GB1605171A – Instruments for aircraft
– Google Patents
GB1605171A – Instruments for aircraft
– Google Patents
Instruments for aircraft
Download PDF
Info
Publication number
GB1605171A
GB1605171A
GB5368674A
GB5368674A
GB1605171A
GB 1605171 A
GB1605171 A
GB 1605171A
GB 5368674 A
GB5368674 A
GB 5368674A
GB 5368674 A
GB5368674 A
GB 5368674A
GB 1605171 A
GB1605171 A
GB 1605171A
Authority
GB
United Kingdom
Prior art keywords
aircraft
value
clearance
determining
computer
Prior art date
1975-12-05
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB5368674A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
UK Secretary of State for Defence
Original Assignee
UK Secretary of State for Defence
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1975-12-05
Filing date
1975-12-05
Publication date
1982-10-13
1975-12-05
Application filed by UK Secretary of State for Defence
filed
Critical
UK Secretary of State for Defence
1975-12-05
Priority to GB5368674A
priority
Critical
patent/GB1605171A/en
1982-10-13
Publication of GB1605171A
publication
Critical
patent/GB1605171A/en
Status
Expired
legal-status
Critical
Current
Links
Espacenet
Global Dossier
Discuss
Classifications
G—PHYSICS
G01—MEASURING; TESTING
G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
G01S3/782—Systems for determining direction or deviation from predetermined direction
G01S3/785—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system
G01S3/786—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically
G01S3/7864—T.V. type tracking systems
G01S3/7865—T.V. type tracking systems using correlation of the live video image with a stored image
Description
(54) IMPROVEMENTS IN OR RELATING TO INSTRUMENTS FOR
AIRCRAFT
(71) 1, THE SECRETARY OF STATE
FOR DEFENCE, LONDON, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:
This invention relates to instruments for aircraft and in particular to instruments for determining the ranges from the aircraft of landscape features and for determining the clearances between the flight line of an aircraft and features of the landscape over which the aircraft is flying.
For military missions the technique of fast low-level approach, maintaining as far as possible a minimum safe clearance above the ground, is frequently considered to be desirable.
In conditions of good visibility it is possible for a skilled pilot to use such a technique, estimating his clearance from his direct view of the terrain over which he is flying and using his skill and experience to maintain a safe but lowlevel course. When visibility is poor the pilot no longer has a good direct view of the terrain. A view of the terrain can be had by the use of low-light television or infra-red line scan apparatus, but the view is considerably degraded compared with a direct view and it is only two dimensional, so the pilot’s estimate of his clearance based on such a view will be less reliable.
In any case the technique by its nature involves keeping close to the limits of safety, so it is desirable to give the pilot as much help as possible with the aid of instruments.
It is known to measure range by means of forward-looking radar and similar echo-sounding techniques such as laser range-finding, and it is known to use radar equipment to control an aircraft automatically to follow the profile of a terrain. The disadvantage which radar shares with other forward-looking echo-sounding techniques however is that it involves sending out signals from the aircraft. These signals may be detected by an enemy and serve to advertise the presence of the aircraft which it is an object of the fast low-level approach technique to hide.
It is an object of the present invention to provide instruments for determining range or clearance which do not involve the use of forward-looking echo-sounding techniques.
According to the present invention in one aspect thereof there is provided an instrument for determining the range R from an aircraft of a landscape feature lying substantially in the vertical plane containing the flight line of the aircraft, comprising: means for determing 0, the angle below the flight line of the aircraft of a sight line from the aircraft to the feature; means for determing A, the rate of increase of the angle of the sight line below the horizontal; means for determining V, the ground speed of the aircraft; and computing means for computing the range according to the relation
R = VO IA, none of the said means including forward-looking echo-sounding sensors.
