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Патент USA US2113000

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April 5, 1938. ,
D. c. ROWE,
Filed May 17, 1933
Patented Apr. 5, 1938
Donald C. Rowe, Kenmore, N. Y., assignor, by
mesne assignments‘, to Curtiss-Wright Corpo
ration, a corporation of New York
Application May 1'7, 1933, Serial No.‘ 671,470
17 Claims. (CL 244—75)
the annexed specification and claims, and in
This invention relates to aircraft, and particu
larly. to means for overcoming inadvertent ?utter considering the drawing, in which, similar num
bers designate similar parts, and in which:
in control surfaces thereof.
In the recent development of high speed air- ' Fig. 1 is a. side elevation of 'the empennage of
an airplane embodying the invention,
5 craft, a phenomenon commonly known as "?ut
Fig. 2 is an enlarged section on the line 2-2
ter” has sometimes appeared in the .control air- A
foils, such as ailerons‘, rudder and/or elevators. of Fig. '1, showing, in dotted linespcertain of the
elements in different positions of adjustment,
The effect of ?utter is to‘impose severe stresses
Fig. 3 is a cross section througha brace wire
on the aircraft structure with possible failure
13 resulting, and may also have the e?ect of im
pairing the controllability of the aircraft. The
basic reasons for the phenomenon have not been
having‘ an auxiliary airfoil attached thereto, and 10
Fig. 4 is a cross‘ section through a streamline
strut having an auxiliary airfoil attached‘ there
fully determined,>but certain curative practices
have been evolved which, when applied, appear
15' to assist in eliminating flutter.
Describing the invention in detail, In is an air
Some of these" plane fuselage having a vertical ?n H, and a_15
horizontal stabilizer l2. ‘At the trailing edge-of
practices include‘ lightening the affected parts,
the ?n II, a rudder I3 is pivoted, as at M, for
forward of its pivot axis, and eliminating slack‘ swinging movement subject to the action of con
ventional rudder controls 15. The line a,--a des
and lost motion in the airfoil hinges and actuat
locating the center of gravity of a control airfoil
ing members. _
" ignates the rudder. pivot axis, which may be rear-
The subject invention provides. fully automatic " ward of the leading edge l6 of the rudder, or
means for damping and eliminating control air
foil ?utter, and comprises brie?y an auxiliary air
‘ foil hinged to the control airfoil rearwardly. of
25 the control airfoil pivot. Thejauiliary airfoilis
arranged with its center of gravity forward of its
may be at any other convenient location with
respect ‘to said leading, edge. Suitable brackets
ii, attached to'the. ?n I I, carry the rudder pivots.
Toward the trailing edge I8 of the rudder l3, 25
a cutout I9 is made,’ and hinges 20 are arranged
on an axis b-b to carry'an'anxiliary airfoil 2i.
Said airfoil 2| ‘extends rearwardly from the hinge,
moments for the control airfoil in a manner to be axis 17-17, and is freely swingable to either side
of the plane of symmetry of the rudder l3. It‘will 30
30 more fully described hereinafter.
. A somewhat similar and related phenomenon be noted-‘that, since the bulk of the surface of the
to control surface ?utter is the vibration in ?ight airfoil 2! is rearward ofv the axis b--b, the center
of exposed brace wires and long exposed=~struts. of pressure of air acting thereon will likewise be
The invention also provides means for damping rearward of said‘ axis,‘ To place the center of
gravity of the structure of.‘ the airfoil ~2l forward,
Li vibration in such members’.
Objects of the invention are to provide means of said hinge axis b--b, an arm_ 22, carrying
for eliminating control airfoil ?utter; to provide a weight 23 at its forward wencLextends for;
a, freely swingable ‘auxiliary airfoil hinged to a, wardly-of the axis b-b, and is rigidly attached
to the airfoil 2|? Alternative means will be ap
control airfoil; to provide a hinged airfoil hav
49 ing its center of gravity forward of the hinge ‘parent to those‘skilled in the art for carrying 40
axis; to provide a hinged airfoil having the major the center of gravity of the airfoil 2|‘ forward'of
. _,
part of its air contacting surface rearward of the hinge axis b--b. " _
The operationfof the devicemay be more readily
its hinge axis; and to provide an airfoil.- which
- 'by its inertia, tends to damp ?uttering tendencies. understood by referring to Fig. 2. The position C
shows the rudder l3 and the auxiliary airfoil 2| 45
01 Related ,objects are to provide auxiliary airfoil‘s, '
hinge axis, and with its center of pressure rear
ward thereof, which, in action, providesdamping
either fixed to or hinged to other aircraft meni
bers which may be‘subject to vibration or ?utter,» ,
to damp and eliminate such vibration or ?utter.
