CA1094526A - Aircraft surface structure - Google Patents
Aircraft surface structureInfo
- Publication number
- CA1094526A CA1094526A CA293,260A CA293260A CA1094526A CA 1094526 A CA1094526 A CA 1094526A CA 293260 A CA293260 A CA 293260A CA 1094526 A CA1094526 A CA 1094526A
- Authority
- CA
- Canada
- Prior art keywords
- alloy
- surface region
- super
- weight
- plastic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C1/00—Fuselages; Constructional features common to fuselages, wings, stabilising surfaces or the like
- B64C1/38—Constructions adapted to reduce effects of aerodynamic or other external heating
Abstract
ABSTRACT OF DISCLOSURE
A method of protecting a surface region of an aircraft against erosion by rain, airborne sand, hail and the like, inc-ludes starting with a sheet or sheets of a super-plastic alloy.
The sheets of alloy are engaged with the surface region to be protected, and are then shaped, while at a temperature such that super-plastic properties of the alloy are exhibited, to follow the surface contours of the surface region to be protected.
Thereafter the shaped sheet or sheets of alloy are secured in position on the surface region. The invention also resides in a surface region of an aircraft protected by a layer of super-plastic alloy, and also in a protection member shaped to fit a particular aircraft surface region and formed from the super-plastic alloy.
A method of protecting a surface region of an aircraft against erosion by rain, airborne sand, hail and the like, inc-ludes starting with a sheet or sheets of a super-plastic alloy.
The sheets of alloy are engaged with the surface region to be protected, and are then shaped, while at a temperature such that super-plastic properties of the alloy are exhibited, to follow the surface contours of the surface region to be protected.
Thereafter the shaped sheet or sheets of alloy are secured in position on the surface region. The invention also resides in a surface region of an aircraft protected by a layer of super-plastic alloy, and also in a protection member shaped to fit a particular aircraft surface region and formed from the super-plastic alloy.
Description
10~4S~6 Thi~ rent;Lon re:Lates to a meth~d of pro~ctiJIg pred~
erlllinec~ sllrface regions of an aircraft and to an aircraft s~rf-lce reg:ion incorpo~atig sllch protection.
-Lt i.9 k210Wn that certain surface regions of an aircraft~
for example the leading edgeR of the wing~, tha englne air intake~, the leading ~dge~ o~ the tail structure, helicopter rotor blade~
airscre~3, engine compressor blades, and guide vanes, are subjec-.
in use to surface erosion and to impact dam~ge5 by rain, airborn~
~and, and ice ~nd the like. These ~urface r~.gionq may incorporate electrical heating devLces to facilitate de-icing during ~light~
and of course the preservation of the mechanic~l, and where app~
ropriato electrical integrity of these regiorls i4 of great imp~
ortance. It is known to protect ouch ~urface r0gions a~ainst ~i erosion and impact damage by providin~ the surface rsgion witha synthetic resin covering, for ex~mple a covering of a polyura~
th,ne or neoprene material. Such co~erings ar0 quit2ble for 3 relati~ely low speed app`lication~, for example up to an ~pprox-imate maximum of 450 miles per hour~ this fig~lre repres6nti3lg ~he v~locity component normal to the ~urface in que~tionO In order to provide surface erosion protection for higher speed aircraft~
for e~ample aircraft c~pable of entering supersQnic speed rang~s, it has in the past been proposed to provide protective layers~
o~ stainles3 ~teel or nickol. The synthetic resin group of materials provjde protection by virtue o~ their resili~nce ~nd toughness~ l~hile t'lemet~llic coatig3 ment~oned a~ford protectiou by virtue o~ their hardness. The syrrthetic resi~ Inaterials ~u~fer from t~e ~isad~rantage that i-lleir usef`lllne~ is limited .
erlllinec~ sllrface regions of an aircraft and to an aircraft s~rf-lce reg:ion incorpo~atig sllch protection.
-Lt i.9 k210Wn that certain surface regions of an aircraft~
for example the leading edgeR of the wing~, tha englne air intake~, the leading ~dge~ o~ the tail structure, helicopter rotor blade~
airscre~3, engine compressor blades, and guide vanes, are subjec-.
in use to surface erosion and to impact dam~ge5 by rain, airborn~
~and, and ice ~nd the like. These ~urface r~.gionq may incorporate electrical heating devLces to facilitate de-icing during ~light~
and of course the preservation of the mechanic~l, and where app~
ropriato electrical integrity of these regiorls i4 of great imp~
ortance. It is known to protect ouch ~urface r0gions a~ainst ~i erosion and impact damage by providin~ the surface rsgion witha synthetic resin covering, for ex~mple a covering of a polyura~
th,ne or neoprene material. Such co~erings ar0 quit2ble for 3 relati~ely low speed app`lication~, for example up to an ~pprox-imate maximum of 450 miles per hour~ this fig~lre repres6nti3lg ~he v~locity component normal to the ~urface in que~tionO In order to provide surface erosion protection for higher speed aircraft~
for e~ample aircraft c~pable of entering supersQnic speed rang~s, it has in the past been proposed to provide protective layers~
o~ stainles3 ~teel or nickol. The synthetic resin group of materials provjde protection by virtue o~ their resili~nce ~nd toughness~ l~hile t'lemet~llic coatig3 ment~oned a~ford protectiou by virtue o~ their hardness. The syrrthetic resi~ Inaterials ~u~fer from t~e ~isad~rantage that i-lleir usef`lllne~ is limited .