According to the present invention in another aspect thereof there is provided an instrument for determining the clearance C between the flight line of an aircraft and a landscape feature lying substantially in the vertical plane containing the flight line of the aircraft, comprising: means for determining 0, the angle below the flight line of the aircraft of a sight line from the aircraft to the feature; means for determining A, the rate of increase of the angle of the sight line below the horizontal; means for determining V, the ground speed of the aircraft; and computing means for computing the clearance according to the relation
C = V o2 la, none of the said means including forward-looking echo-sounding sensors.
A flying aid for aircraft according to the invention may comprise means for determining 0, the angle below the flight line of the aircraft of each of a plurality of sight lines from the aircraft to respective landscape features lying substantially in the vertical plane containing the flight line of the aircraft; means for determining
A, the rate of increase of the angle below the horizontal of each of the sight lines; means for determining V, the ground speed of the aircraft; computing means for computing the range R and the clearance C of each of the features according to the relations R = V 0/h and C = V02/A and calculating a safe clearance Co(R) for each of the features according to a predetermined relation; and warning means for giving a warning signal whenever the computed clearance of any of the features is less than the safe clearance, none of the said means including forward-looking echo-sounding sensors.
The warning means may be adapted to give a preliminary warning signal whenever the computed clearance of any of the features, while being greater than the safe clearance, approaches the safe clearance. The preliminary warning signal may, for example, be an intermittent signal whose frequency increases as the computed clearance approaches the safe clearance.
The invention may be used in conjunction with an electro-optical sensor such as a low- light television apparatus or an infra-red line scan apparatus which produces a pictorial display of the terrain ahead of the aircraft, and the warning signal and preliminary warning signal may include a visual signal superimposed on the pictorial display so as to indicate which features are giving rise to the signal. The warning signal may include an audible warning signal to distinguish it from a preliminary warning signal.
Of the drawings accompanying the provisional specification:
Figure 1 is a geometrical drawing illustrating the principle of the invention,
Figure 2 is a block diagram showing an exemplary layout of the invention,
Figure 3 is an exemplary logical flow diagram for a correlator for use in the invention, and
Figure 4 is an exemplary logical flow diagram for a computer for use in the invention.
Figure 1 shows an aircraft A and a feature X on the ground. The horizontal through the aircraft is shown by the line AH. The flight line
AV of the aircraft makes an angle 0 below the horizontal AH. The angle of the sight line AX below the flight line AV of the aircraft is 0. The angle of the sight line AX below the horizontal, which is clearly the sum of the angles 0 and , is A. The clearance between the flight line of the aircraft and the feature X is C and the vertical distance of the aircraft A above the feature
X is h. The range of the feature X from the aircraft A is R.
In the situation in which the use of the invention is envisaged the angles 0, 0 and A will be small, so small angle approximations may be used without introducing undue inaccuracy. Accordingly we may express the angle A as A = h/R.
Differentiating with respect to time and using
Newton’s notation for the differential with respect to time, we may express the rate of change of lv as A = h/RRh/R . Since AH is fixed in direction, being the horizontal, we may write the rate of change of h as h = – Vld. The rate 9f change of R is approximately given by
R = -V. The expression for A can then be simplified to A = Vo/It, which can be rearranged to give R = V0/A. Since the clearance C is approximately given by C = R 0, it follows that C=V02/A.
Figure 2 shows an electro-optical sensor 1, such as low-light television apparatus or infra-red line scan apparatus, connected to a display device 2 so as to give a pictorial display of the terrain ahead of the aircraft. An output from the electro-optical sensor 1, corresponding to the optical intensity of the pictorial display at successive points on a vertical line through the centre of the display, corresponding to features lying substantially in the vertical plane containing the flight line of the aircraft, is applied to a correlator 3. The correlator 3 may be a digital computing circuit programmed to compare the outputs received from the electro-optical sensor
1 at successive instants and to compute there
from the angular velocity 0 of the feature rel ative to the flight line of the aircraft.An output
from the correlator 3 is applied together with an output from aircraft sensors 4 corresponding to the ground speed V and the rate of change Q) of the angle of climb of the aircraft, to a computer 5 which is programmed to compute the ranges and the clearances of the features, to
compute safe clearances Cn of the features according to a predetermined3function of their range R and ground speed V, to compare the calculated clearances C of the features with the
safe clearances CO and to produce preliminary warning signals on the display 2 or warning signals on the display 2 and from an audible warning device 6 whenever the computed clearances of any of the features respectively approach or become less than the corresponding safe clearances.The relationship between the safe clearance C and range R and ground speed V will depend on the known flight characteristics of
the aircraft in which the invention is to be used.
