Time to PSR = E x H    Where: E = Fuel endurance: 3 hrs 10 mins (3.17hrs)

                         (O + H)                 H = Groundspeed home

                                                       O = Groundspeed out

 

To find H and O use CRP5 or similar:

 

Centre dot on TAS, 140 kts, rotate to wind direction, 100°; come down from centre dot for wind speed, 25 kts; mark end of wind vector at 115 kts.

 

Rotate to outbound track (135º) under heading index; note drift 7°Stbd; rotate track to drift; note drift now 6°Stbd; rotate track to drift; note drift still 6°Stbd.  Required heading outbound will be 129° to track 135°; groundspeed out, O = 119 kts

 

Rotate to homebound track (315º) under heading index; note drift 5°Port; rotate track to drift; note drift now 6°Port; rotate track to drift; note drift still 6°Port.  Required heading homebound will be 321° to track 135°; groundspeed home, H = 159 kts

 

            Time to fly out =  3.17 x 159  = 1.81 hr = 1 hr 49 mins

                                            (119 + 159)