List of Boeing B-17 Flying Fortress variants

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Boeing B-17G Flying Fortress

The following is an extensive catalogue of the variants and specific unique elements of each variant and/or design stage of the Boeing B-17 Flying Fortress heavy bomber. For a broader article on the history of the B-17, see B-17 Flying Fortress.

Boeing Model 299 (XB-17)[edit]

Model 299, registration NX13372

The Boeing 299 was the original bomber design made by Boeing to fulfill an August 1934 requirement by the United States Army Air Corps for a bomber capable of carrying 2,000 lb (907 kg) of bombs 2,000 mi (3,218 km) at 200 mph (322 km/h).[1] The Model 299 was powered by four Pratt & Whitney S1EG Hornet radial engines rated at 750 horsepower (560 kW) each at 7,000 feet (2,100 m), giving a maximum speed of 236 miles per hour (380 km/h) and a maximum gross weight of 38,053 pounds (17,261 kg). It carried a bombload of eight 600 pounds (270 kg) bombs, with a defensive armament of five machine guns, with one gun in a nose turret and one each in dorsal and ventral mounts and two waist blisters.[2][3] In 1935, the Boeing 299 competed with several entries by other companies at an evaluation at Wright Field near Dayton, Ohio, USA.

On its flight from Seattle, Washington to Wright Field for the competition, the 299 set a nonstop speed record of 252 mph (406 km/h). Though it crashed to its destruction on takeoff during a demonstration, the crash was due to flight-crew error, not from any flaw in the airplane. Subsequent implementation of a mandatory checklist by the flight crew prior to take-off ensured avoidance of the flight crew error. Despite the crash (and more important, its much higher cost per unit), Air Corps leaders were impressed by the 299. Boeing was awarded with a development contract. The aircraft has since been referred to as the XB-17 but the designation is not contemporary or official.

Y1B-17 (YB-17)[edit]

Boeing Y1B-17 in flight

Though still enthusiastic about the Boeing design, despite it being disqualified from the fly-off contest following the crash of the Model 299 prototype, the Army Air Corps hedged its bet. It cut its order for service test YB-17s from 65 to just 13. On November 20, 1936, the bomber's normal acquisition funding was changed to "F-1"[clarification needed], and the heavy bomber was redesignated "Y1B-17" as a result, before it even flew.

Unlike its predecessor, which had used Pratt & Whitney R-1690 Hornet radial engines, the Y1B-17 used the more powerful Wright R-1820 Cyclone that would become the standard power plant on all B-17s produced. Several changes were also made in the armament, and the crew was reduced from seven to six. Most changes were minor: the most notable was switching from double-wishbone to single-arm landing gear for ease of regular maintenance.

On December 7, 1936, five days after the first flight of the Y1B-17, the brakes on the bomber fused during landing, and it nosed over. Though damage was minimal, the cumulative impact of this event, combined with the crash of the Model 299, triggered a Congressional investigation. Following the crash, the Army Air Corps was put on notice: another such crash would mean the end of the bomber's "F-1" procurement program.

Though they were meant for testing, the commander of Army General Headquarters (Air Force), Major General Frank Andrews, decided to assign twelve Y1B-17s to the 2nd Bomb Group located at Langley Field, Virginia. Andrews reasoned that it was best to develop heavy bombing techniques as quickly as possible. Of the thirteen Boeing aircraft built, one was used for stress testing.

Boeing Y1B-17 wearing a temporary wargame camouflage paint scheme, assigned to the 20th Bomb Squadron, 2nd Bomb Group, based at Langley Field, Virginia

In 1937, the twelve Y1B-17s at Langley Field represented the entire American fleet of heavy bombers. Most of the time spent with the bombers entailed eliminating problems with the aircraft. The most important development was the use of a detailed checklist, to be reviewed by the pilot and copilot just prior to each takeoff. It was hoped that this procedure would prevent accidents similar to that which led to the loss of the Model 299 prototype.

In May 1938, the Y1B-17s (now redesignated B-17) of the 2nd Bombardment Group, led by the lead bombers' navigator Curtis LeMay, took part in a demonstration in which they intercepted the Italian liner Rex. Coming into contact with the liner while it was still 610 mi (982 km) out at sea, the demonstration was meant to prove the range and navigational superiority of the B-17. It also showed that the bomber would be an effective tool for attacking an invasion force before it could reach the United States. The Navy was furious about Army intrusion into their mission, and forced the War Department to issue an order restricting the Army Air Corps from operating more than a hundred miles from the American coastline.