-2- ~ ~
s lO9'1S26 ~o rclatively low sp~ )p]i~ltions, whi]e ~le prev;ously-ploposed layers of llicliel or stainlcss steel, while bc;ng suit-a})le for a w;~e specd r~nge, are both extremely difficult and e~t)^eille]y expensive to produce. ~loreover, even thougll the pro-~-ective metallic ]ayers are extreme]y thin, it is extremely difficult al~d expens;ve to rorm them accurately to the complex surface shapes involved.
It is an object of the present invention to provide a method of pro~cecting surface regions of an aircraft, and an air-craft surface region so protected, in a simple and convenient r,lanner .
A metllod of protecting a surface region of an aircraftin accordance with the invention, includes starting with a sneet or sheecs of a super-plastic alloy engaging the sheet or sheets of super-plastic alloy, with the surface region to be protected, shaping the sheet or sheets of ~uper-plastic alloy at a tempera-ture such that the super plastic properties of the alloy are exhibited to follow the surface contours of the surface region to be protected, and securing the protective layer of super-plastic alloy so formed to said surface region~
In this specification, by the term super-plastic alloy, the applicants mean a super-plastic metal alloy.
Desirably the formed layer is secured to said surface reyion by means of an acihesive.
Conveniently the adhesive is applied to the surface region to be protected and/or the sheet or sheets of alloy prior to the shaping of the sheet or sheets.
1094SZ~; -Convellientl~- the ~31leet or ~h~et~ are preform~-l to th~
general .shap~ of the surface region ~nd are finally sh~ped in situ so as to conform to the s~rface contours p~cul-iar tG the actual surf~ce region~
The invention further resides in an aircraft ~urface regicr having seGUred thereto a protectivs laye~ of a super-plastic alloy.
In one aspect of the inventior., the aircraft surface reg-Gn incorporates heat~r structure and the protective layer of .5uper-, plastic alloy overlie~ the hoater structure.
s lO9'1S26 ~o rclatively low sp~ )p]i~ltions, whi]e ~le prev;ously-ploposed layers of llicliel or stainlcss steel, while bc;ng suit-a})le for a w;~e specd r~nge, are both extremely difficult and e~t)^eille]y expensive to produce. ~loreover, even thougll the pro-~-ective metallic ]ayers are extreme]y thin, it is extremely difficult al~d expens;ve to rorm them accurately to the complex surface shapes involved.
It is an object of the present invention to provide a method of pro~cecting surface regions of an aircraft, and an air-craft surface region so protected, in a simple and convenient r,lanner .
A metllod of protecting a surface region of an aircraftin accordance with the invention, includes starting with a sneet or sheecs of a super-plastic alloy engaging the sheet or sheets of super-plastic alloy, with the surface region to be protected, shaping the sheet or sheets of ~uper-plastic alloy at a tempera-ture such that the super plastic properties of the alloy are exhibited to follow the surface contours of the surface region to be protected, and securing the protective layer of super-plastic alloy so formed to said surface region~
In this specification, by the term super-plastic alloy, the applicants mean a super-plastic metal alloy.
Desirably the formed layer is secured to said surface reyion by means of an acihesive.
Conveniently the adhesive is applied to the surface region to be protected and/or the sheet or sheets of alloy prior to the shaping of the sheet or sheets.
1094SZ~; -Convellientl~- the ~31leet or ~h~et~ are preform~-l to th~
general .shap~ of the surface region ~nd are finally sh~ped in situ so as to conform to the s~rface contours p~cul-iar tG the actual surf~ce region~
The invention further resides in an aircraft ~urface regicr having seGUred thereto a protectivs laye~ of a super-plastic alloy.
In one aspect of the inventior., the aircraft surface reg-Gn incorporates heat~r structure and the protective layer of .5uper-, plastic alloy overlie~ the hoater structure.
3 In a further aspect of the invention the aircraft ~urface region incorporates ~trengthening fibre3 in its con~truction ` for example carbon filaments.
:~ In a furth~r aspectt the invention re~ides .in a protective shoe of a s~per~pla~tic alloy which is shaped 'o fit onto a .' predetermined aircraft surface region, said shoe being intended finally to be shaped in 9itU 90 as completely to follow the surface contours pecu~ar to the surf2ce region for ~hich it defines the protecti~e layer.
Conveniently the prefoxmed shoe i~lcorporate~ a heater structure 50 that the p~otective shoe and the he~ter structurs can be applied to the prede~rmined surface region in the ;
same operation.
:~ In a furth~r aspectt the invention re~ides .in a protective shoe of a s~per~pla~tic alloy which is shaped 'o fit onto a .' predetermined aircraft surface region, said shoe being intended finally to be shaped in 9itU 90 as completely to follow the surface contours pecu~ar to the surf2ce region for ~hich it defines the protecti~e layer.
Conveniently the prefoxmed shoe i~lcorporate~ a heater structure 50 that the p~otective shoe and the he~ter structurs can be applied to the prede~rmined surface region in the ;
same operation.
-4-10~ ~52~
Preferal-ly the alloy from which ih~ prot0ctive Layer i~
formed .i9 that kno~.~ as:
~ 'SP~ alloy" rnanufacturcd by the Imperial S~lting Comp~ny Lim.ited;
or is a two~pha~e aAuatornary alloy having a fine grain micro-structure stable at t,he te~perature of a super~pla~tic deformation consist.ill~ of zinc within thc range 70-~2/-' by weight and aluminium 30-18~ by wei~ht to which is added up to 0025,~o by - weight of magnesium and up to 2~ by woigh.t of one of the elerllents copper~ nickel and silver.
In the accompanying drawings 9 ~ igura t i9 a cross-~ectional r~pre3ent~tio~ of p~rt of an aircraft wing in accordanco with one eæample of th~ pr~ent ' invention~
:. ~igure 2 i9 a ~iew similar to ~lgure 1 of a modificationt ; and Figure 3 i~ a diagrammatic repre~entation o~ an aircraft.
i, .
