The 30,000-mile swing around the Atlantic Ocean by Colonel and Mrs. Charles A. Lindbergh in the Tingmissartoq in the last half of 1933 resulted in the solution of problems of particular interest to naval aviation. Long overwater flights, a wide range of weather conditions, necessity for accurate navigation, and scarcity of bases are all conditions which have to be met by naval aviators. This flight resulted in practically a 100 per cent performance by both personnel and material and may therefore be used as a guide for future flights. These facts together with the details personally told the writer by Colonel Lindbergh are written down with the hope they may afford an authentic reference for a study of that flight.
Plane data.—The name, Tingmissartoq, which means in Greenland Esquimo language "The man who flies like a bird," was given the Lockheed Sirius monoplane by the Greenland natives. The plane was equipped with pontoons and full dual controls. An auxiliary wing surface connected the pontoons and in addition to strengthening the plane it added several hundred pounds to the lift. The plane cruised at 103 knots when turning up 1,425 r.p.m. and used 25 gallons of fuel per hour. The total gas capacity on the 1,800-mile flight from Bathurst to Natal was 440 gallons, though the gas capacity of the plane had been changed from time to time, and was considerably greater on the Orient flight on which it was used in 1931. Using the most efficient r.p.m., which was as low as 1,350 under light load condition, the plane had a range of 2,300 land miles.
The plane had a wing spread of 42 ft. 10 in., giving it a wing area of 265 sq. ft. At Colonel Lindbergh's suggestion his seaplane was weighed upon his return to New York in order to establish accurately the loading on the South Atlantic crossing.
Actual weight empty but including equipment 4,589 lb.
Weight of Colonel and Mrs. Lindbergh 280 lb.
Miscellaneous baggage 27 lb.
20 gallons of oil at 7.5 lb. per gal 150 lb.
435 gallons of gasoline at 6.1 lb. per gal. 2,653 lb.
Gross weight at time of take-off 7,699 lb.
The true weight empty of the plane including standard instruments, radio, battery, starter, etc., was estimated to be 4,289 lb. after making allowance for approximately 300 lb. of special instruments and equipment carried on the South Atlantic crossing. This gives a useful load of 3,410 lb., or 44.3 per cent.
The total gasoline capacity of the plane was actually 440 gallons, consisting of 320 gallons in the floats and 120 gallons in the wing tanks, but an allowance of 5 gallons was made to cover consumption while warming up before take-off.
The floats were a pair of Edo model 6,075 fitted with special gas tanks and normally rated for a gross weight of 6,400 lb. at 90 per cent reserve buoyancy. They had a total submerged displacement each of 6,075 lb. From the above, the following figures are obtained:
Wing loading at Bathurst take-off 29.0 lb. per sq. ft.
Power loading (710-hp. engine) 10.85 lb. per sq. ft.
Reserve displacement of floats 58 per cent
At the time of take-off the wind velocity was estimated at 10 m.p.h. The water was slightly choppy; air temperature, 18°C.
The sea level top speed of the ship was approximately 185 land m.p.h. and its normal cruising speed 150 m.p.h. at 1,700 r.p.m. However, Lindbergh cruised the 30,000 miles at an average of 1,425 r.p.m. which gave him a speed of 103 knots, or approximately 118 land miles per hour. At this speed the gasoline consumption of the 710-hp. motor was only 25 gallons per hour. During the transatlantic crossing the r.p.m. were held to between 1,350 and 1,390 and the fuel consumption dropped to approximately 21 gallons per hour.
It will be seen from the above that the actual range of the ship in still air was in the order of 2,100 miles, at a cruising speed of 118 m.p.h. Lindbergh's conservative planning is evidenced by the fact that when he picked up the South American coast after 15 hours 55 minutes' flying he still carried approximately a 5-hour fuel supply in his tanks.
When the plane was finally placed in the American Museum of Natural History it had some 41,000 miles of seaplane flying to its credit in addition to several transcontinental flights on wheels. Although a new and latest type motor and propeller had been installed prior to the recent Atlantic circuit, the original plane and floats remained unchanged. In point of service they had seen a total of some 5.5 months' exposure to tropical heat and arctic cold, swinging to a mooring—generally on salt water. Furthermore, the plane had passed through the experience of being partially submerged in the waters of the Yangtze River.
The latter incident occurred in 1931 during preparations for a relief flight over the flooded areas of China and the details are of pertinent interest. The plane was lowered by cables from the British aircraft carrier Hermes in the same manner that its air force seaplanes were handled. It was found, however, that the quick-release mechanism regularly employed with the hoist could not be adapted to the Lockheed without extensive alterations and due to the urgency of the mission the risk of operating without it was deliberately taken.