In such auxiliary airfoils, the principles are iden- '
I 50 tical with the airfoils as applied to control sur-
faces; namely, the center of ‘gravity of the airfoil
is ahead of the member,- or ahead of the point of
attachment of‘ the, airfoil, ‘ while ' the center of
pressure is rearward thereof;
. 55 vFurther objects will be apparentv in reading
in alinement, which would be their normal posi
tion. ' Should the'rudder
to ?utter, that-is,
be moved by forces othenthan those imposed-by
the pilot of the'aircraft on‘the controlsrliitj
will movequickly to some displaced position such‘ 50
as D. When this occurs,v the‘ surface of the
auxiliaryairfoil 2! will tend to be displaced at a
greater angle‘than the rudder; due to the weight
of saidairfoil acting forward of“ the axis b—-b,
which weight, by inertia5 resists displacement.._f55'
Hence, the airfoil 2|, addressedbythe air stream,
exerts a steering effect on the rudderi I, tending
from the spirit or scope thereof. , I aim iii the ap
pendedolaims to cover all such‘modifications and
to move it back to the plane of symmetry or to -
position C. -As suchv movement occurs, the rud-l
"der It and airfoil 2| will assume a position such
-as E, wherein the rudder is moving'toward the
plane of symmetry, but the‘airfoil 2| has, by its
inertia, moved in oppodte angular sense. to the
rudder, since the center of gravity thereof is
forward of its hinge axis. Hence, the air stream
‘then acts on the opposite 'side of the airfoil 2|, ‘
counteracting in some degree the restoring tum
ing moment initiated in position D, thus damping
movement of both the rudder i3 and the airfoil
2|, preventing repetitious oscillation of either, and
gradually returning both, “their positions in the
aircraft plane of symme
Iclaimss'my invention:
1“. ,In aircraft ‘having a cont ml airfoil "movable
about a pivot,_an auxiliary airfoil freely movable
about a hinge carried-on said :control airfoil,
said auxiliary airfoil having its center of gravity
forward 0: its-hinge and its center'of pressure
rearward thereof.
. .
2. In aircraft‘ having a controlr airfoil con
trollably movable with respect thereto, an aux;
iliary airfoil hinged toward the rearward edge of
said control airfoil movable with and with respect
thereto, having its center of gravity forward of 15
said hinge and its center of pressure rearward of
The proportionate size, weight, center ,0: grav-I
3. In aircraft having a control airfoil subject
to controlled movement, means for overcoming
_uncon'trolled ?utter of said airfoil comprising a 20
statically unbalanced auxiliary airfoil hinged to
?utter oscillation. The above X ctional descrip
tion is predicated upon correct _roportions in the I said control airfoil‘jhaving its center of 'avity
device, which proportions may be evolved by cal¢. forward of said hinge and its center of pr ssure
rearward thereof. ,
, ..
culation and experiment. It will be readily ap
4. In aircraft,_a control airfoil pivoted thereto 25
preciated that the structure and functions above
ity location and center of pressure location of the
20 airfoil 2| will govern its effectiveness in damping
described may be applied with identical effect to
elevators, ailerons, brace'wires, struts or other
movable aircraft members. In Fig. 1 the elevator
25, carried by the stabilizer l2, for instance, may
so be ‘equipped with an auxiliary airfoil 2|’; an arm
22' and a weight 23', to act in-the same manner
as the similar elements 2|,'22 and 23.
and extending rearwardly from the pivot, an aux
iliary, airfoil hinged toward its forward edge to
said control airfoil, the hinge axis being spaced
rearwardly from said pivot, and an arm extend
ing from said auxiliary airfoil forward of said 30
hinge, the mass of said arm being of a magnitude
to-more thancounterbalance the weight of said .
auxiliary airfoil rearward of said hinge.
_The airfoil 2| as above described, may be either
freely swingable to ful?ll an anti-?utter function
only, or may be controllable. Fig. 2 shows, in.
dotted lines, one arrangement for controlling the
airfoil 2|, wherein ‘a horn 24, ?xed to the airfoil,
is connected by the rod 25 to a lever 26, movable
on the axis a--a.
_\ 5. .In aircraft, a vertical rudder pivoted there
to, and an auxiliary airfoil hinged to said rudder 35
rearwardly of said rudder pivot for free swing
ing with respect thereto, said airfoil having its
center‘ of gravity forward of said hinge and its
center of pressure rearward of said hinge.
lI'his lever may in turn be
6. In aircraft, an elevator pivoted-thereto and 40
"quarters, whereby the pilot may set the airfoil 2| . .an auxiliary airfoil hinged to said elevator rear-4
40 controlled by a rod 21 leading to the pilot's
wardly of said elevator ‘pivot for‘ free swinging‘
I at an angle with respect to the rudder l3 for
with respect thereto, said airfoil having its cen
ter of gravity forward of said, hinge, and
trimming yawing tendencies in the ?ight _of the‘
aircraft. _Whether controllable or freely swing
able, the airfoil 2| will have the desired effect center of p'ressure rearward of said hinge.- ‘
‘ 7. In aircraft having a member subject to both‘
When controllable, the
in controlling ?utter.
control elements, as 24, 25, 26 and 21 will have ' controlled _and- uncontrolled relative movement
su?lcient resilience to allow the airfoil 2| to move ’ in ?ight, an auxiliary airfoil for damping the un
controlled movement attachedto said member,
said airfoil having its center of pressure rear
Figs. 3“ and 4‘ show the anti-?utter or anti
vibration devices as they ‘may be applied to , ward of its point of attachment, and having 5-0
streamline brace ‘wires onstruts. In Fig. v3, a _means forward of said point of attachment ‘for
su?iciently to damp ?utter.
locating the 'center of - gravity of said airfoil for
wire 28 has attached theretoa small airfoil-2S
having a’ main v,portion 31 of light material ex
ward of said point of attachment.
8. In aircraft having a member subjectto both 55
tending principally rearwardly of the wire 28.
so that .its center of surface area is rearward
of the wire. A' nose ll of heavier material forms
controlled and uncontrolled relative movement in
?ight,‘ means for damping the. uncontrolled
the forward portion ofthe airfoil 20, whereby the
element. attached ~
center of gravity of the unit is thrown forward thereto intermediate the width of said‘ ele'ment,
said element having its aerodynamic center of
60 of the center of the wire 28. ‘If the wire starts to
move crosswise ofthe airstream, the nose 2| lags .pressure rearward of said point of attachment,
by inertia, tilting the airfoil 28 and twisting the . ‘and having. a mass forward, of said pointof at
wire 28 to steer the unit. to a neutral position. tachment greater than ‘the mass rearward
In Fig. 4, the element 28' may represent a strut
65 or the like which is relatively rigid and not sub
‘ 9.“In ircraft, aj movable element'in the slip
center of gravity theeof. forwardloi' said point 70
"ject to twist. Hera/the airfoil 29' is‘swiv’elled~ stream nd an auxiliary airfoil embracing said
on the Istrut as at 32L so thatr as the element 28' element having its aerodynamic center of pres
_moves crosswise, the airfoil.29' will turn about sure rearward of'its Point of‘; ' tiMTihmentv to said?
the swivel 32,- by the inertia of the nose it’, and element, and having’_means fo?e's‘tablishing the
steer the strut 2l'lback ‘to a neutral position. .
While I have described my invention in detail
in its present preferred embodiment, it will be ob
vious to those skilled _in the art, after understand
1 ing my invention, that various changes and mod
of attachment.
ffi_',_l ;_ '
I; f
10. In‘ aircraft, an .vauxiliary airfoil, 'and a
movable member in'th'e slipstream embraced by‘.
. andv attached tos'aid ‘airfoil,;‘ " di'airi’oil having
ifications may be‘made'therein without departing 1th center of pressure rearward'gofthe point of 75
' attachment and having. its center
of gravity for-" '
trolled movement, meana for preventing flutter
thereof, comprising an auxiliary airfoil carried
11. In aircraft having a member subject to . thereby and disposed in the airstream, said airfoil
' uncontrolled relative movement'in ?ight, an aux- -
iliary airfoil for damping said movement ‘con
being hinged to saidyelement and having its cen
ter- of gravity forward of the hinge line, and its
trolled in its own movanent only by its response . center of pressure rearward thereof. >
to air?ow and inertia, pivoted to swing freely on
15. In means for overcoming ?utter in an air
and vwith respect to said member, said airfoil craft element subject to controlled movement, an
having its ‘center of pressure rearward of said‘ auxiliary airfoil mounted for oscillation on said
pivot, and'having its center of gravity forward of
said pivot.
12. In an aircraft element exposed to the air
stream- and subject to movement aboutv an axis
element, said airfoil having its center of mass for
ward of the axis of oscillation, and having its
center of pressure rearward of said axis of oscilla
of oscillation, ?utter'prev'ention means compris-. ' 16. In aircraft, an airfoil subject to controlled
ing an ‘auxiliary control surface carried by said movement, an auxiliary anti-?utter airfoil hinged 15
element, said surface having its center of pres--' to said controlled airfoil, the center of gravity
'} sure rearward of the oscillation axis of said ele
of said auxiliary airfoil being forward of ' said
ment', and having its center of gravity forward-of
hinge and the center of pressure thereof bei
said oscillation axis.
rearward of said hinge.‘
13. In a ‘relatively long slender aircraft ele
~ ' ment exposed to the airstream, means for pre
venting inadvertent ?utter thereof, comprising
an auxiliary airfoil carried by said element, said
airfoil having its center of gravity forward of
25 the center of gravity of said element. and having
. its center of pressurerearward of the center of
gravity of said element.
17. In aircraft, a control airfoil pivoted there
to, and an auxiliary airfoil hinged to said control
airfoil rearwardly of said control airfoil pivot for
free swinging movement with respect to the con- -
trol airfoil, said auxiliary airfoil having its cen
ter of ‘gravity forward of said hinge and its cen 25
ter of pressure rearward of said hinge.
' ’ -
- . ‘is. In an aircraft element whim W 9°11"
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