Court Opinion

ID: 4678024
Source: CourtListenerOpinion
Date Created: 2021-04-16 15:01:05.8343+00
Date Added: 2024-06-11T08:03:42.313261
License: Public Domain

Case: 20-1755   Document: 51    Page: 1   Filed: 04/16/2021

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

   RAYTHEON TECHNOLOGIES CORPORATION,
                Appellant

                           v.

          GENERAL ELECTRIC COMPANY,
                    Appellee

   ANDREW HIRSHFELD, PERFORMING THE
    FUNCTIONS AND DUTIES OF THE UNDER
       SECRETARY OF COMMERCE FOR
 INTELLECTUAL PROPERTY AND DIRECTOR OF
 THE UNITED STATES PATENT AND TRADEMARK
                   OFFICE,
                   Intervenor
             ______________________

                       2020-1755
                 ______________________

     Appeal from the United States Patent and Trademark
 Office, Patent Trial and Appeal Board in No. IPR2018-
 01442.
                  ______________________

                Decided: April 16, 2021
                ______________________

     LAUREN ANN DEGNAN, Fish & Richardson P.C., Wash-
 ington, DC, argued for appellant. Also represented by
 CHRISTOPHER DRYER, WALTER KARL RENNER; KENNETH
 WAYNE DARBY, Austin, TX; TIMOTHY RAWSON, San Diego,
Case: 20-1755     Document: 51     Page: 2    Filed: 04/16/2021

 2                           RAYTHEON TECHNOLOGIES CORP. v.
                                 GENERAL ELECTRIC COMPANY

 CA; MICHAEL VALAIK, Bartlit Beck Herman Palenchar &
 Scott LLP, Chicago, IL.

    BRIAN E. FERGUSON, Weil, Gotshal & Manges LLP,
 Washington, DC, argued for appellee. Also represented by
 DANIEL MUSHER, CHRISTOPHER PEPE; ANISH R. DESAI, New
 York, NY.

     ROBERT J. MCMANUS, Office of the Solicitor, United
 States Patent and Trademark Office, Alexandria, VA, for
 intervenor. Also represented by THOMAS W. KRAUSE,
 FRANCES LYNCH, FARHEENA YASMEEN RASHEED.
                 ______________________

     Before LOURIE, CHEN, and HUGHES, Circuit Judges.
 CHEN, Circuit Judge.
     A typical 35 U.S.C. § 103 obviousness case often turns
 on whether an asserted prior art reference teaches a par-
 ticular disputed claim limitation or whether a skilled arti-
 san would have been motivated at the time of invention to
 combine the teachings of different references. There usu-
 ally is no dispute about whether an asserted prior art ref-
 erence is “self-enabling,” i.e., whether a skilled artisan can
 make and use the subject matter disclosed in the reference.
 This appeal, however, requires us to consider when a refer-
 ence needs to have a self-enabling disclosure for supporting
 an obviousness case. We have explained that there is no
 absolute requirement for a relied-upon reference to be self-
 enabling in the § 103 context, so long as the overall evi-
 dence of what was known at the time of invention estab-
 lishes that a skilled artisan could have made and used the
 claimed invention. We have also previously expounded the
 principle that if an obviousness case is based on a non-self-
 enabled reference, and no other prior art reference or evi-
 dence would have enabled a skilled artisan to make the
 claimed invention, then the invention cannot be said to
 have been obvious.
Case: 20-1755    Document: 51          Page: 3   Filed: 04/16/2021

 RAYTHEON TECHNOLOGIES CORP.      v.                           3
 GENERAL ELECTRIC COMPANY

     In the present case, Raytheon 1 appeals a final inter
 partes review decision of the Patent Trial and Appeal
 Board (Board) finding claims 3 and 16 of U.S. Patent No.
 9,695,751 (’751 patent) unpatentable as obvious in view of
 the Knip reference. In particular, the Board found that
 Knip discloses the claimed power density limitation for a
 geared gas turbine engine. During the proceeding, Ray-
 theon submitted unrebutted evidence establishing that
 Knip’s disclosure of highly aggressive performance param-
 eters for a futuristic turbine engine was based on the use
 of nonexistent composite materials. In response, the peti-
 tioner, General Electric Company (GE), never put forth any
 evidence suggesting a skilled artisan could have made a
 turbine engine with the power density recited in the
 claims. Because the relied-upon prior art fails to enable a
 skilled artisan to make and use the claimed invention, we
 reverse.
                        BACKGROUND
                              A
     Raytheon owns the ’751 patent, which is directed to gas
 turbine engines. See ’751 patent at Abstract. Gas turbine
 engines are commonly used for powering airplanes. At a
 high level, a gas turbine engine generally consists of a fan
 section, a compressor section, a combustor section, and a
 turbine section. See id. at col. 4 ll. 8–10. The compressor
 section typically includes a low-pressure and high-pressure
 compressor. See id. at col. 4 ll. 33–59. Similarly, the tur-
 bine section often consists of low- and high-pressure tur-
 bines. See id.

