U.S. patent application number 13/663543 was filed with the patent office on 2014-05-01 for composite structures having bondlines with matched electrical conductivity.
This patent application is currently assigned to THE BOEING COMPANY. The applicant listed for this patent is The Boeing Company. Invention is credited to Patrice K. Ackerman, Diane L. Heidlebaugh.
Application Number | 20140117022 13/663543 |
Document ID | / |
Family ID | 49305094 |
Filed Date | 2014-05-01 |
United States Patent
Application |
20140117022 |
Kind Code |
A1 |
Ackerman; Patrice K. ; et
al. |
May 1, 2014 |
Composite Structures Having Bondlines with Matched Electrical
Conductivity
Abstract
Two composite laminates are joined together by a bondline having
portions exposed to the ambient environment. The bondline contains
scrim having an electrical conductivity and impedance matched to
that of the laminates in order to mitigate effects of lightning
strikes.
Inventors: |
Ackerman; Patrice K.; (Kent,
WA) ; Heidlebaugh; Diane L.; (Kenmore, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Boeing Company; |
|
|
US |
|
|
Assignee: |
THE BOEING COMPANY
Chicago
IL
|
Family ID: |
49305094 |
Appl. No.: |
13/663543 |
Filed: |
October 30, 2012 |
Current U.S.
Class: |
220/562 ; 156/60;
29/428; 403/265; 428/212; 428/35.7 |
Current CPC
Class: |
Y10T 428/24942 20150115;
B29C 66/73141 20130101; Y10T 29/49826 20150115; B29C 66/72141
20130101; B29C 65/5028 20130101; B29C 66/112 20130101; B29C
66/43441 20130101; Y10T 156/10 20150115; B29C 66/72143 20130101;
B64D 37/02 20130101; B29L 2031/3076 20130101; B29C 65/4855
20130101; B29C 65/5021 20130101; Y02T 50/40 20130101; Y10T 428/1352
20150115; B29C 65/5057 20130101; B29C 66/43 20130101; B29L
2031/7172 20130101; Y10T 403/47 20150115; B64F 5/40 20170101; B29C
66/1122 20130101; B29C 66/114 20130101; B64D 45/02 20130101; B29C
66/7212 20130101; B29C 66/7212 20130101; B29K 2307/04 20130101 |
Class at
Publication: |
220/562 ; 29/428;
428/212; 428/35.7; 403/265; 156/60 |
International
Class: |
B32B 1/02 20060101
B32B001/02; B32B 37/12 20060101 B32B037/12; B32B 7/02 20060101
B32B007/02; F16B 12/04 20060101 F16B012/04; B60K 15/03 20060101
B60K015/03; B23P 11/00 20060101 B23P011/00 |
Claims
1. A composite laminate structure, comprising: first and second
fiber reinforced plastic resin laminates each having an electrical
impedance; and a structural bondline joining the first and second
laminates together, the bondline having an electrical impedance
substantially matching the electrical impedance of the first and
second laminates.
2. The composite laminate structure of claim 1, wherein: the fiber
reinforcement in each of the first and second fiber reinforced
plastic resin laminates are carbon fibers, and the structural
bondline includes an adhesively impregnated scrim having an
electrical impedance that substantially matches the electrical
impedance of the first and second laminates.
3. The composite laminate structure of claim 1, wherein at least a
portion of the structural bondline is exposed to an ambient
environment.
4. The composite laminate structure of claim 1, wherein the first
and second laminates and the structural bondline form a
T-joint.
5. The composite laminate structure of claim 1, wherein: the first
and second laminates form part of a fuel tank having an open
interior, and a portion of the structural bondline is exposed to
the open interior of the fuel tank.
6. The composite laminate structure of claim 1, wherein the
structural bondline includes an adhesively impregnated scrim having
an AC conductivity that substantially matches the AC conductivity
of the first and second laminates.
7. A composite laminate structure, comprising: a first carbon fiber
reinforced plastic laminate having a first electrical impedance; a
second carbon fiber reinforced plastic laminate having a second
electrical impedance substantially matching the first electrical
impedance; and an adhesive bondline between the first and second
laminates, the adhesive bond including an adhesive and a scrim
having a third electrical impedance substantially matching the
first and second electrical impedances.
8. The composite laminate structure of claim 7, wherein: the first
and second laminates form part of a fuel tank having an open
interior adapted to store fuel, and a portion of the adhesive
bondline is exposed to the open interior of the fuel tank.
