Bomber Losses: USAAF vs RAF

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OBOE had obvious limitations and the USAAF would have had to develop marking systems similar to Bomber Command,and probably a Path Finder Force to implement them.

Micro-H? Do you mean Gee-H? First used experimentally in November 1943, 50% of the bombs dropped fell within 750 yards of the target. It was much more accurate than GEE, H2S or OBOE, but still hardly pin point.
During April 1944, five more experimental raids were carried out, with a view to developing tactics for the system. An average error of just 275 yards was achieved, similar but not better than bombing by daylight in good visual conditions.

Now to the real world, and use of the system in mainforce bombing raids.
An analysis of GH attacks between October and the end of December 1944 showed that the average error of bomb distributions achieved was 1,172 yards, with an overall systematic error of 375 yards. 23% of aircraft made gross errors of 2,500 yards or over.

A final analysis in the first two months of 1945 showed that the average radial error was reduced to about 900 yards. That's the best G.H. could do for the British, who were far better trained and less resistant to using bombing and navigational aids than their US counterparts.

Micro-H was certainly not a navigational aid that could solve the accuracy problems of the strategic bombing forces.

Cheers

Steve
 
Koopernic said:
The safest and most accurate way to bomb would have been from a B17E at night from 33,000 ft using Oboe or the systems that followed it such as micro-H and could guide 50 aircraft at once.
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Discussions for use of Oboe by the USAAF were held in September 1943.

Options discussed were:
  • Oboe-less Oboe: using the Oboe ground stations, but without the Oboe set on board the aircraft. This would require a significant formation size, accuracy was yet to be determined, but the range was expected to be of the order of 100 miles - insufficient for USAAF use.
  • Mk I Oboe: This was the system in operational use by the RAF at that time. Transition to Mk II Oboe in the RAF was expected to begin within two or three months. Oboe would be carried in "leader" aircraft only. The RAF feared that Oboe fitted to a B-17 would survive being shot down, enough for the Germans to determine the frequencies, etc, and be able to jam it. Against this, it was noted that of the 460 8th AF bombers shot down to that point, only 3 "leader" aircraft had been shot down.
  • Gee-H: This was just coming into use by the RAF. It's accuracy was expected to be between Oboe and H2S. It was also believed to be much more susceptible to jamming than either Oboe or H2S.
After further discussions, it was agreed to release Oboe Mk I to the USAAF from October 1943, under the conditions that it be used only when weather requires its use, in formations of greater than 100 aircraft and that "destructors" be fitted to the equipment. It was also suggested that two Oboe sets be fitted to the lead aircraft, to give a measure of redundancy.

At the same time the Telecommunications Research Establishment (TRE) and US radar developers (MIT Radiation Lab) were soon to deploy 3cm versions of H2S (H2S Mk III and H2X/AN/APS-15 respectively).

I am unsure as to whether Oboe or Gee-H was ever used by the USAAF, since they adopted H2X early in 1944.

In both Gee-H and Oboe, the bomber had to fly a course at a constant radius from the base station. This, I am sure, would have been problematic for large aircraft flying slowly during daylight.
 
Peter Gunn said:
Interesting thought, so for the un-enlightened (i.e. me) can the E model cruise at 33,000 and if so, with what kind of payload?
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One of the requirements of "Oboe" use was operation at very high altitude to get the radar horizon needed. About 500km/ie 306 miles was reasonable for Oboe. A B17 could fly about as high as a Mosquito (Service Ceiling B17F about 37,000ft, so 33,000ft is achievable in the short ranges) so why not use the B17 which had a superior bombload to the Mosquito, certainly 6000lbs and possibly 9000lbs.

The best of the shelf aircraft would be the B-17F lightly stripped down. The B-17D had excellent performance, the B-17E lost performance because of the addition of the tail turret and the B-17F regained it because its engines had a 1340hp WEP rating and the B-17G lost masses of performance due to the chin turret and additional armour.

