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Direct Lift Control  
User currently offlineMlsrar From United States of America, joined Mar 2000, 1417 posts, RR: 8
Posted (10 years 8 months 3 weeks 1 day 5 hours ago) and read 7764 times:

Having just read some interesting information about the Tristar's ability to take off with an essentially null AOA, I was also informed about the Direct-Lift-Control system. (It isn't too fresh at the moment, but I do believe that was the name of the system)

Does anyone have any information on whether or not this was a true asset to the technology of the Tristar, and, if so, was it incorporated into modern aircraft design?

Regards,

Mike


I mean, for the right price I’ll fight a lion. - Mike Tyson
31 replies: All unread, showing first 25:
 
User currently offlineTito From United States of America, joined Feb 2001, 125 posts, RR: 1
Reply 1, posted (10 years 8 months 3 weeks 1 day 1 hour ago) and read 7678 times:

I had an instructor who was a retired Tristar captain, and used to say in reference to flying airplanes, "when you push forward the nose goes down, when you pull back the nose comes up... except on the L-1011 that is..." He said it took some getting used to moving the yoke on approach and not effecting a pitch change but rather vertical rate.

this guy has a description:

http://flytristar.tripod.com/page/feature.html

-Tito


User currently offlineMlsrar From United States of America, joined Mar 2000, 1417 posts, RR: 8
Reply 2, posted (10 years 8 months 3 weeks 1 day ago) and read 7622 times:

Thanks Tito-

I was also wondering if the automated design was incorporated into modern design?



I mean, for the right price I’ll fight a lion. - Mike Tyson
User currently offline9VSIO From United Kingdom, joined Dec 2006, 708 posts, RR: 2
Reply 3, posted (5 years 1 month 1 day 17 hours ago) and read 7179 times:
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Hi y'all, sorry to dig up such an old thread, but is DLC still used on modern aircraft?


Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 4, posted (5 years 1 month 1 day 15 hours ago) and read 7152 times:



Quoting 9VSIO (Reply 3):
Hi y'all, sorry to dig up such an old thread, but is DLC still used on modern aircraft?

No, it is not. The L1011 was designed when noise regulation was just beginning.

The emphasis on noise reduction in today's environment makes it unwise to fly the approach with spoilers partially deflected. The additional drag means engine thrust (and noise) will be increased.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 5, posted (5 years 1 month 1 day 12 hours ago) and read 7127 times:



Quoting OldAeroGuy (Reply 4):
No, it is not. The L1011 was designed when noise regulation was just beginning.

The emphasis on noise reduction in today's environment makes it unwise to fly the approach with spoilers partially deflected. The additional drag means engine thrust (and noise) will be increased.

DLC has nothing to do with noise control. Its purpose is to allow vertical corrections to the glide slope to be accomplished without use of pitch control. When the flaps are lowered beyond 30 degrees the four inboard spoilers on each wing assume a new null point. Excursion above or below the glide slope will cause the spoilers to extend or retract bring the aircraft back to the glide slope. This is accomplish automatically through the Flight Controls Electronics Computer (FCES) and works in both autopilot and manual modes.

As for noise requirements: The L-1011 was designed to meet FAR Part 36 noise requirements. Those requirements were: Take off, Sideline and Approach were 106.2, 107.3 and 107.3 Decibels (EPNdB). The L-1011 was certified at 98.1, 97.8 and 102.4 respectively.


User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 6, posted (5 years 1 month 1 day 9 hours ago) and read 7075 times:

I would only add....

The L1011 was FAR 36 certified at all weights, unlike it other wide body competition.

DLC has operated without fail, just as advertised, in my nearly 30 years of flying this truly remarkable design.


User currently offline9VSIO From United Kingdom, joined Dec 2006, 708 posts, RR: 2
Reply 7, posted (5 years 4 weeks 17 hours ago) and read 6907 times:
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I only ask because I swore I saw minute deflections on the 773ER spoilers (without any noticeable roll change) while coming down on finals.

