More tech questions !!
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More tech questions !!
Need some help with these guys!
Q1. What is direct lift control ?
Q2. What are active controls ?
Q3. What are the 6 functions of Spoilers ?
Q4. What is "Q feel" ?
Q5. What causes the secondary yaw in Dutch Roll ?
Q6. What is a deep or super stall ?
Q7. Can you explain assymetric blade effect?
Any assistance is appreciated. Thanks
Q1. What is direct lift control ?
Q2. What are active controls ?
Q3. What are the 6 functions of Spoilers ?
Q4. What is "Q feel" ?
Q5. What causes the secondary yaw in Dutch Roll ?
Q6. What is a deep or super stall ?
Q7. Can you explain assymetric blade effect?
Any assistance is appreciated. Thanks
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These are of the top of my head as a starter for ten.
1. Direct lift control is the use of jet air across the top surface of the wing to augment lift. Used on some Russian aircraft
2. Not sure on this one as it a little vague. I think it means a set of flight controls that augment the stability of an aircraft. They continually move to keep the aircraft stable and thats before the pilot supplies an input
3. Lift dump on landing, airbrake, augment roll control....erm....can't think of any more.
4. Q is an aerodynamic term for 1/2 rho 'v' squared, the increase in forces with air density and speed. Q feel is added to hydraulic controls to give the pilot a feeling like that of a normal 'cable driven' system. i.e. Controls feel sluggish at low speed and firm at high speed.
5. Got me there
6. Deep stall usually exists of low wing, high tail aicraft. It is a stable stall, usually unrecoverable, where the distured air flow off the stalled wing blankets the high tail and prevents recovery or at least severely effects pitch control. It was researched on the trident and they lost an aircraft at Salisbury Plain on 22 Oct 1963 researching it!!
7. Try explaining this one without a pencil. Picture and aicraft at an angle of attack of about 10 degrees. The down going blade with have a bigger bite (AoA) in the air than the up going one. More force produced on one side of the propellor disc and can produce yaw I think. (I don't think it is precessed round 90 degrees like a helicopter)
1. Direct lift control is the use of jet air across the top surface of the wing to augment lift. Used on some Russian aircraft
2. Not sure on this one as it a little vague. I think it means a set of flight controls that augment the stability of an aircraft. They continually move to keep the aircraft stable and thats before the pilot supplies an input
3. Lift dump on landing, airbrake, augment roll control....erm....can't think of any more.
4. Q is an aerodynamic term for 1/2 rho 'v' squared, the increase in forces with air density and speed. Q feel is added to hydraulic controls to give the pilot a feeling like that of a normal 'cable driven' system. i.e. Controls feel sluggish at low speed and firm at high speed.
5. Got me there
6. Deep stall usually exists of low wing, high tail aicraft. It is a stable stall, usually unrecoverable, where the distured air flow off the stalled wing blankets the high tail and prevents recovery or at least severely effects pitch control. It was researched on the trident and they lost an aircraft at Salisbury Plain on 22 Oct 1963 researching it!!
7. Try explaining this one without a pencil. Picture and aicraft at an angle of attack of about 10 degrees. The down going blade with have a bigger bite (AoA) in the air than the up going one. More force produced on one side of the propellor disc and can produce yaw I think. (I don't think it is precessed round 90 degrees like a helicopter)
After the a/c rolls it starts to sideslip, causing the resultant airflow to be slightly offset from the fuselage centreline (the longitudinal axis). The fin causes the a/c to yaw into the now offset airstream.
Meanwhile the lower wing, being swept, experiences a significant increase in its lift producing ability compared to the other wing. This causes the a/c to roll back upright. Inertia causes the a/c to continue rolling so now the effect is repeated on the other side.
End result is a series of roll - yaw - roll upright - continue to roll - yaw the other way - roll back upright - continue to roll etc etc. although it can be a very slow cycle.
The nose of the a/c will seem to trace a horizontal figure '8'.
I think it's caused when an a/c has greater stability in roll compared to yaw. The reverse would cause 'snaking'.
Meanwhile the lower wing, being swept, experiences a significant increase in its lift producing ability compared to the other wing. This causes the a/c to roll back upright. Inertia causes the a/c to continue rolling so now the effect is repeated on the other side.
