Spitfire Mk I Pilots Operating Notes, dated
June 1940:
This is an Inspection and Test Certificate for a specific aircraft with a Merlin Mk III engine. Inspection and Test Certificate is probably the same as an FAA Form 337 allowing major modification for research or testing purposes. Note the document clears a
single aircraft by serial number on 28 February 1940. The July of 1940 Spitfire Mk II manual clears the Merlin III engine for use of 100 Octane fuel and notes +12lbs may be used.
That is not the Spitfire Mk I but rather the Spitfire Mk II. There is nothing authorizing the Spitfire Mk I to use +12lbs in any of the Operating Notes.
