AHC: Peerless Air Ministry

The GCI System in Use by the RAF was AFAIK never actually matched in it's technical capability by any system adopted by the Luftwaffe. In 1940 OTL the British were world leaders in the use of RDF (radar) for fighter defence both day and night. Whilst Technically British Radar was not the necessarily the best, the ability and organization to use the new technology was. The RAF are not using GCI/PPI to provide defence lines. the UK is geographically too small for that. Instead it is an integrated whole nation system.
 

perfectgeneral

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UK currently have on strength one hundred and seventy eight night-fighters
One hundred and seventy six (176) if there are sixteen (16) in each. As you say, most squadrons are under strength due to losses, servicing and repair, and waiting for replacements. I think they raised the nominal squadron size for day interception fighters to twenty four (24) because of this issue.

I suppose that old Mk2/Mk3 sets are for training? I hope some get a holiday in the sun as training exceeds home requirements.
 
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10.38 Why do they not come?
10.38. Why do they not come.

September 20th.

Day, One large fighter sweep towards London otherwise reconnaissance only.

Night; London.

Weather, Fair with bright periods. Showery. (1)

There was a slow start to the morning but at ten thirty a large formation of German aircraft was detected assembling over Calais. This mass of aircraft split up into several elements that approached England at various parts of the coast stretching from dover on the East to Dungeness in the west at varying altitudes in an attempt to split Eleven Groups defensive squadrons up. Here the Eleven Group Sector stations into who’s areas the enemy were encroaching showed the real value of the GCI/PPI stations which were now working at full stretch twenty four hours a day. The Kenly sector station handed two of it’s squadrons off to the GCI at Durrington to control the interception of the raid approaching Dungeness, Biggin Hill handed two of it’s squadron over to the GCI station at Wartling as a raid was heading their way and finally Detling sector station passed two squadrons over to the GCI at Willesborough to intercept the raid approaching Dover. This allowed the sector station controllers to concentrate on moving the rest of their squadrons into position to close any gaps or chase down any enemy aircraft that evaded the initial countermoves. The next hour was busy to say the least but no enemy aircraft penetrated inland further than Kenley, Biggin Hill or Detling though a small formation made it as far up the Thames estuary as Tilbury where they were finally intercepted by squadrons from Hornchurch. Two squadrons of RAF fighters fell upon less than a dozen enemy bombers with only a handfull of Me 19’s for escort. Within minutes the retreat of the enemy formation was marked by the tell tale columns of black smoke marking the final resting place of more of their comrades. As the plots finally cleared no new enemy formations were detected and the RAF pilots had a chance to draw breath and as the lull continued it eventually became clear that there would be no further attacks before door that night.



With a waning moon giving what should have been sufficient light for a major Luftwaffe bombing attack the night fighter force was anticipating a very busy night. The one target that the Germans could not resist was London so the sirens summoned one and all to take shelter yet again. Those who remained above ground were rewarded by seeing more than one enemy aircraft become a bright meteor of flame descending to earth and final destruction. To night the guns claimed two enemy bombers shot down over London. The night fighters claimed an additional three of the attackers. Whilst nothing like the number of daylight losses inflicted on the bombers this steady attrition of their numbers was notable and witnessed by the empty chairs in the messes as the crews sat down to breakfast.



(1) Daily summary quoted verbatim from the The Narrow Margin by Derek Wood and Derek Dempster



September 21st.

Day, Slight activity; some fighter sweeps in East Kent.

Night, London and Merseyside attacked.

