TM 1-1510-223-10
ISA -6C (-35C IFAT)
Fuel Flow Per Engine ..............................362 Ibs/hr
Total Fuel Flow ....................................... 724 lbs/hr
Time and fuel used were calculated at normal cruise
power at 1500 RPM as follows:
Time = distance/ground speed
Fuel used = (time)(total fuel flow)
(7)
Flight planning results. Refer to table 7-3
(EXAMPLE CRUISE RESULTS) for an illustration of the
flight planning procedure.
NOTE
For flight planning, enter the Fuel
Flow Graphs at the forecast ISA
condition; for enroute fuel flow, enter
the graphs at the actual IFAT.
Refer to table 7-4 (EXAMPLE TIME, FUEL, AND
DISTANCE) for an illustration of the total flight planning
results.
(a)
Reserve fuel. Reserve Fuel is the
amount of fuel required to fly at cruise altitude for 45
minutes at maximum range power. This example
assumes the average cruise weight while using reserve
fuel to be 15,000 pounds.
Enter the MAXIMUM RANGE POWER AT 1500
RPM tables for ISA and for ISA +10C and interpolate to
find the total fuel flow for 25,000 feet at 16,000 pounds
and 14,000 pounds. Interpolate between these values
for 15,000
pounds. In this example it is found that data is
presented for MAXIMUM RANGE POWER AT 1500
RPM for ISA and ISA +100C at 24,000 feet and at
26,000 feet for 14,000 pounds, but not for 16,000
pounds. Consequently, it is not possible to determine a
maximum range power torque, airspeed, or fuel flow for
15,000 pounds at 25,000 feet, since chart values may
not be extrapolated. This means that either a lower
altitude must be selected for the leg of the mission that
would be using reserve fuel, or that the NORMAL
CRUISE POWER AT 1500 RPM values must be used to
determine
power
setting
and
the
reserve
fuel
requirement. If no values are presented for the given
conditions in the NORMAL CRUISE POWER AT 1500
RPM tables either select a lower altitude, or use the
maximum cruise power at 1700 RPM table values to
determine
power
setting
and
the
reserve
fuel
requirement. In this example it is found that data is
presented for the mission conditions in the NORMAL
CRUISE POWER AT 1500 RPM tables, so that data can
be used. Refer to table 7-5 (EXAMPLE FUEL FLOW)
for an illustration of the reserve fuel determination
procedure.
(8)
Total fuel requirement. Expected fuel
usage + reserve fuel = total fuel requirement. (916 Ibs)
+ (539 lbs) = 1455 lbs.
(9)
Zero-fuel weight limitation.
For this
example, the following conditions were assumed:
Ramp Weight ......................................... 16,120 lbs
Weight of Usable Fuel on Board .................3631 lbs
Zero Fuel Weight = (16,120 - 3631) ......... 12,489 lbs
Maximum Zero Fuel Weight (from Chapter 5 -
LIMITATIONS) ....................................... 13,100 lbs
Table 7-3. Example Cruise Results
ESTIMATED
2TIME AT
3FUEL
ROUTE
GROUND
CRUISE
USED FOR
SEGMENT
1DISTANCE
SPEED
ALTITUDE
CRUISE
NM
KNOTS
MIN
LBS
BIL-SHR
34
254
8.0
104.41
SHR-CZI
57
294
11.6
151.22
CZI-CPR
10
256
2.3
28.05
TOTAL
101
---
21.9
283.68
1
Time Distance required to climb or descend has been subtracted from segment distance.
2
Time =Distance divided by Ground Speed.
3
Fuel Used =Distance divided by Ground Speed, multiplied by total Fuel Flow.
BT03668
7-10 Change 2
