B24 ceiling vs. B17 ceiling

[Glider]

A small but often overlooked action that implied that the B17 had an advantage was the decision around May 1944 for the 8th airforce to remove the ventral turret from B24's. This was done to improve performance and handling at altitude. To the best of my knowledge this didn't happen to B17's.

 

[Shortround6]

THE FORTY-FOURTH HARMON MEMORIAL LECTURE IN MILITARY HISTORY, The Aircraft that Decided World War II: Aeronautical Engineering and Grand Strategy, 1933-1945, The American Dimension John F. Guilmartin, Jr. United States Air Force Academy 2001

B-17 (pp.17-20 of 44)
The Boeing B-17 Flying Fortress was the anvil against which the USAAF fighter force hammered the Luftwaffe fighter arm to destruction in the skies over Germany. for the quality of its design............................

That is some of the god awful crap history that one expects from PR flack.
It is hard to say that most of it is actually false considered one sentence or part sentence at a time but it makes more twists and turns through story than a long program figure skater.

The B-24 did have problems and it a number of ways it was not as good as B-17, but the actual differences/problems are glossed over with too much of the Boeing and the Army made all right choices right from start start narrative. Granted the author may have been trying to keep word count down or actual research may have taken too long.
Boeing 299 used P & W engines.
Wright redesigned the R-1820 three times from the Y1B-17 to the B-17C.
The 1st B-17 to get a turbo was the 13th Y1B-17 and it was only available for installation after it was decided to complete it as a flying airframe instead of a static stress test rig after serial number 36-157 got tangled up with a thunderhead and wound up in an inverted spin and recovered.
All of the record breaking/news reel flights of 1938 ( east to west and west to east trans-continental flights, formation flight to Rio, intercepting the Rex) were done with non-turbo equipped Y1B-17s.
On September 13, 1935, Howard Hughes set a world speed record using 100 octane fuel (P & W engine). Every engine maker knew 100 octane was coming, they just didn't know when. But apparently the Army gets the credit?

Changes in the B-17 defensive armament seems to gotten fast forward. B-17E had two power turrets/mounts. It showed up in 1941, not 1942.
The famous 13 .50 cal guns tends to over look a few things. Like the radio operators gun have a rather narrow firing arc and even worse vision.
Also over looked is the fact that if you actually want to use all 13 guns you have to have 3 men stuffed in the nose and an 11 man crew.
Totally skipped over is the time it took to get to the Cheyenne tail gun mount in all the self congratulations.

It there is also some question about
" Another was the development of the turbo supercharger by General Electric on an Air Corps contract, the only discrete Army research and development program to receive funding through the Great Depression. "
May depend on when the author defines the great depression was and what discrete means. The Army was certainly funding the hyper engine program from 1930 on which in most peoples minds was during the Great Depression.

And this mess,
"American military aircraft would henceforth be powered by engines designed for civilian use, and while high altitude performance had obvious military importance it had little civilian value. The European solution, gear-driven superchargers designed as an integral part of the engine, was an obvious non-starter for economic reasons.27 The military market was simply too small. American superchargers therefore would be add- on accessories and the only evident way to power such a supercharger was a turbine driven by engine exhaust gasses. "

Author apparently doesn't know the difference between single stage and two stage superchargers or he does and doesn't think his readers know the difference.
Also rather ignores the US Navy and P & W working on two stage gear driven supercharges.

 

[Simon Thomas]

The airfoil used by each was quite different. The symmetrical section on the B-17 was a rather poor choice. The Davis airfoil was far better wrt drag than the symmetrical section.

 

[33k in the air]

A small but often overlooked action that implied that the B17 had an advantage was the decision around May 1944 for the 8th airforce to remove the ventral turret from B24's. This was done to improve performance and handling at altitude. To the best of my knowledge this didn't happen to B17's.

That was also due to a statistical analysis showing the ventral turret engaged enemy fighters the least, From what I recall reading, the choice to remove the ventral turret was left up to each bomb group; some did remove it and others didn't.

In the B-17, the radio room gun was dispensed with, since it contributed little to aircraft defense, and only one waist gunner was carried.

The B-24 did have problems and it a number of ways it was not as good as B-17, but the actual differences/problems are glossed over with too much of the Boeing and the Army made all right choices right from start start narrative. Granted the author may have been trying to keep word count down or actual research may have taken too long.

From an operational and logistical perspective, switching to only one type of heavy bomber for the 8th AF made sense, since it would streamline things.

 

[Geoffrey Sinclair]

The examples for why the "real killers of bombers are fighters", if ground fire was as deadly then there should be similar examples of high losses inflicted by the guns at heavy bomber altitudes. Where fighters were active and able to intercept, from Mighty Eighth War Diary

13 June 1943, Kiel raid, 76 sent, 60 effective, 22 lost, 1 written off.
While the second Schweinfurt raid is noted for its losses, the raids of 8 to 10 October had cost 88 MIA and 8 written off.
11 January 1944, Oschersleben raid, 177 sent, 159 effective, 34 lost, 2 written off.
22 February 1944, Aschersleben raid, 289 sent, 181 effective, 32 lost, 4 written off.
24 February 1944, Gotha raid, 239 sent, 213 effective, 33 lost, 1 written off.
6 March 1944, Berlin raid, 730 sent, 672 effective, 69 lost, 6 written off.
18 March 1944, Friedrichshafen raid, 227 sent, 198 effective, 28 lost, 3 written off.
11 April 1944 raids, 917 sent 826 effective, 64 lost, 5 written off.
29 April 1944, Berlin raid, 679 sent, 618 effective, 63 lost, 2 written off.
12 May 1944, Zwickau raid, 295 sent, 258 effective, 41 lost, 1 written off.

