Thursday, April 23, 2015

B-17 and B-24 in the 8th Air Force.

Most of this data comes from the 8th Air Force April 1945 monthly report, which includes 2 tables of effort, one for the B-17 and one for the B-24, it notes casualty figures are not finalised as some reports still have to come in from aircraft that landed in Europe, not back in Britain.

For example it seems the total number of heavy bombers written off after a combat sortie for the war is 1,557 versus 1,562 given in the April report.

In addition the sorties are for stated to be bombing missions only, however the final 8th Air Force report has slightly higher sortie figures, 330,866 versus 328,590 in the April report, so if a final report can be found that splits B-17 and B-24 effort the numbers will vary slightly from the ones presented here.

In terms of numbers the B-17 accounts for 68.9% of all 8th Air Force heavy bomber sorties, 69.2% of such sorties that entered contested airspace (credit sortie) and 70.2% of sorties reported as bombing (effective sortie).  The average B-17 bomb load for the war was 5,139.4 pounds versus 5,329.95 pounds for the B-24.  It means the B-17 dropped 69.45% of the bombs dropped by the 8th Air Force heavy bombers.

As can be seen by the sortie percentages it seems the B-24 was more vulnerable at about every stage to factors causing the sortie to be abandoned.  One reason seems to be a different use of spare sorties, aircraft taking off used to replace any aborting sorties, so formation left Britain at full strength.  Some 4,621 B-17 sorties landed classified as "unused spares" versus 302 B-24, which probably accounts for some of the later differences in sortie abort rates.

Having said that some 91.4% of B-17 credit sorties were classified as effective, versus 87.1% for the B-24.  So while 68.9% of heavy bomber sorties were B-17s they accounted for 61.95% of mechanical, 58.7% of weather and 61.45% of other reason aborted sorties.  The B-17 was the more reliable as used by the 8th Air Force.

For 1944 and the first 4 months of 1945 the B-24 had an accident rate on operations of 0.3 per 100 take offs and 1.01 accidents per 1,000 hours of non-operational flying, versus 0.22 and 0.97 respectively for the B-17.

For the entire war 1.58% of B-17 credit sorties were Missing In Action, versus 1.2% of B-24, partly this is the result of the losses in 1943 (nearly a quarter of total B-17 losses) but if you simply use the 1944 results the loss figures actually increase, to 1.61% for the B-17 and 1.3% for the B-24.  So unless the B-24 was deliberately and regularly being sent to less heavily defended targets the figures indicate you were more likely to come home in a B-24.

Another interesting point about losses is for every 4.15 B-17 listed as missing another was written off after a combat sortie, for the B-24 it is 3 missing for each write off.

The loss figures at first examination seem to be saying the opposite to the anecdotal evidence, the figures are reporting the B-24 was the more survivable, taking fewer losses and making it back with heavier damage.  Alternatively in the damaged situation it could be the B-24 was more prone to taking significant damage in a crash landing.  The figures indicate this was the case, 0.5% of B-17 credit sorties were written off, versus 0.6% of B-24, some 20% more than the B-17 but the B-17 missing to write off ratio is approaching 40% more than the B-24.

So short of a systematic bias in target selection the B-24 was more likely to abandon the mission and more likely to crash but more likely to bring you back, even when damaged, even when accounting for it taking more damage in a crash landing.

The USAAF had 4 categories of damage, A, repairable within 36 hours by the unit, AC, more than 36 hours to repair and needing non unit resources like a sub depot, B requiring a full Repair Depot to fix E write off.

For the war, using 293,025 credit sorties, there were 43,601 category A, 13,893 category AC, 593 category B and 1,557 category E, or 20.4% of all credit sorties came back damaged enough to be classified as damaged.  By year it was 27.4% in 1942, 30.9% in 1943, 21.1% in 1944 and 15.6% in 1945.

The top 4 months were all in 1943 and are the only figures above 40%, being 48.4% in January, 43.9% in July, 42.4% in August and 41.7% in October.  Being percentages these figures are prone to big shifts when there are only a small number of sorties, in 1943 there were 22,099 heavy bomber credit sorties, versus 188,036 in 1944 and 81,912 in the first 4 months of 1945.  There were only 279 credit sorties in January 1943, but over 2,000 for the other 3 months listed above.

