Estimated IAF Fuels - Cont'd

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INTERMEDIATE FLIGHT PREPARATION WORKBOOK
CHAPTER TWO
2.
Matrix Method: Set up a matrix of fuel used at convenient time intervals, then add
available time intervals to equal the time remaining. For example, at 1200 lbs/hour, the matrix
would be:
Time (min)
60
30
15
10
6
1
1200 lbs
600 lbs
300 lbs
200 lbs
120 lbs
20 lbs
To speed the matrix calculations, note that 30 minutes is half of 60 minutes, 15 minutes is half of
30 minutes, and 6 minutes is a tenth of an hour.
Wings Level: 106 min = 60 + 30 + 15 + 1 = 1200 + 600 + 300 + 20 = 2120
or
= (60 x 2) - 15 + 1 = 2400 - 300 + 20 = 2120
then
4040 lbs - 2120 lbs = 1920 lbs at IAF
3.  Gauge Method: The gauge method is a variation on the matrix method. Instead of setting
up a matrix, we will use the fuel flow gauges. At fuel flow 1200 lbs/hr, each gauge reads 600
lbs/hr.
Time (min)
# of Gauges
Fuel (lbs)
60
2 gauges
=
1200
45
1 gauge + 1/2 gauge
=
900
30
1 gauge
=
600
20
2/3 of one gauge
=
400
10
1/3 of one gauge
=
200
One minute: 1200 lbs/hr divided by 60 min = 20 lbs/min
Example:
Wings Level: 106 min = 60 + 45 + 1 = 2 gauges + 1 gauge + 1/2 of 1 gauge + 1
= 1200 + 600 + 300 + 20
= 2120
4040 lbs - 2120 lbs = 1920 lbs at the IAF
4.  Pounds Per Nautical Mile (PPNM) Method: Determine fuel flow in terms of PPNM by
dividing fuel flow (lbs/hr) by estimated GS to IAF (NM/hr). Multiply the result by the distance
remaining to IAF.
1200 lbs/hr ÷ 420 NM/hr (estimated) = 2.9 lbs/NM
Wings Level: 742 NM x 2.9 lbs/NM = 2151 (rounded to 2150)
4040 - 2150 = 1890 lbs at IAF
T1-A FLIGHT PROFILES 2-13

 Integrated Publishing, Inc.