Medium bombers tended to operate above the light flak ceilings.
17 May 1943, the 322nd Group B-26, 11 aircraft low level mission to Holland, 1 abort, remainder shot down by fighters, flak and collisions avoiding hostile fire.
23 December 1944 the 391st Group B-26 versus Luftwaffe fighters, 16 B-26 lost, over half the force. The Luftwaffe fighter threat to the allied light and medium bombers stopped well before the threat to the heavies, more so as the light and medium bombers were usually operating with an escort from the start.

flak was the best killer of airplanes and was equal to fighters as a bomber killer for heavy bombers and the best at it for everything else.

Flak was present for the entire ETO air campaign and in fact increased in density over time, the threat from German fighters decreased markedly from June 1944 onwards. In bombs dropped on Germany terms and therefore sorties the 8th Air force hit its half way point in mid November 1944. If you want to use the for campaign figures like that then consider the USN aircraft carrier landing system was a much more effective weapon for the Japanese than their fighters were against the USN carrier based aircraft.

I flat disagree with "loss rates go up with time spent in hostile airspace." This was WWII, not modern warfare.

Whereas I note the longer you are tracked the more likely you are to be intercepted, plus there were so many flak guns in Germany 1944/45 that it was very hard to avoid being shot at flying to and from the target and easy to make a small navigation mistake that put you over a defended area. Navigation errors go up with distance. As the Swiss found out a few times.

If you take 31 August 1944 as the date the continental airfields became available to take damaged allied heavy bombers then the following figures apply for the 8th Air Force. In the period to 31 August 1944 some 2.7% of B-17s listed as lost to fighters made it back to allied territory, versus 6.4% of those listed as lost to flak. For the period 1 September 1944 to the end of the war the figures become 5.8% and 16.6%.

I have spent about 20 years around WWII warbirds. Their engines are reliable to the point of being almost laughably reliable.

Some of the 1945 15th Air Force monthly reports have Engine Change Reports, graphs of average running time per aircraft engine changed. Generally speaking the R-1830 radials in the B-24 and the R-1820 radials in the B-17 had at least an average of 300 hours running when changed, few had 400, with the R-1820 ahead, most having 350 or more hours. Overhauled engines usually had around half the average hours of new engines. The V-1650 Merlins and the V-1710 Allisons usually averaged over 200 hours, few made it to 300 until March/April. Overhauled Allisons were around half the new engine hours, overhauled Merlins more like a quarter. Post war commercial R-1820s and R-1830s were normally racking up TBOs of about 1500 Hrs. Wat are the TBOs these days?

The 15th Air Force target and duty sheets I have often record the altitude the bombs were released at, the maximum was 32,000 feet by a B-17 group, the highest recorded B-24 altitude was 27,000 feet, it is the only B-24 entry of 26,000 feet or higher, versus the 120 B-17 entries. Lowest bombing altitude, assuming no mistaken entries, was 2,300 feet, then one at 3,500 feet, all other entries are 11,000 feet or higher.

We ran 50+ sorties a day for 3 days once a year. That's 1,500+ sorties. We had a grand total of 5 aborts during those 10+ years.

How many were 4 engined bombers? The 8th Air Force ones had a 4.2% mechanical abort rate. How many sorties in bad weather? The 8th Air Force had a 9.1% weather abort rate. The USSBS weather report notes in cloud cover terms the forecasts were correct 302 times in 524 raids. The B-17 were better able to fly above bad weather. The 9th Air Force P-47, 201,546 sorties, of which 11,096 were non effective or 5.5%, broken down by cause 5,418 weather, 244 personnel, 3,322 mechanical and 2,112 other causes. Have you done a study to discover why your abort rates are so much less than the wartime ones? So you are sure you are comparing like with like, like available maintenance facilities, stresses put on the aircraft? Mission requirements? Total flying times? Operational tempo?

Weather is a factor only when it is extreme. Flying in clouds won't make you crash unless you have a midair, which is unlikely in formation but more likely in combat.

Even in formations as tight as the 8th Air Force heavy bombers? The night bombers could operate in worse weather as they were not trying to fly in formation.

------

If Roger Freeman is correct in May 1944 the 1st Division started a policy of removing the radio room gun and one waist gunner from its B-17s, mainly for centre of gravity reasons, both waist guns were retained though. In March 1945 the 381st group was flying without ball turrets, the 91st without waist guns or gunners, the 398th without chin turrets and the 94th without chin and ball turrets. The 398th liked the performance increase. In June 1944 the 8th Air Force HQ gave permission to remove the ball turrets from its B-24s, it was a decision left to the groups so some removed the turret and others kept it.

-----

"THE FORTY-FOURTH HARMON MEMORIAL LECTURE IN MILITARY HISTORY,… The Boeing B-17 Flying Fortress was the anvil against which the USAAF fighter force hammered the Luftwaffe fighter arm… The B-17 was a singular design for which there would have been no viable substitute until the B-29… Even before long range fighters were available to escort deep penetrations, massed formations of B-17s took a significant toll of the Luftwaffe fighter arm. the B-24 was nonetheless inferior to the B-17 in every critical performance parameter that counted in the European theater of operations save maximum range… the study showed that four engine bombers were significantly more accurate than twin engine bombers across the board."

If the anvil is correct the Luftwaffe was ignoring raids done by B-24, which would make the B-24 far better than the B-17, zero air to air losses. The 8th Air Force concluded the B-17 was better for it but the results show the B-24 could have been used instead. The USAAF Statistical Digest notes the ETO lost 599 heavy bombers to fighters to end October 1943 and the MTO 166. Assuming a 1 to 1 kill ratio, that makes it 765 Luftwaffe fighters, but the 1943 exchange rate is more like 3 bombers to 2 fighters, so around 500 fighters shot down. Note the critical parameters are not listed in the article, which is a flag that opinion is being used.