The night bombers consistently reported higher MIA figures than the day bombers for 1945, as a percentage of sorties, but it seems the number damaged, including to write off stage, was around 2.8% of sorties despatched.  Versus 15.6% for the 8th Air Force credit sorties, which were about 90% of airborne sorties.  The extra maintenance requirements from consistently having several times the number of damaged aircraft would have been significant.

Bomber Command – British Aircraft

When war clouds gathered in the 1930s, Winston Churchill and a minority of others in the British government urged accelerated development and production of military aircraft as it became increasingly apparent that Germany, rearming in defiance of the Treaty of Versailles, was creating a large and advanced air force. The outbreak of war caught Britain with an undersized air force, and the nation consequently relied heavily on a variety of U.S.- supplied aircraft. However, the British aircraft industry also produced some of the most important planes of the war.

Among British bomber aircraft, the most significant were: 

Armstrong Whitworth Whitley V. Powered by two 1,145-horsepower RR Merlin X engines, the Armstrong Whitworth Whitley entered into Royal Air Force (RAF) service in March 1937. The first of the heavy RAF night bombers, the aircraft was a mediocre performer, with a top speed of 222 miles per hour and a service ceiling of 17,600 feet. Range was 1,650 miles. After 1942, it was used by the RAF exclusively as a trainer and glider tug. A total of 1,737 (all versions) were built. The Royal Navy’s Fleet Air Arm operated the aircraft until 1945.

Avro Lancaster I. Becoming operational in March 1942, the Avro Lancaster was powered by four 1,460-horsepower RR Merlin XX engines and had a wingspan of 102 feet, a loaded weight of 68,000 pounds, a top speed of 308 miles per hour, and a ceiling of 24,500 feet. Its effective range was 1,600 miles. This military workhorse, produced in a quantity of 7,377, could carry a maximum bomb load of 22,000 pounds and was one of the great bombers of World War II, deserving a place beside such American aircraft as the B-17, B-24, and B-29. Lancasters were the most heavily used of British bombers, flying in excess of 156,000 operations and delivering 608,612 tons of bombs on target. Reflecting the monumental cost of the Strategic Bombing of Germany, 3,249 Lancasters were lost in action.

Bristol Blenheim Mark IV. This bomber was developed from the Bristol model 142 civil transport, and when it first became operational (in the Mark I version) in 1937, it was actually faster than most RAF fighters. The Mark IV version, operational by 1939, had a top speed of 266 miles per hour, a service ceiling of 22,000 feet, and a range of 1,460 miles. With a wingspan of 56 feet 4 inches, it was powered by two 920-horsepower Bristol Mercury XV engines. Maximum bomb load was 1,325 pounds.
The Mark I version of the aircraft had the distinction of flying the first Allied operational mission of the war, a reconnaissance over Germany. Mark IV was used extensively as a light bomber and also as a fighter, a reconnaissance aircraft, and a close-support aircraft. The aircraft was crewed by three. A Mark V was developed, which increased the service ceiling to 31,000 feet and range to 1,600 miles. In other respects, however, its performance was disappointing, and the Mark V was used almost exclusively in the Far East.
Relatively slow by 1940s standards and with only light defensive armament, the Blenheims were especially vulnerable to fighter attack. They were withdrawn from the bomber role in 1943. About 6,200 (all versions) were built.

De Haviland Mosquito XVI. One of the war’s great aircraft, the Mosquito was flown as a night fighter, fighter bomber, bomber, and reconnaissance plane. Crewed by two, it had a remarkable top speed of 425 miles per hour and a service ceiling of 36,000 feet. In bomber configurations, the XVI version carried no defensive armament but relied on its speed and maneuverability, which could outperform most fighters. Maximum range was 3,500 miles.
Affectionately dubbed the Mossie, the aircraft was first flown late in 1940 and became operational with the RAF in 1942. It served in Europe and Asia and proved so adaptable that it remained in service well after the war, until 1955. A total of 7,781 (all versions) were built.
The Mark XVI version was driven by two 1,680- horsepower Rolls Royce engines. Wingspan was 54 feet 2 inches, and maximum bomb load was 4,000 pounds.