9. The composite laminate structure of claim 7, wherein the first
and second laminates and the adhesive bondline form a T-joint.
10. The composite laminate structure of claim 7, wherein: each of
the first, second and third electrical impedances include a
resistive component and a reactive component, the resistive
components are substantially equal, and the reactive components are
substantially equal.
11. The composite laminate structure of claim 7, wherein the scrim
is formed of carbon fibers.
12. The composite laminate structure of claim 7, wherein the first
and second laminates and the bondline have substantially the same
AC conductivity.
13. A composite aircraft fuel tank having lightning protection,
comprising: at least a first carbon fiber reinforced plastic
laminate wall; at least a second carbon fiber reinforced plastic
laminate wall; an adhesive bondline joining the first and second
laminate walls, the adhesive bondline including an electrically
conductive scrim having an electrical impedance substantially
matching the electrical impedance of each of the first and second
laminate walls.
14. The composite aircraft fuel tank of claim 13, wherein at least
a portion of the adhesive bondline is adapted to be exposed to fuel
vapors within the fuel tank.
15. A method of providing lightning protection of for a bond joint
between two cured carbon fiber reinforced plastic laminates,
comprising: installing scrim in the bond joint having an electrical
impedance that substantially matches the electrical impedance each
of the two carbon fiber reinforced plastic laminates.
16. The method of claim 15, wherein installing the scrim includes
impregnating the scrim with an adhesive.
17. The method of claim 16, wherein the adhesive is one of a film
adhesive and a paste adhesive.
18. The method of claim 15 wherein the scrim is formed of carbon
fibers.
19. The method of claim 15, wherein the laminates and the scrim
possess substantially the same electrical conductivity.
20. The method of claim 16, wherein installing the scrim in the
bond joint includes: assembling the two laminates in a T-shaped
configuration, and placing the scrim between an edge of one of the
two laminates, and a face of the other of the two laminates.
21. An aircraft fuel tank having a exposed bond joint produced by
the method of claim 15.
22. A method of reducing the electrical potential across an exposed
bondline between two carbon fiber reinforced plastic laminates,
comprising: determining the electrical conductivity of each of the
two laminates; selecting a scrim having an electrical conductivity
substantially matching the determined electrical conductivity of
each of the two laminates; installing the scrim and an adhesive
between the two laminates; curing the adhesive.
23. A method of fabricating a composite structure having an exposed
bond protected against lightning strikes, comprising: laying up
first and second carbon fiber reinforced plastic pre-preg
laminates; curing the first and second pre-preg laminates; joining
the first and second cured laminates with a bond joint, including
selecting a scrim having an electrical impedance substantially
matching the electrical impedance of each of the first and second
laminates, impregnating the scrim with a bonding adhesive,
installing the impregnated scrim between the first and second
laminates to form a bondline, and curing the adhesive.
Description
BACKGROUND INFORMATION
[0001] 1. Field
[0002] This disclosure generally relates to techniques for bonding
composite structures, and deals more particularly with methods for
mitigating the effects of lightning strikes at bondlines.
[0003] 2. Background
[0004] Fiber reinforced composite structures, such as, without
limitation, carbon fiber reinforced plastics (CFRP) may be bonded
together along a bondline using a structural adhesive. The bondline
may be strengthened and reinforced by introducing one or more
layers of scrim into the adhesive.
[0005] In aircraft applications, areas of composite structures such
as fuselage skins are sometimes repaired or reworked by adhesively
bonding composite repair patches to the structure. In order to
reduce the effects of lightning strikes on the repair patch, it is
necessary to provide a continuous electrical path between the
repair patch and the structure to which it is bonded in order to
dissipate electrical current flow.
[0006] In order to provide electrical continuity between a
composite repair patch and the composite structure to which it is
bonded, an electrically conductive scrim may be placed in the
bondline. A problem arises, however, when portions of the bondline
are exposed to the ambient environment. A lightning strike may
generate an undesirable electrical potential across the bondline.
In order to avoid the effects of an undesirable electrical
potential across the bondline, the exposed areas of the bondline
are covered with an electrically insulating sealant. Although
sealants are effective, they increase the weight of the aircraft,
and are both time-consuming and labor-intensive, adding to
manufacturing costs.