The motor was left running for the purpose pose of maintaining control as the seaplane was lowered into the swift current but unfortunately it swung broadside to the stream. As it drifted downstream there was no opportunity to get sufficient slack to unhook the cables from the top of the wing and in the absence of any release mechanism the ship was pulled slowly over as the end of the cable was reached. It was then hoisted back on deck and dried out.
Engine data.—Type of engine, Wright Cyclone SR-1820-F2, with direct drive; total hp. at 1,900 r.p.m., 710; 9 cylinders; the engine was fitted with a Hamilton controllable pitch propeller with a diameter of 10 ft., having blade settings ranging from 18.5 to 22.5°.
Flight data.—The flight was undertaken primarily to learn as much as possible of the various routes which could be used for an air service between North America and Europe, in connection with Colonel Lindbergh’s position as technical adviser to Pan-American Airways. Steamship cooperation was furnished by the chartered Danish supply ship, the Jettinge, while in the Greenland-Iceland areas.
The flight commenced at New York on July 9, 1933, and ended there December 19, more than 5 months later. In this time the seaplane traveled 30,000 miles, visited 3 oceans, 4 continents, and 21 countries. The range of latitude extended from south of the equator to about 73°N. The formidable Greenland Ice Cap and the Atlantic Ocean were each crossed in both directions.
Standard equipment.—The plane was equipped with the usual panel instruments of the best available type. This included the air-speed meter, climb indicator, turn indicator, altimeter, r.p.m. indicator, dashboard compass, voltmeter, ammeter, and thermometers. For blind flying the gyro horizon and the directional gyro were mounted in the center of the panel. The 9 principal flight instruments were mounted on an anti-vibrational mounting. The Sperry Gyroscope Company has devoted a great deal of research to this feature, and stresses the importance of it for the more delicate instruments.
Special equipment.—An additional aperiodic magnetic compass with 3-inch card was mounted on the right between the forward and after seats where it might be viewed from either position. This compass was the standard and was used to set the directional gyro which was used continuously for steering. The directional gyro was set at intervals of from 20 minutes to 2 hours, and usually checked, but not set, every 10 or 15 minutes. Lindbergh states that this device is almost indispensable for proper steering in high latitudes near the magnetic pole, especially when flying over water, snow, or in a fog. If steering by magnetic compass, the plane follows the swing of the compass without the pilot being able to detect it, and this change in the course increases the erratic behavior of the compass with the result that the plane is steered on a series of curving courses. The plane may be kept steady on the course when steering by the directional gyro and this permits the magnetic compass to settle down and become more reliable and more accurate for setting the gyro.
A large collapsible rubber boat with 12-ft. mast, 3.5-ft. boom, 2 oars and a sail along with water and one month's supply of food, was carried for emergency purposes. While in the Greenland area a 11-ft. snow sledge, ample arctic clothing, and crampons for traveling on smooth or sloping ice were carried. Some of the unexpected items carried were an outboard motor for maneuvering inside a harbor without starting the motor, rifle and ammunition, machete, fishing gear, Flit, mosquito nets, citronella oil, quinine, blankets, snow veils, scalpel, bandages and other first-aid equipment, revolver and ammunition. Also added at this time was a Very pistol and shells, snowshoes, and an ax.
All of this equipment was not carried on each leg of the flight, but nearly all of it was required in the arctic regions. All of the items carried are not listed as it would require considerable space if the total equipment were itemized. A general idea may be had from the fact that 11 cases of equipment from this, the Orient flight, and the transcontinental flight of 1930 are on display at the museum. Some of the heavier items not mentioned are the 23-lb. anchor, anchor lines, rubber boots, rain clothes, tools, sea anchor, life preservers, 2 hand air pumps for inflating rubber boat, cooking utensils, not to mention 2 radio sets, navigation outfit, and many small items such as needle and thread, wing rope, waterproof match box, etc.
Radio equipment.—The plane carried also two complete radio outfits for trans mitting and receiving, both of which were built by Pan-American Airways. The regular set included a fixed loop built into the fuselage by means of which fairly accurate bearings could be taken by heading toward the sending station. This set was designed for sending in code only, though either code or broadcast speech could be received. Mrs. Lindbergh did all the radio transmitting and receiving in code and did this exceptionally well. She was in communication with South-American stations shortly after leaving Bathurst, and picked up the German ship Westfalen by following its radio bearing. This wide use of radio in addition to the other duties performed by Mrs. Lindbergh is an excellent example of what can be done by the Navy radio operator, if properly trained.
