Boeing 727 Question
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Jane Doh: the 727 wasn't poor in terms of directional stability - just that the latreral stability was very strong. (courtesy, probably, of the amount of wing sweep).
The longer -200 had effectively more rudder 'volume', as the extra fuselage length behind the CG provides additional moment arm for the fin. Surmising (never flown the machine), but this is probably the reason for the 747SP's additional fin/rudder area - the aircarft is shorter, so has less moment arm, though the same wing/engine (basically).
The longer -200 had effectively more rudder 'volume', as the extra fuselage length behind the CG provides additional moment arm for the fin. Surmising (never flown the machine), but this is probably the reason for the 747SP's additional fin/rudder area - the aircarft is shorter, so has less moment arm, though the same wing/engine (basically).
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Is it possible to have an adverse yaw induced a dutch roll during the approach
phase with 30 to 40 flap degree?. [PS. YD off]
Since, I used to fly Flight simulator [I know it isn't real, but it helps me to learn]
on B727 by hand on final. I believe I have a strong adverse yaw during making the alignment to the runway by hand [I turned YD off to see the airplane handling quality] and hence dutch roll which add a difficulty during landing.
What about the real aircraft? Does any one have any experience or idea about
dutch roll during the approach or landing phase?
Best Regards
phase with 30 to 40 flap degree?. [PS. YD off]
Since, I used to fly Flight simulator [I know it isn't real, but it helps me to learn]
on B727 by hand on final. I believe I have a strong adverse yaw during making the alignment to the runway by hand [I turned YD off to see the airplane handling quality] and hence dutch roll which add a difficulty during landing.
What about the real aircraft? Does any one have any experience or idea about
dutch roll during the approach or landing phase?
Best Regards
Last edited by Mr.Vortex; 31st Dec 2010 at 05:06. Reason: add some note
The 727 on approach was conventional in all respects. I see Mr 'Vortex' you are only 17, there is nothing wrong with that and it's good to see young people interested. In a modern jet, rudder is used only for x-wind landings, either to kick it straight during the flare or use cross-control wing down whatever your preference during the approach.
Before I get shot down, rudder is obsviously used for take-off, directional control and x-winds etc. you should never see 'Dutch-Roll' characteristics in normal flight. For what it's worth the 727 is the nicest handling of all the Boeings I have flown.
At first I was going to say if you're not doing .83 in the pattern it shouldn't be a problem. However, thinking about it, you've got a lot more lift and drag with flaps 30 (you're not going to see flaps 40 due to noise restrictions.) Plus you lose some yaw damping due to the nose being pitched up and blanking part of the vertical fin. So I don't know.
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I took my type rating check ride in the aircraft, a -100. One of the tests was to recover from an induced Dutch roll. This was a long time ago so I cannot remember the airspeed and altitude where this section of the check ride took place. I think we were at FL 240 and at 300 Kts IAS, I think.
The FAA check airman was in the jump seat behind me and another FAA pilot was in the right seat. The pilot in the right seat turned off both yaw dampers and then induced the Dutch Roll, then just before he gave me control of the aircraft the check airman instructed me not to use the spoilers, but to use the flight controls.
Using the full aileron into the roll stopped the Dutch Roll, the yaw dampers were turned back on and the check ride continued.
I was more nervous about the full dirty stall than the Dutch Roll bit.
As some have said earlier, the 727 was a very nice flying aircraft and when light we used some really short runways, shortest I personally flew into and out of was 4,800 feet. Passenger load was only 15 people and we two hours of fuel on board on takeoff. I was actually more worried about sinking into the ramp/taxiway/runway. Oh, we could use flaps 40, which I did on that runway.
So, also as some one else already posted, to let a Dutch Roll develop into a serious condition, you'd have to be dead already.
And yes, if one or both yaw dampers were out, there were some very restrictive conditions one had to abide by. If I remember correctly, if you lost both in flight, the magic numbers were below FL 240 and 250 Kts IAS. But it has been a while since I flew the 72.