Referring^ to thc drawing~ the wing includes an out~r skin 11 which defil~es the airfoil shape of the ~ring. The de~irabi.~it~
of protecting wing surfaces and other surface regions of the airfra~le again~t erosion and impact damage by rain~ and air-borne ~and and ice~ is well known. For example~ the leading e~ge surface~ of wlng~, tail structure~ and erlgine air i~ntake~
g~i~ vane~ and compressor blade~ and the leaaing edges of h~licopter rotor blades are su~ceptible to erosion and i~act dam~ge by ~a.in9 and airborne ice and ~nd, and thAus it ~
~ S ~
.
109452~
desirable to take steps to preserve the mechanical integrity of these re~ions, and also, of course, their electrical inte-grity in the event that they are provided with surface heaters for de-icing. Moreover where the component, for example a helicopter rotor blade, is formed from a material reinforced with fibres, i.e. carbon filaments, then clearly their integrity must also be protected. Thus in accordance with the present invention such surface regions are provided with an outer protective layer, the layer 12 in the drawing, formed from a sheet or sheets of super-plastic alloy having the super--plastic properties found in many binary zinc/aluminium alloys but not having their susceptibility of moisture attack. This reduction is susceptibility to moisture attack is of course important where protection against rain erosion is one of the requirements.
Tests made on aircraft parts filled with surface protection layers of the super-plastic alloy as described hereinafter show a good resistance to erosion under conditions of impact by rain, hail and sand.
A further benefit of using such super-plastic alloys to produce the protective outer layer is that as a result of the super-plastic properties sheets of alloy can be worked easily to follow accurately the surface contours peculiar to the actual airfoil or other surface region of the airframe on which the sheet or sheets are secured.
The sheet or sheets of super-plastic alloy are - relatively thin, of the order of 0.010 - 0.030 inches, the thickness chosen being consistent with need for the layer to be thick enough to prevent the impact shock of rain, ice and said from damaging -~O~`~S~6 the adlle~ . bo~ bet~een t:lla la~-er ~nd the surface being protected ~where all adhes:ive is u~ed) but thin anougll to Iceep the weight of the layer within acceptable limitsO
In o~er to apply such a protective layer t2 to a predet~
errnincd ~urface re~ion 11 of the airframe ~e~er~l alternative procedures are po~sible, for e~ample; ~he airframe component is detached and the predQterrnined surface region and/or,sheet or sheets of the ~uper plastic ~lloy are coated with an expoxy resin adhesi~e 13. The sh00t or sheet~ of alloy are the~ pressed ontv the predeter~ined surface region ~o that they generally f~low the sh~ptng thereof. Thereafter9 the components tog0ther with the sheet or sheets of alloy are rai~ed to the temperature of superpla~tlc defor~nation of the alloy at which ~emperature t'ne super plastic properties ~ the alloy are e~hibited, i~ an ove~
and the sheet or sheets of ~lloy are then shaped to inti7nately follow the predetermin~ surface regi.Gn, using the surface region itself as the former. Tho shaping ~orce is applted to the sheet or 3heet~ of alloy by engaging with the outer surface o~ the ~heet or sheets one or more air bag~, and thGn ir.flatin~
the air b~s to apply pressure to the sheet or shsets 90 as to ~chie~e a u~iform fi~al t~}ickness o~ adhe~i~e over the whols o`
the sheet or sheets. Alternati~rely the airfran~e compo~e~t carrying the ~heet or ~heet~ raised to the temperature of s~ita'ote plas~c de.ormatio~ can be placed in an impervious flexible baæ
~hlcb i5 then e~acuated 50 that external air pres~ure pres~es the ~heet or ~heet~ o, alloy to ~ollo~ intimately the .~.~hapir~
o~ the predetermine~d sllrface re~ion of the air~rams componellt.
_ 7 ~-:10~526 ~ ere it is necessar~r to restx:;ct the temperature to which the aircraft surf~ce reglon i~ heat0dr the sheet or sheets of super~plastic al].oy can be heated~ separat~ from the surface region9 to a suital)le te~perature in exces.q of the ideal forming temperat~r~ and Call then raidly be applied to and shap~d on tne cold surf~ce region. As a further pracaution.a heat in3ulating layer can be introduced between the hot ~heet or sheets and the surfa~0 region9 the insulati.~g layer being-in place of and of a thickneYs equal to, the adhesiv0 layer. The sheet or sheets ~r0 then shaped to the Aurface region, th~ sheet or sheets t~en being remo~ed to permit the insulatine~ layer to be replaced by a layer of adhesi~et ~ol~owing which tha sheet or sh~et~ will be replaced so as to be adhesively bonded to the ~urface region. As is me~-tionèd later, the aricraft region m~y require to be provided with a heat~r for use in aircraft de~icing. The heater layer may act a~ a heat insulating layer during sh~ping of the sheet or sheets of super-plastic alloy9 but of course in this situation the insul.atln.g layer defined by the heat~r will be left in situ and the sheet or ~heets will be adhesively bonded in positio~
co~ering the heater layer. As a still further ~lternative the aircraft surface regioll can temp.orarily be pro~ided with a cooling ar~angement to prevent ov~rh~a$ing of the surface or sheets region, during fitting of the sheet/o~ super~plastic alloy.
~, , ` As a furth~r alternative where a series of thaoretically j identical qurraces are to b2 protected, for example tha leading ; èdg6s of the wings of a flight cf identical air~raft then a pl~r~lity Gf protecti~e 3hoes each formed from a sheet or ~heets of 3uper-pla~tic al.Loy cnn be prGduced using a for!ner which is .