Figure 3 is a flow diagram illustrating the operation of the correlator 3 of Figure 2. The most recent inputs from the electro-optical sensor 1 of Figure 2 are stored in an array AN.
The previous set of inputs is stored in an array
AO. For the purposes of the correlator the optical intensities of points on the display are
quantised into a number of discrete levels.
There may, for example, be eight levels so that the elements in the arrays AN and AO may be three-bit integers. For each point labelled I the
correlator takes a group of points centred on
the point I, namely the points I – K to I + K where K is a predetermined small integer, for example four, and correlates the elements of
AN corresponding to those points with the elements of AO corresponding to a similar group
of points centred on the point I + J, which is displaced by J positions from the point I. This correlation process is repeated for several values of J, namely from – M to M where M is a predetermined small integer whose value depends on the angular resolution of the display and the flight characteristics of the aircraft, and the correlator finds the value JB of J for which the correlation is best. The values of JB for each value of I are stored in an array JJ. The value of
JJ(I) therefore indicates the amount by which the pattern on the display about the point I has been displaced since the previous instant. Since the value of I is proportional to the angle 0 corresponding to a feature shown on the display, the value of JJ(I) is proportional to the rate of change d.
It is therefore possible to calculate an estimate of 9 corresponding to each point I from the displacement JJ and the known time interval between successive instants. Since the elements of JJ are integers they only provide a coarse estimate of the angular displacement of the features qf the landscape, so the estimated values of 9 will be correspondingly coarse. The coarseness can be smoothed by averaging the values of 9 over several successive instants. The correlation of the values of AN at a set of points with the values of AO at a set of corresponding points may be the sum over the set of points of the values of a predetermined correlation function which depends on the difference between the value of AN at a point and the value of AO at the corresponding point.For example the correlation function may be equal to four if the value of AN is equal to the value of AO, equal to two if the value of AN differs by one from the value of AO, equal to one if the value of
AN differs by two from the value of AO, and equal to zero otherwise.
A hardware-implemented correlator cap able of being adapted for use in the present invention is described in British Patent Specification No. 1 409 448.
Figure 4 shows a flow diagram for the computer 5 in Figure 2. The computer takes the points I in turn, and for each point calculates the range R and the clearance C, calculating 9 from I, using the value of the ground speed V from the sensors 4 and using the rate of change ss of the angle of climb as measured by the aircraft sensors 4 of Figure 2 and the values of 9 supplied by the correlator 3 of Figure 2 to calculate t. From the range R and the ground speed V the computer then calculates a safe clearance CO according to a predetermined formula which will be determined by the known characteristics of the aircraft in which the invention is to be used.The computer then calculates a safety margin SM which is the amount by which the clearance exceeds the safe clearance and finds the point ILat which the safety margin takes its lowest value LSM. When all the points have been examined and the values of LSM and
IL have been found the computer then examines the value of LSM. If the value of LSM is less than zero the computer gives a warning indicating the point IL, but if it is greater than zero but less than some predetermined value PSM the computer gives a preliminary warning, also indicating the point IL. The warning may be an audible warning together with a flashing cross on the display 2 of Figure 2 indicating the point
IL.The preliminary warning may be a flashing cross on the display 2 of Figure 2 indicating the point IL, and the frequency of flashing may depend upon the value of the lowest safety margin LSM, with the frequency increasing as
LSM decreases.
