The flying wing bombers enjoyed all the usual financial support and governmental interest normally associated with a wartime program. They also suffered through the chaotic period that came with war's end. The program endured, however, because of the enormous potential demonstrated by the unique aircraft. The enthusiasm for the program that was demonstrated by the Northrop "family" was shared to a great extent by many of the technical and management people of the Army Air Forces. Their foresight, assistance, and encouragement kept the development program going through the rough times.

Project MX-140, as the bomber program was called, was officially initiated by contract action on November 22, 1941, following previous discussions between Northrop and Air Force officials regarding performance requirements for a high altitude, long range, heavy bombardment airplane. The numbers that spelled out the airplane's vital statistics in formal Airplane Specifications NS-9A gave no hint of the sheer expansiveness of the airplane, and its spectacular performance. They also gave no hint of the problems that would attend its design, construction, and flight evaluation.

In size, the XB-35 would dwarf the B-17 Flying Fortress, with wing area and gross weight almost three times those of the legendary heavy bomber. The unconventional control system reflected years of study, wind tunnel tests, and flight test data gleaned from the N-1M and N-9M programs. The elevons and rudders were power operated. Thus, it was necessary to provide an artificial "feel" to the controls for these surfaces. This was accomplished by springs attached to the control wheels and rudder pedal mechanisms which returned the controls to neutral and provided the "feel" necessary to prevent over-control of the rudder and aileron movement of the elevons. "Feel" to the operation of the control columns for elevator control was provided by ram air pressure in a bellows attached to the control columns.

Trim flaps, elevons, and landing flaps were arrayed in order from each wing tip inboard along the trailing edge of the wing. The electrically actuated trim flaps at the wing tips were used by the pilot in much the same manner as elevator or aileron tabs. Their primary purpose was to balance the large diving moments produced by the split trailing edge landing flaps, minimizing the upward deflection of the elevons and thus permitting them to be deflected over a greater range as elevators. The trim flaps could also be operate differentially to counteract unbalanced rolling moments.

Rudders consisted of split flaps that were incorporated as an integral part of the trim flaps at the trailing edges of the wing tips. Operated one at a time by the pilot's movement of the corresponding rudder pedal, the surfaces deflected above and below the trim flap. Simultaneous movement of the rudder pedals, which were not interconnected, opened both rudders for speed control. Despite the unconventional arrangement and function of the control surface, the conventional control column with wheel and rudder pedals made the pilot feel right at home.

Contributing to increased longitudinal stability at high angles of attack were wing tip slots with automatically controlled cover doors. These doors were set to open at high lift coefficients, preventing wing tip stall and increasing stability. A switch actuated by the landing gear also opened the doors when the gear was down.

One of the primary concerns in the layout of the aircraft was the cockpit design. Despite unorthodox configuration, space was not a problem. The aircraft's cockpit featured convenient control and instrument arrangements and excellent visibility.

Conventional instruments and control switches are arranged in a slightly unconventional manner in the XB-35 cockpit. Flight instruments are arrayed on the vertical panel between the pilot stations; radio equipment and prop controls are located on the pedestal separating the pilot stations. One set of throttle controls is suspended from the top of the cabin between the pilot and co-pilot, another is mounted in a quadrant at the engineers table further aft, along with the mixture controls.

The pilot seated in the plexiglass bubble to the left of the aircraft centreline. The co-pilot was to the right of and below the pilot, behind a large window in the leading edge of the wing. An engineer's station was also in the forward part of the crew nacelle, as were stations for the radio operator, navigator, bombardier, and gunners. The mid-section of the crew nacelle had sleeping facilities for a relief crew of six people, a requirement for operational missions of 10,000 miles where crew fatigue would be a primary consideration. The after section contained the gunner's station. The seven-foot headroom in the crew's quarters was certainly adequate, and the accommodations were the first of such extent and complexity to have been incorporated into such a radical design.

