Lyman,
Perhaps a review of what the STC process is and how it is granted, or not, would be helpful. Don't confuse it with a patent application or patent issuance, they are two different subjects. An STC may often be not patentable but useful for installation on an aircraft. Conversely, a patented item or idea, although deemed valid, may not be determined useful enough to warrant installation. It is as simple as that, don't try to merge or confuse the two...
From the FAA:
STC process - major steps, as required
Applicant applies for STC
Familiarization and preliminary type certification board (TCB) meetings
FAA develops certification program plan
Establishment of certification basis by FAA
Applicant submits data for approval
FAA design evaluation
FAA and applicant hold specialists and interim type certification meetings, as required
FAA performs conformity inspections
Engineering compliance determinations
Pre-flight TCB Meeting
Applicant performs ground inspections, ground tests, and flight tests
FAA reviews manufacturer's flight test results and issues TIA
FAA performs conformity inspections, witnesses tests, performs official certification flight tests and flight standards evaluations
Functional and reliability testing
FAA approves flight manual supplement or supplemental flight manual and holds final TCB meeting
AEG completes continuing airworthiness determination
FAA issues STC
An STC will be issued only if:
the pertinent technical data have been examined and found satisfactory,
all necessary tests and compliance inspections have been completed, and
the alteration has been found to conform with the technical data.&
An STC will not be issued to:
approve minor changes, or for approval of identical replacement parts, unless the installation of such parts constitutes a major change to the type design
approve design changes to Technical Standard Order (TSO) approved articles unless the TSO is invalidated for the modified article. An STC which modifies a TSO article must provide for installation
combine two or more STCs without additional showing of compliance; or
manufacturers or applicants outside of the U.S., except as provided for in a bilateral agreement.
TD