Bomber Losses: USAAF vs RAF

[Shortround6]

Shortround6. In regards to B-17F service ceiling. You would have to admit that 9000m/30,000ft is a plausible attack altitude for a B-17F whose target is 500km/306 miles from the English coast.

10,000m/33,000ft is stretching it a bit but note that at a fuel consumption of about 1440bs/hour that less than 3600lbs is needed for the round trip after having achieved altitude over Britain and such a "B-17F" would be stripped of a moderate amount of weight, such as the waist gunners and the nose guns bar one 30 Caliber.

The Luftwaffe would be hard pressed to intercept in 1942 or even 1944. Ju 88R with their BMW 801 converted to run of Nitrous Oxide kits developed for the Ju 88S1 in the latter half of 1942 or Me 109 without radar but directed by Wurzbug radar. Both have severe operation limits.


The USAAF did have a escort fighter. It was called the P-38 and although it exhibited problems these were resolved. It at least shows a commitment to the escort fighter and the appreciation of its need even if the implementation was somewhat protracted.

There were three main problems with trying to operate B-17s at altitudes of 30,000ft and above and I am using the 30,000ft as a general benchmark, not something from official paper work.

There is a pilots manual for the B-17F available in the manuals section with lots of pages of charts.

A B-17F at 'basic' weight went 41,300lbs this included 9 man crew, 9 .50 cal guns (only one in the nose, none in radio compartment) 3500rounds of ammo, 900lbs of Misc. equipement, 144 gallons of oil and 1500lbs for the outer wing tanks.

6000lbs of bombs (pretty much internal max, the higher internal loads listed require 1600lb AP bombs of which only a few hundred were dropped in Europe, 7in steel Armour roofs being rather scarce. ) and 1728 gallons of fuel push the weight to 57,700lbs.
Manual shows weights and ranges for a variety of loads including a pair of 4000lbs external.

Charts vary on how much fuel was required for warm-up and take off from 132 gallons to 182 gallons???
there is another chart showing horizontal distance traveled and fuel used to climb to altitude at 5 different weights. at 55,000lbs it takes 150 miles and about 320 gallons to reach 30,000ft. There is a bit of cross over between the charts as the warm up and take off charts allow for climb out to 5000ft while the climb chart is from sea level.

There are 'tactical' range charts but they are calculated and assume the aircraft has been magically elevated to the desired altitude with warm engines/oil and there are no headwinds.

All of these charts or for a single airplane and not a formation. The larger the formation the more allowances that have to be made.

the 2nd point was that the airplane and crew simply could not operate at the higher altitudes as originally intended due to the temperatures. Temperatures from a chart in a different book (in Fahrenheit) are 20,000ft -12, 25,000ft -30, 30,000ft -48, 35,000ft -66.

This is for a 59 degree day at sea level, decimals rounded off. Guns, radios, instruments,etc. froze and did not operate, windows frosted over, cabin heaters and even electric crew suits didn't keep up with temperature drop and so on.

3rd was they found out pretty quick that bombing from 30,000ft wasn't anywhere near as accurate as they hoped. This was one of the main reasons which they canceled all the high altitude medium bomber projects.

 

[drgondog]

The USAAF did have a escort fighter. It was called the P-38 and although it exhibited problems these were resolved. It at least shows a commitment to the escort fighter and the appreciation of its need even if the implementation was somewhat protracted.

Koop - you are correct in the main. When performing to specifications, the P-38FG/H was the Best escort fighter combining range and overall high altitude performance in 1943. The problem is that the Intercooler design, the turbo limitations, the cockpit 'freezer', maintenance complexity, limited both operational availability at mission planning level as well as severe reliability issues in ETO high altitude ops.

The decision to re-route the 55th FG to ETO was made during Blitz Week in late July 1943 when the penetrations were daily and deep and the attrition rate steadily climbed above Q1 and Q2 levels. AAF planners were in a pinch on P-38 demand from Pacific and MTO and the P-51B-1 was just finishing first AAF Flight tests and advancing to Acceptance testing. The P-47D-1/-2 was just arriving with the aforementioned range issues in comparison to P-38. The 200 gallon tank breached the gap of forthcoming external 75/108 and 160 combat tanks - but none of the US fighters, including the P-51B-1 were yet modified to pressure the tanks in 1943 as a factory feature - leaving Col Hough and Service Command to their ingenuity.

