WO2013014645A1 - Flight computer - Google Patents

Abstract

An aeronautical ruler includes, on at least the first side (2), at least one disc (3) and a second disc (4), both graded and movable for the implementation of two- variables computations, and a third graded disc (5), working with the first (3) and the second one (4), for the implementation of three-variables, and comprising at least a first window (6) for the reading of the result of a three-variables formula, derived from a certain alignment of the first (3), the second (4), and the third one (5). The ruler comprises, on the second side (12), two overlying, concentric, and sliding discs (13,14), which are properly graded and comprising of trigonometric conversion tables (14c) in order to solve, through proper alignments, the wind triangle and compute the drift angle of an aircraft. The slide ruler does not comprise transparent discs for the graphical solution of the wind triangle.

Description

DESCRIPTION

FLIGHT COMPUTER

Technical field

The present invention relates to a flight computer, in particular an aeronautic slide (sliding) ruler.

In aviation, mainly dominated by electronics, there are cases, especially in the academic and training field, in which the use of sliding rulers (even if it is an analog instruments) still has several advantages.

The aeronautic sliding ruler, in fact, remains a valuable teaching and academic tool because it allows you to make calculations without losing any physical meaning, thereby maintaining an awareness of the steps required and the logic that leads to a certain solution. With a slide ruler, for example, it is possible to rapidly visualize the result of an operation by varying a parameter.

State of the art

The currently known slide rulers allow one to graphically play calculations of varying complexity that would normally require the use of electronic calculators, or, if manually done with paper and pen, a long time of resolution and relative increase in the possibility of errors.

This tool is generally based on the properties of logarithms, allowing, for example, carrying out multiplications and divisions through simple graphics operations .

There are essentially two types of slide-ruler: linear and circular; in the aeronautic field the latter is used, making possible a greater number of operations with respect to the linear case. Another important advantage of the circular slide ruler lies in the ease of use when dealing with several orders of magnitude of the involved factors.

A circular slide ruler works by relatively rotating two discs and matching the chosen parameters so as to read, in correspondence with sliders or indexes of reference, certain values that are nothing more than the solution of simple equations with two variables.

Said device allows to implement functions to be used in the aeronautic field, using the composition of elementary approximated operations, which provide a rough idea of the numerical result that has to be obtained .

The calculations that can be made with a traditional aeronautic ruler are very simple and mostly limited to conversions between measurement units, corrections to information coming from atmospheric measurements that have to do with altitude, pressure, and temperature, the calculation of fuel consumption and the estimated time to reach a given destination, knowing ground speed and fuel consumption (using, crudely, the relationship velocity = space / time) , the computation of the true airspeed (anemometer) from the indicated airspeed (which is affected by errors caused by pressure, temperature, compressibility and positioning of the sensor) . The traditional slide ruler still allows computing the ground speed starting from the true airspeed of the aircraft and the characteristics of the wind, with a graphical solution of the problem.

An example of slide ruler that has found widespread use in the last fifty years is the Jeppesen CR-3.

This device is composed of two discs in the front and allows to perform simple division and multiplication calculations, conversions of measurement units, the identification of parameters of interest such as aircraft altitude, speed, temperature and pressure in different ways, depending on the needs of the pilot and, sometimes, of the reference model.

The back is more particularly devoted to navigation, allowing, through sine and cosine scales, to identify the components of the ground speed as a function of the encountered wind. In the inner part there is a transparent disc, which allows the user to graphically calculate the velocity triangles depending on the flight conditions .

The Jeppesen device is still used in flight schools and colleges for aeronautical technical aspects of training and education, especially for courses of flight mechanics .

The Jeppesen ruler, like others currently on the market, only allows performing conversions between units or simple equations with no more than two variables.

Very useful it would be instead to calculate, for example, the range and the endurance of an airplane, or other functions that are mathematically more complex. In addition, on the side that allows the calculation of the triangle of the wind, it is necessary to visually track lines on a transparent disc that is part of the ruler, and then erase before a new use. As a consequence, the use of the ruler is uncomfortable and results impossible in the absence of a supporting surface or a pencil.

Many other instruments were designed to solve analogous functions. An example is described in patent US3350007. In this document a device is presented that comprises a graduated ruler slidable with respect to two rotating discs, which are also graduated. This is an alternative to the Jeppesen patent with regard to the calculation of the wind triangle.

A similar instrument, that is useful for the resolution of the wind triangle, and therefore for the calculation of the drift angle of an aircraft, is described in the document FR2754894. This instrument consists of three linear graduated rulers hinged together, interacting with two circular compasses.

