Photo: Point of No Return, from "The High and the Mighty"

Eddie Sez:

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.


PSR Explained

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.


Regulatory Requirement

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]

  1. No certificate holder may operate an airplane outside the 48 contiguous States and the District of Columbia, when its position cannot be reliably fixed for a period of more than 1 hour, without—
    1. A flight crewmember who holds a current flight navigator certificate; or

    2. Specialized means of navigation approved in accordance with §121.355 which enables a reliable determination to be made of the position of the airplane by each pilot seated at his duty station.
  2. Notwithstanding paragraph (a) of this section, the Administrator may also require a flight navigator or special navigation equipment, or both, when specialized means of navigation are necessary for 1 hour or less. In making this determination, the Administrator considers—
    1. The speed of the airplane;

    2. Normal weather conditions en route;

    3. Extent of air traffic control;

    4. Traffic congestion;

    5. Area of navigational radio coverage at destination;

    6. Fuel requirements;

    7. Fuel available for return to point of departure or alternates;

    8. Predication of flight upon operation beyond the point of no return; and

    9. Any other factors he determines are relevant in the interest of safety.
  3. Operations where a flight navigator or special navigation equipment, or both, are required are specified in the operations specifications of the air carrier or commercial operator.

Point of Safe Return, The Math

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:

Ground Distance to PSR = ( Endurance ) ( GSR1 ) ( GSO ) GSO + GSR1 = NM

Where:

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:

  • Unlike the ETP, the Point of Safe Return should be based on your original departure airport, since that is where you are likely to want to go if it becomes an issue. (More on that below.)

  • The terms GSR, GSC, and ETP are for the "Equal Time Point." More about that: International Operations / Equal Time Points.

Example PSR

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.


Book Notes

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.


References

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