System and method for the calculation of the approach speed during air to air refuelling operations

1. A system for calculating the difference in speed between a receiver aircraft and a tanker aircraft in an approach operation for conducting a refueling operation using a hose and drogue device, characterized in that it comprises:

a) capturing means of a sequence of digital photograms of the approach operation scenario located on a place of the tanker aircraft that enables laterally viewing said scenario, said capture means being calibrated in order to determine the real distance corresponding to a pixel of a photogram;

b) computational means implemented for:

b1) obtaining the coordinates of the relative trajectory between the receiver aircraft and the tanker aircraft by means of processing a sequence of photograms of the approach operation obtained by said capture means in which:

following the selection in the first photogram of a pattern area of a predetermined size in which a portion of receiver aircraft is viewed, the storing of the 2D coordinates of its midpoint and the identifying of a reference frame having the same midpoint, shape and a larger size than that of pattern area by a predetermined scaling factor,

in each photogram following the first the identification of a new pattern area as well as a new reference frame of the same pattern area, having the same features as in the photogram, searching in said new pattern area for the image in the reference frame of the previous photogram,

the storing of 2D coordinates of the midpoint of new pattern area and the instant in time of the photogram;

b2) calculating the difference of the speed between receiver aircraft and tanker aircraft, based on the trajectory defined by the stored coordinates in process b1).

2. The system of claim 1 wherein the hose and drogue device is deployed from a gondola located on the wing of tanker aircraft and said capture means are located on the rear portion of the fuselage of tanker aircraft.

3. The system of claim 1 , wherein the calculation of the difference of the speed between receiver aircraft and tanker aircraft is done in real time.

4. The system of claim 1 wherein pattern areas and reference frames have a square shape.

5. The system of claim 4 , wherein the scaling factor between the number of pixels of each side of reference frames and pattern areas is comprised between 3 and 5 pixels.

6. A method for calculating the difference in speed between a receiver aircraft and a tanker aircraft in an approach operation for conducting a refueling operation using a hose and drogue device, wherein it comprises the following steps:

a) obtaining a sequence of digital photograms of the approach operation from a place on the tanker aircraft that enables lateral viewing of said scenario knowing the real distance corresponding to a pixel of a photogram;

b) obtaining the 2D coordinates of the relative trajectory of receiver aircraft shown in said sequence of photograms with respect of tanker aircraft by means of the following sub-steps:

b1) selecting in the first photogram a pattern area of the receiver aircraft having a small size, in which a portion of receiver aircraft is visible, and obtaining and storing the 2D coordinates of its midpoint, and identifying a reference frame of pattern area having the same midpoint, shape, and a larger size than that of the pattern area of a predetermined scaling factor;

b2) searching for pattern area of the previous photogram on the next photogram within the reference frame identified in the previous photogram and, once found, using it as the new pattern area, obtaining and storing the 2D coordinates of its midpoint, as well as the instant in time of photogram, and identifying and defining the reference frame of the said new pattern area in the same way as in the previous sub-step;

b3) repeating sup-step b2) for the rest of the photograms of the sequence;

c) calculating the difference of the speed between receiver aircraft and tanker aircraft, based on the trajectory defined by the 2D coordinates of each pattern area midpoint stored in step b).

7. The method of claim 6 , wherein hose and drogue device is deployed from the gondola located on the wing of tanker aircraft and photograms are obtained from the rear portion of the fuselage of tanker aircraft.

8. The method of claim 6 , wherein the calculation of the difference of the speed between receiver aircraft and tanker aircraft is done in real time.

9. The method of claim 6 , in which pattern area and reference frame have a square shape.

10. The method of claim 9 , wherein the scaling factor between the number of pixels on each side of reference frames and pattern areas is comprised between 3 and 5 pixels.