As mentioned above, the analog instruments currently known do not allow to perform complex calculations, particularly those that require at least three variables, such as the calculation of the cruise range by means of Breguet's formula. Moreover, these tools do not allow an easy numerical solution of the wind triangle problem, because of the graphic interface.

Aim of the invention

In this context, the technical task underlying the present invention is to propose a circular slide ruler that overcomes the drawbacks of the prior art mentioned above . The purpose of the present invention is to suggest a new slide ruler that is able to provide, to pilots and engineers, an easier resolution of the same problems already solved by regulating known.

Another object of the invention is to introduce additional aspects of performance of the aircraft from design parameters, in addition to the integration of various empirical rulers that are extensively used in some operating manuals.

Furthermore, the purpose of the present invention is to propose an aeronautical ruler as a tool for renewed teaching in technical schools, where greater attention is given to the interaction between different disciplines such as, for example, navigation and aeromechanics.

In particular, it is an object of the present invention to provide an instrument capable of performing complex calculations (for example the cruise range) in a particularly simple way (i.e. minimizing the movements to be performed and the information to be stored or write) .

Further object of the present invention is to suggest a method to solve the wind triangle exclusively by numerical means, without the aid of a pencil.

The mentioned technical tasks and the aims specified are achieved by a circular slide ruler that comprises the technical characteristics set forth in the appended claims .

The invention comprises, on the first face, a first and a second hard disc, both with graduated scales and reciprocally movable for the implementation of the calculations, and a scale to read the results.

According to the invention, the device comprises a third graduated disc with its own scale and is movable with respect to first and second discs.

The three discs include at least a first reference mark, to enable an alignment of the three discs by setting the mutual positions of the first reference mark (3b) and the values of three variables identified on the corresponding scales of the three discs.

In addition, the ruler comprises (on one of the three discs) a second reference mark, in order to detect on the reading scale the result of a formula involving three variables, as function of the alignment of the three discs.

In this way, the invention allows to calculate the result of a formula with three variables by performing two alignments only (i.e., by aligning the three discs in pairs of two) , by exploiting the four references consisting of the values of the three variables of the formula and the first reference mark.

The result of the formula can be directly read, without having to remember any intermediate result (a part of the formula comprising only two variables) , and without having to use this intermediate result to align the disks.

This allows, advantageously, to carry out the calculation with less time (minimizing the steps to be carried out in the displacement of the discs) and with less waste of mental energies, as should not be taken to match any partial intermediate memory.

This is particularly useful for the implementation of the formula for the calculation of the Breguet's range of the aircraft.

This formula is shown below:

"E * V/C * In (W1/W2) " .

In this formula, E is the aerodynamic efficiency, C the specific consumption, V the flight speed, and with Wl / W2 the weight fraction.

An alternative version of said formula is the following: "sqr(E * V/C * ln(Wl/W2))".

In this formula, E is the aerodynamic efficiency, C the specific consumption, V the flight speed, and with Wl / W2 the weight fraction, "sqr" is the square root.

In this context, the formula in three variables is:

"E * V/C".

The ruler of the invention is configured to solve this formula, "E * V/C", aligning the three discs, not counting any partial or interim results of that formula and without having to use such a partial result for the alignment of the discs.

Note that each of the three discs comprises at least a logarithmic scale, to implement the formula in which the variables are combined by multiplication and division. The second disc is interposed between the first and the third disc.

Preferably, the second disk defines a first scale, for an alignment with the first disc, and a second scale, for an alignment with the third disc.

Preferably, one between the first and the second scale of the second disk define the reading scale of the aforementioned formula with three variables.

Preferably, the first reference mark is disposed on the first disk and the second reference mark is disposed on the third disc.

In this case, the second scale of the second disk is preferably used to define the reading scale of the three -variables formula.

The ruler comprises a further reading scale, reported on the discs and said configured to implement a formula with four variables for the determination of the cruise range of an aircraft.

Preferably, the aforementioned reading scale is disposed on the third disc and is configured so as to allow a view of the result of the described formula with four variables at the second reference mark.

Preferably, the slide ruler of the invention comprises: - a further reading scale configured to implement a formula for determining the airspeed of an aircraft, by means of the lift equation, as result of the alignment of at least two of the first, second and third discs, and

- a further scale configured to implement a formula for the determination of the aerodynamic efficiency of an aircraft, by means of the equation of the aerodynamic efficiency, as result of the alignment of at least two of the first, second and third discs.

