CH660156A5 - FLOOR PROXIMITY WARNING DEVICE FOR AIRCRAFT TAKING OFF OR MANEUVERING AT LOW ALTITUDE. - Google Patents

Description

The invention relates to a device for warning of proximity to the ground and more particularly to a device for protecting an airplane during maneuvers at low altitude if this airplane descends below a predetermined height above the ground or if its speed of descent exceeds a predetermined value while it makes turns or other maneuvers requiring a lateral inclination. Separate specific warnings may be provided to inform the pilot of the specific actions he must take to escape from a dangerous flight path.

Ground proximity warning devices are known which warn the pilot of dangerous trajectories. These devices warn the pilot of an airplane during the existence of various dangerous flight conditions inclusive under a predetermined minimum altitude which allows the airplane to reach an excessive descent speed after takeoff or during the approach flight. . An example of a device which warns the pilot if he descends below a predetermined minimum altitude is given by a device which compares the radio altitude with a minimum altitude decision value, or even a limit value of the radio altimeter, and which provides an acoustic or visual warning signal if the radio altitude drops below the chosen minimum limit value. U.S. Patent Nos. 3,946,358, 3,947,808, 3,947,810 and 4,319,218 illustrate examples of devices which provide a warning to the pilot during take-off or during a missed approach flight if the aircraft descends at excessive barometric speed or loses a predetermined barometric altitude.

These devices effectively serve to warn the pilot when the airplane descends below a predetermined minimum altitude above the ground, or if the airplane has an excessive descent speed after takeoff or during a missed approach, however, these systems are intended for the front line for transport aircraft that do not normally fly at low altitudes and do not make turns or other abrupt and brutal maneuvers near the ground. Consequently, these devices cannot, as a general rule, provide adequate warnings to the pilot of a highly maneuverable aircraft, for example a fighter or assault aircraft performing tactical maneuvers close to the ground.

It is therefore the object of the invention to provide a warning device which avoids many disadvantages of the above devices5

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also known to maneuver an airplane at high speed and low altitude.

To this end, the invention is defined as stated in claim 1.

The missions of a fighter or assault aircraft include phases of cruises and attacks at low altitude which involve the danger of inadvertently descending to the ground or colliding in low ascending terrain if the pilot is even slightly distracted or disoriented. The danger of hitting in an ascending terrain exists in the first place during takeoff and cruise flight at low altitude. The danger of an inadvertent descent is greatest during low altitude maneuvers requiring large roll angles such as those performed during the attack phase of a flight. Indeed, during such maneuvers the pilot can easily have his attention distracted or be disoriented because an airplane tends to lose altitude when it flies with a large angle of roll.

This is why, in a preferred variant of the invention, the warning device measures the height of the airplane above the ground using a radio altimeter or a similar instrument and emits a specific acoustic warning signal such as "too low" addressed to the pilot if the airplane descends below a certain predetermined minimum height above the ground, thus ensuring protection during cruising flight operations at low altitude . The desired and predetermined minimum height is generally a minimum decision height chosen manually using a minimum decision altitude marker or a “spy” incorporated in the radio altimeter indicator.

In addition, to provide a warning during take-off in ascending terrain or even during an inadvertent loss of altitude before the minimum decision altitude is reached, the device is equipped with an accumulator which monitors the altitude radio after takeoff and memorizes the greatest height reached after takeoff. If the aircraft descends below a predetermined fraction of the maximum radio altitude reached before exceeding the minimum decision altitude, a warning may also be issued. Typically this warning will be the same "too low" signal that is issued when the minimum decision altitude is reached to indicate to the pilot that he is too low.

In addition, the device can monitor the aircraft's roll angle and issue a second specific warning signal if the aircraft is below a second predetermined altitude and descends faster than a rate of descent. predetermined, which varies depending on the roll angle of the airplane to signal the pilot that the airplane descends too quickly during a roll maneuver. The warning signal transmitted must be specific enough to allow the pilot to quickly diagnose the problem, and in the example of embodiment described there is provided a signal of the kind "too much roll".

