YB-40 Flying Fortress
Encyclopedia
The Boeing
YB-40 Flying Fortress was a modification of the United States
B-17 Flying Fortress bomber
aircraft, converted to act as a heavily armed escort for other bombers during World War II
. At the time of its development, long-range fighter aircraft
such as the P-51 Mustang
were just entering quantity production, and thus were not yet available to accompany bombers all the way from England
to Germany
and back.
, Project V-139, began in September, 1942 by converting the second production B-17F-1-BO (serial number 41-24341) built. Conversion work was done by Lockheed's Vega company.
The aircraft differed from the standard B-17 in that a second manned dorsal turret was installed in the former radio compartment, just behind the bomb bay and forward of the ventral ball turret
's location. The single .50-calibre (12.7 mm) Browning machine gun at each waist station was replaced by two of them mounted side-by-side as a twin-mount emplacement, with a mount for each pair of these being very much like the tail gun setup in general appearance. The bombardier
's equipment was also replaced with two .50-calibre machine guns in a remotely operated Bendix
designed "chin"-location turret.
The existing "cheek" machine guns (on the sides of the forward fuselage at the bombardier station), initially removed from the configuration, were restored in England to provide a total of sixteen guns, and the bomb bay was converted to an ammunition magazine
. Additional armor plating
was installed to protect crew positions.
The aircraft's gross weight was some 4,000 pounds greater than a fully armed B-17. An indication of the burden this placed on the YB-40 is that while the B-17F on which it was based was rated to climb to 20,000 ft in 25 minutes, the YB-40 was rated at 48 minutes. Part of the decreased performance was due to the weight increase, and part was due to the greater aerodynamic drag
of the gun stations.
The first flight of the XB-40 was on 10 November 1942. The first order of 13 YB-40s was made in October 1942. A follow-up order for 12 more was made in January 1943. The modifications were performed by Douglas Aircraft at their Tulsa, Oklahoma
center, and the first aircraft were completed by the end of March 1943. Twenty service test aircraft were ordered, Vega Project V-140, as YB-40 along with four crew trainers designated TB-40.
Because Vega had higher priority production projects, the YB-40/TB-40 assembly job was transferred to Douglas. A variety of different armament configurations was tried. Some YB-40s were fitted with four-gun nose and tail turrets. Some carried cannon of up to 40 mm in calibre, and a few carried up to as many as 30 guns of various calibres in multiple hand-held positions in the waist as well as in additional power turrets above and below the fuselage.
Externally, the XB-40 had the symmetrical waist windows of the standard B-17F and the second dorsal turret integrated into a dorsal fairing. In contrast, most of the YB-40s had staggered waist windows for better freedom of movement of the waist gunners, and the dorsal turret was moved slightly backwards, so that it stood clear of the dorsal fairing.
and repaired, it never flew in combat. The remaining 12 were allocated to the 92d Bombardment Group (Heavy), being assigned to the 327th Bombardment Squadron
, stationed at RAF Alconbury
(AAF-102) on 8 May 1943.
YB-40s flew in the following operational missions:
s were credited. Five German fighter kills and two probables (likely kills) were claimed, and one YB-40 was lost, shot down on the 22 June mission to Hüls, Germany. Tactics were revised on the final five missions by placing a pair of YB-40s in the lead element of the strike to protect the mission commander.
Overall the concept proved a failure because the YB-40 could not keep up with standard B-17Fs, particularly after they had dropped their bombs. Despite the failure of the project as an operational aircraft, it led directly to modifications conspicuous on the final production variant of the B-17, the B-17G:
Once the test program ended, most of the surviving aircraft returned to the United States in November 1943 and were used as trainers. 42-5736 ("Tampa Tornado") was flown to RAF Kimbolton
on 2 October 1943 where it was put on display and later used as a group transport. It was returned to the United States on 28 March 1944. All of the aircraft were sent to reclamation, mostly at RFC Ontario
in May 1945, being broken up and smelted. (A couple of the YB-40s can be seen in the 1946 movie The Best Years of Our Lives
, in the famous scene shot at the Ontario "graveyard".) No airframes were sold on the civil market.
United States
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
YB-40 Flying Fortress was a modification of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
B-17 Flying Fortress bomber
Bomber
A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...
aircraft, converted to act as a heavily armed escort for other bombers during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. At the time of its development, long-range fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
such as the P-51 Mustang
P-51 Mustang
The North American Aviation P-51 Mustang was an American long-range, single-seat fighter and fighter-bomber used during World War II, the Korean War and in several other conflicts...
were just entering quantity production, and thus were not yet available to accompany bombers all the way from England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
to Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and back.
Design and development
Work on the prototypePrototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
, Project V-139, began in September, 1942 by converting the second production B-17F-1-BO (serial number 41-24341) built. Conversion work was done by Lockheed's Vega company.