Therefore, the slide ruler of the invention allows to calculate the range of an aircraft, without having to go through the calculation of any partial result devoid of interest (for the purposes of teaching or practice) , meaningless from the physical point of view or for the theory of flight, employing a minimum number of movements, in a particularly efficient manner. According to another aspect of the present invention, the aeronautical slide ruler comprises, on at least a second face (opposite to the first face, which has the three discs as described above) , two overlaying disks, concentric, having different diameters and rotating one with respect to the other one.

These disks (according to the second face) are appropriately dimensioned and designed, only through appropriate alignments and trigonometric correspondences, the wind triangle and calculate the wind drift of an aircraft, without the use of any transparent disc for graphic resolution of the wind triangle .

Brief description of the drawings

Further characteristics and advantages of the present invention become more clear from the descriptive point of view with a non-limiting embodiment of a preferred but not exclusive slide ruler, as illustrated in the accompanying drawings in which:

- Figure 1 is a front view of the circular slide ruler of the present invention;

- Figure 2 is a rear view of the circular slide ruler of the present invention.

Detailed description of preferred embodiments of the invention

With particular reference to the accompanying figures, number 1 has been indicated as an aeronautical slide ruler in accordance with the present invention.

The ruler 1 has a front face 2 dedicated to the calculation and display of aeronautical parameters, through the aid of logarithmic scales and viewing windows .

The slide 1 comprises, on the first face 2, at least a first 3, a second 4, and third 5 disc, all graduated and reciprocally movable. Advantageously, the three discs 3, 4 and 5 are overlaid, coaxial and relatively rotatable to one another, around a central axis la.

The three disks 3, 4, and 5 have different diameters: in particular, the first disk 3 has a larger diameter than the second disk 4 and the third 5 disc, and the second disc 4 has a diameter intermediate between the first 3 and third 5 disc.

The first disk 3, which is the outer one, simply presents a logarithmic scale 3a that is necessary to the third manual calculation of certain parameters, and some colored marks 3b that, when aligned with the relative marks 4b of the second disc 4, allow to perform conversions between measurement units from the international system 3a ', 4a ' to the Anglo-Saxon 3a", 4a" and vice versa.

The second disc 4 is intermediate and has a logarithmic scale specular to that of the first disk 3, with the corresponding marks 4b, previously cited for conversion tasks; several scales (described below) are printed, which allow, with the aid of the third disc 5, to find the parameter of interest.

The interaction between the first 3 and the second 4 discs allows the implementation of a simple calculation, generally conversion of units or calculations with two variables . The third disc 5 is essential to carry out more complex calculations: in fact, it interacts with the other two disks 3 and 4 via one or more rotations.

The cooperation of the third disc 5 with the first 3 and second 4 allows the implementation of the calculations of formulas to three variables.

The third disc 5 innermost comprises at least one window 6, inside which a result is viewable as obtained from a formula with three variables derived by appropriate rotations, alignments and/or iterations of rotations between the first 3, the second 4 and third 5 disk.

Advantageously, the third disc 5 has a plurality of windows 6, 7, 8, and 9 as well as the proper reference slots 5b' , 5b " , 5b ' ' '.

Some of the main parameters calculated by the interaction of two or more disks 3, 4, and 5 are conversions between units, preferably from the international system to the Anglo-Saxon system and vice versa, variation of the air density and sound speed with the altitude, calculating the Mach number, maximum efficiency and the relative coefficient of lift in conditions of maximum efficiency. It is also possible to calculate the minimum path angle in gliding flight, the actual speed or TAS (True Air Speed) , the characteristic velocity programs for jet and propeller aircrafts cruises. Finally, through the interaction of all the three discs, the range and endurance can be calculated (through Breguet' s formula).

In addition to these parameters, however, an infinite number of other calculations can be performed, through the use of logarithmic scales that are external to each disk .

Along the external perimeter of the ruler, particularly along the outer perimeter of the first disk 3 and the second disk 4, two logarithmic scales 3a and 4a are located, with some colored marks 3b and 4b.

The latter are located in well-defined positions, in order to perform some of the conversions between units, which are mostly used in the aeronautical field.

It is possible to make conversions from the International System (SI) to the Anglo-Saxon (UK) and vice versa, simply by aligning the two marks on the units of interest. Note that the conversion can be done from the external disc 3 to the intermediate 4 or vice versa .

