrical in plan, the
portion forward of the axis being of greater area
than the portion aft of the axis. There is thus
a kind of large curved bulge 5 on the forward
portion adjacent to the tip of the wing and at
the extreme span of the burbler, the after por on
tion of the latter having a much smaller bulge 6
substantially opposite to the said larger bulge.
Each burbler is mounted so as to be turnable from
the position, see Fig. 1, in which it lies in and
across the ori?ce 3 in the wing up to the extreme
position in which it is at right angles to- the
chord, as shown in Fig. 2, or even at a greater
angle, for example 100°. Owing to the inclination
of the axis, the large bulge 5 on the forward por
tion describes an arc which is downward and 70
rearward whilst the bulge on the rear portion
describes an are which is upward and forward.
A convenient lateral spacing for the area centre
of each burbler is about three quarters of the wing
span reckoned from the root end or from the ad
75
3
2,111,481
jacent side or the level of the adjacent side of
the fuselage if the wing is a continuous, non
interrupted wing.
carried on a turnable shaft.
The latter is con
nected by rods, accommodated in the wing, to
a lever which is linked to a lever extending from
the under surface of the burbler. In order to
allow the burblers to be operated independently
or simultaneously, a compression unit (or other
idle, action means) is arranged to‘ connect the
two parts of each of the push-pull rods con~
turned. Such a control surface is bound to be I nected to the swing bar. The steering column,
effective in COlll'ltEI'i'fl‘?‘ any tendency of the airor. wheel mounting, is also arranged in such a 10.
craft to spin, the pressure on the burbler is in»
manner that it can be hinged bodily in a fore
creased and concentrated whilst control about and aft direction, thereby moving the swing bar
all axes should be possible at much greater than in the same direction and without being turned
critical angles without alteration (to any large. about its axis. This movement causes both bur
15 extent) of the centre of pressure, thus maintain
blers to be raised or lowered, as the case may 15
ing horizontal attitude longitudinally. Further, be. On the other hand, the steering wheel and
pressure is built up gradually and symmetrically, the mechanism connecting the same to the swing
increasing drag Without undue torsion or criti
bar is so mounted that the wheel is capable of
It will be appreciated that when the burbler
is turned on its axis, the airstream is diverted
from the high pressure area under the wing to
the low pressure area above it, through the ori
fice formed in the wing when the burbler is
cal moments.
.
In the modi?ed constructional form of the invention shown in Fig. 3, also applied to an aero
plane of the above mentioned type, the burb-ler
is pear-shaped in plan but in this construction
the inner end ‘i of the burbler is much narrower
25. than‘ that of the preceding construction. The
inner end of the burbler also terminates much
closer to the leading edge 8‘ of the wing.
The modi?ed construction of burbler shown
in Fig. 4 has its turnable axis A——B arranged at
20
. a very slight angle only to the leading edge 8 of
the wing. In this construction, the forward edge
9 of the burbler is practically straight. whilst the
trailing edge I is only slightly curved at H but
more steeply at E2‘ adjacent to the tip of the
wing. It will also be observed from the ?gure
that the burbler is asymmetrical about the axis
A~B as viewed in plan.
The burbler shown in Fig. 5 differs very con~
siderably in shape from any of the other bur
The burbler is asymmet
rical about its turnable axis A--B and its lead
ing edge mainly consists of a straight part l3
whilst its trailing edge is made up of .a slightly
inwardly-curved part i4 and a straight part it,
45 the latter and the part l3 being connected to
gether by a curved end portion 16 adjacent to
40 blers described above.
the tip of the wing.
,
In the construction shown in Fig. 6, the lead
ing and trailing edge comprise, respectively, sub
50 stantially straight portions El .and !8, the por
tion it’ being almost parallel to the turnable
axis A—-B whilst the portion I8 'is arranged at
a greater angle to the axis. 7 The inner ends of
55
60
65
75
the two edges are joined ‘by a curved part 55 and
the outer ends by a curved part 20.
In the construction shown in Fig. 7, the bur
bler somewhat resembles that shown in Fig. .6,
except that the leading edge 2! and the trailing
edge 22 are joined by an outwardly-bulged part
23. The burbler shown in Fig. 7 is also squatter
than that shown in Fig. 6.
The modi?ed control surface shown in Fig, 9
differs from the preceding control surfaces in
that it is symmetrical about its turnable axis
or substantially so, the leading edge 33 and the
trailing edge 36 each being curved almost to the
same radius. The inner end 35 of the control
surface is almost pointed whilst the outer end
is well rounded.
