c.
Aircraft Torque Factor (ATF). The ratio of an indi-vidual aircraft’s power available to speci.cation power at a reference temperature of 35°C. The ATF is the average of the ETF’s of both engines and its value is allowed to range from 0.9 to 1.0.
7.10.2 Torque Factor Procedure. The use of the ATF or ETF to obtain the TR from Figure 7-2 for ambient tem-
peratures between -15°C and 35°C is shown by the ex-ample. The ATF and ETF values for an individual aircraft are found on the engine HIT Log. The TR always equals
1.0 for ambient temperatures of -15°C and below, and the TR equals the ATF or ETF for temperatures of 35°C and above. For these cases, and for an ATF or ETF value of 1.0, Figure 7-2 need not be used.
7.11 MAXIMUM TORQUE AVAILABLE CHART.
This chart (Figure 7-3) presents the maximum speci.ca-
tion torque available at zero airspeed and 100% RPM R for the operational range of pressure altitude and FAT. The single-and dual-engine transmission limits for continuous operation are shown and should not be exceeded. The en-gine torque available data above the single-engine trans-mission limit is presented as dashed lines and is required for determining torque available when TR values are below
1.0. When the TR equals 1.0, the maximum torque avail-able may be read from the horizontal speci.cation torque available per engine scale. When the TR value is less than 1.0, the maximum torque available is determined by multi-plying the TR by the speci.cation torque available. The lower portion of Figure 7-3 presents TR correction lines which may be used in place of multiplication to read torque available per engine directly from the vertical scale. Re-duce torque by 2% with OBOGS on.
7.12 ENGINE BLEED AIR.
With engine bleed air turned on, the maximum available torque is reduced as follows:
a.
Engine Anti-Ice On: Reduce torque determined from Figure 7-3 by a constant 16% TRQ. Example: (90% TRQ-
16% TRQ) = 74% TRQ.
b.
Cockpit Heater On: Reduce torque available by 4% TRQ.
c.
Both On: Reduce torque available by 20% TRQ.
d.
OBOGS On: Reduce torque available by 2% TRQ.
7.13 INFRARED SUPPRESSOR SYSTEM.
When the hover IR suppressor system is installed and operating in the benign mode exhaust (baffles removed) the maximum torque available is increased about 1% TRQ. When an IR suppressor system is not installed, maximum torque available is also increased about 1%.
TORQUE FACTOR
TORQUE FACTOR ~ ATF OR ETF
.90 .92 .94 .96 .98 1.0
TORQUE RATIO = TR
.84 .86 .88
40 35 30 25 20 15 10 5 0 .5 .10 .15 .20
WANTED:
FOR FAT’S OF 35oC AND ABOVE TR = ATF
FOR FAT’S OF .15OC AND BELOW TR = 1.0
EXAMPLE
TORQUE RATIO AND MAXIMUM TORQUE AVAILABLE
KNOWN:
ATF = .95
PRESSURE ALTITUDE = 6000 FT
FAT = 6oC
METHOD:
TO OBTAIN TORQUE RATIO:
1.
ENTER TORQUE FACTOR CHART AT KNOWN FAT
2.
MOVE RIGHT TO THE ATF VALUE
3.
MOVE DOWN, READ TORQUE RATIO = .972
DATA BASIS: CALCULATED
TO CALCULATE MAXIMUM TORQUE AVAILABLE:
4.
ENTER MAXIMUM TORQUE AVAILABLE CHART AT KNOWN FAT (FIGURE 7.3)
5.
MOVE RIGHT TO KNOWN PRESSURE ALTITUDE
6.
MOVE DOWN, READ SPECIFICATION TORQUE = 97.2% TO OBTAIN VALUE FROM CHART:
7.
MOVE DOWN TO TORQUE RATIO OBTAINED FROM FIGURE 7.2
8.
MOVE LEFT, READ MAXIMUM TORQUE AVAILABLE = 93.0%
AA0675A
SA
Figure 7-2. Aircraft Torque Factor (ATF)
MAXIMUM TORQUE AVAILABLE 30 MIN LIMIT 100% RPM R HIRSS (BAFFLES INSTALLED) ZERO AIRSPEED BLEED AIR OFF
60
FREE AIR TEMPERATURE ~ oC
AA0381B
SA
DATA BASIS: FLIGHT TEST
Section III HOVER
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