Arranged on a central portion of the second intermediate disk 4, there is a plurality of graduated scales, indicating flight parameters such as, for example, the cruise range 4d, the Mach number 4e, the coefficient of lift at maximum efficiency 4f, the maximum efficiency itself 4g and the corresponding minimum path of the descent trajectory 4h in gliding flight and the actual speed or TAS 4i.

These values are readable through a plurality of windows 6, 7, 8, 9, made in the third disc 5, as a result of an appropriate alignment of the latter with the second disc 4.

In particular, following the relative rotation of the first disk 3, the second disk 4 and the third disk 5, suitably aligned by placing the corresponding reference marks 3b, 4b, and 5b in correspondence with the selected parameters or by matching two values of two different discs, you can determine the desired flight parameters: specifically, as a result of the mutual interaction between the three discs, the cruise range of an aircraft is readable within the first window 6 of the third disc 5.

The third disc 5 has, in turn, logarithmic scales graduated 5a indicating characteristic flight speeds 5g, flight altitude 5h, percentage of fuel consumption 5c and coefficients of fuel consumption per hour 5d.

As shown in Figure 1, the windows 6, 7, 8, and 9, into a plurality of circular sectors, divide the third disc 5. In particular, on the circular sector 11 of the third outer disk 5 are shown, for a ready reference, the tables showing the air data. In the first table 5e correspondences between flight altitude and air density are shown, while in the second table 5f, the correspondences between the flight altitude and the speed of sound are reported.

The first table 5e presents a numerical scale that represents the outer part (in km) and an inner part corresponding to the density of the air (in kg/m^A3) .

A scale indicating the flight altitude, expressed in feet, which should be read together with the logarithmic external scale 5a, placed along the outer perimeter of the third disc 5 constitutes the second table 5f. On the logarithmic scale 5a, one can read, at the desired altitude, the values of the speed of sound in knots. Some parameters, such as the value of the Mach number, are located as a result of only one relative rotation between two disks, in particular aligning the second 4 and the third disc 5, and then reading the value directly into a 7 second window of the third disc 5. The second window 7, as can be seen from Figure 1, is preferably located in a central position.

In particular, for the calculation of the Mach number 4e, one aligns the speed of the aircraft, represented in logarithmic scale 4a on the second disk 4, with the desired height, for example the sea level (SL) , considered in the scale of speed of sound (table 5f represented on the third disc 5) . Within the second window 7 of the third disc, in correspondence with the reference mark 5b ', it is possible to read the result relative to the number of Mach 4e.

For other parameters, at least two iterations between two disks are required.

For example, for the calculation of the maximum efficiency, 4g aligns with the reference mark 5b ' ' ' of the third disc 5 with the value of the coefficient of induced drag, or with the value of the coefficient of parasitic resistance, both inside of the graduated logarithmic 4a of the second disc 4. Then one finds, on the third disc 5, the other parameter still not set (and therefore the parasitic drag coefficient in the first case or the coefficient of induced resistance in the second) and reads the value in correspondence to the second disk 4. Finally, aligning the latter read value with the reference mark 5b ' ' ' of the third outer disk 5, the value of 4g maximum efficiency is read within a third window 8 of the third disc 5, in correspondence of the mark 5b' ' . The third window 8 is preferably located in an intermediate position within the third disc 5, between the first 6 and the second 7 windows. Another parameter that can be calculated by the slide ruler 1 is the minimum path angle of the descent trajectory 4h in the absence of thrust. The latter parameter is closely related to the maximum efficiency 4g. Therefore, within the third window 8, a scale is also shown with correspondences between the minimum path angle 4h and the maximum efficiency 4g.

Regarding the determination of the coefficient of lift at maximum efficiency 4f, align the second disc 4 and the third disc 5, by matching the value of the parasitic drag coefficient set on the second disk 4 with the value of the coefficient of induced drag on the third disc 5. Within the second window 7 of the third disc 5, indicated by the reference mark 5b', one reads the corresponding value of the coefficient of lift at maximum efficiency 4f.

The ruler also gives the possibility to calculate the true airspeed of the aircraft 4i (TAS, True Air Speed) , with the variation of the wing loading and the lift coefficient.

It is sufficient to choose on the second disk 4, within the 4a logarithmic scale, the value of the desired wing loading and align it with the coefficient of lift chosen along the graduated logarithmic scale 5a of the third disc 5. At the desired altitude, indicated on a second circular sector 10 of the third disc 5, placed around the third window 8, there is the true air speed in meters per second, readable in a fourth window 9 of the third disc 5. Window 9, preferably made of transparent material, presents an annular shape and separates the first circular sector 11 from the second outer circular ring 10 inside.

