RAF Low Level Bomb Sight Mark III

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Airman 1st Class
Sep 1, 2019
Having seen the computor element in the MOTAT Sunderland it got me wondering about the bombing system. I learned that the main bomb sight sits in the nose - unsurprisingly. The Low Level Bomb Sight Mark III comprises the main box, the computor and the power supply. The computor operator (it was to the right of the co-pilot) has three things to set - height, ground speed and munitions type (e.g. depth charge stick, single bomb, practice bomb). That feeds a setting through to the bomb sight.

I have found the manual at the UK National Archives (AIR10/4995) plus there is a good instructional video on YouTube (search for "low level bomb sight" hosted by Australian War Memorial). I also have a few other TNA files that I confess I have not fully read yet.

What I would like to find out more about is its actual use. Are there any accounts that describe it in action? One account said that while carried by ASW Sunderlands it was often not used as a snap sighting of a U-boat often happened so fast that the bomb-aimer did not have time to get to his position and for the limited set-up to be undertaken. That sounds right. But there must be other cases when, for example, a Sunderland stood off from a surfaced U-boat waiting for it to dive before attacking. The sight would then be usable.
I've written something up on this that I can send you as it applied to the B-17 Fortress aircraft in RAF Coastal Command service. By way of a summary in answer to your question, here's the last three paragraphs:

According to Armament Vol I Bombs And Bombing Equipment, the LLBS Mark III became a standard item of wartime bombing equipment for aircraft used for this type of low-level attack. Substantiating this, a US Navy Department intelligence report dated August 1944 confirms that Fortress IIAs and IIs of 220 Sqn deployed to the Azores were fitted with the
Mk.III bomb sight.
However, as far at the Author is aware, the Mk.III sight was never used in encounters between a Fortress and a U-boat, the depth charge release point being routinely judged by the captain by eye.
As quoted in the book by a former Fortress flight engineer: "Time was of the essence and the aircraft would normally go straight into the attack… so it would be tracking over the target long before the navigator could get into position to use the low-level bombsight. The normal way to drop the depth charges was for the pilot to aim by eye… this was practised using dummy targets at between 50 to 150 feet."

Hope this is helpful.

Hi Robert
Many thanks. I have the TNA file Armament Vol I Bombs And Bombing Equipment which has some good content. It claims that "Late sighting is no deterrent". I'd dispute that and agree with your flight engineer quote. Unless the bomb aimer is already in situ then I cannot see them getting in place in time for a snap attack of a spotted U-boat with the aircraft, banking, diving, etc. It was looking around a Sunderland that got me interested in the bomb sight. For all its size it is not easy to move around in the flight crew area. An alternative scenario is when the plane sees a surfaced U-boat and decides to wait it out to see if the U-boat dives. The bomb aimer could then be in position and ready to use the sight.
I have your Fortress book, which is very good by the way, but had not looked at that as regards bomb sights. I am going to do an article on the sight based on TNA documents primarily but if you can supplement that with any US/Canadian primary sources that would be of great interest.
You're welcome. You can reach me at robstittATbrookhouseDOTbcDOTca and I'll forward what I have.
That is great. I have emailed you.

Many thanks


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