The FAA check airman was in the jump seat behind me and another FAA pilot was in the right seat. The pilot in the right seat turned off both yaw dampers and then induced the Dutch Roll, then just before he gave me control of the aircraft the check airman instructed me not to use the spoilers, but to use the flight controls.
Using the full aileron into the roll stopped the Dutch Roll, the yaw dampers were turned back on and the check ride continued.
I was more nervous about the full dirty stall than the Dutch Roll bit.
As some have said earlier, the 727 was a very nice flying aircraft and when light we used some really short runways, shortest I personally flew into and out of was 4,800 feet. Passenger load was only 15 people and we two hours of fuel on board on takeoff. I was actually more worried about sinking into the ramp/taxiway/runway. Oh, we could use flaps 40, which I did on that runway.
So, also as some one else already posted, to let a Dutch Roll develop into a serious condition, you'd have to be dead already.
And yes, if one or both yaw dampers were out, there were some very restrictive conditions one had to abide by. If I remember correctly, if you lost both in flight, the magic numbers were below FL 240 and 250 Kts IAS. But it has been a while since I flew the 72.
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Old Fella,
If I recall, the 707's 35-degree sweep-angle figure was based at the 1/4-chord mark (I think it was around 37.5 at the leading-edge); the 727's 31.5 degree sweep-angle was based at the leading-edge as far as I know, with the sweep at the quarter-chord being 28.5.
trimotor,
Okay, I understand
If I recall, the 707's 35-degree sweep-angle figure was based at the 1/4-chord mark (I think it was around 37.5 at the leading-edge); the 727's 31.5 degree sweep-angle was based at the leading-edge as far as I know, with the sweep at the quarter-chord being 28.5.
trimotor,
Jane Doh: the 727 wasn't poor in terms of directional stability - just that the latreral stability was very strong. (courtesy, probably, of the amount of wing sweep).
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Dutch roll inducement and Mach Tuck
Does the 727 wing dihedral additional to sweep have a combinatorial causal effect? Reduced aerodynamic damping at high altitude might also be influential I reckon.
What could cause a Dutch Roll apart from YD failure..Turbulence?
"Handling the Big Jets, D.P.Davis" has an exhaustive and best technical explaination of how to deal with Dutch Roll.It also explains series dampers and Roll dampers.
Does 727 suffer from significant Mach Tuck.Is there a Mach Trim indicator on the 727?
What could cause a Dutch Roll apart from YD failure..Turbulence?
"Handling the Big Jets, D.P.Davis" has an exhaustive and best technical explaination of how to deal with Dutch Roll.It also explains series dampers and Roll dampers.
Does 727 suffer from significant Mach Tuck.Is there a Mach Trim indicator on the 727?
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It's been a long time but as I recall the roll rate on the 727 almost doubled with spoilers deployed and one-half deployment was where it was most noticeable. Not sure why deploying the spoilers would be the appropriate recovery maneuver?
The Drill
Every training session on the 707 and the 727 had a dutch toll drill somewhere along the line.
The trick was to aggressively move the control wheel to the stops towards the wing that was coming up, then back to neutral (level) position.
As soon as the other wing started up, you did the same thing. It usually took 2 or 3 "slaps" as we called them to get the dutch roll stopped.
As I recall, they were called "slaps" because when you moved the control wheel hard one way or the other, it caused one of the spoilers on that side to "slap" up to assist the aileron"
Did many of them this way, and it worked.
The trick was to aggressively move the control wheel to the stops towards the wing that was coming up, then back to neutral (level) position.
As soon as the other wing started up, you did the same thing. It usually took 2 or 3 "slaps" as we called them to get the dutch roll stopped.
As I recall, they were called "slaps" because when you moved the control wheel hard one way or the other, it caused one of the spoilers on that side to "slap" up to assist the aileron"
Did many of them this way, and it worked.
The yaw damper is installed to prevent Dutch roll. So even in turbulence there should be no Dutch roll. There is no Mach trim in the 727. With a Mach limit of .90 I don't know what the critical Mach number is. And Mach tuck isn't much of a problem until you get close to critical Mach.
