Gago Coutinho’s constant astronomical observations showed that the Equator passes through Rolas Islet and not between it and São Tomé as had previously been thought. This contribution to terrestrial geography earned him the construction of a commemorative stone (“padrão”) at the highest point on the islet, precisely at the coordinates he himself had determined. Later, on the anniversary of Coutinho and Cabral’s arrival in Brazil, the provincial government in São Tomé decided that Rolas would be renamed Gago Coutinho Islet and that the channel between it and São Tomé Island would become Sacadura Cabral Channel.

When the Mission’s work ended in 1919, he began to prepare what was to become known as the greatest Portuguese adventure of the 20th century – the first air crossing of the South Atlantic. This flight was to differ from earlier journeys because the project was not going to benefit from any naval beacons or radio coverage. The fact was that the aviators could only count on a combination of dead-reckoning and the stars to navigate by. In order to make the former easier, they needed to find a solution that would enable them to graphically calculate the angle between the longitudinal axis of the aircraft and their heading, while taking into account both the speed and direction of the wind, which disrupted the aircraft’s movement in relation to the ground, “and the reference plane used to measure the elevation of the stars” (A Extinção da Aviação Naval [The Abolition of Naval Aviation], 2002, p.8.). This was necessary in order not to have to make drawings in flight, and to overcome geometric difficulties caused by the aircraft’s drift to one side or the other, which is inevitable in any flight between two fixed points.

The two friends first named their invention the “Drift Plaque”, but then changed this to “Course Corrector”. To deal with the problems that arose when it wasn’t possible to see the line of the horizon on the water, Gago Coutinho revolutionised aerial navigation by creating a sextant with an artificial horizon using a spirit level and an auxiliary mirror to reflect the image of the air bubble, in such a way that the distance between the image and the observer’s eye was equal to the radius of the curvature of the plumb. He called this a “precision astrolabe”. It was equipped with an electrical system for lighting the spirit level, which was added by Jorge de Castilho and permitted observations at night.

1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | (Pdf)