c.
Fuel Flow. Fuel .ow scales are provided opposite the torque scales. On any chart, torque may be converted di-rectly to fuel .ow without regard to other chart informa-tion. Data shown in this section is for two-engine operation. For one-engine fuel .ow, refer to Section VIII FUEL FLOW.
(1) With bleed-air extracted, fuel .ow increases:
(a)
Engine anti-ice on -About 60 lbs/hr Example: (760 lbs/hr + 60 lbs/hr = 820 lbs/hr.)
(b)
Heater on -About 20 lbs/hr.
(c)
Both on -About 80 lbs/hr.
(2)
When the cruise IR suppressors are removed or hover IR suppressor system is installed and operating in the benign mode (exhaust baffles removed), the dual-engine fuel .ow will decrease about 16 lbs/hr.
d.
Maximum Range. The maximum range lines (MAX RANGE) indicate the combinations of gross weight and
airspeed that will produce the greatest .ight range per pound of fuel under zero wind conditions. When maximum range airspeed line is above the maximum torque available, the resulting maximum airspeed should be used for maxi-mum range. A method of estimating maximum range speed in winds is to increase IAS by 2.5 knots per each 10 knots of effective headwind (which reduces .ight time and mini-mizes loss in range) and decrease IAS by 2.5 knots per 10 knots of effective tailwind for economy.
e.
Maximum Endurance and Rate of Climb. The maxi-mum endurance and rate of climb lines (MAX END and R/C) indicate the combinations of gross weight and air-speed that will produce the maximum endurance and the maximum rate of climb. The torque required for level .ight at this condition is a minimum, providing a minimum fuel .ow (maximum endurance) and a maximum torque change available for climb (maximum rate of climb).
f.
Change in Frontal Area. Since the cruise information is given for the 9clean con.guration,9 adjustments to torque should be made when operating with external sling loads or aircraft external con.guration changes. To determine the change in torque, .rst obtain the appropriate multiplying factor from the drag load chart (Figure 7-30), then enter the cruise chart at the planned cruise speed TAS, move right to the broken
TRQ line, and move up and read
TRQ. Multiply
TRQ by the multiplying factor to obtain change in torque, then add or subtract change in torque from torque required for the primary mission con.guration. Enter the cruise chart at resulting torque required, move up, and read fuel .ow. If the resulting torque required exceeds the gov-erning torque limit, the torque required must be reduced to the limit. The resulting reduction in airspeed may be found by subtracting the change in torque from the limit torque; then enter the cruise chart at the reduced torque, and move up to the gross weight. Move left or right to read TAS or IAS. The engine torque setting for maximum range ob-tained from the clean con.guration cruise chart will gener-ally result in cruise at best range airspeed for the higher drag con.guration. To determine the approximate airspeed for maximum range for alternative or external load con.gu-rations, reduce the value from the cruise chart by 6 knots for each 10 square foot increase in drag area,
F. For example, if both cabin doors are open the
F increases 6 ft2 and the maximum range airspeed would be reduced by approximately 4 knots (6 Kts/10 ft236ft2 = 3.6 Kts).
g. Additional Uses. The low speed end of the cruise chart (below 40 knots) is shown primarily to familiarize you with the low speed power requirements of the helicop-ter. It shows the power margin available for climb or accel-eration during maneuvers, such as NOE .ight. At zero air-speed, the torque represents the torque required to hover out of ground effect. In general, mission planning for low speed .ight should be based on hover out of ground effect.
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