Tristar's Direct Lift Control
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Tristar's Direct Lift Control
Any (ex) Tristar pilot would enlighten us on Direct Lift Control (spoilers deploying and retracting to maintain the glide path, rather than changing pitch)?
Is it easier-nicer-more accurate or what?
That would be nice! Thanks
LEM
Is it easier-nicer-more accurate or what?
That would be nice! Thanks
LEM
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I had 5000 hrs plus on the Tristar, albeit as a flight engineer. DLC was akin to speedbrakes on a glider, if you are familiar with that, except it was automatic. Supposed to have been the ants pants of approach and landing design but still experienced the hardest landings at times, of my entire flying career.
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PFM...
Some of the spoiler panels moved to a null position (7 degrees) when the flaphandle was moved past the 30 degree position.
Forward pressure on the pole resulted in spoiler extension (to a max of 14 degrees), whereas aft pressure on said pole resulted in spoilers retracting.
Worked OK, for the very finest in automatic approach/landings.
Required a definate technique for manual flying.
As some found out, the Boeing 'push' did not work.
Forward pressure on the pole resulted in spoiler extension (to a max of 14 degrees), whereas aft pressure on said pole resulted in spoilers retracting.
Worked OK, for the very finest in automatic approach/landings.
Required a definate technique for manual flying.
As some found out, the Boeing 'push' did not work.
LEM
HD and 411A have answered your query but whilst cleaning out my old computer the other day I found an old file which may be of use if you have a broader interest in the Tristar....
All of the flight controls on the Tristar are hydraulically actuated and none has any form of manual reversion. This simply means that, in the event of the failure of all hydraulic systems, the aeroplane would be completely uncontrollable. Before you blacklist all airlines flying Tristars, remember that the flight crews are all made well aware of this fact during their conversion and that they are all only too happy to operate the aeroplane. Prior to going on to the hydraulic actuation of these controls, and all of the rest of the hydraulic services, I will briefly run through these flight controls with particular reference to those that may not be quite so familiar to all of us.
Pitch control is maintained by the use of an all flying tailplane to which is attached a relatively normal elevator. They move in conjunction, and the elevator is mechanically linked to the tailplane. Control is by two servos and if either jams it can be disconnected. Trim is automatic and is achieved by the positioning of both surfaces Each time trim is used the control column takes up a new neutral position. The rate of movement of the trim is automatically varied for different speeds.
The rudder is reasonably conventional and incorporates a yaw damper whose purpose is to help eliminate "Dutch Roll". A series of "stops", which are actuated by speed sensitive switches, automatically limits arc of travel of the rudder in various conditions of flight.
Most jet airliners are equipped with two ailerons on each wing and the norm has been for the outboard aileron to be automatically locked central at high speed. The Tri Star differs in that all ailerons are operating at all stages of the flight. Extra control in the rolling plane at slow speed is needed and is provided by differential operation of the spoilers.
Six spoilers are fitted to each wing and their functions are many and wonderous to behold. They operate in a multitude of combinations to achieve these functions which are as follows:-Speed Brakes (at any time in the flight), Roll control assistance (when flap is extended), Lift control (on approach), and automatic extension after landing. When spoiler extension is demanded the aircraft decides which ones will extend and which ones will not. To make these decisions it gathers information from a series of speed sensitive switches, flap position indicating switches, Throttle position switches, and "squat" switches on each of the three U/C. legs.
Four double-slotted Fowler flaps are fitted to the trailing edges of the wings and alternate between the spoilers, while there are seven slats, or leading edge flaps, fitted to each wing. The slats go out with the first extension of the flaps (3 degrees), and are responsible for the very marked difference in the stall, and approach, speeds when either flapped or clean.
Hydraulic Systems.
There are four hydraulic systems in the Tristar. They are completely independent of each other. Each has is own reservoir and pressure source, and a loss of fluid in one will not affect any other. Pressure is provided by E.D.P.'s, P.T.U.'s, A.T.M.'s , electrically powered pumps and a R.A.T.
"A" System is powered by an E.D.P. on No. 1 engine and has, as an alternate power source, a PTU from System "B".
"B" System is powered by an E.D.P. on No. 2 engine and, as alternate power source, has an A.T.M. and an electric pump,
"C" System is exactly similar to "B" System but in addition may be powere by the R.A.T.