The burblers (of any of the kinds described
above) .are arranged to be operated either inde
pendently or simultaneously, for example, by
means of a single steering wheel operatively
connected to a swing bar, each end of which is
connected to a two-part push-pull rod to a lever
. turning relatively to the wheel mounting and
of pivoting the swing bar about its axis. In this 20
manner, only one of the two‘ burblers is actuated,
the other remaining vin its inoperative position.
Additional safety means (e. g. springs) may be,
provided for ensuring that the burbler shall re
turn to, its inoperative position in the event of 25
the failure of one of the, compression units.
In the further modi?ed construction shown
in Fig. 8, the burbler is divided in its action.
That is to say, either part 24 or 25 of the burbler
on either side of the axis 26 may be operated
whilst the other part remains stationary or one
part may be operated in advance of the other
part. If the burbler is thus arranged it will be
possible, if desired, to fold it backwards or for~
wards so that either the front or the rear half
of the ori?ce in the wing i will be uncovered.
' Fig.
10 shows two constructional forms of
burblers ?tted to the wings of a tail-less aero
plane.
The two different constructions of bur
blers are only shown on the ?gure to illustrate 40
the positioning of the burblers on the wings. It
will be understood, of course, that the two bur
blers ?tted on the same aeroplane would nor
mally be the same in construction.
The air flow takes place through the wing
past the front and back of the control surface
from below to above, i. e. from the high pressure
area under the leading edge to the low pressure
area at the rear of the top of the wing. The
steeper the ?ight path, i. e. the greater the angle
of attack of the wing, the greater the diiference
in pressure becomes and consequently the faster
must be the flow of the 'airstream through the
ori?ce in the wing and past the control surface.
Thus, the worse the stalling tendency the more
the inclination for the control surfaces to equal
ize pressure distribution. The problem of steep
descent is not one of lift but of stable equilibrium
and control of balance whilst lift is being re
duced to a minimum. Even if vertical descent
is attempted the control surfaces could not stall
45
50
55
60
but must hold the aircraft about all axes of con»
trol.
Movements of the centre of pressure laterally,
vertically and fore and aft can be de?nitely ‘con 65
trolled and varied in different designs by suitable
variation in the balance of the control surface
about its axis, its symmetry, section, outline and
curvature. For instance, particularly in the
types shown in Figs. 3, 4 and 5, a de?nite increase’ 70
of lift’ and forward movement of the centre of
pressure may take place thus causing a. climbing
angle during the ?rst slight opening of the con
trol surface. A subsequent larger opening of the
control surface can, however, cause a loss of 75
2,111,481
lift and slight rearward movement of centre of
pressure thus slightly putting the nose down
and at the same time a loss of lift and steep
flight path is taken up.
Thus, with this type
of control surface gradual and most accurate
controlled variation of the lift-drag ratio for
any given speed or angle of attack is made pos
sible by the degree of opening and closing of
the control surface and its nature relative to
10 various types of design can be greatly varied in
sofar as its plan outline, position of axis, total
affect the increase of drag and the relative lift
variation. For example, see Fig. 4, a small area
each side of the axis, and the axis at a maximum
angle to line of flight causes a large variation in
lift values, a considerable increase in lift when
slightly open at high speed, but further opened,
a rapid decline in lift with not very great
in drag. Therefore, a fast and steep
and a fast and steep descent, but both
more human control, since the control
increase
take-off
needing
and the 10
changes in lift-drag ratio are rapid and sensitive.
On the other hand, a large area each side of the
area, and so on is concerned.
In the case of my invention the control sur
face will set obliquely inside the wing area in
15 such a manner that the inequality of pressure
axis, and the angle of axis nearer 45° gives very
little increase of lift accompanied by a bigger
proportion of drag when slightly open and a rapid 15
between the top and bottom surfaces itself con
tributes to safe control, whilst pressure losses
and very large increase or drag as more and more
open, but with a, more slowly graduated loss of
around the control surface are minimized.
lift more firmly under control, giving a slow but
The
variation in the values of lift and of drag and
20 of the lift-drag ratio is possible under complete
and fool-proof control of the pilot. This gives
fairly good climbing take-off, but a very slow and
very easily ‘controlled descent, steep or carefully 20
regulated under simple and widely graduated lift
a safe balance about all axes in any weather
drag ratios.
conditions.