A brief look at the overall arrangement would not be complete without at least some reference to the "main battery" of the XB-35-its eight bomb bays. Capable of carrying 10,000 pounds of conventional bombs (but not an atomic weapon), the bays were incorporated in the wings, arrayed four on each side of the crew nacelle.' Defensive armament consisted of twenty 0.50 calibre machine guns contained in seven remotely controlled turrets: four on the wing, two on the crew nacelle, and a tail stinger.

This striking photograph, staged though it may be, dramatically shows the XB-35's  "Achilles' heel" -the eight four-bladed, contra-rotating propellers. Constant troubles with government furnished gearboxes severely restricted the further development of the XB-35 flying wing

The power plants were also vital to the successful operation of this revolutionary weapons system. They consisted of four Pratt & Whitney Wasp Major engines, one pair each of R-4360-17 and R-4360-21 series equipped with single stage GE turbo-superchargers, each delivering 3000 hp. The "Achilles' heel" of the installation was the propulsion power train. Each engine was coupled to a remote gear box assembly by an extension drive shaft. Two sets of four-bladed, dual rotating, reversible pitch, full feathering, Hamilton Standard propellers were mounted on dual concentric shafts extending from each gear box. The engines were completely enclosed within the wing, an arrangement that imposed severe requirements on the aircraft's structure. Superchargers, intercoolers, oil coolers, and fans for ground-cooling and cooling at low speeds were located in the wing, as were cooling ducts and controls to diffuse the air around the engines and expel it through flaps near the trailing edge.

Basic design similarities between N-9M and XB-35 are evident in this photograph of the XB-35, under tow prior to taxi tests at Northrop in May 1946. Split-flap rudders attached to the pitch trimmers, elevons and landing flaps are along the trailing edge; automatic wing slot is visible just aft of the leading edge on the left side.

Translating 100 pages of statistics and technical terms into 100 tons of complex, futuristic airplane proved to be an almost insurmountable task. From contract approval in November 1941, to first flight of the XB-35 on June 25, 1946, there were interminable delays. At one time or another, changes in priorities, design and engineering difficulties, problems with ground testing engines, shortages of engineers, indecision by management, constant shortages of government furnished equipment (GFE), and a myriad of other factors contributed to the lengthy production process. Of all the obstacles to orderly progress, the most frustrating involved the highly unsatisfactory working relationship between two major aircraft builders, Northrop and Martin.

Following an initial contract for one XB-35 airplane, approved November 22, 1941, Northrop received an order for an additional XB-35 as a backup in January 1942. Later that year, another 13 service test models were contracted for, to be designated YB-35. By June 1943, with a production contract for 200 B-35s on hand, and the first flight date still out of sight, it was apparent that Northrop production and engineering facilities, already heavily committed to production of P-61 Black Widow night fighters, were inadequate for the job. If the program was to proceed, engineering and production assistance would have to come from some other source.

By the end of June 1943, the Glenn L. Martin Company of Baltimore, Maryland, at the AAF's request, had contracted to assist Northrop in engineering the XB-35 and YB-35 and also to manufacture 200 production B-35s. Delivery of the first production airplane was to be in June 1945. From a tactical and logistical standpoint, there was no further need for Martin's B-33 Super Marauder. The production contract was cancelled and the available engineering talent was diverted to the XB-35 project.

The engineering "partnership" that evolved between Northrop and Martin not only failed to produce a single B-35, but also engendered confusion, delays, and even ill will. Engineering work was carried out simultaneously at both companies on "X," "Y," and production airplanes, resulting in indecision, lack of coordination, and unresolved questions of priorities and responsibilities. Loss of engineers to the military draft aggravated an already untenable situation. As of March 1944, Martin had made no commitments to materials and had not started tooling. The program was already 18 months behind schedule and relations between Northrop and Martin were considerably strained.

In May 1944, the AAF reviewed the entire program. It was the opinion of some officials that the attitude of Martin management was a significant factor in the lack of progress to date. Never enthusiastic about producing any airplane not of their own design, Martin continually put forth more reasons for not continuing their part of the production program. Martin management expressed little faith in the B-35 as a practical airplane. The AAF decided to cancel Martin's production contract, with the understanding that Martin would continue to give Northrop engineering assistance on the "X" and "Y" models. Additional engineering assistance would be made available from the Otis Elevator Company. No production engineering was to be undertaken at that time. In effect, it was a conscious decision that the B-35 would be a post-war airplane.

