XB-35 Flying Wing
The origin of the B-35 may be traced as far back as 1923, when John K. Northrop, then an engineer with the Douglas Aircraft Company, became interested in the possibilities of a "flying wing" design. However, more than a decade would pass before the young engineer's efforts showed tangible results. In August 1939, John Northrop became President and Chief Engineer of Northrop Aircraft, Incorporated, a totally independent concern primarily interested in the manufacture of military aircraft. Less than a year later, the N-1M, as Northrop called his initial "flying wing" took to the air (The N-1M's first flight occurred on 3 July 1940. In 1945, following completion of its test program, Northrop sent the airplane to the Army Air Forces for display in the Wright Patterson Museum, Dayton, Ohio. The Air Force eventually transferred the N-1M to the Smithsonian Institution, which stored it at Silver Hill, Maryland.). It was the world's first pure all wing airplane, and high ranking officials of the Army Air Corps were soon impressed by the flight characteristics of the spectacular research vehicle. The Army Air Forces (established in June 1941) applied the designation XB-35 to the N IM's military variant, which was subsequently ordered.
On 27 May 1941, the Army Air Forces (AAF) asked Northrop to provide studies of the flying wing as it related to requirements for a bomber with a range of 8,000 miles, a minimum cruising speed of 250 miles per hour, a service ceiling of 40,000 feet, and a bombload of 10,000 pounds. Such characteristics were far less demanding than the preliminary ones of April 1941, which led to production of the Convair B-36. The revised characteristics of August 1941, slightly more ambitious than the May characteristics, were again submitted to Northrop and other potential manufacturers of conventional, long range bombers. Contrary to expectations, by year's end only 2 models were contemplated for production before the Boeing B-29: the Northrop XB-35 and the Convair XB-36. The first was extremely unconventional, aerodynamically; the second was unconventional, but strictly from the weight, propulsion, and size standpoint. Although the AAF deplored the lack of choice offered by its experimental heavy bombardment program, several years would go by before comparable bombers would appear on the drawing boards.
The Northrop proposal submitted to the AAF in September 1941 was immediately followed by contractual negotiations. In a departure from standard practices, the initial procurement of the flying wing was preceded by a purchase order for engineering data, model tests, and evaluation of reports on the N-1M that had been flight tested since June 1940. Also included was the purchase of the first N-9M, a 1/3 scale flying mockup of the future B-35. The entire order, approved by Secretary of War Henry L. Stimson on 3 October 1941, was covered by Contract W535-ac-21341 which was signed on the 30th. Available records did not reveal the cost of Contract W535-ac-21341, an oversight which by the end of the costly flying wing program proved immaterial.
Procurement of the first full scale flying wing, endorsed by Maj. Gen. Henry H. Arnold, Chief of the AAF, on 9 September 1941, came under Contract W535-ac-21920 on 22 November. At the contractor's request, the contract, estimated at $2.9 million, was of the cost plus fixed fee type because, as pointed out by Northrop Incorporated, development of the XB-35 was a large project, involving funds in excess of those available to the company for experimental purposes. In addition, Northrop anticipated that materiel and labor costs would rise significantly before November 1943, when the XB-35 was scheduled for delivery. Besides providing for the first XB-35, Contract W535-ac-21920 included 1 XB-35 mockup, engineering data, plus an option clause covering the purchase of 1 additional XB-35. This option was exercised on 2 January 1942. Northrop quoted a delivery date of April 1944 for the second XB-35, also known as the back up article. Estimated extra costs were set at $1.5 million.
Another cost plus fixed fee contract (W535-ac-33920) was approved on 17 December 1942. It called for the construction and testing of 13 service test models of the XB-35, designated YB-35s. Counting spare parts and the contractor's fee, the contract's cost was expected to reach $22.7 million. The AAF's approval of this YB-35 prototype contract followed by a few months the purchase of 2 additional N-9Ms, a fourth and last N-9M being ordered in mid 1943. Retained records did not itemize the costs of the additional N-9Ms. However, such costs were included in the XB-35 program's total amount.
The huge XB-35's most noticeable features were its size and shape. Otherwise, the 4 engine aircraft was not so unusual. Its cantilever wings of aluminum alloy were constructed in 1 piece, straight tapered, and swept back. On the other hand, the XB-35 also featured some distinctive internal characteristics. It offered 8 spacious bomb bays, and the crew compartment and various systems bays were fully pressurized. In addition, the future B-35 would provide 6 beds and a small galley to allow 6 of the aircraft's 15 crewmen to rest during long missions.
The XB-35's first flight took place on 27 December 1942. As a military variant of the N-1M, the N-9M was similarly built and consisted primarily of a welded steel tube center section and an external covering of wood. As a research model of the XB-35, the 60 foot wing span N-9M closely resembled the future full size "flying wing." Two Menasco C654 engines aboard the N-9M, instead of the 4 Pratt & Whitney R-4360s earmarked for the XB-35, were the main difference between the 7,100 pound scaled down model and the experimental bomber, originally planned. Actually, the N-9M was expected to allow Northrop to more accurately predict the flight characteristics of the upcoming XB-35, a purpose which presumably would also save money and time. Nevertheless, the N-9M's first flight on 27 December 1942 was about 3 months behind schedule. Nearly all of the N-9M's ensuing flight tests were shortened by mechanical failures of one kind or another, most of them involving the Menasco engines that also equipped the next 2-N-9s.
The initial N-9M crashed on its 45th flight, killing its Northrop test pilot. The crash on 19 May 1943, after the model had only accumulated some 22 hours of flying time, was closely followed by the second N-9M's first flight. During the maiden flight of the second model, on 24 June 1943, the small aircraft's cockpit canopy was lost shortly after takeoff, but a successful landing was made (Slightly different N-9M's were still being tested late in 1945, even though a total of 150 flights had been accomplished. Flights of the remaining models averaged considerably less than 1 hour each. This time limit was shared by the N-9MB, the fourth N-9, bought to replace the lost N-9M and powered by 2 Franklin 0-540-5 air cooled engines.). Meanwhile, other difficulties had begun to compound the AAF's many problems.
The multitude of requirements generated by World War II complicated from the start the Army Air Forces' many tasks. While all sorts of weapons were urgently needed, shortages of material and manpower resources could not be immediately resolved. National priorities, regardless of their careful selection, hampered the timely progression of some aircraft programs and nearly stopped the development of crucial experimental projects. Two cases in point were the Convair B-36 and the Northrop B-35, the latter presenting the AAF with a peculiar situation. Northrop, located in Hawthorne, California, while sharing the industry's shortage of engineers, also lacked adequate production facilities. The Materiel Command's efforts to borrow engineers from other West Coast manufacturers to assist the young corporation had been totally unsuccessful, and the possibility of enlarging the Hawthorne plant was non-existent.
By the end of 1942, it seemed that Northrop's problem was solved as negotiations, instigated by the AAF, were being concluded between Northrop, Incorporated, and the Glenn L. Martin Company. In short, Northrop had indicated that it would be satisfied to fabricate only the experimental and prototype B-35s. The Martin production contract for 400 B-33s had been canceled on 25 November (By that time, Martin knew that a production contract for 200 B-35s was forthcoming. Furthermore, the company had many other commitments. In fact, it had to refuse to make a study of the long range, heavy bombardment airplane, as suggested by the AAF in October 1942.), and this actually meant that the B-35 could be produced, in lieu of the deficient B-33, at Martin's spacious Baltimore plant in Maryland. This change would also allow Northrop and the AAF to benefit from Martin's engineering talent and experience in the design of large, long range transport airplanes. But this optimistic outlook was to prove deceptive.
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