GB2274934A

GB2274934A - Navigation computer

Info

Publication number: GB2274934A
Application number: GB9302506A
Authority: GB
Inventors: Gordon Albert Alder; Dorothy Isabel Alder
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-02-09
Filing date: 1993-02-09
Publication date: 1994-08-10
Also published as: GB9302506D0

Abstract

A simple mechanical computer designed to produced simplified solutions of aeronautical navigation problems comprises two rigid bodyparts made from transparent material and hinged together at 3 to enclose a disc 7 which rotates within the computer body. The body of the computer is selectively overprinted so as to leave a number of transparent windows 9 and 10 through which printing on the disc can be seen. The results of a series of calculations are printed on the disc. The centre of the computer 11 is transparent with radial lines forming a protractor. The edges of the computer body are marked with a distance scale. Interchangeable discs provide a wide range of solutions of navigation problems. <IMAGE>

Description

SIMPLE MECHANICAL AERONAUTICAL NAVIGATION COMPUTER This invention relates to a simple mechanical aeronautical navigation computer for airborne use by pilots of light aircraft.

Both mechanical and electronic aeronautical navigation computers are well known, but all require the user to enter data and manipulate controls before the solution to the navigation problem is available. During flight this may distract the pilot's attention from other tasks which are essential for flight safety.

This invention provides a computer whereby, for any given cruising speed of an aircraft, following the rotation of a disc, contained within the computer body, simpiified solutions to any navigation problem may be read off. Further by the provision of suitable markings on the body of the computer it may be used additionally as a protractor and distance scale.

The invention will now be described in detail beginning with its mechanical construction which is shown in the accompanying drawings: (Note that in all drawings showing a cross section the thickness has been exaggerated for the sake of clarity.) Drawing 1/7 Figure 1 Front part of the computer body Figure 2 Sections X-X and Y-Y through the front part of the body Drawing 2/7 Figure 3 Back part of computer body Figure 4 Sections X-X and Y-Y through the back part of the body Drawing 3/7 Figure 5 Disc Figure 6 Section through disc Drawing 4/7 Figure 7 Front view of assembled computer Figure 8 Sections X-X and Y-Y through assembled computer Drawing 5/7 Figure 9 Lay out of printing on front part of the body Drawing 6/7 Figure 10 Lay out of printing on back part of the body Drawing 7/7 Figure 11 Lay out of printing on disc Referring to drawings 1/7 and 2/7, the body of the computer consists of two parts 1 and 2 which are moulded from a rigid transparent material, each being in the order of 150 mm square. Along one edge there are matching parts to form a hinge 3. On the opposite edge there are matching parts to form a clip. The two sides adjacent to the hinge have a semi-circular recess 5 cut out. Each part has an annular recess 6 formed in one face.

Referring to drawing 4/7 parts 1 and 2 are joined by the hinge 3 and when closed together are fastened by the clip 4. When the two parts are closed together an annulus 8 is formed.

Referring to drawing 3/7 the disc has a centre hole which is slightly larger in diameter than the boss formed when the two parts of the body are closed. The thickness of the disc is slightly less than that of the annuius 8.

As shown in drawing 4/7, when fully assembled the disc 7 fits into the annulus 8 formed by the closed body. The disc may be rotated by manipulating the edges which project through the cut-outs 5 in the body of the computer.

The purpose of the computer is to present to the pilot the already obtained results of a number of calculations. The basis of these calculations is given, at the end of this description under the heading "Calculation of Data." Information is printed onto the parts of the computer as follows: Referring to drawing 5/7, the front part of the computer is variously over printed (as described below) so as to obscure the surface with the exception of the areas marked 9, 10 and 11, thus forming "windows" in the body through which parts of the disc, contained therein, can be selectively viewed. These transparent areas will be referred to as "windows" in the remainded of this description. Only the first quadrant is shown, but the remaining three quadrants are similarly marked.

The window labelled 10 is one of 125 similar circular, or elliptical, windows which are arranged in five concentric rings; within each ring the 25 windows are spaced at 150 intervals, the 0 reference being at the mid point of the top edge of the body, and which also bisects window 9. Each radial line of windows 10 is extended by a radial line which is numbered in degrees from the 0 reference line and represents the Aircraft'Track across the ground. Each ring of windows 10 is labelled, from the innermost, with numerical values, for example "5," "10," "15," "20," "30," representing the Wind Speed.

