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#1
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Mounting a turn coordinator on the tail?
(Things are so slow in this group at the moment, I thought I'd post
this to get your input on something I've been mulling over...) If you put a plane into a skidding left turn (wings level) with left rudder, the ball on the panel goes to the right. However, I've been trying to work out what would happen to the ball if it was mounted on the tail. The rudder is pushing the tail of the plane to the right, so I think the ball would go to the left. Can anyone confirm this? Tim. |
#2
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Mounting a turn coordinator on the tail?
I don't think so. My understanding is the ball rests in a slightly
curved tube, arranged so that gravity tends to center it. Centrifugal force tries to move it to the outside of the skid, up the curved tube. Neither of these forces depends on where you mount the turn coordinator. Tim Auckland wrote: (Things are so slow in this group at the moment, I thought I'd post this to get your input on something I've been mulling over...) If you put a plane into a skidding left turn (wings level) with left rudder, the ball on the panel goes to the right. However, I've been trying to work out what would happen to the ball if it was mounted on the tail. The rudder is pushing the tail of the plane to the right, so I think the ball would go to the left. Can anyone confirm this? Tim. |
#3
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Mounting a turn coordinator on the tail?
Stubby,
Thanks, I think I've got it now. As the turn is initiated, the tail has to go right (this is what causes the plane to turn) and my guess is that the ball initially goes very slightly left. However, once a constant-radius turn has been achieved, the ball will be on the right (outside) of the turn. Tim. On Sat, 29 Jul 2006 18:28:28 -0400, Stubby wrote: I don't think so. My understanding is the ball rests in a slightly curved tube, arranged so that gravity tends to center it. Centrifugal force tries to move it to the outside of the skid, up the curved tube. Neither of these forces depends on where you mount the turn coordinator. Tim Auckland wrote: (Things are so slow in this group at the moment, I thought I'd post this to get your input on something I've been mulling over...) If you put a plane into a skidding left turn (wings level) with left rudder, the ball on the panel goes to the right. However, I've been trying to work out what would happen to the ball if it was mounted on the tail. The rudder is pushing the tail of the plane to the right, so I think the ball would go to the left. Can anyone confirm this? Tim. |
#4
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Mounting a turn coordinator on the tail?
What causes a plane to turn is the horizontal component of the lift
vector. It certainly does not depend on the turn coordinator. What counts is the center of gravity of the plane, not the tail. Tim Auckland wrote: Stubby, Thanks, I think I've got it now. As the turn is initiated, the tail has to go right (this is what causes the plane to turn) and my guess is that the ball initially goes very slightly left. However, once a constant-radius turn has been achieved, the ball will be on the right (outside) of the turn. Tim. On Sat, 29 Jul 2006 18:28:28 -0400, Stubby wrote: I don't think so. My understanding is the ball rests in a slightly curved tube, arranged so that gravity tends to center it. Centrifugal force tries to move it to the outside of the skid, up the curved tube. Neither of these forces depends on where you mount the turn coordinator. Tim Auckland wrote: (Things are so slow in this group at the moment, I thought I'd post this to get your input on something I've been mulling over...) If you put a plane into a skidding left turn (wings level) with left rudder, the ball on the panel goes to the right. However, I've been trying to work out what would happen to the ball if it was mounted on the tail. The rudder is pushing the tail of the plane to the right, so I think the ball would go to the left. Can anyone confirm this? Tim. |
#5
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Mounting a turn coordinator on the tail?
I've never quite bought in to the "horizontal component of lift"
explanation for what causes a plane to turn. I started this discussion talking about a "wings level skidding turn". There's no horizontal component of lift generated by the wings if the wings are level. There is however a couple comprising of the rightwards force from the rudder, and the induced leftwards force of wind resistance acting further forward along the fuselage. It's the couple which causes the plane to turn. I can also generate a substantial amount of horizontal force from the wings without the plane turning (think forward slip); it just moves sideways through the air. I believe what causes a plane to turn is the couple comprised of opposing forces which aren't aligned. For example, in a coordinated left turn, the wings generate a horizontal force to the left. The tail generates a horizontal force to the right. The forces aren't aligned, so a couple is generated, and the airplane turns left. Without a force to the right, the "horizontal component of lift" to the left generated by the banked wings would merely cause the plane to move left -- it wouldn't turn. Just my $0.10 worth, and I'll happily listen to contradictory arguments. Tim. On Sat, 29 Jul 2006 20:52:00 -0400, Stubby wrote: What causes a plane to turn is the horizontal component of the lift vector. It certainly does not depend on the turn coordinator. What counts is the center of gravity of the plane, not the tail. Tim Auckland wrote: Stubby, Thanks, I think I've got it now. As the turn is initiated, the tail has to go right (this is what causes the plane to turn) and my guess is that the ball initially goes very slightly left. However, once a constant-radius turn has been achieved, the ball will be on the right (outside) of the turn. Tim. On Sat, 29 Jul 2006 18:28:28 -0400, Stubby wrote: I don't think so. My understanding is the ball rests in a slightly curved tube, arranged so that gravity tends to center it. Centrifugal force tries to move it to the outside of the skid, up the curved tube. Neither of these forces depends on where you mount the turn coordinator. Tim Auckland wrote: (Things are so slow in this group at the moment, I thought I'd post this to get your input on something I've been mulling over...) If you put a plane into a skidding left turn (wings level) with left rudder, the ball on the panel goes to the right. However, I've been trying to work out what would happen to the ball if it was mounted on the tail. The rudder is pushing the tail of the plane to the right, so I think the ball would go to the left. Can anyone confirm this? Tim. |
#6
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Mounting a turn coordinator on the tail?
