You can freely build on Frank Whittle's Early Jet Engine Design
This patent expired in 1957. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Individual
Patent granted
1939
Expired
1957
Forward citations
50
What this patent covers
The patent describes a propulsion system for aircraft that utilizes a gas turbine to generate thrust. It details a compressor that draws in air, a combustion chamber where fuel is burned to increase the energy of the air, and a turbine that extracts energy from the hot exhaust gases to drive the compressor. The high-velocity exhaust is then expelled through a nozzle to create forward propulsion. This design effectively replaces the traditional piston-and-propeller engine with a continuous flow process.
What is now free to use
All 0 claims of US 2168726 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover turbofan engine designs with high bypass ratios common in modern airliners.
Does not cover specific electronic fuel injection or digital engine control systems.
Does not cover ramjet or scramjet propulsion systems that lack rotating compressor components.
Does not cover modern materials like single-crystal turbine blades or ceramic matrix composites.
Who is building on this today
Major aerospace engine manufacturers like Rolls-Royce, General Electric, and Pratt & Whitney continue to refine the fundamental gas turbine cycle established by Whittle. These companies have evolved the basic architecture into the complex, high-bypass turbofans used in modern commercial aviation.
Products built on expired version of this technology
Gloster E.28/39
Early Whittle W.1 turbojet engines
Foundational design for all modern turbojet engines
How to cite this patent in your documentation
Individual. US Patent 2168726. Propulsion of aircraft and gas turbines. Granted 1939, expired 1957. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.