The invention will now be described by way of example and with the aid of the drawing, in which:

FIG. 1 represents a diagram of a warning device according to the invention;

FIG. 2 represents a graph illustrating the relationships existing between the relative speed and the radio altitude when warning signals are emitted, and FIG. 3 is a graph showing the relationships existing between the speed of change of the barometric altitude and the roll angle when a warning signal is issued to warn that the aircraft is descending at excessive speed during a roll maneuver.

FIG. 1 illustrates an embodiment of a ground proximity warning device produced according to the invention and which is particularly useful for signaling dangerous flight conditions during the execution of low altitude maneuvers; this device is identified by the reference numeral 10. The diagram in FIG. 1 shows an embodiment of the device according to the invention in the form of logic assemblies comprising series of doors, comparators, fiip-fiops, etc .; this is intended to facilitate understanding,

but it should be noted that the practical embodiment of the logic circuits in question may differ from that shown in FIG. 1, different digital or similar embodiments being able to be chosen. The signals used by the warning device described here include signals for the radio altitude, the variation in barometric altitude, the relative speed, the number of revolutions min, the aircraft roll angle, the altitude minimum decision, as well as signals indicating the position of the aircraft landing gear and a certain number of validation signals. Depending on the type of aircraft on which the warning device is installed, the signals shown in FIG. 1 can be obtained from separate instruments such as the barometric altimeter 12, a barometric altitude variation circuit 14, a radio altimeter 16, and a gyrosco-pic platform 18, as well as from various elements of discrete circuits such as a discrete element which indicates the position of the landing gear. In some modern devices, signals can also be obtained from a central data bus.

As mentioned above, the device in question is intended to emit different warning signals in different phases of the flight. Thus, the device is designed to issue a first warning which may, for example, be an acoustic warning of the "too low" type if the aircraft descends below the minimum decision altitude during a cruise flight at low altitude. This warning will also be issued if the aircraft loses a predetermined fraction of the altitude reached after takeoff, and this before reaching the minimum decision altitude. In addition, the device is designed to emit a second specific warning signal, such as for example the acoustic signal "too much roll" if the aircraft loses height too quickly during a roll maneuver. Consequently, logic circuits are provided to inform the system in which particular phase of the flight the aircraft is in, that is to say if it is in the process of takeoff, at low altitude cruise or in maneuver at low altitude, so that an adequate warning is issued if certain flight parameters take excessive values. This function is performed by a logic circuit comprising AND gates 20, 22, 24, 26 and 28, an OR gate 30, a pair of arming / resetting flip-flops 32 and 34, a transition detector 36 and a switch 38 controlled by flip-flop 34.

Since the device is designed to be capable of issuing warnings during takeoff, during low altitude cruising and during maneuvers performed at low altitude, certain information must be gathered to determine whether the aircraft is actually in one of the flight phases mentioned. The initial observations are made by the AND gate 20 which delivers an activation signal to the AND gates 22 and 24 only when certain conditions are met. These conditions require that there be no load on the wheels, to indicate that the airplane is actually in flight, that the landing gear is raised and that the airplane is not flying at less than 200 knots (360 km h), indicating that the aircraft is not landing. For the device to be activated, the barometric altimeter 12, the barometric variation circuit 14 and the radio altimeter must also function correctly. Consequently, signals indicating that the barometric altimeter and the radio altimeter have not been deactivated, as well as a signal indicating that the variation in radio altitude is not excessive, are applied to gate 20 for cause this door 20 to activate doors 22 and 24 only if the signals emitted by the barometric altimeter 12, the barometric variation circuit 14 and the radio altimeter 16 are valid.

