The H series of the B-25 (and its Navy PBJ-1H equivalent) was an awesome airplane.
Built by North American Aviation (NAA) and used primarily during World War II from mid-1944 and into 1945, this series of the B-25 contained a 75-mm cannon in the nose, hand-loaded by the navigator-cannoneer, that was fired by the pilot simultaneously along with four .50-cal. machine guns also mounted in the nose (each with 400 rounds per gun), plus either two or four more machine guns mounted in blister packages on the sides of the cockpit (also with 400 rounds per gun). Designed primarily to be used for interdiction work against shipping and other fortified targets where a cannon could be deadly, the H series was the final development of testing begun by "Pappy" Gunn in the Pacific and first implemented in the B-25C1 "Commerce Strafers." The production B-25G that followed first employed the 75-mm cannon (the M-4) and was initially known as a fighter-bomber, before the AAF adopted that term for bombing fighters. The later B-25H retained the cannon, albeit a lighter version (the T13E1), which allowed for more forward-firing machine guns, plus additional armor plating to protect the crew.
The B-25H ended up not being used as much as planned. This was in principle due to its configuration as an attack bomber and changes in AAF tactics, its lack of factory dual controls, higher maintenance due to the wear and tear caused by the cannon, and a widespread lack of targets of the type needing the cannon (such as low altitude bombing missons common in mid- and late-1944 in the Pacific). Although tested by a variety of combat groups in mid-1944, those B-25H models that remained in combat were used by a few squadrons who specialized in this type of use, particularly in the South and Southwest Pacific and in Southeast Asia. The units that made more extensive use of the B-25H include: the 100th BS of 42nd BG (13th Air Force); the 498th BS of the 345th BG, squadrons of the 38th BG, plus the 418th Night Fighter Squadron, all of the 5th Air Force; squadrons of the 341st BG of the 10th and 14th Air Force in Southeast Asia, plus the 1st Air Commando Group of the 10th Air Force; and by the Marine Corps in the Central Pacific.
Only 1,000 B-25H planes were manufactured (including the Navy variant, the PBJ-1H), all built at the Inglewood factory of North American Aviation and assigned sequential tail numbers from 43-4105 through 43-5104. When there was a shortage of the newer light-weight cannon, Republic Aviation (of Evansville) finished several H-1 planes with the original heavier cannon as used in the G series; for these planes, the extra weight also meant a reduction of the nose guns by half. [See this webpage, http://home.att.net/~jbaugher2/b25_15.html, for details about the H series. Or for a summary on all the B-25 versions, try this webpage, http://www.vectorsite.net/avb25.html.]
Besides personally believing this series to be the best looking of all the B-25 production types, the H series also holds a particular interest for me due to two personal connections:
Below is a series of photographs that I've collected from various places on the web to both illustrate and pay tribute to this lesser known series of the B-25, followed by further data on wartime allocation of the H series. I will continue to add information and pictures as they become available. Enjoy!
I must give due credit to Phil Marchese for his important contributions to the above description of the H series, which also includes information from Joe Baugher's webpage, plus from other sources here and there on the B-25H and PBJ-1H.