Window 9 is an elongated semi-circular window covering an arc of 30 , and is labelled "Wind Direction." The centre window 11 is marked with radial lines spaced at 15 intervals, using the same 0 reference as for windows 9 and 10. An outer scale in window 11 is marked out in 5 graduations.

The two sides adjacent to the hinges are marked with a suitable distance scale (not shown in drawing 5/7.) Referring to drawing 6/7, the back part of the computer is variously over printed (as described below) so as to obscure the surface with the exception of the windows marked 13 and 14.

Window 13 is labelled "Airspeed Disc Fitted." The diameter of window 14 is the same as window 11 on the front part and forms a transparent window through the body of the computer. A small table relating distance, speed and time is printed on this side.

Referring to drawing 7/7 the results obtained from the calculations are printed into the areas labelled 16. These print areas are located precisely as the windows 11 on the front part of the disc. (The circles shown in drawing 7/7 are simply to identify the location of the printing area and are not in fact printed on the disc.) The print area 15 is marked out anticlockwise with a circular scale at 15 intervals, the 0 reference corresponding with the centre line of one radial line of the print areas 16.

Each concentric ring of print areas corresponds to the Wind Speed which is shown marked on the front part of the computer and each radial line of print areas corresponds to the Aircraft Track which is shown marked on the front part of the computer. Note that the 0 reference for these markings is the same as that in the outer scale 15 but that the 15 markings increment clockwise.

Two numbers are marked within each print area 16, one above the other, representing the Track Correction and the Ground Speed, respectively corresponding to the Wind Speed and Aircraft Track for that particular print area. A typical table of calculation results is given below.

The reverse side of the disc is marked at 15 intervals, in the area corresponding to the print area 15 on the front of the disc, with a number which shows the value of Airspeed used in the calculations. These markings correspond with the radial lines of markings on the front of the disc in print area 15.

The computer is used in the following manner. A disc is selected which contains the results of the calculations based on the Airspeed most appropriate to the aircraft cruising speed. This disc is inserted into the body of the computer by locating the centre hole on the boss in the back part. The body of the computer is clipped shut securing the disc but still allowing it to be rotated. The disc is rotated until the appropriate Wind Direction appears in the semi-circular window 9 (aligned with the 0 reference mark). The required Track of the aircraft may be determined by using the centre portion of the computer as a protractor laid onto a chart or map. Using the outer marks on the radial lines 12 the nearest line to the required Track is identified and in the window which most nearly represents the Wind Speed, the correction to the Track and the Ground Speed are read off. The Track Correction is added (algebraically) to the Track to obtain the Aircraft Heading that the pilot should follow.

Unless the Wind Direction significantly alters there will be no need to alter the setting of the disc within the computer body during the flight. Other Track Corrections and Ground Speeds may be read off as required.

The distance scale, marked on the sides of the computer body is used to find from the chart or map the distance across the ground to be covered and using the Ground Speed figure obtained from the computer the distance, speed, time chart on the back of the computer will give the time to be taken to cover the desired distance.

Calculation of Data The variables in the equations are: Wind speed Swind Wind direction Dwind Airspeed of aircraft 5aircraft Track (across ground) Around which are known, and Ground speed Sground Heading of aircraft Daircrae which are unknown and required to be determined using the following equations: Aircraft Heading (Daircraft) = Dground + arCSin(swind x sin(Dwind - Dground) Saircraft) Heading correction = Daircraft - Dground Ground Speed (5ground) = Sir x COS(Doround - Daircraft) - Swind x COS(Dwind - Daircraft) These equations may be simplified by making two of the variables constants, as follows:: For any given aircraft the cruising speed is sensibly constant, so let 5aircraft = K, also the mechanical features of the computer allow the wind direction to be made a constant, so let Dwind = 00.

The equations then become: Aircraft Heading (Dajrcraft) = Dground + arcsin(Swjnd x sin(0 - Dground) + K) . . 1 Heading correction = Daircraft - Dground ............................................................. 2 Ground Speed (Sground) = K x COS(Dgroung - Daircraft) - Swind x cos(0 - Daircraft) 3 Thus by substituting the solution to equation 1 into equation 2, a table can be constructed giving the correction to be applied to the required track across the ground to give the heading to be steered by the pilot, of a given aircraft, for tracks of 0-359 and a range of wind speeds.

