Note: Descriptions are shown in the official language in which they were submitted.
--~ 2 ~2~
SELP-ADJUSTING SLIDE ASSEMBLY
FOR WEIGHT ON GEAR SWITCH
TECHNICAL FIELD
Thls lnventlon relates to alrcraft welght on gear
swltches and, in partlcular, to ~ self-ad~ustlng sllde
assembly for mountlng an alrcraft welght on gear swltch.
" ~'~';,'
~ .;
- 2~2~33~ ~
,
BACXGROUND OF l~IE INVENTION
Sophlstlcated alrcraft generally lnclude a welght
on gear swltch for actlvatlng and deactlvatlng varlous
alrcraft systems and fllght controls dependlng upon
whether the alrcraft ls airborne or fully supported by
the landlng gear on the ground. In some alrcraft, such
as hellcopters, the welght on gear swltch also provldes
an indlcatlon to the pllot that the alrcraft ls elther
alrborne or on the ground.
Aircraft welght on gear swltches, or squat
switches, are typlcally actuated by a maln landlng gear
strut when compressed to support the welght of the
alrcraft. On hellcopters wlth skid landlng gear
systems, paddles or slmllar devlces have been used to
actually contact the ground surface upon landlng of the
hellcopter. However, swltches deslgned to contact the
ground are generally unrellable because of collectlon of
dlrt and debris or damage from skld movement and ob~ects
on the ground. In addltlon, ground contact swltches can
glve erroneous lndlcatlons when the hellcopter ls
landlng on uneven terraln.
Other types of hellcopter welght on gear swltches
have been based on collectlve stlck posltlon or englne
torque. However, these types of swltches generally can
be overridden by the pllot so that they can lndlcate the
alrcraft ls ~lrborne when it ls actually on the ground.
Another type of welght on gear swltch for skld gear
helicopters ls mounted so as to detect deflectlon of a
cross tube of the skld landlng gear. Thls placement of
the welght on gear swltch overcomes many of the
dlsadvantages of the ground contact or collective stlck
~' posltlon swltches. However, swltches mounted to
lndlcate deflectlon of the skid gear cross tube requlre
perlodlc ad~ustment as a result of repeated cross tube
... ...... .
'~
', ,`~
.''i''"',~' .. .' ~,. ',' '` . : ' '` `
~: :
`~
~ 3 ~ 6 3 ~i~
deflection from normal landlngs and permanent
deformation from harder than normal landlngs. Wlthout
such periodlc ad~ustment, welght on gear swltches can
glve erroneous lndlcatlons that can affect fllght
safety.
Therefore, there ls a need for a mountlng assembly
for a hellcopter welght on gear swltch that is self-
ad~ust1ng both for normal landlng deflection of the skld
gear cross tube and for permanent deformation of the
cross tube resultlng from hard landlngs.
:
`' ;" ~
1~ . . . ` . :
$33~
SUMMARY OF THE INVENTION
The present lnventlon ls a self-ad~ustlng sllde
assembly for an alrcraft welght on gear swltch. A
preferred embodlment of the sllde assembly ls
partlcularly ~dapted for mounting a welght on gear
swltch to detect the osclllatory deflectlon of a skld
landlng gear cross tube on a hellcopter.
A mountlng bracket of the self-ad~ustlng sllde
assembly ls mounted to the underslde of the hellcopter
fuselage ln close proxlmity to the center of a cross
tube of the skld landlng gear. A back plate extends
vertlcally downward from the mountlng bracket. A palr
of vertlcal clamp plates are attached to the back plate
by fastenlng means so as to form a vertlcal channel
lS between the clamp plates and a vertlcal groove between
each of the clamp plates and the back plate. A sllde
member has a T-shaped flange along one edge thereof for
slldably mountlng ln the channel and grooves formed by
the back plate and the clamp plates. The fastenlng
means may be tlghtened or loosened to ad~ust the force
necessary to move the sllde member vertlcally ln the
channel ~nd grooves.