The B-25H, in a NAA publicity shot of 43-4570 over the coast of Los Angeles. [11]
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A wartime picture of a B-25H assigned to the 100th BS(M), tail number 43-4498, christened "Dutch" by it's pilot (and named after his wife's nickname). The pilot is 1LT Donald C. Robertson (taking the photograh), and my Uncle Roy was his co-pilot (that is Roy in the white T-shirt, along with the crew's navigator, 1LT James Schaade, in the coveralls). This is a good full-length side view of the H model. This picture was taken in the Pacific, likely in July, August, or September 1944. [Photo courtesy of Donald Robertson, Jr.] [1]
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View of a B-25H from the other side, in what appears to be a stateside photograph at the Inglewood factory. This particular plane, tail number 43-4448, has the K-24 12-inch forward shooting camera installed in its nose, just above the machine guns. [2]
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A front view, showing its cannon and four nose-mounted machine guns, plus a good view of the pilot-side machine gun packages on the side of the cockpit and the armor plating protecting the pilot. With the sailor in the cockpit, this looks to be a photograph of the Navy/Marine Corps variant, known as the PBJ-1H. Note the armor plating covering part of the cockpit window to provide further protection for the pilot. This is a trademark of the H series (and earlier G types) that doesn't seem to appear with the later J series that followed. [2]
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Diagram from the B-25 pilot's handbook that shows the basic layout for the cannon in the nose of the B-25H. The cannon is mounted in what would be the crawlway under the cockpit to the glassed bombardier's nose in the other models of the B-25. The H series has a lighter cannon, the T13E1, and is a later design first developed in the field by "Pappy" Gunn and put into production originally by North America Aviation as the B-25G. [Here is a link to the similar diagram of the B-25G. The B-25G had only two front-mounted machine guns due to the heavier M-4 cannon. Some of the early H's were also configured with the heavier M-4 cannon when the lighter T13E1 was still short in supply.] [17 and 13]
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A three-quarter view from ground level. [8]
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Another front view picture. [2]
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The front of the airplane, looking straight on. The cannon and machine guns were bore-sighted to 1000 yards. Note the covering of flat-black paint on the top side of the nose and on the inner edges of the engine naceles, painted on what is otherwise a natural metal finish, to reduce glare for the pilot. (Also note the just-visible tail on the right side of the photograph showing tail number 43-4551, another B-25H.) [2]
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A close-up picture of the cannon and machine guns. Another characteristic identifying feature of most of the H series is the ram air vent, the "doohickey" protruding from the side of the nose, on the right side of the photograph, near the front and in line with and just below the cannon. The purpose of the ram air vent was to bring air into the nose of the airplane to help vent away the gases that accumulated from the firing of the machine guns and cannon. Many of the early H-series airplanes did not have this vent, nor is this vent found on the later J series with the 8-gun strafer nose, at least not in this position. [2]
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The guns in the nose being installed. By the paint scheme (light color beneath the nose and on the underside of the engines), this looks to be a Navy PBJ-1H. (See the color picture of the PBJ-1H for comparison.) [12]
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A B-25H being loaded by armorers at a field with both .50 cal and cannon shells. By the coincidental appearance of the one guy with the white cap, this could be taken of the same plane and location as several of the photos above. [18]
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The "business end" of the modern-day "Barbie III," the only known B-25H still flying today. Here you can see how the four machine guns were arranged and fed their ammunition. [The original "Barbie III," 43-4380, flew with the 1st Air Commando Group (see picture elsewhere on this page); the airplane today called "Barbie III" and painted to look like the original airplane by that name, is actually 43-4106, a stateside trainer. At least they used a real B-25H-1 to simulate another Block -1 airplane.][4]
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Starboard-side package guns, with the cover removed from one, showing how the gun was mounted and spent cartridges ejected. The charging handle was somehow accessible from inside, although stoppages, jams, or other problems couldn't be dealt with in flight due to the gun being outside of the airplane. Note also the extra plate on the fuselage by each muzzle to reduce flash damage to the plane. [15]
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The underside of the H series in flight. This particular picture and text was taken from the 42nd BG history book, published right after the war. A NAA publicity photograph, again showing 43-4570. [5]
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Another picture of the underside of a B-25H in flight. This is a very early Block -1 airplane, tail number 32-4110, the 6th B-25H made. [2]