The auxiliary radio set was built by the Pan-American Airways as an emergency set for use with the sledge or in the rubber boat. It was housed in a water-tight case about 18 x 18 x 18 in. and weighs 44 lb. It is self-contained with batteries, transmitter, and receiver, and has a range of 150 miles by day and 1,200 miles at night. In addition to being waterproof, it has been built as nearly shockproof as possible. On test it was dropped 18 ft. on concrete, then operated 300 miles, and submerged in water 24 hours after which it was operated successfully. It may be dropped by parachute to a party in the water or in a jungle where there is no suitable place to land, and by establishing communication, a party may thus be more easily conducted to safety.
Dead-reckoning equipment.—The following special dead-reckoning equipment was carried:
Charts and maps (as many as needed for each flight)
Slide rule
Catty ground-speed and drift indicator
Celluloid 180° protractor.
The charts and maps were obtained from various sources, but the Hydrographic Office marine charts on the Mercator projection were preferred and used when available except for high latitudes. British Admiralty charts Nos. 2202B and 2060A were used for the South Atlantic crossing. A Canadian government equidistant map on the conical orthomorphic projection was used in the Greenland area. This map gives the great circle as practically a straight line, and carries a scale which is correct to 3 per cent for the areas used. No separate chart board was used, it being found that the stiff paper in the charts when properly folded to fit the lap afforded a satisfactory working surface.
The slide rule was used very little.
The Gatty ground-speed and drift meter was used regularly and proved satisfactory. Observations were taken over land, snow, and water, but due to the nature of the flight, drift observations were more useful than ground speed, since when the plane was once committed to a long hop, it was necessary to complete it regardless of the time required or speed made good. In other words no time schedule was required, yet it was necessary in some cases to keep on a definite course if the island destination were to be sighted. The Gatty instrument is installed inside the plane with a periscope arrangement for seeing outside, and this feature was a comfort in arctic regions.
Celestial-navigation equipment.—Effective use was made of celestial navigation. In fact, Lindbergh definitely stated that he would not have undertaken the long over-water flights to the Azores and across the South Atlantic without a sextant. This does not mean that the results of the dead reckoning were not satisfactory, but rather that he insists on having a check for his navigation and on providing for unforeseen conditions. As a matter of fact, Lindbergh thinks that a trained water pilot should expect to reach his objective by dead reckoning alone, but that radio and celestial navigation should both be used as a check on the work. This is certainly a sane view and parallels the expressed view of Admiral Pratt as commander in chief of the U. S. Fleet when he stated, “We should use all means at our disposal for the safe navigation of the fleet.” And our aircraft are becoming more and more a vital part of our fleet.
Although reluctant to say so, Lindbergh confided that his dead-reckoning course was scarcely ever changed. As a test of his work he would habitually estimate his average drift from advance data, and on a few occasions made slight changes of course to allow for an observed (by eye) change of wind, but in no case was it found necessary to alter course when the navigation was definitely checked by drift observations, by radio, or by celestial navigation. These remarkable results should not lead to the belief that all means for the safe navigation of aircraft are not required for, as Lindbergh states, these checks on the navigation are always reassuring and at times vitally necessary. The real meaning of these remarkable results is that over-water navigation is becoming more and more practicable. The improvement in air navigation comes about in most part because of (a) more skilled navigators; (b) improved compasses and use of directional gyro; (c) improved navigation equipment; and (d) higher speed of the planes.
The higher speed of the modern planes reduces the relative wind effect. With low wind velocities and high speeds, the wind drift for distances under 300 miles should cause little trouble. For example, a 10- knot wind on the beam would cause a wind drift of only 4° for a plane making 140 knots, and for 300 miles this would be only about 20 miles. If, by practice, the pilot can estimate the force and direction of the wind say to within an accuracy of 50 per cent this reduces the error in 300 miles to about 10 miles where there are no serious errors in the compass. The greatest improvement in navigation is due to the accuracy in steering by directional gyro when carefully checked by a good magnetic compass. In low winds, Lindbergh thinks a trained pilot can estimate the wind drift nearly as closely as it can be observed by instrument, though of course the instrument should be used as a check and in adverse conditions.
This general dependability of the means for steering a course made it unnecessary to take celestial observations on the first few hundred miles of a flight. Furthermore, if the plane was off course 30 or 40 miles at mid-distance, very little time would be lost. In order to show the sort of celestial navigation accomplished, the details of the Bathurst-Natal 1,800-mile flight will be given. The following equipment was used (see page 658):
The Air Almanac.
Line of Position Book.