When I first read about DLC a while ago, I thought it was one of the most ingenious methods of adjusting the GP!



Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 8, posted (5 years 4 weeks 16 hours ago) and read 6887 times:



Quoting 9VSIO (Reply 7):
I thought it was one of the most ingenious methods of adjusting the GP!

It still is...and a Lockheed exclusive in the wide-body civil airliner world.


User currently offlineTWAL1011727 From United States of America, joined Mar 2006, 622 posts, RR: 0
Reply 9, posted (5 years 4 weeks 7 hours ago) and read 6847 times:



Quoting 474218 (Reply 5):
DLC has nothing to do with noise control. Its purpose is to allow vertical corrections to the glide slope to be accomplished without use of pitch control. When the flaps are lowered beyond 30 degrees the four inboard spoilers on each wing assume a new null point. Excursion above or below the glide slope will cause the spoilers to extend or retract bring the aircraft back to the glide slope. This is accomplish automatically through the Flight Controls Electronics Computer (FCES) and works in both autopilot and manual modes.

If I remember my dad (TWA L10 Capt) explaining it to me.
with the spoiler change came a slight pitch change.
To keep the deck angle constant through out the approach - pitch trim was also adjusted.

The L1011 was way ahead of its time. Too bad Rolls-Royce had troubles financially
and the L1011 was delayed ; otherwise, Douglas aircraft might have been forced out of
commercial aviation and not Lockheed

KD


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 10, posted (5 years 4 weeks 6 hours ago) and read 6834 times:



Quoting TWAL1011727 (Reply 9):
If I remember my dad (TWA L10 Capt) explaining it to me.
with the spoiler change came a slight pitch change.
To keep the deck angle constant through out the approach - pitch trim was also adjusted.

What TWA L10 Capt told you is partly true, but its the other way around. The horizontal stabilizer and DLC spoilers work together. When the DLC is armed (flaps lower than 30 degrees) any input to the horizontal stabilizer will cause the DLC spoilers to raise or lower to counteract this input.

If the aircraft is above the glide slope and either the automatic systems or the pilot attempts lower the aircraft nose, to bring the aircraft down to the glide slope, the DLC spoilers raise to counter this, keeping the pitch angle constant and lowering the aircraft to the glide slope. So while there is stabilizer movement is kept to a minimum.


User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 11, posted (5 years 4 weeks 6 hours ago) and read 6832 times:
AIRLINERS.NET CREW
DATABASE EDITOR

Is it true that the L-1011 is the only aircraft to have ever used DLC?

2H4



Intentionally Left Blank
User currently offlineKevinL1011 From United States of America, joined Mar 2005, 2964 posts, RR: 48
Reply 12, posted (5 years 3 weeks 6 days 23 hours ago) and read 6792 times:



Quoting 2H4 (Reply 11):
Is it true that the L-1011 is the only aircraft to have ever used DLC?

AFAIK it is. Lockheed referred to it as the "Flying Stabilizer". It was developed along with the CAT III auto-land system, another Tri-Star first.

Quoting 474218 (Reply 5):
When the flaps are lowered beyond 30 degrees the four inboard spoilers on each wing assume a new null point.

I believe it's 8 deg.

The 500 model was equipped with a Recovery Speed Brake (RSB) which deployed the spoilers at high speeds (Mach .85 plus) to improve stability as the 500 was a bit shorter with an extended wingspan.

The Tri-Star also introduced an Active Control System (ACS) which modified the outer aileron null point to compensate for wing flex.

Coincidentally, the first scheduled AFCS flight occurred on June 25th,1972, almost exactly 37 years ago. It was a TWA L-1011 flight from STL to LAX.

I dearly miss flying on Tri-Stars.



474218, Carl, You will be missed.
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 13, posted (5 years 3 weeks 6 days 14 hours ago) and read 6735 times:



Quoting KevinL1011 (Reply 12):
I believe it's 8 deg.

