Hi Walter – can you give us an idea of why you think its definately not Lancaster. We would appreciate any feedback and advice because like so many others, we are still learning.

Of course I can! For starters I think we can all agree that as far as four gun tail turrets go, the Lanc started off with the FN20 tail turret, which was then developed into the FN120.

The FN20 was a development of the FN4. Both equipped with 4 x .303 Brownings but the FN4 carried their ammunition supply within the turret (4 x 1000 round containers, two on the left an two on the right side and situated in the “turret drum” in front of the air gunner’s feet, and arranged in a chevron fashion, ie in an angle towards the turret’s centre line). The FN20 was equipped with a servo feed unit and drew its ammo from boxes situated in the rear fuselage of the aircraft. I may be mistaken but I believe those fuselage boxes contained 2500 rounds per gun, in any case substantially more than with the FN4. Using up those 1000 rounds per gun in the FN4 would only take about a minute of continous firing…

Construction wise those two turrets are quite different too. On of the main giveaway’s is that in the FN4 the gun cradles (onto which the guns are mounted) are held in substantial cast brackets, clearly shown in the below drawing out of AP1659A (sorry but can’t seem to get the drawing attached upright:confused:) :

[ATTACH=CONFIG]245788[/ATTACH]

In the FN20 they did away with those cast brackets and the gun cradles were mounted in a very distinctive frame, clearly shown on the below drawing, also out of AP1659A :

[ATTACH=CONFIG]245789[/ATTACH]

Clearly, if you have an FN20 without that frame, you’ve got nothing to support the gun cradles.

And there are more differences of course, the FN4 uses articulated empty shell/link ejection shutes which slide up and down in runners following the upwards/downwards motions of the guns, all very complicated. The FN20 has simple fixed shutes which you can see sticking out below the guns on the above drawing. And the FN20 is a bit more complicated inside as well as the bottom of the turret drum has a non rotating, ie fixed, central portion where the ammo belts enter the turret.

If you compare the FN4 drawing with the turret you acquired, Reevers, you will agree that that is what you have. Great turret though and definitely worth restoring.

As I pointed out to the previous owner in the other thread, the FN4 came in A and B versions, the B not having oxygen supply for the gunner and used on flying boats. If the rotating service joint is still in place on the bottem of the turret then on the B you should only find hydraulic fluid entry and exit points, whereas the A has an oxygen supply pipe in addition.

This is the rotating service joint on the Brussels Army Museum FN4A prior to its restoration, the small diameter pipe at the bottom is the oxygen supply:

[ATTACH=CONFIG]245791[/ATTACH]

With the connection that Australia has with the Sunderland I’m pretty sure it’s an FN4B though.

Do let us know when you manage to look underneath please!

Cheers,

Walter

I’ve studied the FN4 in detail and that is definitely a Nash & Thompson FN4 you have there Tomahawk – great find and please do bring it under cover as suggested by others.

The FN4A was used on Whitley V, Stirling and Manchester aircraft whereas the FN4B was used on the Saro Lerwick and the Short Sunderland, superceding the FN13 on the latter.

Of note is that the FN4 had a specific cupola design for every aircraft type so if you have a “complete” survivor it’s easy to determine which bomber type it was used on. Unfortunately yours is missing quite a few bits 🙁 .

The difference between the FN4A and FN4B is that the latter did not have any provision for oxygen supply. The oxygen supply socket in the FN4A was mounted on a small triangular panel to the air gunner’s left, as seen in below photo from the FN4A in the Brussels Royal Army Museum before its restoration (this is a Whitley turret) :
[ATTACH=CONFIG]245510[/ATTACH]

Obviously the structure this panel was mounted on is missing from your turret. It might be worth having a look under the turret drum to see if the rotating service joint is still present as on the FN4B this will only have hydraulic fluid inlet and outlet openings whereas on the FN4A one would also find an oxygen supply connection tube.

I hope the above is of help and thank you for sharing the photos!

Cheers,

Walter

Happy New Year to you Mike, and to all other forum members of course :)!

I just have to say it again, your CAD work is absolutely brilliant! Sorry I can’t answer your question re how the side bar is fixed to the side of the gun, think we need to call in the help of one of the forum members who have access to a real .303 Browning!

Thanks again for the Air Diagram copy by the way.

Do keep us updated, it’s fascinating to see the virtual gun come together.

Best wishes,

Walter

Looking awfully good Mike – I do envy your CAD skills! – keep up the good work and do keep us posted please.

Cheers,
Walter

Hi James, sorry for taking so long but further to your post #8 – ta for finding that pic of a 5C/803, I was actually expecting something with a flat end for easy mounting like the 5C/492 navigation lamp.

Anyway back to the Blenheim and to answer your question, the Blenheim only carries single formation keeping lamps, the inventory mentioned earlier does not specify the colour but the 5C vocab lists both blue and clear glasses. Of note is that in various AP’s both the terms “formation keeping lamp” and “recognition lamp” are used for the same item. There IS a signalling switchbox 5C/372 in the circuit for the formation keeping lamps.

As you’re “doing” the Stirling I thought it might be interesting to check AP1600A Vol 1 which covers the AVRO Manchester I as they’re both of the same generation (or sort of anyway) and there we see three formation keeping/recognition lamps on each wing tip, colours being red, green and yellow and again ther is a signalling switchbox in the circuit as is something that looks like a selector switch (to choose the colour perhaps?). No lamp type indicated of course.

Anson and Beaufighter also appear to have only single formation keeping lamps so maybe the triple lamps are specific to larger, four-engined aircraft?

Cheers,
Walter

Hi James! How come I do feel lured into this thread!

The lights you are referring to on the Blenheim are the formation keeping lights but I’m afraid that AP1530B (Blenheim Mk IV) only gives the electrical connection scheme and a drawing of the wing tip structure into which the formation and navigation lights are mounted, bar any details of the lights themselves.

However, I have a scanned copy of a Blenheim Mk IV Airframe Inventory book and this tells us that the formation keeping lamps are of the “B” type and bear reference number 5C/803. I have a few photos of RAF lamps but not of a 5C/803 of course but perhaps someone else might provide.

This of course relates to the Blenheim so don’t know of how much relevance it is to the Stirling.

Cheers,
Walter