The term “aeroplane” is of course intended to
cover non-power driven and power-driven gliders
and although the invention has been described 25
above with reference to an aeroplane of the tail—
The controllable variation in lift
drag ratio takes place without important change
25 in the centre of pressure position except as may
be desired by the control surface, because these
changes are themselves dependent in inverse
ratio to the speed of the aircraft and the air-
flow velocity through the orifice and past the
The centre of pressure auto
matically adjusts itself to the centre of‘ gravity
30 control surface.
movements to a very much greater extent than
on known aircraft. For the same reason parasitic
drag is absent and the control acts only in a
manner required to produce the effect desired.
As regards the area of the control surface and
its position on the wing, if the area of the con
trol is too great in comparison with the: rest
of the wing area, the loss of lift will be too great
and dangerous and the relative increase of drag
too much, thus causing loss of control and sta
bility. If the area of the control is too small
then the effectiveness and control and the lift
drag variation will be too weak and the object
will be lost.
It is therefore suggested that one-third of the
wing area will be about the maximum proportion
for the area of the control surface, but this may
be varied to suit individual needs. If the control
surfaces are located too close to the centre of
gravity they lose effect and must be of larger
area. They can have some effect wherever placed,
but most effect is probable when situated furthest
from the wing root possible. Whether the sur
face is symmetrical or not is immaterial in prin
ciple, but has a different relative effect. It is es
sential that the lower leading edge should pro~
ject below the wing surface and the upper rear
edge above it, so that the airflow is directed as
required and previously described on both sides
of the control. The proportions of the surface
in plan either in front or behind the axis is
therefore to be determined by the prime features
of design and performance aimed at for (a) the
65 amount of drag required at different speeds (b)
the amount of lift increase and decrease required
at different speeds (0) relative movements of the
mean centre of pressure both fore and aft and
vertically and laterally, because a larger surface
less type, to which the invention is particularly
applicable, it is also applicable to aeroplanes hav
ing tales and to aeroplanes having the normal
controls, viz. ailerons, elevators and rudders, and 30
also to continuous, non-interrupted wings. The
invention will be capable of development as a
means of steepening the glide and increasing the
take-off lift of heavy bombing or transport air
craft, and in particular it will lend itself to the
improvement in the control, stability, gliding and
climbing angle of sea-planes of the central hull or
flying boat type, which would thus be able to dis
pense with the usual tail and control surfaces.
The invention will also be found to be of con 40
siderable importance in the stabilizing of model
aeroplanes and gliders, keeping them on an even
keel and ensuring efficient directional, longitudi
nal and lateral control.
What I claim is:—
1. Means for controlling an aeroplane in
flight, comprising wing structure provided with
an ori?ce adjacent each tip thereof and be
tween the leading and trailing edges thereof,
a control surface in each ori?ce and means 50
for turning said surface, the latter being pear
shapecl and asymmetrical in shape about its
turnable axis as viewed in plan and having
non-apertured outer surfaces and not greater
in area than half the area of the wing and 55
mounted in said ori?ce for turnable movement
relatively thereto on a pivot axis which is di
rected forwardly and inclined to the longitudi
nal axis of the aeroplane at an angle less than
90° to said longitudinal axis, and said control 60
surface also being so constructed and arranged
that when turned from its inactive position, its
leading edge can only project downwards and
forwards towards the leading edge of the wing
whilst its trailing edge projects rearwards and 65
upwards, whereby air from the underside of the
wing is caused to flow both over the top surface
and over the underside of the control surface
rearwards or mainly rearwards and upwards
70 in front of the axis than behind can result in
through the ori?ce in the wing thereby causing
a downward movement of the vertical centre of
pressure (or a lowering of the mean centre of
resistance) and vice versa. This can, of course,
either a destruction of lift, pressure loss at the
wing tip and negative pressure, or an increase
change the trim of the aeroplane.
The actual
75 area of the control on each side of the axis can
m
of lift, according to the degree of opening of the
ori?ce by the control surface and the relative
velocity of the airstream caused to flow through 75
5
the ori?ce and past the control surface, and there
by effecting a‘ redistribution of pressure between
the lower and upper wing‘ surfaces through the
ori?ce in‘ which the control surface is disposed.