After three years of flight, no serious incidents occurred with the B-17s. In October 1940, they were transferred to the 19th Bombardment Group at March Field.

B-17A (Y1B-17A)[edit]

Boeing Y1B-17A

The aircraft that became the sole Y1B-17A was originally ordered as a static test bed. However, when one of the Y1B-17s survived an inadvertent violent spin during a flight in a thunderhead, Air Corps leaders decided that the plane was exceptionally robust and that there would be no need for static testing. Instead, it was used as a testbed for engine types. After studying a variety of configurations, use of a ventral-nacelle-mount turbocharger position was settled on for each engine. A successive series of General Electric-manufactured turbochargers would equip B-17s as standard items,[4] starting on the first production model, and allowed it to fly higher and faster than the Y1B-17. When testing was complete the Y1B-17A was renamed the B-17A.

Serial number: 37-369


B-17B just after takeoff

The B-17B (299M) was the first production model of the B-17 and was essentially a B-17A with a larger rudder, larger flaps, and a redesigned nose and 1,200 hp (895 kW) R-1820-51 engines. The small gun turret in the upper nose blister was replaced with a .30 in (12.7 mm) machine gun, its barrel run through a flexible ball socket in the upper right hand window of the bombardier's nose. This was held in place by the socket's strength, combined with an flexible strap, later becoming a smaller window rib frame in the nose glazing; the lower, separate bombardier's window was replaced with a shorter-depth, ten-panel, glass nose; this was used on all airframes up through the B-17E series. 19 B-17B aircraft were modified at Boeing and brought up to the full B-17C/D standard. The new nose glazing held a single .30 caliber machine gun and had additional small ball sockets in different panel locations to hold the weapon (two sockets in the upper windows and later one additional socket in the lower left window). This was continued through the B-17E series. During Army Air Corps service, the teardrop-shaped gun blisters were replaced with flush-mounted windows and used for all B-17C/D production. Various aircraft had different levels of upgrades performed. Some only had the bulged side blisters changed to flush windows, while others also had the bulged upper blister changed to a much flatter, curved widow panel.

Crew locations were rearranged, and the original pneumatic brake system was replaced with more efficient hydraulic brakes.[5]

In October 1942 all B-17B aircraft were redesignated RB-17B, the R- indicating "restricted". The RB-17B was used strictly for training, transport, messenger, and liaison duties. This became a designation for obsolescence.

Many of these upgraded aircraft, along with at least one still-airworthy YB-17, were stationed at Sebring Airfield, where the exterior scenes were filmed for the Warner Bros. drama Air Force, directed by Howard Hawks, and starring (among others) John Garfield, Arthur Kennedy, Gig Young, and Harry Carey. The film's real star, however, was a B-17B (United States Army serial number 38-584), carrying on its upper rudder the security-conscious serial number "05564", while passing as a later model B-17D Flying Fortress. Many of these aircraft can be seen in both ground and aerial scenes during the film.

The "B" series made its maiden flight on June 27, 1939. 39 were built in a single production run, but Army Air Corps serial numbers were scattered over several batches. This was because of limited government funding: The Army Air Corps could only afford buy a few B-17Bs at a time.


Boeing B-17C Fortress I in RAF colors

The B-17C was a B-17B with a number of improvements, including more powerful R-1820-65 engines. To boost crew safety, the waist-mounted machine gun blisters were replaced with teardrop-shaped slide-out panels flush with the fuselage, and the ventral blister was replaced by a lower metal housing dubbed a "bathtub turret", similar in appearance and general location on the lower fuselage, to the Bola ventral gondola being used on Nazi Germany's He 111P medium bomber. Some of the most important additions made to the "C" model were self-sealing fuel tanks and defensive armor.

With the passage of the Lend-lease Act in 1941, the Royal Air Force requested B-17s. At that time, the Army Air Corps was suffering from shortages of the B-17, but hesitantly[citation needed] agreed to provide 20 examples to the RAF. Though the Army Air Corps did not consider the B-17 ready for offensive combat, it was still desperately needed in Britain. The 20 modified bombers were Boeing production B-17Cs (company designation Model 299T). The modifications made were the addition of the self-sealing fuel tanks and replacement of the single .30 caliber nose-mounted machine gun with 0.5 inch Brownings.[6]

The 20, four-engine B-17C bombers were placed immediately into frontline RAF service and designated Fortress Mk I.

