Lessons Learned Designing and Building the XB-19 Were Applied to the B-29 and the B-36
The Douglas XB-19 was the largest four engine propeller-driven aircraft ever flown. It was the largest American aircraft flown until the Consolidated B-36 Peacemaker appeared in 1946. Until then it dwarfed almost every other aircraft in the world by a considerable margin, and wasn’t much smaller than the B-36. But even though only one example was built and the design never went into production, a considerable amount of the engineering required to get the aircraft in the air was later applied to the Boeing B-29 Superfortress as well as the Peacemaker. And Project D definitely took the best Douglas had.
Top Secret Project D
Project D was a Top Secret US Army Air Corps project intended to push the outside of the envelope; to discover what the limits of aeronautical engineering were when it came to long-range bomber aircraft. Project D began on 5 February 1935. Only Douglas and Sikorsky showed interest in the project. The Douglas design received the designation XBLR-2 (Experimental Bomber Long Range-2) on 9 July 1935. Sikorsky’s design was designated XBLR-3. Douglas built a huge new hangar to house the project. Wooden mockups of both designs were inspected in March of 1936.
Bigger Takes Longer
The Douglas design was chosen over the Sikorsky XBLR-3 design and work on the XBLR-2 continued, albeit slowly. The original completion target was 31 March 1938. This proved to an unrealistic goal. One reason was the gigantic aircraft was to be equipped with fully retractable tricycle landing gear- a first for an aircraft of such size and weight. Add to that the state of the economy (and lack of funds for aeronautical research and development) during the late 1930s, and the other challenges associated with designing and building such a massive aircraft, and delay after delay beset the program.
Delays Delays Delays
Another challenge was the powerplants intended for use on the XBLR-2. As originally drawn the aircraft was to be powered by six engines of at least 2,000 horsepower each. By the time construction began the bomber was to be powered by four Allison XV-3420-1 V24 cylinder liquid-cooled inline engines. The XV-3420 was essentially a pair of Allison V-1710 V12 cylinder liquid-cooled inline engines co-mounted and coupled together via a gearbox to drive a single propeller. But on 2 November 1936 Douglas decided instead to use four Wright R-3350 Duplex-Cyclone 18 cylinder air cooled radial engines instead of the Allison powerplants. Delays delays delays.
Funded, Then Nearly Cancelled
Now designated the XB-19, the big Douglas bomber was finally funded 8 March 1938. Douglas, already working on other designs that would eventually help win World War II, and straining to manage all of the critical work, recognized the limited benefit of continuing work on the XB-19. Douglas actually recommended cancellation of the project, but the US Army Materiel Division wouldn’t quit on the the XB-19. But they did remove the XB-19 from the list of secret projects in 1940. This resulted in quite a bit of attention from the aviation press.
One of a Kind Monster
When completed in May of 1941, the XB-19 was a low-winged monoplane sitting on single-wheel tricycle landing gear with a wingspan of 212 feet, wings that were tapered with a straight trailing edge and swept back leading edge, a conventional empennage, and a maximum gross weight of 162,000 pounds. The XB-19 was powered by those four nacelle-mounted Wright R-3350-5 radial engines rated at 2000 horsepower each at takeoff, turning three-bladed constant-speed propellers 17 feet in diameter. Total internal fuel capacity was 10,350 US gallons and could be augmented with an 824 gallon tank in the bomb bay. The XB-19’s maximum 37,100 pound ordnance payload could be carried in the bomb bay and/or on up to ten underwing racks.
Firepower Aloft
The XB-19 was designed to fairly bristle with defensive firepower. 37 millimeter cannons and .30 caliber machine guns were to be mounted in nose and forward dorsal turrets. Single .50 caliber machine guns were to be mounted in the tail, rear dorsal turret, ventral turret, and waist gunner’s positions on either side of the fuselage. Single .30 caliber machine guns were to be mounted on both sides of the nose and just forward of both horizontal stabilizers aft. The XB-19 was to be crewed by a total of 16- pilot, copilot, aircraft commander, navigator, flight engineer, radio operator, bombardier, and as many as nine gunners.
First Flight to the Army
The 55 minute first flight of the XB-19, USAAC serial 38-471, took place on 27 June 1941. The ginormous bomber was flown from Clover Field in Santa Monica over the March Army Airfield near Riverside so the Army Air Corp could begin evaluating it. Thirty hours of flight test time later, the XB-19 was tentatively accepted in October of 1941. But the attack on Pearl Harbor changed things up. The XB-19 was painted in olive drab over gray camouflage, its defensive armament was installed, and only four more test flights were conducted out west before the aircraft moved to Wright Field in Dayton, Ohio on 23 January 1942.