    1    United Technologies Corporation (UTC) is the orig-
 inal assignee of the ’751 patent. After the Board issued its
 final written decision, UTC merged with Raytheon Com-
 pany to form Raytheon Technologies Corporation (Ray-
 theon), the current owner of the ’751 patent.
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 4                            RAYTHEON TECHNOLOGIES CORP. v.
                                  GENERAL ELECTRIC COMPANY

      Gas turbine engines produce thrust by drawing air into
 the front of the engine, mixing it with fuel and burning the
 mixture, and ejecting exhaust gasses. See id. at col. 4 ll.
 12–17. Turbofan engines, a particular type of gas turbine
 engine relevant here, utilize an air bypass duct to increase
 thrust by ejecting some of the air through a bypass nozzle.
 Turbofan engines can be “direct-drive” or “geared.” In a
 direct-drive engine, the fan is directly connected to the low-
 pressure compressor and turbine such that all three turn
 at the same speed. Alternatively, “geared” engines include
 a gearbox, allowing the turbine and compressor to rotate at
 a different, i.e., higher, speed than the fan. See id. at col. 1
 ll. 37–46. When a compressor or turbine can spin at a
 higher rotational speed, it can perform the same amount of
 work in fewer stages. Fewer stages, in turn, leads to re-
 duced volume and weight of the turbine and the engine,
 resulting in greater efficiency.
     The ’751 patent generally claims a geared gas turbine
 engine with two turbines and a specific number of fan
 blades and turbine rotors and/or stages. The key distin-
 guishing feature of the claims is the recitation of a “power
 density” range that the patent describes as being “much
 higher than in the prior art.” See id. at col. 10 ll. 54–55.
 The ’751 patent defines power density as the “sea-level-
 takeoff thrust” (SLTO thrust) divided by the engine turbine
 volume. See id. at col. 10 ll. 22–25 and claims 1, 15.
     Claims 1–3 are reproduced in part below:
     1. A gas turbine engine comprising:
     a fan including a plurality of fan blades . . . ;
     a compressor section;
     a combustor in fluid communication with the com-
     pressor section;
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 RAYTHEON TECHNOLOGIES CORP.       v.                           5
 GENERAL ELECTRIC COMPANY

     a turbine section in fluid communication with the
     combustor, the turbine section including a fan
     drive turbine and a second turbine . . . ; and
     a speed change system configured to be driven by
     the fan drive turbine to rotate the fan about the
     axis; and
     a power density at Sea Level Takeoff greater than
     or equal to 1.5 lbf/in3 and less than or equal to 5.5
     lbf/in3 and defined as thrust in lbf measured by a
     volume of the turbine section in in3 measured be-
     tween an inlet of a first turbine vane in said second
     turbine to an exit of a last rotating airfoil stage in
     said fan drive turbine.
     2. The gas turbine engine as recited in claim 1,
     wherein the fan drive turbine has from three to six
     stages.
     3. The gas turbine engine as recited in claim 2,
     wherein said number of fan blades is less than 18
     and the second turbine has two stages.
 Id. at claims 1–3.
     Independent claim 15 is substantively identical to
 claim 1 but requires the speed change system to have “a
 gear reduction.” See id. at claim 15. And claim 16, which
 depends from claim 15, contains the same additional limi-
 tation as claim 3. See id. at claim 16.
                               B
     GE petitioned for inter partes review of claims 1–4, 9–
 10, 15–16, and 23 of the ’751 patent. See J.A. 102–89. GE’s
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 6                           RAYTHEON TECHNOLOGIES CORP. v.
                                 GENERAL ELECTRIC COMPANY

