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#1
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Does the elevator/stabilator generate upward force?
Ok, this is a followup to the previous discussion about forward control
pressure during the landing rollout. Can someone tell me if the elevator/stabilator can actually generate an _upward_ force, or does it simply generate a downward force for climbing and less downward force for a decent? Does the nose fall due to the CG being forward of the center of lift, or does the elevator actually push the tail up? We are talking about tricycle gear planes, not taildraggers... The PA28 series specifically. --Dan |
#2
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Does the elevator/stabilator generate upward force?
You tell me...
Next time you are doing your run up.. hold the brakes and move the control foward and aft.. is the nose rising and falling because of action of wind (prop wash) over the elevator position? Granted in a heavy PA28, it may not be very noticable, but try it in a Cessna 152/172. you are mixing apples in oranges when talking about "the nose falling due to CG and center of lift". IIRC the original thread was concerned with pushing the nose down to put more weight on the nose wheel for cross wind control, in the example you mention, it involves the nose falling forward because the elevator/wings combination cannot generate enough "lift" in their respective direction to keep the nose up. Now.. lets expand on that a bit.. when performing an outside loop maneuver, is the nose being pushed around the loop because the elevator is creating less "lift" or because the elevator is forcing the nose around. Why would a tricycle gear airplane behave any differently than a tail wheel as far as elevator effectiveness. Other than possible physical limits allowed to elevator travel. In the only Piper POH I have avalible to be right now, On landing... ""After ground contract hold the nose wheel off as long as possible. Braking is most effective when back pressure is applied to the control wheel. In high wind conditions, particularly in strong crosswinds, it may be desirable to approach the ground at highter than normal speeds with partial or no flaps." Funny, it says nothing about pushing forward on the stick for directional control. B "Dan" wrote in message ups.com... Ok, this is a followup to the previous discussion about forward control pressure during the landing rollout. Can someone tell me if the elevator/stabilator can actually generate an _upward_ force, or does it simply generate a downward force for climbing and less downward force for a decent? Does the nose fall due to the CG being forward of the center of lift, or does the elevator actually push the tail up? We are talking about tricycle gear planes, not taildraggers... The PA28 series specifically. --Dan |
#3
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Does the elevator/stabilator generate upward force?
The tail can produce forces in either direction, although in
flight forces are mostly in the down direction at the tail. The wing lift is concentrated aft of the CG so that there is a nose down moment when the airplane becomes stalled. This is for static stability. The initial movement for statically stable airplanes must be toward a unstalled angle of attack and flying speed. This happens with the tail moment leveraging the turning moments to a balanced dynamic position, which will decrease at lower speeds, causing the static pitching moment downward. But it can produce an upward force if the airplane is aft of the CG range, in order to balance the airplane in flight. But if you stall, the nose will pitch up into a deeper stalled condition. On landing the airplane will rotate [pitch] around the main wheel axles and even the nose wheel which is wheel barrowing. The magnitude all depends on the center of gravity in relation to the CG range and the amount of travel exerted. Normal flight is very small movements and acrobatics, and control forces below stall speed on the ground use control displacements for gross changes. The issue is not tail draggers, but tail or canard, the location of the wheels in relation to the CG [wing chord] only has to do with finer details, like rolling. "Dan" wrote in message ups.com... | Ok, this is a followup to the previous discussion about forward control | pressure during the landing rollout. Can someone tell me if the | elevator/stabilator can actually generate an _upward_ force, or does it | simply generate a downward force for climbing and less downward force | for a decent? | | Does the nose fall due to the CG being forward of the center of lift, | or does the elevator actually push the tail up? | | We are talking about tricycle gear planes, not taildraggers... The PA28 | series specifically. | | --Dan | |
#4
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Does the elevator/stabilator generate upward force?
Think loop: outside or inside.
"Dan" wrote in message ups.com... | Ok, this is a followup to the previous discussion about forward control | pressure during the landing rollout. Can someone tell me if the | elevator/stabilator can actually generate an _upward_ force, or does it | simply generate a downward force for climbing and less downward force | for a decent? | | Does the nose fall due to the CG being forward of the center of lift, | or does the elevator actually push the tail up? | | We are talking about tricycle gear planes, not taildraggers... The PA28 | series specifically. | | --Dan | |
#5
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Does the elevator/stabilator generate upward force?
