TM 1-1510-224-10
m.
Flight
Planning
Example.
The
following
calculations provide information for flight planning.
Calculations for flight time, block speed, and fuel
requirements for the proposed flight are detailed below.
NOTE
For
example
purposes,
the
differences between MSL altitudes
and pressure altitudes have been
ignored in MEA calculations.
(1)
ISA conversion. Enter the graph at the
conditions indicated:
BIL
Pressure Altitude ................................... 3499 feet
FAT............................................................. 15C
ISA Condition......................................... ISA+7C
BIL-CZI
Pressure Altitude ................................ 25,000 feet
FAT............................................................ -40C
ISA Condition.......................................... ISA-6C
CZI-CPR
Pressure Altitude ................................ 25,000 feet
FAT............................................................ -30C
ISA Condition......................................... ISA+5C
CPR
Pressure Altitude ................................... 5998 feet
FAT............................................................. 20C
ISA Condition....................................... ISA+17C
(2)
Time, fuel, and distance to cruise climb.
Enter the graph at 15C, to 3499 feet pressure altitude,
and to 16,000 pounds. Enter again at -400C to 25,000
feet pressure altitude, and to 16,000 pounds. The
following results are obtained:
Time to Climb ...................................22 - 2 = 20 min
Fuel to Climb............................... 392 - 50 = 342 lbs
Distance Traveled............................. 52 - 4 = 48 nm
(3)
Time fuel, and distance to descend. Enter
the graph at 25,000 feet, and enter again at 5998 feet,
and find:
Time to Descend...............................17 - 4 = 13 min
Fuel Used to Descend.................. 206 - 58 = 148 lbs
Distance to Descend ....................... 62 - 13 = 49 nm
(4)
Cruise weight (estimated).
For
the
following cruise segment examples, the estimated
average cruise weight used was 15,600 pounds.
(5)
Cruise tables. Enter the tables for Normal
Cruise Power at 1500 RPM for ISA -10C, ISA, and ISA
+10C, and read the cruise speeds for 24,000 feet and
26,000 feet at 16,000 pounds and 14,000 pounds.
Interpolate between these speeds for 25,000-foot
values. Refer to table 7-2 for the results.
Interpolate between the 25,000-foot speeds for
ISA -6C and ISA +5C at 15,600 pounds.
Cruise True Airspeed (ISA -6C)................. 257 knots
Cruise True Airspeed (ISA +50C).............. 246 knots
Similar computations can be made to interpolate
for cruise torque setting and fuel flow.
Cruise Torque (ISA-6C)................................ 68.5%
Cruise Total Fuel Flow (ISA -6C) ............. 778 lbs/hr
Cruise Fuel Flow/Eng (ISA -6C)............... 389 lbs/hr
Cruise Torque (ISA+5C)............................... 61.4%
Cruise Total Fuel Flow (ISA +5C)............. 716 lbs/hr
Cruise Fuel Flow/Eng (ISA +5C) .............. 358 lbs/hr
(6)
Cruise graphs. In addition to the cruise
performance
presented
in
tabular
form,
data
representing a cruise weight of 14,000 pounds is
presented in graphical form for quick reference.
Table 7-2. Example Cruise True Airspeeds
ALT
FEET
16,000 POUNDS
14,000 POUNDS
ISA - 10°C
ISA
ISA +10°C
ISA - 10C
ISA
ISA +10°C
24,000
261
253
242
267
260
250
25,000
259
250.5
238.5
265.5
258
248
26,000
257
248
235
264
256
246
BT05789
7-14
