Boeing YB-40 Flying Fortress

This article is about the military aircraft. For the Vietnamese variant of the RPG-2 see B-40

The Boeing YB-40 Flying Fortress was a modification of the 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 not yet available to accompany bombers all the way from England to Germany and back.

Development

Initial work on the project began in September, 1942 with the XB-40 prototype, built by Lockheed's Vega subsidiary. The first order of 13 was made in October. 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.

The aircraft differed from the standard B-17 in that a second dorsal turret was installed in the former radio compartment (between the top turret and the waist guns); the single 0.50-calibre (12.7 mm) machine gun at each waist station was replaced by a pair of 0.50-calibre (12.7 mm) guns, with a mount for each pair of these being very much like the tail gun setup in general appearance; and the bombardier's equipment was replaced with two 0.50-calibre (12.7 mm) machine guns in a "chin" turret. The existing "cheek" machine guns, initially removed from the configuration, were restored in England to provide a total of sixteen and the bomb bay itself was converted to a magazine. However a significant portion of the 4,000 pound weight increase came from armor plates installed to protect crew positions. 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 feet in 25 minutes, the YB-40 was rated at 48 minutes.

Operational history

The YB-40's mission was to provide a heavily-gunned escort capable of accompanying the bombers all the way to the target and back. Overall the concept proved a failure because the YB-40 could not keep up with standard B-17Fs, particularly after they had dropped bombs. Of the initial order of 13, one was damaged in a forced landing on the Isle of Lewis en route to England, and the remaining 12 were assigned to the 92nd Bomb Group (H) and designated the 327th Bomb Squadron.

Between May 29 and August 16, 1943, the YB-40 flew 14 of the 19 combat missions scheduled by the 8th Air Force, although on the mission of June 26 all the YB-40s scheduled were unable to complete assembly and returned to base. Altogether of the 59 aircraft despatched, 48 sorties were credited. 5 kills and 2 probables (likely kills) were claimed on the 13 missions flown, and one YB-40 was lost, shot down by flak on the June 22 mission to Hüls, Germany. Tactics were revised on the final five missions by placing a pair of YB-40's in the lead element of the strike to protect the mission commander.

One YB-40 of the second order, reflecting modifications requested during combat trials to lighten the aircraft, joined the 327th in October, 1943, but by then B-17G models were beginning to appear and the final YB-40 was not flown in combat. All the deployed YB-40s were returned to the United States and converted to training aircraft, as were 11 aircraft of the second order.

One of the most unusual stories involving the use of a YB-40 was to try and trap an Italian pilot, Guido Rossi, who had begun to offensively fly a captured P-38 Lightning fighter that had been forced to land, low on fuel, over Sardinia in the spring of 1943. Rossi's scheme was to use the P-38 as a supposedly "friendly" aircraft, that he would use to first draw in, then shoot down, crippled American aircraft. Lt. Harold Fisher, a USAAF bomber pilot who had been victimized by Rossi's still-American-marked P-38, was able to get the use of a YB-40 to try and turn the tables on the Italian pilot. On August 31, 1943, Rossi appeared in the sky in the general vicinity of the YB-40, and Fisher drew Rossi in with radio conversation-eventually the Italian pilot became furious at one of Fisher's statements, and the attacking P-38 fell apart from the hail of bullets from the YB-40's guns. This event was documented in the pages of aviation author Martin Caidin's book "Flying Forts", about B-17 action in WW II Europe.[1],[2]

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: the chin turret, off-set waist gun positions, and a lightweight tail position.

Operators

United States

United States Army Air Force

Specifications (YB-40)

General characteristics

Crew: 10

Performance Armament

Guns: 14 (or more) × .50 in (12.7 mm) Browning M2 machine guns. Typically used 14-16, with room for up to 30.

Location	Rounds
Nose	2200
Front top turret	2500
Aft top turret	3300
Ball turret	300
Waist guns	1200
Tail guns	1200
Total	10,700

References

Freeman, Roger A. (1990). The Mighty Eighth War Diary. ISBN 0-87938-495-6.
Freeman, Roger A. (1991). The Mighty Eighth War Manual. pp. 154–155. ISBN 0-87938-513-8.
Bishop, Cliff T. (1986). Fortresses of the Big Triangle First. pp. 69, 73, 246–247. ISBN 1-869987-00-4.
Encyclopedia of American Aircraft
USAF Museum article on YB-40