Been through many of the drills OBD mentions. I've seen them get out of hand if the pilot got out of sync with the ailerons. Like the old method of stall recovery (not losing altitude) it shows you can fly the plane. In the real world if you have a yaw damper failure you are going to have to slow down and go down so close the thrust levers, pull the boards and request a descent.
Been through many of the drills OBD mentions. I've seen them get out of hand if the pilot got out of sync with the ailerons. Like the old method of stall recovery (not losing altitude) it shows you can fly the plane. In the real world if you have a yaw damper failure you are going to have to slow down and go down so close the thrust levers, pull the boards and request a descent.
As someone typed in the 707, 727, 747, and 75/767. I just have a couple of comments. I only ever did Dutch roll in the sim in the 727 and found it a difficult recovery. The 707s I flew had yaw dampers, but in the sim recovery seemed much easier. I also flew the KC135 for many years. It didn't have a yaw damper, but did have a rudder axis for the autopilot. Take offs and landings were of course autopilot off and it was always funny to watch new guys Dutch roll their way down final. We also had to be able to air refuel autopilot off.
As far as longer or shorter planes being more stable I vote for longer. The 747-100/200s that I flew were very stable. The SP was very much less so.
My favorite narrow body plane is the 757. Going out of Denver on a hot day in a fully loaded 727 was a little much for my old heart. No problem in a 757 though. Also never had to go full power in the flare to avoid planting it.
As far as longer or shorter planes being more stable I vote for longer. The 747-100/200s that I flew were very stable. The SP was very much less so.
My favorite narrow body plane is the 757. Going out of Denver on a hot day in a fully loaded 727 was a little much for my old heart. No problem in a 757 though. Also never had to go full power in the flare to avoid planting it.
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727 roll rates with spoilers
Was the 727 roll rate assisted by spoiler's as high as the 747? Any idea of magnitude? 10 degrees per sec? Was there a restriction to this maneuvre or could be applied at will? No slats or flaps I suppose!
Must have been a handy maneuver for traffic avoidance or Intial turn off the airways on emergency descent.I wonder what kind of g loading you impose during the high roll rate and if you encroach the load limits? Was it a recommended Boeing maneuver at all or more of test pilot and wanna be test jockeys?
Must have been a handy maneuver for traffic avoidance or Intial turn off the airways on emergency descent.I wonder what kind of g loading you impose during the high roll rate and if you encroach the load limits? Was it a recommended Boeing maneuver at all or more of test pilot and wanna be test jockeys?
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On a turbulent approach in the 727, it was more like quick jabs of aileron to level the wings as all four ailerons and spoiler were operating. Perhaps the same was true of the 747 in terms of which controls were being operated with aileron input but I found it noticeably less roll responsive. There were several aircraft in between though so it is all based on memory.
Personally, I found that the 727 with flaps extended had a much greater roll response rate on final compared to the 747.
Must have been a handy maneuver for traffic avoidance or Intial turn off the airways on emergency descent. I wonder what kind of g loading you impose during the high roll rate and if you encroach the load limits? Was it a recommended Boeing maneuver at all or more of test pilot and wanna be test jockeys?
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Am not sure if there is or isnt a relationship between roll rate and g loading that's why am asking.I imagined higher roll rates impose more loads than low roll rates..better I review "Handling the Big Jets" again am sure I will get a precise Test Pilot answer.
As mentioned earlier other than spoileron "slaps" to bite off the otherwise divergent Dutch roll application of speed brakes was at how many units up?
As mentioned earlier other than spoileron "slaps" to bite off the otherwise divergent Dutch roll application of speed brakes was at how many units up?
Went straight from the 727 to 744. I think it's mainly the difference in size and mass.
Can't use speed brakes with flaps extended on a 727. It's not really a handy maneuver at all. You think you have to turn. Then you realize you want to turn faster than normal. So you pull the boards. Now you're slowing down so you have to add thrust and pull the nose up if you're hand flying. Ok, now you can start turning. Versus just turning the plane. Why would there be any G load issues during a roll? The G load is a function of bank angle if you're holding a constant altitude and not roll rate.