"D" System is exactly similar to "A" System.
The RAT is extended automatically when needed, and can be manually extended on the ground. It is normally "pinned", for safety reasons, when the aircraft is on the ground.
The most important hydraulically operated services are the flight controls and each of them is supplied with a multitude of alternate pressure sources, either by extra jacks to the same control surface or to mated surfaces (ie spoilers). There are two independent sets of wheel brakes. U/C. can be free falled, and flaps can be done without .
Flight Director/Auto Pilot, Area Navigation, & Auto Land.
Equipment includes, two Auto Pilots. two Flight Directors. three computors, two Inertial Nav. Systems and two VORTAC's.
The information used by the autopilot is the same as used by the corresponding flight director. Only one autopilot may be operated at a time, except in "Autoland" mode, but the flight directors may be operated in conjunction or independently and either automatically or by manual input. The third nav. computor monitors the other two at all times and any one of the three that is "odd man out" is automatically discarded. VORTAC stations are automatically tuned as the a/c. moves along track. As an alternate to automatic navigation the autopilot in use may be manually controlled
Movement along track may be monitored on a C.R.T. type display, a complete sector flight plan may be fed into the computer, automatic interceptions of VOR radials and ILS's can be made, an auto throttle is fitted, and either height or speed may be maintained.
Auto landings are available wherever there is a suitable ILS. Interception of both the ILS and the G/S. are automatic. A "Go Around" facility is incorporated, it is armed when flap in excess of 33 degrees is selected and it is activated when a button is pressed.
HD and 411A have answered your query but whilst cleaning out my old computer the other day I found an old file which may be of use if you have a broader interest in the Tristar....
All of the flight controls on the Tristar are hydraulically actuated and none has any form of manual reversion. This simply means that, in the event of the failure of all hydraulic systems, the aeroplane would be completely uncontrollable. Before you blacklist all airlines flying Tristars, remember that the flight crews are all made well aware of this fact during their conversion and that they are all only too happy to operate the aeroplane. Prior to going on to the hydraulic actuation of these controls, and all of the rest of the hydraulic services, I will briefly run through these flight controls with particular reference to those that may not be quite so familiar to all of us.
Pitch control is maintained by the use of an all flying tailplane to which is attached a relatively normal elevator. They move in conjunction, and the elevator is mechanically linked to the tailplane. Control is by two servos and if either jams it can be disconnected. Trim is automatic and is achieved by the positioning of both surfaces Each time trim is used the control column takes up a new neutral position. The rate of movement of the trim is automatically varied for different speeds.
The rudder is reasonably conventional and incorporates a yaw damper whose purpose is to help eliminate "Dutch Roll". A series of "stops", which are actuated by speed sensitive switches, automatically limits arc of travel of the rudder in various conditions of flight.
Most jet airliners are equipped with two ailerons on each wing and the norm has been for the outboard aileron to be automatically locked central at high speed. The Tri Star differs in that all ailerons are operating at all stages of the flight. Extra control in the rolling plane at slow speed is needed and is provided by differential operation of the spoilers.
Six spoilers are fitted to each wing and their functions are many and wonderous to behold. They operate in a multitude of combinations to achieve these functions which are as follows:-Speed Brakes (at any time in the flight), Roll control assistance (when flap is extended), Lift control (on approach), and automatic extension after landing. When spoiler extension is demanded the aircraft decides which ones will extend and which ones will not. To make these decisions it gathers information from a series of speed sensitive switches, flap position indicating switches, Throttle position switches, and "squat" switches on each of the three U/C. legs.
Four double-slotted Fowler flaps are fitted to the trailing edges of the wings and alternate between the spoilers, while there are seven slats, or leading edge flaps, fitted to each wing. The slats go out with the first extension of the flaps (3 degrees), and are responsible for the very marked difference in the stall, and approach, speeds when either flapped or clean.
Hydraulic Systems.
There are four hydraulic systems in the Tristar. They are completely independent of each other. Each has is own reservoir and pressure source, and a loss of fluid in one will not affect any other. Pressure is provided by E.D.P.'s, P.T.U.'s, A.T.M.'s , electrically powered pumps and a R.A.T.
"A" System is powered by an E.D.P. on No. 1 engine and has, as an alternate power source, a PTU from System "B".
