RAF Bomber intercept doctrine?

[Voyager]

Been playing around with some bomber interception missions in the other game, and noticed that machine guns aren't the rapidest method of downing He-111's. So I'm wondering, what doctrines did the RAF use for their bomber interceptions during the battle of Britain? 

 

What angles were recommended and generally used during approach?

 

What gun convergences were generally sued for the bomber interceptors?

 

Did the fighters do a one-and-done, or was it typical to continue re-engaging until either you ran out of ammo or something important got hit?

 

If they reset for further passes, how did they reset? How long would it be expected to take?

 

Thank you,

 

Harry Voyager

[Chief_Mouser]

As much as I hate to send anybody across to WarThunder this gives an idea.

https://warthunder.com/en/news/209/current/

The Fighter Area Attacks were the order of the day and totally useless. The RAF were so doctrine-led and hidebound in their outlook it came a nasty shock to find that the Luftwaffe had other ideas.

[Voyager]

Ah, yeah I ran into that. I'm more looking for how you successfully attack a bomber formation which machine guns. With late war rapid fire cannon, I know you set up a head-on attack, unload the guns and go home because by then you're generally out of ammo. With a machine gun load, that seems to be not very effective, and you've also generally seem to have a lot more ammo left over after the first run.

 

Did the RAF develop effective bomber engagement tactics durign the BoB? Setting up behind a bomber box seems to more effective at finding a way to walk home, rather than knocking down the bombers.

[ZachariasX]

4 minutes ago, Voyager said:

With a machine gun load, that seems to be not very effective,

Guess why they went for 20 mm as soon as they became somewhat reliable.

[DD_Arthur]

2 hours ago, Voyager said:

I'm more looking for how you successfully attack a bomber formation which machine guns. 

 

In the age of the flying gun you attack the same way with mg's as you did with cannon.  After some experience the RAF found the most effective way to attack a formation was head on.  You expose yourself to a minimum amount of return fire but have a very short firing time.

When it worked it was extremely effective at breaking up a formation.

 

For the RAF getting that tactic to work was difficult.  The amount of early warning received meant it was difficult to get a formation into the air and up to a height where intercept was possible.  This was especially true for Hurricane units.  

 

What happened after the first pass depended on if/where the bomber escort appeared from and whether another pass was possible.  There are plenty of accounts of squadrons managing to retain a formation and have another go if there was no escort to interfere but generally it descended into a melee with wingmen if the escort did manage to intervene.

 

Returning from a sortie after exhausting the ammunition was not unusual but not the norm.  Even at the height of the battle firing chances were minimal. 

    

[Voyager]

@DD_Arthur Ah thank you. That is what I was looking for. So go for the headon, and start the firing run from ~500 yards instead on my usual 250 yard convergence. 

 

Make the pass, and see if I'm being engaged by the air defence fighter. If not, climb over the bombs and set up for another head on pass, and repeat until I need to go home from lack of fuel, interception or loss of ammo. 

 

Are there any good rules of thumb for where to do the reversal to end up on their nose? I've noticed that turn circles at altitude are much larger and slower than at low level. 

[DD_Arthur]

6 hours ago, Voyager said:

 So go for the headon, and start the firing run from ~500 yards instead on my usual 250 yard convergence. 

 

Make the pass, and see if I'm being engaged by the air defence fighter. If not, climb over the bombs and set up for another head on pass, and repeat until I need to go home from lack of fuel, interception or loss of ammo. 

 

Are there any good rules of thumb for where to do the reversal to end up on their nose? I've noticed that turn circles at altitude are much larger and slower than at low level. 

 

I think they opened fire rather closer than 500 yards.  They only had time for a quick squirt at those closing speeds and yes, turning circle and trying to keep the formation together along with how far further the bombers had travelled meant that the headon attack could only be performed once.  If they were still in contact the fighters would climb and turn to re-engage from above and behind.

However it would be unusual for a squadron to retain a coherent formation after that first pass.   