~ 8 --- 10~S26 idcnt:ical in sh.-lpe to the tllooretj.cal leading edge sh~pe of the aircraft of the fl:~gllt. It will be recofj^nised however that eac}l aircraft irl the flig~t will be slightly different from tne other~ since it i.f3 individually constrllctecl and so although eaol leadirlg edgs has tha same theoretical ~hape lt will ,n fact havG
surff~tce colltour3, minor a~perities and the like ~hich do not m~teria].ly affect it.s airfoil performarce, peculiar to itqelf~
Thus each protective shos will fit anyone oi` the leading ~dges of the aircraft of the flight but none wi.ll follow accurat~ly the peculi.ar surface contours. It is vital that the protcctive layer does follo~ the contours of t~ surface it is to pro~.ect in order ~hat t.he layer of adhesive securing the layer to the surff~ce ~s of even thickness and so exhibits conf3tanft ~dhesive properties over the whole area, it being recognised that for optimum adhesiva bond strength, many adhesive must be present in a lay-er of predetermined thicknes3 accurate to 0.1 Mm, Additionally failure of the layer to follow local peculiarities in the surface could result in a void between the layer and the surface which would be an inherent weakness in the co~posite structure. Such in~erent weakness would rapidly give rise tG
failure of the protective layer, under the extremely hig~ impact forces of even sMall particles at sonic velocitiesO It is kno~.in that such a weakness would give rise to failure of the previously known nichel or stainless steel protective layers under the same operating condltions. Al.so, wherc heater layers are incorporete~
then suoh voids would retract ~rofn lheir performance an~ m`'ght give rise to fa_lure due to overheating - 9 ~
. , ", ~ ~ . ~ , . . .
109~526 Since the pro-tective layer is th.n7 it is ~ependent for its mechanical. :integrity on the adhesive boIld and thus protec~ e laycr t7~US t conform accurately to the surface to be protected to ensure optimuln adhesive bond stren~th. I~lUS al.though a ~tc,ck of preforl,led identical shoes can be retained, in many cases each shoe muC-it be subject to final shaping operatior in situ on th3 actual surface to be protected. It will be understood th~t when using a preformed shoe the adhesive can be applied to the surface and/ol~ the shoe. The final shaping operation of the shoe ~ill be perf`ormed at the temperature of plastic de~formation of the a and may involve either of the techniques described above. I~
will be understood that the intimate cnrrelation in sh~pe can be achie~ed with relative ease by virtue of the super-plasticity.
Where the shaping operation is parformed ~ith the adhesive in situ-then it i~ of course a requirement of the adh,sive that it has a sufficien.tly long curing time to permit the alloy and component to be raised to the correct temperature~ and tc permi.t the sheet or sheets of alloy to be for~cd to the correct shape before the adhesive cures to a point at which relative move~ent between the sheet and the aircraft component is prevented~ In the event that a suitable adhesive is not available then it will be understood that the sheet or shoe of alloy could be finally shaped on thc actual surface but without adhesive present, the sheet or shoe then bein~ rernoved to permit application of the adhe,ive in temperature co~lditions s~iited to the adhesivs and t~e sheet er shoe then being ~rep~acsc so as to be secured by the adhe-sive. In such a te,chnique ~ spacar repr¢sentin~ the adhesive layar ma~- be interposad betwean the alloy a~d th~ sur~
.. ... ~................................................. . . ..
10~526 face duri~ i~inal sln~Li3-g of ~,he alloy so as to eJl.'.UJ:e eVCntl~al confoLinity be~weell ~he alloy and the surface whcn the spaccr is replaced by the aclhesive.
Some airfr~ime surface regions inCOLpOrate heater struc-tures 14 for de--iciny t]le surfaces in use. It is of course irnpor-tant to preserve the electrica] integrity as well as the mechani-cal inteyrity of such surface regions and thus such surface regions can be protected by sheets or shoes of super-plastic alloy as described above. It is envisaged -that in some instanccs, for example he]icopte ~-otor blades, it may be desirable ~o incorporate a heater into the protective alloy shoe prior to the application of the shoe to the surface to be protected. In such cases the alloy shoe may be preformed to the general surface shape and may then have a heater struc-ture 14 bonded on to its aircraft surface engaging face prior to fitting the shoe to the surface. It will of course be neces-- sary for the heater structure to be sufficiently flexible to conform to the surface contours of the airframe surface during the final shaping operation to ensure an even, void free thick-ness of adhesive. Various epoxy resin adhesives can be used and also phenolic resin adhesives and acrylic resin adhesives can be used if desired. I~here complex surface shapes are involved the heater structure 14 rnay be fitted to the surface prior to the - application of the sheets of alloy. In such cases the assembly of the sheets of alloy to the aircraft surface will be as des-cribed previously.
The adhesives used may obviously be painted or sprayed in liquid form or may be applied in the form of a paste or a prepared film.
109 ~5Z6 A su~t,able supor~pl~stic a110y is "SPZ all~" manufac~tl~ed by the Imp~rial Smelting Company Limited. The e~act form1~1~t~on of this alloy is not known to us. Ho~evars it io belia~e~ that the alloy is definable as "two-phase quzJcernary alloy havi~3:
a fine grain micro3tructure stabl0 at t;he temp~ature of 5upe~
plastic deformation9 consisting of ~illC within the range 70~,h by weight and aluminiurn 30~1 8~o by weight to which i~ added up to 0. 25~/o by weight of m~gnesium and up to 2.000,b by weight of one of the elements copper, nickel and silver~" and that many alloys within this definition may ~e suitable.