In addition to the check to determine if the aircraft is in a phase of flight other than landing and if the instruments are functioning correctly, it is necessary to determine whether the aircraft is in an approach phase or in the process of take-off or on a runway lap after a missed approach. This determination is carried out by the AND gates 26 and 28, the OR gate 30 and the arming / resetting flip-flop 32. In the described embodiment, a takeoff or a runway runway after a missed approach is only noted if the takeoff power is developed and that if the landing gear

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is raised. If these two conditions are met, the arming / resetting flip-flop 32 is reset. The signals applied to gate 26 and indicating that takeoff power is present can be obtained from different sources, for example from a comparison circuit which delivers an activation signal to gate 26 when the number of turns / engine min is high enough to indicate take-off power, or from a discrete item indicating the position of the throttle. A tachometer indicating for example the number of revolutions of the compressor of a jet can be used to provide a signal indicating the number of revolutions / min of the engine and a predetermined number of revolutions / min, for example 90% of that corresponding to the power maximum, can be used to indicate that take-off power is present. The signal indicating that the landing gear is raised can be easily obtained from a discrete element, for example a switch actuated by the landing gear or by the control lever of the landing gear located in the cockpit.

Conditions identifying an approach flight are indicated by gates 30 and 28 when the train is not raised or the airplane is below 100 feet (30 m) and the engine does not develop power takeoff and the airplane speed is less than 200 knots (360 km / h). The indication of an approach phase by the gate 28 is used to arm the flip-flop 32.

During operation, and during the takeoff phase of the flight, the arming / resetting flip-flop 32 is reset and the output signal Q of the flip-flop 32 is thus brought to pass from a high value to a low value . This transition is detected by the transition detector 36 which, in response to this transition, produces an output pulse and arms, a flip-flop 34 with arming / rearming. This causes the output signal Q of the flip-flop 34 to put the switch 38 in the position shown in FIG. 1, which connects an input of the gate 22 to a circuit comprising a comparator 40, a normalization circuit 42 and a radio altitude accumulator 44. These elements determine when a generator 46 must emit a warning signal of the “too low” type during the take-off phase.

When the aircraft has completed takeoff, which is observed when the radio altitude exceeds a minimum decision altitude (AMD), an AMD 50 comparator delivers a signal indicating that the aircraft has exceeded the minimum decision altitude in order to to reset the input of the flip-flop 34, thus to rearm the flip-flop 34. When the flip-flop 34 is reset, the switch 38 is operated to separate the gate 22 from the comparator 40 and connect it to an output LESS THAN AMD of the AMD 50 comparator. This means that the device will be activated by any descent below the minimum decision altitude. Consequently, if in this flight phase the aircraft descends below the minimum decision altitude, the warning generator 46 will emit a warning signal "too low" and will apply it to the transducer 48.

As long as the aircraft altitude is lower than the minimum decision altitude plus a predetermined value which can be for example 100 feet (30 m), but not below the minimum decision altitude, the door ET 24 will be activated by comparator 50 by means of the signals MORE THAN AMD and LESS THAN AMD PLUS 100 FEET which are applied to two of its inputs. When the AND gate 24 is thus activated, it reacts to a pair of comparators 52 and 54 to activate a second warning generator 56 which produces a second warning signal of the “too much roll” type when the descent speed of l airplane exceeds a predetermined value for a given roll angle.

The mode of operation will now be described in more detail. When the plane takes off, the flip-flop 32 is reset, which causes the transition detector 36 to provide an output pulse to arm the flip-flop 34 in order to connect the gate 22 to the comparator. 40. The output pulse from the transition detector 36 also resets the radio altitude accumulator to zero or to a predetermined low value, for example at 50 feet (15 m). The radio altitude accumulator receives altitude signals from the radio altimeter 16 and stores the highest altitude reached since takeoff. This maximum radio altitude value reached since takeoff is applied to a normalization circuit which multiplies by a normalization factor, for example by 75%, and applies signals to the comparator 40, which controls the warning generator 46 of height too low during takeoff phase.

