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L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 1:28 am
by USAviator
Hello everyone,

I have searched and searched but I can't seem to find an answer to this question....

Why do some L1011's have a different shape underneath the inlet of engine #2?

For example, some L1011's have a clean, straight cutaway from the fuselage to engine #2, yet, other L1011's seem to have the fuselage curve upwards and blend into inlet #2... I attached some photos with some different L1011's below.

I don't know if I explained this well enough, but hopefully after seeing the photos, you can kind of tell what I am trying to convey :D The first two pictures show the fuselage blending to the inlet #2 while the last three pictures show the "clean" cut from inlet #2.

Many thanks!

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Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 1:35 am
by mga707
Going from memory, not checking reference books, that streamlined fairing in front of the #2 engine was a design change on the L-1011-500 series for improved fuel economy. So all -500s have it. Lockheed then offered it as a retrofit for earlier models. Some airlines retrofitted their 'standard' L-1011s, most did not. The Delta photo is a -500, the TWA photo below it shows one of their earlier L10s (TWA had no -500s) with the modification.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 1:40 am
by USAviator
mga707 wrote:
Going from memory, not checking reference books, that streamlined fairing in front of the #2 engine was a design change on the L-1011-500 series for improved fuel economy. So all -500s have it. Lockheed then offered it as a retrofit for earlier models. Some airlines retrofitted their 'standard' L-1011s, most did not. The Delta photo is a -500, the TWA photo below it shows one of their earlier L10s (TWA had no -500s) with the modification.


Thank you so much! I knew someone on this website would know something about it... Just another thing I know now. Thanks!

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 1:41 am
by B757Forever
Delta also did a "250" mod to some of their -100s which added this feature.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 2:51 am
by 325i
Hi US Aviator,good questionQuoted from Airliner Tech (Volume 8 on the Tristar)
"a diverter fairing called the Frisbee fairing was made to the inlet duct for the number 2 engine.
A significant noise reduction in the aft cabin area was accomplished by changing the airflow.
This was offered as an option on all models of the L-1011.
Should you be ,as I am, a L-!011 fan I recommend you purchase this publication.
Printed in 2001.
Kind regards, 325i.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 4:27 am
by JettNC
As a side note, The EAL Tristar photo of ship 310, shown in an earlier post was the L1011 that crashed into the Everglades on 12/29/1972 on a flight from JFK to MIA. It was the subject of books and two TV movies, The Ghost of Flight 401.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 4:52 am
by AWACSooner
There’s all the correct answers above...but then there’s the REAL answer below:
So Lockheed could claim the title of “sexiest airplane EVER designed.” ;)

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 5:36 am
by Moose135
325i wrote:
a diverter fairing called the Frisbee fairing was made to the inlet duct for the number 2 engine.

And for the record, it was named for the engineer who developed it, not the flying disc toy.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 7:23 am
by Ty134A
AWACSooner wrote:
There’s all the correct answers above...but then there’s the REAL answer below:
So Lockheed could claim the title of “sexiest airplane EVER designed.” ;)


Unfortunately Lockheed only takes third place in this ranking, with IL-86 and TU-134 ranking first.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 10:37 am
by Max Q
AWACSooner wrote:
There’s all the correct answers above...but then there’s the REAL answer below:
So Lockheed could claim the title of “sexiest airplane EVER designed.” ;)



Correct in every respect !

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 1:50 pm
by WesternDC6B
I’d sure like to fly on one again. The aircraft itself was very impressive, and like virtually every other Lockheed airliner, radiated “classy!”. I also want to fly on one again because when they were in main line service, passengers were not yet cattle: you actually had a bit of legroom in coach.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 4:42 pm
by kurtverbose
WesternDC6B wrote:
I’d sure like to fly on one again.


I flew on one when I was a kid. Out of Kuwait. It had engine failure and diverted. Spent the night in an horrible hotel with awful food.

I still really like the plane though.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 7:52 pm
by Tristarsteve
When I worked for Gulf Air in Bahrain, we received our first Tristar with a frisbee fairing. We managed to convince one of our engineers that it moved and had an actuator. He got out the manlift and climbed into the S duct to look for the access panel.

That picture of the BEA Tristar was taken at the Farnborough airshow in London. (1973?) Lockheed painted up an Eastern aircraft before delivery to show it off. When the Tristars were delivered, BEA had become British Airways, so those colours only lasted a week.

Re: L1011 Question About a Small Detail

Posted: Wed Nov 13, 2019 8:58 pm
by BravoOne
Flown that Delta -500 a few times. Sweet airplane for sure.

Re: L1011 Question About a Small Detail

Posted: Thu Nov 14, 2019 4:13 am
by Max Q
That ‘frisbee’ fairing makes a great looking aircraft even more attractive,
the carefully sculpted smooth aerodynamic curves and the way it all blends together in the tail area is a work of art, the L1011 makes the DC10 look positively agricultural


Don’t understand why it’s called a ‘frisbee’ fairing though !