In the case where you want true air speed in knots, it will be necessary to use the altitude in feet, always indicated on the third disc 5 but along an inner circumference 5b of the outer sector 11.

A parameter of fundamental importance to design a mission is the calculation of the cruise range, or the detection of the traveled distance, based on the available fuel.

In particular, one can make suitable assumptions, for example, to be at almost level flight, so that we assume to carry out flight schedules that maintain constant speed and attitude and, therefore, for which the flight altitude increases with continuity during the course of the flight. Apply here the so-called Breguet formulas for jet or propeller aircrafts.

With the slide ruler of the present invention it is possible to solve these equations: the relative complexity of these formulas necessarily needs more steps of calculation and the interaction of all the three disks of the ruler, by providing successive rotations that take advantage of the setting of a value found with a previous alignment of two discs.

In these equations some natural logarithms are present, solved by means of few marks 5b ' ' ', positioned along the outer circumference of the third disc 5, which indicate the ^xconsumption' of weight of the aircraft in terms of percentage to the initial weight.

In particular, for the calculation of the range it is necessary to set the reference mark 3b of the first disk 3 with the flight speed indicated on the logarithmic scale 4a of the second disc 4.

One can rotate the third disc 5 in order to align the hourly consumption, reported on the outer circumference of the third disc 5, with the value of efficiency, which is the starting data, identified on the logarithmic scale 3a of the first disk 3.

Once having set the three disks in the positions described above, we read what is the value indicated on the logarithmic scale 4a of the second disc 4, by the reference mark 5b ' ' ', in the outer part of the third disk 5.

This second value on the second disc 4 must be aligned with 5c the percentage fuel consumption reported on the third disc 5 and finally we read, in the first window 6 of the third disk 5, indicated by reference mark 5b ' ' ' , in the outer part of the disc 5, the value of range of the aircraft at a certain speed, with a certain efficiency and with a given fuel time consumption.

Advantageously, the first window 6, from which one reads the value of range, is formed along a portion of the first circular sector 11 of the third disc 5.

The slide 1 also comprises, advantageously, a second face 12 which has at least a first 13 and a second disk 14 overlying, concentric and with different diameters. These discs 13 and 14 are rotatable relative to one another and allow to obtain, simply by appropriate alignments and trigonometric correspondences, the wind triangle so as to calculate the angle of drift of the aircraft .

Advantageously, the first 13 and the second disk 14 of the second face 12 have diameters that are different from each other, in particular the first disk 13 is the outermost and has a larger diameter.

On both discs there are reference marks 13b and 14b, which represent the indices with which aligning the different values.

The first disk 13 comprises a plurality of graduated logarithmic scales 13a, indicating the numerical values of wind speed and its components, arranged along the outer perimeter.

In a central portion of the first disc 13, there are further tables of graduated scales indicating correspondences between the parameters related to the flight speed 13c, the corresponding landing distance in conditions of dry 13d' or wet 13d'' runways, the bank angle 13e and the radius of turn 13f as functions of a certain flight speed 13c and the rate of descent 13g, depending on the angle of descent and for a given flight speed .

The first disc 13 also comprises a first angular linear scale 13h.

The second disc 14 includes a first outer portion 15, having the form of a circular sector, a circular central portion 16 and at least a first window 17, between the first outer portion 15 and the central portion 16, through which to show some of the parameters on the first disc 13 below. Advantageously, the second disc 14 includes at least a second window 18, formed within the central portion 16.

Through the first window 17 of the second disk 14, one reads the angular linear scale 13h, while through the second window 18 there are tables of correspondence between the various parameters reported in the central portion of the first disk 13.

Along the outer perimeter of the outer portion 15, the second disc 14 comprises a plurality of graduated logarithmic scales 14a through which it is possible to carry out multiplications and divisions.

On the outer part 15 of the second disc 14 there are trigonometric scales 14c that allow you to calculate sine and cosine functions with their inverses.

Proceeding towards the inside of the external circular sector 15 of the second disc 14, there is a second angular linear scale 14d which, interacting with the first angular linear scale 13h of the first disk 13 (visible from the first window 17 of the second disc 14), allows you to make additions and subtractions between angles. In particular, the latter allows the identification of the wind direction. All this makes this sector a great tool 15 to perform navigation calculations and, in particular, to study how the wind affects the flight by varying the direction and the intensity of the flight speed.

