Heavy Bombers

Any plane could do either mission. The tradeoffs differ and they then change the performance parameters of the plane.
The B-17/B-24 and Lancaster/Halifax/Etc.. were very similar with huge differences in details. All had the same MTO weight. Their EEWs were close, but not quite even. Their crew, weapons, armor and fuel fraction all differed. Because of the very long ranges envisioned for American planes and their missions, they had more fuel and better aerodynamics and engines.
More later.

 

The short answer is yes. While many think the British bombers were better than the American types, it was in fact the other way around. Even with ten-12 HMGs and extra armor plates, the B-17 was a few hundreds pounds lighter "Empty Equipped Weight" than the Lancaster. The other two British planes were not competitive. The B-24 was not as light weight, but made up for that with it's high Aspect Ratio-Low Drag wing and tight cowing of it's lower frontal area engines. All five types had very similar MTOs, or Maximum Take Off weights. The difference between the EEW and MTO weights determines how much "Pay Load" could be carried.
Because altitude gave immunity from AAA in proportion to the cube of the difference in altitude, such as = 25,000'/18,000'=1.39, Cubed = 2.68, or the Lancaster could be expected to suffer 2.7 times as many casualties from AAA as the higher flying B-17.
Political choices made by the RAF to minimize casualties by night flying had the unintended consequences of more accidents, but paid off in fewer interceptions and AAA hits. If mission requirements were switched, the Lancaster would have had to trade altitude for bombs, heavier weapons and armor for bombs, and gas/range for bombs to allow for formation building before crossing the channel. On the other hand, the B-17/24 could have flown the night mission and done the opposite, trading bombs for altitude, crew and weapons/armor for bombs and fuel to form up for bombs. The Tonnes per sortie numbers would be reversed and the B-17/24 would have had better numbers than the Lancaster's because of greater aerodynamic efficiency and the turbocharged engines.

 

It was one reason why we believed in "Day light" raids. Trials in the US showed that they really could drop a bomb in a pickle barrel. But weather in the US is typically very much better than over Europe. A failure they did not anticipate until after they had six months or so of experience in Europe.

 

I guess I'm confused? B-17G empty weight was 35,972 pounds. Maximum take off weight was 67,860 pounds, which gives a maximum load of 31,888 pounds. Lancaster's empty weight was 36,900 pounds. Maximum take off weight was 70,000 pounds, which gives a maximum load of 33,100 pounds. Standard bombing altitude for the B-17G was 25,000 feet, for the Lancaster it was 20,000 feet, but for the Lancaster was more mission profile determined (depending on target bombing altitudes could be anywhere between about 7,500 and 20,000 feet). So there was a 5,000 foot rather than 15,000 foot difference.

 

"Service ceiling" is normally defined as the altitude at which an aircraft under standard conditions can no longer climb at a rate of at least 100 ft/min. For the Lancaster (depending on which source you read), Service Ceiling was 21 - 24,000 ft. For the B-17G (source dependent) it was 35 - 36,000 feet. Not the same as Absolute Ceiling or bombing altitude.

B-24 Groups normally bombed between 20 - 25,000 ft. as the aircraft was difficult to fly in close formation at higher altitudes. My understanding is that B-17s bombed between 25 - 30,000 feet, although I don't have mission records for any B-17 Groups.

 

The Lancaster load varied by mission. On an incendiary raid it carried up to 14 1,000-lb SBC (Small Bomb Containers). For area bombing 14 1,000-lb GP bombs. Perhaps the most typical was one 4,000-lb HC bomb and 12 SBC. So 14,000 to 16,000 pounds.

The B-17 had 42 bomb stations internally. I am not sure what you mean by a "440 pound incendiary cluster bomb", the standard USAAF incendiary bombs were the 140-lb AN-M1 Incendiary and the the 500-lb AN-M2 Incendiary-Cluster. Eight AN-M2 could be carried in overload. Maximum internal load for the AN-MK33, M52, or M52-A1 1,000-lb AP was 10 in overload and max factor; 8 was overload. Two 2,000-lb AN-M34 or AN-M66 GP could be carried internally along with two 1,000-lb AP, GP or semi-AP. Six 1,600-lb AN-MK1 AP could be carries in overload and max factor. The configurations you give would only be possible with the external shackles, which reduced aerodynamics and severely affected range and performance. The designed "useful" bomb load is quoted as 2,064 pounds, but the "typical" load was mission and range dependent.