2. Means for controlling an aeroplane in ?ight,
comprising wing structure’ provided with an ori
?ce adjacent each tip thereof and between the
leading and trailing edges thereof, a control sur
face in each ori?ce and means for turning said
10 surface, the latter being solid in construction and
not greater in area than half the area of the
wing and mounted in said ori?ce for turnable
movement relatively thereto on a pivot axis which
is directed forwardly and inclined to the longim
15 tudinal axis of the aeroplane at an angle of from
45° to 70° to said longitudinal axis and said con
trol surface also being so constructed and ar
ranged that when turned from its inactive posi
longitudinal axis of the aeroplane, each control
surface as viewed in plan having a large curved
bulge on the forward portion adjacent to‘ the tip
of the wing and at the extreme span of the con
trol surface, and the after portion of the latter
having a much smaller bulge substantially oppo
site to the said larger bulge.
4. Means for controlling an aeroplane in ?ight
comprising wing structure having an: ori?ce
therein at each side of the longitudinal axis of 10
the aeroplane and between the leading and trail
ing edges of the structure, a control surface piv
otally mounted in each ori?ce and asymmetrical
in shape’ about its pivotal axis as Viewed in
plan and having a continuous bounding surface, 15
said control surfaces having an area less than
half- the adjacent area of the wing with said pivot
axis directed forwardly and inclined to the longi
tion, its leading edge projects downwards and for
20' wards towards the leading edge of the wing whilst
its trailing edge projects rearwards and upwards,
whereby air from the underside of the wing is
tudinal axis of the aeroplane at an angle less
than 90° to said longitudinal axis, and each said
control surface being so constructed and arranged
that when turned from its inoperative position
caused to ?ow both‘ over the top surface and over
the ‘underside of the control surface-rearwards
the leading edge always projects downwardly and
forwardly toward the leading edge of the wing
whilst its trailing edge projects rearwardly and
upwardly, whereby air from the underside of the
or mainly rearwards and upwards‘ through the
ori?ce in the wing thereby causing either a de
struction of lift, pressure loss at the wing tip and
negative pressure, or an increase of lift, accord
wing is caused to ?ow over both the top and bot
tom ‘sides of said control surface rearwardly or
ing to the degree of opening» of the ori?ce by the
mainly rearwardly and upwardly through the
at: control surface and'the relative velocity of the
351
airstream caused to ?ow through the ori?ce and
past the control surface, and thereby effecting a
redistribution of‘ pressure between the lower and
upper wing surfaces through the ori?ce in which
the control’ surface is disposed, and the approxi
mate area center of each control surface being
located on the wing structure at about three
quarters of the span reckoned from the root end
of the wing, whereby the control reaction of the
control surface will have substantially a maximum effective moment arm. about the fore and‘
aft axis of the craft.
3. Means for controlling an aeroplane in ?ight
comprising wing structure having an ori?ce
45 therein at each side of the longitudinal axis of
the aeroplane and. between the leading and trail
ing edges of the structure, a controlsurface piv
otally mounted in each ori?ce and asymmetrical
in shape about its pivotal axis as viewed in
plan and having a continuous bounding surface,
each said control surface having an area less.
than half the adjacent area of the wing with said
pivot axis directed forwardly and inclined to the
longitudinal axis of the aeroplane at an angle
less than 90° to said longitudinal axis, and each
said control surface being so constructed and
arranged‘ that when turned from its inoperative
position the leading edge always projects down
wardly and forwardly toward the leading edge of
60 the wing whilst its trailing edge projects rear
wardly and upwardly, whereby air from the un
derside of the wing is caused to flow over both the
top and bottom sides of said control surface rear
wardly or mainly rearwardly , and upwardly
65 through the ori?ce in the wing thereby causing
either a destruction of lift, pressure loss at the
wing tip and negative pressure, or an increase of
lift, according to the degree to which the ori?ce
is opened by the control surface and the relative
70 velocity of the air stream caused to flow through
the ori?ce and past the control surface, to there
by effect a redistribution of pressure between‘ the
lower and upper wing surfaces, said control sur
' V faces being‘ somewhat pear-shaped in plan and
~ having their narrower ends directed towards‘the
ori?ce in the wing thereby causing either a de 30
struction of lift, pressure loss at the wing tip and
negative pressure, or an increase of lift, accord
ing to the degree to which the ori?ce is opened
by the control surface and the relative velocity
of the air stream caused to flow through the
ori?ce and pastthe control surface, to thereby
effect a redistribution of pressure between the
lower and upper wing surfaces, said control sur
faces being somewhat pear-shaped in plan and
having their narrower ends directed towards the 40
longitudinal axis of the aeroplane, each control
surfaceras viewed" in plan having a narrow for
ward portion extending rearwards for about one
third of the length of said surface, a large curved
bulge on its trailing edge and a smaller curved 45
bulge on its leading edge, the forward end of the
pivot axis of the control surface being arranged
relatively near to the leading edge of the wing.