In particular, depending on the direction of the wind on the aircraft, it is possible to have Head Wind, Tail Wind, with or without lateral components. A compass, indicating type and then angle of incidence of the wind, can be found inside the angular linear scale 13h reported on the first disk 13 (and visible through the first window 17 of the second disk 14) .

The central portion 16 of the second disc 14 is a table of conversion 19 between Celsius and Fahrenheit degrees.

The central part of the second face 12 of the slide 1 is dedicated to the resolution of some parameters that are associated with particular maneuvers not been addressed in the front side, which is primarily dedicated to cruise performances.

In particular, through the interaction of the first 13 and the second disk 14 of the second face 12 of the ruler, it is possible to calculate the radius of turn and the bank angle, the landing distance, both in case of dry 13d' and wet 13d'' runways, and the rate of descent 13g.

The calculation scheme and the identification of the parameters calculated using the second face 12 of the ruler are entirely analogous to those described above with reference to the first face 2.

The second face 12 of the ruler 1 has an innovative method for the resolution of the wind triangle, as explained below, useful to the calculation of the angle of drift of the aircraft.

When an aircraft is in flight, its movement with respect to ground will be composed with the displacement of the entire mass of air. To maintain the predetermined route, the pilot must rotate the nose of the aircraft just enough to counteract the movement of the air. He must then make a geometric correction on the route to follow, depending on the intensity and direction of the wind.

The problem therefore becomes to know by which angle it needs to correct the cruise, in the presence of a given wind, to maintain the predetermined trajectory.

This problem can be solved by drawing a velocity triangle where two sides (the wind and the true airspeed of the aircraft) and the angle between one of these and the third side (that is, between the wind direction and the route of the aircraft) are known. The analog instruments currently in use allow calculating this angle graphically, physically drawing the velocity triangle.

The ruler the present invention, instead, allows to solve the problem of the wind triangle and calculate the angle of drift by trigonometry, i.e. only through a calculation .

In particular, using the second face 12 of the rod 1, only by suitable rotations of the two disks 13 and 14, it is possible to determine the angle of drift of the aircraft .

Specifically, one uses the angular linear scales 13h and 14d to obtain the angle between the actual route and the direction of the wind. Then it is possible to align the mark 14b of the second disc 14 with the value of the angle of the actual route, shown on the angular linear scale 13a of the first disk 13. So one reads on the second disc 14, in correspondence with the relative angular tilt of the wind direction indicated on the 13a linear angular scale on disc 13, which is the angle a between the two trajectories: in other words, appropriately aligning these two discs 13 and 14, one performs a difference between the direction of the trajectory of the actual route and that of the wind.

Having obtained the angle a, one aligns the reference mark 14b of the second disk 14 with the value of the wind speed, read on the graduated logarithmic scale 13a, present on the outer perimeter of the first disk 13.

Once aligned the two discs 13 and 14, it is stated, in correspondence with the sine of the angle a, (identifiable in the trigonometric scale 14c present on the circular sector 15 of the second disc 14), the value of a component of the wind speed, read on the graduated logarithmic scale 13a present on the outer perimeter of the first disk 13. Then one aligns the value of the just found velocity component of the wind (as read from the graduated logarithmic scale 13a of the first disc 13) with the value of the actual speed of the aircraft, located on the logarithmic scale 14a of the second disk 14, and reads the ratio, on the first disk 13, at the value indicated by the reference mark 14b of the second disk 14.

Finally, on the trigonometric scale 14c of the second disc 14 one reads the arcsine of the just determined ratio to get the angle of drift.

This system avoids the use of graphics for the resolution of the wind triangle and the calculation of the angle of the wind drift.

It should be noted that the present invention provides an aeronautical ruler comprising, on one of its faces 12 (referred to as "second face" in the description above) two discs 13, 14 overlying, concentric, having different diameters and relatively rotatable with respect to one another, wherein disks 13 and 14 are appropriately sized and include trigonometric conversion tables 14c to solve, exclusively through appropriate alignments and correspondences, the wind triangle and calculate the angle of the wind drift, without any transparent disc for graphic resolution.

Preferably, discs 13 and 14 (of the aforementioned second face 12) comprise a first disk 13, having a greater diameter, with a plurality of graduated scales 13a indicating numerical values of wind speed and its components, arranged along the outer perimeter.

Preferably, the first disc 13 (of the second face 12) includes graduated scales, placed in a central portion, indicating correspondences between the tables of parameters related to the flight speed 13c, the landing distance in conditions of dry 13d' or wet 13d'' runways, the bank angle 13e, the radius of turn 13f and rate of descent 13g depending on the angle of descent; the first disc 13 of the first face 12 also comprises, between the central portion and the outer perimeter, a circular sector on which a first angular linear scale 13h is shown.

