Tail rotor design for noise
Tail rotor design for noise
(OP)
Wondering what design considerations there are for noise when making a tail rotor.
I see that speed is a big factor in this article on tail rotor design, but isn't there something with the airfoil or tip shape?
I see that speed is a big factor in this article on tail rotor design, but isn't there something with the airfoil or tip shape?
RE: Tail rotor design for noise
I can't say as to how I have ever noticed that a majority of sound emitted from the tail rotor - it is usually the powerplant and the main rotor downwash impingement on the fuselage, at least to my ear.
The biggest consideration, past plain aerodynamic efficiency and effectiveness, is that tail rotors offer an excellent thing to strike trees, power lines, careless people walking around them, and that this often leads to an immediate disassembly of much of the remainder of the helicopter, either from uncontrolled spinning, flipping over, or by smashing into the ground.
RE: Tail rotor design for noise
A bit on the Hughes 500P
https://medium.com/war-is-boring/the-cia-built-a-s...
RE: Tail rotor design for noise
RE: Tail rotor design for noise
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Tail rotor design for noise
I bet there is someone out there now considering creating a variable phase adjustment to create a spread-spectrum system.
RE: Tail rotor design for noise
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Tail rotor design for noise
RE: Tail rotor design for noise
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Tail rotor design for noise
A LOT of research and development goes into each decibel reduction coming from any machine... and machines with military implications expend even more capitol for the audible-stealth mode than for civilian operations/applications.
During the Vietnam war, the 'quietest' fixed and rotary wing aircraft ever built were used in 'stealth mode' for ultra-secretive [and still mostly classified] CIA missions. The missions flown have only partially been revealed after 4 decades… BUT the embedded technology/innovations have NEVER been declassified.
Having said all of this I am sure there are a few unclassified NASA and DOD reports for helicopter design for reduction of noise-exposure for the crew/pax and for exterior noise to come into 'environmental' compliance. There are likely other design guides for rotor-specific noise reductions...
Suggest starting with the basics for YOUR DESIGN... ANALYZE the noise signature of YOUR Tail Rotor Drive System [TRDS] mechanical components and then do the same for Your [now isolated] Tail Rotor System [TRS]driven by the TRDS... for starters... then test in-flight for the aft-fuselage and stabilizers contributions due to overall noise.
MIL-STD-1294 ACOUSTICAL NOISE LIMITS IN HELICOPTERS
MIL-STD-1474 DESIGN CRITERIA STANDARD NOISE LIMITS
It is then a matter of experimentation which leads to an analytical-modeling/understanding of YOUR TRS/TRDS/Structure... which can be driven mathematically to various conditions for noise analysis. Then TEST to verify the analytics of the combination of TRS and TRDS. Then refine Your design and thinking.
"Experience is a cruel teacher... First you take the test then learn the lesson." -Vern Law
"Nothing is a waste of time if you use the experience wisely." --Auguste Rodin
"Mistakes are the usual bridge between inexperience and wisdom."-- Phyllis Theroux
"Experience is one thing you can't get for nothing." -- Oscar Wilde
"Experience is a brutal teacher, but you learn. My God, do you learn." --C.S. Lewis
Regards, Wil Taylor
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o We believe to be true what we prefer to be true. [Unknown]
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