7 Flight Mystery and Aerodynamic Principles
541
Fig. 7.133 An-225 multi-wheel multi-pillar main landing gear
The external noise of the aircraft mainly includes propulsion system noise,
airframe noise, and interference noise between the propulsion system and the
airframe, as shown in Fig. 7.138. Propulsion system noise, i.e., engine noise,
including fan noise, compressor/turbine noise, combustion noise, and jet
noise, is a dynamic noise, all of which are dynamic noise. The airframe noise
includes the lifting device and the landing gear noise, it and the interference
noise between the propulsion system and the airframe are all non-dynamic
noise.
With the use of a large bypass ratio turbofan engines and the effective
application of noise reduction technologies such as muffler nacelles and
V-shaped petal nozzles, the proportion of engine noise in overall noise is
decreasing. Especially in the landing stage of the aircraft, when the engine
is in a low power state, the lifting device and the landing gear are all open,
541
Fig. 7.133 An-225 multi-wheel multi-pillar main landing gear
The external noise of the aircraft mainly includes propulsion system noise,
airframe noise, and interference noise between the propulsion system and the
airframe, as shown in Fig. 7.138. Propulsion system noise, i.e., engine noise,
including fan noise, compressor/turbine noise, combustion noise, and jet
noise, is a dynamic noise, all of which are dynamic noise. The airframe noise
includes the lifting device and the landing gear noise, it and the interference
noise between the propulsion system and the airframe are all non-dynamic
noise.
With the use of a large bypass ratio turbofan engines and the effective
application of noise reduction technologies such as muffler nacelles and
V-shaped petal nozzles, the proportion of engine noise in overall noise is
decreasing. Especially in the landing stage of the aircraft, when the engine
is in a low power state, the lifting device and the landing gear are all open,