Butterfly Bomb

SD 2 bomblets were not dropped individually, but were packed into containers holding between 6 and 108 submunitions e.g. the AB 23 SD 2 and AB 250-3 submunition dispensers. The SD 2 submunitions were released after the container was released from the aircraft and had burst open. Because SD 2s were always dropped in groups (never individually) the discovery of one unexploded SD 2 was a reliable indication that others had been dropped nearby. This bomb type was one of the first cluster bombs ever used in combat and it proved to be a highly effective weapon. The bomb containers that carried the SD 2 bomblets and released them in the air were nicknamed the "Devil's Eggs" by Luftwaffe air and ground crew. • Illustration — SD 2 – Closed: fuze is not yet armed. • Illustration — SD 2 – Open: wings have flipped open and screw threads at the base of arming spindle are visible: fuze is now armed.

The SD 2 submunition was a 76 mm long cylinder of cast iron, which was slightly larger in diameter before its wings deployed. A steel cable 121 mm long was attached via a spindle to an aluminium fuze screwed into the fuze pocket in the side of the bomblet. The outer shell was hinged and would flip open as two half-cylinders when it was dropped. Additionally, spring-loaded wings at the ends would flip out. The wings at the end were canted at an angle to the airflow, which turned the spindle (connected to the fuze) counterclockwise as the bomblet fell. After the spindle had revolved approximately 10 times (partially unscrewing itself from the bomb) it released a spring-loaded pin inside the fuze, which fully armed the SD 2 bomb. The wings and arming spindle remained attached to the bomb after the fuze had armed itself, as the bomb descended towards the ground. Butterfly bombs contained the kleine Zündladung 34 (kl. Zdlg. 34/Np with a blasting cap and 7 grams of Nitropenta) booster and the main explosive filling consisting of 225 grams of cast Füllpulver 60/40 (Amatol) explosive. The fragmentation density produced by an SD 2 was 1 fragment per m 2 in 8 meters radius from a ground burst SD 2 bomb; overall, the body of an SD 2 produced about 250 fragments with a mass of over 1 gram and a still greater number of lighter fragments. The fragments were generally lethal to anyone within a radius of 10 m and could inflict serious fragmentation injuries (e.g. deep penetrating eye wounds) as far away as 100 m. Butterfly bombs were usually painted either straw yellow (desert camouflage), or, if fitted with the DoppZ (41) or (41) A fuze, dark green or grey. Butterfly bombs could be fitted with any one of three fuzes, which were made of aluminium and stamped with the model type surrounded by a circle: • 41 fuze – has an external selector switch with two settings. The Zeit (time) setting will detonate the bomb in the air, approximately five seconds after being armed. The "AZ" (Aufschlagzünder - impact) setting triggers detonation when the bomb hits the ground. The fuze is armed if 4 screw threads at the base of the arming spindle are visible. This fuze is highly sensitive to disturbance if the selector switch is set to Zeit and the bomb is unexploded. The particular switch setting of any type 41 fuze is clearly visible on its exterior. • 67 fuze – clockwork time delay. Time of detonation can be set between 5 and 30 minutes after arming itself in the air. This fuze also has an external selector switch for impact detonation. The particular switch setting of any type 67 fuze is clearly visible on its exterior. • 70 fuze – anti-handling device (i.e. booby trap) will trigger detonation if the bomb is moved after impact with the ground. The fuze is armed if three screw threads at the base of the arming spindle are visible. Butterfly bombs in a submunitions container could have a mixture of different fuzes fitted to increase disruption to the target. Additionally, when a single fuze type with two operating functions was fitted (e.g. type 41), bombs in a submunitions container could have either or both possible fuze settings selected by the Luftwaffe ground crew. Fuze variants such as the 41A, 41B, 70B1, 70B2, etc., also existed. These variants were inserted into the fuze pocket via a bayonet fitting (the fuze was held in place via two steel clips) but otherwise functioned identically. As with more modern cluster bombs, it was not considered practical to disarm butterfly bombs which had fully armed themselves but failed to detonate. This was because SD 2 fuzes were deliberately designed to be extremely difficult and dangerous to render safe once they had armed themselves. Instead, the standard render safe procedure for any unexploded SD 2 butterfly bomb was to evacuate the area for at least 30 minutes (in case the bomblet was fitted with a type 67 time delay fuze), then surround it with a ring of sandbags (to contain the explosion) and destroy it in situ by detonating a small explosive charge beside it. Other solutions were to attach a long string to the bomb and tug on it after taking cover, or for bombs in open countryside, shooting at them with a rifle from a safe distance. Not all unexploded SD 2 butterfly bombs still have their wings attached. In some cases the wings have rusted away and fallen off. The SD 2 then resembles a rusty tin can with an aluminium disc (the fuze) in its side, sometimes with a short stub projecting from it. Regardless of age and condition, all unexploded SD 2s remain highly sensitive to disturbance and can easily detonate.