Radar-based terrain awareness warning system attenuation alert

The present disclosure is directed to systems and methods for providing attenuation alerts for a radar-based terrain warning.A method for providing radar-based terrain warning attenuation alerts may comprise: (a) receiving a radar return; (b) detecting a region of atmospheric disturbance limiting the range of the radar return; and (c) providing a notification of radar-based terrain awareness warning system attenuation in the region of atmospheric disturbance.

BACKGROUND

Terrain awareness systems, such as Terrain Awareness Warning Systems (TAWS), typically provide flight crews with information (e.g., alerts, warnings, displays of terrain data, etc.) related to detection of potentially hazardous terrain situations that pose or may pose a threat to the continued safe flight and landing of an aircraft and provide warnings or alerts in sufficient time for the flight crew to take effective action to prevent a controlled flight into terrain (CFIT). Terrain awareness systems generally have three alerting functions including a Ground Proximity Warning System (GPWS) alerting function, a Forward Looking Terrain Avoidance (FLTA) alerting function, and a Premature Descent Alerting (PDA) function.

Although the GPWS and TAWS have greatly reduced the controlled flight into terrain risk for aviation worldwide, both GPWS and TAWS have limitations. Neither of these systems detects the terrain or other obstructions ahead of the aircraft.

Instead, GPWS may differentiate the aircraft's altitude signals to detect abnormally high closure rates with terrain. However, highly discontinuous terrain profiles, such as a cliff, may not generate an alert in sufficient time to prevent an accident. In addition, non-fixed terrain features and non-fixed terrain threats such as, for example, aircraft or vehicular traffic on the runway, are also not readily determinable by typical ground proximity warning systems.

Similarly, the “look ahead” function of TAWS compares aircraft position data, based on a stored terrain map to calculate the aircraft's probable position relative to the terrain and determine whether a terrain collision threat exists. However, this system cannot detect collision threats due to obstructions not contained within the database (e.g. a construction crane). In addition, the integrity of the TAWS depends directly upon the integrity of the aircraft position data. Errors in aircraft position could reduce the warning time given the flight crew.

An alternative means of compliance with the FAA TAWS forward looking terrain alerting function requirements (which are currently defined in FAA Technical Standard Order ISO C115b) is a Radar-based TAWS (R-TAWS). Such a system uses airborne radar sensors (e.g., similar to the radar that is used for weather and wind shear detection) to detect terrain and/or obstacles that are potentially hazardous to the aircraft rather than or in addition to using a database.

However, the efficacy of an R-TAWS system may be impacted by the presence of intervening weather between an aircraft and a terrain obstacle. As such, it may be desirable to provide an R-TAWS attenuation alert.

SUMMARY

The present disclosure is directed to a method and system for providing an R-TAWS attenuation alert.

A method for providing radar-based terrain warning attenuation alerts may comprise: (a) receiving a radar return; (b) detecting a region of atmospheric disturbance limiting the range of the radar return; and (c) providing a notification of radar-based terrain awareness warning system attenuation in the region of atmospheric disturbance.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the claims. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate examples and together with the general description, serve to explain the principles of the disclosure.

DETAILED DESCRIPTION

Referring toFIG. 1, an aircraft100includes an aircraft cone section102, which includes a terrain awareness system, such as an R-TAWS200. According to one exemplary embodiment, R-TAWS200may utilize a broad band directional receiver and active radar for detection of terrain and/or obstacles, for example terrain110. The terrain110may include a tower, for example a radio tower, a television tower, a cellular phone tower, a bridge, a building, or any other structure have sufficient height to intersect a flight path of aircraft100. The R-TAWS200may be configured to detect multiple obstacles or terrain features.

R-TAWS200may be configured to transmit a first radio frequency signal106in a predetermined pattern. The first radio frequency signal106may reflect off terrain110to become a second radio frequency signal108. The second radio frequency signal108may be detected by R-TAWS200.

Either the first radio frequency signal106or the second radio frequency signal108may be subjected to an intervening region of atmospheric disturbance112(e.g. precipitation, airborne particulates, and the like) which may interfere with accurate broadcast and/or reception of either the first radio frequency signal106or the second radio frequency signal108

Referring toFIG. 2, aircraft100may include a weather radar system210, and a radar based terrain warning system (e.g., R-TAWS200). The weather radar system210may include an antenna system220capable of casting a radar beam(s) and receiving reflective energy from weather systems, terrain, and other obstacles.

The weather radar system210may be similar to the system described in U.S. Pat. No. 6,388,608, incorporated by reference herein in its entirety. Alternately, the weather radar system210may be a radar-based wind shear detection system or a monopulse radar system. The weather radar system210may be capable of providing terrain elevation estimates or data the R-TAWS200. According to one embodiment, the terrain elevation estimates are provided real time or almost real time as aircraft100is operated.

The weather radar system210may include a transceiver circuit211and a processor212. The weather radar system210may be coupled to display230which can be a multi-function flight display, a dedicated display, or any type of visual indicator and/or an audio system240, such as a speaker system.

The R-TAWS200may include a processor201, a terrain database202and an aircraft position module203.

The weather radar system210may be configured to provide terrain elevation data to the R-TAWS200which may, in turn provide terrain warnings or terrain avoidance instructions via display230and/or audio system240.

Although the R-TAWS200and weather radar system210are shown as distinct systems, they may be provided as a single system or as parts of other distributed systems or other electronics associated with aircraft100.

