First Flight from Europe to the South Atlantic

The History of the transatlantic flights goes back to 1919 and began with a flight performed from Newfoundland to Lisbon; two weeks later another flight was performed between Newfoundland and Ireland. On 1922, the Portuguese airmen Gago Coutinho and Sacadura Cabral crossed the South Atlantic Ocean by air in a flight performed exclusively with internal means of navigation: a new instrument that consisted in a type of sextant improved with two spirit levels to provide an artificial horizon and also with the help of a “path corrector”. Despite this journey had lasted 79 days to cross South Atlantic Ocean, their flight time was only 62:26 minutes, and they’ve flown 8,383 nautical miles, using 3 different hydroplanes christened: Lusitania, Patria and Santa Cruz. Despite this journey had lasted 79 days, their flight time was only 62 h 26 m; they’ve flown 8,383 nautical miles using 3 different hydroplanes christened: Lusitania, Patria and Santa Cruz. The new artificial horizon sextant had proven itself while flying over the ocean, without external references.


I. Background
URING the World War I (1914)(1915)(1916)(1917)(1918) considerable development of aeronautics occurred, although most of the results of the planning had not time to come to daylight before the Armistice. An important example is the NC-4 flying boat (see Fig. 1), designed by Glenn Curtiss and manufactured by Curtiss Aeroplane and Motor Company, to become an alternative to the Allied shipping that was being threatened by submarine warfare. To fulfill the US Navy requirements, this fixed-wing aircraft was designed to be capable of flying between the United States and Europe on its own power, but the demonstration of the transatlantic flight capability only happened after the war was over. This expedition of three NC Flight Boats began on the 8 May 1919 at the Naval Air Station Rockaway (New York), then stopping Newfoundland (Terra Nova), and continuing on the 16 May 1919 to the Azores (Açores). Due to rough weather only the NC-4 with a crew of six people took off again and landed in Lisbon, Portugal, on the 27 May 1919. This became the first fixedwing aircraft to cross the ocean, covering a distance of 4,000 km in 22 hours of flying time at an average cruising speed of 180 km/h, and total installed propulsion power of 1,600 hp. This flight however did not use any kind of astronomical navigation. As a matter of fact it is was decided to dispose 70 ships every 60 miles along the route, and to use directional TSF in the case that the weather conditions did not allow to catch sight of the projectors 1 .
Only two weeks later, the second successful transatlantic flight was achieved the British John Alcock and Arthur Brown using TSF. A distance of 3,040 km between Newfoundland and Ireland was flown non-stop in 16 hours using a modified Vickers Vimy IV twin-engined bomber powered by two Rolls Royce Eagle Engines, each of 360 hp. For this feat they received the Daily Mail prize (13,000 £) 2 and were knighted by King George V 3 . In spite of the Arthur Brown aerial navigation skills only a few observations were made revealing that they had only a limited confidence in the results.
Only a few days after the first transatlantic flight of the American NC-4 flying boat, during the official visit of the President of Brasil to Lisbon, the Portuguese and Brazilian governments agreed to prepare a joint crossing of the South Atlantic between Lisbon and Rio de Janeiro as a way of strengthen the ties of friendship between the two countries reflecting the affinities of language, thoughts and feelings. This initiative consisted in an 8,300 km flight with the most difficult leg between Africa and Brazil where the nearest location was the Cape of S. Roué. In the Africa side the Portuguese administrated island of Cape Verde was the natural option. Between Africa and Brasil there was a landing possibility at the island of Fernando Noronha which is already Brazilian territory, but at that time it was believed that due to the lack of precision of the aeronautical navigation instruments it would be almost impossible to find this small island (less than 10 km of maximum extension) after a 2,330 km of flight over the ocean. So, the first decision of Lieutenant Commander Sacadura Cabral, the aviator that had made the proposal to the Portuguese Government, was to make a non stop flight from Praia (Cape Verde) to the Brazilian coast. This leg would require an aircraft with a range longer than 1,500 nautical miles. The aircraft could be either an airplane or a hydroplane. The first had the advantage that its better aerodynamic performance could provide a longer range with the same engine power or increased payload, but a major inconvenient was the need of landing fields in case of failure. The hydroplane had the advantage that could alight on water to repair any failure avoiding the loss of the aircraft. Even if an airplane with an appropriate range was chosen other problems had arisen: a Brazilian officer to participate in the study of the possibilities had not been appointed, and that would require air reconnaissance to choose each leg, and to prepare the landing fields. So, taking into account all of these variables, and after studying the prevailing winds it was decided to choose a hydroplane between Praia (Cape Verde) and Natal (Rio Grande do Norte, Brasil).
