Lindbergh watched in anguish as others attempting his feat disappeared at sea. After finishing his Latin American and Caribbean tour with the Spirit of St. Louis in early 1928, he was eager to find better equipment and procedures for future flights. Though he had dismissed celestial navigation for his trip to Paris, during his return aboard the USS Memphis he was enthralled with the ability of the ship’s navigator to fix position with sun and star sextant sightings, and he resolved to pick up the skill, writing, “It was a lot of fun ‘shooting the sun’…with the Memphis sextant. I was fortunate enough to hit it with a fair degree of accuracy.”
Upon his return, Lindbergh began planning an around-the-world flight, scheduled to kick off a few months later in a Ford Tri-motor provided by Henry Ford and copiloted by his close friend, Thomas Lanphier. That April, he went to observe air operations aboard the USS Langley, where he encountered an enthusiastic Navy Lieutenant Commander, Philip Van Horn Weems, who was conducting navigation experiments for carrier-based aircraft. Weems demonstrated several of his innovations to Lindbergh, including a bubble sextant that he was helping the National Bureau of Standards to improve, and his prototype Second-Setting Watch: the first true aviator “hack” watch that could be set precisely to the second. (Later, the military realized a major benefit of this precision, and began to synchronize multiple watches for field operations, thus making famous the line “Gentleman, synchronize your watches.”)
Several weeks later, after donating the Spirit to the Smithsonian Institution, Lindbergh decided he would set out from Washington for Detroit to finalize his plans with Ford and Lanphier. He felt the trip would be an ideal time to learn “avigation”—a popular term used in the 1920s and ’30s to differentiate air navigation from maritime practice—and asked polar explorer Lincoln Ellsworth for suitable tutors. Ellsworth recommended Weems.
Shortly after Roald Amundsen’s 1925 Arctic flight, in which the crew was nearly lost after a crash-landing, Ellsworth had begun looking in earnest for better aerial navigation techniques. At the time, Weems was an instructor at the Naval Academy in Annapolis, and though not a pilot, he found the problem of using celestial navigation in airplanes to be an interesting intellectual challenge. His conservative Navy superiors disagreed and rejected his request for funding to develop a simplified system. Weems’ ideas so impressed Ellsworth, however, that he helped finance the research.
Lindbergh petitioned the White House for Weems to be assigned as navigation tutor, and the Navy officer received a leave of absence, to the irritation of his superiors. He told Lindbergh later, “My relations with the Navy Department [have] been rather peculiar. I get patted on the back by one crowd and kicked in the pants by another!”
Not surprisingly, most Americans assumed Lindbergh was an expert in all things aeronautic, and learning that he needed training in navigation left many reporters confused. When Lindbergh began his training with Weems, the New York Times wrote, “It will be news to…millions that Colonel Lindbergh needs to be taught navigation…. If the Colonel doesn’t know how to navigate, who knows anything about anything?” But the publicity started a conversation in the aviation community, one thoroughly documented by the newspapers of the time, about the poor state of air navigation and the potential for celestial navigation to be a solution on long over-water flights.
Weems approached Lindbergh’s training with items from his bag of tricks, including his hack watch. Previous chronometers could be set only to the minute; this was an acceptable error for 19th century mariners who might go weeks or more before stopping and making an adjustment, but not for 20th century pilots who could use radio broadcasts to synchronize their timepieces. A watch error of 30 seconds could throw off a position calculation as much as seven miles, so Weems’ innovation was significant.
Weems used most of the lessons to teach Lindbergh how to find his position by shooting the sun with a very rare sextant. It was a 1924 Bausch & Lomb model, of which only six were made, and Weems believed it was still the best model available in the United States. Bubble sextants had been around for more than a decade, but because so little attention had been paid to aerial navigation, their design had not advanced much. During his sessions with Lindbergh, Weems carefully studied the sextant’s deficiencies, later taking his notes to the National Bureau of Standards, which worked with Bausch & Lomb to produce an improved version that saw wide service in the 1930s.
Another Weems innovation used in Lindbergh’s training was the Star Altitude Curves, a revolutionary set of charts that let a navigator find his position using two stars (one was usually the North Star, Polaris). The graphs helped cut the calculation time from 15 minutes to 40 seconds. During the day, instead of triangulating position using two stars, a navigator could use the sun to determine a line of position. By measuring the angle between the horizon and the location of the sun on its daily path, a navigator could draw a line on the globe and be assured that his position was a point somewhere on that line.
In Line of Position, Weems published the ultimate Cliffs Notes for this more difficult calculation. Though Lindbergh had dropped out of college to fly, he proved to be an excellent student and “toiled cheerfully for days over head-splitting mathematics,” Weems noted in a letter to a friend. “Lindbergh makes a fine student. He [studies] till twelve or one o’clock and does not get ‘fussed’ or rushed.” During a visit to New York, Weems stayed with Lindbergh to spend extra time tutoring, but found that he “didn’t really do much instructing”; the pilot “was brilliant and caught on quickly. He instructed himself.”