B-17 CC Additional Material by Robert M Stitt

MKS. III, IV, V and VI A.S.V.
There are no restrictions upon the use of A.S.V. Mks. III, IV, V and VI, and continuous watch by a trained WOP/AG must
be maintained by day and night. In order to ensure maximum efficiency, the Captain of aircraft should carefully organise
a tube watch system to enable operators to be changed at suitable intervals, and so avoid eye fatigue which results in
inefficiency. Watch of the indicator should, when possible, not last more than 45 minutes, when a relief watch must take
over. The operator relinquishing watch should then have a period of at least one hour on some other duty before returning
to A.S.V. watch again.
HEIGHT AT WHICH TO FLY.
The best height at which to fly on an A/S patrol is that which gives the greatest chance of the aircraft surprising the U/
Boat. In conditions of moderate or good visibility, A/S patrols should therefore, be flown as indicated below:-
(i) When there is no cloud or cloud is above 5,000 feet
Patrol height should be 5,000 feet. Pilots may, however, fly higher if they wish, when confident that they can lose
height sufficiently quickly to make an effective attack.
(ii) When clouds are not more than 5/10th below 5,000 feet
Patrol above cloud, but not above 5,000 feet. Aircraft flying above cloud should not normally fly directly over the
cloud tops, but preferably 500 to 1,000 feet above them.
(iii) When clouds are more than 5/10ths below 5,000 feet
Cloud cover to be used to the maximum to give concealment. Aircraft should normally fly as near the cloud base
as possible.
In conditions of low lying haze with good visibility above, U/Boats will have only a limited horizontal view, while their view,
upwards, will be little affected. Aircraft should, under these conditions, fly much lower and at a height calculated to reduce
to the minimum the chances of being sighted, on the assumption that an aircraft flying high will be seen by a U/Boat
sooner than one flying lower.
A/S WEAPONS.
The normal A/S weapons at present in use are the 250 lb. Torpex-filled depth charge and the 600 lb. Anti-Submarine
Bomb.
HEIGHT LIMITATIONS.
The height limitations of these two weapons are as follows:-
Maximum Height Minimum Height
250 lb. Depth Charge 500 feet No limitation.
600 lb. A/S Bomb 5,000 feet 500 feet.
Depth Settings
Pistols, in both the 250 lb. depth charge and the 600 lb. A/S Bomb should be set at the shallowest settings. These are as
follows:-
STICK SPACINGS.
250 lb. D.C. 25 feet.
600 lb. A/S Bomb 35 feet (Set during manufacture).
When dropping a stick of 250 lb. depth charges by eye, the stick spacing to be used is 100 feet, which has been proved
over a period to give the best all-round results.
When using the Mk.II(0)A and Mk.III Low Level Bombsight, stick spacings for the 250 lb. D.C. are to be as follows (as
soon as the necessary computer charts have been issued):-
For sticks of six D.C.s
For sticks of four D.C.s
For sticks of two D.C.s
60 feet
100 feet
100 feet (Distributor to be adjusted so that these are dropped as Nos. 2 and 3 of an
imaginary stick of four).
The 600 lb. A/S Bomb should be employed in conjunction with the Mk.XIV Bombsight, or the Mk.II(0)A or Mk.III Low Level
Bombsights. It has not yet been cleared for stick spacings less than 80 feet and will normally be dropped in sticks of three,
spaced 150 feet.
METHOD OF APPROACH TO ATTACK.
In a low level attack, height must be lost and the approach made in the quickest possible manner. In doing so, however,
the pilot must appreciate:-
(i) Whether, if flying direct to the target, he has time to get the bomb-doors open (when applicable) and to get in all
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