End result is a series of roll - yaw - roll upright - continue to roll - yaw the other way - roll back upright - continue to roll etc etc. although it can be a very slow cycle.
The nose of the a/c will seem to trace a horizontal figure '8'.
I think it's caused when an a/c has greater stability in roll compared to yaw. The reverse would cause 'snaking'.
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Direct Lift Control is a TriStar device used to keep the aircraft attitude constant on an auto ILS. Other aircraft may also use it.
Normally, if you want to increase your rate of descent, you push the stick forward, the elevators go down and the aircraft pitches down. With DLC small stick movements on the approach lead to the spoilers moving in or out to decrease or increase rate of descent keeping the attitude constant. Large stick movements change the attitude as well.
Normally, if you want to increase your rate of descent, you push the stick forward, the elevators go down and the aircraft pitches down. With DLC small stick movements on the approach lead to the spoilers moving in or out to decrease or increase rate of descent keeping the attitude constant. Large stick movements change the attitude as well.
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Tinstaafl---
Seems correct to me. Boeing increased the height of the tail on later models of the 707 to help with this problem. Also, a series yaw damper was fitted, better still.
DLC on the TriStar has worked well for many years with few failures and aided in certification for CAT III. Interesting to note that some pilots prefer to switch off DLC so they can land the aircraft like a Boeing. Watched one Captain do this on an FAA check ride, only to be failed. The inspector mentioned that aircraft systems should be switched off only in the event of malfunction, and according to check list procedures.
He was quite right IMHO.
[ 12 July 2001: Message edited by: 411A ]
Seems correct to me. Boeing increased the height of the tail on later models of the 707 to help with this problem. Also, a series yaw damper was fitted, better still.
DLC on the TriStar has worked well for many years with few failures and aided in certification for CAT III. Interesting to note that some pilots prefer to switch off DLC so they can land the aircraft like a Boeing. Watched one Captain do this on an FAA check ride, only to be failed. The inspector mentioned that aircraft systems should be switched off only in the event of malfunction, and according to check list procedures.
He was quite right IMHO.
[ 12 July 2001: Message edited by: 411A ]
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Hello Down Three Greens
Regarding your answer to question number six, I’m not quite sure whether you meant it was a Trident that crashed on 22 October 1963, or whether you just meant an aircraft was lost!
The aircraft that crashed during test flying on 22 October 1963, near Chicklade, Wiltshire, was in fact a BAC 1-11 (another "T" tail design), and tragically a further BAC 1-11 was also lost during test flying on 20 August 1964.
The Trident which crashed during test flying, and to which I believe you may have been referring, was a Trident 1, G-ARPY, which deep stalled and was lost on 03 June 1966, near Norwich, Norfolk.
Regarding your answer to question number six, I’m not quite sure whether you meant it was a Trident that crashed on 22 October 1963, or whether you just meant an aircraft was lost!
The aircraft that crashed during test flying on 22 October 1963, near Chicklade, Wiltshire, was in fact a BAC 1-11 (another "T" tail design), and tragically a further BAC 1-11 was also lost during test flying on 20 August 1964.
The Trident which crashed during test flying, and to which I believe you may have been referring, was a Trident 1, G-ARPY, which deep stalled and was lost on 03 June 1966, near Norwich, Norfolk.
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Tinstaafl---
The only Boeing aircraft that I have flown is the 707 (except for a very brief period in a B-377).
In the 707, just before touchdown, the column can be moved forward gently resulting in a very smooth landing, if done properly (Boeing push).
This works best with the long-body aircraft (-300 series). Have seen this done with a 727 as well.
In the Lockheed TriStar, the Boeing push is not possible because, if the column is moved forward, the spoilers come up from their 7 degree null position. If this is done at about 10 feet, the resulting thud will shake your back teeth loose.
With the DLC switched off however, the spoilers are retracted (except for roll assist) and the Boeing push is possible.
The TriStar can be rolled on very smoothly nearly every time, once you get the hang of it.
And, the best part is, it ain't a Boeing.
I have spent 20 years in this fine machine, it is an absolute delight to fly.
The only Boeing aircraft that I have flown is the 707 (except for a very brief period in a B-377).
In the 707, just before touchdown, the column can be moved forward gently resulting in a very smooth landing, if done properly (Boeing push).
