Sud Aviation SA-330 with Ducted-Fan Tail Rotor

[hesham]

Hi,

here is the Sud Aviation SA-330 helicopter model,with a ducted-fan
tail rotor.
http://www.flightglobal.com/pdfarchive/view/1964/1964 - 2089.html?search=ring tail projects

 

[Jemiba]

Good find Hesham !
Such a modification didn't remain a project, as can be seen in the
photo of SA 330Z, but in a different form, not with a high set
fenestron and a V-tail.
(from Minidocavia N°9)

 

[Stingray]

Good find Hesham !
Such a modification didn't remain a project, as can be seen in the
photo of SA 330Z, but in a different form, not with a high set
fenestron and a V-tail.
(from Minidocavia N°9)

Thanks, Jemiba. I've been looking for this modification for years.

 

[Jemiba]

Found another picture of the SA 330 with a ducted fan. Indeed, it was proposed
at first, but changed during development into a conventional tail rotor.
Reason behind was a higher cruising speed and better rough field landing capability.

(from AviationWeek April 1963)

 

[hesham]

From Aviation magazine 1975.

 

[Kiltonge]

From Aviation magazine 1975.

The SA.331 was to be the long-body Super Puma, with 332 to retain the original fuselage length. The long cabin was tested on 330B c/n 1541 F-WZAT which was stretched but retained the Turmo engines, as the sole SA.330R. Flew 05 September 1977.

The long-cabin model was paused in late 1977 pending the outcome of the 'Euttas' consortium, but Aerospatiale proceeded with the short-cabin 332. Eventually the longer cabin was introduced as the 332L model and the 331 designation was dropped.

 

[Aeroweanie]

Another picture of the A330Z

 

[Deltafan]

 

[Archibald]

Geez, now that's one hell of a fenestron !! Fenestron on steroids: megafenestron. Since fenestron comes from the word "fenêtre" (window) maybe they should have called it according to "bigger windows" - either "vasistas" (skylight) or "véranda" - so: vasistron ? véranstron ?

More seriously - why did they dropped it ? can't see any on Super Puma / EC-725 ? "law of diminishing returns", not worth it at larger scale ?

 

[persil]

More seriously - why did they dropped it ? can't see any on Super Puma / EC-725 ? "law of diminishing returns", not worth it at larger scale ?

I was once told (I think it was during mechanical type rating on EC135) that the Fenestron itself is rather heavy and helicopter which were not designed with it in mind since the beginning, but altered to incorporate the Fenestron (like EC135 vs. Bo108, or EC145T2 vs. Ec145/Bk117), they are usually tail-heavy. Not to mention that Fenestron itself has smaller diameter that the tail rotor - and even that the ducting bit should help, it seems to not help as much to make it equal to open tail rotor. So in the hover it sucks a bit more power than classic tail rotor. At the speed, there is no problem as it is solved aerodynamically - the entire vertical fin hiding the Fenestron counteracts the rotor torque.

Have I mention the noise? It is a personal preference, but in general it is a higher pitch noise than the classic tail rotor - for me personally the noise of the EC-135 Fenestron (1 m in diameter) is acceptable, but certainly not pleasant.

 

[hesham]

From Aviation Week.

 

[Scott Kenny]

Have I mention the noise? It is a personal preference, but in general it is a higher pitch noise than the classic tail rotor - for me personally the noise of the EC-135 Fenestron (1 m in diameter) is acceptable, but certainly not pleasant.

The higher pitch noise is also not audible from as far away. Plus it's easier to soundproof internally, though that does add weight.