The signal from the radio altimeter is also applied to the comparator 40, and as long as the radio altitude remains above the maximum radio altitude multiplied by the normalization factor, no warning will be issued. If however the radio altitude falls below the reduced maximum altitude, for example less than 75% of the highest altitude reached during the flight, then the comparator 40 will deliver a signal to gate 22. This signal will bring the gate 22 to deliver a signal to the warning generator 46 "too low" and is will cause this generator 46 to issue a warning "too low" and to apply this signal, either directly or indirectly, to the transducer 48, provided that the other input of door 22 is activated by door 20.

The radio altitude signal from the altimeter 16 is also applied to the AMD comparator 50 which monitors the radio altitude signal from the radio altimeter 16 and delivers a signal MORE THAN AMD to the flip-flop 34 when the radio altitude exceeds the minimum decision altitude. This signal rearms the flip-flop 34 and causes the switch 38 to connect the gate 22 to the AMD comparator 50 so that any warning produced is controlled by the AMD comparator 50. The AMD comparator 50 continues to monitor the radio altitude, and no warning signal will be produced as long as the radio altitude remains above the minimum decision altitude. If, however, the altitude falls below the minimum decision altitude 30 and if door 22 is activated by door 20, the AMD comparator will provide door 22 with a LESS AMD signal in order to bring door 22 to trigger the warning signal “too low” by the warning generator 46.

When the airplane rises above the minimum decision altitude, but remains below the minimum decision altitude plus a predetermined value of 30 m for example, and as long as the gate 20 produces an activation signal, the door 24 will be under the control of a roll comparator 52 and a roll angle comparator 54. The function of the comparators 52 and 54 is to monitor the angle of 40 roll and the barometric descent speed of the airplane, and causing the door 24 to trigger a warning emitted by the warning signal generator 56 when a dangerous combination of descent speed and roll angle is observed.

As mentioned above, airplanes tend to descend 45 as the roll angle increases. However, this trend is not marked until the roll angle exceeds a predetermined value, which will for example be 45 ° for a modern fighter and assault aircraft, such as the Fairchild AIO. Consequently, the roll angle comparator 54 monitors the roll signal produced by the gyroscopic platform 18 or by a similar element indicating the roll angle of the aircraft. The roll angle comparator 54 will deliver an activation signal to gate 24 when the roll angle reaches a value from which the aircraft tends to descend. This allows the generator 56 to produce a “too 55 roll” warning signal if the barometric descent speed exceeds the maximum speed allowed for a given roll angle, which is controlled by the roll comparator 52. The necessary conditions for producing a "too much roll" warning signal are discussed in more detail in connection with Figure 3.

60 Figure 2 shows a graph illustrating the conditions required to produce the “too low” warning and to activate the “too much roll” warning as a function of true speed and altitude. These conditions are illustrated by the two openwork regions on the graph. As shown in Figure 2, neither of the 65 warnings can be issued as long as the true speed ("relative speed") of the aircraft is less than a predetermined value, which in the example described is 200 knots ( 360 km / h). As long as the relative speed of the aircraft exceeds 200 knots (360 km / h) and the

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other conditions considered above are met, the warning "too low" will be given as soon as the aircraft descends below the minimum decision altitude, or below a given fraction, for example less than 75 %, of the maximum altitude reached during takeoff or a runway before exceeding the minimum decision altitude.

When the aircraft altitude exceeds the minimum decision altitude, but remains below the minimum decision altitude plus a predetermined value which can be for example 100 feet (30 m), the warning "too "will be activated. However, the warning "too much roll" is not automatically produced when the limits of the region "too much roll" illustrated in FIG. 2 are reached, as is the case when the limits of the region d 'too low' warning are reached. On the contrary, the "too much roll" warning mode is only activated, but a warning will only be effectively issued if the roll angle exceeds

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a predetermined angle, for example 45, and if the descent speed crosses the limit of the descent speed curve (fig. 3) which defines the maximum allowed descent speed as a function of the roll angle.