Remember when it comes to bombing accuracy at some point you have to decide the miss is so great the bombers were in fact attacking a different target. The raid on Huls (22 June 1943, 224 B-17s despatched plus 11 YB40s, 183 attacked 15 B-17s and 1 YB-40 lost) is a prime example of a USAAF raid that caused heavy damage. After the raid the bomb craters were found over an area of 12 square miles, 20% of the bombs dropped hit the 541 acre (0.84 square miles) site. If the site were a square then each side fence would be 4,650 feet long. In 1943 one strike on the Focke-Wulf factory at Marienburg, 598 500lb bombs were dropped, 286 fell in the factory area and at least 35 hit buildings, 5.8% accuracy if the analysis is correct, this was considered a substantial improvement in the accuracy shown so far. Note that while many bombs fell close most still missed.

The USSBS bombing accuracy reports the B-17 was more accurate than the B-24, but of course the medium bombers were more accurate than both, the direct result of bombing from lower altitudes. In any case the difference in B-17 versus B-24 accuracy was small compared with the other factors. The 15th Air Force was more accurate than the 8th as it was able to do more training on the electronic bombing aids. Being the first formation over the target gave you 82% accuracy, being the fifth meant 30% accuracy, attacking a 1,000 foot target a 9 wide aircraft formation scored 100, 6 wide formation 110.6, and a 3 wide formation 142.2. Turn up with 3 bomber boxes and bomb from 10,000 feet the expected circular error was 570 feet, using 15 boxes 765 feet, 3 boxes at 25,000 feet error 1,047 feet, 15 boxes 1,242 feet. In the final four months of 1944 the 8th Air Force bombs within 1,000 feet of the aiming point, 30% in fair to good visibility, 9.4% in poor visibility, 5% using GH, 5% using Micro H, then using H2X in, 4 to 5/10 cloud 4.4%, 6 to 7/10 cloud 2%, 8 to 9/10 cloud 1%, 10/10 cloud 0.2%.

The B-17 was a better aircraft to fly in and pilot than the B-24, it was more reliable and more accurate a bomber but the differences between the two types as used in Europe were much smaller than the other factors involved, like the chances of being intercepted, flak and smoke defences, sighting methods, formation tactics, training time, weather effects and the size of the attack.

Engage smiling systems before proceeding. "no viable substitute" Say in round terms the 8th Air Force had 1,000 fighters and 2,500 bombers, when you look at the dollar cost of aircraft and the manpower in the combat units you discover the ratio is 3.5 P-51 to 1 B-17. If you want a back of envelope total hindsight 8th Air Force and assuming the Lancaster follows this costing then change the 8th Air Force to 1,500 Lancasters and 4,500 P-51. The average Lancaster bomb load was 10,065 pounds versus the average B-17/24 load of 5,194 pounds, so average bomb lift becomes 7,500 versus 6,500 short tons and able to drop the more destructive larger size bombs. The P-51 pilots then rotate the three missions, sit beside your pet Lancaster all mission, standard 8th Air Force escort and look for trouble in the area around the bomber force. If you want altitude performance consider the Lancaster VI with two stage Merlins, with only a rear turret fitted it had a top speed around 345 mph which translated to cruising speeds comes close to the fighter cruise speeds and should cut about an hour out of any mission to Germany with associated decreases in interception chances and winter daylight problems. Perhaps fit a pair of forward firing machine guns under pilot control to counter head on attacks. Adjust according to preferences, 100 bombers to 350 fighters one up, the other down.

 

[GregP]

But that didn't happen all the time, which is the point. You'd have to show in the bombing missions a substantive difference in targets assigned; I highly doubt going through something like Roger Freeman's Mighty Eighth War Diary would show any such meaningful difference in the aggregate.




It should be noted the aggregate does not reflect the change which occurred over time. Flak became more of a threat as the enemy fighter force was reduced in number and capability.




Are these warbirds being operated at anywhere near their typical combat gross weights? Are these warbirds being operated regularly at their typical combat altitudes? Are these warbirds being regularly operated in mediocre to deteriorating weather combat missions often were? Are these warbirds being operated routinely for the lengths of time that a single mission during the war required? Are these warbirds being operated at anywhere near the frequency at which wartime aircraft were operated for sustained periods of time?

What was the typical serviceability rate for USAAF bombers and fighters in the ETO?

Flak was ALWAYS a threat. You can't see it coming or do anything about it. Flak got better as the war went on, too, just as fighters did.

 

[GregP]

That is some of the god awful crap history that one expects from PR flack.
It is hard to say that most of it is actually false considered one sentence or part sentence at a time but it makes more twists and turns through story than a long program figure skater.

The B-24 did have problems and it a number of ways it was not as good as B-17, but the actual differences/problems are glossed over with too much of the Boeing and the Army made all right choices right from start start narrative. Granted the author may have been trying to keep word count down or actual research may have taken too long.
Boeing 299 used P & W engines.
Wright redesigned the R-1820 three times from the Y1B-17 to the B-17C.
The 1st B-17 to get a turbo was the 13th Y1B-17 and it was only available for installation after it was decided to complete it as a flying airframe instead of a static stress test rig after serial number 36-157 got tangled up with a thunderhead and wound up in an inverted spin and recovered.
All of the record breaking/news reel flights of 1938 ( east to west and west to east trans-continental flights, formation flight to Rio, intercepting the Rex) were done with non-turbo equipped Y1B-17s.
On September 13, 1935, Howard Hughes set a world speed record using 100 octane fuel (P & W engine). Every engine maker knew 100 octane was coming, they just didn't know when. But apparently the Army gets the credit?

Changes in the B-17 defensive armament seems to gotten fast forward. B-17E had two power turrets/mounts. It showed up in 1941, not 1942.
The famous 13 .50 cal guns tends to over look a few things. Like the radio operators gun have a rather narrow firing arc and even worse vision.
Also over looked is the fact that if you actually want to use all 13 guns you have to have 3 men stuffed in the nose and an 11 man crew.
Totally skipped over is the time it took to get to the Cheyenne tail gun mount in all the self congratulations.
View attachment 700658

It there is also some question about
" Another was the development of the turbo supercharger by General Electric on an Air Corps contract, the only discrete Army research and development program to receive funding through the Great Depression. "
May depend on when the author defines the great depression was and what discrete means. The Army was certainly funding the hyper engine program from 1930 on which in most peoples minds was during the Great Depression.