So the B-17F is best. Speed 318mph at 25,000ft, service ceiling 37,000ft bombload 9600lbs. It won't need a full load of fuel.
Boeing B-17F Fortress

Oboe was merely an evolution of the IFF transponders both sides used. Two ground stations interrogated (pinged ) transponders on the aircraft and this allowed the aircraft position to be precisely located as the intersection of two circles. Corrective commands were passed to the guided aircraft by using the same interrogating pulse ie long or short pulse to represent morse code.

This system was accurate because the timing circuits were in well developed ground stations and could be calibrated against known survey points on the ground.

There is nothing to stop one ground antenna being set up with multiple freqencies so that multiple aircraft could be guided at once. I'm thinking one would want to cover a squadron. I'm thinking about 12 aircraft.

Gee-H, called Micro-H in its american version worked on the same principles as Oboe but reversed the procedure by having the interrogating transmitters on the aircraft and the transponders on the ground. This meant the timing circuits had to be on the aircraft and they of course had to be simpler and less accurate. Nevertheless by using multiple frequencies and pinging randomely at randomely frequencies about 50 aircraft could measure their own position at once. The clashing pulses were simply filtered out since most pulses would be correct or because they came at the wrong time and represented a change in position that was not possible.

Here is my proposal. The aircraft will guide themselves then switch on their Micro-H or Gee-H systems about 15 minutes from target so that about 50-75 aircraft commence their preparation for bomb runs. About 5 minutes before target the aircraft will try to get the services of one of the 12 Oboe frequencies. It will try for 2 minutes and then cease. If it fails to be assigned to a Oboe frequency it will then complete its bomb run on Gee-H or Micro-H only. I'm allowing 12 Oboe frequencies to control 12 aircraft for a 5 minutes bomb run. This will allow just over 2 aircraft to attack per minute.

So why wasn't this done? Because the RAF wasn't thinking mass precision high altitude bombing very much and and had no sich aircraft whereas the Americans weren't think blind bombing electronic aids or night time bombing very much. The USAAF in fact borrowed its Norden from the USN who had developed the idea with Norden.

The technology was there but the thinking that would see it adapted was not. I'm suprised that blimps or Ballons weren't used to extend the radar horizon either.
 
The way the RAF operated was to use Oboe equipped aircraft as pathfinders, who would mark the target. The remaining aircraft would then bomb using the bomb sight.

The USAAF would bomb on the leader. The lead aircraft, plus a few replacements, would be fitted with the Norden bomb sight. They would identify and bomb the target. The remainder would bomb on that cue.

On a clear day the Oboe and Gee-H systems offered very little advantage. The Norden required an extended straight run into target, and Oboe would effectively require the same. Or worse - I'm not sure how long the aircraft had to remain on the circular track before target.

Which is something the Mosquito could get away with at night. It was as fast, or faster, than the night fighters sent to intercept them.

The USAAF were considering electronic navigation and aiming aids for situations where visual bombing was not possible - as I showed above.

In the end they decided on H2X over Oboe or Gee-H as their preferred non-visual bombing system.

Oboe's accuracy deteriorated with range. Simply because the same percentage error gives less distance error at short ranges than it does at long ranges. And the extra altitude also does not help with accuracy.

The RAF were experimenting with an Oboe Repeater system.

Here are some calculated results of the system.




 
The fundamental problem is that none of the systems being discussed were bombing aids, they were navigational aids. As such they were never accurate enough to achieve really accurate bombing. When bombing on H2X the 8th Air Force often achieved results no better those described for Bomber Command in the Butt Report, Bomber Command was significantly more accurate with the system (H2S).

Bomber Command used all the systems to get aircraft into the right area at which point various marking systems could be employed. All the systems had essentially two main variations. In visual conditions the marking would be done visually, the navigation aids use simply for...errr...navigation, and was consequently often much more accurate. Otherwise the marking was done 'blind' with target indicators being dropped using a position based solely on which navigational system was being employed. The marking was usually much less accurate.

The average deviations from intended aiming points using navigational aids to 'blind' mark were rather large. I posted that the RAF achieved an average error about 900 yards using Gee-H.