BTW, the "military load" frequently quoted of 12,800 pounds included 5,970 rounds of .50 caliber ball, weighing c. 2,090 pounds.

 

I don't mean to be nit picky, but bombing accuracy in the daytime wasn't much better than at night. The raid was considered a success when about 20% of the bombs hit their intended target. At night, hitting 10% of your intended target would be impressive.

 

According to the BBUS, VIII Air Force accuracy calculated as percentage dropped within 1,000 feet of target varied from a low of about 14% in Apr-Jun 43 to a maximum of nearly 40% during Jul-Sep 44 and Jan-Mar 45. Bomber Command measure of night bombing effectiveness was % of sorties dropping within 3 miles of target. Initially that was about 20% Aug-Nov 41 and reached 90% Dec44-Mar45. They also calculated bomb density, which was bombs per square mile at aiming point per 100 bombs dropped. Aug-Nov 42 that was about 1 (i.e. 1%) and increased to about 11.5 (i.e., 11.5%) by Aug-Nov 44.

 

Of course, all that depended on visibility and accuracy of the bombardier and navigator in getting to the target, plus the conditions at the target. For example, the Eighth Air Force calculated that from 1 September to 31 December 1944 only 14% of bombing missions were executed visually in good to fair visibility. Another 10% were visually in poor visibility, and the rest were with blind bombing aides with or without visual means:

GEE-H 15%
Micro-H 3%
H2X w/ 4-5/10 clouds 3%
H2X w/6-7/10 clouds 5%
H2X w/8-9/10 clouds 15%
H2X w/10/10 clouds 35%

 

.........well I'll be darnened, thanks for the info Rich.

 

Nice thinking! But some small mistakes. All three planes had the SAME MTO after 1944, or so, 72,000 pounds! But they all averaged between 56,000 and 65,000 pounds in normal ops! The Lancaster's "Service ceiling was between 17,900 and 19,2-300' depending on which model it was. When toting the Grand Slam bomb, the Service ceiling was about 14-14,500'! (No Lancaster had a Service ceiling as high as 20,000'!= WRONG!) The two American planes had "Service ceilings" of ~35,000'! While the average bombing altitude was between 25-30,000' this depended on the target as much as the quality of the crew to with stand the thin air at higher altitudes. The Brits saw no reason the install high blown engines when they could not afford to be picky about their crews.
To tote the Grand Slam bomb, they had to modify the plane and strip out almost two Tonnes of extra weight. Normal, late model Lancs with all that extra stuff in them had maximum bomb loads of ~18,000 pounds and tankage for a few hundred gallons less than either the B-17, or B-24. However, they rarely took off with that many bombs, or gas up. They all normally took off at much lower weights.
Divide the total bombs dropped by the number of missions and you will find that the Lancaster's average bomb load was less than 8,800 pounds. This was a political trade off as the Lanc, even with it's low blown engines could have operated at lighter loadings and bombed from 25,000', but then the average bomb tonnage would have been less than the B-17s average. They also could have installed the more expensive two speed, two stage Merlin, but why bother if you have already made up your mind to carry more bombs per sortie at night?

 

Well, yes it was as the Brits measured their success as bombs with in 3 miles of the entire city and our measure was bombs inside the factory fence. Granted, under most European weather conditions we were no better than the Brits on average.

 

I am sorry, everything I read about the Lancaster stated their Service Ceiling was under 20,000'! Does your source state under what conditions that was measured?

 