Weather, Mainly fine. (1)

With the south east of England covered in a thick haze for most of the day there were few attacks until very late in the afternoon. Those attacks that did take place earlier were mostly single aircraft attacking targets of opertunity. For the defenders conditions were particularly difficult and against lone aircraft flyinf fairly low the setor conrolers were struggling to achieve interceptions. Like the day before but for very different reasons the sector controllers start to pass flights or even single fighters off to the GCI stations so that they could use their PPI sets to rapidly vector and intercepting fighter or flight onto an intruder. Even with this innovative system few successful interceptions were made. There was a major change in the early evening when a major attack consisting of five raids again crossing the coast at Dungenes, Lympne and Dover just as they had the day before. Once again the sector stations at Hornchurch, Biggin Hill and Kenley were the primary targets with one enemy formation attempting to break through to central London. To counter this assault eleven group scrambled twenty squadrons including the PAC wing from Debden and Duxford. To the West a single squadron from ten Group was also scrambled. Due too the difficult conditions only two squadrons made successful interceptions but as a counter balance not a single bombs fell on a sector station though windows were rattled at both Biggin Hill and Kenley.

For the second night in a row the Luftwaffe failed to take advantage of nearly perfect bombing conditions b y only mounting moderately strong attacks on Colchester, Nottingham, Bolton, Warrington, Liverpool and London.

Today fighter Command did not suffer a single loss whilst the Luftwaffe lost a total of a dozen aircraft in the period from dawn on the 21st to dawn on the 22nd.



(1) Daily summary quoted verbatim from the The Narrow Margin by Derek Wood and Derek Dempster

September 22nd

Day, Slight activity.

Night, London bombed.

Weather, Dull with fog in morning. Cloudy in afternoon. Fair to fine late. Some rain. (1)

Today saw the lowest mission count for fighter command since the start of the summer battles. Only one hundred and sixty daylight sorties were flown by defending fighters as due to the weather and other factors the Luftwaffe bombers had the Sunday off. For their efforts Fighter Command scored ten victories today for not a single lost aircraft. Some were damaged an a couple of pilots received minor wounds. All in all Sir Hugh Dowding could be pleased with the day encounters.

After dark the situation changed completely as large numbers of enemy aircraft crossed the channel to principally attack London. Soon the city was once more ablaze to an extent not seen since the Great Fire of 1666. Over one hundred and fifty bombers attacked the city with last one turning for home as the first hint of the new days light announced itself on the eastern horizon. Despite their best efforts the night fighter only downed five bombers, though a few more were damaged or as one night fighter crew put it ‘Bloody frightened and praying hard’. The guns again claimed a ‘brace of birds’. So though London had taken another pasting the number of enemy aircraft intercepted, attacked and destroyed was slowly rising. The big question for Sir Hugh was would it rise high enough to cause the Germans to cease their attacks and would relief come to Britain before the final straw broke. Tonight also saw the use of a new tactic by the Luftwaffe, that was to insert intruder aircraft into the returning RAF bomber streams. These aircraft would follow the bombers to their bases and then carry out a quick harassing attack using guns and bombs before running for home.



(1) Daily summary quoted verbatim from the The Narrow Margin by Derek Wood and Derek Dempster
 
An excellent update, the weather's forcing a lull and the Germans have seemingly run out of steam and are probably thankful for the weather's enforced halt to heavy operations too. I assume that Bomber Command's still shockingly bad at its job. I was amazed to find that at the outbreak of the war, bomber command was almost ameture hour. Pilots would be told to bomb or leafelet X or Y and the planes would then make their own way there, at their own speed on their own course and bomb when they arrived. No concentration of bombing, or even set times to arrive, just planes bimbling in on their own accord to drop bombs. No wonder Bomber Command was the laughing stock it was in the early years of the war.
 
Nice work. @sonofpegasus how different are German casualties between OTL and TTL? They are certainly higher, since cannon armament does do a much better job of shooting down Luftwaffe aircraft then .303 MGs, not to mention that proportion of aircraft that crash on their way home or are declared TCL is substantialy higher.

