Aerial Bombing Question

[swampyankee]

There was a lot of exaggeration, possibly most from the USAAC/USAAF, about how accurate high-altitude bombing could be.

Complicate that with the limited load capacity of bombers of the era, overestimation of the vulnerability of factories and other targets, and underestimation of the vulnerability of bombers to interceptors, and you have a perfect set up for failure on strategic terms, and that is exactly what happened to the USAAF's original bombing strategy.

 

[Zipper730]

I'm curious if the bombsight technology we developed influenced the fire control system on interceptors? I ask because some of the interceptors we used were automated up the wazoo to levels that were often unnecessary.

As a comparison

Norden Bombsite

1. With airspeed, heading, and altitude...
2. The bombsite is adjusted so as to compute the ground-speed and predict correct impact point...
3. The site is basically run on a timer at that point, ticking down until...
4. Bomb release

USAF Radar & Fire Control Systems: F-86D, F-102A, F-106A, etc

1. Target is acquired with radar and locked on
2. Fire control system computes interception vectors, and gains control over the aircraft to maneuver it into position for...
3. Weapons release, and then
4. Breakway

While a bit off topic, I'm just curious if the level of automation used for interceptor FCS is based on...

1. The NBS
2. Coincidentally to the operational needs of an interceition

 

[stona]

There was a lot of exaggeration, possibly most from the USAAC/USAAF, about how accurate high-altitude bombing could be.
.

Every single air force with a bomber was guilty of that exaggeration.
In the case of the British, in the 1930s, this even led to a roughly ten year flirtation with the idea of precision bombing which ran contrary to everything it had stood for 1916 and which wouldn't finally be abandoned until 1942. There were many reasons for this flirtation, I would argue primarily the realisation that the service simply didn't have enough bombers, let alone suitable bombers, to carry out a strategic campaign,meaning it would have to attempt something which was contra-doctrinal or risk losing it's independent bomber force altogether.
Cheers
Steve

 

[pbehn]

Every single air force with a bomber was guilty of that exaggeration.

Companies trying to sell things tend to be enthusiastic. I have some sympathy with the USA military and manufacturers on this. The theoretical question of hitting a target from a high altitude is different from hitting targets in Europe and Japan which have huge and unknown (in USA) wind speeds at those altitudes.

 

[swampyankee]

A war game referee deciding if a practice bomb is close enough to destroy something is also different than a target's destruction being decided by laws of physics.

 

[wuzak]

Companies trying to sell things tend to be enthusiastic. I have some sympathy with the USA military and manufacturers on this. The theoretical question of hitting a target from a high altitude is different from hitting targets in Europe and Japan which have huge and unknown (in USA) wind speeds at those altitudes.

The problem for the USAAF was that they tested the Norden bomb sight in unrealistic conditions. That is, at altitudes below what would actually be used (around 10,000ft rather than 20,000-30,000ft), in clear desert skies and with no simulated opposition, either from fighters or flak.

Then they took these results and used them to claim the incredible accuracy the Norden allowed, talking up the "pickle barrel" accuracy. And their propagandists ran with it.

 

[pbehn]

The problem for the USAAF was that they tested the Norden bomb sight in unrealistic conditions. That is, at altitudes below what would actually be used (around 10,000ft rather than 20,000-30,000ft), in clear desert skies and with no simulated opposition, either from fighters or flak.

Then they took these results and used them to claim the incredible accuracy the Norden allowed, talking up the "pickle barrel" accuracy. And their propagandists ran with it.

Well they would wouldnt they? No one would say "no chance of hitting anything there on five days out of six"

 

[Shortround6]

I'm curious if the bombsight technology we developed influenced the fire control system on interceptors? I ask because some of the interceptors we used were automated up the wazoo to levels that were often unnecessary.

As a comparison

Norden Bombsite

1. With airspeed, heading, and altitude....................................Breakway

They were about 10 years apart in timing.

And when you are talking about stopping nuclear armed bombers just how much "aid/help" to the pilots in ALL WEATHER conditions is too much or unnecessary?

