Jack Northrop’s Flying Wings
An old idea for which the best years may still lay ahead.
Jack Northrop dreamt of aircraft where everything not absolutely essential for flight was eliminated. Leonardo da Vinci’s theoretical flying machines from the 15th century, Sir George Cayley’s Governable Parachute of 1852, the Wright Brothers’ Flyer of 1903 and virtually every other flying machine all have one thing in common: they all have tails of one sort of another which are used to stabilize and control their flight. Northrop, contrarily, didn’t believe a tail was necessary. In fact, he believed anything other than the wing actively worked against the elusive goal of all aircraft designers: to find the most efficient means of getting an aircraft aloft and then keeping it there.
Pioneering aeronautical engineer Jack Northrop did not invent the flying wing. Furthermore, it’s difficult to determine who should get the credit for the idea given its ubiquity in nature. However, the work of self-taught German aeronautical engineer Alexander Lippisch is a worthy place to start. Lippisch had been inspired by the Wright Brothers’ demonstration flights at the Tempelhof Field, in Berlin, in September of 1909. World War I intervened and it would be 1921 before Lippisch, in collaboration with Gottlob Espenlaub, would build the E-2 glider. What’s remarkable is that elements of Northrop’s future designs can be found in the seminal E-2. In addition to the absence of a tail, of course, Lippisch’s design also had a ‘swept’ wing — where the wing angles back from centre to tip — and large control surfaces located at the trailing edges of the wing tips. These were designed to meet the demanding control requirements of the inherently unstable design.
Lippisch’s work inspired that of Walter and Reimar Horten of Baden-Baden, Germany. The 1919 Treaty of Versailles, after World War I, had provisions to prevent Germany from rebuilding its military. These specifically precluded the development of powered aircraft. In what can only be described as an exploitation of a loophole in the treaty, the Horten brothers — also self-taught — developed a series of gliders which built on Lippisch’s concepts. Starting with their initial flights in 1933, the Hortens progressively stretched the wings in a series of designs based on the understanding that the longer and narrower the wing, the more efficient it is — the more lift it produces for a given amount of drag. They also incorporated a small streamlined ‘pod’ just large enough for a pilot who was nonetheless asked to lie prone so as to make the frontal area of the enclosure as small as possible. The Horten glider designs began to prove out the strengths of flying wings: by eliminating the structure of a tail and most of the fuselage they were able to dramatically reduce the sworn enemies of efficiency: the aerodynamic drag and weight of needless structure. The Hortens’ designs simply slipped through the air more easily and weighed less than conventional configurations, a fact borne out on the slopes of the Wasserkuppe in the period leading up to World War II.
Unfortunately, the Hortens were active in the Nazi’s war effort. They joined the Hitler Youth when given the opportunity, became members of the Nazi party and eventually flew as pilots for the Luftwaffe. That history notwithstanding, their primary aeronautical engineering achievement during the war was the Ho 229. Their new design was the Hortens’ response to the Luftwaffe’s requirement for an aircraft capable of carrying 1,000 kilograms of bombs to a target 1,000 kilometres distant at a speed of 1,000 kilometres per hour. While no period design ever met the so-called 3x1000 dictate, the Hortens’ aircraft came closest and first flew in 1944. The Ho 229 was certainly unlike any other contender in the design competition. It incorporated all of the flying wing elements of the Horten’s highly efficient gliders. In addition, the Hortens added the groundbreaking innovation of twin jet engines embedded almost invisibly into the wings. Scarcity of materials also meant that major assemblies of the Ho 229 had to be made of wood.
While it is the subject of debate whether they realized it at the time, the incidental use of non-metallic construction materials coupled with its small cross section and the absence of vertical surfaces inherent to flying wings, the Ho 229 would have had another interesting capability. It would have been significantly less visible on radar, the newly-invented system deployed in the air defence of the United Kingdom during World War II. While the Ho 229 prototypes were successfully flown, proving the Hortens had mastered at least the basics of flying wing stability and control, it thankfully arrived too late to be of any use prosecuting and possibly prolonging the war. The sole surviving prototype of the Ho 229 was captured by the US Army as it advanced into Germany. The intriguing aircraft was brought back to the United States for further detailed study.
Jack Northrop was born in 1895 in Newark, New Jersey. Shortly thereafter, his family moved west to California and in 1916, at the tender age of just 21 and without the benefit of any formal training, Northrop took his first job in aviation — he started as a draftsman for the Santa Barbara-based Loughead Aircraft Manufacturing Company. In 1923 he moved over to a competitor, Douglas, where he worked on their World Cruiser aircraft which became the first to circumnavigate the globe. The itinerant Northrop subsequently returned to his former employer, now renamed simply Lockheed, and worked on their Vega design favoured by aviation pioneers such as Emelia Earhart and Wiley Post on their record-breaking distance and altitude flights. The through line for Jack Northrop’s early work always came back to one thing: efficiency — making the most of the least.