The 8th AF, using H2X in 1944/5, dropped 42% of its bombs more than 5 miles from the target and achieved an average circular error for those that fell within 5 miles, of 2.48 miles. In the last four months of 1944 the 8th AF dropped 81,654 tons of bombs using H2X of which just 674 tons fell within 1,000 feet of the aiming point. Put this into context, the much vaunted Oil Plan was supposed to be a series of 'precision' attacks on German oil facilities; in fact just 2.2% of the bombs dropped hit what the USSBS describes as 'damageable' buildings. 87.1% were 'spread over the surrounding countryside'.

There was no miracle navigation device which could solve the cultural and systemic problems which led such poor bombing. Further increasing the altitudes would certainly have made things even worse.
 
Waynos said:
Schräge Musik can't have been THAT much of a surprise as British protoypes were built with fixed upward firing guns not only in WW1 but also in the 20's and 30's so the concept was at least known.
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Interesting letter to the editor (Air International September1985) from Mr A S Foulkes. I hope the upload is readable...

 
Schrage Musik exercised the minds of the men who flew the bombers, particularly with hindsight, a lot more than it exercised those of the responsible men in Bomber Command at the time

Even when they became aware of Schrage Musik, losses to fighter attack were never categorised by the type of fighter attack. The principle factors affecting the losses to fighters were and always remained the weather and luck.

Bomber Command was not about to change the conformation of its aircraft, mounting ventral turrets or gun positions, even if this were possible. The H2S radar took the position of such a gun position on both the Halifax and Lancaster anyway. It would have involved a huge effort to mitigate what, harsh though it may seem, were a very small percentage of losses. More lives could have been saved by modifying escape hatches to open outwards rather than inwards, but even this relatively small modification was not deemed practical on aircraft already in service.

Much as Squadron Leader Foulkes might like to think that such remedial action could or should have been taken, the reality is that it was never seriously considered.

Cheers

Steve
 
The German night fighter crews tended to aim at an area between engine and fuselage which would tend to set the tanks alight. I read one night fighter pilots say they did this to give the bomber crew a chance to get out because the crew themselves weren't subject to direct attack. I would say not firing into the bomb bay was also a motivation? Surely the night fighter feared detonating the bombers load. Nevertheless this method of attack would have produced survivors and evidence on many occasion.

The best Defense would have been a practical tail warning radar or device. Obviously there was village inn and circuitry that was fitted to H2S.

German technology seemed to be evolving to blind fire using radar. A device called Elfe seems to have been in service.
 

Some of the American planes are as bad as the German ones for misleading information published in data sheets.

Chances of a B-17 making it to 37,000ft with 9600lbs worth of bombs is about zero.

empty weight is 34,000lbs however 40,437 pounds loaded is the weight the 37,000ft Ceiling is good for (maybe) .

In one test a B-17F at 39,300lbs was climbing at 100fpm at 36,600ft. Granted they were using climb power or max continuous and not combat power but if combat power is limited to 5 minutes and you are climbing at around 100fpm?

Even 2000 gallons of fuel is 12,000lbs . A B-17F in the low 40,000lb range is carrying a small bomb load and not much fuel.

Same plane was tested at 55,900lbs take-off, It took it 63.7 minutes to climb to 31,000ft running the engines at 2300rpm and max rpm the turbos were allowed. (it was later raised). calculated weight was 52,000lbs at 31,00ft at which point the climb was 100fpm. 5,600 feet less than the same plane (same serial number) flying at the lighter weight.

The way the planes were operated was NOT the way many lists of performance would have you believe. A B-17F at max cruise lean (not max continuous=rich) was using around 240 gallons an hour or 1440lbs an hour in level flight. Throw the weight of the crew, guns/ammo and oil onto the the 34,000lb empty weight and the amount of bombs you can carry even 3-400 miles while flying over 30,000ft starts getting rather small,

http://www.wwiiaircraftperformance.org/B-17/B-17F_41-24340_FS-M-19-1470-A.pdf
 
"Nevertheless this method of attack would have produced survivors and evidence on many occasion."

