From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specifications for aircraft gun mounting alignment, tolerance, and dispersion.
| Identifier | ExFiles\Box 175\3\ img252 | |
| Date | 1st January 1940 guessed | |
| - 2 - the gun positions to be checked for conformity with the drawings. 4. In the case of aircraft equipped with only one fixed gun, the gun mounting is to be non-adjustable and its alignment to correspond with that specified in para. 2. The actual alignment is subject to a tolerance of +- 1/4° horizontally and vertically from the nominal alignment shown on the drawings. The datum alignment in elevation in this case must be such that at the outer limit of the tolerance the alignment remains within the limits specified in para. 2. 5. In the case of aircraft equipped with two or more fixed guns, the mountings are to be provided with means of adjustment of the gun alignment. The dispersion requirement of para. 1 (b) is that each gun shall be capable of adjustment over a range of at least 1° in all directions from the datum alignment. 6. The actual range of adjustment provided in the gun mountings must exceed that specified in para. 5 by the amount necessary to cover manufacturing tolerances in the positions of the mountings. 7. In allowing for this range of movement, adequate clearance of the guns from possible obstructions, (e.g. blast tubes, and proper relationship of associated equipment (e.g. ammunition boxes), must be taken into account. 8. Fulfilment of the above requirements will meet the essential need of provision for obtaining a dispersion pattern of the gun barrel centre lines of any diameter up to 2° at 400 yards range. Where the provision of the full range of 2° for each gun involves serious difficulty, however, consideration will be given to alternative proposals for obtaining the required dispersion, e.g. by arranging for some of the guns to cover only a selected portion of the total dispersion, thereby reducing the range of adjustment necessary on these guns. | ||