Re: L1011 Question About a Small Detail

Posted: Thu Nov 14, 2019 4:43 am
by WesternDC6B
Max Q wrote:
That ‘frisbee’ fairing makes a great looking aircraft even more attractive,
the carefully sculpted smooth aerodynamic curves and the way it all blends together in the tail area is a work of art, the L1011 makes the DC10 look positively agricultural


Don’t understand why it’s called a ‘frisbee’ fairing though !


Named after an engineer. See above.

As for the DC-10: I’ll get nailed for this, but, here goes: it looks cobbled up. “We can’t get it off the ground, glue on an extra engine, and try again.” It’s just not an attractive aircraft at all.

Re: L1011 Question About a Small Detail

Posted: Thu Nov 14, 2019 7:53 am
by Max Q
WesternDC6B wrote:
Max Q wrote:
That ‘frisbee’ fairing makes a great looking aircraft even more attractive,
the carefully sculpted smooth aerodynamic curves and the way it all blends together in the tail area is a work of art, the L1011 makes the DC10 look positively agricultural


Don’t understand why it’s called a ‘frisbee’ fairing though !


Named after an engineer. See above.

As for the DC-10: I’ll get nailed for this, but, here goes: it looks cobbled up. “We can’t get it off the ground, glue on an extra engine, and try again.” It’s just not an attractive aircraft at all.


Agree,

The vertical tail and #2 engine installation looks all wrong and the rudder is too small


Indeed DC had to install the wing engines much closer to the fuselage than the L1011 and install a double hinged rudder to provide enough yaw authority in the engine out case

Re: L1011 Question About a Small Detail

Posted: Thu Nov 14, 2019 11:28 am
by slcguy
Just a little clarification on which aircraft had the Frisbee fairing. As stated before it was introduced on the -500 in 1979. It became standard on all versions after that in the last few years of the production run.
An example is Delta, the final ten -1s starting with ship 730 delivered in 1980 had it. The last 6 of which were converted to -250s. It was also available to be retrofitted to older aircraft. Most airlines didn't modify their aircraft but a few did. TWA being a notable example, while a lot of their fleet was older and were not delivered with the fairing, they ended up retrofitting most if not all of their fleet by the late 1980s.

Re: L1011 Question About a Small Detail

Posted: Thu Nov 14, 2019 12:08 pm
by Leej
About the size of the fairing - is it just a kind of cone beneath the inlet, or is it faired all the way back to the tail either side (and below) the intake? The picture of the TWA bird kind of shows it is quite sizeable.

Re: L1011 Question About a Small Detail

Posted: Fri Nov 15, 2019 8:58 am
by Max Q
Leej wrote:
About the size of the fairing - is it just a kind of cone beneath the inlet, or is it faired all the way back to the tail either side (and below) the intake? The picture of the TWA bird kind of shows it is quite sizeable.



It’s just the vertical fairing that starts from the bottom of the #2 engine cowling angling forward and down until it intersects with the top of the fuselage

Re: L1011 Question About a Small Detail

Posted: Fri Nov 15, 2019 5:37 pm
by Kno
WesternDC6B wrote:
Max Q wrote:
That ‘frisbee’ fairing makes a great looking aircraft even more attractive,
the carefully sculpted smooth aerodynamic curves and the way it all blends together in the tail area is a work of art, the L1011 makes the DC10 look positively agricultural


Don’t understand why it’s called a ‘frisbee’ fairing though !


Named after an engineer. See above.

As for the DC-10: I’ll get nailed for this, but, here goes: it looks cobbled up. “We can’t get it off the ground, glue on an extra engine, and try again.” It’s just not an attractive aircraft at all.


I might be in the minority but I actually think the DC10 is a far better looking plane than the l1011 - something about the shape of the L1011s nose looks awkward to me.

Re: L1011 Question About a Small Detail

Posted: Fri Nov 15, 2019 8:14 pm
by GalaxyFlyer
Something about flat pane windows; cobbled up tail engine design and appalling accident history makes the DC-10 ugly to me.

Re: L1011 Question About a Small Detail

Posted: Fri Nov 15, 2019 8:17 pm
by ExpatVet
kurtverbose wrote:
WesternDC6B wrote:
I’d sure like to fly on one again.


I flew on one when I was a kid. Out of Kuwait. It had engine failure and diverted. Spent the night in an horrible hotel with awful food.

I still really like the plane though.


I remember walking out to the TriStars as a kid at the old Dhahran International airport. Good times!

Re: L1011 Question About a Small Detail

Posted: Sat Nov 16, 2019 5:10 am
by Max Q
GalaxyFlyer wrote:
Something about flat pane windows; cobbled up tail engine design and appalling accident history makes the DC-10 ugly to me.



People forget how unsafe the 10 was until they finally addressed its design shortcomings, the AA accident in Chicago is often blamed on poor maintenance procedures but thats only part of the story


DC never incorporated a lock out to prevent asymmetric slat retraction unlike the L1011 so after the engine departed the aircraft the left slat retracted instantly stalling that wing


But for that the aircraft would have been saved.