December 1944, marked a significant turning point in the development of the Flying Wing bomber. By that time, both Germany and England were using turbojet-powered aircraft in combat. The Messerschmitt Me 262 first appeared on combat in July 1944, followed shortly by the first victory of the British Gloster Meteor over a German V-1 missile. In the United States, the Bell XP-59A Airacomet had flown in 1942, and by late 1944 the Lockheed P-80A Shooting Star was almost operational. It was becoming obvious that the world was on the threshold of the jet age and piston engined warplanes such as the B-35 would eventually become obsolete. On the other hand, a B-35 fitted with turbojet engines began to look extremely attractive.

Consequently, in December 1944, series of modification and conversion programs began that lasted until the final days of the Flying Wing bomber. Proposals for changes in the aircraft mission, combined with alternative power plant arrangements led to a bewildering variety of aircraft configurations and designations. After years of conversion and modification programs that ensued, only six were completed and flew, three of which had piston engines, and three with turbojets.

It was another year and a half after the modification proposals in December 1944, before an XB-35 would finally take to the air on its maiden flight. It was a frustrating period marked by engine development problems, delays due to lack of experience in construction of very large aircraft, late deliveries of major GFE items, and the acute conversion problems experienced by the defence contractors with the end of World War II.

The majestic XB-35 (42-13603) moved for the first time on its own wheels and under its own power on May 16, 1946. The occasion was a slow taxi test, and at the controls was the Northrop test pilot who would shepherd the Flying Wings through four turbulent years of flight tests, Max Stanley.³ Accompanying Stanley as co-pilot was Fred Bretcher, who would be at his side during much of the flying program.

As the XB-35 began to move slowly down the 100-foot wide runway at Hawthorne, its 172-foot wing span seemed to dwarf even the building of the nearby Northrop plant from which it came. To Jack Northrop, standing at the flight ramp, the sound of four R-4360s running at the same time, even at taxi power setting, must have been overwhelming. As Max Stanley gave him a "thumbs up" at the conclusion of the satisfactory test, Jack Northrop surely must have been elated at this sign of progress and the prospect of a first flight in the not too distant future.

The day finally came. After dozens of high-speed taxi runs, during which speeds as high as 115 mph were attained, the aircraft seemed ready. June 25, 1946, was picked for first flight. Only a small crowd of sightseers and media people watched Max Stanley, Fred Bretcher, and Flight Engineer O.H. Douglas climb up into the flight deck, which by 10:00 am was like an oven in the hot California sun. Absent were the thousands of designers, engineers, and shop workers who had laboured for years over the engineering and construction of the bomber. They had been restricted to their desks and work stations by company executives concerned over crowd control during the momentous occasion. Absent also was the man whose creative genius had spawned the giant wing, Jack Northrop, who, abiding by company policy, also remained at his desk, in an incredible display of self discipline.

"This is it!" With those words, Max Stanley advanced the throttles and, with 12,000 hp pushing the huge wing along, the XB-35 thundered down the narrow runway at Hawthorne. At 120 mph, Stanley slowly eased the control column back and at 10:32 A.M., the Flying Wing flew for the first time. Finally, after years of planning and experimenting, Jack Northrop had accomplished what Junkers, Soldenhoff, and other early pioneers had only dreamed of.

In an historic moment Max Stanley lifts the world's largest flying wing off Northrop Field on its first flight on June 25, 1946. The uneventful flight terminated at Muroc Air Base.

The first flight was essentially a ferry flight from Northrop Airport to Muroc Army Air Base. The idea was to get to Muroc with a minimum of trouble, but at the same time to learn about the flying characteristics of the airplane. Stanley tested the controls with the landing gear up and down several times. Highest airspeed attained was 200 mph, as the Flying Wing, with its P-61 Black Widow chase plane in company, cleared the mountains and began its descent to Muroc. As a precautionary measure, a no-flap approach was made, with a smooth touchdown at 112 mph. The 44-minute flight was uneventful, except for erratic operation of a propeller governor. Everyone associated with the project was jubilant, anxious to press on with the flight testing and prove the design once and for all.