A number of modifications will now be apparent to a person skilled in the art to which this invention relates. For example, instead of the correlator 3 and the computer 5 of Figure 2 being physically distinct entities, they may be combined into one computer which is controlled by a program to perform the functions of the correlator 3 and the computer 5.
WHAT I CLAIM IS:
1. An instrument for determining the range
R from an aircraft of a landscape feature lying substantially in the vertical plane containing the flight line of the aircraft, comprising: means for determining 9, the angle below the flight line of the aircraft of a sight line from the aircraft to the feature; means for determining A, the rate of increase of the angle of the sight line below the horizontal; means for determining V, the ground speed of the aircraft; and computing means for computing the range according to the relation R = V 0/A, none of the said means including forward-looking echo-sounding sensors.
2. An instrument for determining the clearance C between the flight line of an aircraft and a landscape feature lying substantially in the vertical plane containing the flight line of the aircraft, comprising: means for determining 6, the angle below the flight line of the aircraft of a sight line from the aircraft to the feature; means for determining A, the rate of increase of the angle of the sight line below the horizontal; means for determining V, the ground speed of the aircraft; and computing means for computing the clearance according to the relation
C = V 92/A, none of the said means including
forward-looking echo-sounding sensors.
3. A flying aid for aircraft comprising: means for determining 9, the angle below the flight line of the aircraft of each of a plurality of sight lines from the aircraft to respective landscape features lying substantially in the vertical plane containing the flight line of the aircraft; means for determining A, the rate of increase of the angle below the horizontal of each of the sight lines; means for determining V, the ground speed of the aircraft; computing means for computing the range R and the clearance C of each of the features accqrding to the relations R = V9/A and C = VS and calculating a safe clearance CO (R) for each of the features according to a predetermined relation; and warning means for giving a warning signal whenever the computed clearance of any of the features is less than the safe clearance, none of the said means including forward-looking echosounding sensors.
4. A flying aid as claimed in Claim 3 wherein the warning means is adapted to give a preliminary waming whenever the computed clearance of any of the features, while being greater than the safe clearance, approaches the safe clearance.
5. A flying aid as claimed in Claim 3 or
Claim 4 associated with an electro-optical sensor for producing a pictorial display of the terrain ahead ofthe aircraft, wherein the warning signal, and, as the case may be, the preliminary warning signal, include a visual signal superimposed on the pictorial display so as to indicate which
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (7)
**WARNING** start of CLMS field may overlap end of DESC **. of 9 corresponding to each point I from the displacement JJ and the known time interval between successive instants. Since the elements of JJ are integers they only provide a coarse estimate of the angular displacement of the features qf the landscape, so the estimated values of 9 will be correspondingly coarse. The coarseness can be smoothed by averaging the values of 9 over several successive instants. The correlation of the values of AN at a set of points with the values of AO at a set of corresponding points may be the sum over the set of points of the values of a predetermined correlation function which depends on the difference between the value of AN at a point and the value of AO at the corresponding point.For example the correlation function may be equal to four if the value of AN is equal to the value of AO, equal to two if the value of AN differs by one from the value of AO, equal to one if the value of AN differs by two from the value of AO, and equal to zero otherwise. A hardware-implemented correlator cap able of being adapted for use in the present invention is described in British Patent Specification No. 1 409 448. Figure 4 shows a flow diagram for the computer 5 in Figure 2. The computer takes the points I in turn, and for each point calculates the range R and the clearance C, calculating 9 from I, using the value of the ground speed V from the sensors 4 and using the rate of change ss of the angle of climb as measured by the aircraft sensors 4 of Figure 2 and the values of 9 supplied by the correlator 3 of Figure 2 to