Preferably, the second face 12 includes a second disc 14, having a smaller diameter, comprising a plurality of graduated scales indicating trigonometric conversion tables 14c, linear angular values 14d and a conversion scale between Celsius and Fahrenheit 19.

Preferably, the second disc 14 (the second face 12) has at least a first window 17 which is visible from the first angular linear scale 13h of the first disk 13 of face 12.

Preferably, the second disc 14 (the second face 12) has at least a second window 18 from which graduated scales indicating the aforementioned tables of correspondences are visible, placed in a central portion of the first disc 13 (of the second face 12) .

Note that, in the preferred embodiment, the slide ruler comprises (at least) five discs: - three mutually movable discs on the first face 2 (as described above) ;

- two mutually movable discs on the second face 12 (as described above) .

The main advantage of the proposed ruler is related to the new features introduced.

In this way, the ruler proves to be a useful estimation tool for typical users (student pilots and students in technical schools) and as an innovative way for college students.

In particular, the described ruler allows to obtain the maximum efficiency, the minimum path angle for gliding in conditions of maximum efficiency and the computation of the coefficient of lift in conditions of maximum efficiency. Furthermore, this ruler allows to solve the equation of the level flight, by calculating the true and the indicated airspeed, and to implement the Breguet's formulas for cruise range and endurance, also taking into account the fuel consumption.

Moreover, this ruler gives indications on the characteristic speeds for cruise and maneuvering compared to the condition of maximum efficiency.

In addition it provides correspondences between

- the landing distance (in wet and dry conditions) , - the vertical speed approaching the runway,

- the bank angle,

- the radius of turn and the speed of flight.

Finally, it allows a rapid resolution of the wind triangle exclusively by trigonometry, without the aid of graphic means.

Clearly, the ruler of the present invention are can provide valuable support to the phases of training of pilot students and students of aeronautical technical schools and universities.

The ruler of the present invention, serving as a portable and efficient means of calculation, results to be more useful and practical, both for the study of the flight mechanics and for navigation. In particular, with the use of the slide ruler, one can immediately calculate and display various aircraft parameters, as well as tables of data conversion of aeronautical interest .

In addition, the ruler of the present invention allows to obtain the result of more complex formulas that cannot be not be solved by traditional devices.

Furthermore, with the traditional devices one can carry out studies almost exclusively via the graphics, while, with the straight edge, it is possible to solve the same problems without the need to resort to a pencil and a support surface, but simply rotating and aligning in a suitable manner the disks that compose it.

Claims

CLAIM

1. A flight computer defined by a slide ruler comprising, at least on a first face of it (2), at least a first disc (3) and a second disc (4), both graduated with scales and movable relative to each other for implementing calculations, and a readout scale for reading a formula result,

characterized in that it comprises a third disc (5) graduated with a third scale and movable relative to the first and second discs, the discs (3, 4, 5) comprising at least a first reference mark (3b) , to allow the three discs to be aligned by setting the positions of the first reference mark (3b) relative to the values of three variables identified on the corresponding scales of the three discs (3, 4, 5), and a second reference mark (5b' ' ' ) for identifying on the readout scale the result of a three-variable formula, according to the alignment of the three discs.

2. The flight computer according to claim 1, wherein the second disc (4) defines a first scale, for alignment with the first disc (3) , and a second scale, for alignment with the third disc (5) , the second disc being interposed between the first and the third.

3. The flight computer according to claim 2, wherein either the first or the second scale of the second disc (4) defines the readout scale.

4. The flight computer according to claim 3, wherein the first reference mark (3b) is positioned on the first disc (3) and the second reference mark (5b' ' ' ) is positioned on the third disc (5) .

5. The flight computer according to any of the preceding claims, comprising a further readout scale, the scales and readout scales being configured to implement a four- variable formula for determining the fuel range (4d) of an aircraft.

6. The flight computer according to claim 5, wherein the further readout scale is positioned on the third disc (5) and is configured to allow reading of the result of the four-variable formula at the second reference mark.

7. The flight computer according to any of the preceding claims, comprising:

a further readout scale configured to implement a formula for determining the flying speed of an aircraft using the lift equation, in response to alignment of at least two out of the first, second and third discs; and a further scale configured to implement a formula for determining the aerodynamic efficiency of an aircraft using the aerodynamic efficiency equation, in response to alignment of at least two out of the first, second and third discs.