This works best with the long-body aircraft (-300 series). Have seen this done with a 727 as well.
In the Lockheed TriStar, the Boeing push is not possible because, if the column is moved forward, the spoilers come up from their 7 degree null position. If this is done at about 10 feet, the resulting thud will shake your back teeth loose.
With the DLC switched off however, the spoilers are retracted (except for roll assist) and the Boeing push is possible.
The TriStar can be rolled on very smoothly nearly every time, once you get the hang of it.
And, the best part is, it ain't a Boeing.
I have spent 20 years in this fine machine, it is an absolute delight to fly.
Q5 Dutch Roll.
Lateral stability = Roll due to sideslip
Directional stability = Yaw due to sideslip.
As an aircraft rolls or yaws sideslip is inevitable, part of the control mechanism. The sideslip, however causes, has an impact on both axes.
So, DR is an oscillation in both yaw and roll, driven by sideslip. If it is perceived as "snaking" (the nose weaving from side to side) then it is mostly in yaw, and thus directional stability is greater than lateral stability and if it's a problem, the solution is probably a yaw damper.
If DR is seen as wing-rocking, then it is mostly in yaw, and thus lateral stability is greater than directional stability and the fix is a roll damper.
More normally lat-dir is fairly well balanced and DR is seen as a figure of 8 along the nose, or oval at the wingtip (or when test flying, the chinagraph cross you put on the side window). The ratio of height:width of the oval seen out the side is approximately the ratio of lateral to directional stability.
G
[ 13 July 2001: Message edited by: Genghis the Engineer ]
Lateral stability = Roll due to sideslip
Directional stability = Yaw due to sideslip.
As an aircraft rolls or yaws sideslip is inevitable, part of the control mechanism. The sideslip, however causes, has an impact on both axes.
So, DR is an oscillation in both yaw and roll, driven by sideslip. If it is perceived as "snaking" (the nose weaving from side to side) then it is mostly in yaw, and thus directional stability is greater than lateral stability and if it's a problem, the solution is probably a yaw damper.
If DR is seen as wing-rocking, then it is mostly in yaw, and thus lateral stability is greater than directional stability and the fix is a roll damper.
More normally lat-dir is fairly well balanced and DR is seen as a figure of 8 along the nose, or oval at the wingtip (or when test flying, the chinagraph cross you put on the side window). The ratio of height:width of the oval seen out the side is approximately the ratio of lateral to directional stability.
G
[ 13 July 2001: Message edited by: Genghis the Engineer ]
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Ah, caught me. Told you most of it was from memory. Thanks for putting the facts straight. Twas in fact a 1-11. Just finished reading Brian Trubshaw's Autobiography 'Test Pilot' Thanks Tinstaafl 
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1. Tristar. On selecting land flap(switch is on the lever not the flap so you may not actualy have it.) The inboard 4 spoiler panels move out to a 9degree null position. From there they respond to pitch inputs along with the stab(all flying tailplain)to increase or decrease the rate of descent without changing the pitch attitude. Developed to reduce "longitudinal scatter" ie. make the aircraft touchdown at the same place on the runway.
2 Tristar-500. The outbard ailerons have 3 active modes to reduce wing bending fatigue.
a. High Lift mode. With flap selected both outboard ailerons move to a 6 degree up position thus offloading the outboard section of the wing.
b. Elastic mode suppression. G meters in the wing tips and body compare singnals and cause each aileron seperately to move in oposition to the bending force thus smoothing out individual wing flexing.
c. Donīt remember the name. Similar to b but both ailerons work in unison thus smoothing wing root flexing and giving a smoother ride in turb.
The whole lot was developed because the 500 has extensions to the wing tips to reduce induced drag.
3. Reduce lift, Increase drag(air), Increase drag(ground), roll assist, DLC, pass
4. 1/2rho vsq uses a Q pot(chamber) to measure air density and cause artificial force(friction) in flying controls.
5 wing sweep.
6 A stall condition that due to aircraft design causes the elevator to fly in disturbed air thus rendering it less or in-efective.
7no.
FE Hoppy available for work NOW!!!