Roughly one man in ten survived being shot down in a Lancaster, not even one per crew. It was almost tthree in ten for the Halifax, but still not a great chance.

The problem is that it didn't produce evidence. Generally survivors IF they managed to escape and evade to return to the UK (which might take months via Spain, Switzerland etc.) had no idea how they were shot down. Very few aircraft survived a Shrage Musik attack, which by definition was a surprise attack, with cannon armament, at close range.
Evidence on how fighter attacks were carried out was largely gleaned from damaged aircraft which did return and this showed that most attacks were from the horizontal or only slightly below. The damaged aircraft seen by the ex Squadron Leader and described in his letter obviously wasn't one of those seen by boffins from Bomber Command's ORS.

The best way to defeat the night fighter threat was not to react to a particular threat posed by it, as in a new weapon system,but to use tactics and strategies to avoid the fighters making contact with the bombers in the first place. This covered everything from careful routing (away from night fighter beacons), split and spoof raids, to practical methods to jam the German radar systems and radio communications. A huge effort was made in all these areas.

Cheers

Steve
 
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The issues for 8th AF to convert to RAF Night Bombing doctrine were legion, both political and practical. The losses in Fall 1943 when the 8th began training with RAF, as well as equipping a B-17BG with H2S/H2X certainly began in earnest but several factors were in play:
1.) the logistics of training Pilots and Navigators in night navigation and bombing were daunting
2.) abandon formation flying, strip bombers of 1/2 armament and crew to increase payload
3.) integrate 800+ B-17/B-24 into airspace over East Anglia while avoiding RAF, including modification of Beacon/Buncher communication. Estimated loss rate to new strategy and tactics due to mid air collisions and take off/landing accidents were high (still looking for the analysis).
4.) weigh achievement of the objectives of POINTBLANK destruction of day fighter capability by changing to night bombing vs 'Stay the Course' and hope P-51B is solution, along with diverting all P-38J to ETO. By this time the performance was widely understood by Giles/Arnold and communicated to Eaker and Spaatz. Time was the issue confronting AAF leadership.
5.) P-51B's arriving in number beginning with late September deliveries, but experiencing similar operational issues with radios, etc
6.) organizational in-fighting between 8th and 9th AF on disposition of the Mustang.

Night bombing was never going to be adopted primarily because POINTBLANK/Overlord REQUIRED engagement with Germany's Day Fighter arm, and 8th AF combined with 15th were only combat units capable of the task..
 
The modifications to the Lancaster to increase speed would only be valid if the RAF only operated Lancasters. The Halifax had already been modified with more powerful engines and front turret removed to allow it to keep pace with the Lancaster in the bomber stream
 
To add to drgondog's post, the Americans never connected the need for escorts to daylight bombing operations before the war. As late as October 1941 a board was convened to discuss the future development of pursuit aircraft, and failed once again to perceive the issue with insight and clarity. A certain Colonel Spaatz passed up an opportunity to have 623 P-39s equipped with auxiliary fuel tanks in the interests of keeping aircraft design simple and maintaining high volume production.

In the absence of fighter escorts and undaunted by either the German or British conversion to night time operations in the face of unacceptable daylight losses, the Americans convinced themselves that the superior speed and armament of the B-17, along with the maintenance of tight formations, would avoid the troubles faced by European bombers. This became a central point of doctrine with an inordinate faith in the accuracy of the Norden bomb sight.

The British, due to their own grim experiences had no faith in the American's faith to conduct a daylight precision campaign against Germany. Both Churchill and Portal feared that the Americans would commit resources to a campaign which they could not carry out, and that as it failed it would be too late for a tactical volte-face.
The Americans had no interest in changing their plans. Initially the British were proved correct, but the belated arrival of escort fighters turned a looming American defeat into an unequivocal victory. The tactical volte-face was avoided.

Sir John Slessor spent the winter of 1941-42 in the US and he would write (to Sinclair)

"They [the Americans] have hung their hats on the day bomber policy and are convinced they can do it...to cast doubts on it just at present would only cause irritation and make them very obstinate."

