Defense Media Network

Brilliant Mistakes: The YB-40

The YB-40 gunship was both more and less than planners expected


We are reminded ceaselessly of how crucial breakthroughs like bronze weapons, longbows, the stirrup, gunpowder, rifles, the airplane, the submarine, the machine gun, and many other technologies changed the face of warfare and often became deciding factors on the battlefield. Not mentioned as often are the failures, the brilliant ideas that were not so brilliant, the technological dead ends, the badly conceived or badly employed weapons that either had no effect or actually contributed to defeat. “Brilliant Mistakes” is a continuing series covering failed concepts, weaponry, tactics, and strategies, all of which probably seemed like a good idea at the time.

Today, historians have a wealth of knowledge about the YB-40, the World War II aircraft that appears to qualify as the U.S. Air Force’s first gunship.

This modified B-17F Flying Fortress bristled with gun barrels and was sent forth to guard American bomber formations high over Europe. What is missing from its history is the name of its creator. Who thought up the YB-40?

The AAF launched a program for a “flying destroyer” or “flying hedgehog” that would guard against Luftwaffe fighter attacks by filling the sky with a giant storm of machine-gun rounds.

“The record is unclear,” said Rob Young, a historian at Wright-Patterson Air Force Base, Ohio. “It appears the YB-40 meets the definition of a donkey – that is, a horse designed by a committee.”

YB-40 diagram

This is a diagram of the YB-40, showing a very heavily armed aircraft that rightly deserves to be called a gunship. Robert F. Dorr Collection

During the early period of the bombing campaign in Europe in 1942 and 1943, aggressive Luftwaffe fighter pilots began attacking American bombers from straight ahead at five degrees above the centerline, the position the Americans called “Twelve o’clock high” and where the fewest guns could be brought to bear against the attacking fighters. This tactic was intended to knock a bomber out of the sky by killing its pilots – and it worked. At one juncture a bomber crew was said to have at best a fifty-fifty chance of surviving its assigned 25 missions. Long-range fighters were not yet available to escort the bombers to their targets, so the Army Air Forces, or AAF – predecessor of today’s U. S. Air Force – searched for another way. 

The AAF launched a program for a “flying destroyer” or “flying hedgehog” that would guard against Luftwaffe fighter attacks by filling the sky with a giant storm of machine-gun rounds. In August 1942, the AAF contracted with Vega Aircraft Corp. to modify the second production B-17F (aircraft no. 41-24341) to become the first XB-40. The aircraft probably should have been given a “P” for “pursuit” designation because it was now more like a fighter than a bomber and no longer had a bomb bay, bombs, or bombardier.

Vega fitted the aircraft with a chin-mounted nose turret – later to become standard on B-17G Flying Fortress models – and an additional Glenn L. Martin turret at the rear of the dorsal cockpit fairing where the radio operator’s single .50 caliber machine gun was usually mounted. Likewise, the waist gunners’ single .50s were replaced by twin mounts. Ammunition supply was almost triple that of a standard B-17F, some 11,275 rounds compared to 3,900 rounds on a B-17F.


This is the first XB-40 gunship (aircraft no. 41-24341) at Wright Field, Ohio in early 1943. Robert F. Dorr Collection

The XB-40 made its first flight on Nov. 10, 1942. It’s significant that this was just a month ahead of the Rolls-Royce Merlin-powered P-51B Mustang, which would end up protecting bombers using different methods.

With its added guns and triple load of ammunition the YB-40 was ungainly, bulky, tail-heavy and unmaneuverable – the whole nine yards and more.

The XB-40 (X for “experimental”) was followed by an order for 13 YB-40 aircraft (Y signifying “service test”), which had minor differences but were equally heavily gunned and were meant to escort bombers all the way to their targets and back.

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Robert F. Dorr is an author, U.S. Air Force veteran, and retired American diplomat who...

    li class="comment even thread-even depth-1" id="comment-6902">
    Dwight Jon Zimmerman
    Dwight Zimmerman

    I remember Martin Caidin’s account. Fascinating tale. Too bad it seems to be more a piece of fiction. The interesting thing was that the people in charge used as their platform the B-17 instead of the DC-3.

    li class="comment byuser comment-author-chuck-oldham odd alt thread-odd thread-alt depth-1" id="comment-6904">
    Chuck Oldham (Editor)

    If you liked Martin Caidin’s account, you might also enjoy Renegade Lightning by Robert Skimin and Ferdie Pacheco. If the second name sounds familiar, yes, that’s Ferdie Pacheco, Muhammad Ali’s fight doctor, a Tampa native who’s written a couple of great memoirs and is also a very talented painter.

    li class="comment even thread-even depth-1" id="comment-34264">
    David Stubbs

    An interesting question is whether the Americans thought up the idea of the YB-40 or was the idea planted in Eaker’s mind by the British. Tami Davis Biddle (Tami Davis Biddle, Rhetoric and Reality in Air Warfare: Princeton NJ, Princeton University Press, 2002 pages 118-119) noted that In 1936 Sholto-Douglas thought that: “My own feeling on the matter is that the bombers should be able to look after themselves without the addition of an escort fighters” (sic): although certain of the bombers might be more heavily armed than the remainder at the expense of their bomb load”

    Given Sholto-Douglas was C-in-C Fighter Command from Nov 1940 to Nov 1942 he may well have influenced Eaker towards the same idea, with the result being the YB-40 …..and the delay of the Mustang project. Sholto-Douglas was replaced, as CinC Fighter Command by Leigh-Mallory until Nov 1943, and he too might have influenced Eaker.

    Eaker called a proposal to study the possible use of the P-51 Mustang as a long-range escort “premature” in June 1943 and as late as October 1943 thought that a big enough formations wouldn’t need escorts. He only assigned the drop tank project a priority of four. When drop tanks for the EIghth Air Force’s P-47s finally began to trickle in during the summer of 1943, Eaker still hesitated to make greater use of fighter escorts. And only with Arnold’s decision to remove Eaker as commander of the Eighth Air Force in December would there be the determination to use this new tool, which by now all of the bomber commanders, but Eaker, had finally recognized as essential. (Budiansky, Air Power, London, Penguin, 2004, page 325)

    The $64,000 question is did these RAF officers influence Eaker and if so is this why Arnold replaced Eaker with Doolittle? Any ideas?