2 Tristar-500. The outbard ailerons have 3 active modes to reduce wing bending fatigue.
a. High Lift mode. With flap selected both outboard ailerons move to a 6 degree up position thus offloading the outboard section of the wing.
b. Elastic mode suppression. G meters in the wing tips and body compare singnals and cause each aileron seperately to move in oposition to the bending force thus smoothing out individual wing flexing.
c. Donīt remember the name. Similar to b but both ailerons work in unison thus smoothing wing root flexing and giving a smoother ride in turb.
The whole lot was developed because the 500 has extensions to the wing tips to reduce induced drag.
3. Reduce lift, Increase drag(air), Increase drag(ground), roll assist, DLC, pass
4. 1/2rho vsq uses a Q pot(chamber) to measure air density and cause artificial force(friction) in flying controls.
5 wing sweep.
6 A stall condition that due to aircraft design causes the elevator to fly in disturbed air thus rendering it less or in-efective.
7no.
FE Hoppy available for work NOW!!!
Ta, 411A.
The rollover landing I've heard about. Never thought how it would get screwed up by DLC.
I see what you mean. The DLC would interpret the slight pitch input to be commanding a lift reduction, not the desired slow rate pitch ND.
[ 13 July 2001: Message edited by: Tinstaafl ]
The rollover landing I've heard about. Never thought how it would get screwed up by DLC.
I see what you mean. The DLC would interpret the slight pitch input to be commanding a lift reduction, not the desired slow rate pitch ND.
[ 13 July 2001: Message edited by: Tinstaafl ]
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FE Hoppy--
The -500 series TriStar uses 9 degree null position for the spoilers, when landing flap selected. The stardard body aircraft uses 7 degrees.
Contrary to some folks thinking, it works really well. Suspect those that throw darts at the TriStar have never flown it.
Have to say though, it does require care and attention from the maintenance department, unfortunately some operators now ignore this very basic requirement.
The -500 series TriStar uses 9 degree null position for the spoilers, when landing flap selected. The stardard body aircraft uses 7 degrees.
Contrary to some folks thinking, it works really well. Suspect those that throw darts at the TriStar have never flown it.
Have to say though, it does require care and attention from the maintenance department, unfortunately some operators now ignore this very basic requirement.
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411A, reference the "Boeing Push" (or "Boeing Bunt" as I first heard it referred to many years ago in CX) I can categorically state that there is one longbody Boeing on which it does not work...
About 4 years ago, Larnaca, B777, muggins here flares about 10 feet too high, and thus performs company-prohibited low-fly-by manouever at about 5 feet radio. Not got the World's longest piece of tarmac to do this with in front of me.
"No problem, " thinks I, "I'll just bunt it, that always works."
No it doesn't. On the 777 it merely flattens the attitude at which your low pass is being flown. Low fly-by now is taking place at a crowd-pleasing 3 feet!
For the record we touched down through sheer luck a millisecond before I hit TOGA, and completed the (er, rather deep!) landing with plenty of margin. Lesson learned.
And then... on the bus, what were the comments from the back? "Who did that landing? It was so good, so smooth!" Sometimes it is best to keep'em in ignorance of the reality, no?
Ģ6
[ 14 July 2001: Message edited by: Sick Squid ]
About 4 years ago, Larnaca, B777, muggins here flares about 10 feet too high, and thus performs company-prohibited low-fly-by manouever at about 5 feet radio. Not got the World's longest piece of tarmac to do this with in front of me.
"No problem, " thinks I, "I'll just bunt it, that always works."
No it doesn't. On the 777 it merely flattens the attitude at which your low pass is being flown. Low fly-by now is taking place at a crowd-pleasing 3 feet!
For the record we touched down through sheer luck a millisecond before I hit TOGA, and completed the (er, rather deep!) landing with plenty of margin. Lesson learned.
And then... on the bus, what were the comments from the back? "Who did that landing? It was so good, so smooth!" Sometimes it is best to keep'em in ignorance of the reality, no?
Ģ6
[ 14 July 2001: Message edited by: Sick Squid ]
I larfed, and I larfed, and I larfed! 
At the next PPRuNe bash, is it OK for me to say "G'day muggins, good to see you again.", instead of the more usual 'Wanna' beer?'
At the next PPRuNe bash, is it OK for me to say "G'day muggins, good to see you again.", instead of the more usual 'Wanna' beer?'