And this mess,
"American military aircraft would henceforth be powered by engines designed for civilian use, and while high altitude performance had obvious military importance it had little civilian value. The European solution, gear-driven superchargers designed as an integral part of the engine, was an obvious non-starter for economic reasons.27 The military market was simply too small. American superchargers therefore would be add- on accessories and the only evident way to power such a supercharger was a turbine driven by engine exhaust gasses. "

Author apparently doesn't know the difference between single stage and two stage superchargers or he does and doesn't think his readers know the difference.
Also rather ignores the US Navy and P & W working on two stage gear driven supercharges.

Doesn't take much time to get to the tail gun. I helped build a seat for one at the Planes of Fame to original plans. I am in my early 70's and can get into it easily and decently fast. In any case, you don't get into it when the enemy shows up; you get into it on the ground before takeoff. You might get out of it to go relieve yourself, but it's not like you pop in and out a lot during the mission.

 

[GregP]

The examples for why the "real killers of bombers are fighters", if ground fire was as deadly then there should be similar examples of high losses inflicted by the guns at heavy bomber altitudes. Where fighters were active and able to intercept, from Mighty Eighth War Diary

13 June 1943, Kiel raid, 76 sent, 60 effective, 22 lost, 1 written off.
While the second Schweinfurt raid is noted for its losses, the raids of 8 to 10 October had cost 88 MIA and 8 written off.
11 January 1944, Oschersleben raid, 177 sent, 159 effective, 34 lost, 2 written off.
22 February 1944, Aschersleben raid, 289 sent, 181 effective, 32 lost, 4 written off.
24 February 1944, Gotha raid, 239 sent, 213 effective, 33 lost, 1 written off.
6 March 1944, Berlin raid, 730 sent, 672 effective, 69 lost, 6 written off.
18 March 1944, Friedrichshafen raid, 227 sent, 198 effective, 28 lost, 3 written off.
11 April 1944 raids, 917 sent 826 effective, 64 lost, 5 written off.
29 April 1944, Berlin raid, 679 sent, 618 effective, 63 lost, 2 written off.
12 May 1944, Zwickau raid, 295 sent, 258 effective, 41 lost, 1 written off.

Medium bombers tended to operate above the light flak ceilings.
17 May 1943, the 322nd Group B-26, 11 aircraft low level mission to Holland, 1 abort, remainder shot down by fighters, flak and collisions avoiding hostile fire.
23 December 1944 the 391st Group B-26 versus Luftwaffe fighters, 16 B-26 lost, over half the force. The Luftwaffe fighter threat to the allied light and medium bombers stopped well before the threat to the heavies, more so as the light and medium bombers were usually operating with an escort from the start.


Flak was present for the entire ETO air campaign and in fact increased in density over time, the threat from German fighters decreased markedly from June 1944 onwards. In bombs dropped on Germany terms and therefore sorties the 8th Air force hit its half way point in mid November 1944. If you want to use the for campaign figures like that then consider the USN aircraft carrier landing system was a much more effective weapon for the Japanese than their fighters were against the USN carrier based aircraft.


Whereas I note the longer you are tracked the more likely you are to be intercepted, plus there were so many flak guns in Germany 1944/45 that it was very hard to avoid being shot at flying to and from the target and easy to make a small navigation mistake that put you over a defended area. Navigation errors go up with distance. As the Swiss found out a few times.

If you take 31 August 1944 as the date the continental airfields became available to take damaged allied heavy bombers then the following figures apply for the 8th Air Force. In the period to 31 August 1944 some 2.7% of B-17s listed as lost to fighters made it back to allied territory, versus 6.4% of those listed as lost to flak. For the period 1 September 1944 to the end of the war the figures become 5.8% and 16.6%.


Some of the 1945 15th Air Force monthly reports have Engine Change Reports, graphs of average running time per aircraft engine changed. Generally speaking the R-1830 radials in the B-24 and the R-1820 radials in the B-17 had at least an average of 300 hours running when changed, few had 400, with the R-1820 ahead, most having 350 or more hours. Overhauled engines usually had around half the average hours of new engines. The V-1650 Merlins and the V-1710 Allisons usually averaged over 200 hours, few made it to 300 until March/April. Overhauled Allisons were around half the new engine hours, overhauled Merlins more like a quarter. Post war commercial R-1820s and R-1830s were normally racking up TBOs of about 1500 Hrs. Wat are the TBOs these days?

The 15th Air Force target and duty sheets I have often record the altitude the bombs were released at, the maximum was 32,000 feet by a B-17 group, the highest recorded B-24 altitude was 27,000 feet, it is the only B-24 entry of 26,000 feet or higher, versus the 120 B-17 entries. Lowest bombing altitude, assuming no mistaken entries, was 2,300 feet, then one at 3,500 feet, all other entries are 11,000 feet or higher.


How many were 4 engined bombers? The 8th Air Force ones had a 4.2% mechanical abort rate. How many sorties in bad weather? The 8th Air Force had a 9.1% weather abort rate. The USSBS weather report notes in cloud cover terms the forecasts were correct 302 times in 524 raids. The B-17 were better able to fly above bad weather. The 9th Air Force P-47, 201,546 sorties, of which 11,096 were non effective or 5.5%, broken down by cause 5,418 weather, 244 personnel, 3,322 mechanical and 2,112 other causes. Have you done a study to discover why your abort rates are so much less than the wartime ones? So you are sure you are comparing like with like, like available maintenance facilities, stresses put on the aircraft? Mission requirements? Total flying times? Operational tempo?


