Boeing XB-39 Superfortress

The Boeing XB-39 was an experimental project to evaluate the substitution of the Allison V-3420-17 inline engine for the Wright R-3350 radials on a B-29 airframe, should the R-3350 run into insurmountable engineering or supply issues.
The airframe selected was the first YB-29 developmental aircraft, 41-36954. The aircraft was camouflaged in the standard USAAF Olive Drab over Neutral Gray scheme. Note the forward turret is equipped with only two .50 caliber machine guns instead of the later four-gun turret.
The Allison V-3420-17 was a 24-cylinder inline, basically made by joining two Allison V-1710 engines to a common crankcase. It was a successful design with a 1:1 power to weight ratio.
The Fisher Body division of General Motors was selected for the work due to their experience in developing the XP-75 Eagle long-range fighter, a design which also was to use the Allison V-3420. 41-36954 was christened “The Spirit of Lincoln” and conversion work began at Fisher’s Detroit plant.
Technicians are seen at work on the engine nacelle in this page from a Fisher’s brochure. Modelers should note that the Olive Drab paint has been worn off the wings around the new nacelles, which have been left in natural aluminum and that the leading edge fairings on the wings have been removed.
The result was an attractive aircraft with a hybrid finish of new natural aluminum components added to a camouflaged airframe.
The planned General Electric superchargers were not ready when the first flight was made on 09DEC44. In spite of the lack of superchargers, the XB-39 was able to surpass 400 mph, demonstrating the validity of the concept.
An interesting photograph of the undersides of the XB-39 in flight. The horizontal tail surfaces and rudder have been replaced, and the starboard aileron has had its outer surfaces removed revealing the internal structure. This was sometimes done to solve aerodynamic flutter but it is not clear if that was the reason in this case.
This photograph shows off the engine nacelles to good advantage.
Despite the success of the conversion, the decision was made to continue B-29 production using the R-3350 radials, as the issues with the radial engines were being rectified and supply chain issues did not materialize. The Spirit of Lincoln would remain the only B-39 ever constructed.

Countdown 1945 Book Review



Countdown 1945: The Extraordinary Story of the Atomic Bomb and the 116 Days That Changed the World

By Chris Wallace with Mitch Weiss

Hardcover in dustjacket, 320 pages

Published by Avid Reader Press June 2020

Language: English

ISBN-10: 1982143347

ISBN-13: 978-1982143343

Dimensions: 6.1 x 1.1 x 9.2 inches

Countdown 1945 is the story of the final efforts in the deployment of the atomic bomb at the end of the Second World War.  The chapters are arranged chronologically counting down from 116 days before the Little Boy Device was dropped over Hiroshima.  The 116 day point is the day that President Roosevelt died, and the day that President Truman was sworn in and first learned of the American effort to develop nuclear weaponry – a good place to start the narrative.

The Manhattan Project was an enormous undertaking and was conducted in great secrecy.  It employed over 130,000 workers in various capacities, many of whom had no idea what they were working on until after the Japanese surrender.  The project started with a letter from Albert Einstein to President Roosevelt in August 1939, advising of the theoretical possibility of developing nuclear weapons and warning of German interest in doing so.  The obstacles standing between that letter and a deployable weapon were considerable:  America did not possess the high-grade Uranium ore required for a device (that would come from Canada); the equipment to purify the Uranium did not exist; while the device was theoretically possible none of the scientific or engineering work required to make a physical device had been started; the aircraft which would ultimately be capable of delivering the atomic bomb, the B-29 Superfortress, had not yet been designed; the base needed to support the B-29s had not been built – in fact the location for the base, Tinian in the Marshal Islands, was in Japanese hands.  All of these obstacles would be overcome in the next six years.

The organization of the book in a countdown format allows the authors to focus on the most important events while also facilitating shifts in perspective.  One of the most important and interesting perspectives is that of President Truman himself.  Initially surprised by the existence of the program, the decision to use or not use the weapon was his.  In addition, he had to decide how much information to share with Stalin and whether to warn the Japanese before the device was used.  The lead scientist, Robert Oppenheimer, struggled with scientific and later moral questions.  Major General Leslie Groves had the herculean task of keeping all the various efforts scattered across the country secret and producing results.  Colonel Paul Tibbits led and trained the bomber crews who would ultimately deliver the weapons.

There are also some narratives introduced to represent the common man and put the story into a more personal perspective.  Ruth Sisson operated a calutron machine which was used to purify the Uranium.  She knew her job was part of the war effort but had no idea what the machine she was operating did – her concern was the safe return of her fiancé who was a medic with the Army in Europe.  Draper Kaufman was a U.S. Navy Commander and leader of a UDT unit which would go in before the amphibious assault on Japanese island of Kyūshū to clear beach obstacles.  The invasion was scheduled for November 1945.  American casualties were expected to surpass the total losses already experienced in the war to that point, Japanese casualties were expected to number in the millions.  Hideko Tamura was a Japanese schoolgirl who survived the bombing of Hiroshima, studied in the United States after the war and married an American.

There were a few minor errors which distracted from an otherwise excellent effort.  One caption describes Colonel Tibbits standing in front of his B-17 in Europe but the aircraft is clearly a B-29.  Another passage indicates that a Kamikaze strike on the Fletcher-class destroyer USS Callaghan (DD-792) killed all 47 members of her crew.  The Callaghan was sunk on 29JUL45 and was the last U.S. ship to be lost to a Kamikaze attack.  47 crewmembers were killed, but 282 of her total complement of 329 survived.  Minor errors, but easily fact-checked and avoided.

Overall, I did enjoy the book and the presentation.  I can recommend it, I found the insights into Truman’s roles in both the Manhattan Project and the diplomatic efforts at the end of the war particularly fascinating.  This week marks the seventy-fifth anniversary of the first uses of atomic weapons in warfare.  Given humanity’s propensity for destruction it is remarkable that the atomic bombings of Japan remain unique events, we can all hope that always remains the case.





Academy Boeing B-29 Superfortress in 1/72 Scale

One of the bigger WWII era kits in 1/72 scale is Academy’s Boeing B-29A Superfortress.  Airfix issued one around 1970 or so, and Academy first released theirs in the early 1990’s.   Academy re-released their kit again with markings for camouflaged subjects.  It’s huge when built up – a 16.5 inch ( 41.9 cm) length and a 23.5 inch (59.7 cm) wingspan.

The model depicts Joltin’ Josie the Pacific Pioneer which was the first B-29 to land on Saipan on 12OCT44, piloted by General Haywood S. Hansell and Major Jack Catton. Hansell headed the XXI Bomber Command. Catton was a flight leader of the 873rd squadron in the 498th Bomb Group.  After logging 400 flight hours and 24 missions over Japan during which Josie never suffered an abort and always hit the primary target, Major Catton was transferred to General Curtis LeMay’s Headquarters. Captain Wilson C. Currier took over as aircraft commander.  Josie was lost on the first mission following Major Catton’s departure. Immediately after taking off on 1 April 1945, she plummeted into Magicienne Bay and exploded on impact. There were no survivors.