 

[Koopernic]

I think the USAAF had units of comparable skill, but that kind of accuracy could not be realized in anything other than small unit raids. As an aside, at least one of the bombs dropped on the Tirpitz went through the ship and detonated underneath.

I don't think that American Tacticians or Strategists exaggerated the Norden bombsight as much as underestimated the effects of European cloud cover and the ferocious German resistance. Also formation bombing produces a spread of bombs related to the dimensions of the formation.

I am not overly impressed with SABS II or the supposed unique accuracy of 617 squadron in bombing the stationary and moored Tirpitz (Operation Catechism 12 December 1944). Both the USAAF (Norden) and Luftwaffe (Lofte 7) had gyro stabilised wind and motion correcting bombsights that were as good and crews that could and did perform their drills just as well and courageously in the face of equally or more terrible opposition. (There was no fighter opposition to catechism due to treachery of the German officer who was in command at the Wassermann radar station, he certainly sent confusing information and was in contact with Norweigen Resistance who were agents of the British)

The Tirpitz had a dimension of 250m x 36m which would produce a deck area of 4500sqm. The Lancasters attacked from staggered altitudes of 12000ft up to 16000ft. At that altitude the Tirpitz had a dimension of 0.7% to 7% of altitude. It's the same area as a 76m/84 yard diameter circle. The average radial error of 125 yard often quoted for the SABS II subtends a circle smaller than the length of the Tirpitz's length. The deck area of the Tirpitz is probably around 4500sq meters and the area of the 125 yard circle is less than 40,000 sq meters. Assuming that 30 bombs are aimed and 15 are dropped within that circle then the average chance of a hit for each individual bomb is about 12%. Get 15 bombs in that circle and the compounded chances of a hit are 1-0.88ˆ15 or 89%. This doesn't take into account the clustering of the bombs about the centre. Perhaps 'line errors' are more appropriate given the Tirpitz's dimensions.

I'm thinking of the 1942 Fw 200C4 Condor attack on Convoy Faith in which the Focke Wulf seemed to hit a 12-15 knot ships from similar altitudes about 33% of the time with a stick of either 2 or 4 bombs. The escort ships used their speed and manoeuvrability to narrowly evade several bombs as the fall time would have been around 30 seconds but the cargo vessels were too slow.

Some of of the USAAF bridge busting raids using B-26 would have been equally impressive and certainly more important than sinking a crippled stationary battleship in Norway while Germany was surrounded on all sides.

It's plausible that in similar circumstances of no air opposition that Luftwaffe Dornier Do 217M could have conducted a similar raid with a single SC 1700kg bomb, a pair of 900L drop tanks and additional 700L fuel tank in the rear torpedo bay bomb bay. The straight line distance Murmansk-> Tromso->Edinburgh is less than 2400km/ 1440 miles.

Part of the SABS 2 bombsights reputation comes from the fact it was used with elite squadrons. The standard MK 14 bombsight was used by average crews as well as elites. The Mk 14 couldn't calculate the offset required to compensate for target motion by tracking target or wind rift like the Norden, SABS or Lofte 7 but it could be set up with an wind drift estimate calculated elsewhere e.g. The path finders. It's Trick was bombing in a slide or while manoeuvring. It was used at night so target tracking was mute or used at low level facing forward in a mosquito.

The Luftwaffe also had the Fritz-X guided bomb which was aimed by a computing bombsight and would have had the same accuracy as a normal but was terminally guided. Corrections were possible 500m in range and 300m in cross range.

A practised bombardier could manage to guide 50% of the bombs to within a 15 m (50 ft) radius of the aiming point, and about 90% hit within a 30 m (100 ft) radius (other sources say 60% hits within 4.6 metre radius)

 

[stona]

Companies trying to sell things tend to be enthusiastic.

