Flight Calculator.
Flight Calculator in a Breguet XIX.
The Slide Rule donated by the Contributor J. Pérez-Cruz.
Flight Calculator by Carlos de Haya González.
Original drawings of rudders.
"Patent Haya" Flight Calculator story, including donation to the Air Force and the Navy Aeronautics. Draft document with Captain Haya's handwriting.
Flight Calculator donated to the Air Force and the Navy Aeronautics.
French patent for the Flight Calculator.
Click on photo to see image enlarged.


The Inertial guidance meter or “Haya Patent” Flight Calculator , which as early as 1931 had already been registered in the Spanish Patent Office under Nº 123.609 for that same year, was the result of our subject’s study, hard work and the ability to observe and synthesise, transforming simple ideas into practical and brilliant solutions.

At the end of the same year in December 1931 it was used by Captain Cipriano Rodriguez (Cucufate) and the creator himself in their flight from Seville to Guinea and on 24th October 1933, it obtained the French patent Nº 739.107 which had been applied for by the patent office of Taviera and Botella in Madrid.

In a brief article containing terms and expressions verging on the colloquial - very typical of aviators - Carlos de Haya himself described his calculator in the 1935 September issue of the Aeronautical Review as follows:

“ Every aviator that uses an inertial navigation system needs to make a series of calculations to determine their position in the air taking into account the headings and distances covered. The art of setting a course correctly do not require any complicated calculations; a simple addition or subtraction of the deviation shown on the compass for the course in question can be easily done in the head.; where calculations are required and definitely cannot be done mentally is when working out the distance covered or the speed maintained in relation to the ground, or the time it takes to reach a specific point. In other words, there are three factors involved in these calculations: distance, speed and time; the fact is, to multiply or divide we need to resort to pencil and paper, something which is a bit of a nuisance when you are flying, and what is more, to do so as often as is required would mean having to devote some time to it, thereby distracting us from other matters that may be important; moreover, because of the conditions in which the aviator finds himself while in flight, being unable to pay the same amount of attention as on the ground, there is a risk of making a mistake.

And if the pilot is the one who actually wants to do these calculations then the whole affair takes on an acrobatic character as he would need to hold the paper properly and would be making hurried scribbles instead of numbers, the result being hardly any effective arithmetic. Finally, is there a pilot who does not remember with desperation trying to manipulate a pencil, tied to a string to prevent it from escaping, eventually seeing its tip broken bringing to an end any hope of trying to fix it ?

Haya knew well how tedious it usually is for many pilots to carry out even the simplest arithmetic calculations during flight. Thus, he refers to the “nuisance” of having to use pencil and paper, a syndrome familiar to all those from all periods who have flown.

“ This way of navigating without making a single calculation allows us in a more or less approximate manner to determine our position on the horizontal plane which, once done, leaves us with only having to compare it with the land surface in order to rectify any slight error that may exist. This means that, in order to avoid losing our bearings, we would have to be constantly observing and comparing the land surface with the horizontal plane without being off guard for even a moment; in other words, we need to carry out a watchful navigation”.

What he calls a good “watchful navigation and attentive to the compass” becomes essential for achieving an inertial navigation system.

“….When, for any of the reasons mentioned above, it is necessary for us to know our exact position, while knowing our speed and time, or if we need to find out our speed, knowing the distance covered and the time, or if we need to calculate when we will arrive at a given point, knowing the speed and distance yet to be covered, we must resort to the Inertial guidance meters, which in a fast and simple mechanical way solve these problems for us.

Let us look at one of these devices which, thought up by its creator, has been used on several flights, one in particular being that celebrated flight of Barberán and Collar, which could be regarded as being a truly admirable display of inertial and astronomical navigation.

And from this was born the idea of the Flight Calculator, of which a few were already in existence at that time, but once again we find our intrepid inventor coming up with his “Columbus’ egg”, a brilliantly simple idea made easily practicable; the handling and solving of problems becomes as simple as drawing a line on a graph with a couple of indices, involving at most two or three consecutive operations, and the noting down of some data.