Even in formations as tight as the 8th Air Force heavy bombers? The night bombers could operate in worse weather as they were not trying to fly in formation.

------

If Roger Freeman is correct in May 1944 the 1st Division started a policy of removing the radio room gun and one waist gunner from its B-17s, mainly for centre of gravity reasons, both waist guns were retained though. In March 1945 the 381st group was flying without ball turrets, the 91st without waist guns or gunners, the 398th without chin turrets and the 94th without chin and ball turrets. The 398th liked the performance increase. In June 1944 the 8th Air Force HQ gave permission to remove the ball turrets from its B-24s, it was a decision left to the groups so some removed the turret and others kept it.

-----

"THE FORTY-FOURTH HARMON MEMORIAL LECTURE IN MILITARY HISTORY,… The Boeing B-17 Flying Fortress was the anvil against which the USAAF fighter force hammered the Luftwaffe fighter arm… The B-17 was a singular design for which there would have been no viable substitute until the B-29… Even before long range fighters were available to escort deep penetrations, massed formations of B-17s took a significant toll of the Luftwaffe fighter arm. the B-24 was nonetheless inferior to the B-17 in every critical performance parameter that counted in the European theater of operations save maximum range… the study showed that four engine bombers were significantly more accurate than twin engine bombers across the board."

If the anvil is correct the Luftwaffe was ignoring raids done by B-24, which would make the B-24 far better than the B-17, zero air to air losses. The 8th Air Force concluded the B-17 was better for it but the results show the B-24 could have been used instead. The USAAF Statistical Digest notes the ETO lost 599 heavy bombers to fighters to end October 1943 and the MTO 166. Assuming a 1 to 1 kill ratio, that makes it 765 Luftwaffe fighters, but the 1943 exchange rate is more like 3 bombers to 2 fighters, so around 500 fighters shot down. Note the critical parameters are not listed in the article, which is a flag that opinion is being used.

Remember when it comes to bombing accuracy at some point you have to decide the miss is so great the bombers were in fact attacking a different target. The raid on Huls (22 June 1943, 224 B-17s despatched plus 11 YB40s, 183 attacked 15 B-17s and 1 YB-40 lost) is a prime example of a USAAF raid that caused heavy damage. After the raid the bomb craters were found over an area of 12 square miles, 20% of the bombs dropped hit the 541 acre (0.84 square miles) site. If the site were a square then each side fence would be 4,650 feet long. In 1943 one strike on the Focke-Wulf factory at Marienburg, 598 500lb bombs were dropped, 286 fell in the factory area and at least 35 hit buildings, 5.8% accuracy if the analysis is correct, this was considered a substantial improvement in the accuracy shown so far. Note that while many bombs fell close most still missed.

The USSBS bombing accuracy reports the B-17 was more accurate than the B-24, but of course the medium bombers were more accurate than both, the direct result of bombing from lower altitudes. In any case the difference in B-17 versus B-24 accuracy was small compared with the other factors. The 15th Air Force was more accurate than the 8th as it was able to do more training on the electronic bombing aids. Being the first formation over the target gave you 82% accuracy, being the fifth meant 30% accuracy, attacking a 1,000 foot target a 9 wide aircraft formation scored 100, 6 wide formation 110.6, and a 3 wide formation 142.2. Turn up with 3 bomber boxes and bomb from 10,000 feet the expected circular error was 570 feet, using 15 boxes 765 feet, 3 boxes at 25,000 feet error 1,047 feet, 15 boxes 1,242 feet. In the final four months of 1944 the 8th Air Force bombs within 1,000 feet of the aiming point, 30% in fair to good visibility, 9.4% in poor visibility, 5% using GH, 5% using Micro H, then using H2X in, 4 to 5/10 cloud 4.4%, 6 to 7/10 cloud 2%, 8 to 9/10 cloud 1%, 10/10 cloud 0.2%.

The B-17 was a better aircraft to fly in and pilot than the B-24, it was more reliable and more accurate a bomber but the differences between the two types as used in Europe were much smaller than the other factors involved, like the chances of being intercepted, flak and smoke defences, sighting methods, formation tactics, training time, weather effects and the size of the attack.

Engage smiling systems before proceeding. "no viable substitute" Say in round terms the 8th Air Force had 1,000 fighters and 2,500 bombers, when you look at the dollar cost of aircraft and the manpower in the combat units you discover the ratio is 3.5 P-51 to 1 B-17. If you want a back of envelope total hindsight 8th Air Force and assuming the Lancaster follows this costing then change the 8th Air Force to 1,500 Lancasters and 4,500 P-51. The average Lancaster bomb load was 10,065 pounds versus the average B-17/24 load of 5,194 pounds, so average bomb lift becomes 7,500 versus 6,500 short tons and able to drop the more destructive larger size bombs. The P-51 pilots then rotate the three missions, sit beside your pet Lancaster all mission, standard 8th Air Force escort and look for trouble in the area around the bomber force. If you want altitude performance consider the Lancaster VI with two stage Merlins, with only a rear turret fitted it had a top speed around 345 mph which translated to cruising speeds comes close to the fighter cruise speeds and should cut about an hour out of any mission to Germany with associated decreases in interception chances and winter daylight problems. Perhaps fit a pair of forward firing machine guns under pilot control to counter head on attacks. Adjust according to preferences, 100 bombers to 350 fighters one up, the other down.

None of which change the losses to AAA ...and they still generally outweigh the losses to fighters except for heavy bombers, where they are about equal.

 

[Shortround6]

Totally skipped over is the time it took to get to the Cheyenne tail gun mount in all the self congratulations.

In any case, you don't get into it when the enemy shows up; you get into it on the ground before takeoff.