The aircraft differed from the standard B-17 in that a second manned dorsal turret was installed in the former radio compartment, just behind the bomb bay and forward of the ventral ball turret
Ball turret
A ball turret was a particular form of spherical-form, altazimuth mount movement manned aircraft gun turret, accommodating the gunner with nearly all the needed equipment for defensive firepower mounted either within or onto the spherical shell of the turret structure, mounted on aircraft during...
's location. The single .50-calibre (12.7 mm) Browning machine gun at each waist station was replaced by two of them mounted side-by-side as a twin-mount emplacement, with a mount for each pair of these being very much like the tail gun setup in general appearance. The bombardier
Bombardier (rank)
Bombardier is a rank used in artillery units in the armies of Commonwealth countries instead of corporal. Lance-bombardier is used instead of lance-corporal....
's equipment was also replaced with two .50-calibre machine guns in a remotely operated Bendix
Bendix Corporation
The Bendix Corporation was an American manufacturing and engineering company which during various times in its 60 year existence made brake systems, aeronautical hydraulics, avionics, aircraft and automobile fuel control systems, radios, televisions and computers, and which licensed its name for...
designed "chin"-location turret.
The existing "cheek" machine guns (on the sides of the forward fuselage at the bombardier station), initially removed from the configuration, were restored in England to provide a total of sixteen guns, and the bomb bay was converted to an ammunition magazine
Magazine (artillery)
Magazine is the name for an item or place within which ammunition is stored. It is taken from the Arabic word "makahazin" meaning "warehouse".-Ammunition storage areas:...
. Additional armor plating
Vehicle armour
Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, missiles, or shells, protecting the personnel inside from enemy fire. Such vehicles include tanks, aircraft, and ships....
was installed to protect crew positions.
The aircraft's gross weight was some 4,000 pounds greater than a fully armed B-17. An indication of the burden this placed on the YB-40 is that while the B-17F on which it was based was rated to climb to 20,000 ft in 25 minutes, the YB-40 was rated at 48 minutes. Part of the decreased performance was due to the weight increase, and part was due to the greater aerodynamic drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
of the gun stations.
The first flight of the XB-40 was on 10 November 1942. The first order of 13 YB-40s was made in October 1942. A follow-up order for 12 more was made in January 1943. The modifications were performed by Douglas Aircraft at their Tulsa, Oklahoma
Tulsa, Oklahoma
Tulsa is the second-largest city in the state of Oklahoma and 46th-largest city in the United States. With a population of 391,906 as of the 2010 census, it is the principal municipality of the Tulsa Metropolitan Area, a region with 937,478 residents in the MSA and 988,454 in the CSA. Tulsa's...
center, and the first aircraft were completed by the end of March 1943. Twenty service test aircraft were ordered, Vega Project V-140, as YB-40 along with four crew trainers designated TB-40.
Because Vega had higher priority production projects, the YB-40/TB-40 assembly job was transferred to Douglas. A variety of different armament configurations was tried. Some YB-40s were fitted with four-gun nose and tail turrets. Some carried cannon of up to 40 mm in calibre, and a few carried up to as many as 30 guns of various calibres in multiple hand-held positions in the waist as well as in additional power turrets above and below the fuselage.
Externally, the XB-40 had the symmetrical waist windows of the standard B-17F and the second dorsal turret integrated into a dorsal fairing. In contrast, most of the YB-40s had staggered waist windows for better freedom of movement of the waist gunners, and the dorsal turret was moved slightly backwards, so that it stood clear of the dorsal fairing.
Operational history
The YB-40's mission was to provide a heavily gunned escort capable of accompanying bombers all the way to the target and back. Of the initial order of 13, one (43-5732) was lost on the delivery flight from Iceland to UK in May 1943; it force-landed in a peat bog on an offshore Scottish island after running out of fuel. Although removed to StornowayStornoway Airport
-Other Tenants:* Maritime and Coastguard Agency - 2 Sikorsky S-92 helicopters operated by CHC Helicopter-Accident and incidents:...
and repaired, it never flew in combat. The remaining 12 were allocated to the 92d Bombardment Group (Heavy), being assigned to the 327th Bombardment Squadron
327th Bombardment Squadron
The 327th Bombardment Squadron is an inactive United States Air Force unit. Its last was assigned to the 4170th Strategic Wing, stationed at Larson Air Force Base, Washington. It was inactivated on 1 February 1963-World War II:...
, stationed at RAF Alconbury
RAF Alconbury
RAF Alconbury is an active Royal Air Force station in Cambridgeshire, England. The airfield is adjacent to the Stukeleys [Great and Little] and located about northwest of Huntingdon; about north of London....
(AAF-102) on 8 May 1943.