A demonstration:

This flight calculator, or more precisely known as an Inertial guidance meter, consists of an aluminium casing inside which, rolled up into two reels, is a large strip of paper containing:

1. An abacus
2. A double entry table with headings and distances and
3. A table with sunrise and sunset hours as well as the days of full moon.

The strip of paper containing the above mentioned graphs, is rolled up into two reels which are simultaneously spun in one direction or another by means of a small handle of a size that makes it easily operable with the thick airman’s gloves; the calculator can be easily mounted on the instrument panel, and the printed numbers are sufficiently large to enable the pilot to comfortably read them without moving from his seat.

The handle is operated with the left hand in such a way that the pilot need not take his hand off the control stick.

These tables can be read through a window on the device on the edges of which are two speed calculators, one expressed in kilometres, the other in miles; both guide a cursor whose aim is to make some of the operations easier. The strip of paper is easily taken off allowing the pilot to make notes and add any new graphics that he finds interesting.

Thus, the pilot can use this instrument as a kind of memorandum which, while allowing him to use it as an aerial slide rule also serves as a data check (engine consumption, magnetic deviations, adjustments to the anemometer, bombing raid table), which he might find of interest during the flight and which must contribute to the total success of the mission he has been entrusted.

With such elementary equipment as this the following problems could be solved, all relating to the speeds and consumption rates of the planes of that age but which, if we change the units and the magnitudes, are still the same basic navigation problems of today, of Concorde or any other aircraft.
With Table 1:

1. How long it would take to reach a point if we know the distance and the real speed of our plane.
2. At what real speed we are travelling, if we know the time taken to cover a known distance.
3. At what distance we are from a given point, if we know the speed and the time we have been flying.
4. How long we can remain airborne, if we know the amount of petrol we are carrying and the consumption rate of our engine.
5. The consumption of our engine, if we know that a given amount of petrol has been consumed in a given period of flying time.
6. How much petrol we should carry in order to stay airborne for a certain period of time, if we know the consumption rate of the engine.
7. The radius of action of our plane, if we know the consumption rate of the engine and the real speed.
8. Miles can be converted to kilometres and vice versa.
9. We can quickly find out the distances and the headings for a vast number of aerodromes in Spain.

Using the table indicating the sunrise/sunset and the full moon, all the information of interest to the pilot can be obtained easily.

With the performance table, if we know the consumption rate and the speed we can find the best system for the engine, for the least consumption per kilometre.

He goes on to give solutions to standard problems one by one, using the different scales and tables, all on the same strip of paper. The calculator offered really extraordinary possibilities with such little effort that it became an important element in many flights made during that period. In 1933 it was used by Captain Berberan, an exceptional navigator, in his flight from Seville to Havana. The same year it was used in the Round Spain Trip for light aircraft by Captain Gil Mendizabal, Lieutenant Garcia Morato, Captain Pruleda and the civilian Fernando Flores, in whose plane it was installed and was used by the owner and the inventor. It had also been used by the Cuatro Vientos School of Observers in its regular courses from 1933 onwards.


Finally, in July 1935, the inventor offered the patent to the Aviation Service Corps and to The Naval Air Force, who took up the offer and responded with gratitude, as he explained in an official despatch sent to the Air Commander in Chief, dated in Seville on 6th November 1937, four months before his glorious death in combat. In that communiqué, expressed in the honest noble tones he reserved for solemn occasions, Haya declared that the “Flight Calculator” devised by him was “well known in the Aviation Service Corps who, according to despatch number 214 dated 25th September 1935, expressed their thanks accepting the offer of Spanish Patent number 123.609 registered in 1931”, reaffirming then and there the transfer of his rights on the said patent, and considering himself honoured that its acceptance might have make modest contribution…!”

All this information has been obtained from the following writings, books and encyclopaedias:
-Espasa-Calpe Encyclopaedia
- Aeronautical History Review (October 1989 issue nº 7/ November 1990 issue nº 8) R. de Madariaga.
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