5. Means for controlling an aeroplane in ?ight
comprising wing structure having an ori?ce
therein at each side of the longitudinal axis of
the aeroplane and between the leading and trail
ing edges of the structure, a control surface piv
otally mounted in each ori?ce and asymmetrical
in shape about its pivotal axis as viewed in plan
and having a continuous bounding surface, each
said control surface having an area less than half
the adjacent area of the wing with said pivot
axis directed forwardly and inclined to the longi
tudinal axis of the aeroplane at an angle less
than 90° to said longitudinal axis, and each said
control surface being so constructed and ar
ranged that when turned from its inoperative
so5
position the leading edge always projects down
wardly and forwardly toward the leading edge of
the wing whilst its trailing edge projects rear
wardly and upwardly, whereby air from the un
derside of the wing is caused to ?ow over both
the top and bottom sides of said control surface
rearwardly or mainly rearwardly and upwardly
through the ori?ce in the wing thereby causing
either a destruction of lift, pressure loss at the
wing tip andnegative pressure, or an increase of
lift, according to the degree to which the ori?ce
is opened by the control surface and the relative
To
6
2,111,481
velocity of the air stream caused to flow through
the ori?ce and past the control surface, to there
by effect a redistribution of pressure between the
lower and upper wing surfaces, said control sur
faces being somewhat pear-shaped in plan and
having their narrower ends directed towards the
longitudinal axis of the aeroplane, each control
surface as viewed in plan having a substantially
straight leading edge arranged relatively near to
the leading edge of the wing and at a slight angle
only thereto and a slightly-curved trailing edge,
a steep curve connecting the leading and trailing
edges adjacent to the tip of the wing.
6. Means for controlling an aeroplane in flight
comprising wing structure having an ori?ce
therein at each side of the longitudinal axis of
the aeroplane and between the leading and trail
ing edges of the structure, a control surface piv
otally mounted in each ori?ce and asymmetrical
20 in shape about its pivotal axis as viewed in plan
and having a continuous bounding surface, each
said control surface having an area less than half
the adjacent area of the wing with said pivot
axis directed forwardly and inclined to the longi
tudinal axis of the aeroplane at an angle less
than 90° to said longitudinal axis, and each said
control surface being so constructed and arranged
that when turned from its inoperative position
the leading edge always projects downwardly and
forwardly toward the leading edge of the wing
whilst its trailing edge projects rearwardly and
upwardly, whereby air from the underside of the
wing is caused to flow over both the top and bot
through the ori?ce in the wing thereby causing
either a destruction of lift, pressure loss at the
wing tip and negative pressure,‘ or an increase
of lift, according to the degree to which the ori
?ce is opened by the control surface and the rela
tive velocity of the air stream caused to flow
through the ori?ce and past the control surface,
to thereby effect a redistribution of pressure be
tween the lower and upper wing surfaces, said
control surfaces being somewhat pear-shaped in 10
plan and having their narrower ends directed to
wards the longitudinal axis of the aeroplane, each
control surface as viewed in plan having substan
tially straight leading and trailing edges, the
leading edge being substantially parallel to the 15
pivot axis of the control surface and the trail
ing edge being arranged at a greater angle to
said axis and curved parts joining said leading
and trailing edges.
