Abstract :
In cruising conditions the aircraft is at a stable altitude. Generally, passenger
aircraft that use jet engines today roam between 25,000 ft ? 43,000 ft. At a certain
altitude, air has different densities and temperatures, which affect the performance
of aircraft engines. This has an impact on the specific fuel consumption of aircraft
engines. Therefore, it is very important to analyze the effect of altitude on the SFC
engine CFM56-7B26 in cruising conditions to find out how much influence altitude
has on engine performance, in this case the specific fuel consumption of the
CFM56-7B26 engine.
The method used in this study is the parametric cycle analysis of real engines
using the help of Mathcad software. Then analyze the specific fuel consumption
which has been affected by variations in temperature and air density values at
altitudes of 30,000 ft, 32,000 ft, 34,000 ft, 36,000 ft, and 38,000 ft to find out how
the performance is generated from the CFM56-7B2 engine.
Variation of the temperature value according to the flight altitude obtained
the lowest specific fuel consumption value at an altitude of 30,000 feet with a
temperature of 411.75 oR of 12.746 (lbm/h)/lbf and the highest specific fuel
consumption value at an altitude of 38,000 feet with a temperature of 389.97 oR of
14.039 (lbm/h)/lbf. And the variation in the air density value according to the
altitude, the lowest specific fuel consumption value was obtained at an altitude of
30,000 feet with an air density of 0.0007259 slug/ft3 of 10.459 (lbm/h)/lbf and the
highest specific fuel consumption value at an altitude of 38,000 feet with an air
density 0.0005258 slug/ft3 of 11.522 (lbm/h)/lbf. The higher the flying altitude, the
temperature and air density will decrease, causing the specific fuel consumption
value to increase.