This ETP can also be called "Medical" or some variation leading to the idea the airplane divert but not need to descend or decelerate.
GS r is the groundspeed to return to departure from the ETP. Since ETP is most significant for the overwater portion of a flight, the ETP should be determined from coastal departure points and for alternate landing points.
Total distance is the number of nautical miles from departure to destination.Total Distance GS r + GS c = ETP (in miles from departure) GS r Use the following formula to compute a ETP:.When computing ETP, obtain a wind factor for each half of the route.
When the wind factor is a minus value (GS less than TAS), it is called a head wind factor when it is a plus value (GS greater than TAS), it is a tail wind factor. To do this, algebraically subtract the TAS from the GS. A wind factor is a headwind or tailwind component which is computed by comparing the average groundspeed (GS) to the true airspeed (TAS).Its location is somewhere near the midpoint of the route, however, and it dependent upon the wind factor. The ETP is not necessarily the midpoint in time from departure to destination.It is usually computed when planning long, overwater flights. The equal time point is a point along the route from which it takes the same amount of time to return to departure as it would to continue to destination.