 petition relied on either Knip 2 or Gliebe 3 as a primary ref-
 erence for its asserted unpatentability grounds. See J.A.
 124–25. GE challenged claims 1–4, 9–10, and 15–16 as ob-
 vious in light of Knip alone and/or Knip in view of a second-
 ary reference. See id. GE also challenged claims 1–2 and
 15 as anticipated by or rendered obvious by Gliebe, alone,
 and claim 23 as rendered obvious by Gliebe and a second-
 ary reference. See id.
      Knip is a 1987 NASA technical memorandum that en-
 visions superior performance characteristics for an imag-
 ined “advanced [turbofan] engine” “incorporating all
 composite materials.” See J.A. 902. Although the construc-
 tion of a turbofan engine incorporating such composite ma-
 terials was undisputedly unattainable at that time (and,
 according to the record, continues to this day to be beyond
 reality), an imagined application of these “revolutionary”
 composite materials to a turbofan engine allowed the au-
 thor of Knip to assume aggressive performance parameters
 for an “advanced engine,” including then-unachievable
 pressure ratios and turbine temperatures. See J.A. 906.
 Knip predicts that the use of these composite materials
 would permit the resulting advanced engine to achieve sig-
 nificant reductions in engine volume and weight leading to
 “improvement in engine performance and thrust-to-
 weight-ratios.” See J.A. 903, 908. Although Knip discloses
 numerous performance parameters associated with its fu-
 turistic engine, it does not explicitly disclose SLTO thrust,
 turbine volume, or power density.
     In its petition, GE argued that both Knip and Gliebe
 disclose performance parameters of a kind that would

     2  G. Knip, Analysis of an Advanced Technology Sub-
 sonic Turbofan Incorporating Revolutionary Materials
 (May 1987). J.A. 901–25.
     3  P. Gliebe, Ultra-High Bypass Engine Aeroacoustic
 Study (Oct. 2003). J.A. 792–900.
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 RAYTHEON TECHNOLOGIES CORP.    v.                           7
 GENERAL ELECTRIC COMPANY

 permit a skilled artisan to derive the power density of their
 respective engines from those disclosed parameters. See
 J.A. 140–45, 180–83. According to GE, those power densi-
 ties render obvious or anticipate the claimed power density
 range, proving the challenged claims unpatentable. In the
 alternative, GE argued that because power density is a “re-
 sult-effective variable,” see J.A. 145–53, “even if Knip did
 not disclose a turbine section volume and/or SLTO thrust
 that resulted in a power density within the claimed range,
 it would have nevertheless been obvious to a [skilled arti-
 san] to modify the thrust and/or turbine volume for Knip’s
 engine to optimize the power density.” J.A. 726; see also
 J.A. 709.
     After the Board instituted the inter partes review of the
 challenged claims, Raytheon disclaimed claims 1–2, 4, 9–
 10, 15, and 23, to “streamline” the issues, see Oral Arg. at
 1:28–50, 3:57–4:24. The disclaimer mooted all grounds re-
 lying on Gliebe, leaving only dependent claims 3 and 16,
 which were challenged exclusively on Knip-based grounds.
 See J.A. 124–25. Despite its disclaimer, Raytheon relied
 solely on limitations within claims 1 and 15—i.e., the
 claimed power density range—to argue the patentability of
 dependent claims 3 and 16 over Knip. 4 See, e.g., J.A. 4804.
     Raytheon made two main arguments to the Board in
 support of claims 3 and 16’s patentability. First, it argued
 that GE’s expert employed a flawed methodology in deriv-
 ing the power density of Knip’s advanced engine from the
 parameters that Knip disclosed. See id. Second, Raytheon

     4    Disclaimed claims are treated as if they never ex-
 isted, see Sanofi-Aventis U.S., LLC v. Dr. Reddy’s Labora-
 tories, Inc., 933 F.3d 1367, 1373 (Fed. Cir. 2019), and
 disclaimer does not legally constitute “an admission that
 the subject of the disclaimer appears in the prior art,” Na-
 tional Fruit Products Co., v. C.H. Musselman Co., 8 F.
 Supp. 994, 995 (M.D. Pa. 1934).
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 8                          RAYTHEON TECHNOLOGIES CORP. v.
                                GENERAL ELECTRIC COMPANY

