Why did Britain give up on the Avro Manchester bomber?

[tomo pauk]

As for concept of fast bomber, while it backfired in day ops, it was very workable for night ops. The night fighters were inherently heavier draggier than day fighters ( usually 2-3 seaters, antennae sets for Luftwaffe types, heavy armament), so most of them resembled performed more akin to bombers, than common fighters. Too bad Americans didn't built (X)B-38s (with turrets replaced by single HMGs, no waist guns) for RAF Bomber command.

 

[Shortround6]

The 8,8 (56 cal barrels) formed the bulk of Luftwaffe heavy Flak force (80% ? in 1944, but perhaps 90-95% in 1942). I'd venture to say the bomber cruising at 25K has much better chance to avoid heavy Flak guns than one flying at 20K.

I am not sure about German practice but by 1944 allied practice/terminology was the that effective ceiling of the AA gun was the altitude at which a 300mph airplane could be engaged for 20 seconds. Yes, a plane flying at 20,000ft can be engaging for a longer period of time or by guns further to side of it's flight path than a plane flying at 25,000ft. The higher altitude will increase the difficulties of the AA defense but will not grant immunity just as a higher cruising speed increases the interceptor fighter's difficulties but does not grant immunity. The price of these performance gains in order to secure large performance increases (on the order of the Mosquito for example) may be not only no defensive armament but lower bombloads, shorter range which need more missions to deliver the same tonnage of bombs.

 

[tyrodtom]

The only turret i've found the weight on is the Sperry ball turret, as installed in the B-17, 1200lbs, with gunner, who had to be a small guy.
They were thinking about eliminating the belly turret late in the war, that's the weight they figured it would save. That 1200lb wouldn't include the extra structual reinforcement added in the fuselage for that turret or the extra generating capacity to power it, or the extra life support sytems for the gunner.
The belly turret in the B-24 would be even heavier, it was retractable.
My wag estimate of 1000 lb per gun might be a little too much, some of the gunner positions was performed by crewmembers with other functions also.

 

[tomo pauk]

Hi, shortround6,
You can note that I was proposing deletion of turrets, to save both on weight and drag. As you've stated, the weight reduction is 500lbs per power-turreted gun, so deletion of 3 turrets (8 guns total) yields 3000-4000 lbs of weight saving. The part of that saving is canceled out by replacing the turrets with gunner single MG (twin MG for stern position? weight 300 lbs per position?; 1000 lbs total), so we save perhaps 2000-3000 lbs.

 

[Shortround6]

that and British turrets often had four .303 guns which is what really throws the weight per gun thing off.

 

[pbfoot]

quoted from Mike Lewis DFC CD one of the first Manchester pilots 207 Sqn quoting about Manchester 1A "the mid upper turret on the Manchester never did function properly. When rotated it set up a disconcerting vibration in the airframe. The AirMinistry finally circulated aletter permitting the squadrons and Avro to remove the turret if desired . I always had the mid upper removed from my aircraft removed from my aircraft giving me an extra 10 mph and improving single engine performance immenesly `` Mike Lewis did 2 tours on Manchesters

 

[tomo pauk]

Truth to be told, that turret itself seem like the draggiest ever produced.

 

[Shortround6]

Hi, shortround6,
You can note that I was proposing deletion of turrets, to save both on weight and drag. As you've stated, the weight reduction is 500lbs per power-turreted gun, so deletion of 3 turrets (8 guns total) yields 3000-4000 lbs of weight saving. The part of that saving is canceled out by replacing the turrets with gunner single MG (twin MG for stern position? weight 300 lbs per position?; 1000 lbs total), so we save perhaps 2000-3000 lbs.

I think you either keep the power turrets (and get them to work) or you design a new plane without the gun stations. Pulling turrets out of an existing airframe and plating over the holes saves weight but doesn't save a whole lot on drag. Some, maybe, but not as much as a new thinner airframe. They went to turrets because hand held guns didn't work very well. Difficult to aim in a several hundred mile an hour slipstream and in many cases the hand held guns had limited ammo capacity. IF 4 power driven .303s won't bring down an enemy fighter (80 rounds a second) then a single Vickers K gun (18 rounds a second?) isn't going to do much good on average.
Going from a cruise of 215-240mph to even 265mph is not going to stop the fighters from intercepting a large portion of the time. You need to get to 300mph plus and be able to keep it up for for 1/2 hour to hour at a time (or longer?) just ripping a couple of turrets out of an existing design isn't going to do it. As far as twin .303 out the back in hand held mounts try checking the record of the Handley Page Hampden. Early Wellingtons used twin powered "mounts" that weren't really turrets. The gunner did not sit in with the guns and turn with them. Some early American bombers had Manual tail guns, like the early B-26s. If you are going to ruin the lines of the fuselage by making the tail big enough to hold a man and you are going to stick 200lbs of man and chute, 100-200lbs of guns and ammo (more if they are .50s), commo equipment, oxogen, suit heating, etc you might as well go whole hog and stick in the power turret and drastically change his chances of actually hitting something.

 

[tomo pauk]

The reason I'm not proposing ditching the defensive MG posts all together is not because I think that hand-aimed MGs would be good replacment, but because the observer checking around is good to have on night bomber. So since we have observers in lieu of crewed gun turrets, me might have a MG by himself. Since I've proposed re-engining the Manchester too, that, coupled with 1+ ton weight saving (gained by deletion of turrets) mean something for performance.

And now, I'd order some Mossies for upcoming bomber missions vs. Germany.