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T.O. GR1F16CJ11 A44Change 7 Loiter Time Available at 5000 feet MSL = 15 minutes (loiter at mach = 0.35, begin descent 13 nm from destination with 87 pounds fuel used in descent). Loiter Time Available Using Optimum Altitude = 16 minutes (MIL climb at 423 KIAS or optimum altitude mach number, whichever is less, to 10,000 feet, loiter at mach = 0.38, begin descent 24 nm from destination with 149 pounds fuel used in descent). Based on this information, a decision to divert to the nearby base would be prudent. Maximum holding time using all remaining fuel, optimum altitude, and an IDLE descent would yield only 16 minutes-too little. Even remaining at 5000 feet MSL, a range of 66 nm is available which would leave a small fuel reserve at the alternate base. Even more reserve fuel would remain if optimum altitude (30,000 feet) were used. If range and time available (which require a fuel reserve) are needed, find the range and time which would be available if the desired reserve were con sumed and deduct those values from range and time available for the total fuel on board. For instance, if 200 pounds reserve fuel had been required in the above problem, 26 nm would be deducted from the 66 nm range available by cruising at 5000 feet. The other range and times available would be adjusted in the same manner. However, note, for this sample prob lem, 50 nm is not obtainable with 200 pounds reserve. BEST CRUISE ALTITUDE FOR SHORT RANGE MISSION For short missions or mission legs, fuel consumption can be minimized by climbing to a lowerthanopti mum cruise altitude and descending on course. For distances of 250 nm or less, use of a lowerthanopti mum cruise altitude will result in lower overall fuel usage. Figure A45 contains information defining the best altitude to use for these short distances as a func tion of initial GW and distance. For distances greater than 250 nm, optimum cruise altitude should be used. Fuel consumption is given in figure A45 as a function of drag index for each initial GW and distance. Also provided in the chart is the range from destination at which to begin a penetration descent or maximum range descent. All data shown is based on beginning at sea level, climbing to the indicated altitude using MIL, cruising at optimum mach at the indicated alti tude to the descent point, and executing a penetration descent (300 KIAS, IDLE, and speedbrakes open) or maximum range descent (at schedule KIAS, IDLE, and with speedbrakes closed). MIL climb speed for any drag index may be obtained from Part 3 and opti mum KTAS for constant altitude cruise from the Sub sonic Cruise Tables. Further guidance to establish the climb and cruise conditions recommended in the Best Altitude for Short Range Mission chart is avail able through the FCC cruise energy management guidance system. Climb speed for most economical climb may be established through use of the CRUS HOM mode on the upfront control set. Climb speed guidance is displayed on the HUD speed scale (scales switch set to VV/VAH). Once at altitude, optimum cruise mach can be established by using the CAS, TAS, or GND speed guidance displayed on the HUD when the CRUS RNG mode is selected on the upfront control set. REFER TO FIGURE A45. Enter figure A45 with start climb GW (A), desired total mission range (B), and drag index (C). With these given conditions, read best cruise altitude (D), fuel consumed (E), and penetration descent range (F). SAMPLE PROBLEM. A. Start climb GW = 28,000 pounds B. Total mission range = 150 nm C. Drag index = 200 D. Best cruise altitude = 32,100 feet E. Fuel consumed = 1543 pounds F. Penetration descent range = 19.6 nm |