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Another picture of the underside of a B-25H in flight, in this case a PBJ-1H of Marine Corps VMB-613 Squadron. I believe this may be "8-Ball" (MB-8, BuNo 35264). Note the mount points for rockets under the wing, the antenna that is part of the AN/APG-13A ("Falcon") targeting radar just above the nose guns, and the radome on the starboard wing tip holding the antenna for the AN/APS-3 ("Dog") search radar. Note also that the package guns are missing on the pilot side. [16]
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A great view of several H-series airplanes in right echelon flight. These planes are with the 1st Air Commando Group (10th Air Force). The closest planes are 43-4380, the original "Barbie III," and 43-4271, "Dolly." Both of these are the earlier Block -1 type, which only had package guns on the starboard ("co-pilot") side of the cockpit in addition to the four machine guns in front. (Pilot-side package guns were added starting with the Block -5 type, serial numbers 43-4405 and later). These earlier airplanes are also missing the ram air vent, mounted just off from the nose alongside the cannon on the pilot side, which brought added air into the plane to help vent gases from the fired guns (see the front-view pictures above.) The 1st Air Commando Group flew in support of the Burma Campaign in Southeast Asia. [2]
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A color photo of a PBJ-1H in flight, in its normal Navy three-tone blue paint scheme. One of the more successful users of the PBJ-1H in combat was Marine Corps Squadron VMB-613 in the Central Pacific, including use of the AN/APG-13A gunsight radar. [6]
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The top (dorsal) turret, shown with its guns in the stowed, rear-facing position. Previously mounted in the rear portion of the airplane, the turret was moved forward to behind the cockpit starting with the H series and continued with the later J series. This is a redesigned turret (compared to that used in earlier B-25s), taller, with better visibility and a streamlined design. Moving the turret forward helped with weight distribution, plus also brought two more forward-firing guns to bear during strafing attacks, bringing the total to ten plus the cannon. [2]
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The waist guns and tail turret being serviced at the Inglewood factory. [12]
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A side-view cutaway drawing showing the basic layout inside the B-25H. The early planes of this series, the Block -1 and -5, could carry an aerial torpedo, which was done away with in the later Block -10 type. [9]
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An excellent color cutaway drawing showing the basic layout inside the B-25H. Designed for a crew of five - pilot, navigator-cannoneer, flight engineer-top turret gunner, radio operator-waist gunner, and armorer-tail gunner - most units flew with a crew of six, adding a co-pilot (with the pilot also functioning as "bombardier.") [10]
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Top view of a B-25H painted in overseas colors (a dark green). This is an early Block -1 type as it has only the package guns on the starboard side of the cockpit, and not on the port/pilot-side. [14]
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A picture from the pilot's manual, showing the instrument panel and cockpit of the B-25H/PBJ-1H. What distinguished the H series from all other B-25s was the lack of factory installed dual controls for a co-pilot. This was a very controversial design desision made by the higher brass in the War Department, right up to General "Hap" Arnold himself, chief of the Army Air Forces, which was another reason why the combat folks didn't particularly like the H model. In place of the co-pilot was a jump seat intended to be used by the navigator, but in reality often used by a second pilot, as the 100th BS and other groups in the Pacific still flew with a co-pilot who traded places with the pilot on long flights. Dual controls were added back to the production J and later types, but apparently many H's were also field and depot modified to include dual controls. [3]
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The gun sight used by the pilot to target the machine guns and cannon, as well as for skip bombing. This particular sight, the N-3B, had to be manually adjusted by the pilot as the plane approached the target to account for the decreasing range and effects of gravity. The War Department also experimented with a forward-looking radar gun sight, the AN/APG-13 "Falcon," that could remotely adjust the sight based on adjustments made by the radar operator sitting to the pilot's right. Used by the Navy/Marine Corps, and also by the 14th Air Force, the radar gun sight worked best against shipping targets without a "cluttered" background to confuse the operator. To the best of my knowledge, none of the 13th and 5th Air Force units in the South Pacific used the radar sight, whereas it was used by both the 341st BG of the Army Air Forces and VMB-613 Squadron of the Marine Corps. (If you are curious about the radar gun sight, see this webpage: http://www.riemarfamily.com/falcon%20in%20action.html.) [3]
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Another view of the cockpit, from a slightly higher angle, with covers over the electronics below the panel. This is of the H-series as originally manufactured, still with only one set of flight controls. [15]