Reference is made herein to "the temperature of super-plastic deformation". It is to be understood that thi~ t~mp-erature is i~ practic~ a rang~ of tomperatures althou~h a particular te-nperature within the range may prove preferable in practice. ~or e~ample super plastic deformation of` a suitabl6 alloy can take place between approximately 150 C and 260 C but it i8 desirabLe in some applications in order to match the qual-i$ies o~ the adhesive used, the nature of the airframe regisn, and/or the degree o~ forming requirsd~ to perform the final shaping necessitating super-plastic deformation at the minim~lrn temperature at which pcrmanent de~ormation of the layer of` alloy can be en~ured. It will be u~derstood that the protecti-~e layer may be applied to the a~rcraft component wl1ich has the surface to be protected either while the component is on the aircraft or where po~sible while 1;he component i9 detached from tne aircraft.
~ 12 _ las~sz6 It ~ e recogni.sec~ at the ~hapin~ of` the protGctive layer t;o accuratoly conform to the contours peculiar to the act~ ur~ace to be protect;ed i.s a desideratu!n which is virtu~.lly in~po.~-~i b].e to achi~ve in practice u~inD the previou~ly known non-~uper-plas l;ic metal protective member
Preferal-ly the alloy from which ih~ prot0ctive Layer i~
formed .i9 that kno~.~ as:
~ 'SP~ alloy" rnanufacturcd by the Imperial S~lting Comp~ny Lim.ited;
or is a two~pha~e aAuatornary alloy having a fine grain micro-structure stable at t,he te~perature of a super~pla~tic deformation consist.ill~ of zinc within thc range 70-~2/-' by weight and aluminium 30-18~ by wei~ht to which is added up to 0025,~o by - weight of magnesium and up to 2~ by woigh.t of one of the elerllents copper~ nickel and silver.
In the accompanying drawings 9 ~ igura t i9 a cross-~ectional r~pre3ent~tio~ of p~rt of an aircraft wing in accordanco with one eæample of th~ pr~ent ' invention~
:. ~igure 2 i9 a ~iew similar to ~lgure 1 of a modificationt ; and Figure 3 i~ a diagrammatic repre~entation o~ an aircraft.
i, .
Referring^ to thc drawing~ the wing includes an out~r skin 11 which defil~es the airfoil shape of the ~ring. The de~irabi.~it~
of protecting wing surfaces and other surface regions of the airfra~le again~t erosion and impact damage by rain~ and air-borne ~and and ice~ is well known. For example~ the leading e~ge surface~ of wlng~, tail structure~ and erlgine air i~ntake~
g~i~ vane~ and compressor blade~ and the leaaing edges of h~licopter rotor blades are su~ceptible to erosion and i~act dam~ge by ~a.in9 and airborne ice and ~nd, and thAus it ~
~ S ~
.
109452~
desirable to take steps to preserve the mechanical integrity of these re~ions, and also, of course, their electrical inte-grity in the event that they are provided with surface heaters for de-icing. Moreover where the component, for example a helicopter rotor blade, is formed from a material reinforced with fibres, i.e. carbon filaments, then clearly their integrity must also be protected. Thus in accordance with the present invention such surface regions are provided with an outer protective layer, the layer 12 in the drawing, formed from a sheet or sheets of super-plastic alloy having the super--plastic properties found in many binary zinc/aluminium alloys but not having their susceptibility of moisture attack. This reduction is susceptibility to moisture attack is of course important where protection against rain erosion is one of the requirements.
Tests made on aircraft parts filled with surface protection layers of the super-plastic alloy as described hereinafter show a good resistance to erosion under conditions of impact by rain, hail and sand.
A further benefit of using such super-plastic alloys to produce the protective outer layer is that as a result of the super-plastic properties sheets of alloy can be worked easily to follow accurately the surface contours peculiar to the actual airfoil or other surface region of the airframe on which the sheet or sheets are secured.
The sheet or sheets of super-plastic alloy are - relatively thin, of the order of 0.010 - 0.030 inches, the thickness chosen being consistent with need for the layer to be thick enough to prevent the impact shock of rain, ice and said from damaging -~O~`~S~6 the adlle~ . bo~ bet~een t:lla la~-er ~nd the surface being protected ~where all adhes:ive is u~ed) but thin anougll to Iceep the weight of the layer within acceptable limitsO
In o~er to apply such a protective layer t2 to a predet~
errnincd ~urface re~ion 11 of the airframe ~e~er~l alternative procedures are po~sible, for e~ample; ~he airframe component is detached and the predQterrnined surface region and/or,sheet or sheets of the ~uper plastic ~lloy are coated with an expoxy resin adhesi~e 13. The sh00t or sheet~ of alloy are the~ pressed ontv the predeter~ined surface region ~o that they generally f~low the sh~ptng thereof. Thereafter9 the components tog0ther with the sheet or sheets of alloy are rai~ed to the temperature of superpla~tlc defor~nation of the alloy at which ~emperature t'ne super plastic properties ~ the alloy are e~hibited, i~ an ove~
and the sheet or sheets of ~lloy are then shaped to inti7nately follow the predetermin~ surface regi.Gn, using the surface region itself as the former. Tho shaping ~orce is applted to the sheet or 3heet~ of alloy by engaging with the outer surface o~ the ~heet or sheets one or more air bag~, and thGn ir.flatin~
the air b~s to apply pressure to the sheet or shsets 90 as to ~chie~e a u~iform fi~al t~}ickness o~ adhe~i~e over the whols o`
the sheet or sheets. Alternati~rely the airfran~e compo~e~t carrying the ~heet or ~heet~ raised to the temperature of s~ita'ote plas~c de.ormatio~ can be placed in an impervious flexible baæ
~hlcb i5 then e~acuated 50 that external air pres~ure pres~es the ~heet or ~heet~ o, alloy to ~ollo~ intimately the .~.~hapir~
o~ the predetermine~d sllrface re~ion of the air~rams componellt.
