b.
Select the appropriate cruise chart for the desired .ight condition and enter the torque scale with the torque value derived above. Move up to the intersection of torque available and the mission gross weight arc, and read across for minimum single-engine airspeed. Move up to the sec-ond intersection of torque and weight, and read across to determine the maximum single-engine speed. If no inter-sections occur, there is no single-engine level .ight capa-bility for the conditions. Single-engine fuel .ow at the de-sired 10 minute, 30 minute, continuous conditions may be obtained by doubling the torque required from the cruise chart and referring to Figure 7–33.
CRUISE EXAMPLE CLEAN CONFIGURATION 100% RPM R
FAT: 30 OC ALT: 6,000 FT
EXAMPLE
TOTAL FUEL FLOW 100 LB/HR WANTED: 6 7 8 9 10 111213 170
A. CRUISE CONDITIONS FOR MAXIMUM RANGE
130
140
B. CONDITIONS FOR MAXIMUM ENDURANCE
C. MAXIMUM AIRSPEED IN LEVEL FLIGHT
160
D. DETERMINE TORQUE AND FUEL FLOW
180 REQUIRED TO CRUISE AT THE CONDITIONS
OF EXAMPLE A WITH CABIN DOORS OPEN
150
170
KNOWN:
160
140
FAT = + 30oC PRESSURE ALTITUDE = 6000 FT GW = 17000 LBS
150
ATF = 0.95
METHOD:
120
A. TURN TO CRUISE CHARTS NEAREST KNOWN FLIGHT CONDITIONS, AT INTERSECTION 130 OF MAX RANGE LINE AND KNOWN VALUE OF
110
GROSS WEIGHT:
MOVE LEFT, READ TAS = 135 KTS
120MOVE RIGHT, READ IAS = 119 KTS MOVE DOWN, READ TORQUE = 62% TRQ
INDICATED AIRSPEED ~ KTS
100
MOVE UP, READ TOTAL FUEL FLOW = 900 LBS / HR
TRUE AIRSPEED ~ KTS
110
B. AT INTERSECTION OF MAX END. / AND R / C
LINE AND KNOWN VALUE OF GROSS WEIGHT: MOVE LEFT, READ TAS = 82 KTS
MOVE RIGHT, READ IAS = 67 KTS MOVE DOWN, READ TORQUE = 41% TRQ
MOVE UP, READ TOTAL FUEL FLOW = 700 LBS / HR
C. AT INTERSECTION OF 30.MINUTE TORQUE AVAILABLE AS INTERPOLATED FOR THE ATF
VALUE AT THE KNOWN GROSS WEIGHT:
MOVE LEFT, READ MAXIMUM TAS = 153 KTS
MOVE RIGHT, READ MAXIMUM IAS = 135 KTS
100
90
80
MOVE DOWN, READ MAXIMUM TORQUE = 82% TRQ
MOVE UP, READ TOTAL FUEL FLOW = 1125 LBS / HR
70
D. ENTER
TRQ% PER 10 SQ FT SCALE AT 135 KTAS
MOVE UP READ
TRQ = 8.0%
TURN TO DRAG TABLE IN SECTION VII 60
NOTE CABIN DOORS OPEN = 6.0 SQ FT
F
AND HAS A DRAG MULTIPLYING FACTOR VALUE
40 OF 0.60, CALCULATE TOTAL TORQUE REQUIRED:
50
62% + (0.6 X 8.0%) = 66.8% TRQ
30 40
READ FUEL FLOW AT.TOTAL TORQUE = 950 LBS / HR
30
20
10
10 0 0
TORQUE PER ENGINE ~ %
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SA
Figure 7-6. Sample Cruise Chart -Clean
7-14
130
110
110
120
100
100
110
90
100
90
90
80
80
160
150
130
130
140
120
CRUISE
CRUISE 0 FT
CLEAN CONFIGURATION T700 (2) PRESS ALT: 0 FT
.50OC.40OC
TOTAL FUEL FLOW ~ 100 LB/HR IAS ~ KTS TOTAL FUEL FLOW ~ 100 LB/HR
6 7 8 9 10111213 6 7 8 9 10111213
170
TRUE AIRSPEED ~ KTS
80
70
70
TRUE AIRSPEED ~ KTS
60
50
40
30
30
30
20
10
10
10
0
0
0
TORQUE PER ENGINE ~ % TORQUE PER ENGINE ~ %
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