Astronomic Air Navigation

Precision Astronomical Navigation

One of the great innovations of this journey was the use of a method of precision astronomical navigation adapted to the use of aircraft. By managing to reach the Penedos de São Pedro e São Paulo, after more than 11 hours of flight, over the Atlantic Ocean, without any reference or outside help, they showed the whole world that it was possible to fly to any point on the globe and be sure of getting there

In addition to developing a method of precision astronomical navigation, Gago Coutinho also developed:

The sextant with a bubble level, allowing the creation of an artificial horizon, and the adaptation of this instrument to aeronautical use
The course corrector, which allowed him to determine and correct the drift caused by the wind

What is the Artificial Horizon Sextant?

The artificial horizon sextant or bubble sextant is an air navigation device and in precision astronomical navigation is used to measure the height of a star without having to resort to the sea horizon, a device that invented by the Portuguese admiral Gago Coutinho.

Through the bubble sextant (artificial horizon sextant) it is possible to materialize an artificial horizon through a spirit level, leaving the reading of the height of a star (sun or other celestial bodies) independent of the possibility of visualization of the horizon. It was an adaptation of the classic navy sextant to air navigation conditions, in which there are often difficulties in viewing the horizon line, since planes often fly above this line and also to cloudiness. The device thus allowed precision astronomical navigation, taking measurements day and night, navigating without resorting to the visualization of terrestrial references and with an accuracy of a few minutes of degree, allowing to plan the navigation with a margin of error of the order of ten of kilometers.

The invention would revolutionize air navigation methods, allowing it to be carried out with precision, without any outside assistance, and marked the birth of what would provide the current artificial horizon, for instrument flight.

The artificial horizon sextant, the invention of Gago Coutinho, was characterized by the result of the adaptation of a conventional sextant where a spirit level and a mirror and optical system are installed, in such a way that the horizon line was no longer necessary to determine the altitude of a star. Altitude is determined by the artificial horizon sextant, measuring the angle between the observed celestial body and a horizontal reference line. With the artificialization of the horizon line, the additional advantage of taking readings at night or in poor visibility conditions was achieved by using a lighting system. The initial system only included a level to indicate horizontality, but it later evolved into one that included a second bubble level to indicate verticality.

What is the Course Corrector?

The course corrector was used as a graphical process for solving the speed triangle, thus providing the wind direction and speed, the useful aircraft speed, and the course correction to continue the desired trajectory.

What is Precision Astronomical Navigation?

The precision astronomical navigation is part of a branch of astronomical sciences used for guidance purposes and whose mission is, making use of logarithmic tables, to annul the translational and rotational movements of planet Earth in order to freeze the apparent ones, relative to the Sun, to Moon and stars 365 days a year, the system offers the pilot the exact position of the stars for every moment of observation, as if they were always fixed in the sky. This knowledge, made with the verification of the height of the stars in relation to the horizon, allows the navigator to correct his estimated position.

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