"B" System is powered by an E.D.P. on No. 2 engine and, as alternate power source, has an A.T.M. and an electric pump,
"C" System is exactly similar to "B" System but in addition may be powere by the R.A.T.
"D" System is exactly similar to "A" System.
The RAT is extended automatically when needed, and can be manually extended on the ground. It is normally "pinned", for safety reasons, when the aircraft is on the ground.
The most important hydraulically operated services are the flight controls and each of them is supplied with a multitude of alternate pressure sources, either by extra jacks to the same control surface or to mated surfaces (ie spoilers). There are two independent sets of wheel brakes. U/C. can be free falled, and flaps can be done without .
Flight Director/Auto Pilot, Area Navigation, & Auto Land.
Equipment includes, two Auto Pilots. two Flight Directors. three computors, two Inertial Nav. Systems and two VORTAC's.
The information used by the autopilot is the same as used by the corresponding flight director. Only one autopilot may be operated at a time, except in "Autoland" mode, but the flight directors may be operated in conjunction or independently and either automatically or by manual input. The third nav. computor monitors the other two at all times and any one of the three that is "odd man out" is automatically discarded. VORTAC stations are automatically tuned as the a/c. moves along track. As an alternate to automatic navigation the autopilot in use may be manually controlled
Movement along track may be monitored on a C.R.T. type display, a complete sector flight plan may be fed into the computer, automatic interceptions of VOR radials and ILS's can be made, an auto throttle is fitted, and either height or speed may be maintained.
Auto landings are available wherever there is a suitable ILS. Interception of both the ILS and the G/S. are automatic. A "Go Around" facility is incorporated, it is armed when flap in excess of 33 degrees is selected and it is activated when a button is pressed.
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VR-HFX has covered the TriStar systems rather well...while there are very slight differences between models...all generally correct.
As to flight control redundancy...the TriStar has no equal in this regard, designed right in from the begining.
As an example, a TriStar was landed in the middle east with only one half of one hydraulic system quantity remaining..and done by a brand new First Officer, who had very good training.
The dual channel dual autopilots fitted provided superb automatic approach/langings. CAT IIIC capability built in, from the start...by the folks who migrated to Lockheed from the HS Trident team, so I was told. The only thing missing was Smiths stamped on the autopilot control panel.
The Lockheed TriStar was the cream d'la cream of early design wide-body aircraft, IMHO.
Just like the Lockheed 1649A was the epitomy of piston-engine airliner designs. Douglas made more...Boeing made a lot more, Lockheed provided the most technically advanced designs.
As to flight control redundancy...the TriStar has no equal in this regard, designed right in from the begining.
As an example, a TriStar was landed in the middle east with only one half of one hydraulic system quantity remaining..and done by a brand new First Officer, who had very good training.
The dual channel dual autopilots fitted provided superb automatic approach/langings. CAT IIIC capability built in, from the start...by the folks who migrated to Lockheed from the HS Trident team, so I was told. The only thing missing was Smiths stamped on the autopilot control panel.
The Lockheed TriStar was the cream d'la cream of early design wide-body aircraft, IMHO.
Just like the Lockheed 1649A was the epitomy of piston-engine airliner designs. Douglas made more...Boeing made a lot more, Lockheed provided the most technically advanced designs.
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Thanks a lot, gentlemen, for your descriptions!
I had already heard, in fact, that technologically the Tristar was better than the DC10.
For example on the DC10 you have to keep an eye on which tank the n°2 eng is feeding from, for a possible imbalance. Not so on the Tristar, where that is equally shared between tanks 2L and 2R by a flow equalizer.
It seems Direct Lift Control is unique in commercial airliners.
Did it require a different mental approach on maintaining the glide?
Did you like it?
ps: one silly question: I have seen various Tristar takeoffs: everytime it seemed to be underpowered (quite flat climb gradient, at least initially). Was that a false impression?
Again, thank you for your time!
LEM
I had already heard, in fact, that technologically the Tristar was better than the DC10.
For example on the DC10 you have to keep an eye on which tank the n°2 eng is feeding from, for a possible imbalance. Not so on the Tristar, where that is equally shared between tanks 2L and 2R by a flow equalizer.
It seems Direct Lift Control is unique in commercial airliners.
