[Test running log for Whittle W.1 engine. Ms. vol., 1941 Apr-May. Prefaced by note 'Whittle Supercharger W1. Manufactured by B.T.-H. Co. Ltd. Rugby & modified & re-assembled by Power Jets, Ltd. at Ladywood Works, Lutterworth'. Covers period Apr 12 to May 30 with details of several tests per day. Each left-hand page bears details of modifications and repairs; each right-hand page includes details re duration of test and reasons for stopping, remarks, faults and defects found on inspection, total running time. The first flight, in a tricycle gear Gloster E.28/39, was on May 15; on May 21 there was a demonstration flight for the Secretary of State for Air et al. See also MS 653 (inv. no. 1946-26/2) test running log for W1X engine]