28 June 2012

The Genesis of the B-25 Mitchell Strafer-Bomber

The first strafer package installed on a B-25 Mitchell.
The first half of 1942 in the Pacific were dark days for the Allies. With the loss of the Philippines and the Dutch East Indies and the fall of Singapore in February, Allied forces fell back in the face of the Japanese, seeking refuge in Australia to regroup for the offensive. Australia would soon become the base of operations for General Douglas MacArthur's South Pacific offensive as war materiel from the United States along with personnel began to flow in via a logistical supply line stretching from California via Hawaii and Fiji. It was via this route that the first North American B-25 Mitchell medium bombers began to arrive in Australia- rather unusually, though, the first B-25s to arrive were earmarked for the Dutch and were accompanied by Jack Fox, North American's field service representative. With ten brand-new B-25s present, it wasn't long before some back room dealings resulted in the B-25s along with Jack Fox being transferred to the US Army Air Forces at their new base in Charters Towers which was built in only six weeks by the Australians. Arriving at Charters Towers, Fox saw "his" B-25s arriving with American crews which was unusual as few pilots had been checked out in the new bomber. Fox queried one of the arriving pilots who gruffly responded "Who needs checking out? The damn thing has a stick and throttle, doesn't it?"

That was the legendary Captain Paul "Pappy" Gunn that Fox had just met. A retired Navy flight instructor, Gunn was living in the Philippines working for Philippine Air Lines when the Japanese invaded. Managing to assist the ultimately futile battle against the Japanese, Gunn managed to fall back to Australia where his intimate knowledge of the Philippines was put to use with an immediate commission in the USAAF. Gunn's initial meeting with Fox would be the start of the development of some of the most lethal aircraft fielded against Japanese forces in the South Pacific, the "strafer-bombers". But before we move on, we have to back track a little bit to January 1942 and back to the United States when the tactics of a minimum altitude bombing attack on ships and troops were being discussed within the USAAF. Soon tests were underway at Eglin Army Air Field in the Florida panhandle to develop the technique. By this time the USAAF in the South Pacific under General George Kenney, head of the Thirteenth Air Force, recognized the low-level attack virtues of the Douglas A-20 Havoc and North American B-25 Mitchells, roles they were not originally designed to perform. But Kenney was dissatisfied with the armament and bombs of the two attack aircraft as they weren't completely suited to how he wanted to employ them. 

With flight tests at Eglin AAF and with Kenney's own aircraft in Australia, skip bombing was developed which involved a low level approach against the heavy defensive fire of the Japanese ships. Lacking proper American fuses to perform skip bombing, Kenney had Australian fuses which were longer substituted on the bombs. With A-20 and B-25 crews training locally on skip bombing, the first attacks were found to be more successful if combined with Australian Beaufighters which strafed the ships to kept the defensive fire to a minimum. It was at this juncture that Pappy Gunn enters the picture. He had come up with a field modification for the A-20 that put a battery of four fifty-caliber guns in the nose since a bombardier wasn't needed on low level attack runs. This way skip bombing and strafing could be combined in a single aircraft. The results were better, but extra fuel tanks had to be installed in the Havoc's bomb bay to increase its range, which in turn reduced its bomb load. By by the summer of 1942 A-20s were in short supply as A-20 deliveries to the Russians were increasing.

"Pappy's Folly" with Pappy Gunn at the helm.
And that's when the B-25 entered the picture. It had longer "legs" than the Havoc and could carry a heavier load. Early skip bombing missions had already shown the B-25 eminently suitable for the role. Gunn and Fox come up with a field modification with General Kenney's blessing that put four fifty-caliber guns in the nose section with plenty of ammunition as well as an additional two pairs of fifty-caliber guns on external blisters on each side of the forward fuselage. By the summer 1942 Jack Fox issued a memo to all the other North American field reps in the South Pacific on how to modify the B-25 into a strafer-bomber. North American dispatched an engineering team to the field depot which was located at Eagle Farms in Brisbane to further assist Pappy Gunn and Jack Fox in their development work. The first B-25 Mitchell modified as a strafer-bomber was aptly named "Pappy's Folly" and personally flight tested by Gunn himself as well as Jack Fox. Working out the bugs, General Kenney then sent the two men and "Pappy's Folly" up to Port Moresby closer to the front lines for more testing. By February 1943 the North American team at Eagle Farms converted twelve more B-25s which were then assigned to crews with the 90th Bombardment Squadron in Port Moresby. Tactics were worked out and crews trained on a wrecked ship off the coast of Port Moresby- a pair of B-25s would approach enemy ships at 1,000-1,500 feet and then drop to 500 feet or lower on the final run in to the target. One Mitchell would open up with its gun battery to suppress the defensive fire while the other Mitchell would drop a string of three 250-lb bombs in a skip bomb attack. After the first pass, the pair returned for a second run, this time switching roles. 

During the first half of 1943 General Kenney's "commerce destroyers" wreaked havoc on Japanese shipping in the Bismarck Sea that supported the Imperial war machine. Soon airfields also came under attack by the strafer-bombers dropping 23-lb fragmentation bombs slowed by parachutes- "parafrag" bombs. They would soon be a decisive force in the campaign in the Southwest Pacific on the road back to the Philippines. 

Source/Photos: B-25 Mitchell: The Magnificent Medium by Norm L. Avery.  Phalanx Publishing, 1992, p95-103.

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