[unreasonable]

14 minutes ago, DD_Arthur said:

 

I think they opened fire rather closer than 500 yards.  They only had time for a quick squirt at those closing speeds and yes, turning circle and trying to keep the formation together along with how far further the bombers had travelled meant that the headon attack could only be performed once.  If they were still in contact the fighters would climb and turn to re-engage from above and behind.

However it would be unusual for a squadron to retain a coherent formation after that first pass.   

 

I think they would be opening fire at at least 1000m in a frontal attack if they could get lined up. An He111 cruises at 360kph, let's say the Spitfires are doing 500, that is equivalent to 238m/s closing speed. 

 

You will have to break off from your point of aim a second or so before you collide,  so even opening up at 1,000m you are only getting about one three second burst: unless you can kill the pilot with that nothing much will happen with 303s. 

 

That is why the pre-war doctrine RAF advocated rear attacks -  at these speeds you are now closing at only 39m/s, so allowing time for collision avoidance you could fire for ten seconds (pretty much the full load IIRC) starting at 4-500m out.

 

In reality, from my reading, the bombers in the BoB were usually escorted by large numbers of snappers so the interceptors just had to plough in from whatever angle they found themselves. They would rarely have the luxury of leisurely repositioning for another run. 

[DD_Arthur]

14 minutes ago, unreasonable said:

 

I think they would be opening fire at at least 1000m in a frontal attack if they could get lined up. An He111 cruises at 360kph, let's say the Spitfires are doing 500, that is equivalent to 238m/s closing speed. 

 

You will have to break off from your point of aim a second or so before you collide,  so even opening up at 1,000m you are only getting about one three second burst: unless you can kill the pilot with that nothing much will happen with 303s. 

 

In reality, from my reading, the bombers in the BoB were usually escorted by large numbers of snappers so the interceptors just had to plough in from whatever angle they found themselves. They would rarely have the luxury of leisurely repositioning for another run. 

 

I defer to Unreasonable on firing distances!

 

I also agree with a basic point unreasonable has made;  whilst the headon attack was the most effective in breaking up a formation, in practice the RAF would have to wade in wherever opportunity allowed.  The LW escort were nearly always above the bombers and any attacking force.  

 

One area where flight sims tend to fall over are the vagaries of european weather.  Clouds, haze, etc. could soon render even a large attacking force invisible in short order.  

[danielprates]

Great info in this thread. Thanks to you all!

[Sokol1]

BoB gun can footage, most attacks from rear quarter, distances informed for some.

 

 

https://www.youtube.com/watch?v=UKJdVn2i8is

 

In RL BoB are cases of pilots shooting down two bombers in one sortie.

In one case three, but one damaged bomber colide with another.

 

In game Quick missions, I shoot six He 111 once (full difficult, ammo limited) but at time AI gunners are a bit "Mr.Magoo", has improved in Blitz.

https://theairtacticalassaultgroup.com/forum/attachment.php?attachmentid=5526&d=1383354751

 

Someone in game tactics (multiplayer):

 

 

Edited April 23, 2020 by Sokol1

[Avimimus]

On 4/19/2020 at 6:39 AM, unreasonable said:

 

I think they would be opening fire at at least 1000m in a frontal attack if they could get lined up. An He111 cruises at 360kph, let's say the Spitfires are doing 500, that is equivalent to 238m/s closing speed. 

 

You will have to break off from your point of aim a second or so before you collide,  so even opening up at 1,000m you are only getting about one three second burst: unless you can kill the pilot with that nothing much will happen with 303s. 

 

That is why the pre-war doctrine RAF advocated rear attacks -  at these speeds you are now closing at only 39m/s, so allowing time for collision avoidance you could fire for ten seconds (pretty much the full load IIRC) starting at 4-500m out.

 

In reality, from my reading, the bombers in the BoB were usually escorted by large numbers of snappers so the interceptors just had to plough in from whatever angle they found themselves. They would rarely have the luxury of leisurely repositioning for another run. 