YB-40s flew in the following operational missions:
- 29 May 1943 - attacked submarine pens and locks at Saint-NazaireSaint-NazaireSaint-Nazaire , is a commune in the Loire-Atlantique department in western France.The town has a major harbour, on the right bank of the Loire River estuary, near the Atlantic Ocean. The town is at the south of the second-largest swamp in France, called "la Brière"...
. Smaller strikes were made at RennesRennesRennes is a city in the east of Brittany in northwestern France. Rennes is the capital of the region of Brittany, as well as the Ille-et-Vilaine department.-History:...
naval depot and U-boatU-boatU-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...
yards at La Pallice. In the attack, seven YB-40s were dispatched to Saint-Nazaire; they were unable to keep up with B-17s on their return from the target and modification of the waist and tail gun feeds and ammunition supplies was found to be needed. The YB-40s were sent to Technical Service Command at the Abbots Ripton 2nd Strategic Air Depot for modifications.
- 15 June 1943 - four YB-40s were dispatched from Alconbury in a raid on Le MansLe MansLe Mans is a city in France, located on the Sarthe River. Traditionally the capital of the province of Maine, it is now the capital of the Sarthe department and the seat of the Roman Catholic diocese of Le Mans. Le Mans is a part of the Pays de la Loire region.Its inhabitants are called Manceaux...
after completion of additional modifications.
- 22 June 1943 - attack on the I.G. Farben Industrie Chemische Werke synthetic rubber plant at Hüls. The plant, representing a large percentage of the Germany's synthetic rubber producing capacity, is severely damaged. In the raid 11 YB-40s were dispatched; aircraft 42-5735 was lost, being first damaged by flak and later shot down by Uffz. Bernhard Kunze in an Fw 190A-4Focke-Wulf Fw 190The Focke-Wulf Fw 190 Würger was a German Second World War single-seat, single-engine fighter aircraft designed by Kurt Tank in the late 1930s. Powered by a radial engine, the 190 had ample power and was able to lift larger loads than its well-known counterpart, the Messerschmitt Bf 109...
of JG 1/1 over Pont, Germany. The 10 crew members survived and were taken prisoner.
- 25 June 1943 - attack on Blohm & Voss sub shops at OldenburgOldenburgOldenburg is an independent city in Lower Saxony, Germany. It is situated in the western part of the state between the cities of Bremen and Groningen, Netherlands, at the Hunte river. It has a population of 160,279 which makes it the fourth biggest city in Lower Saxony after Hanover, Braunschweig...
. This was the secondary target, as the primary at HamburgHamburg-History:The first historic name for the city was, according to Claudius Ptolemy's reports, Treva.But the city takes its modern name, Hamburg, from the first permanent building on the site, a castle whose construction was ordered by the Emperor Charlemagne in AD 808...
was obscured by clouds. In this raid seven YB-40s were dispatched, of which two aborted. Two German aircraft were claimed as destroyed.
- 26 June 1943 - scheduled but aborted participation in attack on the Luftwaffe air depot at Villacoublay, FranceFranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
(primary target) and also the Luftwaffe airfield at PoissyPoissyPoissy is a commune in the Yvelines department in the Île-de-France in north-central France. It is located in the western suburbs of Paris from the center.In 1561 it was the site of a fruitless Catholic-Huguenot conference, the Colloquy at Poissy...
, FranceFranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. The five YB-40s assigned to the attack were unable to form up with the bombing squadron, and returned to base.
- 28 June 1943 - attack on the U-boatU-boatU-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...
pens at Saint-NazaireSaint-NazaireSaint-Nazaire , is a commune in the Loire-Atlantique department in western France.The town has a major harbour, on the right bank of the Loire River estuary, near the Atlantic Ocean. The town is at the south of the second-largest swamp in France, called "la Brière"...
. In the raid the only serviceable lock entrance to the pens was destroyed. In this attack six YB-40s were dispatched, and one German aircraft was claimed as destroyed.
- 29 June 1943 - scheduled participation in attack on the Luftwaffe air depot at Villacoublay, but aircraft returned to Alconbury due to clouds obscuring the target. In the raid two YB 40s dispatched, one aborted.
- 4 July 1943 - attacks on aircraft factories at NantesNantesNantes is a city in western France, located on the Loire River, from the Atlantic coast. The city is the 6th largest in France, while its metropolitan area ranks 8th with over 800,000 inhabitants....
and Le Mans, France. In these raids two YB-40s were dispatched to Nantes and one to Le Mans.
- 10 July 1943 - attack on CaenCaenCaen is a commune in northwestern France. It is the prefecture of the Calvados department and the capital of the Basse-Normandie region. It is located inland from the English Channel....
/CarpiquetCarpiquetCarpiquet is a commune in the Calvados department in the Basse-Normandie region in northwestern France. Caen – Carpiquet Airport is located in Carpiquet.-Geography:Carpiquet is on the western side of the Caen metropolitan area...
airfield. In this raid five YB-40s were dispatched.