To activate DLC the flaps must be in the landing configuration ie: greater then 30 degrees.

Quoting KevinL1011 (Reply 12):
The 500 model was equipped with a Recovery Speed Brake (RSB) which deployed the spoilers at high speeds (Mach .85 plus) to improve stability as the 500 was a bit shorter with an extended wingspan.

Recovery Speed Brakes are only found of CAA certified L-1011-500's, British Airways -200's and aircraft modified by Service Bulletin 093-27-181 the Rapid Decent Modification.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (5 years 3 weeks 6 days 14 hours ago) and read 6730 times:



Quoting 2H4 (Reply 11):
Is it true that the L-1011 is the only aircraft to have ever used DLC?

It might be true that the L-1011 is the only commercial jet to use it, but it's not the only aircraft. The C-17 uses this too. I'm not sure if it's used to hold glideslope in the C-17, but it's used as part of the "flareless landing", I believe.

Tom.


User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 15, posted (5 years 3 weeks 6 days 12 hours ago) and read 6718 times:

I introduced DLC on a sketch aircraft named Turboliner some time ago.

http://i191.photobucket.com/albums/z...Turboliner28april.jpg?t=1246033147

IMO it could offer steeper more controlled, more comfortable approaches to places like London City.

http://www.youtube.com/watch?v=8hce7A4mluw

Maybe F14 had it too.


User currently offline9VSIO From United Kingdom, joined Dec 2006, 708 posts, RR: 2
Reply 16, posted (5 years 3 weeks 6 days 12 hours ago) and read 6707 times:
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Quoting 474218 (Reply 13):
Quoting KevinL1011 (Reply 12):
I believe it's 8 deg.

To activate DLC the flaps must be in the landing configuration ie: greater then 30 degrees.

I think he meant the null point for the spoilers?



Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 17, posted (5 years 3 weeks 6 days 11 hours ago) and read 6691 times:



Quoting 9VSIO (Reply 16):
I think he meant the null point for the spoilers?

He was still wrong: the null point is 7 degrees for all L-1011's except for the -500's which is 9 degrees.


User currently offlineKevinL1011 From United States of America, joined Mar 2005, 2964 posts, RR: 48
Reply 18, posted (5 years 3 weeks 6 days 8 hours ago) and read 6672 times:



Quoting 9VSIO (Reply 16):
I think he meant the null point for the spoilers?

Yes.

Quoting 474218 (Reply 13):
To activate DLC the flaps must be in the landing configuration ie: greater then 30 degrees.

And 2 of the 3 engines must be less than TO thrust or Auto Land.

Quoting 474218 (Reply 17):
the -500's which is 9 degrees.

I stand corrected.



474218, Carl, You will be missed.
User currently offlineDL_Mech From United States of America, joined Feb 2000, 1926 posts, RR: 9
Reply 19, posted (5 years 3 weeks 6 days 1 hour ago) and read 6629 times:

DLC can be seen in this video, beginning at 3:51.

http://www.youtube.com/watch?v=Vf2nFYHKGuU



This plane is built to withstand anything... except a bad pilot.
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 20, posted (5 years 3 weeks 5 days 13 hours ago) and read 6568 times:



Quoting 474218 (Reply 5):
As for noise requirements: The L-1011 was designed to meet FAR Part 36 noise requirements. Those requirements were: Take off, Sideline and Approach were 106.2, 107.3 and 107.3 Decibels (EPNdB). The L-1011 was certified at 98.1, 97.8 and 102.4 respectively.

The approach noise of the L-1011 was excellent when certified, but compare it to a 772LR today. At MLW, the 772LR is almost 3 EPNdB quieter (99.6 vs 102.4) while weighing 33% more (492,000 lb vs 368,000 lb).

Given that EPNdB is a log scale, a reduction of 3 dB equates to a halfing of the noise level.