[0007] Accordingly, there is a need for a method of joining
composite structures along bondlines that mitigate the effects of
lightning strikes, and reduce accompanying electrical potentials
occurring across exposed bondlines. There is also a need for a
method of bonding composite structures together which obviates the
need for sealants to cover exposed portions of bondlines between
the structures.
SUMMARY
[0008] The disclosed methods provide composite structures joined
together along bondlines that have electrical conductivities which
are matched to the structures which they join. The use of bondlines
having conductivities matched to those of the structures reduces an
electrical potential across exposed portions of the bondline. The
use of sealants to cover exposed portions of bondlines may be
reduced or eliminated, thereby reducing aircraft weight and
manufacturing costs.
[0009] According to one disclosed embodiment, a composite laminate
structure is provided comprising first and second fiber reinforced
plastic resin laminates each having an electrical impedance, and a
structural bondline joining the first and second laminates
together. The bondline has an electrical impedance substantially
matching the electrical impedance of the first and second
laminates. The fiber reinforcement in each of the first and second
fiber reinforced plastic resin laminates are carbon fibers, and the
bondline includes an adhesively impregnated scrim having an
electrical impedance that substantially matches the electrical
impedance of the first and second laminates. At least a portion of
the bondline is exposed to an ambient environment. The first and
second laminates and the bondline may form a T-joint. The first and
second laminates may form part of a fuel tank having an open
interior, and in which a portion of the bondline is exposed to the
open interior of the fuel tank. The bondline includes an adhesively
impregnated scrim having an AC (alternating current) conductivity
that substantially matches the AC conductivity of the first and
second laminates.
[0010] According to another embodiment, a composite laminate
structure is provided comprising a first carbon fiber reinforced
plastic laminate having a first electrical impedance, and a second
carbon fiber reinforced plastic laminate having a second electrical
impedance substantially matching the first electrical impedance.
The laminate structure further includes an adhesive bondline
between the first and second laminates. The adhesive bond includes
an adhesive and a scrim having a third electrical impedance
substantially matching the first and second electrical impedances.
The first and second laminates may form part of a fuel tank having
an open interior adapted to store fuel, wherein a portion of the
adhesive bondline is exposed to the open interior of the fuel tank.
The first and second laminates and the adhesive bondline may form a
T-joint. Each of the first, second and third electrical impedances
include a resistive component and a reactive component. The
resistive components are substantially equal, and the reactive
components are substantially equal. The scrim may be formed of
carbon fibers. The first and second laminates and the bondline have
substantially the same AC conductivity.
[0011] According to still another embodiment, a composite aircraft
fuel tank is provided with lightning protection. The lighting
protection comprises at least a first carbon fiber reinforced
plastic laminate wall, at least a second carbon fiber reinforced
plastic laminate wall, and an adhesive bondline joining the first
and second laminate walls, the adhesive bondline including an
electrically conductive scrim having an electrical impedance
substantially matching the electrical impedance of each of the
first and second laminate walls. At least a portion of the adhesive
bondline is adapted to be exposed to fuel vapors within the fuel
tank.
[0012] According to still another embodiment, a method of providing
lightning protection for a bond joint between two cured carbon
fiber reinforced plastic laminates comprises installing scrim in
the bond joint having an electrical impedance that substantially
matches the electrical impedance each of the two carbon fiber
reinforced plastic laminates. Installing the scrim includes
impregnating the scrim with an adhesive. The adhesive may be one of
a film adhesive and a paste adhesive. The scrim may be formed of
carbon fibers. The laminates and the scrim may possess
substantially the same electrical conductivity. Installing the
scrim in the bond joint includes assembling the two laminates in a
T-shaped configuration, and placing the scrim between an edge of
one of the two laminates, and a face of the other of the two
laminates.
[0013] According to a further embodiment, a method is provided of
reducing the electrical potential across an exposed bondline
between two, carbon fiber reinforced plastic laminates. The method
comprises determining the electrical conductivity of each of the
two laminates, selecting a scrim having an electrical conductivity
substantially matching the determined electrical conductivity of
each of the two laminates, installing the scrim and an adhesive
between the two laminates, and curing the adhesive.
[0014] According to still further embodiment, a method is provided
of fabricating a composite structure having an exposed bond
protected against lightning strikes. The method comprises laying up
first and second carbon fiber reinforced plastic pre-preg
laminates, curing the first and second pre-preg laminates, and
joining the first and second cured laminates with a bond joint.