One does wonder how will the large scale and effective use of Night Fighters by the British influence their own night bombing campaign, both in tactics and aircraft design. They should at least recognise that Germans could do unto them at least some damage, and that the German defenses are going to get stronger and more effective as time goes by, and that they should be aware of that. Perhaps, dedicated night bombers should lose most of their defensive armament, only keeping tail turrets, with armament becoming heavier, 20mm cannons instead of .303s, reducing the overall weight and crew of the aircraft. One can already imagine Lancasters with Radar Guided 20mm Tail guns...
 
Previous posts have allude to some important changes in RAF thinking already. One of the most important of these other than 'the bomber is not the be all and end all of Air warfare' is that a bomber has to be able to find it's target if it is going to hit it. Hence the new emphasis on navigational training and the employment of Francis Chichester as a navigational guru. Once having found the target then a better bomb site to hit it reliably was required. OR something ignored in OTL by Bomber Command until around 1942 has ITTL been forced upon them by the AM and will over the autumn start to have an effect. As to night fighters the effect of the RAF having a better radar system of GCI ITTL will actually have more efect on the RAF operational thinking than the Luftwaffe! Ostrich syndrome was well in the ascendancy in Goering's world at this time OTL.
 
The biggest problem with arming Bombers with 20 mm is weight. the second is ammunition.
Weight of the FN-20 turret was 612 kg . this was for 4 0.303 guns(40kg) and 10,000 rds of ammo . enough for 2 minutes of firing. This weighs 218kg

Now a single 20 mm comes in at 43 kg. 2 minutes of ammo will weigh 405 kg.
Using the twin 0.50 they eventually decided on results in a 28kg per gun and 2 minutes of ammo being 220kg I think my data on this is sketchy.. this is acceptable and shows why the twin 50 replaced the 4 0.303. 1600 rds per minute
 
Also wasn't RAF fighter command rabidly protective of its 20mm cannons and there was a huge kerfuffle about any being allocated away from the RAF and fighters. The RAF will still need a bomber command though, because really its the only weapon the UK has to strike back at Germany, and it will need heavy bombers. But if they can be steered away from the Area campaign and the attack against 'will' that would be good. The Germans tried to break the UK's will with the Blitz, that failed, you'd think they would look at that and go 'so bombing folks won't make them surrender'.
 

perfectgeneral

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How much development would it take to have radar controlled guns in the rear turret? No man there would save some weight and casualties and a radar set is more likely to to fire with economy. Since putting on a radar "lamp" is asking for trouble, it would be a weak, short range set with switching wavelengths blipping on until a return is found. Thank you Hedy Lamar.

Bombs will be of thin casing with maximized charge, but where to drop them? An accuracy hasn't been measured to warrant a large scale strategic campaign yet, but they could try "Gardening" and coastal surprise attacks at medium altitude.
 
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The biggest problem with arming Bombers with 20 mm is weight. the second is ammunition.
Weight of the FN-20 turret was 612 kg . this was for 4 0.303 guns(40kg) and 10,000 rds of ammo . enough for 2 minutes of firing. This weighs 218kg

Now a single 20 mm comes in at 43 kg. 2 minutes of ammo will weigh 405 kg.
Using the twin 0.50 they eventually decided on results in a 28kg per gun and 2 minutes of ammo being 220kg I think my data on this is sketchy.. this is acceptable and shows why the twin 50 replaced the 4 0.303. 1600 rds per minute
I must admit that I know rather little about weight of defensive guns, turrets and their ammo, so it is nice to see some concrete info on the matter. Since you know more then I do, how feasable would it be, that Avro Lancaster loses all of its defensive armament, except for the tail turret with twin 20mm cannons, would we see any substantial weight savings? Also, how often were defensive turrets actually used in combat, especially nose and ventral turrets, I do not think that German night fighters attacked from these angles often, especially since they had upwards firing guns on some of their night fighters.

How much development would it take to have radar controlled guns in the rear turret? No man there would save some weight and casualties and a radar set is more likely to to fire with economy. Since putting on a radar "lamp" is asking for trouble, it would be a weak, short range set with switching wavelengths blipping on until a return is found. Thank you Hedy Lamar.
Well, considering the goal of this TL, we could see something like Village Inn enter service earlier, which would certainly save a couple of Bombers.
 