calculate t. From the range R and the ground speed V the computer then calculates a safe clearance CO according to a predetermined formula which will be determined by the known characteristics of the aircraft in which the invention is to be used.The computer then calculates a safety margin SM which is the amount by which the clearance exceeds the safe clearance and finds the point ILat which the safety margin takes its lowest value LSM. When all the points have been examined and the values of LSM and IL have been found the computer then examines the value of LSM. If the value of LSM is less than zero the computer gives a warning indicating the point IL, but if it is greater than zero but less than some predetermined value PSM the computer gives a preliminary warning, also indicating the point IL. The warning may be an audible warning together with a flashing cross on the display 2 of Figure 2 indicating the point IL.The preliminary warning may be a flashing cross on the display 2 of Figure 2 indicating the point IL, and the frequency of flashing may depend upon the value of the lowest safety margin LSM, with the frequency increasing as LSM decreases. A number of modifications will now be apparent to a person skilled in the art to which this invention relates. For example, instead of the correlator 3 and the computer 5 of Figure 2 being physically distinct entities, they may be combined into one computer which is controlled by a program to perform the functions of the correlator 3 and the computer 5. WHAT I CLAIM IS:
1. An instrument for determining the range
R from an aircraft of a landscape feature lying substantially in the vertical plane containing the flight line of the aircraft, comprising: means for determining 9, the angle below the flight line of the aircraft of a sight line from the aircraft to the feature; means for determining A, the rate of increase of the angle of the sight line below the horizontal; means for determining V, the ground speed of the aircraft; and computing means for computing the range according to the relation R = V 0/A, none of the said means including forward-looking echo-sounding sensors.
2. An instrument for determining the clearance C between the flight line of an aircraft and a landscape feature lying substantially in the vertical plane containing the flight line of the aircraft, comprising: means for determining 6, the angle below the flight line of the aircraft of a sight line from the aircraft to the feature; means for determining A, the rate of increase of the angle of the sight line below the horizontal; means for determining V, the ground speed of the aircraft; and computing means for computing the clearance according to the relation
C = V 92/A, none of the said means including
forward-looking echo-sounding sensors.
3. A flying aid for aircraft comprising: means for determining 9, the angle below the flight line of the aircraft of each of a plurality of sight lines from the aircraft to respective landscape features lying substantially in the vertical plane containing the flight line of the aircraft; means for determining A, the rate of increase of the angle below the horizontal of each of the sight lines; means for determining V, the ground speed of the aircraft; computing means for computing the range R and the clearance C of each of the features accqrding to the relations R = V9/A and C = VS and calculating a safe clearance CO (R) for each of the features according to a predetermined relation; and warning means for giving a warning signal whenever the computed clearance of any of the features is less than the safe clearance, none of the said means including forward-looking echosounding sensors.
4. A flying aid as claimed in Claim 3 wherein the warning means is adapted to give a preliminary waming whenever the computed clearance of any of the features, while being greater than the safe clearance, approaches the safe clearance.
5. A flying aid as claimed in Claim 3 or
Claim 4 associated with an electro-optical sensor for producing a pictorial display of the terrain ahead ofthe aircraft, wherein the warning signal, and, as the case may be, the preliminary warning signal, include a visual signal superimposed on the pictorial display so as to indicate which
features are giving rise to the signal.
6. A flying aid substantially as herein described with reference to Figure 2 of the drawings accompanying the provisional specification.
7. A flying aid substantially as herein described with reference to Figure 2 of the drawings accompanying the provisional specification and wherein the correlator and computer are adapted to operate substantially as herein described with reference to Figures 3 and 4 respectively of the drawings accompanying the provisional specification.