He was right and the British let them get on with it. Early failures of the British night bombing and American day bombing campaigns very nearly derailed the entire concept of a combined bomber offensive, and it didn't matter who was bombing when.

Cheers

Steve
 

While the 2nd paragraph is essentially correct the first warrants a few comments.

Before the war, or even in the first year of the war, it was impossible to build an escort fighter for the B-17.
The B-17C first flew in July of 1940. It was rated as carrying 4000lbs of bombs 2400 miles. Now even if we cut that down to a 600 mile radius what in production 1940 fighter was available (or even close) to even try to escort in relays over that distance? This is 3-4 months after the first P-40 no letter is delivered. On August 30th 1940 the B-17E with power turrets is ordered, the prototype won't fly for a year. But the Air Force commanders know it is coming.
The Americans are handicapped by the Allison engine, in the improved versions ordered for the P-40D/E and the P-39s the critical height is about 12,000ft. Way too low to make a practical escort for bombers flying even in the low 20s.

In Oct 1941 things had not change a lot. The P-47 was in the works but still 8 months away from being issued to the first squadron.
there were 929 P-39s built in 1941 but just over 500 were built in the last three months (Oct-Nov-Dec) so doing anything to screw up production-Delivery might be justifiably seen as a problem.
And what do you get if you do modify the P-39? yes it is fast but it only holds 120 US gallons (100 imperial) so a drop tank isn't going to get you back from an escort mission. You need 12-16 gallons to warm up and take-off. you need around 2 gallons a minute at military rating (more at low altitudes) and we can forget WEP in 1941-42, it doesn't exist in command thinking of the time. 15 minutes worth of max continuous is worth 20-25 gallons depending on altitude and you need 10-12 gallons reserve once you hit the coast (whose coast? US or British or Pacific Island?) so you actually have 50-60 gallons at best once you have punched off the tank in enemy territory. depending on speed and altitude that is good for 220-300 miles on the range chart. Basically a P-39, even with a drop tank can't escort even to the German Border at any practical speed/altitude for getting home.
Now maybe you can pull the wing .30 cal guns and stick extra fuel out there ( there isn't any room in the fuselage) but the P-39 is running close to the wing loading of the Bf 109F , it can't out climb it and it can't out run it at most altitudes (if any).

I guess it depends on what you mean by "auxiliary fuel tanks", internal or external. With external tanks the P-39 was no more of an escort fighter than the Spitfire and since it's best altitude was thousands of feet below a Spitfire V it wouldn't have dome much good except to absorb bullets that might have been shot at the bombers.
SO what is the point?

The only hope in 1940-41 was the P-38.
 
Steve and Shortround both have good insight to the problem. To simplify the issues, the Material Command Never believed that a single engine fighter could be designed with both range AND acceptable performance. Eaker was a former Fighter Group commander and flew the Mustang I - and liked it. So, what? There was never a long range single engine fighter contemplated from US Industry. It wasn't until Ben Kelsey bootlegged an external ferry tank in secret collaboration with Lockheed to get P-38s equipped to fly to England in summer 1942.

Second problem and best known. There were zero two stage/two speed in line engines available for the Allies until the Merlin 61, so 1938-1941 had in-lines AND Radials totally dependent on Turbo superchargers to kick performance - and no US airframe save the Mustang had sufficient internal fuel to be considered, with only the obsolete p-39C w/170 gallons coming close.

Third, The dense and stupid Gen. Oliver Echols was so opposed to NAA Fighter program/Mustang that it took several interventions by Arnold/Giles to rub his nose in the performance reports coming in from RAF/RR Mustang X program. Arnold did approve the A-36 contract to keep NAA production alive in 4-42, but still approved the Xp-75 concept advanced by Echols/GM. That said, MC kept trying to convince NAA to install the 1650-1 because the installation risk was lower than Merlin 61 - It STILL was not conceptually understood that the P-51 mated with the internal fuel, external bomb rack/fuel tank, and the Merlin 61 was THE solution that fit Arnold to Giles directive to Solve escort problem by end of the year.