 argued that Knip’s disclosure failed to enable a skilled ar-
 tisan to make the claimed invention. See J.A. 4847–68. Ac-
 cording to Raytheon, the aggressive parameters disclosed
 in Knip, and therefore, its power density, relied on “revolu-
 tionary” materials unavailable as of the priority date of the
 ’751 patent. J.A. 4855–58.
      In response, GE did not dispute that Knip’s contem-
 plated revolutionary materials were unavailable at the
 time the ’751 patent was filed. See J.A. 6442. Nor did GE
 argue that the aggressive parameters disclosed by Knip,
 parameters GE used to calculate power density, were
 achievable through some other means. See J.A. 6440–43.
 Rather, GE argued that the issue of whether Knip enabled
 its advanced engine was “irrelevant” to the “question
 whether a [skilled artisan] reviewing Knip could make the
 [’]751 Patent’s engine (using any already available materi-
 als) without undue experimentation.” See J.A. 6442 (em-
 phasis in original).
                              C
     In its Final Written Decision, the Board determined
 that GE had met its burden of proving that claims 3 and 16
 are unpatentable as obvious. See General Elec. Co. v.
 United Techs. Corp., IPR2018–01442, 2020 WL 859443, at
 *1 (P.T.A.B. Feb. 20, 2020). The Board treated enablement
 as a threshold issue, recognizing that it “could be disposi-
 tive of any analysis based on Knip in this proceeding.” Id.
 at *6. The Board ultimately concluded that Knip was “en-
 abling,” see id. at *10, because it provided enough infor-
 mation to allow a skilled artisan to “determine a power
 density as defined in claim 1, and within the range pro-
 scribed in claim 1,” id. at *29.
     Having found Knip “enabling,” the Board concluded
 that Knip rendered claims 3 and 16 obvious to a skilled ar-
 tisan. See id. at *29–30. Like its enablement analysis, the
 Board’s overall conclusion focused on the narrow question
 of whether Knip provided enough disclosure to enable a
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 RAYTHEON TECHNOLOGIES CORP.      v.                           9
 GENERAL ELECTRIC COMPANY

 skilled artisan to calculate what would be the power den-
 sity of Knip’s advanced engine. See id. at *29 (“We credit
 [GE’s expert’s] analysis [], which showed persuasively that
 [a skilled artisan] would have used the engine cycle and
 turbine volume measurement parameters expressly pro-
 vided in Knip, along with certain reasonable assumptions
 and estimates as to missing parameters, and obtained
 SLTO thrusts resulting in values within the claimed range
 as set forth in claim 1.”). The Board further supported its
 obviousness conclusion in view of Knip by concluding that,
 even if Knip’s power density did not fall within the claimed
 power density range, power density is a result-effective
 variable. See id. at *23–27.
    Raytheon appealed to this court. We have jurisdiction
 under 28 U.S.C. § 1295(a)(4)(A).
                         DISCUSSION
      Raytheon’s appeal presents a single issue: whether the
 Board erred in finding Knip “enabling” of the claimed in-
 vention. According to Raytheon, the Board improperly fo-
 cused only on whether Knip enables a skilled artisan to
 calculate the power density of Knip’s contemplated, futur-
 istic engine, rather than also considering whether Knip en-
 ables a skilled artisan to make the claimed invention.
 Raytheon argues that, when viewed under the proper legal
 standard, nothing in the record demonstrates that Knip en-
 ables a skilled artisan to make the claimed invention. We
 agree.
                              A
      “Whether a prior art reference is enabling is a question
 of law based upon underlying factual findings.” Minn. Min-
 ing & Mfg. Co. v. Chemque, Inc., 303 F.3d 1294, 1301 (Fed.
 Cir. 2002). We review the Board’s legal conclusions de novo
 and its underlying factual determinations for substantial
 evidence. See In re Gartside, 203 F.3d 1305, 1316 (Fed. Cir.
 2000).
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 10                          RAYTHEON TECHNOLOGIES CORP. v.
                                 GENERAL ELECTRIC COMPANY