The bomber performed unremarkably while in British service. By September 1941, three months after the Air Corps became the Army Air Forces, 39 sorties had made up 22 missions. Nearly half of those sorties were aborted due to mechanical problems. Eight of the 20 aircraft were destroyed by September, half to various accidents. Their machine guns tended to freeze-up at high altitudes and were generally unable to effectively protect the Fortresses from German fighters. Their success as bombers were also limited, largely because the aircraft were unable to hit targets from the altitudes at which they flew missions.

The first "C" series flew in July 1940; 38 were built. The 18 remaining of the 20 transferred to the RAF were modified to Boeing's B-17D configuration. However, one of these, B-17C 40-2047, crashed while being ferried from Salt Lake City, UT, to Mather Army Air Base, CA, on November 2, 1941.[7]


B-17D in flight

Though changes in the design made the Army Air Corps decide that the B-17D was worthy of a new sub designation, the B-17C and B-17D were very similar. In fact, both were given the same sub designation (299H) by Boeing.

Several minor changes were made, both internally and externally. Outside, the engines received a set of cowl flaps for improved cooling, and the external bomb racks were removed. On the interior, the electrical system was revised, and another crew member was added. In the aft-dorsal radio compartment room was an overhead twin-machine gun mount, and in the central-aft section was a ventral "bathtub" twin machine gun emplacement. Nose-mounted "cheek" gun ball joints were added for the first time to windows, in a longitudinally staggered layout (the starboard "cheek" gun ball joint was further forward with the port-side ball joint). The number of machine guns brought the total armament aboard to 7: one portable nose 0.30 in (7.62 mm) and 6 flexible 0.50 in (12.7 mm). The B-17D also featured more extensive armor plate protection. A total of 42 "D" models were built, and the 18 remaining B-17Cs were also converted to Boeing's B-17D standard. The sole-surviving example of the "D" model Flying Fortress (originally built in 1940 and nicknamed Ole Betsy by her original crew) is currently undergoing restoration at the National Museum of the United States Air Force in Dayton, Ohio. This B-17D was later renamed "The Swoose" by her last pilot Frank Kurtz; he later named his daughter, actress Swoosie Kurtz, after the bomber.


B-17E in flight

The B-17E (299-O) was an extensive redesign of that used in previous models up to the B-17D. The most obvious change was a redesigned vertical stabilizer, originally developed for the Boeing 307 by George S. Schairer. The new fin had a distinctive shape for the time, with the other end of the fuselage retaining the well-framed, ten panel bombardier's nose glazing from the B-series design.

Because experience had shown that the plane would be vulnerable to attack from behind, both a tail gunner's position and powered fully traversable dorsal turret behind the cockpit, each armed with a pair of "light-barrel" Browning AN/M2 .50 cal. machine guns, were added to the B-17E design. Until this modification, crews had had to devise elaborate maneuvers to deal with a direct attack from behind, including swinging the bomber laterally, which allowed the waist gunners to alternate shots at enemy fighters. (The configuration of "3-window box" would also be implemeted on the B-29, and also adopted by Soviet bombers as late as the Tupolev Tu-16 Badger, and in different form on the US B-52). The teardrop-shaped sliding panels of the waist gunners were replaced by larger rectangular windows, directly across the fuselage from each other, for better visibility. In the initial production run, the ventral "bathtub" gun emplacement of the B-17C/Ds was replaced by a remote-sighted turret, similar to the one used on the chin of the B-25B Mitchell medium bomber, which proved to be a failure in usability, resulting in the remaining B-17E-series being fitted with a Sperry ball turret, to be used for all succeeding B-17 versions.

Boeing B-17Es under construction. This is the first released wartime production photograph of Flying Fortress heavy bombers at one of the Boeing plants, at Seattle, Wash. Boeing exceeded its accelerated delivery schedules by 70% for the month of December 1942.

A total of 512 were built (possibly from the July 1940-dated order from the then-USAAC for B-17s being for that specific number of airframes[8]) making the B-17E the first mass-production version of the Boeing B-17. One of these was later converted to the XB-38 Flying Fortress. Since production this size was too large for Boeing alone to handle, it was assisted by the Vega division of Lockheed and Douglas. Boeing also built a new plant, and Douglas added one specifically for production of the B-17.