The sllde member has a generally C-shaped
conflguratlon wlth upper and lower arms. The sllde
member ls mounted so that the arms extend above and
below the cross tube of the hellcopter skld landlng
gear. Durlng take-off and landlng, the cross tube of
the landlng gear deflects a known dlstance ln the
vertlcal dlrectlon. Deflectlon of the cross tube causes
lt to contact a top bumper on the upper arm when the
hellcopter ls alrborne and to contact a bottom bumper on
the lower arm when the weight of the hellcopter ls on
the landlng gear. A mlcroswltch ls mounted on the iower
arm sc as to extend vertlcally ~ust above the bottom
'~'""" ' ~' '' '
;2~3r
bumper. When the hellcopter lands, the mlcroswltch ls
actlvated by the cross tube as lt deflects agalnst the
bottom bumper. The bottom bumper protects the
mlcroswltch from damage by llmitlng the extent of
s contact between the cross tube and the mlcroswltch. The
top and bottom bumpers of the sllde member are spaced
apart to accommodate the normal vertlcal osclllatory
deflectlon of the cross tube about a mean positlon
durlng take-off and landlng.
Although the mlcroswltch ls mounted on the slide
member to detect the normal range of cross tube
deflection, repeated landlngs or harder than normal
landlngs can cause the cross tube to be temporarlly or
permanently deflected from lts orlglnal mean posltlon
;~
lS wlth respect to the hellcopter. However, the sllde
-~
assembly of the present lnventlon automatlcally ad~usts
the posltlon of the mlcroswltch durlng each take-off and
;
landlng cycle of the hellcopter to correspond to any
change ln the mean posltlon of the cross tube. For
example, lf the cross tube ls permanently deflected
downward durlng a hard landlng, the cross tube contacts
the bottom bumper and moves the entlre sllde member
downward relatlve to the bracket attached to the
-~
fuselage of the hellcopter. Tnus, the mlcroswltch on
the lower arm ls moved downward an amount correspondln~
to the permanent deflectlon of the cross tube so that
the normal downward deflectlon of the cross tube upon
landlng contlnues to actuate the mlcroswltch.
6 2~633~
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understandlng of the present
lnventlon and for further advantages thereof, reference
ls made to the followlng Descrlption of the Preferred
s Embodlment taken in con~unctlon wlth the accompanylng
Drawlngs, ln whlch:
FIGURE 1 lllustrates the lnstallatlon of the
present inventlon on a hellcopter havlng a skld landlng
gear system; and
FIGURE 2 ls a perspectlve vlew of the self-
ad~ustlng sllde assembly of the present lnventlon.
''; ~
7 ~2~3~L
`
DESCRIPTION OF T}IE PREFERRED EMBODIMEN~
FIGURE 1 shows a self-ad~ustlng sllde assembly 10
of the present lnventlon mounted on the underslde of the
fuselage of a hellcopter 11. Hellcopter 11 ls equlpped
wlth a skld landlng gear assembly 12 lncludlng ~ cross
tube 14 attached to hellcopter 11 by mountlng polnts 13.
Sllde assembly 10 ls mounted ln close proxlmlty to the
center of the cross tube 14 between mountlng polnts 13
so that vertlcal osclllatory deflectlon of cross tube 14
about a mean posltlon actuates a weight on gear swltch
to lndlcate whether hellcopter 11 ls alrborne or on the
ground. Assembly 10 should preferzbly be mounted on
rear cross tube 14, as excesslve aft cycllc can transfer
vlrtually the entlre welght of the hellcopter from front
cross tube 14 to rear cross tube 14 when the hellcopter -
ls on the ground. A welght on gear swltch mounted to -~
front cross tube 14 ln thls sltuatlon would falsely -~-~
lndlcate that the hellcopter was alrborne. Thls
phenomenon, however, ls not normally exhlblted wlth rear
cross tube 14 when full forward cycllc is applled, thus
maklng the rear cross tube 14 the preferred posltlon for
attachment at assembly 10. Whlle two swltches can be
used, one on the front and one on the rear cross tube,
preferably only one at the rear cross tube ls used.