But the minor problem with the propeller governor did not fade away. The XB-35 flew twice more in the next three months, accumulating only three hours of flight time by mid-September 1946. Problems with the Hamilton Standard propeller governors became chronic, with the propellers continually "hunting" around a constant speed setting and "creeping" in fixed pitch during air operations. Additionally, there was evidence that the huge counter-rotating propellers were operating under excessive stress, leading to a restriction of 80 hours operating time due to the danger of fatigue.

Another major problem with GFE arose. Troubles centred around the gear box assembly that coupled each engine to its propeller by means of a drive shaft from engine to gear box, and a dual concentric shaft from gear box to the counter-rotating propellers. Propellers and engine vibration caused frequent failures of the gear boxes. A flexible, vibration absorbing gear box mount was a vital necessity for successful flight testing.

Regardless of developmental problems, the Flying Wing in the air was the epitome of style and grace, exhibiting an extraordinary quality that caught the fancy and imagination of the public.

At the beginning of 1947, the Flying Wing program consisted of one XB-35 flying, albeit occasionally, one XB-35 about to finish engineering inspection in March, two YB-49s (the jet engine configured B-35) and six YB-35s (built to XB-35 specifications) either complete or in the final stage of assembly. The remaining five YB-35s on the existing contract were to be equipped with more modern navigation and weapons systems, and thus were to be designated YB-35As.

The first XB-35 flew only intermittently during 1947, plagued by landing gear doors failing to retract and the continuing gear box malfunctions. The second XB-35 (42-38323) flew for the first time almost one year after the first, on June 26, 1947. It too, began to experience the same difficulties as the first aircraft. In desperation, the Air Materiel Command cancelled dual rotation propellers for the YB-35 and decided to use single rotation gear boxes and 15-foot diameter Hamilton Standard propellers, despite the resulting deterioration in performance. In April, both XB-35s were grounded for installation of the changes. Flight tests did not resume until February 1948.

The troublesome contra-rotating propellers eventually gave way to four new single-rotation propellers, shown here installed on the first XB-35. Despite the change, the piston-engined B-35 eventually became a victim of the jet age

By trading props for tailpipes and adding vertical fins, the B-35 acquired a new designation, B-49, and a new lease on life. Gross weight increased 30,000 pounds, maximum bomb load decreased from 144,800 to 32,000 pounds, and range decreased to about 4900 miles, despite the addition of fuel tanks.

Shown here is the right side bank of four J35 turbojet engines flanked by two fixed vertical fins. At the lower left is the right side landing flap in the extended position.

The eight-jet YB-49 (42-102367) was rolled out and unveiled to an admiring press at Hawthorne on Monday morning, September 29, 1947. The first taxi test was on October 20, with Max Stanley, Fred Bretcher, and O.H. Douglas at their accustomed crew stations.

Cockpit of the YB-49 (42-102367) has a cleaner look to it compared to that of the XB-35. Two overhead throttles for eight jet engines replace the four piston engine throttles; the centre pedestal is less cluttered with the absence of propeller and some radio controls

The first flight on October 21, 1947, was from Hawthorne to Muroc; the 34 minutes in the air were uneventful. Orva Douglas summed up the reaction of the crew: "With its smooth (vibration free) flying, quiet operation, and phenomenal performance, the YB-49 is a dream."

Flight testing of the YB-49 began in earnest, the aircraft flying almost as much time in the next two months as the two XB-35s had flown in 18 months. Nevertheless, problems with props and gear boxes were immediately replaced by failures of auxiliary power units that supplied current to the electrical system of the airplane, poor reliability of the J35 turbojet engines, and marginal stability that compromised the capability of the YB-49 to perform the bombing mission for which it was intended.