How does this bird behave on a x-wind final approach with both YDs off/unserviceable?
What the lowest hright Boeing limits the use of speed brakes if arriving hot on speed?
Can't use speed brakes with flaps extended on a 727. It's not really a handy maneuver at all. You think you have to turn. Then you realize you want to turn faster than normal. So you pull the boards. Now you're slowing down so you have to add thrust and pull the nose up if you're hand flying. Ok, now you can start turning. Versus just turning the plane. Why would there be any G load issues during a roll? The G load is a function of bank angle if you're holding a constant altitude and not roll rate.
How does this bird behave on a x-wind final approach with both YDs off/unserviceable?
What the lowest hright Boeing limits the use of speed brakes if arriving hot on speed?
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Static and Dynamic lateral Stability,Control and Maneuverability-Turning Performance
Part 1: Static Lateral Stability
The lateral motions in an aeroplane are of two types,assuming that the aeroplane posseses 'static stability' about the directional, or yaw axis ans has roll or 'dihedral stability'. Directional Stability addresses the tendency of the aeroplane to point into the oncoming airstream and is provided by the vertical fin.It is often referred to as "Dihedral Stability", since a wing dihedral angle provides the necessary restoring rolling moment.Dihedral (when wing tips higher than wing root..opposite to anhedral) effects on the rolling moment of a yawed wing.
Part 2 : Dynamic Lateral Stability (To be continued...)
The lateral motions in an aeroplane are of two types,assuming that the aeroplane posseses 'static stability' about the directional, or yaw axis ans has roll or 'dihedral stability'. Directional Stability addresses the tendency of the aeroplane to point into the oncoming airstream and is provided by the vertical fin.It is often referred to as "Dihedral Stability", since a wing dihedral angle provides the necessary restoring rolling moment.Dihedral (when wing tips higher than wing root..opposite to anhedral) effects on the rolling moment of a yawed wing.
Part 2 : Dynamic Lateral Stability (To be continued...)
Am not sure if there is or isnt a relationship between roll rate and g loading that's why am asking.I imagined higher roll rates impose more loads than low roll rates..better I review "Handling the Big Jets" again am sure I will get a precise Test Pilot answer.
As mentioned earlier other than spoileron "slaps" to bite off the otherwise divergent Dutch roll application of speed brakes was at how many units up?
As mentioned earlier other than spoileron "slaps" to bite off the otherwise divergent Dutch roll application of speed brakes was at how many units up?
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part 2: Dynamic Lateral Stability
(Continued...)
There are two types of possible lateral dynamic motion.The first is called the "Spiral Mode". If a spirally unstable airplane,through the action of a gust or othe disturbance,gets a small initial roll angle, a gentle side slip in the same direction of roll is produced if rolled tp the right...slideslip to the right hand side. If the dihedal stability is low,the directional stability keeps turning the airplane qhile the continuing bank angle maintains the side slip and yaw angle.As this process develops,the spiral gets tighter and steeper until finallt, if motion is unchecked, a steep, high-speed, spiral dive results! The motion develops so gradually,however, that it us usually corrected unconsciously by the handling pilot,who may not be aware that the spiral instability exists.A combination of high directional stability and low dihedral,or roll stability leads ti a spirally unstable aeroplane.
The second lateral motion is an oscillatory combined roll and yaw motion rederred to as the "Dutch Roll" ( coined to mimick drunken Dutch sailors landing on their next port of call afyer a long spell on rough seas I suspect). The Dutch Roll may be described as a yaw and roll to the right, followed by a recovery toward the equilibrium condition, then an overshootibg of this condition and a taw and roll to the left, thenafter back past the equilibrium attitude, and so on. The oscillatory period is usyally of the order of 3 to 5 seconds.Damping is increases by large directional stability and small dihedral and decreased by small dirwctional stability and large dihedral. Although usually stable in a normal airplane,the motion may be so slightly damped that the effect is very unpleasant and undesirable!
