Aircraft Performance

Figure 11-27. Cruise and range performance. 11-24 snoitidnoC setoN two sets of numbers from one another, but given the fact that Gross weight—2,300 lb. the numbers read zero at sea level, it is known that the time Standard conditions to climb from sea level to 8,000 feet is 10 minutes. It is also Zero wind Lean mixture known that 21 pounds of fuel is used and 20 NM is covered during the climb. However, the temperature is 22 °C, which is Maximum cruise is normally limited to 75% power. 7° above the standard temperature of 15 °C. The notes section of this chart indicate that the findings must be increased by ten 38 gal 48 gal ALT RPM % TAS GAL/ (no reserve) (no reserve) percent for each 7° above standard. Multiply the findings by BHP MPH Hour Endr. Range Endr. Range ten percent or .10 (10 × .10 = 1, 1 + 10 = 11 minutes). After hours miles hours miles 2,500 2,700 86 134 9.7 3.9 525 4.9 660 accounting for the additional ten percent, the findings should 2,600 79 129 8.6 4.4 570 5.6 720 2,500 72 123 7.8 4.9 600 6.2 760 read 11 minutes, 23.1 pounds of fuel, and 22 NM. Notice that 2,400 65 117 7.2 5.3 620 6.7 780 the fuel is reported in pounds of fuel, not gallons. Aviation 2,300 58 111 6.7 5.7 630 7.2 795 2,200 52 103 6.3 6.1 625 7.7 790 fuel weighs six pounds per gallon, so 23.1 pounds of fuel is 5,000 2,700 82 134 9.0 4.2 565 5.3 710 equal to 3.85 gallons of fuel (23.1 ÷ 6 = 3.85). 2,600 75 128 8.1 4.7 600 5.9 760 2,500 68 122 7.4 5.1 625 6.4 790 2,400 61 116 6.9 5.5 635 6.9 805 2,300 55 108 6.5 5.9 635 7.4 805 The next example is a cruise and range performance chart. 2,200 49 100 6.0 6.3 630 7.9 795 This type of table is designed to give TAS, fuel consumption, 7,500 2,700 78 133 8.4 4.5 600 5.7 755 endurance in hours, and range in miles at specific cruise 2,600 71 127 7.7 4.9 625 6.2 790 2,500 64 121 7.1 5.3 645 6.7 810 configurations. Use Figure 11-27 to determine the cruise and 2,400 58 113 6.7 5.7 645 7.2 820 2,300 52 105 6.2 6.1 640 7.7 810 range performance under the given conditions. 10,000 2,650 70 129 7.6 5.0 640 6.3 810 2,600 67 125 7.3 5.2 650 6.5 820 Sample Problem 6 2,500 61 118 6.9 5.5 655 7.0 830 2,400 55 110 6.4 5.9 650 7.5 825 2,300 49 100 6.0 6.3 635 8.0 800 Pressure Altitude...............................................5,000 feet RPM..................................................................2,400 rpm Fuel Carrying Capacity..................38 gallons, no reserve Another type of cruise chart is a best power mixture range graph. This graph gives the best range based on power Find 5,000 feet pressure altitude in the first column on the setting and altitude. Using Figure 11-29, find the range at left side of the table. Next, find the correct rpm of 2,400 65 percent power with and without a reserve based on the in the second column. Follow that line straight across and provided conditions. read the TAS of 116 mph and a fuel burn rate of 6.9 gallons per hour. As per the example, the aircraft is equipped with Sample Problem 8 a fuel carrying capacity of 38 gallons. Under this column, OAT....................................................................Standard read that the endurance in hours is 5.5 hours and the range in miles is 635 miles. Pressure Altitude...............................................5,000 feet Cruise power setting tables are useful when planning cross- First, move up the left side of the graph to 5,000 feet and country flights. The table gives the correct cruise power standard temperature. Follow the line straight across the settings, as well as the fuel flow and airspeed performance graph until it intersects the 65 percent line under both the numbers at that altitude and airspeed. reserve and no reserve categories. Draw a line straight down from both intersections to the bottom of the graph. At 65 Sample Problem 7 percent power with a reserve, the range is approximately 522 miles. At 65 percent power with no reserve, the range Pressure Altitude at Cruise................................6,000 feet should be 581 miles. OAT..................................................36 °F above standard The last cruise chart referenced is a cruise performance graph. Refer to Figure 11-28 for this sample problem. First, locate This graph is designed to tell the TAS performance of the the pressure altitude of 6,000 feet on the far left side of the airplane depending on the altitude, temperature, and power table. Follow that line across to the far right side of the table setting. Using Figure 11-30, find the TAS performance based under the 20 °C (or 36 °F) column. At 6,000 feet, the rpm on the given information. setting of 2,450 will maintain 65 percent continuous power at 21.0 "Hg with a fuel flow rate of 11.5 gallons per hour and airspeed of 161 knots.