There was an entrepreneurial aspect to Northrop’s nature not easily accommodated at Lockeed, Douglas or any other company for which he was not a founder. In 1929 Northrop left Lockheed to form Avion Corporation and to work on his first generation of flying wing designs, the X-216H. What’s odd is that it wasn’t actually a flying wing at all, at least in terms of its outward appearance. It had a fairly conventional tail mounted aft of the main wing at the end of two spindly booms. At the end of each boom there was a vertical control surface and, in turn, a horizontal surface running between them. Despite this obvious incongruence, there were a number of innovations which were important stepping stones to the fully realized flying wings still only in Northrop’s imagination. First, the wing utilized ‘multicellular’ construction—a matrix of box-like, sheet aluminum ‘cells’ to make up the inner structure of the wing. These were then directly riveted to the wing’s skin to make the latter an integral part of the load bearing structure. It enabled a smooth wing surface of precise dimensions without the aid of any external bracing or struts and without the need for heavy internal structure either. Second, Northrop blended the powerplant and pilot’s cockpit into the wing rather than enclosing them in separate, external structures. It wasn’t a flying wing in the formal sense, but if an observer squinted a little and held a hand up to cover its tail, they would have seen distinct elements of the true flying wings which were just over the horizon for Northrop.
Jack Northrop’s genius and creativity didn’t seem to extend to the commercial aspects of his business, at least not initially and perhaps not ever. A year after Avion Corporation was founded, Northrop was forced to sell it under duress into the emerging aviation conglomerate United Aircraft and Transport Corporation. A couple of years later Jack Northrop founded the first company bearing his name which was fairly quickly sold to Douglas after producing a number of successful designs. Despite his zero-for-two record for startups, Northrop still couldn’t shake the entrepreneurial habit and, in 1939, founded the second iteration of the Northrop Corporation. That company, in an evolved form as Northrop Grumman, still exists today.
Under the auspices of his new startup, Jack Northrop quickly identified his next opportunity to further his flying wing ambitions. The US Army Air Corps (the forerunner of today’s US Air Force) was looking for a new fighter as it geared up for the looming conflict in Europe and beyond. Northrop proposed the XP-56 Black Bullet. It was a measured but still significant step from the X-216H of the 1920s. Any semblance of a tail was now gone, replaced by a small vertical surface integrated with a central pod. This also enclosed the pilot and powerplant which turned contra-rotating propellers in a pusher configuration. Northrop bent the tips of the XP-56’s wings downwards making it look distinctly bird-like from some angles. While they weren’t the fully vertical surfaces of conventional aircraft, the drooped tips had a vertical component which would have contributed to the aircraft’s stability. Significantly, though, that theoretical observer of Northrop’s earlier design would no longer have to squint and use their imagination. The XP-56 was the real thing — a true, tailless flying wing.
It was not a success. Two prototypes were built, one of which crashed and seriously injured the test pilot. But the design did fly, if only to further reveal the principal bête noire of flying wing designs — stability, or rather the lack of it, on all three axes of motion. They were simply very difficult to fly particularly given this was the era before any sort of technological assistance for the pilot. What was felt and seen from the cockpit had to be translated into responsive motions by the hands and feet of the crew. Flying wings placed almost impossible demands on even the most skilled human pilot.
Meanwhile, this would have been the period where the Hortens in Germany and Northrop in the United States would have been working on the development of flying wings at the same time. There is not much, if any, evidence of direct contact between the two camps and certainly no evidence of active collaboration. Northrop was aware of the work of the Hortens, however, even if he was dismissive of them as ‘just glider designers’ as he was reported to have said. Given the similarities in outcomes for the Horten and Northrop work, however, it’s difficult to believe they didn’t influence each other at least to some degree.
As part of the XP-56 development program and in particular to help with the chronic issues of stability and control, Northrop designed and built a lighter and less complex flying wing: the N-1M. With its resplendent yellow paint, the new aircraft began to resemble the ultimate configuration of Northrop’s future flying wings. The N-1M’s wings were both tapered and swept back from root to tip. Those tips were drooped downwards, similar to the XP-56. The twin piston engines were buried somewhere inside the wing with little external evidence of their presence. The propellers were again pointed aft and pushed rather than pulled the wing along its flightpath. The pilot peaked out of a tiny bubble just aft of the leading edge of the wing at its centre. Any semblance of a pod was gone. With the N-1M, Jack Northrop’s original idea, a simple wing abstracted from any other structure, was slowly becoming a reality. The N-1M flew quite well, doing so for the first time in 1941.