Initial Testing
It wasn’t until modifications, including the addition of improved brakes, took place that the Army Air Corps formally accepted the XB-19 during June of 1942. With the exception of engine cooling challenges, which required the engine cooling flaps be kept open during long flights, requiring a 20 mile per hour reduction in maximum speed at 15,700 feet, the XB-19 proved to be relatively trouble-free during subsequent test flights.
Fitted With the Original Engines
Ironically after the the XB-19 completed its flight testing in 1943 it was fitted with four 2600 horsepower Allison V-3420-11 turbo-supercharged twenty-four cylinder liquid cooled engines turning four bladed propellers 19 feet in diameter. These engines were the production version of the engine that had originally been specified for the aircraft. After the engine mods the designation of the aircraft was changed to XB-19A. The XB-19A’s maximum speed rose by 50 miles per hour to 275 miles per hour- still far slower than that of the B-29 and the eventual B-36. The XB-19A was then modified for use as a cargo carrier and flew critical war materiel back and forth across the country for the duration of World War II.
The End of the Giant
The XB-19A made its last flight on 17 August 1946 when it was flown from Wright Field to Davis-Monthan Field in Arizona and placed in storage. It was scrapped there in June of 1949. The B-36 had flown for the first time nine days earlier.
The XB-19 Compared to the B-29 and the B-36
So let’s compare the XB-19 with the B-29 and the B-36. At just over 132 feet in length, the XB-19 was 33 feet longer than the B-29 and 30 feet shorter than the B-36. At nearly 43 feet tall, the XB-19 was 15 feet taller than the B-29 but only four feet shorter than the B-36. The XB-19’s wingspan was 212 feet, which was 71 feet longer than that of the B-29 and only 18 feet shorter than that of the B-36. The XB-19’s wing area was 4,492 square feet- about 2,756 square feet more than that of the B-29 and only about 300 square feet less than that of the B-36
The XB-19 weighed in (empty at 86,000 pounds, which was 11,500 pounds more than the B-29 and roughly half the weight of the B-36. The XB-19’s loaded weight was 39,000 pounds greater than that of the B-29 but only a quarter of what the B-36 weighed loaded. Range was only 350 miles longer than the B-29 and 300 miles less than the B-36. The XB-19’s service ceiling was 8,000 feet higher than that of the B-29 and 4,000 feet lower than that of the B-36. Of course the XB-19 was unable to reach the speeds both the B-29 and the B-36 were capable of. But in sheer size it didn’t give up much to the B-36.
XB-19 Trivia
In 1939, even before the XB-19 flew, it was estimated that the big bomber could also transport up to 215 fully-equipped soldiers.
By the time if flew for the first time the formerly Top Secret bomber was so popular that President Franklin D Roosevelt sent Donald Douglas a congratulatory telegram after the XB-19 made its maiden flight.
Although its massive size should have earned the XB-19 all manner of nicknames, there was never an official name given to the aircraft. It was referred to as a “flying laboratory” often. Behemoth seems to be the popular after-the-fact nickname.
Thanks to AIRBOYD.
The Douglas Aircraft Company actually lost money on the XB-19. The Army only paid Douglas $1,400,064 for the aircraft, but Douglas spent nearly $4,000,000 on the project.
After the initial flight of the XB-19, it became clear that there was some delay between control inputs and responses. Test pilot USAAC Major Stanley M Umstead said of the controllability of the big aircraft, “You soon learned how to get out of a difficult situation, before you get there.”
The XB-19 had a special compartment in the fuselage above the bomb bay with eight seats, six bunks, and a full galley intended for the relief crew (a couple of inflight mechanics and up to six relievers) and for the regular crew to prepare meals in flight during the bomber’s (projected) 24-hour missions.
The XB-19 had passages built into the lower wings which gave the those inflight mechanics direct access to the engines and accessories/engine driven systems- while the massive bomber was aloft.
Thanks to AIRBOYD.
Although the XB-19A was scrapped in 1949, its nose section inexplicably showed up in a scrap yard on Alameda Street in Los Angeles, where it remained visible until as late as 1955.
In early 1949 the U.S. Air Force had plans to save the B-19 for eventual display, but at the time the Air Force had no program to save historic aircraft and the Air Force Museum had not yet been built. But although the aircraft was scrapped, two of its enormous eight-foot tall main landing gear tires were saved. One was put on display at the Hill Aerospace Museum at Hill Air Force Base. The other has been on display at the National Museum of the United States Air Force for many years.
