Document created: 04 May 2004
Air University Review, July-August 1971

Five Pathfinders

The Origins of Air Navigation

Colonel Ray L. Bowers

Among the navigators of the U.S. Army Air Forces during the Second World War, few were military professionals. Most had come lately from the offices and schools of the nation, with only a fast training program to introduce them to what sometimes became one of the war’s most challenging tasks. The navigator’s job was seldom an exalted one. Few reached high rank; regardless of talent, a navigator never commanded the aircraft in which he flew. He often flew as part of a massed formation of bombers or troop carrier planes, with no responsibility for actually directing his own aircraft. On the other hand, those navigators who themselves led the formations knew that a misjudgment could mean the lives of hundreds of paratroops or airmen; few responsibilities could be as awesome.

The limitations of the navigator’s art became magnified in the urgency of combat. In troop carrier operations, navigating in darkness or bad weather proved so uncertain as to call into question the very efficacy of airborne assault, while the main American bomber offensives hinged on the existence of visual conditions near the target. Exemplifying the problem were the navigational mistakes on the Ploesti mission of 1 August 1943 and on the Sicily airborne assaults the same summer. In less pressing circumstances, however, wartime navigational successes were impressive:  thousands of trans­oceanic flights by the crews of the Air Transport Command, for example, foreshadowed the global nature of air power.

The idea of a specialist, professional air navigator was itself recent in the U.S. air arm. The B-17 and B-18, which entered active Air Corps service in 1937, were the first types having crew positions designed for the navigator, and until 1941 these positions were manned by Air Corps pilots certified in celestial navigation and dead reckoning after short training courses. But if the navigators themselves were new to the Air Corps, the techniques and equipment they employed were not. These elements, along with a conceptual framework for systematic air navigation, were wholly in existence by 1940, the products of two decades of determination and resourcefulness among a handful of pathfinders in the field, men to whom the challenge of invention was all-absorbing. If the demands of combat in World War II at times went beyond the state of the navigator’s art, least at fault were the “impatient young men” of the years of austerity.

During the decade following the First World War, developments in navigation within the Air Service centered around the career of Albert F. Hegenberger. Bostonian by birth, Hegenberger had left Massachusetts Institute of Technology for flying training in the wartime Air Service and had subsequently returned to MIT for studies in aeronautical engineering. After reporting to McCook Field (now part of Wright-Patterson AFB, Ohio) in 1919, Second Lieutenant Hegenberger established what subsequently became the Instrument and Navigation Branch. Here Hegenberger and his associates worked to perfect their ideas in air navigation, or avigation, turning their inventiveness toward new developments in compasses, airspeed meters, driftmeters, sextants, and maps. Limited funds for procurement yielded chronic delays and frustrations. In June 1919 Hegenberger prepared a week-long course in air navigation for the Engineering School, including ground practice in star identification and use of the sextant. After attending a special course under the Navy at Pensacola, including dead reckoning and celestial flights over the Gulf, Hegenberger returned to his work at McCook.

The June 1927 flight of Lieutenants Hegenberger and Lester J. Maitland from California to Hawaii in a Fokker trimotor reflected the advancements at McCook in long-range navigation. Hegenberger’s successful navigation resulted from accurate dead reckoning using the magnetic compass and driftmeter, supplemented by celestial observations. The newer earth induction compass failed during the flight, and the radio compasses proved unreliable. Hegenberger had made azimuth and altitude precomputations for the sun and selected stars for several points along the route. His final early-morning observations, taken amid rain and clouds, indicated that the aircraft was well north of the planned course. After some persuasion, Maitland accepted the 90-degree left turn. The correction proved sound, and the pair landed successfully at Wheeler Field. The flight of their Bird of Paradise was the first from the mainland to Hawaii. Two years earlier two Navy flying boats had attempted the crossing but had made forced landings in the Pacific. The successful flight earned for the two Air Corps pilots the Mackay Trophy for 1927.

Soon afterwards Hegenberger (who remained a lieutenant until 1932) and two other instructors opened a new navigation school for pilots at Wright Field, incorporating in the curriculum missions over the Gulf of Mexico in the Bird of Paradise. The school closed shortly, and Hegenberger’s attention turned to instruments for blind flying. The Collier Trophy in 1934 recognized his achievement in this work, made possible by his strong background both as pilot and engineer.