The processor201of the R-TAWS200may utilize any number of techniques for determining or generating terrain elevation estimates. For example, processor201may be configured to have weather radar system210provide multiple beams swept in azimuth that have different beam elevations. The multiple beams may be used to determine an angle to terrain110using the difference in return power to estimate the target angle within the beam. Using the range with both this intra-beam angle and the beam's center angle, the altitude of the terrain110can be determined relative to the altitude of aircraft100provided by the aircraft position module203.

In yet another example, antenna system220can be controlled in a single azimuth sweep while the data used to support terrain height estimation is taken with either a vertical monopulse antenna (not shown) or vertically orientated sequential lobed antenna (not shown).

In yet another example, the antenna system220may employ vertically swept beams using monopulse antennas and receivers to create terrain data or estimates.

The processor201of the R-TAWS200may receive altitude information from aircraft position module203to determine the elevation of the terrain, obstacle or feature of the terrain. The aircraft position module203can be a GPS system, an altimeter, radar altimeter, etc.

The processor201of the R-TAWS200may include a weather detection module204for determining the presence of weather in response to weather radar returns and a terrain detection module205for determining the presence of terrain and obstacles in response to weather radar returns. The weather detection module204and terrain detection module205may operate in conjunction with weather radar system210. R-TAWS200may alternate between weather detection and terrain detection during flight of aircraft100or utilize antenna/transmitter pulse patterns that may be used for both weather and terrain detection functions. Dual pulse patterns may reduce the total number of antenna sweeps needed to collect the different kinds of needed data (e.g., for wind shear, weather, terrain, obstacle, and runway confirmation).

The R-TAWS200may distinguish data that is related to weather detected by weather radar system210. The R-TAWS200may filters or subtracts out returns from the terrain elevation estimates that are associated with weather features but not with terrain features.

For example, an estimated altitude of the feature associated with the weather radar returns can be compared to data maintained in the terrain database202to determine if it is weather or terrain feature (e.g., a feature at an unusually high altitude in a known planar region is more likely to be weather than terrain.) R-TAWS200can be configured to ignore a feature if its height is well above known parameters (e.g., height is above an error factor for the region).

Alternatively, other radar features and signatures can be utilized to determine whether the return is associated with terrain. Doppler conditions can be monitored to detect movement. Doppler mean frequencies can be estimated from radar return data. The difference between the estimated ground modeled Doppler and the radar derived target estimated Doppler frequency may be used to separate ground returns from weather returns. Alternatively, the radar data may be filtered in the frequency domain to reject weather information.

However, it may be the case that a region of atmospheric disturbance112may be of such a degree that the abilities of the R-TAWS200to distinguish between terrain and weather are attenuated.

FIG. 3illustrates an operational flow300representing example operations related to providing notification of an attenuation of the R-TAWS200. InFIG. 3and in following figures that include various examples of operational flows, discussion and explanation may be provided with respect to the above-described examples ofFIGS. 1 and 2, and/or with respect to other examples and contexts. However, it should be understood that the operational flows may be executed in a number of other environments and contexts, and/or in modified versions ofFIGS. 1 and 2. Also, although the various operational flows are presented in the sequence(s) illustrated, it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently.

After a start operation, operation310depicts receiving a radar return. For example, as shown inFIGS. 1 and 2, weather radar system210may receive a radar return comprising radio frequency signals108via antenna system220.

Operation320depicts detecting a region of atmospheric disturbance limiting the range of the radar return. For example, the weather radar system210may provide radar return data to the R-TAWS200. The R-TAWS200may detect that the radar return data indicates a region of atmospheric disturbance112which may be attenuate future radar returns beyond a threshold level at which the returns are insufficient for the R-TAWS200to provide adequate warning regarding any terrain110which may be obscured by the region of atmospheric disturbance112. For example, R-TAWS200may maintain a defined threshold distance (e.g. 10 miles) or variable threshold distance (e.g. a function of the speed of the aircraft100) whereby the terrain110may safely navigate around terrain110. Radar return data indicating that the region of atmospheric disturbance112will attenuate the range of the R-TAWS200to less than the threshold distance may indicate an area requiring enhanced vigilance by a pilot or altering the course for the aircraft100. It should be noted that the use of distance as a threshold value is merely exemplary and one skilled in the art will recognize that various other values may be employed in determining radar range limitation.

Operation330depicts presenting a notification of radar-based terrain awareness warning system attenuation. Should the R-TAWS200receive radar return data indicating that the region of atmospheric disturbance112will limit the range of the R-TAWS200to less than the threshold value, the R-TAWS200may provide a notification to a pilot that the R-TAWS200will not be functional in a given geographic area due to the region of atmospheric disturbance112.

Referring toFIG. 4, operation410depicts presenting a visual notification. For example, the R-TAWS200may provide a notification via display230. The notification may be in the form of an alert LED, a textual or graphical representation, or any other viewable format.

Operation420depicts presenting an audio notification. For example, R-TAWS200may provide a notification via audio system240. The notification may be in the form an alert signal, spoken instructions or any other audible format.

Referring toFIG. 5, operation510depicts presenting a stored terrain representation of a geographic location associated with the region of atmospheric disturbance. For example, if the R-TAWS200detects that it may become non-functional due to attenuated radar returns resulting from the region of atmospheric disturbance112, the R-TAWS200may provide an alternate mechanism of terrain awareness warning, such as a graphical representation of the topographical features of the surrounding terrain110. Particularly, the R-TAWS200may compute the location of the region of atmospheric disturbance112by correlating the radar returns to a present location of aircraft100as determined by the aircraft position module203. The R-TAWS200may then retrieve stored terrain data from the terrain database202which may be provided to the pilot (e.g. as an overlay to an existing flight status display or as an independent portion of a multi-function display) to allow a degree of terrain awareness in the absence of the radar based functionality of the R-TAWS200.