So, the P-38G/H while the best on paper for the job, was not truly combat operational in context of reliability, mods to extend range (55 Gal LE Tanks), redesigned Intercooler/turbo system, dive flaps and boosted ailerons as a complete factory package for ETO until the P-38J-25 which only deployed to 9th AF in very late summer, 1944. The J-5/-10 mostly solved the turbo/engine reliability issue, the J-15 had the dive flap and production 55 gal LE tanks and kits were available for boosted flaps (but destroyed in FF incident by RAF en route to ETO in Dec 1943). The J, as modified in ETO, would have been excellent in fall of 1943. If the P-38J-10 w/LE tanks and dive flap kit had been available to say 5 FG in 8th AF in Jan 1944, it would have performed well for target escort - but probably never as effectively as the P-51B/C - in the ETO

 

[stona]

The tank tested, 8th July, up to 33,000' was pressurised somehow. The pressure never dropped below 15-17 psi. This is the one which was subsequently cleared for production in the UK

The unpressurised tank was only considered useful up to 25,000', this is the one of which 1,156 were already in theatre having been shipped from the US.

Cheers

Steve

 

[Koopernic]

There were three main problems with trying to operate B-17s at altitudes of 30,000ft and above and I am using the 30,000ft as a general benchmark, not something from official paper work.

There is a pilots manual for the B-17F available in the manuals section with lots of pages of charts.

A B-17F at 'basic' weight went 41,300lbs this included 9 man crew, 9 .50 cal guns (only one in the nose, none in radio compartment) 3500rounds of ammo, 900lbs of Misc. equipement, 144 gallons of oil and 1500lbs for the outer wing tanks.

6000lbs of bombs (pretty much internal max, the higher internal loads listed require 1600lb AP bombs of which only a few hundred were dropped in Europe, 7in steel Armour roofs being rather scarce. ) and 1728 gallons of fuel push the weight to 57,700lbs.
Manual shows weights and ranges for a variety of loads including a pair of 4000lbs external.

Charts vary on how much fuel was required for warm-up and take off from 132 gallons to 182 gallons???
there is another chart showing horizontal distance traveled and fuel used to climb to altitude at 5 different weights. at 55,000lbs it takes 150 miles and about 320 gallons to reach 30,000ft. There is a bit of cross over between the charts as the warm up and take off charts allow for climb out to 5000ft while the climb chart is from sea level.

There are 'tactical' range charts but they are calculated and assume the aircraft has been magically elevated to the desired altitude with warm engines/oil and there are no headwinds.

All of these charts or for a single airplane and not a formation. The larger the formation the more allowances that have to be made.

the 2nd point was that the airplane and crew simply could not operate at the higher altitudes as originally intended due to the temperatures. Temperatures from a chart in a different book (in Fahrenheit) are 20,000ft -12, 25,000ft -30, 30,000ft -48, 35,000ft -66.

This is for a 59 degree day at sea level, decimals rounded off. Guns, radios, instruments,etc. froze and did not operate, windows frosted over, cabin heaters and even electric crew suits didn't keep up with temperature drop and so on.

3rd was they found out pretty quick that bombing from 30,000ft wasn't anywhere near as accurate as they hoped. This was one of the main reasons which they canceled all the high altitude medium bomber projects.

A lot of interesting information.

My point was that it takes only 3600lbs of fuel to to a round trip of 1000km/612 miles at around 30,000ft. IE 300 miles to target plus 300 miles back. You can take of with a full load of fuel 20,000lbs, it doesn't matter, burn however much it off to get to 25,000ft and in the lightened state climb the additional 5000ft or more to get to 30,000ft plus. Then you start your mission to target. You'll even have 60 miles of gliding ability to count into the reserve for the return.

Surely getting rid of the waist gunners helps keep the cabin warm.

As far as accuracy goes. Radar bombing whether it was x-garaet or Oboe or Gee-H or Micro-H all gave an actual true speed over ground that allowed headwinds to be calculated and entered into the bomb fall calculation. The side ways crabbing I imagine was easy to calculate on x-garaet to give a cross wind and maybe Oboe as well. The main trick of the Norden was to calculate the wind drift of the bomber. If the electronics gives it to you all the better.

 

[fastmongrel]

the 2nd point was that the airplane and crew simply could not operate at the higher altitudes as originally intended due to the temperatures. Temperatures from a chart in a different book (in Fahrenheit) are 20,000ft -12, 25,000ft -30, 30,000ft -48, 35,000ft -66.

This is for a 59 degree day at sea level, decimals rounded off. Guns, radios, instruments,etc. froze and did not operate, windows frosted over, cabin heaters and even electric crew suits didn't keep up with temperature drop and so on.

3rd was they found out pretty quick that bombing from 30,000ft wasn't anywhere near as accurate as they hoped. This was one of the main reasons which they canceled all the high altitude medium bomber projects.

