ETP (equal time point)
 

Hi everybody! Does any body remember the ETP formula?

Equal Time Point (ETP) = Total Ground distance *(GSr/(GSr + GSc))

Total Ground Distance = ground distance along intended route
GSr = Ground speed return
GSc = Ground speed continue

The ground speed is the average TAS plus the wind. With the wind sign convention as headwind -ve and tailwind +ve

Its also called PET - point of equal time

d = (D * H)/ (O + H)

d= dist to pet from A , D =total dist between the two bases,
H= GS home from PET to A , O= GS on from PET to B

Hope it helps .. further info available from Ground Studies for Pilots

Thankyou
 

Thank you very much guys!!!

ETP = (D x GSret)/(GSret + GSFWD)

D = total distance for flight

GSret = ground speed from the ETP back to the orgin

GSfwd = ground speed from the ETP to the destination

ETP = distance from the departure airport to the ETP

Don't forget your wind shift and wet footprint.

Thank goodness todays computer generated flight plans(CFP) caculate all this for you. They also calculate for the senario of an engine loss, which would produce a driftdown to a lower altitude, with different fuel burns at same and lower speeds.