      To render a claim obvious, the prior art, taken as a
 whole, must enable a skilled artisan to make and use the
 claimed invention. See In re Kumar, 418 F.3d 1361, 1368
 (Fed. Cir. 2005). In general, a prior art reference asserted
 under § 103 does not necessarily have to enable its own dis-
 closure, i.e., be “self-enabling,” to be relevant to the obvi-
 ousness inquiry. See Symbol Techs., Inc. v. Opticon, Inc.,
 935 F.2d 1569, 1578 (Fed. Cir. 1991) (“While a reference
 must enable someone to practice the invention in order to
 anticipate under § 102(b), a non-enabling reference may
 qualify as prior art for the purpose of determining obvious-
 ness under § 103.”); Beckman Instruments Inc. v. LKB
 Produkter AB, 892 F.2d 1547, 1551 (Fed. Cir. 1989) (“Even
 if a reference discloses an inoperative device, it is prior art
 for all that it teaches.”). For example, a reference that does
 not provide an enabling disclosure for a particular claim
 limitation may nonetheless furnish the motivation to com-
 bine, and be combined with, another reference in which
 that limitation is enabled. See Apple Inc. v. Int’l Trade
 Comm’n, 725 F.3d 1356, 1365–66 (Fed. Cir. 2013). Alter-
 natively, such a reference may be used to supply claim ele-
 ments enabled by other prior art or evidence of record. See
 Comcast Cable Commc’ns Corp. v. Finisar Corp., 571 F.
 Supp. 2d 1137, 1145 (N.D. Cal. 2008), aff’d sub nom. Com-
 cast Cable Commc’ns, LLC v. Finisar Corp., 319 F. App’x
 916 (Fed. Cir. 2009). 5
      But even though a non-enabling reference can play a
 role in an obviousness analysis, the evidence of record must
 still establish that a skilled artisan could have made the
 claimed invention. As the Sixth Circuit aptly explained:

      5  Comcast presents an example where a prior art ref-
 erence that was not enabled at the time of the publication
 became enabled at a later date through advances in tech-
 nology. See id.
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 RAYTHEON TECHNOLOGIES CORP.     v.                          11
 GENERAL ELECTRIC COMPANY

     The enabling disclosure concept [for a prior art ref-
     erence] is a commonsense factor in making a deter-
     mination of obviousness, for if neither any item of
     prior art, nor the background knowledge of one
     with ordinary skill in the art, would enable one to
     arrive at an invention, that invention would not be
     obvious. But to argue, as does [the patentee], that
     the sufficiency of each prior art teaching must be
     tested under the strict standard requiring an ena-
     bling disclosure is to shift the emphasis from obvi-
     ousness in light of the prior art, taken as a whole,
     to the sufficiency of each prior art teaching sepa-
     rately considered.
 Minn. Mining & Mfg. Co. v. Blume, 684 F.2d 1166, 1173
 n.10 (6th Cir. 1982); see also Beckman, 892 F.2d at 1551
 (citing Minn. Mining with approval).
      In the absence of such other supporting evidence to en-
 able a skilled artisan to make the claimed invention, a
 standalone § 103 reference must enable the portions of its
 disclosure being relied upon. See Ashland Oil, Inc. v. Delta
 Resins & Refractories, Inc., 776 F.2d 281, 297 (Fed. Cir.
 1985) (“The test of whether a particular compound de-
 scribed in the prior art may have been relied upon to show
 that the claimed subject matter at issue would have been
 obvious is whether the prior art provided an enabling dis-
 closure with respect to the disclosed prior art compound.”);
 In re Hoeksema, 399 F.2d 269, 274 (CCPA 1968) (“[I]f the
 prior art of record fails to disclose or render obvious a
 method for making a claimed compound . . . it may not be
 legally concluded that the compound itself is in the posses-
 sion of the public [or obvious].”). In this context the refer-
 ence must necessarily enable the relied-upon portion of its
 own disclosure—the same standard applied to anticipatory
 references. In re Antor Media Corp., 689 F.3d 1282, 1290
 (Fed. Cir. 2012) (“[A] prior art reference need not enable its
 full disclosure; it only needs to enable the portions of its
 disclosure alleged to anticipate the claimed invention.”).
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 12                          RAYTHEON TECHNOLOGIES CORP. v.
                                 GENERAL ELECTRIC COMPANY