As do services, including air forces/air arms, competing for a slice of an always limited and sometimes severely limited military budget. This was particularly true of the relatively newborn RAF competing against the Royal Navy and to a lesser extent the Army in the 1920s and 1930s.
Cheers
Steve

 

[stona]

A war game referee deciding if a practice bomb is close enough to destroy something is also different than a target's destruction being decided by laws of physics.

This applied to the criteria by which bombers were judged to have successfully shot down fighters and by which fighters failed to shoot down bombers in many pre-war exercises. The referees simply pandered to, or indulged, the prevailing prejudices.
Cheers
Steve

 

[stona]

I am not overly impressed with SABS II or the supposed unique accuracy of 617 squadron in bombing the stationary and moored Tirpitz (Operation Catechism 12 December 1944).

You can't make any meaningful comment on the accuracy of any sight based on one raid. Of the aircraft attacking, eighteen were equipped with the SABS and twelve with the Mk XIV sight and nobody knows whose bombs went where (see Bomber Command's ORS Report S.218). It is, in the context of a discussion of the accuracy of SABS, almost completely irrelevant. In any case three bombs struck Tirpitz and at least another seven (maybe ten, depending who you believe) landed within the torpedo nets, three very close to the ship, which is remarkably accurate bombing. Six of twenty nine bombs dropped either hit or landed close enough to severely damage the target. Whether a specially trained Norden equipped unit of US bombers in Europe could have come close to this is a moot point as it couldn't have carried a tallboy to make the attempt. The Americans had earlier declined to make the Norden sight available to the British.
The facts are that the SABS, of which less than 1,000 were ever made, in the hands of No. 617 Squadron, achieved an average radial error of 125 yards in all assessed operations between January and March 1945. Given that many of these raids were with special ordnance almost all were assessed.
The Mk XIV bomb sight, used by two other specially trained 'precision' squadrons achieved an error of 195 yards in the same period. The SABS was statistically and in reality a more accurate sight. The above figures were rarely achieved by US bombers equipped with Norden sights, which might explain why British interest in it quickly waned and it was rejected when finally offered late in the war.
ALL US bombers were supposed to be precision bombing, at least as far as the public back home was concerned, yet their results were often worse than those achieved by the RAF's area raids at night. In the last quarter of 1944, for bombs dropped by the USAAF in Europe under conditions of good visibility (as the RAF enjoyed for 'Catechism' ) the figures show that B-17s dropped 13.1% and B-24s a mere 8.8% within 500 feet/ 166 yards of the aiming point with the Norden sight.
The main draw back of the SABs when compared with the Mk XIV (though not the Norden) was the tactical limitations imposed by a long, straight and level bomb run. The Mk XIV required a ten second run and could be used in a climb or glide, allowing a greater degree of tactical freedom, though Bomber Command still attempted to limit evasive manoeuvres. The SABS was also complicated and difficult to manufacture and required skilled maintenance, certainly when compared with the Mk XIV.
Cheers
Steve

 

[Koopernic]

You can't make any meaningful comment on the accuracy of any sight based on one raid. Of the aircraft attacking, eighteen were equipped with the SABS and twelve with the Mk XIV sight and nobody knows whose bombs went where (see Bomber Command's ORS Report S.218). It is, in the context of a discussion of the accuracy of SABS, almost completely irrelevant. In any case three bombs struck Tirpitz and at least another seven (maybe ten, depending who you believe) landed within the torpedo nets, three very close to the ship, which is remarkably accurate bombing. Six of twenty nine bombs dropped either hit or landed close enough to severely damage the target. Whether a specially trained Norden equipped unit of US bombers in Europe could have come close to this is a moot point as it couldn't have carried a tallboy to make the attempt. The Americans had earlier declined to make the Norden sight available to the British.
The facts are that the SABS, of which less than 1,000 were ever made, in the hands of No. 617 Squadron, achieved an average radial error of 125 yards in all assessed operations between January and March 1945. Given that many of these raids were with special ordnance almost all were assessed.
The Mk XIV bomb sight, used by two other specially trained 'precision' squadrons achieved an error of 195 yards in the same period. The SABS was statistically and in reality a more accurate sight. The above figures were rarely achieved by US bombers equipped with Norden sights, which might explain why British interest in it quickly waned and it was rejected when finally offered late in the war.
ALL US bombers were supposed to be precision bombing, at least as far as the public back home was concerned, yet their results were often worse than those achieved by the RAF's area raids at night. In the last quarter of 1944, for bombs dropped by the USAAF in Europe under conditions of good visibility (as the RAF enjoyed for 'Catechism' ) the figures show that B-17s dropped 13.1% and B-24s a mere 8.8% within 500 feet/ 166 yards of the aiming point with the Norden sight.
The main draw back of the SABs when compared with the Mk XIV (though not the Norden) was the tactical limitations imposed by a long, straight and level bomb run. The Mk XIV required a ten second run and could be used in a climb or glide, allowing a greater degree of tactical freedom, though Bomber Command still attempted to limit evasive manoeuvres. The SABS was also complicated and difficult to manufacture and required skilled maintenance, certainly when compared with the Mk XIV.
Cheers
Steve

