Accession Number : AD0067410

Title :   The Effect of Yaw upon Penetration; the Effect upon Bullets of Penetrating very Thin Duralumin Sheets; and the Use of Shielding Structures in the Form of Gratings

Descriptive Note : Partial rept. no. 5 on Light Armor


Personal Author(s) : Irwin, George R ; Webster, R A

Full Text :

Report Date : 19 Jun 1939

Pagination or Media Count : 46

Abstract : Three investigations directly related to light armor for aircraft are described in this report: the effect of yaw upon penetration, the effect upon bullets of penetrating very thin Duralumin sheets, and the use of shielding structures in the form of gratings. Data illustrating these topics are still in the process of collection. Methods of these investigations are, however, described and preliminary results of interest are shown. An effect of yaw upon penetration of about 1.4 per cent limit velocity increase per degree yaw was found for samples of 17 ST Duralumin, STS armor plate and hard homogeneous armor. The largest yaw effect was measured using a plate of STS armor hardened to Brinell 370. The smallest measured yaw effect was obtained on a sample of 0.25 inch face-hardened armor. It is shown that apparent differences in plate quality or bullet quality of 50 feet per second in plate testing may be due to several degrees of yaw of the bullets at impact. If armor is spaced back inside the fuselage of an aircraft, bullets may tumble before striking the armor due to penetrating a Duralumin sheet at large obliquity and 23 inches separation on the limit of a typical bullet-proof plate at normal incidence is shown to be more than 200 feet per second. There is a gain in weight efficiency even when the resolved weight of the Duralumin is included with that of the armor plate. The efficiency of a light grating used as the first plate of a divided armor structure depends considerably upon design. Certain design improvements have been ascertained. On account of the very large effectiveness of solid shielding plates, it is still uncertain whether gratings or solid plates are better as first members of a divided armor structure.


Subject Categories : Ammunition and Explosives

Distribution Statement : APPROVED FOR PUBLIC RELEASE