DE3639398C1 - Arrangement for determining the wind gradient on board an aircraft - Google Patents

Abstract

It is intended to specify an arrangement for determining the wind gradient on board an aircraft. The arrangement can be used for aeroplanes and gliders. The air speed indicator signal on board an aircraft is measured using a pressure probe, such as a pitot tube. In this case, changes in the wind pattern (which varies with position and in time) caused by gusts and wind shear are also measured. It is intended to produce a signal for the wind gradient, without using an inertia platform. For this purpose, a second pressure probe is fitted in the direction of flight, spaced apart from the first pressure probe, and a signal for the wind gradient is calculated from the difference between the two probe pressures. The arrangement is used together with wind shear instruments and warning apparatuses and in total-energy variometers in gliding.

Description

The invention relates to an arrangement for Determination of the wind gradient on board an aircraft according to the preamble of claim 1.

To measure the journey on board an aircraft Usually a pitot tube is used. That from the Measurement signal derived speed signal for the journey refers to the air speed versus that Plane. On the one hand, it changes when the plane accelerated or decelerated, on the other hand if the air mass flown through the wind speed or Wind direction changes. This change in wind speed (Wind gradient, shear wind, gust) can be dangerous Flight conditions result when an aircraft approaches during the descent with relatively little change in Air masses fly through, their speed and / or direction of movement are clearly different. In Commercial aircraft are used to monitor the horizontal Scherwindes information and warning devices for the pilot intended.

In a system for determining the wind gradient (DE-PS 31 45 389) it is assumed that the horizontal Scherwind from the difference of the time derivative the ride  and the background acceleration ^k =b _k   is calculated. Instead of the time derivative of the trip is to be calculated for a warning device version the trip meter signal passed through a high-pass filter (Aviation Week & Space Technology, Sept. 22, 1986, pg. 78).  

Both methods of signal processing are difficult to master. A spatial acceleration measurement is required to determine the background acceleration b _k . This requires complex devices that are not suitable for light aircraft and gliders due to their weight and price.

In gliding, the desire for availability is one Wind gradient signal has already been discussed. That in Glider used display device for energy change, the so-called total energy variometer, is currently the Determination of the kinetic energy of the aircraft with the Driving signal operated. So there are also energy changes displayed that is not based on an acceleration of the Airplane based, but on a local and / or time-dependent wind change of the air masses flown through. At Knowing the wind gradient could reduce aircraft energy in a reference system adjusted for wind changes (gusts) determined and displayed.

The object of the invention is an arrangement according to further develop the preamble of claim 1, that with little technical effort a signal for Change in wind speed (wind gradient) determined can be. The arrangement is also intended for gliding be usable. In particular, a differentiation of the trip meter signal can be avoided.

This object is achieved with those specified in claim 1 characteristic features solved.

Advantageous configurations and applications of the arrangement according to claim 1 are laid down in subclaims.  

In an expedient embodiment, the aim is that both pressure probes are the same at the same dynamic pressure Deliver pressure readings. This is most likely the case if both pressure probes are in largely undisturbed flow be attached. The rear or the front pressure probe, carried by a towing probe, deliver measured values outside the flow field of the aircraft. To achieve a balanced differential pressure measurement it may be appropriate to insert additional pressure probes in Longitudinal offset or largely side by side to attach. To obtain the required pressure measurements different types of probes, such as Venturi, Hot wire or cylindrical probes can be used. It It is also sufficient to place pressure on the aircraft, depending on the location to measure the kinetic pressure in any way and is therefore dependent on the journey. To the results and display of the measuring pressures are pressure gauges or after Conversion into electrical signals electrical devices suitable.

The device known as the total energy variometer is taken into account the potential energy of the aircraft in the form of a Measured value for the static pressurep _s  and the kinetic Energy in the form of kinetic pressure and represents the time derivative of the sum of both energy components a display device. With knowledge of the wind gradient _W  can be due to gusts or wind Energy change shown in the airplane or from Total energy variometer signal to be subtracted. By Integration of the wind gradient _W  over time it will Wind speed signalV _W  for the total energy variometer available. The part based on gusts can be of the total energy and in the variometer input signal take into account before deriving the time of the total energy signal thus obtained is formed.  

Due to the wind speed V _W , the aircraft is accelerated or decelerated in relation to the reference system, which is in the middle wind. In the case of shear wind warning devices, this acceleration is usually measured using an inertial platform. Such a complex device is not available for gliding. However, from the signal for V _W , knowing the aircraft performance and the current aircraft configuration, a value for the aircraft acceleration b _W in the flight direction can be determined at least roughly. This acceleration counteracts the wind speed V _W and increases the aircraft speed - albeit with a comparatively large time constant. The signal for V _W can thus be corrected, the reduction in the signal V _W having to result in an increase in the signal for the mean aircraft speed V _m . The reference system, which is located in the middle wind, is also computationally tracked to the on-board reference system, although the time constant is large compared to the time constant of the gust speed (low-pass effect).

In the following the invention is based on an embodiment described for example.

The measurement pressure p _DV ( p _DH ) can be obtained with the dynamic pressure probe at the front (rear) in the direction of flight. In unaccelerated flight, both pressures should be the same. If the aircraft is accelerated as a whole in gust-free air, both probes will deliver the same pressures - increasing over time. If a gust hits the aircraft, ie if the speed of the air flown increases quickly enough, the front probe will register a pressure increase first and only after a certain time Δ T later the rear probe. At least during this period, a differential pressure measured _value Δ p _D can be derived from the pressures p _DV and p _DH . Pressure transducers or flowmeters are suitable for this. Electrical transducers are particularly suitable for measuring and transmitting the pressures or the differential pressure measured value.