Swept wing aircraft have large digedral stability even when they have no dihedral angle.This is because, the effect if an angle of yaw is to increase the swewp back angle of onw wing panel and decrease it for the other side of the aeroplane. The change in sweep alters the effective dynamic pressure normal to the quarter-chord line of the wing panel, increasing the lift on one side of the wing,lowering it on the opposite side, and producing a restoring rolling moment. Nevertheless, many swept wing aeroplanes have a considerable dihedral angle, not for aerodynamic reasons bit to give adequate ground clearance for the wing tips and especially wing -mounted engine nacelles during take off and landing.These aircraft may then have too much dihedral effect for satisfactory Dutch Roll damping.The technical name for Dutch Roll is Oscilatory lateral stability. The problem is solved by installing a yaw damper YD.The Yaw Damper is in effect a special purpose autopilot that damps out any yawing oscillation by apying rudder corrections instantaneosly.Some swept wing aircraft demonstrate an unstable Dutch Roll mode.If the Dutch Roll is very lightly damped or unstable,the YD becomes a safety requirement rather than a pilot and passenger design convenience.Dual YDs are required and a failed YD is cause for limiting flight to lower altitude and lower Mach numbers.At high sltitude there is reduced aerodynamic damping due to high altitude low air density.At the lower altitudes Dutch Roll stability is improved.
Part 3 ...to be continued. "Turning performance".
There are two types of possible lateral dynamic motion.The first is called the "Spiral Mode". If a spirally unstable airplane,through the action of a gust or othe disturbance,gets a small initial roll angle, a gentle side slip in the same direction of roll is produced if rolled tp the right...slideslip to the right hand side. If the dihedal stability is low,the directional stability keeps turning the airplane qhile the continuing bank angle maintains the side slip and yaw angle.As this process develops,the spiral gets tighter and steeper until finallt, if motion is unchecked, a steep, high-speed, spiral dive results! The motion develops so gradually,however, that it us usually corrected unconsciously by the handling pilot,who may not be aware that the spiral instability exists.A combination of high directional stability and low dihedral,or roll stability leads ti a spirally unstable aeroplane.
The second lateral motion is an oscillatory combined roll and yaw motion rederred to as the "Dutch Roll" ( coined to mimick drunken Dutch sailors landing on their next port of call afyer a long spell on rough seas I suspect). The Dutch Roll may be described as a yaw and roll to the right, followed by a recovery toward the equilibrium condition, then an overshootibg of this condition and a taw and roll to the left, thenafter back past the equilibrium attitude, and so on. The oscillatory period is usyally of the order of 3 to 5 seconds.Damping is increases by large directional stability and small dihedral and decreased by small dirwctional stability and large dihedral. Although usually stable in a normal airplane,the motion may be so slightly damped that the effect is very unpleasant and undesirable!
Swept wing aircraft have large digedral stability even when they have no dihedral angle.This is because, the effect if an angle of yaw is to increase the swewp back angle of onw wing panel and decrease it for the other side of the aeroplane. The change in sweep alters the effective dynamic pressure normal to the quarter-chord line of the wing panel, increasing the lift on one side of the wing,lowering it on the opposite side, and producing a restoring rolling moment. Nevertheless, many swept wing aeroplanes have a considerable dihedral angle, not for aerodynamic reasons bit to give adequate ground clearance for the wing tips and especially wing -mounted engine nacelles during take off and landing.These aircraft may then have too much dihedral effect for satisfactory Dutch Roll damping.The technical name for Dutch Roll is Oscilatory lateral stability. The problem is solved by installing a yaw damper YD.The Yaw Damper is in effect a special purpose autopilot that damps out any yawing oscillation by apying rudder corrections instantaneosly.Some swept wing aircraft demonstrate an unstable Dutch Roll mode.If the Dutch Roll is very lightly damped or unstable,the YD becomes a safety requirement rather than a pilot and passenger design convenience.Dual YDs are required and a failed YD is cause for limiting flight to lower altitude and lower Mach numbers.At high sltitude there is reduced aerodynamic damping due to high altitude low air density.At the lower altitudes Dutch Roll stability is improved.
Part 3 ...to be continued. "Turning performance".