Two second-setting navigation watches, one reading in arc.
A Pioneer bubble sextant.
Mercator charts, scale 1:7,727,000.
180° celluloid protractor.
The Air Almanac was considered excellent and a great improvement over the previous Nautical Almanac; in fact, next to the Line of Position Book itself, Lindbergh states that the Air Almanac was the most helpful of any tables used. The two navigation watches kept time to within fraction of a second, a truly remarkable record when the conditions to which they were subjected are considered. The arc reading feature of one of the watches was the Colonel's own invention. In describing to the writer the first of these watches made in 1930, Lindbergh writes, "Mrs. Lindbergh used a dial graduated in degrees for navigating on our transcontinental flight last April. She was able to save considerable time in working out lines of position." With the equation of time set by means of the second-setting feature, the Greenwich hour angle was read directly from the watch face. However, when the Air Almanac was used, the Greenwich hour angle in arc is tabulated against Greenwich civil time, and as Lindbergh observes, the arc reading watch is not needed with the Air Almanac. Neither is the sidereal watch needed for working lines of position of stars when the Air Almanac is available, though it is required for use with the Star Altitude Curves.
The experiences of Lindbergh shows how desirable it is to continue the Air Almanac as it appeared in 1933. We are taking a backward step in the 1934 Nautical Almanac where the features of the Air Almanac are merely added to the old Nautical Almanac data. The Air Almanac in the form it appeared in 1933 best meets the demands of the aviation world, and if continued would be used by an increasing number of mariners.
The route followed by the Lindbergh on the South Atlantic crossing is on page 677, with samples of the celestial navigation accomplished. This shows clearly that tables using an assumed position to the nearest degree are better suited for this work than tables using the exact (?) estimated position. Since the estimated position itself might be in error more than a degree, trying to use an assumed position near the actual position merely adds to the work.
All equipment except the bubble sextant gave excellent results. In the case of the sextant, the bubble element gave trouble—the old familiar story. Otherwise, this instrument was satisfactory. The trouble experienced is not peculiar to this type of sextant, for all suffer from the same trouble. It seems ridiculous that the "bug" can't be smoked out of the bubble, and even if this were done, the bubble sextant would still be the weak link in celestial navigation. On the Bathurst-Natal flight the weather was good, and the natural horizon was used for all sights, the bubble causing trouble by obscuring the natural horizon.
The technique used by Lindbergh is of special interest to naval aviators. As we all know, when taking observations from the air it is tedious work to write down a series of times and altitudes and average them. A dodge to avoid this work was used by Lindbergh. He figured that if he could get three consecutive sights with consistent increments of altitude, the results would not be an accident and that he could trust either or all of them. One minute intervals were found convenient. In smooth air, only a few sights were necessary to get a string of three good ones; but in rough air it would sometimes require patience and a long string of sights. When using the natural horizon it was, of course, much easier to get good sights. When satisfied with the sights, one set of data would be worked out, the line plotted, and the navigation checked. Then one other sight of the three would be worked independently as a check but not plotted. In this way the work was reduced to a minimum, a record was kept, and mistakes avoided.
In laying the course across the South Atlantic, the best weather data showed a northeast wind near Africa nearly balanced by a southeast wind near South America, consequently the wind was ignored in setting the course. This accounts for the slight curve in the course followed, but it will be noted that the plane was nearly on the original course laid down at the time she turned left to sight the SS. Westfalen.
Teamwork of Colonel and Mrs. Lindbergh.—The best lesson to be gained from this flight is the efficient teamwork of Colonel and Mrs. Lindbergh. The work was fairly divided. Lindbergh flew the plane most of the time, but turned the controls over to Mrs. Lindbergh when he took celestial observations and made the necessary calculations. Mrs. Lindbergh transmitted and received all radio messages in code, took repeated radio bearings, and in general did the work of a 100 per cent radio operator. She picked up commercial messages, sent frequent position reports, and received weather and other reports. Also, she successfully operated the Gatty instrument and got groundspeed and drift observations over land snow, and water. In addition to these principal duties, she kept the official log of the flight, and took the controls when her husband was otherwise occupied.
The lesson here to be gained is the fact that the radio operator in a naval plane is also in a position to take ground-speed and drift observations, and otherwise help with the many duties which devolve on the naval aviator.
The principal items of celestial-navigation equipment used on the 1933 flight is on display at the American Museum of Natural History in New York. An interesting view of the plane itself just before it was hoisted to its final resting place is shown on page 659. Note the skeleton of whales in the background.
A careful study of equipment and technique used on the flight of the Tingmissartoq should be helpful to naval aviators.