WHEN TO ATTACK AND WHEN NOT TO ATTACK.
30. If the aircraft cannot deliver its attack until after the U/Boat has been
submerged for some time, the question always arises as to whether to attack or whether the D.C.'s should be saved for a probable second and better
opportunity later.
31. The pilot must in these circumstances, always use his own judgment whether to deliver an attack or not; but it is most unlikely that an attack with 250 lb. D.C.'s will be successful if the U/Boat has been submerged for more than 30 seconds at the time of detonation, unless it happens to have been seriously damaged previously.
32. A depth charge attack should not, therefore, usually be made after this
time limit, unless there is conclusive evidence of slow submersion or the
U/Boat is in the pilot's opinion, threatening a convoy or other surface craft,
or unless the attacking aircraft is nearing the end of its sortie. In these
circumstances, an attack may be made with a view to giving the U/Boat at least a bad shaking up, and in the case of a threat to shipping, preventing it
delivering its attack.
33. Owing to the increased lethal range of the 600 lb. A/S bomb and its
slightly deeper depth setting, this weapon has a good chance of being
effective if detonation occurs within 40 seconds of the U/Boat submerging.
When using this bomb, however, alowance must of course, always be made for the increase in time of fall. The time between release from 1,500 feet, for
example, and detonation at 35 feet would be approximately 10 seconds. As a
temporary measure, until sufficient data on which to assess the value of the
600 lb. A/S Bomb, is available, release may be made up to 40 seconds after
U/Boat has submerged.
34. If a U/Boat is sighted and no attack has been made, "baiting tactics" are
to be employed except when the aircraft is proceeding to escort a convoy, in
which case it should continue on its way. For details of "baiting tactics",
see paragraph 48 below.
35. Attacks are not to be made on oil streaks unless specifically ordered.
NUMBER OF DEPTH CHARGES TO BE RELEASED
36. The number of depth charges to be released in any attack must always be left to the discretion of the Captain of the aircraft, according to the total
load carried and other circumstances at the time, but the following is given
as a general guide and should normally be adhered to:-
Aircraft on A/S Patrols or Sweeps -
37. (i) Aircraft carrying six or less depth charges should drop the whole
load in one stick.
(ii) Aircraft carrying more than six depth charges should drop sticks of
six leaving the remainder for subsequent use.
Aircraft on Escort Duty -
38. Aircraft on convoy or other escort duty should drop sticks of four depth
charges, leaving the remainder for subsequent attacks, e.g., an aircraft
carrying a total of six depth charges would drop four in the first attack
leaving two for a possible second attack, and an aircraft carrying twelve
depth charges will thus have sufficient for three attacks.
39. The Captain of the aircraft is, however, always at liberty to drop more
than four depth charges if he considers the chances of a second sighting
unlikely, e.g., when near his P.L.E. If he makes his first U/Boat sighting
when returning to base, he should always drop at least a full stick of six.
40. When a U/Boat is sighted by an aircraft which is en route to escort a
"threatened" convoy, an attack should be delivered only if a Class "A" Target
is presented, i.e., if the U/Boat is on the surface or has submerged for less
than 15 seconds, but not more than 50% of the depth charges, (and in any case a maximum of four) should be expended in these circumstances. When proceeding to a convoy not reported as "threatened", however, a full stick of four depth charges should always be dropped if the chances of a successful attack are considered good.
U/BOATS FIGHTING BACK.
41. It is evident that U/Boat Commanders are now tending, increasingly, to
remain on the surface and fight back with their gun armament when attacked by aircraft. It is in fact, known that they have received orders to adopt these tactics if surprised on the surface, in such a way as to be unable to dive to a safe depth before the aircraft can deliver its attack.
42. When a U/Boat remains on the surface and fires at the attacking aircraft,
the decision as to the method of attack must rest with the Captain of the
aircraft who will take into consideration his armament, the degree of surprise
achieved, the presence or otherwise of A/S surface vessels and the extent to which he is committed to the attack when the U/Boat opens fire. In general, however, he must remember that the primary reason for his existence is, for the time being, to kill U/Boats and that a U/Boat on the surface presents a much better chance of a kill than one submerged. It is no coincidence that recently, by far the larger proportion of certain or probable kills have been U/Boats which stayed on the surface and fought back.
43. It should also be borne in mind that even a big aircraft properly handled
and using its guns well presents a difficult target for the gunners in the
necessarily cramped positions of a U/Boat, which in any sort of a sea is a
very poor gun platform and especially so if the sea is beam-on. While,
therefore, the tactics to be employed must be left to the Captain's judgment
the attack should, whenever possible, be pressed home at once, preferably from dead ahead, making full use of the front guns to kill the U/Boat's gun crews or at least to keep their heads down.
44. If, however, the Captain of aircraft considers the direct form of attack
undesirable, alternative tactics are to circle the U/Boat at such a range as
to bring accurate fire to bear, flying an irregular course with constant
variations in height and firing with as many guns as possible, until the
U/Boat's gunners are disabled or the U/Boat begins to dive; when the aircraft
must be prepared to make an immediate attack. While adopting these tactics, a very careful watch through binoculars shold always be maintained to ensure that the earliest possible warning is received of any intention on the part of the U/Boat to submerge.
ACTION AFTER ATTACK.
45. After carrying out an attack on a U/Boat by day, the aircraft must drop a
marker beside the swirl. By nite the site of the attack is to be marked by
flame float, and whenever practicable, two flame floats should be dropped at
the same time as the depth charges.
46. The aircraft should then keep the area of attack under observation long
enough to observe results and if possible, determine the extent of the damage caused by the attack. Where there are indications, such as wreckage or persisting oil, or air bubbles, that the U/Boat may be forced to re-surface, the aircraft is to remain over the site and maintain position and height best suited for delivering another attack.
47. On other occasions, excepting, of course, when the U/Boat is definitely
sunk, and except when the aircraft is on convoy escort duty, or at night,
"baiting tactics" (see para. 48 below), are to be employed. Aircraft
proceeding en route to escort a convoy should not remain over the site of an
attack for a period longer than fifteen minutes.
BAITING TACTICS
48. In adopting "baiting tactics" the aircraft will set course from the
position of the attack to a distance of at least 30 miles and will remain
outside this range for not less than 30 minutes. The aircraft should then
return to the scene of the attack, taking full advantage of cloud, sun and
weather conditions for concealment, in the hope that the U/Boat will have
again surfaced.
PHOTOGRAPHS
49. Photographs are to be taken whenever possible and duties are to be
allotted as necessary to individual members of the crew prior to take-off.
The most important photographs are those recording the attack. The rear, or mirror camera is to be turned on at least five seconds before the release of the depth charges and must be kept on for a minimum of 15 seconds afterwards, throughout which period the pilot should make no alteration of course.