Introduction

The attack can be seen as the culmination of the work of the costal command. Around 170 man hours were needed to give one hour of flying time and around 200 hours of flying time to give one attack. That attack would then last only a few minutes. It is clear therefore that a huge amount of time and effort is invested in those few minutes. Since the attack only concerned a relatively small number of aircrew and the equipment they were using it was seen as a good way to increase the total number of U-boats sunk. This was shown to be correct by the massive improvement in the success rate for attacks. In 1941 only 2 or 3% of attacks resulted in a sinking, this rose to 40% in 1944 and as high as 60% in the last few months of the war. This also meant that aircraft changed from being simply a moral deterrent to a credible killing weapon against U-boats.

The principal weapon used against U-boats was the depth charge (D.C.) also known as the anti-submarine bomb. This is an explosive dropped by the plane which is either set to explode at a certain depth using a hydrostatic fuse or after a certain time using a time delay fuse. During an attack the plane will drop several bombs equally spaced in a straight line. This is known as a stick with the distance between each D.C. being the stick spacing. The aim is to get the centre of the stick to be on the U-boat's conning tower. This form of attack is affected by several different factors which can be modified to yield a higher success rate. Among these factors the most important were:

• Aiming errors
• Depth setting of D.C.
• Orientation of the stick relative to the U-boat
• Stick spacing
• Explosive charge in the D.C.

Some of these will be discussed in the subsequent sections.