 

Just a bit to add on pre-war doctrines:

 

From what I gather there had been a desire in some circles to upgrade firepower from two to four machine guns by 1927.

 

However, the big change happened in 1934 (requirement F.5/34). This happened after a calculations by Ralph Sorley showed that increasing speeds of aircraft meant less time for the guns to fire. Assuming that fighter pilots would usually only get one pass on an enemy bomber, using eight browning machine guns it would be possible to achieve just over 250 rounds per second. This was deemed the sufficient weight of fire to down a bomber with a few seconds of fire during a single pass. This was clearly deemed insufficient in practice as the requirements for later Hurricane and Typhoon would be designed around twelve browning machine guns.

 

The other approach was the turret fighter. These could concentrate the firepower of a smaller number of guns over a long period of time. It was envisioned that an entire squadron of Defiants would approach a bomber stream with their pilots able to focus on maintaining a tight formation (as they didn't need to aim) and the gunners would be able to overwhelm the bombers with superior firepower. This idea was appealing enough that the RAF received over a dozen different design studies for anti-bomber fighters with machine gun or cannon turrets.

 

However, that wasn't the end of the story as the RAF foresaw an arms race of more destructive cannons firing at ever long ranges:

 

Anticipating a similar enemy doctrine of massed attacks - the RAF intended its bombers to have superior firepower with the definitive RAF bomber having eight or even twelves 20mm Hispano cannons in two or three giant four gun turrets. These bombers would operate in the day time at medium altitudes where accuracy and payload could be maximised. The only thing which prevented the entry of these bombers into production in 1941-1942 was actual wartime experience that showed night bombing to be a safer approach and altitude a better defense. However, if the war hadn't taken place such aircraft would have been seen alongside defiant like twin-engined designs. This trend was considered to possibly continue with 40mm cannon turrets designed, including potentially for use on heavy interceptors.

 

Note: Even before the war the use of four (or even 6) 20mm Hispano cannons was considered for fighters, and would likely end up as their definitive armament (as happened historically). However, reliability issues limited their use until 1941-1942 and encouraged the use of mixed-gun Spitfires.

 

Note: British Secret Projects Vol.3 by Tony Butler is a source of much of this information.

Edited April 28, 2020 by Avimimus

[Avimimus]

Just another thought about tactics... it has been a while since I saw the data (it was on the old UBIsoft forums)... but I remember someone posting data which showed that penetration was decreased by a couple of millimetres as a result of rounds first passing through the skin of an aircraft. The study had concluded that the bullets were yawing slightly as a result of passing through the skin and thus weren't completely aligned with the direction of travel when they hit the target. So we're talking about pretty marginal penetration (and a bit less than the tables would typically indicate).

 

This is interesting if one considers how quickly rounds lose velocity while travelling supersonically - especially small rounds that have a lower mass compared to their surface area). If one wants to get enough penetration to damage the aircraft's systems... it would make sense to fire at very close ranges where your rounds are still supersonic.

Edited May 2, 2020 by Avimimus

[ZachariasX]

On 4/28/2020 at 9:39 PM, Avimimus said:

Anticipating a similar enemy doctrine of massed attacks - the RAF intended its bombers to have superior firepower with the definitive RAF bomber having eight or even twelves 20mm Hispano cannons in two or three giant four gun turrets.

Such has been tried by the Germans as well. To protect the Me-323, they made a variant, the Me-323 WT (Waffenträger) by adding 20 mm turrets.

Wasn‘t helpful at all.

 

Bottom line for the British is that it took them until 1941 to have a somewhat useful 20 mm gun. Until then, there was just the machine gun and they had to make do with that.

 

 

[RNAS10_Oliver]

On 4/18/2020 at 9:25 PM, Voyager said:

What angles were recommended and generally used during approach?

 

What gun convergences were generally sued for the bomber interceptors?

 

Bit late to the party, and maybe it's just specific to the Fleet Air Arm in 1941 (though doubt) but for what its worth in Mike Crosley's book he mentions quarter attacks being the done thing, rabbits on about them to be honest.

