FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesEasy
A high-bypass turbofan engine's inlet duct and fan cowl are lined with perforated honeycomb acoustic panels. What is the primary purpose of these panels?
- ATo reduce the overall weight of the nacelle structure
- BTo absorb sound energy generated by the fan, reducing engine noise
- CTo smooth airflow and eliminate compressor stalls
- DTo prevent ice accumulation on the inlet lip
Show answer & explanationAnswer & explanation
Correct answer: B. To absorb sound energy generated by the fan, reducing engine noise
Acoustic treatment panels, consisting of a perforated facesheet bonded to a honeycomb core, are installed in the inlet and fan duct to absorb sound energy produced primarily by the fan. This significantly reduces the noise radiated from the engine, helping meet noise certification requirements.
Why the other options are wrong
- A. Weight is a secondary consideration; the panels are added specifically for noise attenuation.
- C. Compressor stalls are addressed by bleed valves and variable stators, not acoustic treatment.
- D. Ice protection is provided by separate anti-ice bleed air systems, not acoustic panels.
Acoustic Treatment (Nacelle Noise Suppression)
Perforated honeycomb panels lining the fan inlet and duct that absorb sound energy to reduce turbofan engine noise.
- Targets fan noise, the dominant noise source in high-bypass engines
- Consists of a perforated facesheet over honeycomb core
- Helps meet FAA/ICAO noise certification standards
Memory trick: Honeycomb panels are noise 'sponges' soaking up fan racket.