The maximum bomb load was conditional on range to target and how much fuel it took to get there and back. The Bomb you identify as the 500-lb AN-M2 Incendiary-Cluster actually weighed ~440 pounds and is/was the same bomb as you mention it, IIRC. Of the 42 positions in the bay, only 34 of them could be used with most normal bombs. See page ~110 of the Time Life books about WW-II where it shows 34 incendiary cluster bomb strings from a gaggle of B-17Gs, IIRC again.
That is 14,960 pounds. The maximum listed bomb load on most placards is 17,600 pounds, not 12,800. It was conditional on the fuel load required to RTB after a bomb run at 25-30K'! At 19,200 pounds of bombs, IE, 12 each 1,600 pound AP bombs dropped on the Sub pens on the French coast they never loaded enough fuel so as to limit the operational ceiling to less than 25,000'. I have personally measured the bomb bay of several B-17s, at 102" Long by 96" Wide by 92" tall, and they can easily hold eight 2,000 pounders! One on the top shackle of the inside rack, one just below it on the outside rack, a second bomb on the inside rack below the first bomb on the outside rack and a forth bomb on the outside rack just above the bomb bay doors, other people say you have to start on the outside rack to have the last bomb clear the least deep part of the bay on the inside rack, but I am absolutely certain it could be done the hard way, and it may be possible to fit FIVE 2,000 pound bombs on in that manner. In any case the other side of the plane can also load four 2,000 pounders, or an auxiliary gas tank of, IIRC, 700 Gallons. (= >5,000 pounds!)
Early in the war, we chose not to carry so many bombs because we knew the facts of Flack and were unwilling to take the risk of flying lower. If we had wanted to modify the cat walk between the left and right sides of the bomb bay, like they did with the Lancaster, it would easily hold four "Short fin" AN-M-56 4,000 pound bombs. aS IT WAS, WE NEVER FELT THE NEED. Dratts, bit on the butt again by the dreaded caps lock monster. Since we had the wing hard points for two ~5,000 pound bombs.
PS. the quoted load of .50 Ball ammo should weigh 2,264 pounds, not 2,090! How ever, we did not use ball ammo in aircraft, we used Mk-1/2/8 API with the hardened steel core which was 3.2 grams lighter for each round of ammo reducing said number by ~42 pounds.

 

Yes, of course.

Er, no, the bomb I identify as the 500-lb AN-M2 Incendiary-Cluster, consisted of 128 4-lb AN-M54 Cluster Bombs and a Cluster Adapter, which weighed 28 pounds for an all-up weight of 540 pounds. It was one of the earliest types, produced in small quantities (24,000) from October 1942 to January 1943. However, it is the type identified on the loading diagram for the B-17F. The AN-M2 was quickly replaced and designated Substitute-standard, its replacements in the 500-lb class were numerous (AN-M7, AN-M13, M14, M17, and M19). The most common were the M17 and M19, but there were numerous others varying in bomblets and fuzing. AN-M13 was the smallest in actual weight at 417 pounds. In any case, the stations available for 50-lb incendiary-cluster class bombs in the B-17F were stations 3, 10, 18, 21, 24, 31, 39, and 42. All stations could be used with normal bombs, but in the B-17G, four stations stressed to a maximum of 100-lb were eliminated as unnecessary.

Um, no, sorry, but that is impossible. I am not going by Time Life books, I'm going by Pilot's Manual for B-17F Flying Fortress (AN-01-20-EF-1, undated, but c. 1943) and by the bomb loading diagram from the Engineering Manual for B-17G Flying Fortress (AN-01-20-EG-2, also undated, but also c. 1943).

The maximum listed bomb load was conditional on the number of stations and what they could carry. What they actually carried depended on the mission profile, but the practical maximum was two external 4,000-lb LC and 10 1,000-lb GP internally. That left room for just over 1,000 gallons of fuel and a useful range of 650 miles.

Sorry, but this is getting silly. https://i.imgur.com/vllrsiU.jpg

 

More than a dozen Lancasters were put through Air Ministry trials (A&AEE). No two aircraft were exactly alike. There was always
some variation in build quality, take-off weight, power settings, propeller type, and other accessories. Some reports are here:

Lancaster Performance Trials


Not posted at that site ...

Lancaster Mk I
PB592
Engines (4): Merlin 24
AUW: 72,000 lb.
High speed: 245 mph @ 16,200 ft.
Service ceiling: 18,600 ft.

Lancaster Mk I
W4963
Engines (4): Merlin 20
AUW: 63,000 lb.
High speed: 282 mph @ 13,000 ft.
Service ceiling: 21,400 ft.

Lancaster Mk II
DS602
Engines (4): Hercules XVI
AUW: 62,300 lb.
High speed: 273 mph @ 14,000 ft.
Service ceiling: 17,500 ft.

Lancaster Mk III
W4114
Engines (4): Merlin 28
AUW: 63,000 lb.
High speed: 269 mph @ 8,700 ft.
Service ceiling: 23,000 ft.

Lancaster Mk X
KB721
Engines (4): Merlin 38
AUW: 63,000 lb.
High speed: 270 mph @ 12,600 ft.
Service ceiling: 22,200 ft.