Hadnt the RAF already found out about these problems in 1941. Did the information from the RAF get to the USA and what did the USAAF and Boeing do to try and fix the problems. Also why hadnt this been found during tests in the US surely the temperature over a US bombing range at 30,000ft is roughly the same as over France.

 

[stona]

The theoretical accuracy of all these electronic aids, navigational or even the bomb sights themselves, were never represented in operational results, not even close.

The results of US 'radar bombing' are there in black and white for anyone who wants to look them up, I've even posted a brief summary in this thread already. They do not make for easy reading.

In early 1945 the 8th Air Force was still, occasionally, not just bombing the wrong targets but the wrong cities. They were not the only ones.

When Bomber Command used blind marking techniques their accuracy was rarely better than that achieved by the Americans bombing through cloud (equally blind). There were systemic reasons why the results were not quite the same, but it's splitting hairs.

Cheers

Steve

 

[stona]

Also why hadnt this been found during tests in the US surely the temperature over a US bombing range at 30,000ft is roughly the same as over France.

The Norden was broadly designed to operate in the 20,000' range. I'm unaware of any testing done in the US at much higher altitudes.
From 20.000' it was supposed to be able to achieve a CEP of just 50' and some bought into this myth. It fitted with the precision doctrine and the 'key node' targeting theory developed by the Americans. In an almost 'cart before the horse' way, through the mid/late 1930s, the Norden sight provided impetus to this doctrine and theory. Stephen McFarland's 'America's Pursuit of Precision Bombing' is a good source of information on the development of American doctrine.

In fact intrinsic errors in the sight itself meant that in 1944 75% of sights tested would only have been capable of a CEP of 280' from 20,000'.

Cheers

Steve

 

[Shortround6]

A lot of interesting information.

My point was that it takes only 3600lbs of fuel to to a round trip of 1000km/612 miles at around 30,000ft. IE 300 miles to target plus 300 miles back. You can take of with a full load of fuel 20,000lbs, it doesn't matter, burn however much it off to get to 25,000ft and in the lightened state climb the additional 5000ft or more to get to 30,000ft plus. Then you start your mission to target. You'll even have 60 miles of gliding ability to count into the reserve for the return.

Surely getting rid of the waist gunners helps keep the cabin warm.

As far as accuracy goes. Radar bombing whether it was x-garaet or Oboe or Gee-H or Micro-H all gave an actual true speed over ground that allowed headwinds to be calculated and entered into the bomb fall calculation. The side ways crabbing I imagine was easy to calculate on x-garaet to give a cross wind and maybe Oboe as well. The main trick of the Norden was to calculate the wind drift of the bomber. If the electronics gives it to you all the better.

From the Flight Operation instruction charts in the Manual for the B-17F,
600 gallons (3600lbs) will get you 600 miles at 30,000ft IF you are flying at 144mph IAS (230 true?) AND your gross weight is between 45,000 and 50,000lbs.
The chart for 50,000 to 55,000lbs gives a range of 500miles for 600 gallons.
In the first case the engines are running at 2050rpm, 30 in MAP and using 216 gallons an hour,
In the 2nd case the enignes are running at 2100rpm, 31 in MAP and using 251 gallons an hour.
Speed has dropped to 141 IAS.

B-17 waist guns went though at least 4 different set ups. This was maybe number 3??

There was a hatch that slide or hinged out of the way when in a combat area, please note the pop out wind deflector in an attempt to keep air currents from affecting the gunners aim, even if it didn't do much to keep him or the tail gunner warm.
Later B-17s got a Plexiglas window

This is the waist gun on the Version the British first used? or movie version?

getting usable waist guns was an ongoing evolution, not a "we tried that, forget it" situation.

Problem with bombing from 30,000ft (or any high altitude) is that while you may know what the wind is doing at the altitude you are flying at by measuring plane drift or even by electronic monitoring of planes position over time you have no idea of what the wind speed and direction is at intermediate altitudes. Bombing from 20,000ft cuts down (but sure doesn't eliminate) the possible errors.

While not bombing I once was at a 600yd rifle match where there were 3 range flags flying from poles to give indications of wind direction and strength. One was pointing to the right, one was point left, one was hanging limp and there was a small dust devil in the parking area alongside the range. What wind value do you set on your sight

 

[fastmongrel]

What wind value do you set on your sight

You need a pair of these

 

[stona]

I've had a chance to flick through the book mentioned above, and it makes for depressing reading.