This same plane was also responsible for a number of incremental innovations of its own. The split aileron, in particular, was a clever means of addressing the flying wing’s absence of vertical control surfaces. Ailerons, located at the outboard trailing edge of a typical aircraft wing, move in opposition to each other to roll the aircraft around its fore-and-aft axis. Northrop configured the ailerons on the N-1M so they consisted of separate upper and lower surfaces. When the pilot want to roll the aircraft, the two surfaces on a given wing would move together like a conventional aileron. When the pilot wanted to yaw the aircraft — that is, rotate it on its vertical axis — the two surfaces of a given aileron could be moved in opposite directions, one surface up and and one down like a clamshell. This resulted in that wing being ‘dragged’ back as if the pilot were steering it with a conventional rudder. Northrop had seemingly solved the fundamental problem of providing the control of a rudder when, in fact, there was none. There was also a handy additional side benefit — if the ailerons were clamshelled open on both wings simultaneously, they were an effective air brake. This was useful for rapidly slowing down the slippery wing during critical phases of flight such as landing.
Given the significant lead time in developing any new aircraft, it may be surprising to learn that Northrop was contacted as early as 1941 to design a replacement for strategic bombers either in production or in the latter stages of the development process. The US Army Air Corps was already beginning to think past the cigar tube shaped B-29 which would be in service through the end of World War II in 1945 and significantly beyond. The new bomber development program would eventually lead to Northrop’s XB-35 design. It was an aircraft which must have begun to reflect Jack Northrop’s limitless ambition for the flying wing. It had a wing span of 172 feet and was propelled by four Pratt & Whitney Wasp piston engines with a combined total of 12,000 horsepower. Each engine swung contra-rotating props similar to those found in the XP-56. The massive aircraft first flew in 1946 which was too late for World War II, but just in time for the Cold War which started soon after. The requirements were the same, just the targets were different. Based on it’s promising performance projections, the US Army Air Force had already ordered 13 pre-production aircraft which were designated as YB-35s. Northrop was lead to believe he was well along the way to a prospective order of 200 production aircraft.
As part of the XB-35 development program, Northrop designed and built a smaller scale prototype which would enable further exploration of technical issues which would undoubtedly arise as work on the full scale aircraft progressed. The new, scaled down aircraft was designated the N-9M. While superficially resembling the earlier N-1M, it actually mimicked the dimensions of the XB-35 albeit with just a 60 foot wingspan. A total of four examples were built and flown including an example still flying today.
The piston-engine powerplants in the YB-35s proved troublesome and were also considered generally less desirable than the jet engines which were becoming more common and more reliable in the late 1940s. The Jet Age had truly arrived. Even before the YB-35 program was completed, the aircraft were being re-engineered to accept Allison J35 jet engines and the aircraft were subsequently re-designated YB-49s. With the contra-rotating propellers removed and replaced with relatively small inlets and outlets for the jet powerplants, it was in this configuration when the aircraft must have finally appeared the way Jack Northrop had originally visualized back as early as the 1920s. It even contained a family likeness to the Horten’s pre-war gliders and their wartime Ho 229. The flying wing family tree finally seemed to be converging to usher in the future of aviation.
Then, in 1949, just as Jack Northrop’s lifelong dream appeared to be coming to fruition, the entire US Air Force flying wing development program was abruptly cancelled and all existing aircraft quickly scrapped.
While there are a number of theories, conspiracy theorists seem to favour one in particular. The Secretary of the Air Force at the time, Stuart Symington, was assigned the task of rationalizing excess post-war aircraft production capacity. While Northrop’s B-35 and B-49 programs were in development, a competing design from Convair, the B-36 Peacemaker, was also undergoing development. Symington didn’t feel there was room for both aircraft in future military procurements. Furthermore, he believed the two companies should merge and presumably produce one aircraft or the other but not both. There were even rumours at the time that Symington wanted to lead the merged company once the deal was done. When Jack Northrop resisted, feeling the terms of the merger were unfair, Symington unilaterally cancelled Northrop’s planes in favour of the much more conventional Peacemaker. At the time, it was justified as a response to budget, schedule and technical problems with Northrop’s design. Jack Northrop remained largely silent on the matter other than to testify before Congress that no such coercion by Symington had occurred. Somewhat mysteriously, though, Northrop severed virtually all connections with his eponymous company just three years later, in 1952, and took early retirement.
Presumably to keep the peace with his former company’s single most important customer, Jack Northrop maintained his silence on the cancellation of the flying wing for over 30 years. Then, in 1979, in a television interview with Clete Roberts of KCET in Los Angeles, an ailing Jack Northrop confirmed that he had, in fact, resisted Symington’s will to merge Northrop and Convair, and there had been active coercion. Symington, perhaps seeing his own career dreams going up in smoke as a result of Northop’s obstinacy over the merger, was quoted by Northrop as saying “you’ll be goddamned sorry if you don’t.” Within a few weeks of that meeting, Northrop’s flying wing dreams were seemingly over.