In the middle of 1942, 45 B-17Es were transferred to the RAF, where they served under the designation Fortress IIA. Likely because of the shortcomings of the Fortress I (B-17C), the RAF decided not to use the Fortress IIA as a daylight high-altitude bomber, the role for which it had been designed. Rather, they were transferred to the Coastal Command for anti-submarine patrol.

Four known examples of B-17Es still exist in museums today, none of which is currently known to be airworthy.


Brand-new B-17Fs from the Seattle plant. Note the transparent seam of the two-piece Plexiglas bombardier's nose glazing.

The B-17F was an upgrade of the B-17E, although outwardly the types were distinguished only by exchanging the bombardier's ten panel, well-framed nose glazing that had originated with the B-17B, for a molded one-piece or two-piece plexiglas cone, the two-piece version having a nearly-transparent diagonal seam. Fully-feathering paddle-bladed propellers were also provided. Numerous internal changes were made to improve the effectiveness, range, and load capacity of the B-17. However, once placed in combat service, the "F" series was found to be tail-heavy. The weight of gunners and ammunition when combat-loaded moved the center of gravity rearward from its original design point and forced the constant use of the elevator trim tab, stressing this component. In combat the B-17F proved almost immediately to have inadequate defensive protection when attacked directly from the front. Various armament configurations of two to four flexible guns in the "cheek" windows (with the starboard emplacement further forward) and bombardier's nose glazing were utilized in the field. Late production "F" series aircraft received substantially-enlarged mounts for the "cheek" guns on each side of the nose, replacing the previous window-mounted guns. These mounts allowed the guns to fire more directly ahead.

The problem of head-on defense was not truly adequately addressed until the introduction of a powered, Bendix-designed remotely operated "chin" turret in the final production blocks of the F-series Fortresses — starting with the last 86 B-17Fs built by Douglas of the 605 B-17F-DL bombers built, from the B-17F-75-DL production block[9] — directly derived from its debut on the YB-40 experimental "gunship" version.

Boeing B-17F-85-BO (S/N 42-30043) of the 384th Bomb Group, 547th Bomb Squadron

By using a stronger undercarriage, the maximum bomb capacity was increased from 4,200 lb (1,900 kg) to 8,000 lb (3,600 kg). Though this modification reduced cruise speed by 70 mph (110 km/h), the increase in bomb capacity was a decided advantage. A number of other modifications were made, including re-integrating external bomb racks, but because of its negative impact on both rate-of-climb and high-altitude flight the configuration was rarely used and the racks were removed.

Range and combat radius were extended with the installation in mid-production of additional fuel cells in the wings. Called "Tokyo tanks", nine self-sealing rubber-composition tanks were mounted inside each wing on each side of the joint between the inner and outer wing sections. With an extra 1,080 US gal (4,100 l) to the 1,700 US gal (6,400 l) available on the first B-17Fs, the Tokyo tanks added approximately 900 mi (1,400 km) to the bomber's range.

3,405 were built: 2,300 by Boeing, 605 by Douglas, and 500 by Lockheed (Vega). These included the famous Memphis Belle. 19 were transferred to the RAF, where they served with RAF Coastal Command as the Fortress II. Three examples of the B-17F remain in existence, including the restored Memphis Belle.


The most unusual conversion of the B-17G was the JB-17G converted to an engine test bed. The nose section was removed and replaced with a strengthened mount for a fifth engine.
Top view of a B-17G in flight

Generally considered the definitive B-17 design, all changes made in the B-17F production run were incorporated into the final version. These included the Bendix remotely-operated chin turret, bringing the defensive armament to 13 .50 caliber machine guns. The waist gun windows were staggered, another carryover from the YB-40. This allowed more freedom of movement for the waist gunners. The earliest B-17Gs lacked the "cheek" machine gun mounts, as it was believed that the chin turret provided sufficient forward firepower, but they were quickly reintroduced when this turned out not to be the case. In a reversal of the B-17F's design, the starboard "cheek" machine gun mount was moved rearwards and the port side mount was moved forward, just behind the edge of the bombardier's nose glazing, as a result of the need to avoid interference with the storage of the chin turret's control yoke when it was not in use.[10] For late production blocks of the G-series, a revised tail gun position (referred to as the "Cheyenne" configuration after the modification center where it was introduced, the United Airlines Modification Center in Cheyenne, Wyoming)[11] was devised, in which the guns were mounted in a new turret with a reflector sight and a much greater field of fire.[12][13] Some 8,680 were built, and dozens were converted for several different uses:

  • CB-17G: Troop transport version, capable of carrying 64 troops. (44-6975; 44-83373)
  • DB-17G: Drone variant
  • JB-17G: Engine test-bed (44-85813; 44-85734)
  • MB-17G: Missile launcher
  • QB-17L: Target drone
  • QB-17N: Target drone
  • RB-17G: Reconnaissance variant
  • SB-17G: Rescue version, later redesignated B-17H: Featured A-1 lifeboat under fuselage. After World War II, armament on the B-17Hs was removed; it was reinstated when the Korean War began.
  • TB-17G: Special duty training version
  • VB-17G: VIP transport
  • PB-1: This designation was given to one B-17F and one B-17G. They were used by the U.S. Navy for various test projects.
  • PB-1G: This designation was given to 17 B-17Gs used by U.S. Coast Guard as air-sea rescue aircraft.
  • PB-1W: This designation was given to 31 B-17Gs used by the U.S. Navy as the first airborne early warning aircraft (AWACS).

Fortress III[edit]

Eighty-five B-17Gs were transferred to the Royal Air Force, where they received the service name Fortress III. Three went to Coastal Command in the Azores fitted with radar before reuse with Meteorological squadrons. The rest were operated by two squadrons of Bomber Command's No. 100 Group RAF at RAF Sculthorpe from February 1944, where they were used to carry electronic countermeasures to confuse and jam enemy radar in support of bombing missions.[14] These Fortress III (SD)[15] would carry extensive array of equipment: the Monica tail-warning receiver, the Jostle VHF jammer,[16] Airborne Grocer air-interception jammers; Gee and LORAN for navigation, and an H2S radar replacing the chin turret. They were also used as decoys during night bombing attacks. They took part in various such operations until the units were disbanded in July 1945.


The XB-38 was a modification project undertaken primarily by the Vega division of Lockheed on the ninth B-17E built. Its primary purpose was testing the feasibility of liquid-cooled Allison V-1710-89 engines. It was meant as an improved version of the B-17, and a variant that could be used if the Wright R-1820 engine became scarce. Completing the modifications took less than a year, and the XB-38 made its first flight on May 19, 1943. While it showed a slightly higher top speed, after a few flights it had to be grounded due to a problem with engine manifold joints leaking exhaust. Following the fixing of this problem, testing continued until the ninth flight on June 16, 1943. During this flight, the third (right inboard) engine caught fire, and the crew was forced to bail out. The XB-38 was destroyed and the project cancelled. The gains in modification were minimal and would have been disruptive to production of existing models. Allison engines were also considered to be more badly needed for constructing fighter aircraft.[17]

Serial number: 41-2401


Prior to the introduction of the P-51 Mustang, a B-17 "gunship" escort variant called the YB-40 was introduced. This aircraft differed from the standard B-17 in that a second dorsal turret was installed atop the radio operator's position between the forward dorsal turret and the waist guns, where only an upward firing single or double Browning M2 had been mounted; and a single 0.50 in (12.7 mm) machine gun at each waist station was replaced by a pair of 0.50 in (12.7 mm) guns, of basically the same twin-mount design used for the tail guns. In addition, the bombardier’s equipment was replaced with twin 0.50 in (12.7 mm) machine guns in a remotely operated "chin" turret directly under the bombardier's position, augmenting the existing "cheek" machine guns; and the bomb bay was converted to a .50 caliber magazine. The YB-40 would provide a heavily armed gunship escort capable of accompanying the bombers all the way to a target and back. The aircraft was deemed a failure, however, because it could not keep up with standard B-17s once they had dropped their heavy bomb loads. It was withdrawn from service after just fourteen missions. (26 built: 1 XB-40 prototype, 21 YB-40 pre-production aircraft, 4 TB-40 training aircraft.)