Joining the first and second cured laminates with the bond joint
may include selecting a scrim having an electrical impedance
substantially matching the electrical impedance of each of the
first and second laminates, impregnating the scrim with a bonding
adhesive, installing the impregnated scrim between the first and
second laminates to form a bondline, and curing the adhesive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The novel features believed characteristic of the
illustrative embodiments are set forth in the appended claims. The
illustrative embodiments, however, as well as a preferred mode of
use, further objectives and advantages thereof, will best be
understood by reference to the following detailed description of an
illustrative embodiment of the present disclosure when read in
conjunction with the accompanying drawings, wherein:
[0016] FIG. 1 is an illustration of a perspective view of a bonded
composite structure having a bondline employing electrically
conductive scrim according to the disclosed embodiments.
[0017] FIG. 2 is an illustration of an end view of the area
designated as FIG. 2 in FIG. 1.
[0018] FIG. 3 is an illustration of a cross-sectional view of two
laminate structures joined together by a lap joint employing the
disclosed scrim.
[0019] FIG. 4 is an illustration of a perspective view of the scrim
along with two layers of adhesive used to form the bondline.
[0020] FIG. 5 is an illustration of a graph showing electrical
current flow resulting from a typical lightning strike.
[0021] FIG. 6 is an illustration of a circuit diagram of an
impedance.
[0022] FIG. 7 is an illustration of a perspective view of an
aircraft fuel tank, portions broken away to reveal the interior of
the tank.
[0023] FIG. 8 is an illustration of a flow diagram of a method of
co-curing two composite pre-pregs along a bondline.
[0024] FIG. 9 is an illustration of a flow diagram of a method of
fabricating a bonded precured structure employing the disclosed
scrim.
[0025] FIG. 10 is an illustration of a flow diagram of aircraft
production and service methodology.
[0026] FIG. 11 is an illustration of a block diagram of an
aircraft.
DETAILED DESCRIPTION
[0027] Referring first to FIGS. 1 and 2, a composite structure 20
comprises first and second composite pre-pregs 24, 26, which may be
formed of by laying up pre-preg plies, such as a CFRP. In this
example, the first and second pre-pregs 24, 26 together are joined
together along a bondline 22 between a face 29 of the first
pre-preg 24 and an edge 27 of the second pre-preg 26, effectively
forming a butt joint 31. The bondline 22 includes exposed portions
28, 30 at the ends of the bondline 22, which are exposed to the
surrounding ambient environment. As will be discussed below, the
bondline 22 has an electrical conductivity .sigma..sub.1 and
impedance Z.sub.1 that substantially match the electrical
conductivity .sigma..sub.2 and impedance Z.sub.2 of each of the
first and second pre-pregs 24, 26. This matching of the electrical
conductivities .sigma..sub.1, .sigma..sub.2 and impedances Z.sub.1,
Z.sub.2 reduces or eliminates build-up of an undesirable electrical
potential or charge "V" (FIG. 2) between the pre-pregs 24, 26 along
the exposed portions 28, 30 of the bondline 22.
[0028] The disclosed bondline 22 may be employed to form other
types of bonded joints between two laminate structures. For
example, referring to FIG. 3, the disclosed bondline 22 may be
employed to form a lap joint 35 between first and second composite
pre-pregs 24, 26. In this example, the bondline 22 also has exposed
portions 28, 30 which need not be sealed as a result of the
electrical conductivity .sigma..sub.l and impedance Z.sub.1 of the
bondline 22 being matched to the electrical conductivity
.sigma..sub.2 and impedance Z.sub.2 of the first and second
pre-pregs 24, 26.
[0029] Attention is now directed to FIG. 4 which illustrates the
components used to form the bondline 22. A scrim 32 is sandwiched
between two layers 34, 36 of a suitable structural adhesive. The
scrim 32 may be in any of the numerous configurations such as,
without limitation, a mesh, knitted mat or random fiber mat
comprising intersecting strands of electrically conductive fibers.
