Photo: Point of No Return, from "The High and the Mighty"
Some call the point where you can reverse course and make it back to your departure airport the "Point of No Return." I think if you do that, you should have the sound track to "The High and the Mighty" cued up and whenever anybody says "point of no return," there should be dramatic music playing. I prefer to call it the "Point of Safe Return."
The Point of Safe Return is seldom discussed because it is rarely critical with modern aircraft designed for oceanic travel. About the only time I've ever used it was during combat operations to Bosnia and even then it was academic; we always had enough fuel to get to Sarajevo, reject the landing, and come home. But even without the threat of a AAA battery, the PSR can be of use to you.
What follows comes from the references shown below. I've added my own techniques in blue.
The Point of Safe Return (PSR) provides the pilot with the farthest point to which the aircraft can go and be able to return safely to the departure point with adequate holding, approach, landing, and alternate fuel. It is normally used when flying to remote island destinations with no diversion possibilities en route but can be useful even when alternates are available.
There is no regulatory requirement to compute a Point of No (or Safe) Return. In fact, the only regulatory mention is for 14 CFR 121 and even that is less than definitive:
[14 CFR 121, §121.389]
Figure: Equal Time Point and Point of No Return, from G450 Performance Handbook, page PB-23.
[G450 Performance Handbook, page PB-23.] The following formula is used to calculate the ground distance from the departure airport to the Point of Safe Return:
Endurance = Total Fuel Quantity / Average Fuel Flow
GSO = Normal Outbound Ground Speed at Cruise Altitude
GSR1 = Return Ground Speed at Normal Cruise Altitude
A few notes:
Figure: Master Document Example Page 5, PNR, from Eddie's Notes.
The example flight used in International Operations Manual / Oceanic Departure is from KBED to LSGG on a G450 which has more than ample range. The flight planning service automatically computed a "PNR" which came to 1,161 nm from KBED. They provided a latitude / longitude so we plotted that:
Figure: Example Plotting Chart, from Eddie's notes.
If any of our passengers, for some reason, decide they need to go back to our departure airport (KBED), the last moment you can do this without having to make a fuel stop is shown with the red bracket on the chart. Keep in mind that if you return at this point, you will need to fly direct to the airport, the PSR does not use normal routings that anyone less than an emergency aircraft will be offered.
Portions of this page can be found in the book Flight Lessons 2: Advanced Flight, Chapter 10.
Portions of this page can be found in the book International Flight Operations, Part VIII, Chapter 30.
14 CFR 121, Title 14: Aeronautics and Space, Operating Requirements: Domestic, Flag, and Supplemental Operations, Federal Aviation Administration, Department of Transportation
Gulfstream G450 Performance Handbook, GAC-AC-G450-OPS-0003, Revision 20, November 30, 2011