Highlight of the YB-49 test program was the long range test flight on April 26, 1948. The aircraft took off with a gross weight of 192,000 pounds, and flew a distance of 3528 miles at a true airspeed of 388 mph. A round robin course over the California and Arizona desert was flown. The only mishap was that a rough running engine had to be shut down two hours before landing at Muroc.

For most negative aspects of the YB-49 development program, however, spectacular demonstration of performance occasionally occurred which evoked superlatives. One such event was the highly successful long range test flight of the YB-49 on April 26, 1948. On that date, the aircraft remained aloft for 9.5 hours, of which 6.5 hours were flown at an altitude of 40,000 feet. The five-man crew for the flight consisted of Max Stanley, Fred Bretcher, and Orva Douglas, augmented by Air Force Captain Jay Wethe and Northrop flight engineer Don Swift. The record breaking flight prompted high praise from General Hoyt S. Vandenberg, Chief of Staff of the U.S. Air Force.

It was an encouraging, well-deserved accolade for the Northrop team. Coming on the heels of the first flight of the second YB-49 (42-102368), flown on January 13, 1948, by Major R.L. Cardenas, it was followed in May by the first flight of the third and last of the B-35 series, the YB-35 (42-102366). All three B-35s were now equipped with the single rotation propellers and gear boxes.

Hard on these tangible signs of progress came disaster. On June 5, 1948, after accumulating almost 57 hours of flight time, the second YB-49 crashed and was destroyed. Killed in the crash were: Major D.N. Forbes, pilot; Captain Glen W. Edwards, co-pilot; Lieutenant E. Swindell, flight engineer; Mr. C. Leser, observer; and Mr. C. LaFountain, observer.

The aircraft was on its twenty-fifth flight at the time of the accident. Recent flights had been devoted to the performance tests of the program, with Forbes as pilot and Edwards as co-pilot on all flights except #23, where Askounis acted as co-pilot in place of Edwards. Flight engineer for these flights was Lieutenant Swindell.

Major Forties and his crew had taken off from Muroc in the early morning ostensibly for a performance test flight. Routine position reports over the Antelope Valley test range were received for about an hour. The aircraft was observed to crash in the desert about 20 minutes after the last report. The major portion of the airplane landed inverted, with no apparent horizontal velocity, and much of the airplane was destroyed in the explosion and fire that followed.

Parts of the airplane, including the outer wing panels and flap and elevator parts, were found in a narrow area extending two or three miles from the wreckage. During the investigation that followed, it was impossible to arrive at an incontestable conclusion regarding the cause of the accident. A major structural failure had obviously occurred in flight. Many specific causes were considered: exceeding flight restrictions, tumbling resulting from a stall, instability due to extreme aft centre of gravity due to improper fuel usage, unintentional nose-up trim flap motion, hydraulic control system malfunction; the possibilities seemed endless. All were examined, many were discarded as impossible, some left open as possibilities.

In the final analysis, it appeared that the crash was caused by simultaneous failure of both outer wing panels from a positive loading condition. The failure could have been due to loads caused by excess normal acceleration, i.e., the airplane was overstressed during a high-G pullout. One of the most plausible explanations was that the overstress occurred during recovery from a stall or post-stall manoeuvre.

The setback in the program turned out to be temporary; the airplane's potential for a variety of roles was well recognized by the Air Force. A review of the Strategic Reconnaissance Program by the Air Force subsequently led to a formal contract in September 1948, for 30 reconnaissance versions of the B-49, designated the RB-49A. Even before the contract was signed, Northrop was instructed in June to arrange production of the airplane, except for an absolute minimum number, at the government-owned Fort Worth facility of Consolidated Vultee Aircraft Corporation (Convair). The Convair Fort Worth plant was engaged in B-36A production, to which only about 70 percent of the facility was devoted. With Northrop's production capacity of only three bombers per month at its Hawthorns facility, the shift would take advantage of Convair's unused production capacity.

The proposed subcontract was an unusual one for peacetime. It appeared to mark the emergence of the B-49 as a major factor in the strategic forces of the jet age. In reality, the days of the Flying Wing were numbered.