 

I like this post! All planes vary is some respects. I note that one of the test planes had a MTO weight of 72,000 pounds. There are many links to interesting data like this; Boeing B-17 Flying Fortress
If you go through all of those pages you will find that late model B-17 F/G had MTOs of 72,000 pounds. The F had a top speed at about 299 MPH at a gross weight of about 65,000 pounds, IIRC? Note that the Service ceiling was 37,500'!
Production of the B-17F was undertaken by Boeing, Vega and Douglas, the BVDs as they were called (the same abbreviation as the underwear company), but new modifications were taking their toll in airspeed. There were more than four hundred modifications on the B-17F. The only noticeable outside difference was the full blown Plexiglass nose. The B-17F, now armed with eleven 0.50-cal. guns, could only reach 299 mph (481 km/h) and the landing speed was up to 90 mph (144 km/h)! Service ceiling was 37,500 ft. (11,430 m) and range 2,880 miles (4,634 km). It took twenty-five and a half minutes to climb to 20,000 ft. (6,096 m). The BVD companies produced 3,400 B-17Fs.
The B-17G was produced in greater numbers than any other single model and more B-17Gs were lost than any other model. The most obvious difference was the installation of the Bendix chin turret installed under the nose. With the turret under the nose, the view through the Plexiglass nose was now unobstructed for the gunner. The chin turret also had no adverse effect on the aerodynamics of the airplane, and it finally produced the protection that was needed against head-on attacks. Another major change was the installation of the Cheyenne tail turret. The gun had a larger field of fire and the ring-and-bead site was replaced with a reflector site. On the late G models, the waist gunner windows were staggered so the gunners wouldn't get in each other's way. The radio operator's gun on the upper hatch was eliminated since it was considered of low value, because of its poor vantage point. Gradually, production of the B-17 was left solely to Vega and Douglas in California as Boeing eased out of building the B-17 to make room for B-29 Superfortress production lines.17 In all, there were 8,680 B-17Gs built by Boeing, Vega, and Douglas to make it the largest production variation. 18

Boeing B-17 Flying Fortress Specifications
Model: B-17E B-17F B-17G
Dimensions:
Wing span: 103 ft. 9 in (31.6 m) 103 ft. 9 in (31.6 m) 103 ft. 9 in (31.6 m)
Length: 74 ft. 1.5 in (22.5 m) 74 ft. 8.9 in (22.8 m) 74 ft. 4 in (22.6 m)
Height: 19 ft. 2.4 in (5.9 m) 19 ft. 2.4 in (5.9 m) 19 ft. 1 in (5.8 m)
Wing Area: 1,420 sq ft (132 sq m) 1,420 sq ft (132 sq m) 1,420 sq ft (132 sq m)
Weights: Empty: 33,279 lb (15,095 kg) 35,728 lb (16,205 kg) 36,135 lb (16,391 kg)
Loaded: 40,260 lb (18,261 kg) 40,260 lb (18,261 kg) 54,000 lb (24,500 kg)
Maximum Take-off: 48,726 lb (22,101 kg) 48,720 lb (22,099 kg) 65,500 lb (29,710 kg)
Performance: Maximum Speed: 318 mph (511 km/h)
at 25,000 ft (7,625 m) 325 mph (523 km/h)
at 25,000 ft (7,625 m) 287 mph (462 km/h)
at 25,000 ft (7,625 m)
Cruise Speed: 160 mph (257 km/h) 160 mph (257 km/h) 182 mph (293 km/h)
Service Ceiling: 30,000 ft (9,144 m) 30,000 ft (9,144 m) 35,600 ft (10,850 m)
Normal Range: 2,000 miles (3,219 km) with 6,000 lb (2,722 kg) bomb
load @ 220 mph (352 km/h) @ 25,000 ft (7,625 m) 2,000 miles (3,219 km) with 6,000 lb (2,722 kg) bomb
load @ 220 mph (352 km/h) @ 25,000 ft (7,625 m) 2,000 miles (3,219 km) with 6,000 lb (2,722 kg) bomb
load @ 220 mph (352 km/h) @ 25,000 ft (7,625 m)
Powerplant: Four 1,200 hp (895 kW)
Wright R-1820-65 Cyclones
9 cyl. air-cooled single-row radial engines with GE Type B-2
turbo-superchargers. Four 1,200 hp (895 kW)
Wright R-1820-97 Cyclones
9 cyl. air-cooled single-row radial engines with GE Type B-2
turbo-superchargers. Four 1,200 hp (895 kW)
Wright R-1820-97 Cyclones
9 cyl. air-cooled single-row radial engines with GE Type B-22
turbo-superchargers.
Armament: Eleven 50-cal. machine-guns plus a maximum of 17,600 lb (7,983 kg) of bombs. Normal bomb load 6,000 lbs (2,724 kg).
Largest bomb type carried was 2,000 lb (908 kg). Thirteen 50-cal. machine-guns plus a maximum of 17,600 lb (7,983 kg) of bombs. Normal bomb load 6,000 lbs (2,724 kg).
Largest bomb type carried was 2,000 lb (908 kg). Thirteen 50-cal. machine-guns plus a maximum of 17,600 lb (7,983 kg) of bombs. Normal bomb load 6,000 lbs (2,724 kg).
Largest bomb type carried was 2,000 lb (908 kg).

