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The AH-64 Apache attack helicopter was upgraded several times after its first flight in 1974. The Apache Longbow was a major upgrade which entered service in 2003. On the other hand, Agusta A-129's first flight was in 1983.

I have two questions:

  1. Why does AH-64D have much high rotor noise? Why wasn't there any effort to suppress the noise in the upgraded versions?
  2. Why does A-129 have lower rotor noise (i.e. the chop chop sound is almost absent) even though its tail rotor isn't covered?
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    $\begingroup$ For what it's worth you're comparing apples to oranges - the Apache is roughly twice as powerful (with twice the payload) as the Mangusta, and it's about 50% larger in most meaningful specifications. Also, comparing two youtube videos is about as unscientific as you can get from a noise standpoint - different microphones, different environments, etc. $\endgroup$ – egid Apr 11 '18 at 5:54
  • $\begingroup$ @egid - if indeed the engines are as you say, then that serves as an answer and I'd recommend posting one. Noise is directly proportional to thrust / rotor lift after all. $\endgroup$ – ymb1 Apr 11 '18 at 8:28
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Because they are very different helicopters, as egid already pointed out.

  • The Apache is twice as heavy as the Mangusta (5165 kg vs 2530 kg empty)
  • The rotor diameter is also bigger accordingly (14.6 m vs 11.9 m)

A Chinook transport will make more noise than an Apache. An Apache will make more noise than a Mangusta. Different helicopters and different weights that have to be kept airborne.

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