The Norden couldn't be measurably less accurate than the SABS 2.

In principle the SABS 2 worked the same way and didn't add any computational refinements: Both sights were gyrostabilised, calculated the true ground speed of the aircraft by tracking an object near the target or the target itself. This was done by the bombardier setting the speed of variable speed electric motors that moved the optics till the target remained steady in the cross hairs.. The motion of the optics was linearised to account for the bombsights angle of view and altitude hence the speed of the motors was proportional to the ground speed.

They used this true speed over ground to calculate offsets to compensate for target motion and or winds.

What the SABS Bomb sight had to achieve in bombing the Tirpitz was +/- 0.28 (0.56) degrees accuracy for the beam and +/- 2.0 (4.0) degree for the length of the Bismarck which isn't very high.

Neither sight had Ballistic data for the bomb. The bombardier used tables and dialled in bomb fall time, bomb trail error (compared to a bomb dropped in vacuum) and air speed.

Probably the most impressive level bombing successes was achieved by the lofte 7D carried on three Fw 200 Condors of III/KG40 who in July 1943 attacked Convoy Faith. Each of the 3 Fw 200 dropped 4 250kg bombs and achieved 4 hits on 3 moving ships sinking 2 and burning out one. The attacks were carried out from 15000 ft under fire from the escorts.

I have no doubt the Norden could achieve almost as well.

Nor can I imagine the Norden and SABS 2 were ever compared apples to apples. The Americans bombed deep inland targets that could be hard to identify and only the lead bomber of the widely spread formation aimed. 617 squadron however had a clearly identifiable target in Tirpitz. No mistakes. However 617 bombing accuracy was terrible the month before under operation obviate due to the German fog cloud.

The Tallboy was a very precisely made and large dense supersonic armour piercing bomb resistant to deviations due to wind gusts that weighed over 10000lbs. The USAF was dropping 1000lb light case GP bombs with a blunt nose. The smaller slower falling bomb would have more manufacturing variation and be more effected by wind disturbances. The USAAF used CEP because the method of evaluation was to draw a circle of radius of the typical CEP with a compass around the aim point, count the total number of craters inside and if there wasn't 50% to slightly enlarge the circle and add in the additional craters till 50% of the total bombs were counted. If you want mean radial errors you have to individually measure distances from the crater to the aim point. Apart From being slow to evaluate it didn't make sense with formation drops nor provide an idea of bomb density. Most US CEP must have been form formation drops that covered hundreds of yards. In addition B-24/B-17 bombed from higher altitudes and the dispersion increases.

The MK 14 continuously told the bombardier where the bombs would fall as the aircraft manoeuvred allowing the crew to continuously adjust the flight path till the cross hairs were on target. It more or less worked like the Luftwaffe Stuvi 5B with BZA dive and slide bombing sight though it was the pilot the operated to Stuvi.

The SABS, Norden and Lofte 7 guided the aircraft to the release point upon which the cross hairs were placed.