Fairey Battle I. Introduced in 1940, the Fairey Battle I was a two-place light day bomber powered by a single Rolls-Royce Merlin II piston engine, which delivered 1,030 horsepower. With a 54-foot wingspan, it had a top speed of 241 miles per hour, a service ceiling of 23,500 feet, and a range of 1,050 miles. Armed with a forward-firing .303-inch fuselage- mounted Browning machine gun and a rear-facing .303-inch Vickers K machine gun, the aircraft could carry a 1,000-pound bomb load.
Deployed in France at the outbreak of the war in 1940, the Fairey Battle quickly proved inadequate as a day bomber and was withdrawn from such service very early in the war. However, it continued to operate with the RAF as late as 1949 as a trainer, target tug, and communications aircraft. Some 2,200 were built.

Handley Page Halifax VI. This four-engine bomber first flew in prototype in 1939, and the first Mark I version was delivered in 1940. The Mark VII entered production in 1944 and was powered by four 1,800-horsepower Hercules 100s and had a wingspan of 104 feet 2 inches. Maximum speed was 312 miles per hour with a service ceiling of 24,000 feet and a range of 1,260 miles. Maximum bomb load was 13,000 pounds. Although not nearly as well known as the Avro Lancaster, the Halifax was a highly successful heavy bomber, produced in a quantity of 6,176 (all versions).

Handley Page Hampden I. Powered by two 1,000-horsepower Bristol Pegasus XVIII engines, this medium bomber was designed beginning in 1933 and went into production in 1938. With a wingspan of 69 feet 2 inches and a maximum bomb load of 4,000 pounds, the aircraft could make 254 miles per hour and reach a service ceiling of 19,000 feet. Slow and vulnerable to fighters, it made its last bombing raid in September 1942 and was used mainly for training purposes thereafter. A total of 1,430 were built.

Short Stirling III. The Mark I version of this large four-engine bomber was delivered to the RAF in 1940. The first Mark IIIs were flying by 1942. Powered by four 1,650-horsepower Bristol Hercules XVI engines and with a wingspan of 99 feet 1 inch, this heavy bomber could deliver 14,000 pounds of bombs. However, it soon proved unpopular with aircrews because of its low ceiling (17,000 feet) and inadequate maneuverability near its maximum altitude. By 1943, the Stirling III was withdrawn from bombing missions and relegated to duty as a glider tug and transport. Some were adapted as Mark IVs and used as paratroop transports. Total production for all versions was 2,374.

Vickers Wellington III. First flown in prototype in 1936, the Mark I version of this medium bomber entered RAF service in 1938. It proved successful in a variety of roles, and 11,461 were produced before production ceased in October 1945. The Mark III version was powered by two 1,375-horsepower Bristol Hercules III or two 1,425-horsepower Hercules XI engines. Top speed was 255 miles per hour, service ceiling was 19,000 feet, and range was 1,540 miles. The aircraft could deliver a bomb load of 4,500 pounds. Defensive weapons included eight .303-inch machine guns, two in the nose, four in the tail turret, and two in fuselage positions.
At the beginning of World War II, the Wellington was the principal British bomber, and although it continued to fly bombing missions until the end of the war, it was largely supplanted in this role by heavier, four-engine bombers. The Wellington continued to be used very extensively for antisubmarine attacks and for transport duties.


    Bishop, Patrick. Bomber Boys - Fighting Back 1940-1945. ISBN 978-0-00-719215-1.
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    Childers, Thomas. "'Facilis descensus averni est': The Allied Bombing of Germany and the Issue of German Suffering," Central European History Vol. 38, No. 1 (2005), pp. 75–105 in JSTOR
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Early Boeing B-17 Raids I

Early in 1943, the Boeing B-17E began to be replaced by the B-17F.
In February 1942, just as Sir Arthur Harris took over Bomber Command, the advance wave of what would become a flood of hundreds of thousands of officers and airmen arrived in England from the United States. The Americans had arrived.