_ 7 ~-:10~526 ~ ere it is necessar~r to restx:;ct the temperature to which the aircraft surf~ce reglon i~ heat0dr the sheet or sheets of super~plastic al].oy can be heated~ separat~ from the surface region9 to a suital)le te~perature in exces.q of the ideal forming temperat~r~ and Call then raidly be applied to and shap~d on tne cold surf~ce region. As a further pracaution.a heat in3ulating layer can be introduced between the hot ~heet or sheets and the surfa~0 region9 the insulati.~g layer being-in place of and of a thickneYs equal to, the adhesiv0 layer. The sheet or sheets ~r0 then shaped to the Aurface region, th~ sheet or sheets t~en being remo~ed to permit the insulatine~ layer to be replaced by a layer of adhesi~et ~ol~owing which tha sheet or sh~et~ will be replaced so as to be adhesively bonded to the ~urface region. As is me~-tionèd later, the aricraft region m~y require to be provided with a heat~r for use in aircraft de~icing. The heater layer may act a~ a heat insulating layer during sh~ping of the sheet or sheets of super-plastic alloy9 but of course in this situation the insul.atln.g layer defined by the heat~r will be left in situ and the sheet or ~heets will be adhesively bonded in positio~
co~ering the heater layer. As a still further ~lternative the aircraft surface regioll can temp.orarily be pro~ided with a cooling ar~angement to prevent ov~rh~a$ing of the surface or sheets region, during fitting of the sheet/o~ super~plastic alloy.
~, , ` As a furth~r alternative where a series of thaoretically j identical qurraces are to b2 protected, for example tha leading ; èdg6s of the wings of a flight cf identical air~raft then a pl~r~lity Gf protecti~e 3hoes each formed from a sheet or ~heets of 3uper-pla~tic al.Loy cnn be prGduced using a for!ner which is .
~ 8 --- 10~S26 idcnt:ical in sh.-lpe to the tllooretj.cal leading edge sh~pe of the aircraft of the fl:~gllt. It will be recofj^nised however that eac}l aircraft irl the flig~t will be slightly different from tne other~ since it i.f3 individually constrllctecl and so although eaol leadirlg edgs has tha same theoretical ~hape lt will ,n fact havG
surff~tce colltour3, minor a~perities and the like ~hich do not m~teria].ly affect it.s airfoil performarce, peculiar to itqelf~
Thus each protective shos will fit anyone oi` the leading ~dges of the aircraft of the flight but none wi.ll follow accurat~ly the peculi.ar surface contours. It is vital that the protcctive layer does follo~ the contours of t~ surface it is to pro~.ect in order ~hat t.he layer of adhesive securing the layer to the surff~ce ~s of even thickness and so exhibits conf3tanft ~dhesive properties over the whole area, it being recognised that for optimum adhesiva bond strength, many adhesive must be present in a lay-er of predetermined thicknes3 accurate to 0.1 Mm, Additionally failure of the layer to follow local peculiarities in the surface could result in a void between the layer and the surface which would be an inherent weakness in the co~posite structure. Such in~erent weakness would rapidly give rise tG
failure of the protective layer, under the extremely hig~ impact forces of even sMall particles at sonic velocitiesO It is kno~.in that such a weakness would give rise to failure of the previously known nichel or stainless steel protective layers under the same operating condltions. Al.so, wherc heater layers are incorporete~
then suoh voids would retract ~rofn lheir performance an~ m`'ght give rise to fa_lure due to overheating - 9 ~
. , ", ~ ~ . ~ , . . .
109~526 Since the pro-tective layer is th.n7 it is ~ependent for its mechanical. :integrity on the adhesive boIld and thus protec~ e laycr t7~US t conform accurately to the surface to be protected to ensure optimuln adhesive bond stren~th. I~lUS al.though a ~tc,ck of preforl,led identical shoes can be retained, in many cases each shoe muC-it be subject to final shaping operatior in situ on th3 actual surface to be protected. It will be understood th~t when using a preformed shoe the adhesive can be applied to the surface and/ol~ the shoe. The final shaping operation of the shoe ~ill be perf`ormed at the temperature of plastic de~formation of the a and may involve either of the techniques described above. I~
will be understood that the intimate cnrrelation in sh~pe can be achie~ed with relative ease by virtue of the super-plasticity.
Where the shaping operation is parformed ~ith the adhesive in situ-then it i~ of course a requirement of the adh,sive that it has a sufficien.tly long curing time to permit the alloy and component to be raised to the correct temperature~ and tc permi.t the sheet or sheets of alloy to be for~cd to the correct shape before the adhesive cures to a point at which relative move~ent between the sheet and the aircraft component is prevented~ In the event that a suitable adhesive is not available then it will be understood that the sheet or shoe of alloy could be finally shaped on thc actual surface but without adhesive present, the sheet or shoe then bein~ rernoved to permit application of the adhe,ive in temperature co~lditions s~iited to the adhesivs and t~e sheet er shoe then being ~rep~acsc so as to be secured by the adhe-sive. In such a te,chnique ~ spacar repr¢sentin~ the adhesive layar ma~- be interposad betwean the alloy a~d th~ sur~
.. ... ~................................................. . . ..
10~526 face duri~ i~inal sln~Li3-g of ~,he alloy so as to eJl.'.UJ:e eVCntl~al confoLinity be~weell ~he alloy and the surface whcn the spaccr is replaced by the aclhesive.