The conductive fibers have an AC conductivity .sigma..sub.1 and an
impedance Z.sub.1 respectively matching the AC conductivity
.sigma..sub.2 and impedance Z.sub.2 of the first and second
pre-pregs 24, 26. The fibers may comprise a single material, or may
comprise fibers of multiple types of materials which collectively
have the required AC conductivity .sigma..sub.1 and impedance
Z.sub.1 matched to the AC conductivity .sigma..sub.2 and impedance
Z.sub.2 of the pre-pregs 24, 26. In the case of first and second
pre-pregs 24, 26 comprising CFRPs, then the fibers of the scrim 32
may also be formed of carbon fibers similar or identical to those
forming the carbon fiber reinforcement in the first and second
pre-pregs 24, 26. While only a single layer of scrim 32 is
illustrated in FIG. 4, multiple layers of the scrim 32 may be
employed in a single bondline 22.
[0030] Each of the adhesive layers 34, 36 may comprise an adhesive
resin film or an adhesive resin paste which adheres to the CFRP
plies of the pre-pregs 24, 26. The scrim 32 may be embedded into
and adhere to each of the adhesive layers 34, 36, as by pressing
the scrim 32 into the adhesive layers 34, 36. Other techniques for
integrating bonding adhesive with the scrim 32 may be possible,
including impregnating the scrim 32 with the adhesive. The scrim 32
is configured to provide continuous electrical conductivity
throughout the bondline 22 and may also serve as a binding
matrix.
[0031] As previously mentioned, the scrim 32 possesses an AC
conductivity .sigma..sub.1 and an impedance Z.sub.1 that
substantially match the electrical conductivity .sigma..sub.2 and
impedance Z.sub.2 of each of the composite pre-pregs joined by the
bondline 22. Electrical conductivity .sigma. is a measure of the
material's ability to conduct electric current. In the case of a
lightning strike causing electrical current to flow through the
pre-pregs 24, 26, and through the bondline 22, the current flow is
typically not constant, but varies, similar to an alternating
current (AC). For example, FIG. 5 is a graph showing electrical
current flow 37 over time 39, produced by a typical lightning
strike. During an initial time period "A", the current flow begins
with a sharp spike 43 at the initial lightning attachment 41, then
decays slowly during time period "B", may be somewhat constant
during time period "C", and then quickly increases during time
period "D", forming another sharp spike 45 immediately before
detachment at 47. Accordingly, the pre-pregs 24, 26, and the scrim
32 each have respective AC conductivities .sigma..sub.1,
.sigma..sub.2 and respective impedances Z.sub.1, Z.sub.2 (FIGS. 2
and 3).
[0032] FIG. 6 is a circuit diagram representing the components of
each of the impedances Z.sub.1, Z.sub.2. The impedance Z is the sum
of a resistive component R.sub.x and a reactive component X, thus,
Z=R.sub.x+X. The reactive component X, or "reactance", includes
inductance L and capacitance C, and represents the opposition of
the scrim 32, viewed as a circuit, to a change of electric current
or voltage caused by the lightning strike. Because the AC
conductivity .sigma..sub.1 and the impedance Z.sub.1 of the scrim
32, and thus of the bondline 22, are respectively matched to those
of the first and second pre-pregs 24, 26, the current flow through
the pre-pregs 24, 26 passes unimpeded through the bondline 22,
rather "seeing" a discontinuity in the bondline 22 which may
results in the build-up of an undesirable electrical potential or
charge "V" (FIG. 2) across the bondline 22 in the area of the
exposed portions 28, 30.
[0033] The bondline 22 described above having a "matched"
electrical conductivity .sigma..sub.1 and a "matched" impedance
Z.sub.1 may be used in a wide variety of composite laminate
structures to mitigate the effects electrical current flows due to
lightning strikes. For example, the disclosed bondline 22 may be
employed in a composite aircraft fuel tank 42 shown in FIG. 7. The
fuel tank 42 includes a composite laminate top 44, bottom 46 and
sides 48, 50 forming an internal volume 55. The fuel tank 42 may
further include internal ribs 52 as well as a baffle walls 54, each
of which are bonded along its top and bottom edges to the top and
bottom walls 44, 46 respectively, by a T-joint and bondline 22
similar to that shown in FIGS. 1 and 2 which use the scrim 32 shown
in FIG. 4. The disclosed bondline 22 may also be employed to bond
the repair patches (not shown) to underlying composite structures,
such as CFRP laminate skins.