FIGURE 2 ls a perspectlve vlew of sllde assembly 1
removed from hellcopter 11. Sllde assembly 10 lncludes
a mountlng bracket 16 for mountlng sllde assembly lO to
the underside of hellcopter 11. A back plate 18 extends
vertlcally downward from mountlng bracket 16. Back
plate 18 may comprlse an extenslon of mountlng bracket
16 and/or a separate spacer plate 19 attached to
mountlng bracket 16. A palr of vertlcal clamp plates 20 --
are attached to back plate 18 by a plurallty of
fastenlng means 22, such as nuts, bolts, and washers.
8 ~ 3 ~ ~
Clamp plates 20 may be laminated or lnclude multlple
plates such as an lnner wear plate 20a and an outer
support plate 20b. Clamp plates 20 are attached to back
plate 18 so as to provlde a vertlcal channel 21 between
clamp plates 20 and a vertlcal groove 23 between each
clamp plate 20 and spacer plate 19.
In the preferred embodlment, mountlng bracket 16
and back plate 18 are constructed of metal spacer plate
19 and lnner wear plate 20a ls preferably constructed
from a self-lubricatlng plastlc such as Teflon or ~el-F.
Outer wear plate 20b ls preferably constructed of metal.
The use of self-lubrlcatlng plastlcs ~s useful for ease
of malntenance. It ls posslble to use metal ln place of
plastlc, however, use of metal would requlre
malntenance, lubrlcatlon and preferably a cover to
prevent contamlnatlon of the surfaces.
A generally C-shaped sllde member 24 has a T-shaped
flange 25 along lts vertlcal edge. T-shaped flange 25
ls adapted to be engaged between clamp plates 20 and
spacer plate 19 so that sllde member 24 extends through
vertlcal channel 21 and flange 25 slides ln grooves 23
between clamp plates 20 and spacer plate 19. Clamp
plate 20a and spacer plate 19 should be made of Teflon
or a simllar self-lubrlcatlng plastlc materlal havlng a
coefflclent of frlctlon that facllltates slldlng
movement of sllde member 24 ln grooves 23 between clamp
plates 20 and spacer plate 19. ~n order to prevent
corroslon, flange 25 should preferably be made of
stalnless steel. Other sultable materlals would lnclude
<30 Teflon coated or plastlc coated metal parts.
Sllde member 24 has a lower arm 26 that lncludes a
swltch mount 27 and a slot 28 for conflnlng a bottom
bumper 29. Sllde member 24 also has an upper arm 30
wlth a top bwmper 32. Top bumper 32 may comprlse, for
2 ~ 3 ~ `
~. ~
example, a section of shrlnk tublng formed about upper
arm 30.
Sllde member 24 ls mounted so that upper ~rm 30
extends above cross tube 14 and lower arm 26 extends
S below cross tube 14. Arms 26 and 30 are deslgned to
extend past the landlng edge of cross tube 14 so as to
prevent decoupllng from assembly 10 upon deflectlon of
the cross tube durlng a run on landlng. A horlzontal
sxtenslon of about 1/2 inch beyond the leading edge of
the cross tube, which is slzed to incur a vertlcal
deflectlon of about 0.5 lnches when welght of the
hellcopter ls added to the landlng gear, has been found -~
to be sufflclent for thls purpose ln the current
embodlment of assembly 10. The degree of extension of
arms 26 and 30 can be of any length sufflclent to
prevent decoupllng of the assembly when the cross tube
deflects. Preferably, the assembly 10 ls mounted such
that back plate 18 ls on the rear slde of the cross
tube.