The navigator’s position in the Martin B-10 was an afterthought, extemporized by installing a few essentials in the rear cockpit. The position was manned most often by pilots who lacked the 1000 hours of flying time required by regulation for eligibility as B-10 pilot. With aircraft of longer range entering service, the Army Air Corps badly needed to widen its thinking on air navigation systems. Largely on Hegenberger’s urgings, the Air Corps in 1932 brought to Washington a civilian adviser in navigation, Harold Gatty, a Tasmanian of unusual qualification. Gatty had learned marine navigation at the Royal Australian Naval Academy and had had wide experience in air navigation, having navigated for Wiley Post in his round-the-world venture. At first he had trouble communicating his ideas to the officers in the headquarters, but he soon found his element in working with an experimental unit established at Boiling Field, D.C. Gatty stressed a system built about dead reckoning (DR), which he viewed as the basic element of navigation, and the meticulous use of a log form. Vital was the accurate calibration of compass and airspeed meter, along with precise in-flight determination and application of drift and groundspeed. The group spent long weeks, patiently installing and calibrating new navigational devices in the Douglas amphibian airplanes. Periscopic drift and groundspeed instruments devised by Gatty were tested, and a protected hatch fitted for sextant and pelorus, the latter used to obtain relative bearings. A temperature gage for the first time was employed for more accurate calculation of true airspeed. Meanwhile, the Naval Observatory published a simplified version of the Nautical Almanac for 1933, the first Air Almanac, incorporating information essential to the airborne celestial navigator in a form convenient for fast computations in the air.

Courses in navigation for Air Corps pilots opened at Langley Field, Virginia, and Rockwell Field, California, late in 1933, with Gatty alternating between the two locations as principal instructor in celestial navigation. In the first class at Rockwell was an officer of unusual talent whose background included the study of astronomy at Stanford. Lieutenant Thomas L. Thurlow easily grasped the essence of the air navigator’s tasks, and he soon became one of the school’s most innovative instructors. Thurlow’s future influence on Air Corps navigation and equipment was apparent in his sole authorship of the first Air Corps text on the subject, Celestial Air Navigation, issued in 1934. Thurlow and Gatty jointly devised a table that simplified calculations by use of the double drift method, whereby drift readings taken on headings 90 degrees apart afforded groundspeed information.

Training flights out of Rockwell included both DR and celestial work over the Pacific, though no night missions were flown. All students were rated pilots. Each received 50 hours’ air work as navigator during the course, along with instrument flying training, in the assigned Douglas amphibians. On those occasions when Thurlow himself assumed the navigation task, his mastery served as a reminder to his colleagues that navigation was more of an art than a science. Both the Langley and Rockwell schools closed temporarily during the airmail operations of 1934. Gatty shortly resigned his position as senior navigation engineer at Wright, in order to work with Pan American Airways in surveying their Pacific routes, but his brief association with the Air Corps left a lasting impression. He served during the war with the Royal Australian Air Force and afterward died in the crash of a Fiji Airways plane.

Gatty’s departure in 1935 left Thurlow, then instructing at Rockwell, as the acknowledged leader in the celestial navigation field. Thurlow moved to Ohio to join the Instrument and Navigation Laboratory, the successor to Hegenberger’s branch. There his contributions to navigation continued in countless projects, including reformulation of the Air Almanac, which had been abandoned since 1934. Thurlow served as navigator for Howard Hughes on the round-the-world journey of 1938. Colonel Thurlow’s continuing work in navigation was acknowledged by an annual award established by the Institute of Navigation in 1945, a year after his death in a takeoff at Dallas while testing a new compass.

One of Gatty’s students in the 1933 Langley school was energetic Second Lieutenant Curtis E. LeMay. Subsequently assigned to Hawaii, LeMay was directed to organize a navigation school in his unit, and soon, with characteristic resourcefulness, this officer was absorbed by the challenge of adapting Gatty’s methods to the local aircraft. Late in 1936 LeMay was assigned to the 2nd Bombardment Group at Langley Field, which was being equipped with the new B-17s. LeMay adroitly evaded the task of setting up the unit navigation training program, but his obvious skill and inclination earned him the job of lead navigator for the important exercises soon to come. LeMay was the lead navigator for the B-17 formation interceptions of the Utah in the Pacific in 1937 and of the Italian liner Rex, 600 miles off the Atlantic coast, the next year. LeMay also navigated on the mass flight to South America in 1938, providing drift readings to the other navigators by using the only gyrostabilized driftmeter in the flight. A self-described “navigator by nature,”1 LeMay’s insight into the profession of navigation remained with him through the higher posts he afterwards held.

These four men—Hegenberger, Gatty, Thurlow, and LeMay—are the central characters in the recently published chronicle of air navigation, researched and written by Norris B. “Skippy” Harbold, Major General, USAF (Retired).* Harbold’s narrative documents the events herein described, revealing that the activities of the four touched on nearly all important developments in air navigation prior to 1941. Intertwining with the work of each of the four was the career of Harbold himself. As a second lieutenant four years out of West Point, Harbold joined Harold Gatty’s research group at Langley in 1932. There Harbold became a kind of interpreter for Gatty’s brilliance. LeMay later recounted how only Harbold seemed able to grasp Gatty’s ideas and would in turn instruct LeMay and the others.2 LeMay and Harbold had been classmates in flying training at Kelly Field. Harbold remained in navigation work at Langley and Rockwell until 1937, working and flying with Thurlow at the latter field.