The pressure p _DV ( p _DH ) of the front (rear) probe includes the run V _V ( V _H ).

The following applies to the differential pressure measurement

Mean

p air density. V _mean mean of V _V and V _H. Δ V _W is the difference in the travel measurable with the front and rear probe.

This difference Δ V _W is returned to effective in the direction of the trajectory gust or a heavy wind component. If the distance between the two nozzles L and the running speed of the air masses between the nozzles V _medium , it takes time Δ T until the air masses measured at the front nozzle arrive at the rear nozzle and are measurable.

V _medium = L / Δ T (2)

By inserting you get

Δ p _D = - ρ L Δ V _W / Δ T (3)

After the transition from the differential quotient Δ V _W / Δ T to the differential quotient d V _W / d t , the equation is

According to this equation, the differential pressure measured value Δ p _D (t) a signal for the wind gradient _W   derived. _W  can be supplied to an integration device be a wind speed signalV _W  to obtain.

Use with the total energy variometer

The total energy variometer (Total Energy Compensated, TEK) commonly used today usually assumes a Venturi pressure (nozzle coefficient equal to one):

The variometer signal is obtained from this by derivation over time. The speed-dependent term can also be measured using a pitot tube and introduced into the variometer system. In electrical devices, the static pressure is often measured and differentiated directly. The known apparatus (TEK) used to construct the energy of the aircraft journey V. The intention, however, is a medium-sized aircraft velocity V _m to use that is different to the wind speed V _W of the drive V.

V _m = V + V _W (7)

This gust-adjusted mean wind speed is to be introduced into the system using the relationship for V _W (t) according to equation (5).

A total energy compensated (TEK) variometer with gust correction (it should be called TEKB here) would have to differentiate and display the pressure value p _{TEKB over} time.

A comparison with the relationship (6) shows which quantities have to be introduced in addition to those usual for total energy compensation (TEK) .

The variometer signal (TEKB) results from the differentiation of p _{TEKB over} time. To this end, the individual terms can of course also be differentiated individually, and appropriate simplifications or neglections can be provided.

The display signal / TEKB / reads:

/ TEKB / = _s  -ρ (V +V _W ) ( + _W )      (9)

In this representation of the display signal, the signal For _W  according to equation (4) and the signal forV _W   be introduced according to equation (5).

Approximately, a signal forV _W  also by suitable Filter the value for _W  respectivelyΔ p _D   be determined. It is also conceivable in the equation (9)V _W  neglect accordingly

/ TEKB / ≈  -ρ V -ρ V _W       (10)

or

/ TEKB / ≈ / TEK / - p V _W (11)

An adaptation to the respective aircraft is only necessary to the extent that the distance between the two measuring nozzles (pitot tubes) differs. The choice of a small distance L between the measuring nozzles leads to small pressure differences, but also makes it possible to measure higher-frequency components of the gust spectrum.

Claims (12)

1. Arrangement for determining the wind gradient (Shear wind and / or gust) on board an aircraft, in particular of an airplane or glider, from which Measurement signal for the journey, which is carried out by means of a pressure probe, such as B. a Pitot tube or a Venturi nozzle, is measured, a signal for the wind gradient is derived becomes,characterized,
that a second pressure probe in the direction of flight is attached at a distance from the first pressure probe,
that from the pressure reading (p _DV ) the first and the Pressure reading (p _DH ) of the second probe Differential pressure measurement (Δ p _D ) is formed and
that from the differential pressure measurement (Δ p _D ) a signal for the wind gradient ( _W ) is derived. 2. Arrangement according to claim 1, characterized in that the differential pressure measurement value ( Δ p _D ) is formed from both pressure measurement values and is converted into an electrical signal. 3. Arrangement according to claim 1, characterized in that both pressure readings are converted into electrical signals and an electrical differential pressure signal is formed.   4. Arrangement according to one of the preceding claims, characterized in that from the differential pressure measurement derived wind gradient ( _W ) on the plane is displayed and / or recorded and / or to a Ground position is transmitted. 5. Arrangement according to one of the preceding claims, characterized in that when a Limit value for the wind gradient ( _W ) a warning signal generator is activated. 6. Arrangement according to one of the preceding claims, characterized in that the differential pressure measured value ( Δ p _D ) is fed to a device for integration over time and a wind speed signal ( V _W ) is formed. 7. Arrangement according to claim 6, characterized in that the wind speed signal ( V _W ) is added to the measurement signal for the journey (V) and the sum signal is shown as the mean aircraft speed ( V _m ) by a display device. 8. Arrangement according to claim 6 or 7, characterized in that a signal for the acceleration acting on the aircraft ( b _W ) is derived from the wind speed signal ( V _W ) and a flight path and airspeed computer is supplied. 9. Arrangement according to claim 8, characterized in that from the acceleration signal (b _W ) a change signal for the average aircraft speed ( _W ) is derived.   10. The arrangement according to claim 9, characterized in that the acceleration signal ( b _W ) is supplied to a device for integration over time and the wind speed signal ( V _W ) is reduced with the signal thus obtained. 11. Arrangement according to one of the preceding claims, characterized in that a total energy variometer the measurement signal for the journey(V), the wind speed signal (V _W ) and / or the signal for the wind gradient ( _W ) and a measurement signal for the static pressure (p _s ) fed and the determined total energy change of the aircraft is displayed on the display of the variometer. 12. The arrangement according to one of claims 7 to 11, characterized in that an overall energy variometer, the signal for the average aircraft speed ( V _m ) and a measurement signal for the static pressure ( p _s ) are supplied and the determined total energy change of the aircraft on the display device of the Variometers is displayed.