Use of anti-submarine bombs to attack surface vessels

[Rob Stuart]

Greeting from Ottawa,

On 9 April 1942, the 11 Sqn Blenheims which took off from Colombo to attack the Japanese fleet operating off Ceylon (now Sri Lanka) carried a mixed bombload consisting of 15 x 500lb Semi-Armour Piercing (SAP) bombs and 14 x 250lb Anti-Submarine (AS) bombs. A participant stated in 1945 that the AS bombs were carried due to a shortage of SAP bombs. This seems the most likely explanation, but I'm wondering if there were any other instances, on other occasions, of aircraft being armed with AS bombs for attacks on surface ships.

TIA,

Rob

[PNK]

I don't know is the 250lb AS bomb was a depth bomb but if it was set to shallow depths a near miss may have been more effective that a 500lb SAP. The 'B' bomb was designed to float adjacent to a vessel before detonation but although this was used in limited numbers in Europe I doubt it would have made it to the eastern theatres.

An interesting subject, so I hope someone can give a definitive answer.

[Rob Stuart]

I don't know is the 250lb AS bomb was a depth bomb but if it was set to shallow depths a near miss may have been more effective that a 500lb SAP. The 'B' bomb was designed to float adjacent to a vessel before detonation but although this was used in limited numbers in Europe I doubt it would have made it to the eastern theatres.

An interesting subject, so I hope someone can give a definitive answer.

The following is based on info from the 1990 book "Bombs Gone, The development and use of British air-dropped weapons from 1912 to the present day", and other sources:

Once the war started in 1939, the three anti-submarine bombs in the British inventory, the 100, 250 and 500 pounders, proved from the get-go to be almost totally ineffective against submarines, and they had to be replaced by naval depth charges hastily converted for use by aircraft. The AS bombs, intended for use against surfaced submarines, carried fuses intended to detonate the charge instantaneously if the bomb struck a submarine, or following a short delay if it near missed and entered the water. Since the explosive charge made up at least 50 per cent of the weight of these bombs, they had little potential to penetrate the deck of an aircraft carrier in the case of a direct hit. As far as detonation alongside a target was concerned, even the 500 lb AS bomb had to explode within about eight feet of a submarine if it was to inflect lethal damage. It is difficult to say from this what damage might have been caused by a 250 lb AS bomb exploding alongside a carrier such as Akagi, with nearly 50 times the displacement of a German Type VII submarine, but “probably not much” seems like a fair answer.

So, to answer your question, a direct hit on a carrier from an AS bomb was definitely likely to do less damage than a direct hit from a SAP bomb of the same size/weight, and I doubt that a near miss from an AS bomb would do any greater damage than a near miss from a comparable SAP bomb. And of course nobody would attempt to secure a near miss in preference to a hit.

[PNK]

Thanks for that Rob. I always forget about the charge to gross weight ratio. It seems AS bombs suffered from the same lack of development as torpedoes, as they too were considered unfit for purpose - but, better than nothing.

[robstitt]

The anti-submarine bomb was unpopular with aircrew as it was prone to skipping and potentially damaging their low-flying aircraft - the skipping characteristic also spoiled the pilot’s aim. This was remedied on air-dropped depth charges by making the front concave so the perimeter dug into the water on contact, arresting the weapon’s forward motion.

Robert