Similarly by substituting the solution to equation 1 into equation 3, a table can be constructed giving the ground speed of a given aircraft for tracks of O - 359 and a range of wind speeds.

The two tables can be combined so that both the heading correction can be read off together for and combination of aircraft track and wind speed. The total number of calculations will be limited by considering headings at increments of 15 and for five wind speeds spanning the range of those likely to be encountered by a pilot of a light aircraft. A specimen table of calculated results is given below.

A table to give the time taken to cover a distance at a given speed is constructed from the formula: Time = Distance . Speed, distance and speed being the axes of the table.

Specimen Table of Results Calculated for an Airspeed of 100*

Wind 10 15 20 30 Speed 5 10 15 20 30 Track Grod Track Ground Track Ground to Track Ground Track Ground Track Ground Track Correction Speed Correction Speed Correction Speed Correction Speed Correction I Speed 0 0 95 0 90 0 85 0 80 0 70 15 -1 95 -1 90 -2 85 -3 80 -4 70 30 -1 96 -3 91 -4 86 -5 82 -7 72 45 -2 96 -4 92 -6 88 -7 84 -11 75 60 -2 97 1 -5 94 -7 91 9 87 -13 79 75 -3 1 99 -5 97 -8 94 -11 90 -16 83 90 -3 100 -6 99 -9 97 -11 95 -17 90 105 -3 101 -6 103 -9 101 -11 100 -17 98 120 -2 102 -5 104 -8 105 -11 106 -16 106 135 -2 103 4 107 -7 109 -9 111 -14 115 150 -1 104 3 108 -5 112 -7 116 -10 122 165 -1 105 -2 110 -3 114 4 119 -6 128 180 0 105 0 110 0 115 0 120 0 130 195 1 105 2 110 3 114 4 119 6 128 210 1 104 3 108 5 112 7 116 10 122 225 2 103 4 107 6 109 9 111 14 115 240 2 102 5 104 8 105 11 106 16 106 255 3 101 6 102 9 101 11 100 17 98 270 3 100 6 99 9 97 11 95 17 90 285 3 99 5 97 8 94 11 90 16 83 300 2 97 5 94 7 91 9 87 13 79 315 2 96 4 92 6 88 7 84 11 75 330 1 96 3 91 4 86 5 82 7 72 345 1 95 1 90 2 85 3 80 4 70 * Note: Provided the same units of speed are used throughout for air speed and wind speed, the table may be used for knots (nautical miles/hour), (statute) miles/hour or kilometres/hour, giving the ground speed in the corresponding units

Claims

CLAIMS 1. A mechanical computer for solving navigation problems comprising a two part body, made from a rigid transparent material, enclosing a disc which is free to rotate within the body when the two parts are closed together.
2. A mechanical computer as claimed in Claim 1 wherein the two parts of the body are connected together by a hinge and secured, when closed together, by a catch.
3. A mechanical computer as claimed in Claim 1 or Claim 2 wherein the centre portion is left transparent and marked with radial lines emanating from the centre of the computer body and forming a protractor.
4. A mechanical computer as claimed in any of Claim 1 or Claim 2 wherein the edges of the front part of the body are marked in the form of a rule which may be used to measure distances on a chart or map of the corresponding scale.
5. A mechanical computer as claimed in any of Claims 1 to 3 wherein there are a number or interchangeable discs.
6. A mechanical computer as claimed in Claim 1 wherein the transparent material, from which the body is made, is overprinted in such a way as to obscure the surface with the exception of certain areas through which numbers, printed on the disc contained within the computer body, may be viewed.
7. A mechanical computer as claimed in Claim 6 wherein the windows formed are arranged in five concentric rings (each containing 25 windows) and the windows are arranged in radial lines at 15 intervals, the 0 reference being the line which bisects the body of the computer along any two edges.
8. A mechanical computer as claimed in Claim 1 or Claim 2 wherein side portions of the body are cut away to enable the projecting edges of the disc, contained within the body, to be manipulated with the fingers.
9. A simple mechanical navigation computer substantially as described herein with reference to Figures 1 to 11 of the accompanying drawings.