Systems and methods for reducing nuisance alerts for helicopter enhanced ground proximity warning systems

Current helicopter Enhanced Ground Proximity Warning System (EGPWS) look-ahead functionality is deactivated at or below 70 kts aircraft speed to reduce the number of nuisance alerts during takeoff and landing. However, the best rate of climb speed for many helicopters is at an air speed of less than 70 kts, which means during an escape maneuver at the best rate of climb speed, the helicopter EGPWS may not be activated.

US-A-4551723 and US-A-4980684 both disclose systems for enhancing ground proximity warning systems.

Therefore, there exists a need for an improved cutoff method to provide more protection at low speed while still preventing nuisance alerts.

The present invention provides a method for controlling activation of a look-ahead function of a terrain alert and warning system, the method comprising:

• receiving aircraft rate of climb and aircraft speed information;
• comparing the rate of climb and aircraft speed information to a threshold defined by any aircraft speed greater than a threshold aircraft speed and a rate of climb that is greater than at least one of a straight sloped line or a curve defined by a first rate of climb at 0 kts aircraft speed and a second, different, rate of climb at the threshold aircraft speed; and
• setting an operating state of a look-ahead function based on the comparison.

IN THE DRAWINGS

Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings:

FIGURE 1 illustrates a schematic block diagram of an example system formed in accordance with an embodiment of the present invention;

FIGURE 2 illustrates an example process performed by one or more components of the system shown in FIGURE 1; and

FIGURES 3 and 4 illustrate example threshold graphs as used during a comparison step of the example process shown in FIGURE 2.

FIGURE 1 illustrates an example system 22 embodied within a rotary wing aircraft 20 for improving the effectiveness of a look-ahead function of an Enhanced Ground Proximity Warning System (EGPWS). The system 22 includes a processor 24, such as a Terrain Alert and Warning System (TAWS) (e.g., EGPWS), memory 26, a Flight Management System (FMS) 30, multiple other data sources 38, a voice generator 32, one or more speakers 34, and one or more displays 36. The processor 24 is in data communication with the memory 26, the voice generator 32, the displays 36, the FMS 30, and/or the other data sources 38. Examples of the other data sources 38 include, but are not limited to, a Global Positioning System (GPS) and a pitot-static system.

The processor 24 compares terrain and/or obstacle data that is stored within the memory 26 with one or more look-ahead envelopes based on various data received from an Air Data Computer (ADC) 40, and/or any of the other data sources 38. Example look-ahead envelopes and comparison to stored obstacle and terrain data are described in US Patent Serial No. 6,583,733. If conflicts occur between the created envelopes and any of the stored data based on the comparison, the processor 24 outputs caution or warning alerts via the displays 36 or the speakers 34 via the voice generator 32.

The processor 24 deactivates the comparison of the look-ahead envelopes with the stored data or deactivates any caution or warning alerts produced by the comparison of the look-ahead envelopes to the stored data, if the rate of climb of the rotary aircraft 20 at the current aircraft (ground or air) speed of the aircraft 20 is less than a threshold value. Rate of climb information and aircraft speed information comes from any of a number of sources, such as the ADC 40, or the other data sources 38. Examples of thresholds in relation to the rate of climb and aircraft speed are shown in FIGURES 3 and 4 and described below.

FIGURE 2 illustrates an example process performed by the processor 24 for enhancing EGPWS functionality when the rotary aircraft 20 is in a climbing situation. First, at a block 104, the processor 24 receives rate of climb and aircraft speed information from any of the number of sources. In one embodiment, the processor 24 may include functionality for computing the rate of climb or the aircraft speed based on the data received. Next, at a block 106, the processor 24 compares the received or computed rate of climb and aircraft speed information to a pre-defined threshold or look-ahead On-region using a predefined algorithm, such as is shown in the threshold charts of FIGURES 3 and 4 for example. The threshold chart/algorithm indicates when a look-ahead function of the EGPWS is maintained in an On-state. At a decision block 110, if the comparison performed at the block 106 does not indicate that the rate of climb and aircraft speed information are located within the look-ahead On-region, then at a block 112, the look-ahead function is deactivated or the output of any caution or warning alerts produced by the look-ahead function is suppressed and not outputted to the displays 36 or the speakers 34. If, at the decision block 110, the rate of climb and aircraft speed information are within the look-ahead On-region, then at block 114, the look-ahead function is maintained in an On-state (or activated if previously deactivated). Caution or warning alerts that may be produced by processor 24 as they relate to the look-ahead function are not suppressed and thus would be outputted to the displays 36 or the speakers 34 via the voice generator 32.

FIGURE 3 illustrates a first graph 150 that presents a modified threshold comparison for whether the processor 24 deactivates the look-ahead function or suppresses caution or warning alerts that would be produced by the look-ahead function. In this example, the look-ahead function remains active if the aircraft speed is above a threshold aircraft speed (for example 70 kts) or the rate of climb is above a threshold rate-of-climb (X₁). In one embodiment, the value of X₁ is approximately 500 feet per minute, but may be of any value as desired by the aircraft operator. Also, the threshold aircraft speed may be set at different values depending upon the desires of the aircraft operator.

FIGURE 4 illustrates another threshold graph 160. The graph 160 shows that the On-region for the look-ahead function is defined by any aircraft speed above a threshold, such as 70 kts and above a pre-defined slope line that starts at a first rate of climb (X₂) and drops down to a second rate of climb (X₃) at the aircraft speed threshold (e.g., 70 kts). Therefore, if the graph 160 is used, then the look-ahead function is deactivated or similarly the caution or warning alerts produced by the look-ahead function are deactivated, if the aircraft's speed is less than the threshold speed (70 kts and the rate of climb is below the line defined by rate of climb X₂ at 0 kts and X₃ at 70 kts). In one embodiment, X₃ is approximately 200 feet/minute and X₂ is approximately 500 feet/minute or greater. Other X₂ and X₃ values may be used for defining the threshold rate of climb. Also, the line between X₂ and X₃ may have a curve shape, may be stepped or may be a combination of straight and curved.