I started this discussion talking about a "wings level skidding turn".
There's no horizontal component of lift generated by the wings if the wings are level. There is however a couple comprising of the rightwards force from the rudder, and the induced leftwards force of wind resistance acting further forward along the fuselage. It's the couple which causes the plane to turn. There is also the fact that the thrust vector is more aligned with the direction of desired flight. I believe what causes a plane to turn is the couple comprised of opposing forces which aren't aligned. This is always true, for any acceleration not in the direct line of flight. There is no "one thing" which causes anything in aviation (except at the most fundamental level, where all flight is controlled by money). In a coordinated turn, there are several forces, as you pointed out. However, not all turns are coordinated. What makes a car turn? Are there analogs in aviation of these forces? Jose -- The monkey turns the crank and thinks he's making the music. for Email, make the obvious change in the address. |
#7
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Mounting a turn coordinator on the tail?
Stubby wrote:
What causes a plane to turn is the horizontal component of the lift vector. It certainly does not depend on the turn coordinator. What counts is the center of gravity of the plane, not the tail. BZZT. Incorrect over simplification and psuedoscientific drivel given by the FAA. If you believed the FAA description, then the airplane would just translate sidewise rather than turning in a circle. While the horizontal component of lift is what pulls you to the interior of the turn, the tail is VERY important to actually "turn" the aircraft direction so that the horizontal component continually gets pointed to the center of the turn. |
#8
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Mounting a turn coordinator on the tail?
On Mon, 31 Jul 2006 08:06:07 -0400, Ron Natalie
wrote: While the horizontal component of lift is what pulls you to the interior of the turn, the tail is VERY important to actually "turn" the aircraft direction ---------------------------------------- so that the horizontal component continually gets pointed to the center of the turn. ---------------------------------------- Now that's a VERY interesting way of thinking about it. What got me thinking about all this was the observation that I found it difficult to keep the ball exactly centered in a 50-degree bank, so I started thinking about whether it's even possible to do this in a 60-degree bank. In theory, in a 60-degree bank, the angle of attack, controlled by the elevator, has to be such that 2g of lift is generated. However, in a steep bank, the rate of turn is mostly controlled by the elevator. The rudder's forces are mostly acting vertically, so it has a large effect on whether the nose is pointing up or down. If you keep the nose roughly horizontal with the rudder, and 2g of lift with the elevator, you've no controls left to affect the rate of turn. Do the forces in this case work out such that the ball is centered? Any areobatic piliots out there? Is the ball typically centered in a 60-degree bank? Tim. |
#9
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Mounting a turn coordinator on the tail?
Ron Natalie wrote: Stubby wrote: What causes a plane to turn is the horizontal component of the lift vector. It certainly does not depend on the turn coordinator. What counts is the center of gravity of the plane, not the tail. ...opinion deleted... While the horizontal component of lift is what pulls you to the interior of the turn, the tail is VERY important to actually "turn" the aircraft direction so that the horizontal component continually gets pointed to the center of the turn. The elevator/rudder mechanism is for applying the torques to the plane so it rolls and yaws. Also, as I remember from the first day of physics class, a physical body behaves as a point mass at the center of gravity with 3 translational forces and 3 rotational torques that can be applied to it. The horizontal component of lift behaves like a string tied to a rock being swung around. The string does indeed apply force to the center of gravity of the rock and "points" to the center of the turn. If you put a paint spot on the rock and want to make the spot always face you, the rock will have to yaw at the same rate as you are rotating it around you; consequently something like a rudder will be needed. |
#10
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Mounting a turn coordinator on the tail?
Tim Auckland wrote:
(Things are so slow in this group at the moment, I thought I'd post this to get your input on something I've been mulling over...) If you put a plane into a skidding left turn (wings level) with left rudder, the ball on the panel goes to the right. However, I've been trying to work out what would happen to the ball if it was mounted on the tail. The rudder is pushing the tail of the plane to the right, so I think the ball would go to the left. Can anyone confirm this? Tim. If you are coordinated, the ball will be centered If you are slipping, or skidding, the ball will be just the same as if it was in the panel. Dave |
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