Spotlight altimeter calibrator

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BLAC CAT

Recruit
9
6
Jul 16, 2018
VINELAND, ONTARIO
BLAC CAT here. I am a new member and this is my first post. I am on a quest to identify a WW2 artifact/memorabilia that came back to Canada in my father's duffle bag. It must have fallen in by accident because my Dad would never have "organized" it........
What I have is a glass lens measuring 8" in diameter by 1/2 inch thick with triangular concentric rings on the back. On the face at the centre bottom is "LANCASTER" in uppercase embossed.
I have looked at some manuals for the RCAF & RAF Lancaster heavy bomber, in which my father flew as a Navigator/Bomber in 1944-45, to no avail.
I have also tried some research into the "SPOTLIGHT ALTIMETER CALIBRATOR" the name given to the twin spot lamps affixed to the fuselage of the Lancs and aimed so that when the two spots appeared side by side as a figure 8 on the surface of the water of the German dams that were being attacked the bomb aimer knew that the aircraft was precisely at 60 feet. (Can not imagine doing a couple of hundred knots at 60 feet at night.) No pictures to be found.
Any knowledge out there or ideas for search locations?

BLAC CAT is the plate on my XK-8 Jaguar and the Black Cat is also the mascot of my regiment, The Ontario Regiment (RCAC).
 

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As best as I can tell, the forward spotlight would be affixed at the circled location beneath the nose, where the bombing camera would normally be located:



Source: Lincolnshire's Lancaster back home with her new paint work

I couldn't find any shots of the rear spotlight, but here's a depiction of how it would look - it would be located approximated 20ft. aft of the forward spotlight:

Source: Warthunder


And a diagram of how the spotlights worked:




Also see the thread here: Dam Buster Lancaster Spotlights

The OP in that thread has a diagram of the spotlight placement, and further down there is a post with an attachment which shows a picture of the forward spotlight mounted.
 
Thanks YGBSM!!
The size of the protective lexan/plastic cover is when scaled approximately the correct size to fit the lens that I have. I appreciate your research and pics. Had seen the painting of the lights in action on the box previously but not the close up of the tube that housed the lamp and lens.
I believe that my lens is an early version having read that later versions used a clear lens.
Going to keep searching
BLACCAT
 
Yeah, I haven't found any good shots of the rear of a dambuster, excepting some models. I don't trust the models because none of them feature the forward spotlight protrusion - so I'd much prefer an actual photograph for confirmation.

This is the best picture I could find so far:


Source: ww2today.com

For readers of the thread, this is the spotlight projection we're discussing:

Source: the linked ww2aircraft.net thread
 
The pic with the shroud protruding from the aircraft is the best I have yet seen. I am going to contact Coningsby to solicit their input. Where did you find those pics?
BLACCAT
 
A couple more pictures.

Note how the profile of the forward spotlight projection is clearly visible:




Yet the fuselage area below the roundel is very flush, but is also tapered so a light could be canted forward as required:

Source for both: Images of War: 617 Dambuster Squadron at War
 
Here is a better shot. I believe the rear spotlight is in the bottom middle of the fuselage, marked by the square which appears roughly centerline with the wing (see next diagram):



Source: 617 Dambuster Squadron at War


This diagram shows the position of the spotlights as well as their angling - note the rear spotlight is centerline to the wing:


Source: The Men Who Breached the Dams

The only model I found which got the forward spotlight correct:

Source: http://s3.zetaboards.com/locate_and_cement/topic/7639021/1/



EDIT: bonus "twofer" shot - King George VI greeting the crew AND the forward spotlight clearly visible:

Source: 617 Dambusters at War
 
Thanx for the source info and the pics! Will look up the source.
Thanx for your help. Going to also talk to Canadian Warbirds Heritage Museum home of the only other still flying Lancaster which is about 30 minutes from my place. (I still run outside every time I hear the Merlins but have managed to curtail my girlish squeals of delight....)
BLACCAT
 
Everything indicates that the lens I have is in fact an altitude spotlight calibrator lens. Now I need to find a photo of the real thing.
BLACCAT
 
I found an actual photo of the spotlight... but it still doesn't show the lens. You might consider purchasing the book below - the amount of detail it has is incredible (link below).

Interestingly, it shows the rear spotlight further aft where the belly turret would normally be. I'm not sure if one or the other location is incorrect OR if perhaps the modified Lancasters had some variation to them?



It's the only source I've seen so far which actually shows a close-up of a spotlight. Apparently they were standard Aldis signalling lamps which were modified with a tube shroud to minimize their visibility by German flak positions.

Source for both: Dambuster Lancaster - The definite illustrated guide to the Avro Lancaster BIII Type 464

My sense of scale could be off, but it also seems like these Aldis lamps were of a smaller diameter than 8". The landing lights could be another candidate to consider.

This letter from the manufacturer I found on the forums also seems to confirm the earlier positioning of the rear lamp:


I've also seen two measurements between the spotlights thrown around - 20 feet and 35 feet. That could lend further credibility to the hypothesis that the rear lamp was mounted in two locations across the various modified Lancasters.
 
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