ADC Cirrus
I-4 piston aircraft engine
The ADC Cirrus is a series of British aero engines manufactured using
surplus Renault parts by the Aircraft Disposal Company (ADC) in the 1920s.
The engines were air-cooled, four-cylinder inline types. They were widely used for private and light aircraft.
Design and development
The Cirrus engine originated in Geoffrey de Havilland's 1924 search for a powerplant suitable for the light two-seat sports biplane which would become the de Havilland Moth. No engine existed at the time with a suitable level of power combined with a low weight. The Aircraft Disposal Company, also known as Airdisco and ADC, were producing the low-cost Airdisco V8 which had been developed by Frank Halford from their large stocks of war surplus Renault V8 aero engines. De Havilland realised that half of this engine would make an air-cooled four-cylinder inline engine of just the right size at low cost. He persuaded Halford to undertake its design and development.
The cylinders, pistons, con-rods and gearing were taken from the Renault, with the valve gear based on the Airdisco, and a new five-bearing crankshaft and cast crankcase were designed. It became the first Cirrus engine, and the first air-cooled four-cylinder inline aero engine to go into quantity production.
Begin with the source’s own compact description: “ADC Cirrus” is i-4 piston aircraft engine. The dossier treats that line as a proposition to test through Cirrus, piston and aircraft, not as a finished interpretation.
Why this record matters
The phrase “i-4 piston aircraft engine” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Apr 30, 2026. The linked authority identifier is Q4651083. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1924.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
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The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “ADC Cirrus”, its source revision and the description used here.
- Expand the search: follow ADC Cirrus primary sources, ADC Cirrus archive and Cirrus research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
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This entry incorporates text from “ADC Cirrus” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.