McCauley GCM, HCM and PCM Propellers: Cessna 150L and Reims F150L
McCauley 1A101/GCM6948, 1A101/HCM6948 and 1A101/PCM6948 appear in overlapping Cessna 150L and Reims F150L application records. They should be researched together because the main question is which exact design and model-year combination a record describes. The common 6948 suffix does not make the GCM, HCM and PCM identities interchangeable.
The U.S. and Reims year ranges differ
The retained U.S. 150L entries list GCM for 1971-1973, HCM for 1972-1974 and PCM for 1974. The Reims F150L entries list GCM for 1971-1973, HCM for 1973-1974 and PCM for 1974. The HCM difference is small in a broad family overview but important when researching a particular year's application.
| Reference family | Origin | Aircraft Model | Model Year / Config | Engine | Exact Propeller Application | Max Dia | Min Dia | Static Min | Static Max | Notes | Primary Authority | Manufacturer Cross-check |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cessna 150 | USA | 150L | 1971-1973 | O-200-A | 1A101/GCM6948 | 69 | 67 | 2500 | 2600 | - | [1] | [2] |
| Cessna 150 | USA | 150L | 1972-1974 | O-200-A | 1A101/HCM6948 | 69 | 67 | 2500 | 2600 | - | [1] | [2] |
| Cessna 150 | USA | 150L | 1974 | O-200-A | 1A101/PCM6948 | 69 | 67 | 2500 | 2600 | - | [1] | [2] |
| Cessna 150 | USA | A150L | 1971-1973 | O-200-A | 1A101/GCM6948 / 1A101/HCM6948 | 69 | 67 | 2500 | 2600 | - | [1] | [2] |
| Cessna 150 | France | F150L | 1971-1973 | O-200-A | 1A101/GCM6948 | 69 | 67 | 2500 | 2600 | - | [3] | [2] |
| Cessna 150 | France | F150L | 1973-1974 | O-200-A | 1A101/HCM6948 | 69 | 67 | 2500 | 2600 | Different from U.S. year effectivity. | [3] | [2] |
| Cessna 150 | France | F150L | 1974 | O-200-A | 1A101/PCM6948 | 69 | 67 | 2500 | 2600 | - | [3] | [2] |
| Cessna 150 | France | FA150L | 1971-1973 base | O-200-A | 1A101/GCM6948 / 1A101/HCM6948 | 69 | 67 | 2500 | 2600 | If FRA kits installed, use FRA configuration. | [3] | [2] |
The table retains origin, aircraft model, year or configuration, engine, diameter limits, static-RPM limits and both source relationships. An overlapping year range describes listed applications; it does not establish which propeller was delivered on a particular aircraft or which one is installed now.
Why the complete designation matters
A logbook shorthand such as “McCauley 69 inch” omits the design identity needed to choose the correct application row. Preserve the full propeller designation from the available equipment and maintenance records. Then compare that identity with the aircraft model and the approval context, rather than choosing a row because its diameter looks plausible.
The listed limits are application evidence, not permission to alter pitch or diameter. Repair and alteration decisions require the applicable approved instructions and the actual propeller's condition and history. This guide does not infer present serviceability from a numerical match.
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Aerobat and FRA qualifications
The combined GCM/HCM row for base FA150L carries a condition directing FRA-kit configurations to their own application. That qualifier must remain visible. A base FA150L reference is not a substitute for the FRA propeller record when the applicable conversion evidence establishes the different configuration.
The Reims modification guide explains why eligibility, installed equipment and approval scope need separate evidence. This distinction is especially useful when an aircraft's records alternate between abbreviated FA and FRA descriptions.
Related 150L and 150M applications
Overlapping application years mean that the model year cannot select a unique propeller by itself. The complete component identity and its installation evidence must resolve which application is relevant to the aircraft. The 150L-versus-150M comparison supplies the wider model transition, while the OCM6948 reference explains another application branch. None of those relationships establishes current manufacturer support, stock availability or a replacement recommendation; those claims are outside the retained installation evidence.
Use the F150L model reference to retain the French model-year and handbook context alongside the differing HCM application years.
Comparing an alternative application
GCM, HCM and PCM entries answer a real application question because their model-year scopes overlap; that overlap is not a statement that every listed propeller is interchangeable on every aircraft in the group. The 150K-to-150L comparison places these designations in the later 150 generation. Compare the full designation, aircraft model, year and stated diameter/static-RPM conditions together, then reconcile the actual installation with its approval and work records. The static-RPM guide explains why selecting a favorable endpoint from a different application would produce a misleading comparison.