Durlng take-off and landlng, cross tube 14 normally
deflects from a lower positlon agalnst bottom bumper 29
when the welght of hellcopter 11 ls fully on skld gear
12, to an upper posltlon agalnst top bumper 32 when
hellcopter 11 ls alrborne. A mlcroswltch 34 mounted on
swltch mount 27 extends vertlcally sllghtly above bottom
bumper 29 so that cross tube 14 actuates mlcroswltch 34
when hellcopter 11 ls fully on skld gear 12 and cross
tube 14 ls ln contact wlth bottom bumper 29. Bottom
bumper 29 protects mlcroswltch 14 from any hard contact
wlth cross tube 14. As wlll be appreclated, the bumpers
are spaced to accommodate the normal deflectlon of the
cross tube. The swltch mechanlsm should have a
sufflclent length of travel for actlvatlon to prevent
false slgnals from vlbratlons. Also preferable, the
p~. ,..... .. ... : - ........................... - . ~ : , .
,~. ~ : , ' , !.
2 ~ 3 ~ -
--~ 10
swltch is spaced apart from the cross tube when there ls
no welght on the gear. It has been found that a cross
tube, sized to deflect about 0.5 lnches ln the vertlcal
dlrectlon when the welght of the hellcopter ls added to
the landlng gear, can be usefully employed ln the
present lnventlon. A swltch havlng a travel of about
0.125 lnches or more has been found useful ln the
present lnvention.
After repeated landlngs or harder than normal
landlngs, the mean posltlon of the osclllatory
deflectlon of cross tube 14 may become temporarlly or
permanently dlsplaced from lts origlnal posltlon wlth
respect to mountlng bracket 16. In prlor art welght on
gear swltches, excessive deflectlon of cross tube 14
could cause erroneous fllght lndlcatlons affectlng
fllght safety unless the posltlon of the welght on gear
swltch was manually ad~usted.
Durlng normal take-offs and landings, cross tube 14
exhlbits osclllatory deflectlon between top bumper 32
and bottom bumper 29, and actuates mlcroswltch 34 when
ln contact wlth bottom bumper 29. Because sllde member
24 ls slldably mounted between spacer plate 19 and clamp
plates 20, any deflectlon of cross tube 14 beyond lts
normally establlshed llmlts causes sllde member 24 to
sllde so that top bumper 32 and bottom bumper 29 define
new llmlts for osclllatory deflectlon of cross tube 14.
For example, lf a harder than normal landlng causes
cross tube 14 to deflect, temporarlly or permanently,
further from the fuselage of hellcopter 11, cross tube
14 contacts bottom bumper 29 and forces sllde member 24
to sllde downward to the llmlt of the downward
deflectlon of cross tube 14. Because microswltch 34 ls -
mounted on lower arm 26, lts posltion ls moved downward
a dlstance correspondlng to the downward deflectlon of
;: :: ,: . . .
,~ ,~....
",, ' ~ 11 20~6~3~r
cross tube 14 agalnst bottom bumper 29. Llkewlse, any
upward deflection of cross tube 14 beyond lts normally
establlshed llmlt causes cross tube 14 to contact top
bumper 32 and move sllde member 24 upward. Thus,
mlcroswltch 34 always malntalns approxlmately the same
relatlve posltlon with respect to the mean posltlon of
the osclllatory deflectlon of cross tube 14 regardless
of any permanent deformatlon of cross tube 14. -
The pressure between plates 20a and 19 and flange
25 ls regulated by the torque applled to bolts 22. In
order to properly compensate for osclllatory deflection
of cross tube 14, thls pressure should be such that
approxlmately 35 pounds of force ls requlred to move
sllde member 24 vertlcally up or down through vertlcal
channel 21. Greater or lesser torque can be applled to
the bolts to ad~ust the force requlred to move the slide
member. The force selected before movement of the sllde
member ls allowed can vary and be ad~usted dependlng
upon the degree of sensltlvlty deslred, the slze of the
hellcopter and the deflectlon characterlstlcs of the
cross tube.
Although the present lnventlon has been descrlbed
wlth respect to a speclflc embodlment partlcularly
adapted for skld gear hellcopters, varlous changes and
modlflcatlons may be suggested to one skllled ln the art
to adapt the present lnventlon to other landlng gear
systems, for example, and lt ls lntended that the
present lnventlon encompass such changes and
modlflcatlons as fall wlthln the scope of the appended
clalms.
,,~',` `~` ' . ' ` `: ' . '
h ~