As B-49 testing continued and production plans took shape, the B-35 program continued to experience serious problems; doubts arose about the airplane's utility as an operational bomber, particularly in view of force level cutbacks and the inability of the Flying Wing to carry an atomic bomb. Vibration difficulties were being encountered with the single rotation propellers, engine cooling fans continued to fail from metal fatigue, and considerable maintenance problems were experienced with the intricate exhaust system of the R-4360 engines. Many configurations of the B-35 emerged, most involving some sort of conversion to turbojets. One proposal, which was well into the fabrication stage in late 1949, was the conversion of a YB-35 to a combination of turbojet and turboprop engines. Designated EB-35B, the airplane would have six turbojets: four in the wing, and two externally mounted below the wing, as well as two wing-mounted Northrop XT-37 Turbodyne engines.

The XT-37 Turbodyne was developed by the Northrop-Hendy Company, a jointly-owned subsidiary with the Joshua Hendy Iron Works. Research on the turbine that resulted in the Turbodyne dated back to 1939, when Vladimir Pavlecka, then Northrop's chief of research, interested Jack Northrop in the potential of gas turbine power plants. Funded by a joint Army-Navy contract, the turbine development continued during the war years, and the first engine was completed in 1945. It was subsequently destroyed during tests, but a second machine continued in development. By 1950 its 50-hour endurance test was completed, delivering a record-breaking 7500 hp continuously. At the time, it was the most powerful aircraft power plant in the world, capable of delivering 10,000 hp with a suitable propeller. On the EB-35B, two Turbodynes were to drive large counter-rotating pusher propellers. With the cancellation of the EB-35B in 1949, prospects for flight tests of the engine ended. In 1950, at the direction of the Secretary of the Air Force, the patents, name, and technical data were released to the General Electric Company.

In November 1948, another step was taken toward the ultimate dissolution of the B-49 project. During informal discussions about recent bombing tests of the YB-49, Major Robert L. Cardenas, Air Force test pilot on the project, was quoted in official Air Force records as saying that the airplane was "extremely unstable and very difficult to fly on a bombing mission ... because of the continual yawing and the pitching which was evident upon application of the rudders, undoubtedly due to the control arrangements or elevons peculiar to the YB-49." Until aerodynamic deficiencies could be corrected, it was the opinion of Colonel Albert Boyd, Chief, Flight Test Division at Murk, and Major Cardenas, that the YB-49 was unsuitable for both bomber and reconnaissance work^"

Subsequently, Major Cardenas stated for the record that the airplane was marginally stable, rather than "extremely unstable." On November 16, 1948, an official Air Materiel Command report on the bombing evaluation, which was conducted under manual conditions, i.e., without autopilot, reiterated the inadequacies of the YB-49 under the test conditions, but referred to the "marginal directional stability of the aircraft in fight." Installation of a satisfactory autopilot was considered a top priority.

On December 29, 1948, a Board of Senior Officers met to study the Air Force procurement program, and consider a proposed termination of the RB-49 program. The Board recommended cancellation of the 30 RB-49s.

On January 11, 1949, the Air Materiel Command directed Northrop to terminate work on all phases of the reconnaissance version except for completion and test of one YRB-49A, a six engine version equipped with special reconnaissance equipment. Conversion of certain YB-35s to jet engines continued.

 this is a rare photo of nine Northrop Flying Wing Bombers. Many people do not realize that more than one or two prototypes were built of this design. Here, for the first time, is actual proof of their existence. Two of the big wing bombers are undergoing modifications from  XB-35’s to Flying Wing B-49 1t Bombers.

The decision in February 1949, to salvage, or scrap the two XB-35s (4213603 and 42-38323) and the YB-35 (42-102366), which were the only piston-engined Flying Wings in flying status, spelled the end of that phase of the program. With only one remaining jet-powered YB-49 (42-102367) still flying, the future of the program looked bleak. In February, the YB-49 had a brief moment of triumph in an otherwise discouraging year.