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 Jamie's Online Flight Calculator
Jamie's Aviation Flight Computer

Now available as an Android app on the Google Play Store
and as an Apple iOS app on Apple App Store

[ Return to Functions List ]

ETP (Equivalent Time Point) and
PNR (Point of No Return) calculator


GS (Return): kts
GS (Continue): kts
Trip Distance: NM
ETP Distance: NM
ETP Time: min

GS (Return): kts
GS (Outbound): kts
Safe Fuel Endurance:
Total Fuel Qty: units
Avg. Fuel Flow: units/hr
PNR Distance: NM

How ETP and PNR are calculated

Equivalent Time Point (ETP)

The Equivalent Time Point (ETP), also known as the Critical Point (CP), is the point at which the aircraft's position is equidistant (the same flying time) from two suitable en-route Alternates (accounting for wind and temperature conditions). ETPs created for legs/segments during the flight are useful for managing worst case scenarios. The formula for calculating ground ETP distance (DETP) and ETP time is given above. It uses the Ground Speeds of the Return-to Alternate (GSr) and Continue-to Alternate (GSc) and the Trip/Leg distance (Dtrip).

Point of No Return (PNR)

The Point of No Return (PNR) is the point on the flight path at which the aircraft becomes unable to return to the departure aerodrome due to fuel constraints. Beyond this point the aircraft must proceed to another other destination. Calculation of the PNR is mandatory for flights overwater or those without Alternates on route.

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