In Raytheon Technologies Corp. v. General Electric Co., 2021 U.S. App. LEXIS 10961 (Fed. Cir., Apr. 16, 2021), the Federal Circuit (Judges Chen, Lourie, and Hughes) reversed the PTAB’s Final Written Decision that certain challenged claims of Raytheon’s U.S. Patent No. 9,695,751 (“the ’751 patent”) would have been unpatentable as obvious. The Federal Circuit held that the relied-upon prior art failed to enable one of ordinary skill to make and use the claimed invention.


Raytheon’s patent is directed to gas turbine engines and recites a “’power density’ range.” The claims read, in relevant part:

  1. A gas turbine engine comprising:a fan including a plurality of fan blades . . . ; a compressor section; a combustor in fluid communication with the compressor section; 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; anda 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 between 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 (emphasis added).
  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 (emphasis added).

Claim 15 is substantively identical to claim 1 but requires the speed change system to have “a gear reduction.” Claim 16 depends from claim 15 and contains the same additional limitation as claim 3.

GE petitioned for inter partes review (“IPR”) of several claims of the ’751 patent. After institution, Raytheon disclaimed certain challenged claims, leaving only two claims at issue: claims 3 and 16. Only one asserted prior art reference, Knip, related to the remaining claims.

GE argued that Knip disclosed “performance parameters of a kind that would permit a skilled artisan to derive the power density of their respective engines from those disclosed parameters.” Id. at *7. It would have been obvious, according to GE, “to modify the thrust and/or turbine volume for Knip’s engine to optimize the power density.” Id. at *7-8.

“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.” Id. at *8. According to Raytheon, Knip’s disclosure did not enable the skilled artisan to make the claimed invention because “the aggressive parameters disclosed in Knip, and therefore, its power density, relied on ‘revolutionary’ materials unavailable as of the priority date of the ’751 patent.” Id. at *8-9.

GE did not substantively argue that Knip was enabling, or that the materials therein were available at the time the ’751 patent was filed. GE only argued that whether Knip was enabling was “’irrelevant’ to the ‘question whether a [skilled artisan] reviewing Knip could make the [’]751 Patent[’s] engine (using any already available materials) without undue experimentation.’” Id. at *9 (emphasis in original).

PTAB Decision

The PTAB agreed with GE, finding that claims 3 and 16 were unpatentable as obvious in view of Knip. First, the PTAB determined that Knip was enabling “because it provided enough information to allow a skilled artisan to ‘determine a power density as defined in claim 1, and within the range proscribed in claim 1[.]’” Id. at *9–10. Having found Knip to be enabled, the PTAB concluded that Knip rendered the challenged claims obvious, because “Knip provided enough disclosure to enable a skilled artisan to calculate what would be the power density of Knip’s advanced engine.” Id. at *10. Alternatively, “even if Knip’s power density did not fall within the claimed power density range, power density is a result-effective variable.” Id.

Federal Circuit Decision

On appeal, the Federal Circuit reversed. The Court framed the issue broadly as determining “when a reference needs to have a self-enabling disclosure for supporting an obviousness case.” Id. at *2.

As background, the Court elaborated:

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 evidence of what was known at the time of invention establishes 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 evidence would have enabled a skilled artisan to make the claimed invention, then the invention cannot be said to have been obvious.


In this case, there was no evidence of record to establish that the skilled artisan could have used Knip to make the claimed invention. So, to be effective in rendering unpatentable the challenged claims, Knip had to be “self-enabling” for the portions of its disclosure relied upon for obviousness. Id. at *14.

Raytheon successfully submitted unrebutted evidence of non-enablement. Raytheon’s evidence established that Knip’s disclosure was based on nonexistent composite materials, and that Knip’s invention had not been achieved through other means as of the priority date. For its part, GE presented no evidence to establish that the skilled artisan could have made the claimed turbofan engine with the recited power density.

The Federal Circuit thus held that the Board committed error by finding Knip to have been enabled. Moreover, the Court held, “[i]f a skilled artisan cannot make Knip’s engine, a skilled artisan necessarily cannot optimize its power density.” Id. at *17.

In the Court’s view, “Knip’s self-enablement (or lack thereof) … is dispositive.” Id. at *15. In sum, the Federal Circuit reversed the PTAB’s conclusion of obviousness because the relied-upon prior art failed to enable a skilled artisan to make and use the claimed invention.


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 (Fed. Cir. 2005). Id. at *11. Practitioners should note that without any supporting evidence, a reference itself may need to be “self-enabling” to be effective. Careful analysis of potential references prior to filing or during prosecution may reveal disqualifying weaknesses.