C-108 Flying Fortress[edit]

Four B-17s were converted to serve as cargo carriers and V.I.P. transports under the designation C-108 Flying Fortress. (Many more served in the same roles under the designations CB-17 and VB-17, respectively.) The first of them, designated XC-108, was a B-17E partially stripped of military equipment and outfitted with various living accommodations. It served as a V.I.P. transport for General Douglas MacArthur. A similar conversion was made on a B-17F, which was redesignated YC-108. The third plane, designated XC-108A, was made to test the feasibility of converting obsolete bombers to cargo aircraft. B-17E 41-2595 was chosen for the conversion. Based in India, it ferried supplies over the Himalaya to the base for the B-29 Superfortress in Chengdu, China. It proved a difficult plane to maintain, due to lack of spare parts for the Cyclone engines, and was sent back to the United States, where it was based in Bangor, Maine, and flew a cargo route to Scotland until the end of the war. It was sold to a local dealer for scrap, but the airframe survived, and is currently being restored in Illinois. The final one was built under the designation XC-108B, and was used as a tanker to transport fuel from India to Chengdu.

F-9 Flying Fortress[edit]

An F-9/RB-17

Several B-17s were converted to long-range photographic reconnaissance aircraft, designated F-9 Flying Fortress. (The F- here stands for 'fotorecon' and must not be confused with F- for 'fighter', a term only used by the fighters of the U.S. Navy and Marine Corps before 1947; which was not introduced by the USAAF until after the war.)

The first F-9 aircraft were sixteen B-17Fs, with bombing equipment replaced by photographic equipment. Some of the defensive armament was kept. An uncertain number more were converted to a similar configuration to the F-9, but differed in minor details of their cameras, and received the designation F-9A. Some of these, along with more B-17Fs, received further camera alterations and became the F-9B. The last variant designation was the F-9C, which was given to ten B-17G, converted in a similar fashion to the previous planes. Those surviving in 1948 were at first redesignated RB-17G (R indicating 'reconnaissance').

  • FB-17: Post-war redesignation of all F-9 photo-reconnaissance aircraft.

BQ-7 Aphrodite[edit]

Late in World War II, at least 25 B-17s were fitted with radio controls to be used as drones designated BQ-7 missiles, constructed under the auspices of Operation Aphrodite. Loaded with up to 20,000 lb (9,070 kg) of Torpex high explosive and enough fuel for a range of 350 mi (563 km) they were used to attack U-boat pens, V-1 missile sites, and other bomb-resistant fortifications.

The BQ-7s would be taken aloft by two volunteer crew members, who would take it up to 2,000 ft (610 m), point it toward the target, and transfer control to another B-17. They would then bail out through the open cockpit while still safely over England. The controlling B-17 would follow the BQ-7, and lock its controls into a collision course with its target, then turn around to escape.

Because remote-control hardware available at the time was insufficient for the task, Operation Aphrodite was riddled with problems. Between August 1944 and January 1945 15 BQ-7 were launched against Germany, none ever hit its target, and several crew were killed in various parachuting accidents. One bomber left a 100 ft (30 m) crater in British soil and another circled an English port out of control. It was cancelled in early 1945.

PB-1 and PB-1W[edit]

The U.S. Navy (USN) received 48 B-17s towards the end of World War II, renamed PB-1 and used for maritime patrol missions. Post-war, the USN acquired 31 more B-17Gs, renamed PB-1W, and fitted with AN/APS-20 radar for Airborne Early Warning equipment and procedure development.

The Naval Air Material Center's Naval Aircraft Modification Unit (NAMU) at Johnsville, Pennsylvania modified the B-17s to PB-1W specification by sealing up the bomb bay doors and installing 300 gallon drop tanks on each wing, in addition to the “Tokyo Tanks” mounted in the outer wings, holding a total of 3,400 gallons of fuel, giving the PB-1W an endurance of 22+ hours. Initially PB-1W's retained the natural metal finish with a protective wax coat, but later the PB-1Ws were painted gloss Navy Blue overall.

The scanner for the one-megawatt AN/APS-20 Seasearch S-band Radio Detection and Ranging (RADAR), manufactured by Hazeltine Corporation/General Electric, was ventrally mounted in a bulbous housing below the redundant bomb bay, with the RADAR relay transmitter, Identification friend or foe (IFF), Radio Direction Finder (RDF), Instrument Landing System (ILS), and LOng RAnge Navigation (LORAN) also being installed during conversion.

