# Calculate PNR (point of no return)

A useful template to calculate the furthest Distance removed from an aerodrome that you may travel and safely return with an adequate fuel reserve remaining. This is especially useful when traveling on large overwater legs on the sim or remote areas without an alternate destination. The formula is as follows;

Endurance in hours (- Fuel reserve) X Groundspeed out to destination X Groundspeed home / ( Out + Home)

Hope this helps!
Note: For sim use only! (Obviously)

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Oh thank you I was going to try and do this on a real singe engine Cessna flight crossing the Atlantic. (š¤£)

And interesting I would use this to add to my realism but I donāt know how to find the endurance š

And I have a question the result what unit will that be in (hours, nautical miles, etc.)?

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You should add in the denominator instead of multiplying. The dimensions of the numerator are length squared per time so you need to divide by length per time to end up with just length. That gives you the distance to the pnr.

In other words it should be:
Endurance in hours (- Fuel reserve) X Groundspeed out to destination X Groundspeed home / ( Out + Home)

From there if you want the time to the pnr just divide that^ by ground speed outbound.

Just making sureš¤£
And just to add on to what MrMrMan said. Endurance = Ammount of fuel / the rate at which it is consumed (this will be displayed in HRS. X the result by 60 if you want it in mins)š¤

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yes you are absolutely right, Sorry about that guys (out + Home) The power of proof reading!
Thanks for the pick up!š¤

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No worries! A little dimensional analysis always saves the day lol

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Isnāt this literally useless in IF unless you think youāll run out of fuel?
Like this kind of planning is only used in case of engine failure right?

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Thatās more the equi time point (CP) formula. The point of no return takes into account en-route winds so if youāre over the water in a C172 and find that the wind is a lot stronger than anticipated, you can calculate if you should go back or press on. I referred to this formula countless times when flying from Colombo to Nagpur in India when doing a circumnavigation in a C172 ( on IF sadly) and calculated that if I pressed on iād land With only 7 mins of fuel remaining which I did.

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Ahā¦ I use skyvector to plan flights so wind surprises basically never happen.

Hi there, thanks for bringing this!
I wonder if there is a little mistake though. What I find online is Endurance Ć GS back / GS out + GS back
Am I right?

I just checked the notes and found that my explanation was fine. There are multiple ways of working this out. Iāve only done the method that Iāve posted but Iām keen to cross-check!!

Hah! Iāve never tried sky vector. I tried to find international forecasts on IF with no luck so I bounced off METARsš¤£

Well skyvector shows you the flight time. Other than a couple of exceptions (E170 looking at you), the fuel time estimate is less than the actual flight time you can get out of the aircraft. I add 30 for takeoff and landing, 30 for diversion, 30 for emergency and 5% or 15 for contingency. I have proper fuel numbers for some aircraft and for that I do the same.

Yeah thatās a really good way to break down Fuel planning, because it doesnāt matter whether youāre in an A380 or a cub you always have a personal minimum ātemplateā That you can refer too

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