While much of the noise reduction over the past 40 or so years has come from engine technology improvements such as higher bypass ratios and better acoustic treatments, airframe improvements have also played a role.

Wing aspect ratios have been increased and high lift systems have been simplified to reduce approach drag. Reduced approach drag means lower engine thrust and less engine noise. At the same time, high lift system improvments mean less airframe noise due to fewer flap edges and discontinuities.

Quoting 474218 (Reply 17):
the null point is 7 degrees for all L-1011's except for the -500's which is 9 degrees

Deflecting the spoilers by 7 to 9 degrees will increase approach noise due to increased drag (higher approach thrust) and higher airframe noise. This is why DLC is not commonly used on commercial airplanes today even though it's a great idea for tracking the glide slope.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineDash500 From Portugal, joined May 2005, 85 posts, RR: 0
Reply 21, posted (5 years 2 weeks 3 days 6 hours ago) and read 6280 times:



Quoting OldAeroGuy (Reply 20):
Deflecting the spoilers by 7 to 9 degrees will increase approach noise due to increased drag (higher approach thrust) and higher airframe noise. This is why DLC is not commonly used on commercial airplanes today even though it's a great idea for tracking the glide slope.

Nevertheless, even with DLC inducing more drag, the L-1011 was quieter than its rival  Smile



TriStar
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 22, posted (5 years 2 weeks 2 days 23 hours ago) and read 6241 times:



Quoting Dash500 (Reply 21):
Nevertheless, even with DLC inducing more drag, the L-1011 was quieter than its rival



Quoting Mlsrar (Thread starter):
Does anyone have any information on whether or not this was a true asset to the technology of the Tristar, and, if so, was it incorporated into modern aircraft design?

But what commercial airplane uses DLC today? That appears to one of the questions Mlsrar is asking. The answer is none and Approach noise is a primary reason for the lack of DLC airplanes.

The blow-in nacelle doors used on the 747-100 are not seen today either. Noise is a primary reason for this as well.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16991 posts, RR: 67
Reply 23, posted (5 years 2 weeks 2 days 18 hours ago) and read 6204 times:



Quoting OldAeroGuy (Reply 22):

The blow-in nacelle doors used on the 747-100 are not seen today either. Noise is a primary reason for this as well

Isn't there also the fact that intakes have more modern designs and don't need those doors?



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineOldAeroGuy From United States of America, joined Dec 2004, 3476 posts, RR: 67
Reply 24, posted (5 years 2 weeks 2 days 14 hours ago) and read 6168 times:



Quoting Starlionblue (Reply 23):
Isn't there also the fact that intakes have more modern designs and don't need those doors?

If blow-in doors were used, nacelle drag could be reduced for the cruising flight as the inlet lip could be made thinner. This is true even with today's engines.

A primary reason that blow-in doors are no longer used is the acoustic treatment that is applied in the nacelle inlet. Blow-in doors would preclude the use of this noise reducing material.



Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
25 474218 : DLC will not function correctly without the flying stabilizer as the DLC spoilers and the stabilizer work unison's. Since no other airlines uses the
26 OldAeroGuy : Elevators will accommodate DLC quite well, particularly with FBW. You don't need a flying stab. Read up on the A380 development history with respect
27 Phollingsworth : The killer with QC is that it puts weight back in the equation by using absolute certification levels as the basis for the quota count. You can tell
28 Dash500 : I still don't get why you insist with this. L-1011 has DLC. B747-100/B747-200 and DC-10 don't. However the L-1011 was still quieter. It certainly was
29 OldAeroGuy : Because it's an accurate assessment of why no modern airliners use DLC? If you don't think so, please explain why modern airliners don't use DLC. Imp
30 474218 : I suggest you read FAA Advisory Curricular No. 36-1H, which lists the noise levels for all FAA certified aircraft. On page 45 it lists all models the
31 411A : Quite correct, 474218. I find it rather strange that a few folks who normally wouldn't know an L1011 from the back end of a bus...seem to 'know' so mu
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