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British B.1/39 Heavy Bomber Competition

blackkite

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Hi!
https://www.warbirdsforum.com/topic/366-additional-raf-might-have-beens/

"The B1.39 spec was to carry 9,000lb over 2,500miles cruising at least 280mph. Maximum bomb load was to be 10,000lb and some could be carried externally if necessary. Provision was made to stow 20 x 250lb or 500lb bombs, 10 x 1,000lb bombs, 5 x 2,000lb AP bombs, 2 2,000lb SCI containers or 10 small bomb containers. The 20mm cannon were drum fed with 30 rounds per drum, 5 drums per gun and an additional reserve supply of 20 drums per turret was to be carried but not necessarily in the turret. The aircraft was to be stressed to carry alternate turrets with 2 40mm cannon each with 110 rounds of ammunition. Armstrong Whitworth, Blackburn, Bristol, Fairey, Gloster, Handley Page, Avro, Shorts and Vickers all produced designs with Hercules, Griffin or P.24 engines."

Also Bristol 159 is here.
https://www.secretprojects.co.uk/forum/index.php/topic,29457.0.html
Fairey proposal is here.
https://www.secretprojects.co.uk/forum/index.php/topic,5496.msg44089.html#msg44089
 

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Schneiderman

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And this is how a twin 4xHispano cannon turret would function.
 

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Avimimus

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Schneiderman said:
And this is how a twin 4xHispano cannon turret would function.
Ah! That answers my questions!

A mechanical loader and two assistants for a crew of two people per turret! That would compensate for the speed with which ammunition would become exhausted.
 

Hood

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That's an interesting diagram.
The provision of two loaders would push the crew of an RAF 'heavy' to around 9-10 men. I'm guessing the increased firepower was seen as more than compensating the additional weight of ammunition and crew and the consequent reduction in payload.
 

harrier

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A few machine gun bullets from a fighter would also take out the entire defensive capability in one go by killing/injuring the gun crews.
 

JFC Fuller

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Schneiderman, thanks for the photo. That diagram demonstrates one of the three key issues with this scheme:

1) The RAF/UK had yet to develop an acceptable continuous feed system for the Hispano cannon so were forced to use the 20 round drum magazines, the knock-on effect was the need for manual loading arrangements as seen here.

2) The CoG issues associated with such heavy armament/turret arrangements, the entire aircraft had to be designed around them. The RAF apparently preferred the direct over/above configuration shown here but the preferred Bristol design got away with staggering the arrangement.

3) At Kew there are several files that indicate there were severe problems experienced with dispersion resulting from barrel bending as the turret rotated in addition to the drag caused as the turret slewed to either beam

At first glance the quad hispano turret (especially if paired with a gyro gunsight) would have been a remarkable defensive mechanism but the early challenges were substantial.
 

harrier

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The Bristol design might allow only one loader, servicing both turrets. A lot of ammo is shown between them here: https://www.secretprojects.co.uk/forum/index.php/topic,29457.msg314179.html#msg314179

There are two lookouts at the rear though, so crew per turret seems quite high in any case.
 

Foo Fighter

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Harrier said:
A few machine gun bullets from a fighter would also take out the entire defensive capability in one go by killing/injuring the gun crews.
Much like any other system in use at the time.
 

JFC Fuller

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Harrier said:
The Bristol design might allow only one loader, servicing both turrets. A lot of ammo is shown between them here: https://www.secretprojects.co.uk/forum/index.php/topic,29457.msg314179.html#msg314179

There are two lookouts at the rear though, so crew per turret seems quite high in any case.
Suspect it still would have been one loader per turret, the workload would have been pretty high- or at least intense for short bursts.
 

harrier

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Foo Fighter said:
Harrier said:
A few machine gun bullets from a fighter would also take out the entire defensive capability in one go by killing/injuring the gun crews.
Much like any other system in use at the time.
Noes/dorsal/tail turret much less likely to all be knocked out by one quick strafe. Key tenets of aircraft survivability studies; duplicate/triplicate & separate essential things. All eggs literally in one basket with B.1/39.

Also wonder how quickly turrets could align. Assume they thought you could knock 'em down at long range, hence low crossing rates. But once a fighter got close? Need for lookouts also seems curious.
 

harrier

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JFC Fuller said:
Harrier said:
The Bristol design might allow only one loader, servicing both turrets. A lot of ammo is shown between them here: https://www.secretprojects.co.uk/forum/index.php/topic,29457.msg314179.html#msg314179

There are two lookouts at the rear though, so crew per turret seems quite high in any case.
Suspect it still would have been one loader per turret, the workload would have been pretty high- or at least intense for short bursts.
Any idea where the spent cases (and links) went? Intense indeed, and gunners' feet/hot metal whizzing around your head might reduce efficiency of loaders.

ventral guner reminds me of John Fozard's view of prone pilots. "it's a good position, but not for flying!".
 

JFC Fuller

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I suspect the links and cases were to be expelled from the aircraft in some way, probably gravity falling out of hatches in the lower fuselage.

The spotter/gunner coordinator is an odd feature of more than one British design, he makes an appearance in the Albemarle as well. Bomber Command were obsessed with defending against attacks from the rear, many senior officers were convinced that beam attacks were impossible so focus was placed on rearward defence- the design challenge was the center of gravity. As far as I can make out the logic behind the Lancaster's original layout was less about true all-round defence than the ability to point 10 .303s aft (including the soon abandoned under turret).
 

Schneiderman

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JFC Fuller said:
...he makes an appearance in the Albemarle as well.
Ah, it may be an AW thing then as the drawing I posted is from AW's B1/39 submission
 

Tonton-42

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hesham said:
Hi,

here is a proposals from Avro (Model-680),Fairey and Gloster.
Hello !
You go to find me irrelevant and what that adds nothing to the debate, but I find that Fairey looks like a four-engined big Do-17 ! Would it be more than a latest fad in the time ?
@+
Tonton
 

Avimimus

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So assuming all for guns are fired at once (and assuming my calculations are correct) that is 2.77 seconds of fire between reloads. This is similar to the burst length of the 0.303s in British bombers of the time. However, they were belt fed and required cooling, not reloading. So the reload time could have left a considerable period where fire wasn't available. To make matters worse, the gun barrels had set positions during reloading - which means any attacking fighter would have visible cues showing that the gunners were reloading.

So it might be much more ideal to have three two gun turrets (e.g. a tail turret) which would allow one gunner to be operational while the other guns were being reloaded. Doing so would prevent a fighter from safely pressing its attack after the first defensive salvo missed.

That said, this is a really intimidating defensive armament - and a single burst scoring a hit would almost certainly take out the attacker. An interesting side effect is that the Luftwaffe might have invested even more in fighters with larger cannon (37mm or greater) in an attempt to regain a range advantage over the gunners. This would waste funds and might lead to more vulnerable twin engined fighters existing to be shot down in 1944 when long range single-engined escort fighters became more available. Of course, by mid-war both RAF bombers and twin engined Zerstörer would tend to prefer operating at night - and this would mean that engagement ranges would tend to be much closer. So, the actual way this technology would play out might be more complicated.
 
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