                               B
      We agree with Raytheon that the Board legally erred
 in its prior art enablement analysis. Here, the only prior
 art or other evidence GE relied on to establish that one of
 skill in the art would have been able to make a turbofan
 engine with the claimed power density was the Knip refer-
 ence. But rather than determining whether Knip enabled
 a skilled artisan to make and use the claimed invention,
 see Kumar, 418 F.3d at 1368, the Board focused only on
 “whether [a skilled artisan] is provided with sufficient pa-
 rameters in Knip to determine, without undue experimen-
 tation, a power density . . . .” See Gen. Elec., 2020 WL
 859443, at *7. This error propagates throughout the
 Board’s enablement analysis, see id. at *7–10, which fails
 to address whether Knip enables the claimed invention.
     The Board defended its overly cramped inquiry by not-
 ing that the claims at issue do not require the advanced
 materials recited by Knip. See id. at *7. Thus, according
 to the Board, whether Knip’s advanced engine had been or
 could be implemented “is not the proper consideration.”
 See id. (rejecting Raytheon’s argument that Knip’s ad-
 vanced engine must be “physically achievable based on the
 reference’s disclosure itself”); id. at *9 (“[E]nablement does
 not require that Knip’s advanced engine was actually im-
 plemented.” (citing Beckman, 892 F.2d at 1551)). On ap-
 peal, GE echoes the Board’s statements and goes further,
 claiming that “it is irrelevant whether Knip actually ena-
 bles a [skilled artisan] to build the specific engine contem-
 plated by Knip.” See Appellee’s Br. at 45. That position
 may have carried the day if GE had presented other evi-
 dence to establish that a skilled artisan could have made
 the claimed turbofan engine with the recited power den-
 sity. But no such other evidence was presented.
     Thus, Knip’s self-enablement (or lack thereof) is not
 only relevant to the enablement analysis, in this case it is
 dispositive. GE does not contend that the ’751 patent’s
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 RAYTHEON TECHNOLOGIES CORP.      v.                          13
 GENERAL ELECTRIC COMPANY

 turbofan engine is enabled by other prior art or evidence of
 record. Instead, GE relies solely on Knip’s disclosure. See,
 e.g., Appellee’s Br. at 48, 51. At oral argument, counsel for
 GE asserted that the Board determined, based on GE’s ex-
 pert’s analysis, that Knip’s engine could have been in fact
 “successfully constructed, and therefore is enabled with re-
 spect to the claimed invention.” See Oral Arg. at 27:19–
 29:00 (citing J.A. 42–44, 781). We disagree that the Board
 made such a finding. Moreover, GE neglected to mention
 that what its expert “constructed” was a computer model
 simulation of Knip’s imagined engine, see J.A. 781, not a
 physical working engine. GE’s expert never suggested that
 a skilled artisan could have actually built such an engine.
      In contrast, Raytheon presented extensive, unrebutted
 evidence of non-enablement. Raytheon submitted and re-
 lied on a declaration from Dr. Williams, a professor of ma-
 terials science, detailing the unavailability of the
 revolutionary composite material contemplated by Knip.
 See J.A. 4853–68, 6291–311. Additionally, Raytheon sub-
 mitted evidence that the exceptional temperature and
 pressure parameters cited in Knip had not been achieved
 through other means as of the priority date. See J.A. 4856–
 58 (citing the supplemental declaration of Dr. Spakovsky
 (J.A. 4913–22)). Raytheon’s unrebutted evidence that Knip
 fails to enable a skilled artisan to physically make Knip’s
 advanced engine is conclusive, given that this was the only
 evidence GE presented for why a skilled artisan could
 achieve the claimed power density.
     In sum, we conclude that GE failed to provide an evi-
 dence-based case for how the turbofan engine claimed in
 the ’751 patent having a particular power density is ena-
 bled by Knip’s disclosure. Thus, the Board’s finding that
 Knip is “enabling” is legal error.
                              C
    GE’s back-up argument that the Board’s decision can
 be affirmed on the basis of its result-effective variable
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 14                         RAYTHEON TECHNOLOGIES CORP. v.
                                GENERAL ELECTRIC COMPANY

 finding suffers from the same enablement-based flaw.
 Even if the Board were correct that power density and
 other performance characteristics are variables a skilled
 artisan would want to optimize, GE’s argument is predi-
 cated on a skilled artisan “modify[ing] the thrust and/or
 turbine volume for Knip’s engine to optimize the power
 density.” See J.A. 726. If a skilled artisan cannot make
 Knip’s engine, a skilled artisan necessarily cannot optimize
 its power density.
                        CONCLUSION
     We have considered GE’s remaining arguments and
 find them unpersuasive. For the reasons set forth above,
 we reverse the Board’s decision finding claims 3 and 16 of
 the ’751 patent unpatentable as obvious.
                        REVERSED