Menasco “Pirate” C4 / D4 — Primary-Source Engine Documentation Archive

Born from a Golden Age of aviation engineering and forged under the pressure of wartime necessity, the Menasco “Pirate” series of inverted inline air-cooled engines represents one of the most elegant powerplant solutions of the 1930s. Conceived by Al Menasco at John Northrop’s request, these engines powered some of the most celebrated American light aircraft of their era — from Ryan trainers to Golden Age air racers. Fewer than 600 were ever built. The factory documentation that survives them is rarer still.

This archive preserves the primary-source engine handbooks and service bulletins for the Menasco C4, C4S, and D4 “Pirate” / “Super Pirate” series in their original factory form.

Document Manifest

• Engine Handbook for Menasco “Pirate” Model C4 Aircraft Engine — Menasco Manufacturing Company, 6714 McKinley Avenue, Los Angeles, California. Bill Rhode Aeronautical Collection copy. Stamped: 10% price increase effective June 1st, 1937.
• Engine Handbook for Menasco “Super Pirate” Model D4 Aircraft Engine — Menasco Manufacturing Company, 805 So. San Fernando Blvd., Burbank, California (two archival copies preserved)
• Service Bulletins for Menasco Engines — Models C4, C4S and D4 — Registered Copy No. 191; Menasco Manufacturing Company, 805 E. San Fernando Road, Burbank, California

Historical Background

The Menasco “Pirate” series traces its origins to Al Menasco’s early experiments converting surplus WWI Salmson Z-9 radial engines into air-cooled units. At John Northrop’s request, Menasco pioneered a clean-sheet inverted inline air-cooled design — a configuration that elevated the crankshaft line, allowing larger propellers without the weight penalty of tall landing gear, and dramatically improving forward visibility for the pilot.

• First certification: A4 certified May 1930; refined C4 certified January 1931
• Manufacturer: Menasco Motors Company (later Menasco Manufacturing Company), Burbank, California
• Production run: 1930–1941 — approximately 500–600 total units across the 4-cylinder line
• Wartime production: Exactly 136 D4 engines contracted for Canadian de Havilland DH.82C Tiger Moths (“Menasco Moths”), built as insurance against potential Blitz disruption to British Gipsy engine supply
• Post-war: Menasco entirely shifted to aircraft landing gear manufacture for WWII; engine production never resumed

Primary Aircraft Applications

• Military: Ryan PT-16 / PT-20 primary trainers; Canadian de Havilland DH.82C Tiger Moth (“Menasco Moth”)
• Civilian: Ryan ST / STA series; Great Lakes biplanes; Northrop Avion EX-1; Golden Age air racers including Steve Wittman’s Chief Oshkosh

Key Variants

• C4: Naturally aspirated base model — 125 hp
• C4S: Supercharged variant with integrated centrifugal supercharger — 150 hp standard; 200+ hp in racing configuration
• D4 (D4-87): Refined wartime variant with upgraded cylinder cooling — 134 hp; built to Canadian deployment specifications

Technical Specifications

Current Status

A small number of Menasco-powered aircraft remain airworthy today — primarily restored Ryan ST and Ryan STA examples, alongside a tiny handful of de Havilland DH.82C “Menasco Moths.” The FAA maintains historic Airworthiness Directives covering crankcase crack inspections, accessory drives, and cylinder head assemblies. The Type Certificate lineage passes through UTC / Collins Aerospace (via Goodrich), though all practical parts and maintenance support is handled exclusively by specialist vintage aviation restoration shops.

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