8. The flight computer according to any of the preceding claims, wherein the third disc (5) comprises a plurality of windows (6, 7, 8, 9) configured to implement formulas relating to flight parameters, allowing reading of the values of the parameters by aligning at least two out of the first, second and third elements.

9. The flight computer according to any of the preceding claims, wherein the third disc (5) has graduated logarithmic scales (5a) indicating characteristic airspeeds (5g), flying altitude (5h), percentage fuel consumption (5c) , hourly fuel consumption coefficients (5d) , a first air data table (5e) indicating flying altitudes in relation to air density, and a second air data table (5f) indicating flying altitudes in relation to the speed of sound.

10. The flight computer according to any of the preceding claims, comprising, on a second face of it (12), at least two superposed concentric discs (13, 14) differing in diameter and rotatable relative to each other; the discs (13, 14) being suitably graduated and comprising trigonometric conversion tables (14c) for calculating, through suitable alignments and trigonometric relationships, the wind triangle and an angle of drift of an aircraft.

11. The flight computer according to claim 10, wherein the discs (13, 14) of the second face comprise a first disc (13), larger in diameter, comprising a plurality of graduated scales (13a) on the outer perimeter of it, indicating numeric values of wind speed and wind speed components.

12. A flight computer defined by a slide ruler comprising, at least on a first face of it (12), two superposed concentric discs (13, 14) differing in diameter and rotatable relative to each other; characterized in that the discs (13, 14) are suitably graduated and comprise trigonometric conversion tables (14c) for solving, exclusively through suitable alignments and trigonometric relationships, the wind triangle and calculating an angle of drift of an aircraft; the flight computer not comprising any transparent disc for graphically solving the wind triangle .

13. The flight computer according to claim 12, wherein the discs (13, 14) comprise a first disc (13), larger in diameter, comprising a plurality of graduated scales (13a) on the outer perimeter of it, indicating numeric values of wind speed and wind speed components.

14. The flight computer according to claim 13, wherein the first disc (13) of the first face (12) comprises graduated scales, positioned in a central portion, indicating tables of relationships between parameters relating to flying speed (13c), landing distance under dry (13d') or wet (13d") runway conditions, bank angle (13e), turn radius (13f) and vertical component of descent speed (13g) as a function of the descent angle; the first disc (13) of the first face (12) also comprising, between the central portion and the outer perimeter, a circular crown on which a first linear angle scale (13h) is indicated.

15. The flight computer according to claim 14, wherein the discs comprise a second disc (14), smaller in diameter, comprising a plurality of graduated scales indicating trigonometric conversion tables (14c), linear angle values (14d) and a Celsius to Fahrenheit conversion scale (19).

16. The flight computer according to claim 15, wherein the second disc (14) has at least a first window (17) through which is visible the first linear angle scale (13h) of the first disc (13) of the first face (12) .

17. The flight computer according to claim 15, wherein the second disc (14) has at least a second window (18) through which are visible the graduated scales indicating the relationships tables in a central portion of the first disc (13) of the first face (12) .

18. The flight computer according to any of the claims from 12 to 17, comprising at least on a second face of it (2), at least a first disc (3), a second disc (4), and a third disc (5) , all three being graduated with scales and movable relative to each other for implementing calculations, and a readout scale for reading a three-variable formula result, wherein the discs (3, 4, 5) comprise

at least a first reference mark (3b) , to allow the three discs to be aligned by setting the positions of the first reference mark (3b) relative to the values of three variables identified on the corresponding scales of the three discs (3, 4, 5), and

a second reference mark (5b' ' ' ) for identifying on the readout scale the result of the three-variable formula, according to the alignment of the three discs.

19. The flight computer according to claim 18, wherein the second disc (4) defines a first scale, for alignment with the first disc (3) , and a second scale, for alignment with the third disc (5) , the second disc being interposed between the first and the third.

20. The flight computer according to claim 19, wherein either the first or the second scale of the second disc (4) defines the readout scale.

21. The flight computer according to claim 20, wherein the first reference mark (3b) is positioned on the first disc (3) and the second reference mark (5b' ' ' ) is positioned on the third disc (5) .

22. The flight computer according to any of the claims from 18 to 21, comprising a further readout scale, the scales and readout scales being configured to implement a four-variable formula for determining the fuel range (4d) of an aircraft.

23. The flight computer according to claim 22, wherein the further readout scale is positioned on the third disc (5) and is configured to allow reading of the result of the four-variable formula at the second reference mark.