A bit of miscommunication.
I was not referring to time it took for the gunner to get into the firing position but the length of time it took to get a wide field of fire tail gun position into the B-17. It tool until late 1943 or early to start getting the Cheyenne mount into the tail in place of the "stinger"
I would note that the guns were still manually controlled even though the sight was much improved but trying the aim/track with the guns at near the limits of the travers and elevation may have been a problem.
The B-24s used a powered tail turret (mostly).
Things changed for both bombers over time but the B-24 in most of 1944 had four power turrets as built compared to 3 power turrets on the B-17 which may have offset the extra guns on the B-17 to some extent.

 

[JDCAVE]

Have to disagree with your premise about losses and the "real killer of bombers."

I flat disagree with "loss rates go up with time spent in hostile airspace."

I disagree with "loss rates went up with distance" and "loss rates went up with weather."

Sorry to be blunt Greg. These statements are wrong. Everything you said here is completely at odds with all wartime analysis by the scientists and statisticians for the various commands.

"Loss rates go up with time in hostile airspace" Of course it does! The longer fish are around your hooks, the greater number of fish you will catch. Put another way, the longer you fish, the more fish you will catch. Predator-prey models which have been around for over a hundred years predict this to be the outcome. These models have 5 key components: prey availability, prey density, search time, handling time and satiation. The longer prey is available to a predator (measured in units of time), the greater the likelihood it is attacked and eaten. Handling time includes the act of capture as well as consumption. Satiation is the point at which the predator no longer wishes to use energy capturing prey due to being full. The air warfare analogy to satiation is the combination of fatigue and running out of fuel.

"loss rate go up with distance" distance is a function of time, see above.

"loss rates go up with weather" poorly stated, perhaps, but aircraft crash rates absolutely went up with bad weather. Surely you aren't arguing otherwise?

Jim

 

[Just Schmidt]

The European requirement for tight formation flying was not as severe, and the typical maximum-range mission allowed Pacific Liberators, when necessary, to approach the target at adequate altitude because of the large amount of fuel burned on the way. (p.186-187)

I'm not certain I understand this.

Would not a B-24 fueled for a shorter mission be able to attain greater hight from the get go, and at the target, having approximately half of initially less fuel left, be able to attain greater hight than on the longer ranged mission?

Was it policy to fill the tanks to full on missions regardless of the expected range, to give greater safety margins for headwinds and navigational errors, or confer greater oprerational flexibility? Or is adequate hight here to be understood relatively, as what was needed for typical aaa and fighters present in the different theaters?

 

[JDCAVE]

Flak was ALWAYS a threat. You can't see it coming or do anything about it. Flak got better as the war went on, too, just as fighters did.

You would be shot down if you didn't take action against radar guided flak. You had to change your track or you would be shot down. Pilots took evasive action when they had determined they were being predicted.

 

[JDCAVE]

I'm not certain I understand this.

Would not a B-24 fueled for a shorter mission be able to attain greater hight from the get go, and at the target, having approximately half of initially less fuel left, be able to attain greater hight than on the longer ranged mission?

Was it policy to fill the tanks to full on missions regardless of the expected range, to give greater safety margins for headwinds and navigational errors, or confer greater oprerational flexibility? Or is adequate hight here to be understood relatively, as what was needed for typical aaa and fighters present in the different theaters?

I'm not sure about Liberators and how the USAAF/Coastal command delt with load management, but for Bomber Command, heavy bombers carried different petrol and bomb loads, depending on distance to the target. The aircraft were typical loaded to the maximum permissible weights. On deep penetrations, the maximum petrol load was carried at the expense of bomb loads. The maximum petrol load of the Lancaster was 2154 gallons.

https://ibccdigitalarchive.lincoln.ac.uk/omeka/files/original/408/7246/SChattertonJ159568v10186.2.jpg

 

[EwenS]

I'm not sure about Liberators and how the USAAF/Coastal command delt with load management, but for Bomber Command, heavy bombers carried different petrol and bomb loads, depending on distance to the target. The aircraft were typical loaded to the maximum permissible weights. On deep penetrations, the maximum petrol load was carried at the expense of bomb loads. The maximum petrol load of the Lancaster was 2154 gallons.

https://ibccdigitalarchive.lincoln.ac.uk/omeka/files/original/408/7246/SChattertonJ159568v10186.2.jpg

Coastal Command laid down weapon & fuel loads and MTOW for each Liberator Mark. These varied over time. In particular fuel loads including how many overload tanks were carried in the bomb bay. Come 1945 in the Far East various weight reduction measures were adopted (turrets deleted etc) to maximise range with aircraft flying at significant overload weights.

The USN had similar tables for their PB4Y-1 aircraft.

 

[33k in the air]

I'm not certain I understand this.

Would not a B-24 fueled for a shorter mission be able to attain greater hight from the get go, and at the target, having approximately half of initially less fuel left, be able to attain greater hight than on the longer ranged mission?

Was it policy to fill the tanks to full on missions regardless of the expected range, to give greater safety margins for headwinds and navigational errors, or confer greater oprerational flexibility? Or is adequate hight here to be understood relatively, as what was needed for typical aaa and fighters present in the different theaters?

From what I understand, in the ETO for USAAF bombers, fuel tanks were usually filled to the maximum possible for a mission to give the bombers the greatest amount of reserve to compensate for weather, battle damage, and so forth. Note that formation assembly typically took one to two hours, and was done over England, in friendly airspace. (That's one to two hours of flight time not available for cruising toward the target.) In the PTO, formations could slowly assemble while on the way to the target, since the distances involved meant most of the flight was over empty ocean far from enemy bases, and the bombers could climb to bombing altitude gradually while on the way toward the target.

 

[33k in the air]

I'm not sure about Liberators and how the USAAF/Coastal command delt with load management, but for Bomber Command, heavy bombers carried different petrol and bomb loads, depending on distance to the target. The aircraft were typical loaded to the maximum permissible weights. On deep penetrations, the maximum petrol load was carried at the expense of bomb loads. The maximum petrol load of the Lancaster was 2154 gallons.