8. Means for controlling an aeroplane in ?ight 20
comprising wing structure having an ori?ce
therein at each side of the longitudinal axis of
the aeroplane and between the leading and trail
ing edges of the structure, a control surface piv
otally mounted in each ori?ce and asymmetrical 25
in shape about its pivotal axis as viewed in plan
and having a continuous bounding surface, each
control surface having an area less than half
the adjacent area of the wing with
directed forwardly and inclined
tudinal axis of the aeroplane at
than 90° to said longitudinal axis,
said pivot axis
to the longi 30
an angle less
and each said
control surface being so constructed and ar
tom sides of said control surface rearwardly or
ranged that when turned from its inoperative
mainly rearwardly and upwardly through the
position the leading edge always projects down 35
ori?ce in the wing thereby causing either a de
struction of lift, pressure loss at the wing tip and
negative pressure, or an increase of lift, accord
ing to the degree to which the ori?ce is opened
wardly and forwardly toward the leading edge of
the wing whilst its trailing edge projects rear
wardly and upwardly, whereby air from the un
40 by the control surface and the relative velocity
of the air stream caused to ?ow through the ori
derside of the wing is caused to ?ow over both
the top and bottom sides of said control surface 40
rearwardly or mainly rearwardly and upwardly
?ce and past the control surface, to thereby effect
through the ori?ce in the wing thereby causing
a redistribution of pressure between the lower
either a destruction of lift, pressure loss at the
wing tip and negative pressure, or an increase of
lift, according to the degree to which the ori?ce 45
is opened by the control surface and the relative
velocityof the air stream caused to ?ow through
the ori?ce and past the control surface, to there
by effect a redistribution of pressure between the
lower and upper wing surfaces, said control sur
faces being somewhat pear-shaped in plan and
having their narrower ends directed towards the
longitudinal axis of the aeroplane, each control
surface as viewed in plan having substantially
and upper wing surfaces, said control surfaces
45 being somewhat pear-shaped in plan and having
their narrower ends directed towards the longi
tudinal axis of the aeroplane, each control surface
as viewed in plan having a leading edge which
mainly consists of a straight part and a trailing
50 edge made up of a slightly inwardly-curved part
and a straight part, the latter and the leading
edge being connected by a curved end portion
adjacent to the tip of the wing.
7. Means for controlling an aeroplane in flight
55 comprising wing structure having an ori?ce
therein at each side of the longitudinal axis of
the aeroplane and between the leading and trail
ing edges of the structure, a control surface piv
otally mounted in each ori?ce and asymmetrical
60 in shape about its pivotal axis as Viewed in plan
and having a continuous bounding surface, each
said control surface having an area less than
half the adjacent area of the wing, with said
pivot axis directed forwardly and inclined to the
65 longitudinal axis of the aeroplane at an angle
less than 90° to said longitudinal axis, and each
said control surface being so constructed and ar
rarged that when turned from its inoperative
position the leading edge always projects down
70 wardly and forwardly toward the leading edge of
the wing whilst its trailing edge projects rear
wardly and upwardly, whereby air from the un
derside of the wing is caused to flow over both
the top and bottom sides of said control surface
75 rearwardly or mainly rearwardly and‘upwardly
straight leading and trailing edges, the leading
edge being substantially parallel to the pivot axis
of the control surface and the trailing edge be
ing arranged at a greater angle to said axis and
curved parts joining said leading and trailing
edges, and wherein the forward ends of the lead 60
ing and trailing edges of each control surface are
joined by an end part which is only slightly
curved outwardly.
9. Means for controlling an aeroplane having a
wing and a body structure in flight comprising
control surfaces pivotally mounted in ori?ces in the
wing structure adjacent the tips thereof and be
tween the leading and trailing edges thereof, with
the pivot axis of the surface extending at an angle
with respect to the longitudinal axis of the plane
of more than about 45° and less than about 70°,
said surfaces each corresponding in its transverse
cross-section to the surface contour of the wing
at the location of the ori?ce and being substan
tially pear-shaped in plan, said surfaces being 75
2,111,481
movable so that their leading edges project down
ward only, and actuating means for selectively,
individually or jointly moving the‘ control sur
faces so that each leading edge when in actuated
position always extends downwardly and for
wardly with respect to the wing.
10. Means for controlling in ?ight an aero
plane including a wing having ori?ces formed
therein adjacent the tips thereof and a body
structure; comprising control surfaces each sur
7 r
parts extending at an angle with respect to the
longitudinal axis of the plane, one part of each
‘surface extending above and another part there
of extending below the wing structure, each 'part
being so arranged that it cannot move through
the ori?ce to the other side of the wing, the parts
of said surfaces being relatively movable so that
their extreme outer edges may project forwardly
or rearwardly, and actuating means for selective
ly, individually or jointly moving the parts of 10
face including two relatively movable parts piv
the control surfaces so that their outer edges
otally mounted on a common pivot in each ori
when in actuated position may extend forwardly
or rearwardly with respect to the pivot.
?ce in the wing structure adjacent the tips there
of and between the leading and'trailing edges
15 thereof, with the pivot axis of the surface and its
HUBERT LEWELLEN PITT.
15
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