The conversion introduced the following changes:-

  • Chin turret removed.
  • Norden bombsight removed.
  • Bombardier's station retained as a look out post, while on ASW or airborne search and rescue (SAR) missions.
  • Top forward turret removed.
  • Cockpit armour removed.
  • 300 U.S. Gallon drop tanks fitted under the outer wings.
  • Extra fuel tanks in the outer wings (“Tokyo Tanks”).
  • AN/APS-20 Seasearch S-band Radio Detection and Ranging (RADAR), with transmitter in the fuselage and aerial in a bulbous di-electric fairing under the former bomb-bay.
  • Modernised Identification, Friend or Foe (IFF).
  • Radio Direction Finder (RDF).
  • Instrument Landing System (ILS).
  • LOng RAnge Navigation (LORAN).
  • 2 RADAR consoles facing aft in the former bomb-bay
  • Radio Operators seat turned to face outboard.
  • Waist gun positions and ball turret removed.
  • Bench seats fitted for observers at the waist positions.
  • Floating smoke markers carried.
  • A latrine and a galley were fitted amidships.
  • Tail guns and armour removed.
  • Provision for spares and/or cargo to be carried in the tail section.

The crew for USN PB-1Ws consisted of 6 officers, (Pilot in Command, Second in Command, Navigator, CIC Officer, and 2 RADAR Operators/Controllers) and 5 enlisted men (Plane Captain (now referred to as Crew Chief), 2nd Mechanic, Electronics Technician, and 2 Radio Operators).

First delivered to Patrol Bomber Squadron 101 (VPB-101) in the spring of 1946, the Navy was eventually to have twenty two, out of thirty one post-war B-17s, fully upgraded to PB-1W standard. Late in 1946, VPB-101 would move to NAS Quonset Point, Rhode Island, and be redesignated Airborne Early Warning Development Squadron Four (VX-4).

Serial numbers:

  • PB-1: Bu34106
  • PB-1W: Bu34106; 34114; 77137/77138; 77225/77244; 83992/83998

SB-17G and PB-1G[edit]

SB-17G-95DL 83794
5th RS / D Flight

From 1943 to 1948, as part of Dumbo missions, 12 B-17Gs were converted to B-17Hs equipped with an airborne lifeboat and ASV radar for USAAF air-sea rescue duties. The US Coast Guard flew 17 similar aircraft as PB-1G's.

Serial numbers:

  • PB-1G: Bu77245/77257; 82855/82857

See also[edit]


  1. ^ Hess & Winchester Wings of Fame No. 6, 1997, p. 41.
  2. ^ Bowers 1989, pp. 291–292.
  3. ^ Hess & Winchester Wings of Fame No. 6, 1997, pp. 41–42.
  4. ^ GE Turbocharger Manual "Section XIV" for its B-17-applicable turbochargers, pgs. 113–140
  5. ^ Caidin, Martin (1968). Flying Forts: The B-17 in World War II. New York: Bantam Books. pp. 106–108. ISBN 9780553287806.
  6. ^ "Fortress I for RAF". last revised April 2004
  7. ^ [1]
  8. ^ Ethell, Jeff (January 1985). "Our Still-Flying Fortresses". Popular Mechanics. p. 124. Retrieved February 14, 2015.
  9. ^ Lyman, Troy (May 12, 2003). "B17 — Queen of the Sky — The B-17F". Troy Lyman's B-17 Flying Fortress Site. Retrieved June 24, 2014. "...factories were trying to fine a more effective solution to the B-17's lack of forward firepower...This solution was the Bendex Chin Turret. This turret had originally been used on the YB-40 gunship project. While this experiment proved unsuccessful, the chin turret was found to be a major improvement to the B-17's forward firepower. This turret was fitted to the last eighty-six B-17Fs to come off the Douglas assembly line starting with block B-17F-75-DL.
  10. ^ Graphic of usage and stowage positions for B-17G chin turret control yoke
  11. ^ B-17G Flying Fortress, History of, accessed December 20, 2009.
  12. ^ Cheyenne turret Archived August 22, 2016, at the Wayback Machine
  13. ^ Doyle, David (2021). B-17 Flying Fortress, Vol. 2: Boeing's B-17E through B-17H in World War II. Atglen: Schiffer Publishing, Ltd. p. 86. ISBN 9780764361296.
  14. ^ "Boeing Fortress", Royal Air Force Bomber Command 60th Anniversary
  15. ^ SD for "Special Duties".
  16. ^
  17. ^ Caidin, Flying Forts


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