Did it require a different mental approach on maintaining the glide?
Did you like it?
ps: one silly question: I have seen various Tristar takeoffs: everytime it seemed to be underpowered (quite flat climb gradient, at least initially). Was that a false impression?
Again, thank you for your time!
LEM
I forgot to add...the nicest a/c I have ever flown...by far...and the list includes:
C-130, PC-3 B-707/747/777.The L-1011 was light years ahead of it's time and apart from being a bit under-powered at MTOW and short on range (cf: DC10-30) it was the best a/c per dollar that CX ever owned...a license to print money.
C-130, PC-3 B-707/747/777.The L-1011 was light years ahead of it's time and apart from being a bit under-powered at MTOW and short on range (cf: DC10-30) it was the best a/c per dollar that CX ever owned...a license to print money.
Last edited by VR-HFX; 18th Jun 2003 at 09:00.
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LEM,
Some of the early TriStar models powered by the RB.211-22B engine were a bit underpowered.
Later on, the RB.211-524B4 engine was fitted to the standard body aircraft, with excellent results...lots of power.
The last model produced, the -500 series had a slightly shorter fuselage, longer wing, and much more fuel...12 hours range. In addition, had active ailerons, for a smoother ride in turbulence, amoung other things. So far as I know, direct lift control is not used on any other civil aircraft type. Also used on the space shuttle, for pinpoint accurate landings.
Personally flew the Lockheed TriStar for over twenty years with four different carriers...and she never let me down.
Some of the early TriStar models powered by the RB.211-22B engine were a bit underpowered.
Later on, the RB.211-524B4 engine was fitted to the standard body aircraft, with excellent results...lots of power.
The last model produced, the -500 series had a slightly shorter fuselage, longer wing, and much more fuel...12 hours range. In addition, had active ailerons, for a smoother ride in turbulence, amoung other things. So far as I know, direct lift control is not used on any other civil aircraft type. Also used on the space shuttle, for pinpoint accurate landings.
Personally flew the Lockheed TriStar for over twenty years with four different carriers...and she never let me down.
Ah yes HD...the good ol'days..with PJ the Greek in white shoes at JJ's and a million other fun evenings...alas all gone now....except for the black coffee which is the only thing that is better than it used to be.
Keep well.
Keep well.
Last edited by VR-HFX; 18th Jun 2003 at 09:07.
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The -22 was rated at 42,000 Lbs thrust, and the latest -524B4 version was rated at 50,000 Lbs thrust. Big difference in power.
What killed the TriStar program was the failure of Lockheed to offer customers alternate engine manufacturers. It's what Douglas and Boeing had learned early on when building their 4 engined DC8s and 707s. Either was available with RR or P&W powerplants.
What killed the TriStar program was the failure of Lockheed to offer customers alternate engine manufacturers. It's what Douglas and Boeing had learned early on when building their 4 engined DC8s and 707s. Either was available with RR or P&W powerplants.
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Might have been a nice aeroplane to fly........but it was an absolute pile of C##P to work on !.........One of the best moments of my career was when my employers stopped flying the "Hangar Queens"
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Sad to hear that, cirrus01.
Oddly enough, UL had (at one time) the highest daily utilization of any TriStar operator...16.6 hours, as I recall.
All this, and maintaining out of an old blister hangar in CMB.
Well trained ground guys....who later migrated to GAMCO in AUH.
Oddly enough, UL had (at one time) the highest daily utilization of any TriStar operator...16.6 hours, as I recall.
All this, and maintaining out of an old blister hangar in CMB.
Well trained ground guys....who later migrated to GAMCO in AUH.
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Glue Ball,
the Tristar failure was entirely due to the RR collapse.
They tried desparately to use alternative engines but there were two major problems.
The only suitable engines at that time were the other 2 big fan engines.
The GE CF-6 and the PW JT9.
First problem was the fact that the RR was a 3 spool engine and the other two were 2 spool engines. different trust line, diamter and CofG, hence major re-design
Second problem was there were NO engines available.
If you remember there were pictures at the time of lines of B747 sitting in Seattle with concrete blocks in place of engines. This was because PW had their share of problems with ovalation ( Not ovulation
) so none of those available.
GE were flat out producing for DC10 ( and I suspect Douglas would have put their oar in at GE supplying for the opposition
)
So Lockheed, being the new boys on the block had to wait it out.