I don't believe the SABS was superior to the Norden. In accuracy The Norden could have a supplementary device added that alllowed bombing during the climb or dive.

The German Lofte 7 was highly regarded. It was easy to maintaining durable and so tended to work and its optics could track the target much earlier than the Norden.

 

[stona]

I don't believe the SABS was superior to the Norden. In accuracy The Norden could have a supplementary device added that alllowed bombing during the climb or dive.
.

Nor do I, but the much vaunted Norden was no better which explains why the RAF rejected it when it was finally offered. The Mk XIV was considered to be the equal of the Norden by the RAF boffins, though I am unaware of any British comparative testing of the Norden and Mk XIV.

The RAF's 'precision' squadrons achieved better accuracy with the SABS and MK XIV than the USAAF achieved with the Norden. Of course those RAF squadrons were trained for precision bombing, but then so, theoretically, were all those USAAF bombardiers. Time and time again the reinforcement and repetition of the US doctrine of 'precision bombing' appears in all sorts of documents, and some officers ended up jumping through some very odd hoops to reconcile this with the bombing accuracy actually achieved, even in good visual conditions.

When Bomber Command looked at data for 57 late 1944 night raids against 'lightly defended' targets (like French marshalling yards, easily within Oboe range), it found the mean overall systematic error to be 300 yards and the mean random error to be 385 yards. The Mk XIV bomb sight was investigated as a possible source of error, but it was concluded that the device should give an accuracy of "about 130 yards" at 10,000 feet, that is only about 30% of the random error. The same report added that the SABS had an operational error of 120 yards at 10,000 feet (another report says 125 yards) and 170 yards at 16,000 feet.
For 'heavily defended' targets, a sample of six were analysed, all in Germany, the two errors rose to 1080 yards (systematic) and 1460 yards (overall average). The scientists felt the errors were weighted by the relative inaccuracy of the H2S marking used on one of the six raids. Clearly the error caused by the accuracy of the bomb sight used was a small percentage of the overall errors. Tactics and bombing techniques had a far larger impact on the accuracy of bombing than any error in the bomb sights used. The most critical factor in bombing accuracy was always the weather.

Cheers

Steve

 

[Koopernic]

Nor do I, but the much vaunted Norden was no better which explains why the RAF rejected it when it was finally offered. The Mk XIV was considered to be the equal of the Norden by the RAF boffins, though I am unaware of any British comparative testing of the Norden and Mk XIV.

The RAF's 'precision' squadrons achieved better accuracy with the SABS and MK XIV than the USAAF achieved with the Norden. Of course those RAF squadrons were trained for precision bombing, but then so, theoretically, were all those USAAF bombardiers. Time and time again the reinforcement and repetition of the US doctrine of 'precision bombing' appears in all sorts of documents, and some officers ended up jumping through some very odd hoops to reconcile this with the bombing accuracy actually achieved, even in good visual conditions.

When Bomber Command looked at data for 57 late 1944 night raids against 'lightly defended' targets (like French marshalling yards, easily within Oboe range), it found the mean overall systematic error to be 300 yards and the mean random error to be 385 yards. The Mk XIV bomb sight was investigated as a possible source of error, but it was concluded that the device should give an accuracy of "about 130 yards" at 10,000 feet, that is only about 30% of the random error. The same report added that the SABS had an operational error of 120 yards at 10,000 feet (another report says 125 yards) and 170 yards at 16,000 feet.
For 'heavily defended' targets, a sample of six were analysed, all in Germany, the two errors rose to 1080 yards (systematic) and 1460 yards (overall average). The scientists felt the errors were weighted by the relative inaccuracy of the H2S marking used on one of the six raids. Clearly the error caused by the accuracy of the bomb sight used was a small percentage of the overall errors. Tactics and bombing techniques had a far larger impact on the accuracy of bombing than any error in the bomb sights used. The most critical factor in bombing accuracy was always the weather.