- 14 July 1943 - attacked Luftwaffe air depot at Villacoublay. In this raid five YB-40s were dispatched.
- 17 July 1943 - YB-40s recalled from a raid on Hannover due to bad weather. In this raid two YB-40s were dispatched.
- 24 July 1943 - YB-40s recalled from an attack on on BergenBergenBergen is the second largest city in Norway with a population of as of , . Bergen is the administrative centre of Hordaland county. Greater Bergen or Bergen Metropolitan Area as defined by Statistics Norway, has a population of as of , ....
, NorwayNorwayNorway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
due to cloud cover. In this raid one YB-40 was dispatched.
- 28 July 1943 - attack on the Fiesler aircraft factory at KasselKasselKassel is a town located on the Fulda River in northern Hesse, Germany. It is the administrative seat of the Kassel Regierungsbezirk and the Kreis of the same name and has approximately 195,000 inhabitants.- History :...
. In this raid two YB-40s were dispatched.
- 29 July 1943 - attack on U-boat yards at KielKielKiel is the capital and most populous city in the northern German state of Schleswig-Holstein, with a population of 238,049 .Kiel is approximately north of Hamburg. Due to its geographic location in the north of Germany, the southeast of the Jutland peninsula, and the southwestern shore of the...
. In this raid two YB-40s were dispatched.
Summary
Altogether of the 59 aircraft dispatched, 48 sortieSortie
Sortie is a term for deployment or dispatch of one military unit, be it an aircraft, ship, or troops from a strongpoint. The sortie, whether by one or more aircraft or vessels, usually has a specific mission....
s were credited. Five German fighter kills and two probables (likely kills) were claimed, and one YB-40 was lost, shot down on the 22 June mission to Hüls, Germany. Tactics were revised on the final five missions by placing a pair of YB-40s in the lead element of the strike to protect the mission commander.
Overall the concept proved a failure because the YB-40 could not keep up with standard B-17Fs, particularly after they had dropped their bombs. Despite the failure of the project as an operational aircraft, it led directly to modifications conspicuous on the final production variant of the B-17, the B-17G:
- Chin turret (also incorporated on "final production" models of the B-17F aircraft)
- Offset waist gun positions
- Improved tail gunner station, usually nicknamed the "Cheyenne", after the Cheyenne modification center.
Once the test program ended, most of the surviving aircraft returned to the United States in November 1943 and were used as trainers. 42-5736 ("Tampa Tornado") was flown to RAF Kimbolton
RAF Kimbolton
RAF Kimbolton is a former World War II airfield in England, located 8 miles west of Huntingdon in Cambridgeshire.-USAAF use:The airfield was originally built in 1941 for RAF Bomber Command, then expanded to Class A airfield standards for use by American heavy bombers during 1942. Kimbolton was...
on 2 October 1943 where it was put on display and later used as a group transport. It was returned to the United States on 28 March 1944. All of the aircraft were sent to reclamation, mostly at RFC Ontario
Ontario International Airport
LA/Ontario International Airport , formerly Ontario International Airport, is a public airport located east of the central business district of Ontario, a city in San Bernardino County, California, USA. This airport is owned and operated by the Los Angeles World Airports , an agency of the city...
in May 1945, being broken up and smelted. (A couple of the YB-40s can be seen in the 1946 movie The Best Years of Our Lives
The Best Years of Our Lives
The Best Years of Our Lives is a 1946 American drama film directed by William Wyler, and starring Fredric March, Myrna Loy, Dana Andrews, Teresa Wright, and Harold Russell, a United States paratrooper who lost both hands in a military training accident. The film is about three United States...
, in the famous scene shot at the Ontario "graveyard".) No airframes were sold on the civil market.
Operators
United States
- United States Army Air Force
- XB-40: Conversion of B-17F-1-BO 41-24342 (Not deployed to ETO)
- YB-40: Conversions of B-17F-10-VE 42-5732; 5733, "Peoria Prowler"; 5734, "Seymour Angel"; 5735, "Wango Wango"; 5736, "Tampa Tornado"; 5737, "Dakota Demon"; 5738, "Boston Tea Party"; 5739, "Lufkin Ruffian"; 5740, "Monticello"; 5741, "Chicago"; 5742, "Plain Dealing Express"; 5743, "Woolaroc"; 5744, "Dollie Madison" (All deployed to ETO)
- YB-40: Conversions of B-17F-35-VEs 42-5920, 5921, 5923, 5924, 5925, and 5927 (Not deployed to ETO)
- TB-40: Conversions of B-17F-25-VEs 42-5833 and 5834; B-17F-30-VE 42-5872, and B-17F-35-VE 42-5926 (5833 deployed to ETO, but not used in combat; remainder remained in the United States).