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).
Notes on the alignment and range of adjustment for fixed aircraft guns.
| Identifier | ExFiles\Box 176\1\ img111 | |
| Date | 1st January 1940 | |
| COPY. S E C R E T S.B.853. January, 1940. NOTES ON ALIGNMENT AND RANGE OF ADJUSTMENT OF GUNS. PART I. FIXED GUNS. 1. In aircraft equipped with fixed guns firing nominally in the line of flight, the requirements of gun alignment involve two factors:- (a) The alignment of the centre of the total bullet group relative to the aircraft. (b) The alignment of the guns relative to one another to produce a total bullet group dispersed in a prescribed shape and size of pattern. It is necessary therefore to define a datum alignment of each gun, and a range of possible variation of alignment of each gun, measured from its datum alignment. The requirement (b) applies only to aircraft equipped with two or more fixed guns. 2. The required datum alignment 1(a) is that in which all gun barrel centre lines converge at a point 400 yards ahead of the aircraft, this point being:- (a) As seen in plan, on the aircraft longitudinal axis, (b) As seen in elevation, on a line drawn through the lowest gun and parallel to the horizontal when the aeroplane is in level flight at normal top speed, as defined in A.P.970 (as amended by A.L. No.4) Chapter 1, paragraph 5, with flaps not in use. This angle of elevation may be modified within the limits of + 3° and - 2° if necessary to relieve design difficulty. 3. In order to facilitate subsequent routine adjustment of the guns, the angle of elevation of the designed gun line as chosen in accordance with the requirement of para.2(b) is to be shown on the aircraft drawings relative to the aircraft datum. The drawings are also to show the line of flight when the aeroplane is flying level at normal top speed, as defined in A.P.970 (As amended by A.L. No.4) Chapter 1, paragraph 5, with flaps not in use, and means must be provided for enabling 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 is to correspond with that specified in para.2. The actual alignment is subject to a tolerance of ±¼° 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. | ||