Cheers

Steve

Very good clear data. I suspect there was very little difference between the SABS 2, Norden or Lofte 7 in terms of instrument error. What would make a difference is factors that automated the sight and reduced crew workload. This then alleviates the crew stress and time overload in combat. Post war bombers had Doppler radar to measure ground speed which was fed into the inertial navigation system from whence it was available to the bombsight. This would have eliminated the need to track a ground target and greatly alleviated crew workload. Storing bomb fall data in memory that automatically updates every factor also does this.

When the AZON bomb was used in Europe its accuracy was worse than free fall bombs. Under heavy FLAK the bomb aimer would end up making less corrections due to sensory overload and what was thought maybe would make a quick correction, hope for the best, and allow the pilot to take evasive action. There was some electronic records taken of the stick inputs. In the Far East acurate high altitude FLAK was less of a problem and the AZON could be controlled as planned.

The crews of 617 squadron were no doubt not only technically skilled they had the ability to execute their drill without being effected by massive stress and distractions. I wouldn't call it courage maybe resolve, moral certitude, pragmatism. Not sure. I knew a Swedish guy who could execute a somersault in a ski mobile skidoo. I asked how he learned and he said he built a ramp in his backyard and was fearless of getting hurt once he had worked out how to do it. I suspect he would have made a good bombardier. He had infinity girlfriends.

 

[stona]

I suspect there was very little difference between the SABS 2, Norden or Lofte 7 in terms of instrument error.

Probably hard to measure anyway, and being a very small factor in the overall errors measured operationally. Accuracies achieved by all these sights on peaceful bomb ranges were very different for those achieved operationally, with the exception of the SABS, but it was a very special case, used in a special way, and hardly comparable with the others which equipped the majority of the combatant bomber forces.

The British did test the Lofte sight and were impressed with it, though not enough to cause them to abandon or alter the Mk XIV (the SABS came along later).

Post war the RAF used developments of the Mk XIV/T-1 sight in its V-bombers. The SABS seems to have been a dead end, and as far as I know nobody has written a reference for it, nor do any exist in the public domain.

Cheers

Steve

 

[stona]

Apparently the figures taken from the analysis of those fifty seven raids on lightly defended targets are quoted in Wikipedia as definitive figures for the Mk XIV bomb sight. A perfect example of how data taken out of context and misused can lead to confusion and errors. The correct context for those figures is exactly as I posted above; they certainly do not represent definitive operational errors for the Mk XIV sight.
Cheers
Steve

 

[Zipper730]

They were about 10 years apart in timing.

And when you are talking about stopping nuclear armed bombers just how much "aid/help" to the pilots in ALL WEATHER conditions is too much or unnecessary?

I was talking about the philosophy of use of automation, not the technology being exactly the same

I am not overly impressed with SABS II or the supposed unique accuracy of 617 squadron in bombing the stationary and moored Tirpitz (Operation Catechism 12 December 1944).

Was SABS II better able to calculate the ballistics of bombs at supersonic speeds? I remember being told we had trouble calculating ballistics for bombs dropping at supersonic speeds?

Some of of the USAAF bridge busting raids using B-26 would have been equally impressive and certainly more important than sinking a crippled stationary battleship in Norway while Germany was surrounded on all sides.

I have no idea to be honest.

Neither sight had Ballistic data for the bomb. The bombardier used tables and dialled in bomb fall time, bomb trail error (compared to a bomb dropped in vacuum) and air speed.

Could we do this too?

 

[Cpt. John]

Ok, the ww2 USAAF bombing run was pretty accurate. Some bombardiers could be really accurate and hit the target with 80-85% of precision.Then the bomb sight, was vary good. I think was the best one in the 1940s.But at an alt. of 25.000ft it's very difficult to spot the target so , the man was everything, not the machine .Then , the istruments could help him to bomb it .

 

[stona]

Some bombardiers could be really accurate and hit the target with 80-85% of precision..

That doesn't mean anything at all. There is no such thing as a percentage of precision. The accuracy of bombing in good visual conditions, where the bombardiers could see the target with the Mk 1 eyeball, has already been posted in this thread.
Cheers
Steve