TM 1-1520-240-107-7-1SECTION VII. CRUISE7-7-1. Description.The cruise charts, figures 7-7-1 through 7-7-84, presenttorque requirements and fuel flow for cruise flight as afunction of airspeed and gross weight for various com-binations of pressure altitude and free air temperature.Dot pattern (shaded) area indicates time limited opera-tion.7-7-2. Use of Charts.The primary use of charts is illustrated by the examplecruise chart (fig. 7-7-1). To use the charts it is usuallynecessary to know the planned PA, estimated FAT,planned cruise TAS, and the GW. First select the properchart based on PA and free air temperature. Enter thechart at the cruise TAS, move right and read IAS, moveleft to the GW, move down and read torque required, thenmove up and read associated fuel flow. Maximum perfor-mance conditions are determined by entering the chartwhere the maximum range line or maximum enduranceand rate of climb (R/C) line intersect the gross weightline: then read airspeed, fuel flow, and torque required.Normally, sufficient accuracy can be obtained by select-ing the chart nearest to the planned cruising altitude andFAT, or move conservatively, by selecting the chart withthe next higher altitude and FAT (example cruise chart,method one). If greater accuracy is required, interpola-tion between altitudes and/or temperatures is permissi-ble (example cruise chart, method two). To be conserva-tive, use the GW at the beginning of the cruise flight. Forimproved accuracy or long flights, it is preferable to deter-mine cruise information for several flight segments toallow for decreasing GW.a. Airspeed. True and indicated airspeeds arepresented at opposite sides of each chart. On any chart,IAS can be directly converted to TAS (or vice versa) byreading directly across the chart without regard to otherchart information. Estimated airspeed limits with anoperatingCGI appear as dashed lines on each chart.Airspeed limits with the CGI inoperative are presentedin the airspeed limits section of Chapter 5.NOTEAirspeed limitations with an operative cruiseguide indicator are per the indicator display.Estimated values shown on these cruisecharts are for information only, as an aid topre–flight planning.b. Torque. Since PA and temperature are defined foreach chart, torque required varies only with GW andairspeed. The torque required per engine as presentedon the charts is for dual engine operation. The torquerequired for single engine operation is double the dualengine torque value for any given condition. See cruisechart example 2 for example on torque required. WithEAPS installed there is no significant change in torquerequired. The torque available limits shown are eithertransmission or engine torque limits (whichever is least).c. Fuel Flow. The fuel flow scales presented on eachchart opposite the torque scales are for dual engineoperation. Torque may be converted directly to fuel flowon any chart without regard to other chart information. Asingle engine fuel flow chart is presented in Section X.Torque required for any given condition as obtained fromthe preceding cruise charts should be doubled beforebeing used to obtain single engine fuel flow from thischart.d. Maximum Range. Maximum range lines indicateoptimum GW/cruise speed conditions with respect todistance covered per pound of fuel consumed for zerowind condition.e. Maximum Endurance and Rate of Climb. Maxi-mum endurance and rate of climb lines indicate opti-mum GW / cruise speed conditions for maximumendurance and maximum rate of climb. These condi-tions require minimum fuel flow (maximum endurance)and provide maximum torque change for climb (maxi-mum rate of climb). This airspeed also represents thebest single engine airspeed.7-7-3. Conditions.The cruise charts are based on 100% RRPM for ambienttemperatures of –10_Cand above, and 98% and 100%RRPM for ambient temperatures of –20_C and below.7-7-4. Performance Penalties with EAPS.The engine performance loss with EAPS installed isshown in table 7-7-1. The corrections shown in the tableare to be applied to the applicable to the applicable per-formance data shown on Chapter 7.
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