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An excellent view of the area behind the flight deck, looking forward. The photographer would have been standing immediately below the top turret, the domain of the flight engineer. This is also where the navigator (who was also the cannoneer) would have sat if there were two pilots on the flight. The large "box" on the left of the photo, about halfway up, is where 21 live cannon shells would have been stored, three rows deep of seven shells across. Immediately below that would have been the loading mechanism of the 75-mm cannon, which doesn't seem to be installed (as I can see light shining down the open crawlspace underneath the pilot's seat). The cannon sat in the crawlspace that in the J and other models with the glassed nose was the way to the bombardier's station up front (which the H didn't have). Opposite the shell box is the light-colored metal "seat" the cannoneer would have used while loading the weapon. Empty hot shell casings would have collected on the floor during the attack run. [15]
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The radio operator/waist gunner's position, just aft of the bomb bay. This photo is looking forward, toward the bomb bay. (In this particular photograph, the crawlspace over the bomb bay, connecting the front and rear portions of the airplane, is being obscured from view by a canvas covering.) [3]
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Another view of the radio operator/waist gunner's position. This photo is looking aft, toward the rear of the plane. The guns are offset from each other (the starboard side window being forward of the port side window), so two gunners could conceivably be here at the same time. [3]
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Another rear-facing view from the gunner's area, looking toward the tail, and wide enough so you can see out the waist gunner's windows. [15]
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The B-25H introduced a new and improved tail gunner's position, with better visibility, armor plating, and a power-operated gun turret with two .50-cal. machine guns. This same improvement was carried forward into the later and more popular J series. This is a view of the interior of the gunner's position, looking aft. The guns themselves are behind the armor plating protecting the gunner, with the gunner not touching the guns directly. [3]
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Top view of the tail gunner's area. You can see how thick the armor plating was that protected the gunner's chest and lower body. And you can see the long feed mechanism for ammo to the guns, which starts behind the gunner and winds all the way to the guns as shown in the next photo. [15]
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Finally, the business end of the tail guns, with the coverings removed and showing the cartridge feed system. The B-25J's tail would be identical. [15]
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More pictures will be added as I find them....
During the war, nothing was manufactured without having a defined use in mind, and only then if the priority of use was high enough to command the precious resources needed, including the factory workers. This was no different for military equipment (which clearly had priority over household goods), where even their production was in competition with other military goods for priority in manufacturing and allocation to a specific combat theatre or stateside training use. These allocations continued to change as the war progressed. Airplanes such as the B-25 were assigned to projects that identified each airplane's destination based on a perceived priority of need. In the case of the B-25H, project assignments were made from priorities seen during the latter half of 1943 and the first half of 1944, the time period over which the plane was built. Some of these project allocations were to areas of combat, others to stateside training uses, plus some allocation to another country.
Phil Marchese of Pennsylvania did research in the 1980s on all the B-25s manufactured during the war, looking at where they were used and the modifications they received. For the 1,000 airplanes of the B-25H series that were built (also known as the NA-98 for production purposes), below is their distribution according to destination or project allocation as recorded on each airplane's Individual Aircraft Record Card (IARC):
One-tenth of the B-25H allocation was to the Chinese Nationalist Air Force, with another fourth of the NA-98 production built as PBJ-1H's for the Navy and Marine Corps. Of the remaining, allocated to the Army Air Forces, it is clear from this tabulation that the majority of B-25H bombers were sent to units in the Pacific Theater of Operations (PTO), with the single largest combat allocation going to units in the CBI and Southeast Asia. The next biggest AAF combat allocation was to South and Southwest Pacific, to those units of the 5th and 13th Air Force that were also operationally combined later in the war as the Far East Air Forces (FEAF). One must remember, however, that these are allocations and shipments of airplanes; many of these airplanes, while shipped to their combat zone, in reality did not get used in combat due the changing nature of the conflict and need [or lack thereof] for a cannon-firing strafer.
If you are still interested, here is further background information on the 1,000 B-25H models that were built, including the Navy PBJ-1H variant, as well as some other resources:
A Photo Tribute to the B-25H Series