There was always promises that RR would be bailed out but it was too long in coming.
the Tristar failure was entirely due to the RR collapse.
They tried desparately to use alternative engines but there were two major problems.
The only suitable engines at that time were the other 2 big fan engines.
The GE CF-6 and the PW JT9.
First problem was the fact that the RR was a 3 spool engine and the other two were 2 spool engines. different trust line, diamter and CofG, hence major re-design
Second problem was there were NO engines available.
If you remember there were pictures at the time of lines of B747 sitting in Seattle with concrete blocks in place of engines. This was because PW had their share of problems with ovalation ( Not ovulation
) so none of those available.GE were flat out producing for DC10 ( and I suspect Douglas would have put their oar in at GE supplying for the opposition
)So Lockheed, being the new boys on the block had to wait it out.
There was always promises that RR would be bailed out but it was too long in coming.
LEM
Now that is a very good question.
I suspect it is what I used to do when Ms HFX was ovulating...run around an oval until I was too tired to do something that would take another million out of my bank account over the ensuing 20+ years.
In this context it is probably what P&W did when Lockheed expressed amorous intent.
But I could well be wrong.
Now that is a very good question.
I suspect it is what I used to do when Ms HFX was ovulating...run around an oval until I was too tired to do something that would take another million out of my bank account over the ensuing 20+ years.
In this context it is probably what P&W did when Lockheed expressed amorous intent.
But I could well be wrong.
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LEM,
These were the first of the "big" fan engines so bound to be a bit of a learning curve 
The engine started off round when cold but went oval during running with temperature increase. Not a good thing where rotating machinery is concerned
This problem did not occur with the concrete blocks in the place of engines
There were lots of pics of the Boeing Flight line at that time.
These were the first of the "big" fan engines so bound to be a bit of a learning curve
The engine started off round when cold but went oval during running with temperature increase. Not a good thing where rotating machinery is concerned
This problem did not occur with the concrete blocks in the place of engines
There were lots of pics of the Boeing Flight line at that time.
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The early RB.211's were certainly not without their problems as well.
Recall Eastern Air Lines had to do an 'engine run-up' before brakes release, and takeoff commenced.
Then, noticed three RB.211's on the ramp in San Juan (1974) with all the last stage turbine blades gone...gone as in melted away .
Must have been rather expensive.
Recall Eastern Air Lines had to do an 'engine run-up' before brakes release, and takeoff commenced.
Then, noticed three RB.211's on the ramp in San Juan (1974) with all the last stage turbine blades gone...gone as in melted away .
Must have been rather expensive.
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411,
Wasnt the reason that Esatern did that run up to make sure that all the MCD's had seals installed in them ?
Didnt all three engine keep running with no oil ??
Re the San Juan 1974 - yes there were a few pilots around that operated like that in thise days. I guess operating a those new fangled engines took a bit of getting used to
Wasnt the reason that Esatern did that run up to make sure that all the MCD's had seals installed in them ?
Didnt all three engine keep running with no oil ??
Re the San Juan 1974 - yes there were a few pilots around that operated like that in thise days. I guess operating a those new fangled engines took a bit of getting used to
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DLC in go around
You omitted the best thing about DLC.
If on approach with DLC and you need to initiate a Go Around, by advancing the throttles, the spoilers are sent back to zero from the 7 degree DLC nul position and you have an instant 1000 feet per minute rate of climb.
So while the engines are still winding up you are now over flying the runway obstruction in a calm cool collected manner, and not praying that the donks will wind up in time as on todays modern Busses and Boeings.
Clever chaps the guys at NASA-Ames who came up with the idea that Lockheed adopted so very well.
Could be done easily with the flying software of todays aircraft. Maybe on the B787????
If on approach with DLC and you need to initiate a Go Around, by advancing the throttles, the spoilers are sent back to zero from the 7 degree DLC nul position and you have an instant 1000 feet per minute rate of climb.
So while the engines are still winding up you are now over flying the runway obstruction in a calm cool collected manner, and not praying that the donks will wind up in time as on todays modern Busses and Boeings.
Clever chaps the guys at NASA-Ames who came up with the idea that Lockheed adopted so very well.
Could be done easily with the flying software of todays aircraft. Maybe on the B787????