Between 1930 and 1938 the Air Corps dropped over 200,000 bombs in training. The overwhelming majority of these drops came from 4,000 feet to 11,000 feet. Less than three percent came from above 16,000 feet. The Air Corps had no idea how their best bomb sight would perform from, say, 24,000 feet! The highest altitude included in the tables is 15,000 feet.
This data was used by the Air Corps Tactical School (ACTS) for creating the probability studies on which bombing doctrine was based.

I can't reproduce the whole tables here, but to give an idea of the accuracy calculated.
A B 17 flying at 135 mph was expected to achieve a radial error of 107 feet from 7,000 feet, or 144 feet from 10,000 feet.

Using these tables a study evaluated the requirements for destroying the Sault Ste. Marie locks between Michigan and Ontario (Lake Superior and the Lower Great Lakes). The conclusion was that nine 300lb bombs, carried by one medium bomber could do the job. It was this sort of study on which US bombing doctrine was based.

This was the mind set with which the Americans came into WW2 in Europe. It was deeply flawed, they honestly believed that would not bomb from 10,000 feet at 135 mph, and it would require one medium bomber and nine bombs to destroy targets similar to those in the study.
The reality was that they would be forced to bomb from in excess of 20,000 feet, attacked by fighters and flak, in poor conditions. It would require hundreds of bombers and thousands of bombs to destroy most targets. Often hundreds of bombers and thousands of bombs would fail to destroy the target.

Cheers

Steve

 

[Shortround6]

I would say in defence of the US planners (and it is a very poor defence) that many other nations did the same sort of thing/s although perhaps to a lesser extent. The Germans/Japanese/Italians at least having some sort of war experience to reign in the wilder ideas of planes/bombs needed to get certain target effect/s. Although they too vastly over-rated both bomb effectiveness and accuracy.

Of course targets also varied, Chinese cities of the 1930s being constructed much different than european cities let alone modern factories.

 

[stona]

I would say in defence of the US planners (and it is a very poor defence) that many other nations did the same sort of thing/s although perhaps to a lesser extent.

It's a valid defence, everybody got the science of bombing seriously wrong in the inter war years.

What is less excusable is the tenacity with which the Americans held on to their doctrine in the face of the overwhelming evidence, supplied by the British and German experiences between 1939 and 1941, that it was deeply flawed.

Again, this was not an exclusively American failing, all the other combatant nations did something similar, but some did learn quicker than others.

Cheers

Steve

 

[stona]

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.

Oblt. Heiz Roekker, St.Kpt. of 1./NJG 2 would support that contention.

"At the beginning of 1944 upward firing guns (Schrage Musik - slanting music) were installed on our Ju 88 C-6s and R-2s. They were mainly two MG FF or two MG 151 firing at 70 degrees upward and operated by the pilot. The reflector sight was above him in the cabin roof. Although finding the enemy remained as difficult as ever, the actual shooting down was made considerably easier. Once a four-engined aircraft had been found, the Abschuss was almost 100 percent certain.The fact that aircraft flying below one's own level cannot be seen at night meant that the night fighter, some 100 metres below his enemy, had plenty of time to match his speed to that of his victim and follow his movements without being noticed. From below he also has a much larger target before him. My method was generally to aim at the port or starboard trailing edge of the wings and as I opened fire to push my nose slightly down, sending the burst forward through the wing, the fuel tanks and engines. The wing would then burst into flames at once. Swinging off to one side would take one out of the danger area, for one had to reckon with bomb jettisoning and explosions. I believe that this tactic enabled many of the seven man crews to escape by parachute as the fuselage itself was not usually hit."

There is no evidence that more men managed to escape from a bomber destroyed in this way than any other. Basically the chances of escaping a burning and out of control bomber were not good. An analysis of four raids on Hamburg showed that of the 39 Lancasters and and 275 men shot down just 8 men survived (2.9%)! Overall the average odds were slightly better, 13.2% of Lancaster crews survived being shot down, 21.9% for the Halifax. being shot down over Germany or occupied territory gave a slim chance of survival and an even slimmer one of making a return. A man in a PoW camp can't provide useful intelligence to the RAF, and even those who did return rarely knew how they had been shot down.

Cheers

Steve

 

[Jim Daigneau]

Fantastic discussion! In regards to fuel usage, the fuel used stated for power settings assumes steady power. The lead aircraft would achieve those figures but tail end charlie or the guys on the end of the whip would have used more fuel trying to keep position. For shorter missions probably not too big an issue but on the max range missions, the different fuel usage could mean the difference of making it to base or landing short somewhere (hopefully, not the Channel).
(Basis for statement: 3500 hours in A-4s, A-6s, FA-18s and F-16s. So I'm not a bomber guy. Don't hate me.)

