
 T39 FLIGHT PREPARATION
STUDENT GUIDE
DISTANCE TO
DISTANCE TO
TIME TO
TIME TO
IAF
NEXT PT
IAF
NEXT PT
PT #1
140
770
0+20
1+50
PT #2
N/A
630
N/A
1+30
You mark on top of PT #1 at 40+00 with 6100# of fuel. Enroute to PT #2 you
complete a ground speed check: you are traveling 420 kts (7 NM/min). When you "freeze"
the fuel quantity and fuel flow, you have: time (44+00); fuel now (6040 #); fuel flow
(1800 #/hr); distance to PT #2 (112 NM). Compute IAF fuel for wingslevel after PT #1
and IAF fuel after ground speed check.
Ground speed check:
112 NM ÷ 7 NM/min = 16 min to PT #2
16 min (to PT #2) + 90 min (PT #2 to IAF) = 106 min (to IAF)
(1)
Pounds per minute method:
Divide fuel flow by 60 to determine pounds per minute. Multiply pounds per minute
by minutes remaining to IAF.
1800#/hour ÷ 60 min/hour = 30.0 #/min
Wings Level:
106 min x 30.0#/min = 3180# fuel burned to IAF
6040#  3180# = 2860# at IAF
(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 1800 # per hour, the matrix would
be:
Time (min)
60
30
15
10
6
1
1800#
900#
450 #
300 #
180#
30#
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 = 1800 + 900 + 450 + 30 = 3180
or
= (60 x 2)  15 + 1 = 3600  450 + 30 = 3180
then
6040#  3180# = 2860# 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 1800#/hr, each gauge reads 900#/hr.
Time (min) minutes
Fuel (number of gauges)
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