Bomb loads varied considerably in Bomber Command aircraft; for example, the Lancaster had loads typically ranging from 5,000 lbs to 13,000 lbs depending on the target and distance. For USAAF heavies the loads were much more narrow in weight range: 5,000 lbs to 6,000 lbs being by far the most frequent for both the B-17 and B-24.

 

[Geoffrey Sinclair]

Regarding the B-17 versus B-24 debate, I'll offer these quotes from the book The B-24 Liberator — A Pictorial History by Allan G. Blue:

The European requirement for tight formation flying was not as severe, and the typical maximum-range mission allowed Pacific Liberators, when necessary, to approach the target at adequate altitude because of the large amount of fuel burned on the way. (p.186-187)

Not sure I understand this as I thought the further from base the target is the heavier the attacker given the fuel load required to return home. The higher speeds altitudes and tighter formations used in Europe increased fuel consumption so they cold not fly as far but maximum range in both theatres was at half fuel plus reserve remaining, or about the same weight.

Generally the strength of the ground defences determined bombing altitude and speed, from just above bomb safety height to just above "effective" local AA fire height. With a contribution from the chances of being intercepted given that is easier at lower altitude.

According to Roger Freeman for an 8th Air Force B-17F taking off weighing 55,000 pounds the warm up, take off and initial climb to 25,000 feet took an hour and cost 380 US gallons of fuel, over 20% of the fuel on board, horizontal distance moved minimal relative to the target distance. Starting with 1,760 gallons, used 1,075 by target, have 115 gallons left after landing. So 570 gallons in the return journey on what is given as a 5 hour mission, so something like 400+ miles from base at a TAS cruise of 225 mph at 25,000 feet. The Tokyo tanks added another 1,080 gallons, or about an extra hour out and back. The B-17 as operated by the 8th air force had to watch its fuel consumption when hitting targets in eastern Germany, the B-24 less so. Remembering the aircraft at the rear of the formation would be paying a higher fuel penalty than those at the front. RAF Bomber Command used a 200 Imperial gallons fuel reserve for Halifax and Lancaster bombers. The nightmare for the allied bomber commanders was after launching a major strike the weather would change and close most British airfields.

Generally speaking in the Pacific a raid could fly as a quite loose formation, only closing up near the target and not having to climb very high given the usual level of AA and fighter defences.

Now going to the other extreme, the 30 September 1944 B-24 raid on Balikpapan from Noemfoor. Round trip 2,500 miles, normal missions were in the 1,500 to 1,800 miles range. The aircraft would be in the air for 16+ hours, average speed of 150 mph. Full ammunition, 3x1,000 pound bombs and an extra 700 or more gallons of fuel to allow for a 400 gallon reserve. By removing anything they could they managed to get the take off weight down to 68,500 pounds. To maximise the range, schedules were produced for the crew to move themselves and equipment around the aircraft to keep the Centre of Gravity at its optimum.

Take offs started at midnight, 72 aircraft took off at 1 a minute, 2 aborts, the rendezvous point was 900 miles from base, at dawn, the first 12 aircraft assembled into their formation within 13 minutes but when they arrived at the target found it cloud covered, so they spent around 45 minutes waiting for an opportunity under continuous heavy fighter attack plus heavy flak when they came with range of the refineries, heavy as defined in PTO terms, the gunners claimed 7 kills and 9 probable. In the end 4 B-24 lost. A further raid on 3 October then the 10 October raid had P-47 and P-38 escorts showing the allies had opened up airfields closer to Balikpapan.

Bomb loads varied considerably in Bomber Command aircraft; for example, the Lancaster had loads typically ranging from 5,000 lbs to 13,000 lbs depending on the target and distance. For USAAF heavies the loads were much more narrow in weight range: 5,000 lbs to 6,000 lbs being by far the most frequent for both the B-17 and B-24.

Average Lancaster bomb loads went up through the war, given the upgrade to the engines. According to the Bomber Command War Diaries the 26 August 1944 raid on Konigsberg had route to target of 950 miles from base, the average bomb load dropped was around 7,100 pounds. The range/bomb load table for the Lancaster, a route track of 1,800 miles left 9,000 pounds available for bombs and window, after allowing a 200 gallon reserve. I have not seen a bomb load as low as 5,000 pounds on a Lancaster, even in an incendiary heavy load, while six by 1,500 pound mines was a regular load. The maximum internal HE load was 6,000 pounds for the B-17 and 8,000 for the B-24, and the ETO/MTO tight formations tended to mean near maximum fuel loads. The B-17 bomb loads used when bombing Berlin, to the nearest 50 pounds given the usual uncertainties in bomb loads, average for all raids 4,950 pounds. For the raids March to June 1944 4,700 pounds. For the raids in 1945 5,250 pounds. The advantages of air superiority.

 

[33k in the air]

Average Lancaster bomb loads went up through the war, given the upgrade to the engines.

To put some figures to that:

Monthly average nominal bomb load weight according to my analysis of the 106 Squadron ORBs from July 1942 through April 1945, during which time the squadron was flying the Lancaster. This uses only those sorties for which a bomb load was expressly listed, and the nominal weight of the bombs (i.e. its weight class). In parentheses is the number of sorties in that month with a listed bomb load, as well as the percentage of those sorties which carried incendiary bombs of either 4-lb or 30-lb weight.