As you can see from all of these charts, the bomb load was up to 17,600 Lbs. Note the references below!

1. Michael J.H. Taylor and John W.R. Taylor, ed. Encyclopedia of Aircraft. New York; G.P. Putnam's Sons., 1978. 40.
2. Chris Chant. From 1914 To The Present Day, The World's Great Bombers. Edison, NJ; Chartwell Books, Inc., 2005. 90.
3. David Mondey. A Concise Guide to American Aircraft of World War II. New York; Smithmark Publishers, 1996. 20.
4. Kenneth Munson. Bombers Between the Wars, 1919-1939. New York: The MacMillan Company, 1970. 160.
5. Lloyd S. Jones. U.S. Bombers. Fallbrook, California: Aero Publishers, 1974. 51.
6. Kenneth Munson. Bombers Between the Wars, 1939-1945. London: Blandford Press, 1969. 151.
7. John T. Correll. The Air Force on the Eve of World War II. Air Force Magazine. October 2007.
8. Page Shamburger and Joe Christy. Command the Horizon, A Pictorial History of Aviation. New York: Castle Books, 1968. 291.
9. William Green. Famous Bombers of the Second World war. Garden City, New York; Doubleday & Company, 1975. 48.
10. Franklin D. Roosevelt: Message to Congress on Appropriations for National Defense. January 12, 1939.
11. Benjamin D. Foulois and C.V. Glines. From the Wrights to the Astronauts, The memoirs of Major General Benjamin D. Foulois New York: McGraw-Hill Book Company, 1968. 232.
12. Herbert M. Mason, Jr. The United States Air Force, A Turbulent History. New York: Mason Charter, 1976. 119.
13. Charles D. Thompson. Aircraft in Profile, Volume 4; Boeing B-17E & F Flying Fortress. Garden City, New York: Doubleday & Company, 1968. 3.
14. Enzo Angelucci, Paolo Matricardi and Pierluigi Pint. Complete Book of World Combat Aircraft. Vercelli, Italy: White Star Publishers, 1988. 242.
15. Norman Fortier. An Ace Of The Eighth. New York: The Random House Publishing Group, 2003. 86.
15. Edward H. Sims. American Aces. New York: Ballatine Books, 1966. 18.
16. Howard Mingos, ed.The Aircraft Year Book for 1945. New York: Lanciar Publishers, Inc. 1945. 227.
17. Roger A. Freeman. Aircraft in Profile, Volume 9; Boeing B-17G Flying Fortress. Garden City, New York: Doubleday & Company, 1971. 1.

 

Way to go Sherlock...If you had paid attention to Rich's posts you would have known this...

Not sure why you a so Hot-to-Trot about lugging around 6 AN-MK1 AP bombs though? Why are you?

 

They used them to bomb submarine pens in France and ships at sea, with some small success.

 

As a simple way to recap the main points of the Argument;
The main attributes in the three planes were;
1. MTO of 72,000 pounds each after June '44.
2. The B-17 was faster than the Lancaster on less power, thus it must be more aerodynamic than the Lancaster. ( 4800-5,520 HP in the B-17 and 5,920 to 6,840 in the Lancaster)
3. The B-17 EEW, weighed less than the Lancaster and so had a larger difference between the MTO and the EEW making for a greater choice of mission profiles.
4. Lastly, there is the huge difference in equipment weight, armor, guns, crew and ammunition load, all in favor of the B-17. Thus making it much harder to convert the Lancaster for the B-17's mission.