Non-Enabled Futuristic Engine Could Not Invalidate Claimed Turbine Engine

Intellectual Property Law

In Raytheon Technologies Corporation v. General Electric Company,1 the Federal Circuit held that the Patent Trial and Appeal Board (Board) incorrectly invalidated a Raytheon turbine engine patent as obvious based on a three-decade-old paper that attempted to prophetically describe an earlier invention that could not be built. The court noted that a prior art reference used to show obviousness does not need to be self-enabling or enable its own description. However, without supporting evidence of enablement, a reference used to show anticipation or obviousness in federal court must, at minimum, enable the portions of its disclosure being relied upon.

The court initially described the issue in the case as follows:

A typical 35 U.S.C. § 103 obviousness case often turns on whether an asserted prior art reference teaches a particular disputed claim limitation or whether a skilled artisan would have been motivated at the time of invention to combine the teachings of different references. There usually is no dispute about whether an asserted prior art reference 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 reference 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 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.2

Raytheon owned U.S. Patent No. 9,695,751 (the ’751 patent) directed to gas turbine engines, which generate thrust by pulling air into the front of the engine, mixing and burning the pulled air with fuel, and expelling exhaust gases.

The ’751 patent claimed a gas turbine engine with two turbines, fan blades and turbine rotors. The unique feature of the claimed invention was a power density range much higher than that of previous engines. The ’751 patent explained power density as “the ‘sea-level-takeoff thrust’ (SLTO thrust) divided by the engine turbine volume.”

Claims 1–3 recited the following:

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;

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 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.
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.3

GE filed a petition for inter partes review of the ’751 patent based on the prior art reference Knip.

Knip was a 1987 NASA technical memorandum that predicted superior functioning for a fictional turbofan engine using all composite materials—an engine that was impossible at that time and was still impossible at the time of GE’s petition. Though Knip described a number of performance factors for its futuristic engine, it did not describe SLTO thrust, turbine volume or power density.

Raytheon argued that Knip’s disclosure failed to enable one of ordinary skill because its power density feature depended on innovative materials unobtainable as of the priority date of the ’751 patent. GE acknowledged that Knip’s innovative materials were not available at the time of the priority date for the ’751 patent. However, GE maintained that Knip’s enablement was unrelated to whether what Knip disclosed rendered the engine claimed in the ’751 patent unpatentable.

The Board determined that Knip was enabling because it provided a sufficient disclosure to enable one of skill to compute the power density of Knip’s claimed engine. Raytheon appealed, and the Federal Circuit reversed.

On appeal, Raytheon argued the Board improperly focused only on whether Knip enabled calculating the power density of Knip’s futuristic engine, instead of assessing whether Knip enabled the claimed invention. The Federal Circuit agreed.

To render a claim obvious, the prior art, taken as a whole, must enable a skilled artisan to make and use the claimed invention. In general, a prior art reference asserted under § 103 does not necessarily have to enable its own disclosure, i.e., be “self-enabling,” to be relevant to the obviousness inquiry.… For example, a reference that does not provide an enabling disclosure for a particular claim limitation may nonetheless furnish the motivation to combine, and be combined with, another reference in which that limitation is enabled.… Alternatively, such a reference may be used to supply claim elements enabled by other prior art or evidence of record.4

Even though a non-enabling reference can be used to show obviousness, the evidence must still show that one of ordinary skill could have made the claimed invention.

The Federal Circuit explained, however, “In the absence of such other supporting evidence to enable a skilled artisan to make the claimed invention, a standalone § 103 reference must enable the portions of its disclosure being relied upon.”5 According to the court, the prior art “reference must necessarily enable the relied-upon portion of its own disclosure—the same standard applied to anticipatory references.”6

The Federal Circuit agreed with Raytheon that the Board erred because instead of deciding whether Knip enabled the claimed invention, the Board focused only on whether Knip disclosed adequate parameters to determine, without undue experimentation, the power density.

GE further argued that it was irrelevant whether Knip enabled its specific disclosed engine. The court rejected this argument because GE did not provide any evidence to show the claimed turbofan engine could have been made with the claimed power density.

Thus, the court reasoned, “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 turbofan engine is enabled by other prior art or evidence of record. Instead, GE relies solely on Knip’s disclosure.”7 Raytheon, however, submitted extensive proof of non-enablement that was not refuted by GE. “Raytheon submitted and relied on a declaration from Dr. Williams, a professor of materials science, detailing the unavailability of the revolutionary composite material contemplated by Knip.”8

The court explained that “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.”9 Thus, the court determined that GE failed to offer evidence that the turbofan engine claimed in the ’751 patent having a specific power density was enabled by Knip’s description.

With respect to GE’s additional contention that the Board’s verdict based on the result-effective variable outcome was correct, the Federal Circuit disagreed, even if the Board was correct, that the power density and other performance characteristics would have been optimized by one of ordinary skill. The court explained, “If a skilled artisan cannot make Knip’s engine, a skilled artisan necessarily cannot optimize its power density.”10

Thus, holding that the Board’s decision that Knip was enabling was legal error, the court reversed the Board’s ruling that the claims of the ’751 patent would have been obvious.

Key Insights

The law has always been quite muddy and fact-based when a prior art reference is enabled “enough” to be legitimately used in a prior art rejection, and in particular, an obviousness rejection under 35 U.S.C. §103. Raytheon Technologies Corporation v. General Electric Company dealt with what should have been an easy decision—i.e., a prior art reference that prophesized about an invention that was still not proved to exist.

However, the more difficult question of when a prior art reference that is not enabled may be used in a prior art rejection remains an underlying fact-based inquiry used as part of the legal question regarding availability for use in a prior art rejection. The courts arguably have been biased toward permitting at least portions of the non-enabled reference to be used in a prior art rejection. The current decision appears to at least be a bit more realistic in federal court based on the allocation of burdens in litigation. Litigants should be on notice that this decision might breathe more life into arguments that certain prior art cannot be used in an invalidity attack as a result of non-enablement. While the standard is different before the U.S. Patent and Trademark Office, this decision may be sufficient to cause patent examiners to seriously consider arguments regarding patentability during patent prosecution as well.


Irah Donner is a partner in Manatt’s intellectual property practice and is the author of Patent Prosecution: Law, Practice, and Procedure, Eleventh Edition, and Constructing and Deconstructing Patents, Second Edition, both published by Bloomberg Law.


1 Raytheon Techs. Corp. v. Gen. Elec. Co., 993 F.3d 1374, 2021 USPQ2d 434, 2021 WL 1432964 (Fed. Cir. 2021).

2 Id., 993 F.3d at 1376–77.

3 Id., 993 F.3d at 1378 (quoting U.S. Patent No. 9,695,751).

4 Id., 993 F.3d at 1380.

5 Id., 993 F.3d at 1381 (citing Ashland Oil, Inc. v. Delta Resins & Refractories, Inc., 776 F.2d 281, 297, 227 USPQ 657, 667 (Fed. Cir. 1985) (“The test of whether a particular compound described 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 disclosure with respect to the disclosed prior art compound.”); In re Hoeksema, 399 F.2d 269, 274, 158 USPQ 596, 601 (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 possession of the public [or obvious].”)).

6 Id., 993 F.3d at 1381 (quoting In re Antor Media Corp., 689 F.3d 1282, 1290, 103 USPQ2d 1555, 1560 (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.”)).

7 Id., 993 F.3d at 1382.

8 Id., 993 F.3d at 1382.

9 Id., 993 F.3d at 1382.

10 Id., 993 F.3d at 1382.

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