Sperry Ball Turret for Avro Lancaster?

No I don't think it was. There was no mention of additional electrical kit being installed just that it was impractical.

You're quite right, I've just checked my copy of 'The Aircraft of 100 Group', by Martin Streetley, my original comment being 'off the top of my head'.
The 'Jostle' transmitter, a very large cylindrical unit, was mounted in the bomb bay of the B-17s so fitted.
Tests carried out in June 1944, showed that the ball turret installation 'was of little value in night combat' and, when the aircraft reached the operational units, having passed through Scottish Aviation at Prestwick, where modifications and RCM equipment fit were carried out, the ball turrets were removed.
On the 'G' variant, 85 of which were supplied to the RAF, the turret well was plated over.
Depending on the internal RCM equipment fit of the 100 Group aircraft, the area was used to mount other equipment as required.
It was the B-24s used by 100 Group which had the 'Jostle' transmitter in the ball turret position, with the aperture blanked off.

lordish said:

Does anyone know if AVROs ever did any testing of adding an American Sperry Ball type ventral turret to the Lancaster? Eventually a Martin mid upper turret was adopted.

Considering that the periscopic ventral turret was a failure the manned Sperry turret would seem to be an obvious choice. It certainly would have been a surprise to your jaded German Ju88G6 pilot.

lordish

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Yes early Lancasters had a ventral turret with a periscope sighting system but it was difficult to use and with no significant night fighter threat early on, it was dispensed with. Unfortunately with the appearance in 1943 of German aircraft fitted with Schrage Musik upward firing cannons, the lack of ventral armament was something that was regretted once the RAF figured out how they were losing so many aircraft but by then the H2S cupola was being fitted and there was nowhere to fit a ventral turret.

Waynos said:

One of the Dambuster's Lancasters had a lashed up ventral machine gun position. There was a documentary on TV recently where the wreck was excavated and was identified positively because they found this gun mount. It seems it was unique.

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I guess it didn't help them...

Capt. Vick said:

I guess it didn't help them...

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Not much use at low level either.

RAF issues with the Sperry ball turret included internal reflections hampering night vision, gunner battle degradation at -40 degrees in a very cramped position, generally poor night vision generally and the provision of enough electrical power.

Combined with these was the sheer weight of the whole package and the extra framing to take the point load where the turret hung with the additional lateral and vertical loads of it in battle manoeuvres. It was not a field modification but a major production line alteration.

A cultural difference was that the USAAF measured in missions. Bomber Command in tons carried. Using a Sperry ball turret meant the loss of some bomb load or restriction of range. This needed to be made up by additional sorties so the losses saved by such a turret might well be balanced by the losses incurred amongst the extra flights. In the long term a remote set of upper and lower turrets were in development.

There was also the resultant loss of H2S radar which fitted in the same hole. It was a bomb multiplier by allowing more accurate bombing so it's loss again meant more bombs would have to be carried to Germany for the same effect, by additional aircraft which would be themselves subject to losses.

I think that this turret was the right answer to the US needs but the wrong one for Bomber Command. WW2 bomber aircrew I have spoken with commonly felt that gunners were principally there to observe and give warning to the extent that a few had strict instructions not to fire as it might give the location away (in one case' unless he is close enough to throw the ..*! guns at him'. They generally felt that a swift tight corkscrew would be more likely to save the crew at night. Of course Village Inn radar made a difference to that view when fitted. Some differed and felt that visible gunfire would make the night fighter break away and find an easier target.

In early 1944 Bomber Command reminded all Groups that.
"To teach crews that their primary defence is in the use of their guns is wrong."
This followed a comparison of losses between various Groups which showed that 5 Group, which interpreted the rules of engagement more aggressively, opening fire on unidentified aircraft not only suffered more 'friendly' fire incidents but also attracted the attention of German night fighters. 1 Group might be a little more aggressive, opening fire on identified targets, but 5 Group whose gunners 'seem to shoot with abandon at everything that comes their way' should be impressed with the importance of positive identification before firing an initial burst.
The point is that, operating at night, stealth in the darkness and, if necessary, evasive manoeuvres were the best defence. Firing weapons, from any position could serve to increase self inflicted losses and always gave away the position of the bomber opening fire. The best defence the bombers had was the Mk I eyeballs of their crews, adding a ventral turret, with all the penalties that would incur, was not a solution, many of the reasons have been given in a post above.

The Manchester did start life with a retractable F.N.21 A ventral turret, but it did not have a dorsal turret. Early Lancaster prototypes and early production aircraft used for trials had various configurations. For example, L7527 had both a dorsal and ventral turret, but one of the recommendations made by the A&AEE during trials was for the deletion of the ventral turret 'being of no practical use' in night time operations. Contrary to the assertion made above (years ago) service Lancasters never had a ventral turret.

Cheers

Steve

stona said:

service Lancasters never had a ventral turret.

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I thought the BMkIIs were delivered with ventral turrets were they removed before service.

fastmongrel said:

I thought the BMkIIs were delivered with ventral turrets were they removed before service.

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Mmm, I'll check when I get a chance.
I replied mostly from memory, only looking up the serial of the trials aircraft mentioned.
Cheers
Steve

stona said:

Mmm, I'll check when I get a chance.
I replied mostly from memory, only looking up the serial of the trials aircraft mentioned.
Cheers
Steve

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It was something I read a while ago so could be out of date info.

Found this photo whilst looking for Lancaster ventral turrets. A Wellington with the Dustbin turret lowered it must have knocked a lot off the cruising speed.

I have found some evidence that about the first 40 Mk Is (Manchester conversions) were factory fitted with the ventral turret. I can't find much evidence of it in pictures of these aircraft at the first Lancaster squadrons (Just one picture which might show one, they are not always easy to see when retracted), so I suspect it was removed, as recommended by the A&AEE.

I have found pictures of some Mk IIs with both the ventral turret and bulged bomb bay doors fitted, so some at least retained this turret for a while.

The turret ring fitted between frames 24 and 27 (25 and 26 being cut away to fit the turret) and this is also where the H2S installation fitted. The turret ring was replaced by the support brackets for the radar scanner. Mason states that the ventral turret was finally deleted with the introduction of H2S, the two being mutually exclusive.

Cheers

Steve

T Bolt said:

That turret was used on some of the early B-24D's. My father used them in training at said they pretty muck su*ked. He said you would get vertigo looking through the periscope and loose all track of where you were looking, not to mention losing your breakfast!

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The lower turret on early B-24Ds was the Bendix, also used on the B-25B through early B-25Gs.