Well, considering the goal of this TL, we could see something like Village Inn enter service earlier, which would certainly save a couple of Bombers.
There is a big difference between Village Inn and removing the gunner from the tail. 80% of contracts in the bomber stream are friendly, and IFF at the time was a pair of IR lamps. The gunner is there as a lookout and IFF system.
 
I must admit that I know rather little about weight of defensive guns, turrets and their ammo, so it is nice to see some concrete info on the matter. Since you know more then I do, how feasable would it be, that Avro Lancaster loses all of its defensive armament, except for the tail turret with twin 20mm cannons, would we see any substantial weight savings? Also, how often were defensive turrets actually used in combat, especially nose and ventral turrets, I do not think that German night fighters attacked from these angles often, especially since they had upwards firing guns on some of their night fighters.
Think you mean dorsal not ventral as the Lancaster's turrets were front, back and top :). The top and nose turrets were removed on all the special Lancaster's used to carry Grand Slam bombs as , for obvious reasons, weight was a major issue. The Dambuster machines likewise lost the upper turret, again for weight saving.

So for night bombers, just having a rear turret was not seen as a major issue. At night, virtually all attacks were from the rear ( and with the Schräge Musik guns rear and below) at night as , without low vision gear , deflection shooting was not really possible )

As the rear gunner's job was mainly to cause fighters to miss, by alerting the pilot to maneuver, shooting down aircraft was not a major objective so the extra weight of 20mm probably not worth it. Most bombers lost to night fighters never even saw their attacker.
 
Think you mean dorsal not ventral as the Lancaster's turrets were front, back and top
AIUI RL was a bit more complicated than that :frown:

Like a lot of bomber designs, the Lancaster was originally intended to have "all-round armament"... in this case
front (aka nose) - 2 guns
rear - 4
top (aka dorsal aka mid-upper) 2
bottom (aka ventral) 2
all guns originally the RAF standard .303. ~3000 round per gun at the rear , ~ 1000 on the others, which shows something I suppose.

The ventral turret was pretty soon deleted (both in deployed aircraft and production)
for the very reasons we have been discussing

but the turret ring remained. In 42 that ring became the mounting for the H2S ground mapping radar
Ninja-ed by PLP

When the Germans began using "from below" attacks",some squadrons ... especially the Canadians ..ditched the H2S for adhoc .50 calibre guns.

At about the same time new rear turrets were designed with 2 x.50 (about the same weight was 4x.303)
In practice, the new turrets were not more effective as weapons
but some (especially the Rose Bros. design) had better visibility and was easier to escape from.
Few flew in WW2 though it was standard post war

As to electronic systems,
The RAF fitted active tail warning radar but had to withdraw it when they discovered the Nazis were homing on its transmissions.
Similarly, they did try automatic gun aiming systems for the Rear turret, but abandoned the "auto fire" since the IFF element never worked reliably.

However several other Radar gun sights were tried ... all with little use in WW2 but becoming standard in the postwar Lincoln.
 
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One thing to consider is that with radar being more developed than otl the four engine bombers might be designed with H2S radar from the start, rather than having it added later. Maybe they can have the scanners under the nose and still have ventral turrets.
 
I am at the moment having a problem finding out whether 50cm radar could be used for groyund mapping like the centimetric H2S could. If anybody can help with that I would be gratefu
 
I am at the moment having a problem finding out whether 50cm radar could be used for groyund mapping like the centimetric H2S could. If anybody can help with that I would be gratefu
The answer is yes but. You can do it but have two issues , the size and weight of the antenna needed will increase. Today oceanographers use HF radars ( so wavelength in 10's of meters, its approximately the normal wavelength of ocean waves they are interested in ) to map ocean surface currents for example.
 
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