That advanced echelon included the commander of the recently activated Eighth Air Force, Maj. Gen. Carl Spaatz. A Mitchellite to the core, Spaatz appeared at Bomber Commands headquarters at High Wycombe on February 23, 1942. He and Harris hit it off at once. They were kindred souls with unshakable faith in the ability of airpower to win the war, though they differed in the details. Thanks to the RAF s earlier hard knocks, Bomber Command would stick to night attacks for die majority of the war. Spaatz believed that the latest-generation B - I 7 had all the defensive armament needed to conduct long-range missions in the teeth of Luftwaffe fighter interception. If flown in close, mutually protective formations, a B-I7 group could field all-round defense with literally hundreds of deadly .50-caliber machine guns.

Through the spring, aircraft and men trickled in from the United States. It was not an impressive force at first, and on the streets of London there was much gossip about the big-talking Americans who had yet to actually measure up to their own words.

The measuring up would take time. First, the USAAF had to learn hard lessons of its own.

That summer, the first of the heavy bomb groups arrived in Great Britain. The 97th earned that honor, setting up operations at RAF Polebrook. Flying the new B-I7E, the 97th lacked training, experience and tactical knowledge. Some of the navigators didn't know how to navigate. Some of the radio operators couldn't even read or send Morse code. Few of the men had ever conducted flights over 20,000 feet. In fact, most had never even strapped on their oxygen masks.

And yet, the 97th would serve as the seed unit for what would become the most massive air effort ever put forth by the United States. Everything has a start point, no matter how successful or not. For the Mighty Eighth, it began on August 17, 1942, when the 97th carried out a twelve-plane raid against a railroad marshalling yard at Rouen, France. Over a hundred Royal Air Force Spitfires provided heavy escort force for the bombers. Experience had shown the Luftwaffe s fighter units in France, which included the elite Jagdgeschwader 26, could be deadly effective adversaries in their new Focke-Wulf 190 "Butcher Birds."

Flying in a B-17 named Yankee Doodle on that first mission was Gen. Ira Eaker, head of VIII Bomber Command. He'd come along to see for himself how the 97th would fare. The co-pilot of Butcher Bird, the lead aircraft that day was Maj. Paul Tibbets. In 1945, Tibbets would pilot the Enola Gay over Hiroshima and his crew would drop the first atomic bomb used in battle.

The raid succeeded beyond all expectations. The dozen Forts dropped almost 40,000 pounds of British-built bombs on the target area. Post-strike reconnaissance showed an impressive, tight pattern to the destruction wrought on the ground. The Norden bombsight appeared to be a wonder device after all. Nothing the British could do at night matched this level of accuracy.

What's more, not a single B-17 went down. All the crews returned safely to England, and there was much revelry that evening at Polebrook. There wouldn't be many good days ahead like this one. In fact, two missions later, a Messerschmitt made a pass at Tibbetts' B-17. A 20 mm cannon shell exploded in the cockpit, which wounded him with shrapnel and nearly took his co-pilot's left hand off.

Still, the Rouen raid served as a good beginning for the nascent Eighth Air Force. It also made excellent propaganda and quieted the British down for awhile. To counter that English attitude, Spaatz took to carrying recon photos of strike damage in his pocket. He'd pull them out and show the results of precision bombing to anyone who wanted to take a look.

Elated at the results, Spaatz and Eaker set about laying the foundations for the massive force they hoped to field against Germany. Through the summer and fall, new bomb groups reached England, including the 303rd and 93rd. The 1st Fighter Group and its P-38s flew across the Atlantic to join VITT Fighter Command. In time, the 31st, 52nd, and 4th Fighter Groups would form the initial core of the available escort force.

Through the rest of the fall, the Eighth Air Force devoted most of its energy against U-boat targets in support of the campaign in the North Atlantic. These deeply unpopular missions contributed little to the Allied cause. By this time, the U-boat pens in the French ports like St. Nazaire had been reinforced with a twenty foot concrete roof. The bombs the B-17s did get on these targets exploded harmlessly on the surface of these massive structures. Worse, the missions exposed the B-17 crews to heavy fighter and anti-aircraft attack. For the men who laid their lives on the line daily to carry out these sorties, such a ridiculous target selection frustrated and demoralized them.