By the end of 1919 Sacadura Cabral had received the confirmation from English, French and Italian aircraft manufacturers that a hydroplane with such a long range could not be delivered, and the mission and to be postponed to a better opportunity. Some time later Sacadura Cabral discussed the subject with his friend Gago Coutinho (Naval Commander) who was involved in cartography projects and scientific astronomy navigation, and decided to make some experiments to develop means of aeronautical navigation. Sacadura Cabral though that it they were successful they could find the small island of Fernando Noronha in the Atlantic, refuel, and then proceed to the Brazilian Coast. The sextant used by the navy could not be applied to aviation due to the difficulty of the definition of the sky-line at a normal flight altitude. Gago Coutinho developed a new model of sextant that could be used to measure the altitude of a star without the need of the sea horizon. This new instrument was called "precision sextant" (see Fig. 3) and used an artificial horizon line which was defined with the help of a water bubble 4-8 . It also used an illumination system to allow its use during weak light conditions, including the night. An advanced version of this instrument started to be manufactured in Germany by C. Plath under the name of "System Admiral Gago Coutinho". Another instrument called "path corrector" was also developed by Gago Coutinho to calculate graphically the angle between the longitudinal axis of an airplane and the direction of flight, taking into account the intensity and the direction of the winds.
In March 1921 an experimental flight was made from Lisbon to Madeira (520 nautical miles). Above all, they sought to prove that air navigation could be just as accurately pursued as sea navigation, by deploying sextants and other available astronomical devices. The trajectory should be a perfect straight line, and to verify the position of the aircraft three ships were used to control its position. The result was a complete success. Sacadura Cabral then start to believe that the aeronautical navigation could provide the same precision of the nautical navigation, and the aircraft range could be substantial reduced to 1,260 nautical miles which was the distance from Praia and the island of Fernando Noronha (see Fig. 2).
Finally Sacadura Cabral got the necessary approval of the Portuguese Government, but it continued very difficult to find an adequate hydroplane now due to budget restrictions. Actually, the amount allocated to the mission was £ 5,000 (sterling pounds), including not only the aircraft but also, the necessary transportation, spares, fuel, etc.

II. First Flight across the South Atlantic
In spite of all the restrictions and other difficulties the preparation of the mission started with the selection of the hydroplane. Due to the limited budget it should be a single engine, and as consequence the engine was the most critical issue. The 350 hp Rolls-Royce Eagle engine that was used in the first non-stop transatlantic flight (airline b in Fig. 2) was selected. Considering that the fuel consumption would be about 18 gallons per hour at a cruising speed of 70 miles, and then the 1,260 miles from Praia to F. Noronha would require 324 gallons. To calculate the total payload it should added at least 150 lbs. of oil and water, the weight of the crew, the instruments and extras, reaching a total of 3,170 lbs. Using the performance of the American hydroplane that had flown from Newfoundland to Lisbon it was thought that the 350 hp Rolls-Royce engine would be sufficient for a payload of 7,000 lbs, and consequently the aircraft should have a maximum weight of 3,830 lbs (55% of the total weight). The hydroplane chosen was a Fairey III D manufactured by the British company Fairey according to the Portuguese specifications. Unfortunately, the hydroplane did not takeoff with the maximum payload specified in the contract. Several modifications were made, including the change of the engine, the location of the fuel tanks (from the wings to the floats), the fuel system, and finally with the help of a wind a little stronger than the specification the Fairey III D had flown.