7,130 lbs = July 1942 (69 sorties; 26.1%)
8,026 lbs = Aug. 1942 (63 sorties; 50.8%)
7,073 lbs = Sept. 1942 (98 sorties; 80.6%)
5,778 lbs = Oct. 1942 (79 sorties; 88.6%)
5,166 lbs = Nov. 1942 (59 sorties; 78.0%)
5,821 lbs = Dec. 1942 (36 sorties; 88.9%)

7,740 lbs = Jan. 1943 (74 sorties; 90.5%)
6,988 lbs = Feb. 1943 (102 sorties; 91.2%)
7,695 lbs = Mar. 1943 (113 sorties; 83.2%)
6,950 lbs = Apr. 1943 (119 sorties; 69.7%)

7,902 lbs = May. 1943 (80 sorties; 58.8%)
9,447 lbs = June 1943 (107 sorties; 82.2%)
9,524 lbs = July 1943 (109 sorties; 94.5%)
9,442 lbs = Aug. 1943 (129 sorties; 96.1%)
10,570 lbs = Sept. 1943 (64 sorties; 100.0%)
10,657 lbs = Oct. 1943 (95 sorties; 100.0%)
10,320 lbs = Nov. 1943 (78 sorties; 88.5%)
10,140 lbs = Dec. 1943 (84 sorties; 100.0%)

9,572 lbs = Jan. 1944 (114 sorties; 99.1%)
9,279 lbs = Feb. 1944 (73 sorties; 91.8%)
9,968 lbs = Mar. 1944 (136 sorties; 77.9%)
10,231 lbs = Apr. 1944 (99 sorties; 54.5%)
11,427 lbs = May 1944 (91 sorties; 27.5%)
10,462 lbs = June 1944 (184 sorties; 0.0%)
11,005 lbs = July 1944 (212 sorties; 12.3%)
11,398 lbs = Aug. 1944 (240 sorties; 22.5%)
11,491 lbs = Sept. 1944 (160 sorties; 55.0%)
11,266 lbs = Oct. 1944 (65 sorties; 67.7%)
11,551 lbs = Nov. 1944 (126 sorties; 27.0%)
11,253 lbs = Dec. 1944 (105 sorties; 20.0%)

9,982 lbs = Jan. 1945 (87 sorties; 16.1%)
9,593 lbs = Feb. 1945 (122 sorties; 30.3%)
11,243 lbs = Mar. 1945 (149 sorties; 8.1%)
10,858 lbs = Apr. 1945 (74 sorties; 0.0%)


Part of the weight increase is, I think, attributable to improved bomb carrying arrangements in the bomb bay, although I've not come across any reference discussing this point. For example, 14 x 500-lb bombs is regularly shown in graphics depicting the carrying capacity of the bomb bay (e.g. on p.76 in Haynes' Avro Lancaster Owners' Workshop Manual). But 106 Squadron was carrying 18 x 500-lb bombs in 1944, and the Lancaster X of 428 Squadron was sometimes packing in 20 x 500-lb bombs that year.

The Haynes book also shows a load of 1 x 4,000-lb, 6 x 500-lb, and 2 x 250-lb (7,500 lbs total). Yet a load of 1 x 4,000-lb and 16 x 500-lb (12,000 lbs total) was regularly carried by 106 Squadron aircraft (it was the fifth most frequently carried load by the squadron).

 

[daviemax]

B-17s with B-2 turbochargers were rated for 30,000 feet; those with B-22s were rated for above 35,000 feet. The record altitude was 43,499 feet set by B-17G 43-39073 in July 1945 (at the time a world record for four-engine aircraft). Fully loaded for combat, B-24s had trouble flying above 23,500 feet whereas on the same mission B-17s flew 25-30,000 feet. Yes - wing loading was an aspect but also airfoil - the Davis-type wing was less efficient at high altitude; this is why the B-17 had a higher ceiling than B-29s, which had a Boeing developed wing similar to the Davis wing.

QB-17 target drones routinely flew missions at 30,000 feet and occaisionally flew missions as high as 40,000 feet.

 

[33k in the air]

I have not seen a bomb load as low as 5,000 pounds on a Lancaster, even in an incendiary heavy load, while six by 1,500 pound mines was a regular load.

Lower weight 106 Squadron bomb loads:

112 x 30-lb incendiaries (3.360 lbs nominal total, consisting of 14 x 8 x 30-lb SBC) carried in late 1942 and early 1943
1,260 x 4-lb incendiaries (5,040 lbs nominal total, consisting of 14 x 90 x 4-lb SBC) carried in late 1942 and early 1943
5 x 1,000-lb bombs (5,000 lbs nominal total) carried in late 1942.

The maximum internal HE load was 6,000 pounds for the B-17 and 8,000 for the B-24, and the ETO/MTO tight formations tended to mean near maximum fuel loads. The B-17 bomb loads used when bombing Berlin, to the nearest 50 pounds given the usual uncertainties in bomb loads, average for all raids 4,950 pounds. For the raids March to June 1944 4,700 pounds. For the raids in 1945 5,250 pounds. The advantages of air superiority.

The B-17 could carry 8,000 lbs internally, but this had to be 8 x 1,000-lb SAP bombs; only 6 x 1,000-lb GP bombs could fit.

According to B-17 bomb loads for the 401st Bomb Squadron of the 91st Bomb Group for Nov. 1942 through June 1944:

10 x 500-lb bombs (21.9% of sorties)
12 x 500-lb bombs (18.6% of sorties)
42 x 100-lb incendiaries (12.0% of sorties)
5 x 1,000-lb bombs (11.5% of sorties)
6 x 1,000-lb bombs (6.0% of sorties)

Part of the average increase for B-17s and B-24s could also be attributed to better bomb carrying arrangements. The maximum load of 100-lb AN-M47 incendiaries was initially 24 in the B-17, but this was later increased to 42 through the use of a cluster adapter which allowed multiple bombs to be hung from one bomb station. This also boosted the number of 100-lb GP bombs carried from 24 to 38. The B-24 saw similar improvements, with 100-lb GP or incendiaries rising from 20 to 52.

The load of 250-lb GP bombs may have likewise benefited, as I've seen instances of 20 x 250-lb bombs in the B-17 compared to its initial 16 x 250-lb limit; the B-24 seems to on occasion have doubled its load, from 12 x 250-lb to 24 x 250-lb GP. (I haven't yet done a more thorough review of the bomb loads for ETO/MTO American bombers.)