L1011 engine No 2

[Lee Tze Yen, Bob]

Don't know if this has been discussed before... if it has... please e-mail
me privately regarding the source of information.....

I am building a model of N31029 (the only L1011 painted in the new TWA
colours), and I noticed from my photo references that there is a small root
fairing just below the bottom No 2 engine nacelle lip.

I searched through all available photo references on the web, and I noticed
that some L1011s have this root fairing, while some do not, and it's not
according to some specific aircraft type pattern.

Can someone enlighten me as to which L1011s were fitted with them, and
which were not, and why???

Best regards

Lee Tze Yen, Bob
19/09/1999
2058h

[David Lednicer]

The fairing you are looking at is called a "Frisbee Fairing", named
after its developer. The fairing is designed to eliminate a flow
separation that occured in that area and in doing so, it reduces the
noise in the aft cabin. It was originally only fitted to L1011-500s.

The separation that it eliminates is caused by the relatively thick
boundary layer on the fuselage encountering a region of increasing
(adverse) pressure in front of the "pylon" below the #2 engine inlet.
Without the fairing, the adverse pressure gradient would be too steep
for the boundary layer to stay attached and it would separate, forming a
necklace vortex around the "pylon". The fairing makes the gradient less
steep and eliminates the separation and associated vortex.

-------------------------------------------------------------------
David Lednicer | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc. | email: da...@amiwest.com
2133 152nd Ave NE | tel: (206) 643-9090
Redmond, WA 98052 USA | fax: (206) 746-1299

[Pete Mellor]

David Lednicer <da...@amiwest.com> wrote on Tue Oct 5 12:41:55 1999:-

> The fairing you are looking at is called a "Frisbee Fairing", named

> after its developer. ...

Is there any connection with the famous circular throwing toy, or was
that named (as I have heard) after Ma Frisbee's pies (which "threw
better than they ate")? :-)

Pete Mellor
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[Trevor Fenn]

David Lednicer wrote:
> The fairing you are looking at is called a "Frisbee Fairing", named

> after its developer. The fairing is designed to eliminate a flow
> separation that occured in that area and in doing so, it reduces the
> noise in the aft cabin. It was originally only fitted to L1011-500s.
>
> The separation that it eliminates is caused by the relatively thick
> boundary layer on the fuselage encountering a region of increasing
> (adverse) pressure in front of the "pylon" below the #2 engine inlet.
> Without the fairing, the adverse pressure gradient would be too steep
> for the boundary layer to stay attached and it would separate, forming a
> necklace vortex around the "pylon". The fairing makes the gradient less
> steep and eliminates the separation and associated vortex.

Sounds good but if I recall correctly it is a Frakes Fairing.

Trevor Fenn

[David Lednicer]

Pete Mellor wrote:
> Is there any connection with the famous circular throwing toy, or was
> that named (as I have heard) after Ma Frisbee's pies (which "threw
> better than they ate")? :-)

Story I heard was that it was named after the aero guy at Lockheed who
thought up the fairing.

[Steven Nicolaou]

> Sounds good but if I recall correctly it is a Frakes Fairing.

According to "Giant Jetliners" by Guy Norris and Mark Wagner, it is in fact
called a "Frisbee Fairing" named after its designer, Lockheed chief engineer
Lloyd Frisbee. The fairing improved aerodynamic efficiency over earlier
models which suffered from air stagnating at the faring between the inlet
and the fuselage.

Steven.