Figure 3 illustrates a descent speed curve particularly suitable for use in fighter and assault aircraft. The perforated surface shows the relationship that should exist between the roll angle and the barometric descent speed to produce a "too much roll" warning. It follows from Figure 3 that the warning "too much roll" will not be produced before the roll angle reaches 45, and that at this time the warning "too much roll" will be produced if the speed barometric descent exceeds 30 m min. If the roll angle goes up to 60, a descent speed of 50 feet / min will suffice to produce a warning and, if the roll angle reaches 90, no descent is tolerated because, in these conditions, the lift due to the wings practically disappears.

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2 sheets of drawings

Claims (20)

660,156 2 1. Warning device to alert the pilot of an airplane to the existence of dangerous flight conditions after takeoff and during low altitude maneuvers, comprising means for monitoring the height of the airplane above the ground and to produce a signal representing this altitude, characterized by (a) means for storing an indication of the greatest height above the ground reached during the flight; (b) means for selecting a desired minimum height above the ground; and (c) means reacting to the signal representing the height of the airplane above the ground and to the storage means, to produce a first warning as a function of the means for selecting a minimum height if the airplane has reached that -this, or according to the greatest height reached during the flight if the airplane has not yet reached the minimum desired altitude. 2. Device according to claim 1, characterized by (a) means reacting to a signal representing the power developed by the engine; (b) means for producing a signal representing the position of the landing gear; and (c) means for expressing the function of the greatest height above the ground as a percentage of this height upon receipt of a signal that the train is raised and a signal that the engine is developing at least take-off power. 3. Device according to claim 1, characterized by (a) means for producing a signal representing the roll angle of the aircraft; (b) means representing the descent speed of the aircraft; and (c) means for producing a separate second warning above the minimum height, based on the signals representing the roll angle and the descent speed respectively. 4. Device according to claim 3, characterized by means for activating the means producing the second warning only when the roll angle exceeds a determined value. 5. Device according to claim 3, characterized in that the means for producing the first warning are activated if the aircraft descends below the desired minimum altitude after reaching it. 6. Device according to claim 3, characterized by means for preventing the production of a warning when the descent speed of the aircraft exceeds a predetermined value. 7. Device according to claim 1, characterized by means for producing this function of the maximum altitude above the ground in the form of a predetermined fraction of the percentage of the highest altitude reached since takeoff., 8. Device according to claim 1, characterized by manual means for selecting said minimum height above the ground. 9. Device according to claim 8, characterized in that the means for producing a first warning are arranged so as to be activated if the airplane descends below a predetermined percentage of the greatest altitude reached, before having reached the minimum height selected manually. 10. Device according to claim 8, characterized in that the means for producing a first warning are arranged so as to be activated if the aircraft descends below the height selected manually after having exceeded it. 11. Device according to claim 3, characterized in that the means for producing the second warning emit the latter in an altitude interval greater than that in which the first warning is produced. 12. Device according to claim 4, characterized in that it is arranged to produce the second warning when the roll angle of the aircraft exceeds 45 °. 13. Device according to claim 9, characterized in that said predetermined percentage of the highest altitude reached is approximately 75% of the height above the ground reached during the flight. 14. Device according to claim 3, characterized by means for activating the means producing the second warning only below a second altitude and above the minimum altitude. 15. Device according to claim 3, characterized in that said warning is produced when the roll angle exceeds 453 and the descent speed exceeds 100 feet / min. 16. Device according to claim 3, characterized in that said warning is produced when the roll angle exceeds 60 ° and the descent speed exceeds 50 feet / min. 17. Device according to claim 3, characterized in that said warning is produced when the roll angle exceeds 90th and the descent speed exceeds the value of zero. 18. Device according to claim 3, characterized in that said value of the descent speed is an inverse function of the roll angle. 19. Device according to claim 3, characterized by (a) means for supplying a signal representing the true speed of the airplane, and (b) means for activating the means producing the first and second warning only if the true speed exceeds a determined value. 20. Device according to claim 3, characterized by means reacting to the signal representing the height above the ground and arranged to prevent the production of the second warning when the altitude of the aircraft exceeds a given value.