Tail Rotor Shapes

[Vfrpilotpb]

It is said by many that most of the noise generated by any Helcopter comes from those fitted with the conventional type T/Rotor.

It looks like nothing new is hitting the markets,( with the exceptions of the NOTAR and FENESTRON) so it would seem that T/R noise will be around for quite some time yet, are any of the big manufacturers looking at the T/Rnoise problem or are we going to be using these designs for a long time into the future????

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The Fenestron is hardly new VFR, and in it's original guise on the Gazelle was hardly quiet - the whine from the Gaz fenestron is particularly irritating because all the TR noise is concentrated in a narrow frequency band. However, if you look at an EC135, you will see that the spaces between the (much bigger) fenestron blades are not equal which, I am told is an attempt to spread the TR noise across a wider frequency band. It clearly does work as the 135 is much, much quieter than the Gazelle.

[Thud_and_Blunder]

...and than the 117, which can be heard for miles on its occasional forays into the parts of Devon and Cornwall where this correspondent lurks. However, neither is as quiet to a listener on the ground as the 902 I hear over Brum when I'm off shift...:ok:

[PANews]

BUT....

The EC145, which is a sort of BK117C2 [and will be known in southern climes as the Kawasaki KB117C2] has retained a tail rotor.

Although it was expected to defect to a Fenestron in its new version it actually has a conventionally laid out tail rotor that appears to be as quiet as a Fenestron.

I haven't a clue how they did it but it just goes to show that all those noisy t/r types could be quietened if someone puts a mind to it.

The differences between the 135 and the 900 seem to depend on the day of the week, the humidity and the pilot ..... They are about equal overall. But the latter can be VERY VERY quiet sometimes ..... shhhhhhhh

Eurocopter claim they have in excess of 10,000,000 hours experience on the Fenestron boththe noisy ones and the quiet ones.

[handysnaks]

f**k**g h*ll....
Was that PANews saying something complimentary about the 902:eek:

[Lu Zuckerman]

Hughes helicopters did a research project for DARPA in order to develop a quiet helicopter. They created a waterbrake dynamometer that would allow the isolation of the various parts of the driveline. This isolated the noise generating components and mods were made to include a five blade main rotor and the scissors tail rotor. They also insulated and damped all of the metal structure keeping high frequency sound from being generated by the skin and structure. After doing this they installed a muffler on the engine and redesigned the air inlet to keep turbine noise from escaping.

When it was all done the helicopter could fly over at 500 feet and all you would hear is a low whoosh and nothing more. On completion of the contract the helicopter disappeared and everyone figured it ended up in Vietnam.

:E :E

[Notar fan]

Was that PANews saying something complimentary about the 902

It knocked me off the chair..........there is a wee bit of Christmas spirit in everyone

MERRY, MERRY CHRISTMAS, PANEWS :ok:

[Thud_and_Blunder]

I don't think PA was being complimentary - I think he thinks he's being funny 'cos he thinks the Exploder's a hangar queen...

Might be wrong though - it happened once before, in 1979. I thought I'd made a mistake, but I hadn't...