If you study the issue long enough you will realize that Barney Giles took command after Arnold recovering from heart attack, crystallized the issues, reviewed the deck, constructed the 'to be' (Internal fuel tank increase) and drove the Mustang into the spotlight. He stuffed Echols and the XP-75 as the preferred solution, but allowed the program to continue - but by that time the P-51B-1 was delivered and in serial production.

Could the P-51 have been delivered much sooner? NO. The first flight of the XP-51B was delayed 2 mo because Packard couldn't deliver satisfactory engine.The gating factor was supply of Merlin 61/1650-3. Couldn't import enough from UK (not physically possible, nor politically possible) and NAA had to wait for Packard to tool up, deliver test engines, survive the first several bench test failures at Wright Pat, and move into production. 20+ P-151B-1 airframes were compete save engines except for P-51B-1 43-12093 (#2) which flew May 5, 1943. The next airframe was delivered/accepted by AAF June 30.

The Packard Merlin delivery introduction of the Merlin 61 was the key 3+ mo delay to operational Mustangs in 8th AF. Coulda been there for Black Thursday but that was earliest.
 
The above post is why I keep logging on to this forum.
 
To further Bill's post I looked through AHT and found, if I did the math right, that the engine installation of the P-51B/C weighed about 2992lbs (individual aircraft may vary) this does NOT include the cowling (possible the engine mounts) or the fuel system but does include controls, starter, propeller, radiator and oil system (empty).
The book does not have the numbers for the Allison powered P-51, perhaps Bill does?
However the weights for the P-40E using the same engine as the early Allison Mustangs come to 2257lbs for the same parts/groups.

What makes this worthwhile and pertinent to this discussion, is that according to the charts, the V-1650-3 made about 1200hp at 25,000ft (61in MAP) while the V-1710-39 made about 600hp at 25,000ft. The powerplant in the P-51B/C made double the power while only going up about 33% in weight. It was this change in the power to weight ratio of the powerplant that made the escort fighter fighter possible.

The P-47 does come out better on a HP to weight ratio but needs much more fuel, has higher drag and little exhaust thrust making it much harder to compare.

One half of the powerplant weight of an early P-38 is 2539lbs for 1150hp at 25,000ft but that may not include any weight for the inter-coolers since they were the leading edge of the wing? Or the extra volume (drag) of fuselage needed to house the turbo system.

Reason for not including the fuel system is that the weight of the self sealing fuel tanks could vary tremendously with size and layout of the tanks.

There were sound technical reasons why single engine escort fighters were believed NOT to be possible in the late 30s and 1940-41.
Before somebody brings in the A6M Zero think about an A6M2 with it's single speed supercharger trying to fight BF 109Fs at 25,000ft.
The later Zeros with 2 speed superchargers (and much better altitude performance) don't show up until later and I have a lot of doubts about how far a Zero is going to go trying to fly at 22-25,000ft and at the speeds needed over Europe.

While the B-17 wound up NOT using it's speed due to the large formations, distances and bomb loads desired, it was conceived as a high speed aircraft at least when the turbos were added. An early B-17 could outrun a P-36 at 25,000ft by about 30 mph. and was roughly the same speed as a Hurricane I.
Granted 4 engine bombers rarely ran around at max speed but a B-17, not flying in formation, could cruise at about 260mph or better (on the pre "E") at 25,000ft using max lean (750hp per engine). Trying to build a single engine escort fighter with that kind of speed and altitude capability using the engines and fuel available in 1939-40 wasn't going to happen.

Checking other sources the Allison may have had 675hp or so at 25,000ft. the Merlin had 1330hp at 23,300ft , I doubt it lost 130hp in 1700ft. both figures without ram.
 
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drgondog said:
Could the P-51 have been delivered much sooner? NO.
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Let's not forget that the Mustang was considered a 'British' aeroplane and was being built to a British requirement for the British services. It took a bit of convincing to get the USAAC/F to buy into it. The First P-51s, i.e. built for US needs were diverted from RAF Mustang production.
 
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