Sunderlands and Leigh Lights

First, a confession. I have already posted this question on a Sunderland Facebook group but with no joy so far.
I have a question about Sunderlands and the Leigh Light. I thought that the Sunderland was not fitted with the LL, at least operationally.
Reading the web page about NZ4115 at MOTAT in New Zealand within the history it refers to Sunderlands (some?) being fitted with the LL which surprised me. I cannot recall any photos of LL-equipped Sunderlands.
The Wiki Sunderland page says it was fitted but without a citation. The Leigh Light Wiki does not mention the Sunderland. I know Wiki is not a primary source
It is often hard to prove a negative. Can anyone point me to evidence that the LL was fitted?
I am mostly interested in WW2 but it could have been a post-war addition and that is something I would probably not know about.
A bit of digging has thrown up the following, all from TNA files. In June 1942 the Sunderland was under consideration for the LL along with Liberators and Fortresses. There are several updates about difficulties with trial installations in Sunderlands. In March 1943 the plans to fit the LL to the Sunderland were cancelled. The December 1944 Coastal Command Review of the year talks about successful use of flares by Sunderlands and states that the flares were supplied to aircraft without LLs. Based on that I think that MOTAT and Wiki are wrong, at least as regards operational use. But happy to be proved wrong by other good sources.

Osprey's Sunderland vs U-Boat explicitly says several times that the Sunderland never had them in service and had to rely on flares (though it only deals with action in and around the Bay of Biscay).

EDIT: for what it's worth the official data sheets give additional, reduced range figures for when a Leigh Light is fitted
EDIT 2: I do notice that the sheets from '42 and before list the LL range figures, but the '43 and later sheets do not

Hi Good stuff. What are the official data sheets?

According to my AP 1556C Vol Sec 4 Chapt 1 for the Mk III Sunderland Leigh lights were not fitted to that model on or before Feb 1946.

I do not have the Vol 1 for the Mk II, IV or V aircraft and there is no mention of the Leigh lights or any other modifications in the Mk I Vol I that I have.

Interesting, thanks.

I don't know for sure what happened with the Leigh Light after the war but all the aircraft using it were side-lined soon after the cessation of hostilities so I imagine it just disappeared. Presumably there was progress with radar blind-bombing?

The "Moments" column is presumably the effect around the centre of gravity?

I don't suppose you have the actual modification documents as well as the list? There are some on bombsights, altimeters and flares that are of interest. Do you know if RAF Hendon hold the modifications notes?

WATU said:

Interesting, thanks.

I don't know for sure what happened with the Leigh Light after the war but all the aircraft using it were side-lined soon after the cessation of hostilities so I imagine it just disappeared. Presumably there was progress with radar blind-bombing?

The "Moments" column is presumably the effect around the centre of gravity?

I don't suppose you have the actual modification documents as well as the list? There are some on bombsights, altimeters and flares that are of interest. Do you know if RAF Hendon hold the modifications notes?

Click to expand...

By the end of WW2 the airborne searchlight was becoming less and less relevant in anti-submarine warfare. By Aug 1944 virtually all U-boats were equipped with a schnorkel and were spending most of their time underwater. On 9 Oct 1944 U-968 left Bergen on what became the longest schnorkelling patrol of WW2. She remained underwater for 68 days travelling around the north of Scotland to its patrol area in the English Channel and then returning to Bergen.

It was difficult for all but the most modern radars of the time to detect a schnorkel head. In all but a flat calm seeing one in at night in a searchlight beam was all but impossible. By late war (1944/45) sonobuoys were becoming more important to the RAF and that trend continued postwar.

The airborne searchlight did make a return with aircraft like the Nimrod, but that was more geared to investigating shipping than subs.

Hi Ewen
In WW2 the light performed two functions. The first was to allow identification of a potential target, e.g. U-boat or fishing boat, and the second allowing a visual sight to be used at night to aim depth charges or A/S bombs. Presumably identification was achieved with flares post-war.
Sonobuoys were certainly the way forward but the design used in WW2 was not much more than a prototype. Combined with an acoustic torpedo it had great potential. However in WW2 the RAF concluded in 1955 that the sonobuoy was not effective. Here is an extract I wrote from the RAF report. (The RAF in the Maritime War Vol 5, Various pages & App VI)

"A review of claimed U-boat locations was done after the war. I have extracted the cases when sonobuoys featured and my summary is as follows:
• There were 32 examples between 3/11/44 and 4/5/45.
• Aircraft from CC, RCAF and USN were involved from a wide range of squadrons.
• Main aircraft type was, predictably, Liberator plus four Sunderlands and three Cansos.
• Positive sonobuoys sounds were claimed in 23 cases (72%) with contact lasting as long as three hours.
• Whenever a second aircraft arrived it always picked up positive noises.
• Sounds reported covered relatively slow beats of 55pm, below the taught minimum of 100pm, up
to 250pm accompanied by mechanical banging, hammering, clanking, hydroplane use, etc.
• In all positive 23 cases analysis of U-boat proximity concluded that no U-boats were involved. At least one was close but did not schnorkel that day. In many cases there were no U-boats for 200+ miles.

A bit more evidence. Andrew Hendrie's "The Cinderella Service" has Coastal Command orbats including as at 1/1/44 and 1/4/45. These have lists of squadrons and aircraft types. In each case there are Wellington, Catalina and Liberator squadrons designated as "LL" for Leigh Light. No Sunderland squadrons are noted as "LL".

WATU said:

Interesting, thanks.

I don't know for sure what happened with the Leigh Light after the war but all the aircraft using it were side-lined soon after the cessation of hostilities so I imagine it just disappeared. Presumably there was progress with radar blind-bombing?

The "Moments" column is presumably the effect around the centre of gravity?

I don't suppose you have the actual modification documents as well as the list? There are some on bombsights, altimeters and flares that are of interest. Do you know if RAF Hendon hold the modifications notes?

Click to expand...

No I do not have any of the mods etc but Hendon or the IWM may have some or all of them. And yes Moment is the CofG moment.