The voyage began in Lisbon at 7 am on the 30 th March of 1922 with the Fairey III D called "Lusitania" (Fig. 5). At noon the observed position   was 31 o 27'N latitude and 13 o 44'W longitude, so they had flown a distance of 484 miles, corresponding to an 81 miles of average speed. The fuel consumption was 20 gallons per hour which was 11% higher than expected. Additionally, the engine was discharging oil that was spreading everywhere including the face and glasses of Sacadura Cabral. Nevertheless, at 25h37m they had alighted in Las Palmas, although a stronger ondulation caused the rupture of two cables that connected the wings to the floats. The Portuguese ship "5 de Outubro" was expecting the aviators inside the harbor, and it was arranged a place to make the necessary repairs and revisions. At 11h13m on the 2 nd April the preparation for take-off started and it was found that the floats had some water inside. The aircraft initiated the trip to Gando to refueling. During the trip no discharge of oil occurred, but Sacadura Cabral noticed a pitching moment nose-up of the aircraft. After refueling with 240 gallons of gasoline, the tail float plunged too much in the water. Some modifications to the floats were attempted, but on the 3 rd April, before departure it was found that the problem was still there. The major concern was that at Praia, before the longest leg (to F. Noronha) there was no possibility of taking the aircraft out of water to drain the floats. After repairing the "Lusitania" take-off occurred only at 7h35m on the 5 th of April. In the meantime it was decided to make an additional stop at S. Vicente in Cape Verde where the Portuguese government had an official workshop. At 19h18m they had travelled the 849 miles and reached S. Vicente. The aircraft was moved to the workshop where the technicians started immediately to do the necessary improvements. In the meantime they confirmed that the fuel consumption of the engine was not less than 20 gallons per hour, and the flight from Praia to F. Noronha would be dependent on the winds, and even so it would be necessary to drain all the water from the floats at Praia what was impossible. So, the only possibility was to make an additional stop near the Rocks of S. Peter and St. Paul (Fig. 6) and try to do the refueling there. The ship "República" would wait there for the arrival of the "Lusitania". On the 17 th of April it was initiated the flight to Praia which happened with no major problems in 2 hours and 15 minutes. On the following day Sacadura Cabral had to do three attempts to takeoff due to the sea and wind conditions, and two hours after departure the pilot realize that there were only 195 gallons of fuel left, which meant that they had less that 10h of flight left. Gago Coutinho and Sacadura Cabral decided to continue expecting a change to a more favorable wind. At 16 h the main fuel tanks were empty, and only 24 gallons existed at the gravity tank. From the observations they located the Penedo's, but the problem was still remaining and consisted in having or not enough fuel. At 17 h they come in sight of the small island and at the very same time of the ship "República" that was located at about 8 miles to NW. Notwithstanding their arrival with hardly any fuel left, one of the aircraft floaters was destroyed by the crest of a wave and the hydroplane tilted and sank soon thereafter (Fig. 7). There was still sufficient time to a cutter from "República" to arrive and the pilots were saved together with some books, the Gago Coutinho precision sextant (Fig.3), the chronograph and other instruments. The ship "República" proceeded to F. Noronha, and the orders of the Portuguese government were to wait for the arrival of a new aircraft and then to proceed the mission. Against the airmen's hopes, however, this second hydroplane ("Portugal") ended  Paul's) Rocks and the fact that the ship's passengers could not wait for favorable weather for more than two days. It was decided, therefore, to fly from Fernando Noronha to St. Peter (& St. Paul's) Rocks where the Lusitania had sunk, and then proceed back to Fernando Noronha and onwards to Recife. Five hours after take-off, the aviators saw St. Peter (& St. Paul's) Rocks from about 15 miles, but heavy rain made them decide to skip this 15 miles distance and turn back towards the refueling ship "República" located in route at azimuth 25 N, 70 miles from Fernando Noronha. About 1 hour and 50 minutes later, the engine stopped due to fuel carburation hiccups, leading to a forced sea landing. They managed to restart the engine for some 55 minutes but, before they could take off, the engine stopped never to restart again. As the floaters began to sink slowly, one of the airmen sat on the engine to reduce the rear weight on the floaters. Meanwhile, the "República" had realized something had gone wrong and sent radio messages to ships nearby announcing a probable incident. About 1 hour and 20 minutes later, when Coutinho and Cabral's hopes were vanishing under fatigue and sleepiness, a distant light in the dark emerged to which they responded with two gun shots. They were rescued by the freighter "Paris City" on its way from Cardiff to Rio de Janeiro. A third Fairey 17 named "Santa Cruz" was then shipped to Fernando Noronha in a Portuguese Navy ship "Carvalho de Araújo" and the voyage was immediately continued to Recife, Salvador de Baia, Porto Seguro, Vitoria and Rio de Janeiro without any major incidents.

Conclusions
The crossing of the South Atlantic by two Portuguese navigators that used for the first time methods of astronomic navigation when flying out of sight of land was described.
The navigation methods and instruments were tested during short flights, and then applied with quite success to the flight between Lisbon (Portugal) and Recife (Brasil) in 1922.
For the first time in the history of the aviation the crossing of the South Atlantic had been achieved and using an instrument that enabled an aeroplane position to be determined by astronomic navigation when flying out of sight of land.