*Norris B. Harbold, Major General, USAF (Ret), The Log of Air Navigation (San Antonio, Texas: The Naylor Company, 1970, $10.00), 117 pp., 36 plates.

In June 1940 Harbold served on a committee assigned to organize the training programs for the influx of navigator, bombardier, and gunnery students soon to commence. Navigation training for cadets began under contract with Charles Lunn of Pan American, and Harbold spent two strenuous weeks at Coral Gables, organizing the opening of the school with 48 students but without uniforms, study materials, and  (briefly) instructors. During the war Harbold directed navigator training establishments at several bases and became operations chief for Air Training Command. By September 1945 over 50,000 navigators had been trained to use a navigation system differing little from that taught by Harold Gatty a decade earlier. Thus Harbold’s central contribution was to take the knowledge developed by the others and transmit it to those destined to use it in war.

There were other individuals who were less prominent in Harbold’s narrative but whose contributions were large. One was P. V. H. Weems, the retired Naval officer, whose assistance to Air Corps navigational development reached over the entire period and whose methods were reflected in Gatty’s. Another was John Egan, the officer who worked with LeMay in Hawaii and in the early B-17s and who later shared with Harbold many of the tasks of war-time training. Providing continuity at Wright Field over the decades was Dr. Samuel M. Burka, like Thurlow honored by the Institute of Navigation with an annual award in his name.

The record of the twenty years after 1945 was disappointing in comparison, concerning navigation developments for tactical air forces. With the passing of the tactical bombers—the B-45 and B-66—all-weather navigation and bombing capabilities for manned aircraft in the Tactical Air Command (TAC) and the overseas commands declined. The C-123s and C-130s went to Vietnam with a system for airdropping which depended on stopwatch timing from a visual estimate of aircraft position, and the F-105 pilots coming off Thud Ridge sometimes discovered their targets immune to attack because of cloud cover.3 The F-4, its advanced avionics seemingly tailored for a professional career navigator, instead went to war with pilots manning its back-seat position—officers whose career orientation focused on advancing to first-pilot status. Indeed, the belated shifting of navigators into the F-4 was reminiscent of the 1940 decision to train nonpilots as B-17 navigators. Many of the navigators of the postwar Air Force have become dedicated officers of great talent, capable of maintaining the tradition of the earlier pathfinders. Promotion and command opportunities have improved for the navigators, but often only after moving away from navigation and flying duties. Hopefully, the Southeast Asia experience, coupled with the presence of navigators in the current tactical fighter squadrons, will bring new emphasis to the work of this profession.

The technical strengths and weaknesses of Harbold’s book may be quickly summarized. The research is thorough, drawing from materials located in both the National Archives and Air Force Historical Archives; various collections of private papers, including those of Hegenberger and Thurlow; interviews with Hegenberger, Egan, and others; a wide assortment of manuals and technical journals; plus the incomparable range of the author’s personal experience. The brevity of the book—117 pages—is to be regretted, for the expanse of the subject as well as the obvious depth of research would substantiate a fuller account. Stripped to the essentials, the narrative may reflect Harbold’s own characteristic directness of approach. Some thirty pages of illustrations constitute priceless supplements to the text; the footnotes and indexing are precise.

Norris Harbold was chosen one of the early presidents of the Institute of Navigation, founded in 1944. Today he finds that the papers in electronics and space navigation published in the journal of that institute have outdistanced his own technical level. His humility in making this confession is unnecessary: it is in the nature of technology to advance upon the achievements of those who have gone before. As technology advances, however, the qualities needed for leadership in engineering are unchanging. Among the pathfinders of today are to be found the same deep-seated determination and creativity that marked the careers of Harbold, Hegenberger, and the others. The exhilaration of success following upon long periods of endeavor is classic. Few rewards can compare to the emotions felt by Hegenberger and Maitland on reaching Hawaii, by LeMay on intercepting the Rex, or by the Apollo moon walkers in July 1969. Achievements such as these mirror the highest aspirations of modern man.

Alexandria, Virginia


1. Curtis E. LeMay with MacKinlay Kantor, Mission With LeMay (Garden City, New York: Doubleday and Co., 1965), p. 177.

2. Ibid., pp. 94-98.

3. Jack Broughton, Colonel, USAF (Ret), Thud Ridge (Philadelphia and New York:  J. B. Lippincott, 1969).


Colonel Ray L. Bowers (U.S. Naval Academy; M.A., University of Wisconsin) is assigned to the Office of Air Force History, Washington, D.C., working on a history of tactical airlift in Southeast Asia. He has flown as a B-45 navigator-bombardier and participated in the testing and early use of the B-66. He was a history faculty member, USAF Academy (1960-67), and prior to his present assignment was a C-130 navigator with PACAF. Colonel Bowers’s articles have been published in various military journals.


The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.

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