Some airfr~ime surface regions inCOLpOrate heater struc-tures 14 for de--iciny t]le surfaces in use. It is of course irnpor-tant to preserve the electrica] integrity as well as the mechani-cal inteyrity of such surface regions and thus such surface regions can be protected by sheets or shoes of super-plastic alloy as described above. It is envisaged -that in some instanccs, for example he]icopte ~-otor blades, it may be desirable ~o incorporate a heater into the protective alloy shoe prior to the application of the shoe to the surface to be protected. In such cases the alloy shoe may be preformed to the general surface shape and may then have a heater struc-ture 14 bonded on to its aircraft surface engaging face prior to fitting the shoe to the surface. It will of course be neces-- sary for the heater structure to be sufficiently flexible to conform to the surface contours of the airframe surface during the final shaping operation to ensure an even, void free thick-ness of adhesive. Various epoxy resin adhesives can be used and also phenolic resin adhesives and acrylic resin adhesives can be used if desired. I~here complex surface shapes are involved the heater structure 14 rnay be fitted to the surface prior to the - application of the sheets of alloy. In such cases the assembly of the sheets of alloy to the aircraft surface will be as des-cribed previously.
The adhesives used may obviously be painted or sprayed in liquid form or may be applied in the form of a paste or a prepared film.
109 ~5Z6 A su~t,able supor~pl~stic a110y is "SPZ all~" manufac~tl~ed by the Imp~rial Smelting Company Limited. The e~act form1~1~t~on of this alloy is not known to us. Ho~evars it io belia~e~ that the alloy is definable as "two-phase quzJcernary alloy havi~3:
a fine grain micro3tructure stabl0 at t;he temp~ature of 5upe~
plastic deformation9 consisting of ~illC within the range 70~,h by weight and aluminiurn 30~1 8~o by weight to which i~ added up to 0. 25~/o by weight of m~gnesium and up to 2.000,b by weight of one of the elements copper, nickel and silver~" and that many alloys within this definition may ~e suitable.
Reference is made herein to "the temperature of super-plastic deformation". It is to be understood that thi~ t~mp-erature is i~ practic~ a rang~ of tomperatures althou~h a particular te-nperature within the range may prove preferable in practice. ~or e~ample super plastic deformation of` a suitabl6 alloy can take place between approximately 150 C and 260 C but it i8 desirabLe in some applications in order to match the qual-i$ies o~ the adhesive used, the nature of the airframe regisn, and/or the degree o~ forming requirsd~ to perform the final shaping necessitating super-plastic deformation at the minim~lrn temperature at which pcrmanent de~ormation of the layer of` alloy can be en~ured. It will be u~derstood that the protecti-~e layer may be applied to the a~rcraft component wl1ich has the surface to be protected either while the component is on the aircraft or where po~sible while 1;he component i9 detached from tne aircraft.
~ 12 _ las~sz6 It ~ e recogni.sec~ at the ~hapin~ of` the protGctive layer t;o accuratoly conform to the contours peculiar to the act~ ur~ace to be protect;ed i.s a desideratu!n which is virtu~.lly in~po.~-~i b].e to achi~ve in practice u~inD the previou~ly known non-~uper-plas l;ic metal protective member
Claims (13)
1. A method of protecting a surface region of an aircraft including starting with a sheet or sheets of super-plastic alloy, engaging the sheet or sheets of super-plastic alloy with the surface region to be protected, shaping the sheet or sheets of super-plastic alloy at a temperature such that the super plastic properties of the alloy are exhibited to follow the surface contours of the surface region to be protected, and securing the protective layer of super-plastic alloy so formed to said surface region.
2. A method as claimed in claim 1 wherein the formed layer is secured to said surface region by means of an adhesive.
3. A method as claimed in claim 2 wherein the adhesive is applied to the surface region to be protected and/or the sheet or sheets of alloy prior to the shaping of the sheet or sheets.
4. A method as claimed in any one of claims 1 to 3 wherein the sheet or sheets are preformed to the general shape of the surface region and are finally shaped in situ so as to conform to the surface contours peculiar to the actual surface region.
5. A method as claimed in any one of claims 1 to 3 wherein the alloy from which the protective layer is formed is that known as:-"SPZ alloy" manufactured by the Imperial Smelting Company Limited;
or is a two-phase quaternary alloy having a fine grain micro-structure stable at the temperature of super-plastic deformation consisting of zinc within the range 70-82% by weight and aluminium 30-18% by weight to which is added up to 0.25% by weight of magnesium and up to 2% by weight of one of the elements copper, nickel and silver.
or is a two-phase quaternary alloy having a fine grain micro-structure stable at the temperature of super-plastic deformation consisting of zinc within the range 70-82% by weight and aluminium 30-18% by weight to which is added up to 0.25% by weight of magnesium and up to 2% by weight of one of the elements copper, nickel and silver.
6. A composite aircraft structure comprising a surface region, a protective layer of super-plastic alloy fitted onto said surface region, and means for securing said protective layer to said surface region thereby providing said composite structure.
7. A composite aircraft structure as claimed in claim 6, incorporating a heater structure, said protective layer of super-plastic alloy overlying said heater structure.
8. A composite structure as claimed in claim 6, wherein the alloy from which the protective layer is formed is that known as:
"SPZ alloy" manufactured by the Imperial Smelting Company Limited;
or is a two phase quaternary alloy having a fine grain micro-structure stable at the temperature of super-plastic deformation consisting of zinc within the range 70-82% by weight and aluminium 30-18% by weight to which is added up to 0.25% by weight of magnesium and up to 2% by weight of one of the elements copper, nickel and silver.
