INSTRUMENTS FLIGHT PLANNING
In order to accurately revise ETAs and EFRs, the following method is suggested:
Take a GS check.
Sometime after completion of the GS check, "freeze" the following items in your cockpit (done
Fuel on board
Actual clock time
Armed with these figures you can accurately revise your ETAs and EFRs.
Here is a practice example:
DME = MAI 272/35
Fuel on board = 670 lbs
Fuel flow = 240 PPH or 4 lbs/Min
GS = 210
At 50+00 we are 35 NM from MAI. With a GS of 210 kts, we are at MAI in 10 minutes
(00+00). To calculate EFR at the IAF we add our ETE to MAI (10 min) to our ETE from MAI
to the IAF (16 min) for a total of 26 min remaining to the IAF. Since our fuel flow is 4 PPM, we
burn an additional 105 lbs to the IAF. Our on-board fuel is 670 lbs 105 lbs = 565 lbs EFR at
This example is an oversimplified case of using the freeze technique. In a real world situation,
your numbers are not likely to be as round as these were, so you must learn to work quickly with
these calculations, since you must simultaneously navigate and communicate.
The procedure described above in which preflight ETEs are combined with actual fuel flow to
predict future fuel states is considered the most practical method for such calculations here in the
training environment. It is assumed that your preflight ETEs are accurate.
If your route of flight (Figure 5-4) was from Pensacola through Crestview, Montgomery,
Meridian, New Orleans, Semmes to the Navy Pensacola IAF, you can see that a GS check
obtained between Crestview and Montgomery would not hold true for the rest of the flight. If
your flight is in a relatively straight line, it is correct to apply GS checks to future legs of flight to
recalculate your ETEs. Whenever possible, the latter technique is employed.
IN-FLIGHT FUEL AND TIME ANALYSIS