GB5368674A
1975-12-05
1975-12-05
Instruments for aircraft
Expired
GB1605171A
(en)
Priority Applications (1)
Application Number
Priority Date
Filing Date
Title
GB5368674A
GB1605171A
(en)
1975-12-05
1975-12-05
Instruments for aircraft
Applications Claiming Priority (1)
Application Number
Priority Date
Filing Date
Title
GB5368674A
GB1605171A
(en)
1975-12-05
1975-12-05
Instruments for aircraft
Publications (1)
Publication Number
Publication Date
GB1605171A
true
GB1605171A
(en)
1982-10-13
Family
ID=10468652
Family Applications (1)
Application Number
Title
Priority Date
Filing Date
GB5368674A
Expired
GB1605171A
(en)
1975-12-05
1975-12-05
Instruments for aircraft
Country Status (1)
Country
Link
GB
(1)
GB1605171A
(en)
Cited By (2)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
FR2639127A1
(en)
*
1988-11-14
1990-05-18
Smiths Industries Plc
APPARATUS FOR ELECTRONIC PROCESSING OF IMAGES FOR DETERMINING THE DISTANCE OR SIZE OF AN OBJECT
GB2233527A
(en)
*
1989-06-23
1991-01-09
Marconi Gec Ltd
Aircraft landing systems
1975
1975-12-05
GB
GB5368674A
patent/GB1605171A/en
not_active
Expired
Cited By (3)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
FR2639127A1
(en)
*
1988-11-14
1990-05-18
Smiths Industries Plc
APPARATUS FOR ELECTRONIC PROCESSING OF IMAGES FOR DETERMINING THE DISTANCE OR SIZE OF AN OBJECT
GB2233527A
(en)
*
1989-06-23
1991-01-09
Marconi Gec Ltd
Aircraft landing systems
GB2233527B
(en)
*
1989-06-23
1993-05-26
Marconi Gec Ltd
Aircraft landing system
Similar Documents
Publication
Publication Date
Title
US3725918A
(en)
1973-04-03
Collision avoidance display apparatus for maneuverable craft
US3815132A
(en)
1974-06-04
Radar for automatic terrain avoidance
US3717873A
(en)
1973-02-20
Ship's maneuver assessment system
EP0882213B1
(en)
2001-12-05
Three-dimensional lateral displacement display
EP0256124B1
(en)
1991-04-17
Wind shear detection and alerting system
US3784969A
(en)
1974-01-08
Aircraft landing display apparatus
CN110221625B
(en)
2021-08-03
Autonomous landing guiding method for precise position of unmanned aerial vehicle
US5382954A
(en)
1995-01-17
Resolution advisory display instrument for TCAS guidance
US4891642A
(en)
1990-01-02
Wind shear detection system
US3982246A
(en)
1976-09-21
General method of geometrical passive ranging
US3680094A
(en)
1972-07-25
Terrain-warning radar system
US3245076A
(en)
1966-04-05
Automatic pilotage system for an aircraft or missile
US9341705B2
(en)
2016-05-17
Passive ranging of a target
US3650627A
(en)
1972-03-21
Measurement of visual range in fog
US4964723A
(en)
1990-10-23
Process and device for detecting the coming interposition of a mask between an aircraft and a target, particularly in a laser-guided weapon firing system
GB1605171A
(en)
1982-10-13
Instruments for aircraft
CA1241082A
(en)
1988-08-23
Warning system for tactical aircraft
US2958135A
(en)
1960-11-01
Collision-course director
US20210199798A1
(en)
2021-07-01
Continuous wave radar terrain prediction method, device, system, and unmanned aerial vehicle
US4325066A
(en)
1982-04-13
Overwater radar navigation system
US3293641A
(en)
1966-12-20
Lateral maneuver indicator
US3371887A
(en)
1968-03-05
Apparatus and method for guiding a first travelling body relative to a second travelling body
RU2316023C2
(en)
2008-01-27
Method for optimal avoidance of thunderstorm
US3906189A
(en)
1975-09-16
Passive range computer
US3355941A
(en)
1967-12-05
Collimated aircraft landing assis system
Legal Events
Date
Code
Title
Description
1983-01-06
PS
Patent sealed
1983-11-02
PCNP
Patent ceased through non-payment of renewal fee