 

[Zipper730]

Yes and no. The RAF tried high-altitude daylight precision bombing with Fortess I's (B-17C) in early 1941. These raids were carried out unescorted at 30,000ft, and were disastrous - not just because of combat losses, but because the aircraft really weren't up to the task and the crews were not trained or equipped for high-altitude work.

Can you clarify what you mean by "not trained or equipped for high altitude work"?

Ironically, the USAAF had told the British that the B-17C was not sufficiently well-armed for unescorted bombing over Europe, and they were dead right. When the B-17E and -F came along, the USAAF promptly ignored it's own advice in 1942 and Schweinfurt ensued.

The B-17E and F were way better armed than the -C. That said, they still weren't adequate for self defending operation.

On the Army Air Force site it says the USAAF lost 5,548 heavy bombers. . . their losses were actually quite lower than the RAF night bombers, which was 10,000 night bombers lost.

Holy cow, I thought we'd have lost more...

Switzerland had dozens of Allied heavy bombers parked on airfields by the end of the war. Some of them landed on purpose to opt out of the war.

Do you have anymore on that?

H2S and Monica radars were not critical to finding the targets, and in the case of H2S it was manifestly mis-used.

Which means that GEE, or Oboe should have been used most of the time with H2S used in the proximity of the target to make sure they're where the radio navigation aid says they should be before they continue to release ordinance?

However, it was felt by the brass in England that the bombers needed the ability to guide themselves onto the target

Was this because they were concerned with a malfunction or spoofing?

"Oboe used two stations at different and well-separated locations in England to transmit a signal to a Mosquito Pathfinder bomber carrying a radio transponder. The transponder reflected the signals, which were then received by the two stations. The round-trip time of each signal gave the distance to the bomber.

Each Oboe station used the radio ranging to define a circle of specific radius, with the intersection of the two circles pinpointing the target. The Mosquito flew along the circumference of the circle defined by one station, known as the "Cat", and dropped its load (either bombs, or marking flares, depending on the mission) when it reached the intersection with the circle defined by another station, known as "Mouse". There was a network of Oboe stations over southern England, and any of the stations could be operated as a Cat or a Mouse as the need demanded.

The description, I'm not sure I mentally wrap my head around that... are you talking about each transmitter producing a ripple of energy and the intersection between the two ripples being the correct flight path? Or are you describing something else, and are there drawings one can find online?

The initial "Mark I" Oboe was derived from Chain Home Low technology, operating at 1.5 meters / 200 MHz. The two stations emitted a series of pulses at a rate of about 133 times per second. The pulse width could be made short or long so that it was received by the aircraft as a Morse code dot or dash. The Cat station sent continuous dots if the aircraft was too close and continuous dashes if the aircraft was too far, and from these the pilot could make the needed course corrections.

Various Morse letters could also be sent, for example to notify the aircraft crew that the Mosquito was within a specific range of the target. The Mouse station sent five dots and a dash to indicate bomb release.

So -.- or .-. indicated you were on course, .....- means "drop bombs"?

Along with the range restriction, an earlier system called Oboe, had another limitation: it could only really be used by one aircraft at a time. As a result, the British rethought Oboe, and came up with a new scheme named G-H (also given as "GEE-H") based on exactly the same logic, differing only in that the aircraft carried the transmitter and the ground stations were fitted with the transponder. In this manner, it operated in a similar manner to the currently employed civilian DME system, with the aircraft following a DME arc procedure on one set, whilst using another set (tuned to a different transponder as close to 90 degrees apart as geography permits) to determine the point of bomb release.

I didn't know GEE-H was a blind-bombing aid, though I knew you could guide 80 aircraft with it.

 

[stona]

The 10,000 RAF bombers lost needs some qualification.

Operational losses for all Bomber Command aircraft were 8,953. That includes everything from Lancasters and Halifaxes to Blenheims and Whitleys.

There were a further 1,368 aircraft lost in operational crashes.

That gives a total of 10,321 for what are deemed operational losses.

It is important to remember that Bomber Command commenced operations over Europe in September 1939, whereas the USAAFs did not start such operations until several years later.

Cheers

Steve

 

[Milosh]

Slightly different numbers than what Steve posted.

Aircraft Type : Operational Losses by Night and Day
BC - Statistics

Summary Of Operational Statistics
Total Aircraft Lost 8,655 (2.58%)

In the ETO the Americans lost 6592 heavy bombers and 1553 medium and light bombers (total 8135).
Army Air Force Statistical Digest: World War II

 

[stona]

Operational crashes, defined as aircraft which crashed in the UK while inward or outward bound on operational missions should be included in the total. How many of these aircraft were destroyed or written off is impossible to say.

Cheers

Steve