Re: L1011 Question About a Small Detail

Posted: Sat Nov 16, 2019 9:01 pm
by DocLightning
When you have a protrusion sticking straight up out of a surface over which air flows, an interference vortex called a "horseshoe vortex" will form around the base of that protrusion.

Image

The tailfin of the L-1011 had a really large protrusion due to the S duct that probably caused a huge horseshoe vortex. That fairing likely reduced the magnitude and violence of that vortex, reducing cabin noise and overall drag.

Re: L1011 Question About a Small Detail

Posted: Sun Nov 17, 2019 5:35 pm
by asr0dzjq
AWACSooner wrote:
So Lockheed could claim the title of “sexiest airplane EVER designed.” ;)

Laughs in 747

Re: L1011 Question About a Small Detail

Posted: Tue Nov 19, 2019 2:01 pm
by Leej
DocLightning wrote:
When you have a protrusion sticking straight up out of a surface over which air flows, an interference vortex called a "horseshoe vortex" will form around the base of that protrusion.

Image

The tailfin of the L-1011 had a really large protrusion due to the S duct that probably caused a huge horseshoe vortex. That fairing likely reduced the magnitude and violence of that vortex, reducing cabin noise and overall drag.


I wonder if Boeing ever tried something similar with the 727?

Re: L1011 Question About a Small Detail

Posted: Wed Nov 20, 2019 7:58 am
by Max Q
Leej wrote:
DocLightning wrote:
When you have a protrusion sticking straight up out of a surface over which air flows, an interference vortex called a "horseshoe vortex" will form around the base of that protrusion.

Image

The tailfin of the L-1011 had a really large protrusion due to the S duct that probably caused a huge horseshoe vortex. That fairing likely reduced the magnitude and violence of that vortex, reducing cabin noise and overall drag.


I wonder if Boeing ever tried something similar with the 727?



No, slightly off topic though they did change the intake shape from oval to round on the #2 engine when they transitioned from the -100 to the -200 series


Supposed to provide better aerodynamics and airflow to that engine

Re: L1011 Question About a Small Detail

Posted: Thu Nov 21, 2019 1:37 am
by dlednicer
Leej wrote:
DocLightning wrote:
When you have a protrusion sticking straight up out of a surface over which air flows, an interference vortex called a "horseshoe vortex" will form around the base of that protrusion.

Image

The tailfin of the L-1011 had a really large protrusion due to the S duct that probably caused a huge horseshoe vortex. That fairing likely reduced the magnitude and violence of that vortex, reducing cabin noise and overall drag.


I wonder if Boeing ever tried something similar with the 727?


I proposed it to Valsan for the 727RE, but was told that the cost/benefit ratio wasn't very good.

BTW, we often call this a "necklace vortex". Navier-Stokes CFD analyses have the ability to resolve them. I've seen them, one place or another, on almost every aircraft type I've run in CFD.

Re: L1011 Question About a Small Detail

Posted: Thu Nov 21, 2019 4:18 pm
by DarkSnowyNight
Kno wrote:
WesternDC6B wrote:
Max Q wrote:
That ‘frisbee’ fairing makes a great looking aircraft even more attractive,
the carefully sculpted smooth aerodynamic curves and the way it all blends together in the tail area is a work of art, the L1011 makes the DC10 look positively agricultural


Don’t understand why it’s called a ‘frisbee’ fairing though !


Named after an engineer. See above.

As for the DC-10: I’ll get nailed for this, but, here goes: it looks cobbled up. “We can’t get it off the ground, glue on an extra engine, and try again.” It’s just not an attractive aircraft at all.


I might be in the minority but I actually think the DC10 is a far better looking plane than the l1011 - something about the shape of the L1011s nose looks awkward to me.



Objectively, the L1011 was superior in almost every way.

But I have to agree about the looks. I do not get where this 'Sexy' is meant to come from. I always think of a Sea Otter wearing a Top Hat when I see one. Not ugly, but not Sexy, neither.

Re: L1011 Question About a Small Detail

Posted: Thu Nov 21, 2019 5:42 pm
by Kno
the looks of the l1011 always gave me a minivan vibe where as the dc10 gives me more of a ford bronco vibe.

Re: L1011 Question About a Small Detail

Posted: Fri Nov 22, 2019 8:25 am
by Max Q
DarkSnowyNight wrote:
Kno wrote:
WesternDC6B wrote:

Named after an engineer. See above.

As for the DC-10: I’ll get nailed for this, but, here goes: it looks cobbled up. “We can’t get it off the ground, glue on an extra engine, and try again.” It’s just not an attractive aircraft at all.


I might be in the minority but I actually think the DC10 is a far better looking plane than the l1011 - something about the shape of the L1011s nose looks awkward to me.



Objectively, the L1011 was superior in almost every way.

But I have to agree about the looks. I do not get where this 'Sexy' is meant to come from. I always think of a Sea Otter wearing a Top Hat when I see one. Not ugly, but not Sexy, neither.



Agree,

What I see when I look at an L1011 is refined, beautifully crafted and advanced sophistication


The DC10, while not ugly looks agricultural and crude in comparison