At the time of its cancellation, the Northrop flying wing had encountered schedule and budget overruns. There had been technical problems with the program, including the tragic loss of one prototype and its entire crew in a crash possibly related to fundamental lack of stability in the design. But these things were, candidly, nothing out of the ordinary for the development of such a complex aircraft which incorporated so many new ideas. In the end, however, it is at least plausible the cancellation of the US Air Force’s flying wing program came down to an act of petulant, irrational spite.
On November 22nd, 1988 it was a brilliant, sunny fall day outside the prosaically named United States Air Force Plant 42 in Palmdale, California. In front of the carefully vetted crowd sat an aircraft the likes of which nobody had ever seen. There had been rumours of its existence, sure, as well as whispered stories of front companies to acquire parts and covert acquisitions of real estate. There were other measures like the absence of military uniforms so as to disguise the true nature of a rebuilt, non-descript Ford car plant in Pico Rivera, California. This was where the subassemblies of the top secret aircraft would be built. But on that day in Palmdale, the secret would finally — if not incrementally — be revealed. The public was witnessing the rollout of the B-2 Spirit strategic bomber. With its black-on-black radar absorbing outer skin it looked more like something out of the latest Star Wars movie than anything from the US Air Force. But most noticeable of all was the absence of any sort of tail or vertical control surfaces. This was ostensibly to further reduce radar reflections and rendered the B-2 all but invisible to detection. But for all practical purposes, it was the embodiment of the pure flying wing Jack Northrop had visualized from the start.
Technology had finally caught up with Jack Northrop’s dreams. In particular, the Spirit featured fly-by-wire controls. This system, commonplace in virtually every modern aircraft today, is where there is no direct mechanical connection with the pilot’s cockpit controls and the control surfaces of the aircraft. Rather, both are connected to a computer which is further wired up to detect the behaviour and attitude of the aircraft in flight. Through software — millions of lines of computer code — the control inputs of the pilots are automatically converted into the correct movements of the control surfaces to produce the desired reaction of the aircraft. The computer, based on what’s happening to the aircraft in three dimensional space in real time, can also add its own control movements to stabilize the aircraft in the attitude desired by its crew. The net result is that the B-2, which would simply be impossible to fly without this kind of assistance, can be made to feel like a much more conventional aircraft to which conventional flying skills can be applied.
There are also distinct echoes of Jack Northrop’s earlier designs in the B-2. The split ailerons of the N-1M are there albeit the pilots never have to think about them too much. They simply push the rudder pedals with their feet and move the control stick with their hands. The flight control computer will determine whether the aileron’s two surfaces should move up and down together to roll the aircraft or split apart to provide a rudder-like control. Also seemingly too much of a co-incidence are some of the dimensions of the B-2: the wing span is exactly 172 feet — precisely the same as Northrop’s YB-49 from nearly four decades before. The B-2 is scheduled to remain in service until 2032 when it is to be replaced with the B-21 Raider which bears a striking family resemblance to the Spirit.
Jack Northrop passed away in February of 1981 at the age of 85. Shortly before he died, he was given a security clearance to see a small model of the B-2 which was still years away from its first flight or even that rollout ceremony in Palmdale. However, it would have been crystal clear that much of the DNA of the B-2 was directly contributed by Jack Northrop. Rendered speechless by illness, Northrop was said to have written on a piece of paper “now I know why God has kept me alive for 25 years.”
A beneficial side effect of programs like the B-2 is that the core of the fly-by-wire technology — the ability to sense absolute position in three dimensional space and provide computed, reactive, controlling responses — is now ubiquitous in everything from smartphones to drones to surface vehicles and virtually everything in between. Fully integrated modules with these capabilities weigh no more than a few grams and cost no more than a few dollars thus opening up these capabilities to a whole new generation of flying wing experimenters.
A good example would be the recent announcement of the first flight of the Horten HX-2 light aircraft from the German company of the same name. That name, obviously, is an homage to the Horten brothers to whom the present day proponents of flying wings owe a significant debt. The HX-2 is almost what Jack Northrop had visualized in terms of general configuration. The only concession to the age old problem of stability are the small winglets extending upwards at the tips of the wings. The new aircraft seats two in a small pod which also encloses the powerplant with its aft-facing pusher propeller. What’s tantalizing, though, is the prospect of the inherent efficiency of flying wings being an important enabler for the use of new propulsion technologies — such as electric power — which may become available in the future.
Jack Northrop would be pleased to know the flying wing, his lifelong passion, may be more relevant than ever.
©2019 Terence C. Gannon
Thank you so much for reading. You can also listen to this essay as an episode of the Not There Yet podcast, read by the author.
