Aircraft Performance

Outside air temperature Figure 11-22. Density altitude chart. 11-21 )teef dnasuoht( edutitla ytisned etamixorppA 15 14,000 14 13,000 13 12,000 e et) 28.0 1,824 12 11,000 altit u d e (f 2 2 8 8 . . 1 2 1 1 , , 7 6 2 3 7 0 11 10,000 Pr e s s ur e 2 2 8 8 . . 3 4 1 1 , , 5 4 3 3 3 6 10 S ta n 9,000 2 2 8 8 . . 5 6 1 1 , , 3 2 4 4 0 4 d 9 a r 28.7 1,148 d te m 8,000 28.8 1,053 8 p e 28.9 957 r a tu 7,000 29.0 863 r e 29.1 768 7 6,000 29.2 673 29.3 579 6 5,000 29.4 485 29.5 392 5 4,000 29.6 298 29.7 205 4 3,000 2 2 9 9 . . 8 9 11 20 2 3 2,000 2 3 9 0 . . 9 0 2 −73 0 2 el 30.1 −165 1,000 e a l e v 30.2 −257 S 1 30.3 −348 –1,000 3 3 0 0 . . 4 5 − − 4 5 4 3 0 1 S.L. C -18 -12° -7° -1° 4° 10° 16° 21° 27° 32° 38° 3 0.6 −622 30.7 −712 F 0° 10° 20° 30° 40° 50° 60° 70° 80° 90° 100° 30.8 −803 gnittes retemitlA )gH"( edutitla erusserP rotcaf noisrevnoc Sample Problem 3 Pressure Altitude...............................................3,000 feet OAT.........................................................................30 °C Takeoff Weight............................................2,400 pounds Headwind............................................................18 knots Refer to Figure 11-24. This chart is an example of a takeoff distance table for short-field takeoffs. For this table, first find the takeoff weight. Once at 2,400 pounds, begin reading from left to right across the table. The takeoff speed is in the second column and, in the third column under pressure altitude, find the pressure altitude of 3,000 feet. Carefully follow that line to the right until it is under the correct temperature column of 30 °C. The ground roll total reads 1,325 feet and the total required to clear a 50 foot obstacle is 2,480 feet. At this point, there is an 18 knot headwind. According to the notes section under point number two, decrease the distances by ten percent for each 9 knots of headwind. With an 18 knot headwind, it is necessary to decrease the distance by 20 percent. Multiply 1,325 feet by 20 percent (1,325 × .20 = 265), subtract the product from the total distance (1,325 – 265 = 1,060). Repeat this process for the total distance over a 50 foot obstacle. The ground roll distance is 1,060 feet and the total distance over a 50 foot obstacle is 1,984 feet. Climb and Cruise Charts Climb and cruise chart information is based on actual flight tests conducted in an aircraft of the same type. This information is extremely useful when planning a cross-country flight to predict the performance and fuel consumption of the aircraft. Manufacturers produce several different charts for climb and cruise performance. These charts include everything from fuel, time, and distance to climb to best power setting during cruise to cruise range performance. The first chart to check for climb performance is a fuel, time, and distance-to-climb chart. This chart gives the fuel amount used during the climb, the time it takes to accomplish the climb, and the ground distance that is covered during the climb. To use this chart, obtain the information for straight across to the third reference line and from here, draw the departing airport and for the cruise altitude. Using a line in two directions. First, draw a line straight across to Figure 11-25, calculate the fuel, time, and distance to climb figure the ground roll distance. Next, follow the diagonal lines based on the information provided. again until they reach the corresponding obstacle height. In this case, it is a 50 foot obstacle. Therefore, draw the diagonal Sample Problem 4 line to the far edge of the chart. This results in a 700 foot ground roll distance and a total distance of 1,400 feet over a Departing Airport Pressure Altitude.................6,000 feet 50 foot obstacle. To find the corresponding takeoff speeds Departing Airport OAT............................................25 °C at lift-off and over the 50 foot obstacle, refer to the table on Cruise Pressure Altitude..................................10,000 feet the top of the chart. In this case, the lift-off speed at 2,600 pounds would be 63 knots and over the 50 foot obstacle Cruise OAT..............................................................10 °C would be 68 knots.