"you are mixing apples in oranges when talking about "the
nose falling due to | CG and center of lift". | IIRC the original thread was concerned with pushing the nose down to put | more weight on the nose wheel for cross wind control," Increased weight on the nose wheel makes the nose wheel the pivot point and is guaranteed to cause loss of direct WHEELBARROWING Page 8-32 http://www.faa.gov/library/manuals/a...lane_handbook/ chap 7-9 When a pilot permits the airplane weight to become concentrated about the nosewheel during the takeoff or landing roll, a condition known as wheelbarrowing will occur. Wheelbarrowing may cause loss of directional control during the landing roll because braking action is ineffective, and the airplane tends to swerve or pivot on the nosewheel, particularly in crosswind conditions. One of the most common causes of wheelbarrowing during the landing roll is a simultaneous touchdown of the main and nosewheel, with excessive speed, followed by application of forward pressure on the elevator control. Usually, the situation can be corrected by smoothly applying back-elevator pressure. However, if wheelbarrowing is encountered and runway and other conditions permit, it may be advisable to promptly initiate a go-around. Wheelbarrowing will not occur if the pilot achieves and maintains the correct landing attitude, touches down at the proper speed, and gently lowers the nosewheel while losing speed on rollout. If the pilot decides to stay on the ground rather than attempt a go-around or if directional control is lost, the throttle should be closed and the pitch attitude smoothly but firmly rotated to the proper landing attitude. Raise the flaps to reduce lift and to increase the load on the main wheels for better braking action. "BT" wrote in message ... | You tell me... | | Next time you are doing your run up.. hold the brakes and move the control | foward and aft.. is the nose rising and falling because of action of wind | (prop wash) over the elevator position? Granted in a heavy PA28, it may not | be very noticable, but try it in a Cessna 152/172. | | you are mixing apples in oranges when talking about "the nose falling due to | CG and center of lift". | IIRC the original thread was concerned with pushing the nose down to put | more weight on the nose wheel for cross wind control, | in the example you mention, it involves the nose falling forward because the | elevator/wings combination cannot generate enough "lift" in their respective | direction to keep the nose up. | | Now.. lets expand on that a bit.. when performing an outside loop maneuver, | is the nose being pushed around the loop because the elevator is creating | less "lift" or because the elevator is forcing the nose around. | | Why would a tricycle gear airplane behave any differently than a tail wheel | as far as elevator effectiveness. Other than possible physical limits | allowed to elevator travel. | | In the only Piper POH I have avalible to be right now, On landing... ""After | ground contract hold the nose wheel off as long as possible. Braking is most | effective when back pressure is applied to the control wheel. In high wind | conditions, particularly in strong crosswinds, it may be desirable to | approach the ground at highter than normal speeds with partial or no flaps." | | Funny, it says nothing about pushing forward on the stick for directional | control. | | B | | "Dan" wrote in message | ups.com... | Ok, this is a followup to the previous discussion about forward control | pressure during the landing rollout. Can someone tell me if the | elevator/stabilator can actually generate an _upward_ force, or does it | simply generate a downward force for climbing and less downward force | for a decent? | | Does the nose fall due to the CG being forward of the center of lift, | or does the elevator actually push the tail up? | | We are talking about tricycle gear planes, not taildraggers... The PA28 | series specifically. | | --Dan | | | |
#6
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Does the elevator/stabilator generate upward force?
"Dan" wrote in message
ups.com... [...] We are talking about tricycle gear planes, not taildraggers... The PA28 series specifically. Where the landing gear is mounted has nothing to do with the forces that the elevator creates. Several designs are basically identical, except for the position of the landing gear (Pacer and Tri-Pacer, for example). And yes, the elevator can create an upward force. |
#7
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Does the elevator/stabilator generate upward force?
I'm kind of alarmed to hear that an instructor didn't explain to you
that the elevator generates lift. |
#8
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Does the elevator/stabilator generate upward force?
wrote in message
ps.com... I'm kind of alarmed to hear that an instructor didn't explain to you that the elevator generates lift. To whom are you replying? If me, I have no idea what you're talking about. Your reply has nothing to do with what I wrote. If you're not replying to me, then I suggest you learn how to reply to the message to which you intend to reply, or at a minimum learn how to *quote* the text to which you're replying, so that people can tell what the heck you're talking about. Pete |
#9
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Does the elevator/stabilator generate upward force?
Peter Duniho wrote: wrote in message ps.com... I'm kind of alarmed to hear that an instructor didn't explain to you that the elevator generates lift. To whom are you replying? If me, I have no idea what you're talking about. Your reply has nothing to do with what I wrote. If you're not replying to me, then I suggest you learn how to reply to the message to which you intend to reply, or at a minimum learn how to *quote* the text to which you're replying, so that people can tell what the heck you're talking about. Pete Not you... Dan. |
#10
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Does the elevator/stabilator generate upward force?
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