"SPZ alloy" manufactured by the Imperial Smelting Company Limited;
or is a two phase quaternary alloy having a fine grain micro-structure stable at the temperature of super-plastic deformation consisting of zinc within the range 70-82% by weight and aluminium 30-18% by weight to which is added up to 0.25% by weight of magnesium and up to 2% by weight of one of the elements copper, nickel and silver.
9. An aircraft surface region as claimed in claim 6, 7 or 8 in which the component whose surface is to be protected incor-porates strengthening fibres.
10. A protective shoe of a super-plasticalloy which is shaped to fit onto a predetermined aircraft surface region, said shoe being intended to be finally shaped in situ so as to completely follow the surface contours peculiar to the surface region for which it defines the protective layer.
11. A protective shoe as claimed in claim 10 incorporating a heater structure so that the protective shoe and the heater structure can be applied to the predetermined surface region in the same operation.
12. A protective shoe as claimed in claim 10 or claim 11 wherein the alloy from which the protective layer is formed is that known as:
"SPZ alloy" manufactured by the Imperial Smelting Company Limited;
or is a two phase quaternary alloy having a fine grain micro-structure stable at the temperature of super-plastic deformation consisting of zinc within the range 70-82% by weight and aluminium 30-18% by weight to which is added up to 0.25% by weight of magnesium and up to 2% by weight of one of the elements copper, nickel and silver.
"SPZ alloy" manufactured by the Imperial Smelting Company Limited;
or is a two phase quaternary alloy having a fine grain micro-structure stable at the temperature of super-plastic deformation consisting of zinc within the range 70-82% by weight and aluminium 30-18% by weight to which is added up to 0.25% by weight of magnesium and up to 2% by weight of one of the elements copper, nickel and silver.
13. An aircraft surface region protected in accord-ance with the method claimed in any one of claims 1 to 3.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB52941/76 | 1976-12-17 | ||
| GB52941/76A GB1593378A (en) | 1976-12-17 | 1976-12-17 | Aircraft surface structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094526A true CA1094526A (en) | 1981-01-27 |
Family
ID=10465925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA293,260A Expired CA1094526A (en) | 1976-12-17 | 1977-12-16 | Aircraft surface structure |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5378599A (en) |
| BR (1) | BR7708394A (en) |
| CA (1) | CA1094526A (en) |
| DE (1) | DE2756423A1 (en) |
| FR (1) | FR2374109A1 (en) |
| GB (1) | GB1593378A (en) |
| IN (1) | IN149367B (en) |
| IT (1) | IT1088448B (en) |
| NL (1) | NL187567C (en) |
| SE (1) | SE437004B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8609355D0 (en) * | 1986-04-17 | 1986-09-17 | Westland Plc | Erosion shields for aerofoil surfaces |
| FR2694900B1 (en) * | 1992-08-19 | 1994-10-21 | Hispano Suiza Sa | Method of manufacturing assemblies composed of two glued parts and comprising a forming step. |
| GB0913061D0 (en) | 2009-07-28 | 2009-09-02 | Rolls Royce Plc | A method of manufacturing a reinforcing edge for a turbo machine aerofoil |
| WO2024015207A1 (en) * | 2022-07-11 | 2024-01-18 | Wing Aviation Llc | Formed-metal sheet airframe for uavs |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1108081B (en) * | 1955-01-20 | 1961-05-31 | Sud Aviation | Device for manufacturing a rotating sash |
| US3065940A (en) * | 1956-06-22 | 1962-11-27 | Emil L Eckstein | Aircraft outer surface covering |
| US2959229A (en) * | 1957-10-01 | 1960-11-08 | United Aircraft Corp | Nickel plated propeller blade |
| US3712566A (en) * | 1971-02-25 | 1973-01-23 | Us Navy | Supersonic vehicle control surface having a thermally protective coating |
| DE2153434B2 (en) * | 1971-10-27 | 1972-11-09 | Licentia Patent Verwaltungs GmbH, 6000 Frankfurt | FASTENING OF EROSION PROTECTION EDGES TO AIRPLANE PROFILES |
-
1976
- 1976-12-17 GB GB52941/76A patent/GB1593378A/en not_active Expired
-
1977
- 1977-12-08 IN IN1704/CAL/77A patent/IN149367B/en unknown
- 1977-12-13 IT IT30637/77A patent/IT1088448B/en active
- 1977-12-15 SE SE7714234A patent/SE437004B/en not_active IP Right Cessation
- 1977-12-15 NL NLAANVRAGE7713936,A patent/NL187567C/en not_active IP Right Cessation
- 1977-12-16 BR BR7708394A patent/BR7708394A/en unknown
- 1977-12-16 CA CA293,260A patent/CA1094526A/en not_active Expired
- 1977-12-16 FR FR7738049A patent/FR2374109A1/en active Granted
- 1977-12-17 DE DE19772756423 patent/DE2756423A1/en active Granted
- 1977-12-17 JP JP15122377A patent/JPS5378599A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6158359B2 (en) | 1986-12-11 |
| FR2374109A1 (en) | 1978-07-13 |
| DE2756423C2 (en) | 1988-11-10 |
| JPS5378599A (en) | 1978-07-12 |
| BR7708394A (en) | 1978-07-25 |
| NL187567B (en) | 1991-06-17 |
| GB1593378A (en) | 1981-07-15 |
| NL7713936A (en) | 1978-06-20 |
| DE2756423A1 (en) | 1978-06-22 |
| IN149367B (en) | 1981-11-21 |
| SE437004B (en) | 1985-02-04 |
| SE7714234L (en) | 1978-06-18 |
| IT1088448B (en) | 1985-06-10 |
| NL187567C (en) | 1991-11-18 |
| FR2374109B1 (en) | 1982-04-02 |
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