 

Quote

Attacks from dead astern, were, of course, asking for trouble. First, you gave the rear-gunner of the bomber an easy no-deflection shot at you. Secondly, he might have 0.5 inch guns to your 0.303 inch and so he could easily out-range you. He could then start shooting you 150 yards before you could hope to hit him with your much less powerful Brownings. Thirdly, by spending any time right behind him, you would find that your fighter aircraft would become uncontrollable in his slipstream. Accurate aiming then became impossible. The answer was to do a quarter attack, starting from about 30 degrees to one side or the other of his stern, or from above or below. This avoided the slipstream effects and provided the bomber's rear gunner with a difficult target.

 

Quote

I remembered the silhouette on the Heads door, and that it had some guns pointing out of its backside. I was determined, therefore, not to come straight up its jacksie, but to do a proper quarter-attack, so giving the rear gunner a deflection shot, not an easy shot at me. From a position abeam and above him I entered the prescribed and much practised quarter-attack from his port side. I was shattered to see that I was still miles out of range by the time I was at about 30 degrees off his quarter, and that I should be in line-astern, and an easy, no deflection, shot for his rear gunner if I continued to come in from there. Still there was nothing I could do about it now, except perhaps come in from below and astern and keep clear of his slipstream that way.

 

Quote

Spike was my leader and I was perhaps a trifle relieved that it would be his job this time to go in first. I was determined to make sure I had enough speed and enough distance ahead before I turned in. This was so that I could make a proper quarter attack within a range of 250 yards, as I had been taught. I climbed up on the Ju 88's port beam, well ahead and at a distance of 1000 yards. Spike was still closing astern of him on a firing run and I could see his aircraft getting closer and closer to the Ju 88. Then I could see his gun smoke as he opened fire in a long burst, perhaps eight seconds. Not a thing happened to the Ju 88. My heart beat faster as I realised that it was now my turn to do something brave.

 

As I turned in on his port bow 1000 feet higher than him, I could hardly believe my eyes. The dammed Ju 88 turned about 30 degrees away and leapt ahead of me as I tried to position my self once more for a quarter attack. It was moving at twice the speed of our practice targets at fighter school and I was moving at three times the speed. By the time I was at the correct angle-off of about 30 degrees, I was still too far away from him to stand a chance of doing him any damage.

 

All I could do was to carry out the same sort of attack that I had done on the Cant.

 

Quote

If Tricky was, in fact, vectoring me alone, and not a lot of other Hurricanes, then he had done a superb job, having positioned me up sun and with a good height advantage. There were at least four flights of our or five SV 79s, each flight in a typical "Balbo" line astern. They were so close to each other that it was only possible to attack the single "arse-end Charlie" in the formation, and the rear one at that. The only chance was a classic quarter attack, coming in from the south, positioning up sun with my shadow superimposed over the target at the start of the turn-in, breaking-off before reaching the line astern position.

 

The National Archives are providing the downloads of their online records for free at the moment due to the current madness while they are closed to visitors. I've downloaded one that contains the Operational Records Books for 803, 805 and 806 (grouped together as the Royal Naval Fighter Squadron) between August 1941 and January 1942. There's also a number of combat reports interspersed and there does seem to be a fair few "quarter attacks" mentioned in them. But also mention this there's four combat reports stating the gun alignment on their aircraft being set as 275 yards, and one combat report stating at 250 yards instead.

 

Edited July 4, 2020 by Oliver88

[Avimimus]

2 hours ago, Oliver88 said:

Bit late to the party, and maybe it's just specific to the Fleet Air Arm in 1941 (though doubt) but for what its worth in Mike Crosley's book he mentions quarter attacks being the done thing, rabbits on about them to be honest.

 

We are discussing 80 year old history... I think being a few weeks late to contribute something is hardly a problem ?

 

Thanks for the informative post (and the research)! It is really interesting.