Abstract:
Systems and methods that alert the pilot of the unusual negative pitch attitude. Additionally, the system can bias a “sink rate” envelope toward a more sensitive direction, such that the pilot can be alerted while (or before) a large sink rate is built up during an unusual negative pitch attitude condition.

Description:
PRIORITY CLAIM 
     This application claims priority to Provisional Application Ser. No. 61/332,564 filed on May 7, 2010 and is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     In many helicopter accidents, pilots get disoriented, and often drop the helicopter&#39;s nose (negative pitch) without noticing it. Sometimes pilots get confused and in some cases, pilots don&#39;t realize what is going on and end up crashing into the ocean or ground. 
     SUMMARY OF THE INVENTION 
     An unusual negative pitch attitude (e.g., −20 degrees) is the first sign that the helicopter is about to dive and accelerate. The present invention provides systems and methods that alert the pilot of the unusual negative pitch attitude. 
     Additionally, the system can bias a “sink rate” envelope toward a more sensitive direction, such that the pilot can be alerted while (or before) a large sink rate is built up during an unusual negative pitch attitude condition. 
     The present invention includes a processing device that receives a current pitch angle value and generates an alert if the received pitch angle value is more negative than a predefined pitch angle threshold value. An output device outputs the generated alert. 
     The processing device is further configured to adjust the pitch angle threshold value based on altitude. 
     In one aspect of the invention, a system includes a processing device that receives a current pitch angle value, adjusts a sink rate alert envelope if the received pitch angle value is more negative than a pitch angle threshold value, and generates an alert if sink rate is within the sink rate alert envelope. A output device outputs the generated alert. 
     In another aspect of the invention, the processing device adjusts the sink rate alert envelope only if the sink rate alert envelope was previously at a default position. 
     In still another aspect of the invention, the processing device returns the pitch rate alert envelope to the default position if the received pitch angle value is not more negative than a pitch angle threshold value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
         FIG. 1  illustrates a block diagram of a system on a rotary-wing aircraft formed in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates a side view of a helicopter in an excessive negative pitch attitude; 
         FIG. 3  is a flowchart identifying a potentially hazardous negative pitch condition; 
         FIG. 4  illustrates a graph associated with the process shown in  FIG. 3 ; 
         FIG. 5  is a flowchart of an exemplary process for biasing a sink rate alert envelope; and 
         FIG. 6  illustrates a sink rate alert envelope adjusted according to the process shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a block diagram of a rotary-wing aircraft  20  that includes a processor  30 , such as an enhanced ground proximity warning system (EGPWS) processor. The aircraft  20  also includes a radio altimeter (RADALT)  32  and an air data system  34 , a gyroscope  36 , and an alerting device  38  that are all in signal communication with the processor  30 , and a user interface device  40 . 
     The processor  30  includes instructions for alerting the pilot of the aircraft  20  if the pitch attitude is beyond a threshold negative value and/or adjusting a prestored sink rate envelope based on a pitch attitude received from the gyroscope  36 . If the processor  30  determines that either a “nose-too-low” or a pitch rate alert is necessary, then a corresponding alert signal is sent to the alerting device  38  that outputs a corresponding alert audibly and/or visually. 
       FIG. 2  illustrates the rotary-wing aircraft  20  that is presently at a pitch angle θ  42  that is below the pitch angle threshold value. In such a situation, the processor  30  will alert the pilot that the nose is too low and that an acceleration condition may exist. 
       FIG. 3  illustrates a process  60  performed by the processor  30  for alerting the flight crew of an excessive pitch angle attitude. First, at a block  62 , a pitch angle value is received from the gyroscope  36 . Next, at a decision block  64 , the processor  30  determines if the received pitch angle value is more negative than a pitch angle threshold value θ  42 . If the received pitch angle value is not more negative than the pitch angle threshold value, the process returns to block  62 . If, however, the received pitch angle value is more negative than the pitch angle threshold value, the processor  30  generates and outputs an audible or visual “nose-too-low” alert. 
       FIG. 4  illustrates a graph  80  that shows a change in the pitch angle threshold value based on altitude. For example, the graph  80  shows that below 100 feet the pitch angle threshold value is −15 degrees but is a graduated scale to between 100 feet and 300 feet, up to a threshold of −18 degrees. This provides more sensitivity to this condition when the aircraft is lower to the ground. 
       FIG. 5  illustrates an exemplary process  100  performed by the processor  30  for adjusting a sink rate alert envelope. First, at a block  102 , just like in block  62  of  FIG. 3 , the pitch angle value is received from the gyroscope  36 . Next, at a decision block  104 , the processor  30  determines if the received pitch angle value is more negative than a pitch angle threshold value. If not, the process  100  returns to the block  102 . If the pitch angle value is determined to be more negative than the pitch angle threshold value, then at a block  108 , a sink rate alert envelope is made more sensitive if the sink rate alert envelope is presently at its default position. In other words, the sink rate alert envelope is not made more sensitive if it has previously been made more sensitive. Next, at a decision block  110 , the processor  30  determines if the pitch angle value is not more negative than the pitch angle threshold value. What is occurring here is a determination as to whether the state is still active. If the state is of a pitch angle value greater negative than the pitch angle threshold value, then the process  100  stays in its current state. However, if the pitch angle value becomes not more negative than the pitch angle threshold value, then, at a block  112 , the sink rate alert envelope defaults or returns to its default position. 
       FIG. 6  illustrates a graph  130  that shows the sink rate alert envelope plotted with vertical speed (feet per minute (FPM)) on an x axis and an altitude (radio altitude (H)) along the y axis. The solid line indicates the existing or default sink rate envelope. When the condition is met where the pitch angle value of the aircraft  20  is more negative than the pitch angle threshold value, then the sink rate envelope becomes modulated to a more sensitive position, as indicated by the dashed line to the left along the x axis within the graph  130 . 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.