[0034] Attention is now directed to FIG. 8 which illustrates the
overall steps of a method of reducing the buildup of an electrical
potential or charge across a bond line 22 in the area of exposed
portions 28, 30 of the bondline 22 between two pre-pregs 24, 26
subjected to the effects of lightning strikes. At step 56, the
electrical conductivities .sigma..sub.2 of each of the two
pre-pregs 24, 26 are determined. Next at 58, scrim used in the
bondline 22 is selected which has an electrical conductivity
.sigma..sub.1 substantially matching the electrical conductivity
.sigma..sub.2 of each of the two pre-pregs 24, 26. At step 60, the
scrim 32 along with the adhesive is installed between the pre-pregs
24, 26, following which the pre-pregs 24, 26 and the pre-pregs and
the adhesive are co-cured at step 62.
[0035] FIG. 9 broadly illustrates the steps of a method of
fabricating a CFRP laminate structure 20 having bondlines 22
provided with lightning protection. At step 64, first and second
CFRP pre-pregs 24, 26 are laid up, and formed to shape, as
required. At step 66, each of the first and second CFRP pre-pregs
24, 26 are cured to form laminates. At step 68 a scrim 32 is
selected having an electrical impedance Z.sub.1 substantially
matching the electrical impedance Z.sub.2 of the first and second
pre-preg laminates 24, 26. At 70, the scrim 32 is impregnated or
otherwise integrated into a suitable bonding adhesive. At step 72,
the impregnated scrim is installed between surfaces of the first
and second pre-preg laminates 24, 26 to form a bondline 22 which
may include exposed portions 28, 30. Finally, at 74, the adhesive
is cured.
[0036] Embodiments of the disclosure may find use in a variety of
potential applications, particularly in the transportation
industry, including for example, aerospace, marine, automotive
applications and other application where autoclave curing of
composite parts may be used. Thus, referring now to FIGS. 10 and
11, embodiments of the disclosure may be used in the context of an
aircraft manufacturing and service method 76 as shown in FIG. 10
and an aircraft 78 as shown in FIG. 11. Aircraft applications of
the disclosed embodiments may include, for example, without
limitation, fabrication of composite laminate assemblies and
subassemblies requiring bonded joints that require protection
against the effects of lightning strikes on an aircraft. During
pre-production, exemplary method 76 may include specification and
design 80 of the aircraft 78 and material procurement 82. During
production, component and subassembly manufacturing 84 and system
integration 86 of the aircraft 78 takes place. Thereafter, the
aircraft 78 may go through certification and delivery 88 in order
to be placed in service 90. While in service by a customer, the
aircraft 78 is scheduled for routine maintenance and service 92,
which may also include modification, reconfiguration,
refurbishment, and so on.
[0037] Each of the processes of method 76 may be performed or
carried out by a system integrator, a third party, and/or an
operator (e.g., a customer). For the purposes of this description,
a system integrator may include without limitation any number of
aircraft manufacturers and major-system subcontractors; a third
party may include without limitation any number of vendors,
subcontractors, and suppliers; and an operator may be an airline,
leasing company, military entity, service organization, and so
on.
[0038] As shown in FIG. 11, the aircraft 78 produced by exemplary
method 76 may include an airframe 94 with a plurality of systems 96
and an interior 98. Examples of high-level systems 96 include one
or more of a propulsion system 100, an electrical system 102, a
hydraulic system 104, and an environmental system 106. Any number
of other systems may be included. Although an aerospace example is
shown, the principles of the disclosure may be applied to other
industries, such as the marine and automotive industries.
[0039] Systems and methods embodied herein may be employed during
any one or more of the stages of the production and service method
76. For example, components or subassemblies corresponding to
production process 84 may be fabricated or manufactured in a manner
similar to components or subassemblies produced while the aircraft
96 is in service. Also, one or more apparatus embodiments, method
embodiments, or a combination thereof may be utilized during the
production stages 84 and 86, for example, by substantially
expediting assembly of or reducing the cost of an aircraft 78.
Similarly, one or more of apparatus embodiments, method
embodiments, or a combination thereof may be utilized while the
aircraft 78 is in service, for example and without limitation, to
maintenance and service 92.
[0040] The description of the different illustrative embodiments
has been presented for purposes of illustration and description,
and is not intended to be exhaustive or limited to the embodiments
in the form disclosed. Many modifications and variations will be
apparent to those of ordinary skill in the art. Further, different
illustrative embodiments may provide different advantages as
compared to other illustrative embodiments. The embodiment or
embodiments selected are chosen and described in order to best
explain the principles of the embodiments, the practical
application, and to enable others of ordinary skill in the art to
understand the disclosure for various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *