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Why don't commercial aircraft use all-movable tail surfaces like my RC plane?
Clash Royale CLAN TAG#URR8PPP
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Many conventional RC planes use control surfaces at the tail just like the image below:
You can see there is a part in front of each surface control that never moves and only the surface control itself moves.
So, I built an rc plane without that part in front of the surface control. Take a look below:
This plane I built flies really well (no aileron). So I was wondering: why commercial aircrafts or even rc planes dont use this type of rudder/elevator without the part in front of it? See: making the control surface the way I did reduces drag since you dont have a fix part at the tail that does nothing, it reduces weight cause you just need the control surface and nothing more and it is also way easier to build. I cant understand why commercial aircrafts and rc planes dont make use of this exactly same type of rudder/elevator!
Could you please tell me the reason?
control-surfaces rudder tail elevator
edited 3 hours ago
Steve V.
14.1k464129
asked 3 hours ago
amandanovaes
1162
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show 2 more comments
up vote
3
down vote
favorite
Many conventional RC planes use control surfaces at the tail just like the image below:
You can see there is a part in front of each surface control that never moves and only the surface control itself moves.
So, I built an rc plane without that part in front of the surface control. Take a look below:
This plane I built flies really well (no aileron). So I was wondering: why commercial aircrafts or even rc planes dont use this type of rudder/elevator without the part in front of it? See: making the control surface the way I did reduces drag since you dont have a fix part at the tail that does nothing, it reduces weight cause you just need the control surface and nothing more and it is also way easier to build. I cant understand why commercial aircrafts and rc planes dont make use of this exactly same type of rudder/elevator!
Could you please tell me the reason?
control-surfaces rudder tail elevator
edited 3 hours ago
Steve V.
14.1k464129
asked 3 hours ago
amandanovaes
1162
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amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Some aircraft do (for the horizontal stab). The tail in my Cessna 177 is an "all flying tail", also called a stabilator. I haven't seen this for a vertical stabilizer, which I believe is because if it ever got stuck (which sometimes happens), a full-moving vertical stab would be uncontrollable. Most aircraft don't need that much rudder/elevator authority anyway, and the structure required to do that would be significant.
– Ron Beyer
3 hours ago
@Ron Beyer thanks. I checked the CESSNA 177 and the tail does not look like mine, it looks like a normal tail -> mms.tiger.tw/upload/2009-5/20095154522.jpg . Despite most aircrafts dont really need that much controls surface, on my case I realized I could easily cut my control surface in half and I would still have plenty of control. So that's another good point on my question, why most airfrats dont use the type of tail I built? I still cant understand cause this is so effective and I see no downside.
– amandanovaes
3 hours ago
Possible duplicate of What are the pros/cons of all-moving rudder?
– TomMcW
3 hours ago
1
That picture is of a model airplane and isn't accurate (at least not for the 177's that have it, some did not), here is what one looks like: goo.gl/images/gRUxDW . The downside is that there is still a lot of force there, and there has to be structure to hold it. It isn't much on an RC plane, but you are talking literally tons of force that have to be transferred to the fuselage (for an airliner).
– Ron Beyer
3 hours ago
The Lockheed TriStar L-1011 also has an "all flying tail" or stabilator if you want to see something commercial sized. Most airliners have a tail trim system that can move the entire tail some number of degrees, and the elevator takes care of the rest.
– Ron Beyer
2 hours ago
 |Â
show 2 more comments
up vote
3
down vote
favorite
up vote
3
down vote
favorite
Many conventional RC planes use control surfaces at the tail just like the image below:
You can see there is a part in front of each surface control that never moves and only the surface control itself moves.
So, I built an rc plane without that part in front of the surface control. Take a look below:
This plane I built flies really well (no aileron). So I was wondering: why commercial aircrafts or even rc planes dont use this type of rudder/elevator without the part in front of it? See: making the control surface the way I did reduces drag since you dont have a fix part at the tail that does nothing, it reduces weight cause you just need the control surface and nothing more and it is also way easier to build. I cant understand why commercial aircrafts and rc planes dont make use of this exactly same type of rudder/elevator!
Could you please tell me the reason?
control-surfaces rudder tail elevator
edited 3 hours ago
Steve V.
14.1k464129
asked 3 hours ago
amandanovaes
1162
New contributor
amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Many conventional RC planes use control surfaces at the tail just like the image below:
You can see there is a part in front of each surface control that never moves and only the surface control itself moves.
So, I built an rc plane without that part in front of the surface control. Take a look below:
This plane I built flies really well (no aileron). So I was wondering: why commercial aircrafts or even rc planes dont use this type of rudder/elevator without the part in front of it? See: making the control surface the way I did reduces drag since you dont have a fix part at the tail that does nothing, it reduces weight cause you just need the control surface and nothing more and it is also way easier to build. I cant understand why commercial aircrafts and rc planes dont make use of this exactly same type of rudder/elevator!
Could you please tell me the reason?
control-surfaces rudder tail elevator
control-surfaces rudder tail elevator
edited 3 hours ago
Steve V.
14.1k464129
asked 3 hours ago
amandanovaes
1162
New contributor
amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 3 hours ago
Steve V.
14.1k464129
asked 3 hours ago
amandanovaes
1162
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amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited 3 hours ago
Steve V.
14.1k464129
edited 3 hours ago
Steve V.
14.1k464129
edited 3 hours ago
Steve V.
14.1k464129
14.1k464129
asked 3 hours ago
amandanovaes
1162
New contributor
amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
amandanovaes
1162
asked 3 hours ago
amandanovaes
1162
1162
New contributor
amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
amandanovaes is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Some aircraft do (for the horizontal stab). The tail in my Cessna 177 is an "all flying tail", also called a stabilator. I haven't seen this for a vertical stabilizer, which I believe is because if it ever got stuck (which sometimes happens), a full-moving vertical stab would be uncontrollable. Most aircraft don't need that much rudder/elevator authority anyway, and the structure required to do that would be significant.
– Ron Beyer
3 hours ago
@Ron Beyer thanks. I checked the CESSNA 177 and the tail does not look like mine, it looks like a normal tail -> mms.tiger.tw/upload/2009-5/20095154522.jpg . Despite most aircrafts dont really need that much controls surface, on my case I realized I could easily cut my control surface in half and I would still have plenty of control. So that's another good point on my question, why most airfrats dont use the type of tail I built? I still cant understand cause this is so effective and I see no downside.
– amandanovaes
3 hours ago
Possible duplicate of What are the pros/cons of all-moving rudder?
– TomMcW
3 hours ago
1
That picture is of a model airplane and isn't accurate (at least not for the 177's that have it, some did not), here is what one looks like: goo.gl/images/gRUxDW . The downside is that there is still a lot of force there, and there has to be structure to hold it. It isn't much on an RC plane, but you are talking literally tons of force that have to be transferred to the fuselage (for an airliner).
– Ron Beyer
3 hours ago
The Lockheed TriStar L-1011 also has an "all flying tail" or stabilator if you want to see something commercial sized. Most airliners have a tail trim system that can move the entire tail some number of degrees, and the elevator takes care of the rest.
– Ron Beyer
2 hours ago
 |Â
show 2 more comments
Some aircraft do (for the horizontal stab). The tail in my Cessna 177 is an "all flying tail", also called a stabilator. I haven't seen this for a vertical stabilizer, which I believe is because if it ever got stuck (which sometimes happens), a full-moving vertical stab would be uncontrollable. Most aircraft don't need that much rudder/elevator authority anyway, and the structure required to do that would be significant.
– Ron Beyer
3 hours ago
@Ron Beyer thanks. I checked the CESSNA 177 and the tail does not look like mine, it looks like a normal tail -> mms.tiger.tw/upload/2009-5/20095154522.jpg . Despite most aircrafts dont really need that much controls surface, on my case I realized I could easily cut my control surface in half and I would still have plenty of control. So that's another good point on my question, why most airfrats dont use the type of tail I built? I still cant understand cause this is so effective and I see no downside.
– amandanovaes
3 hours ago
Possible duplicate of What are the pros/cons of all-moving rudder?
– TomMcW
3 hours ago
1
That picture is of a model airplane and isn't accurate (at least not for the 177's that have it, some did not), here is what one looks like: goo.gl/images/gRUxDW . The downside is that there is still a lot of force there, and there has to be structure to hold it. It isn't much on an RC plane, but you are talking literally tons of force that have to be transferred to the fuselage (for an airliner).
– Ron Beyer
3 hours ago
The Lockheed TriStar L-1011 also has an "all flying tail" or stabilator if you want to see something commercial sized. Most airliners have a tail trim system that can move the entire tail some number of degrees, and the elevator takes care of the rest.
– Ron Beyer
2 hours ago
Some aircraft do (for the horizontal stab). The tail in my Cessna 177 is an "all flying tail", also called a stabilator. I haven't seen this for a vertical stabilizer, which I believe is because if it ever got stuck (which sometimes happens), a full-moving vertical stab would be uncontrollable. Most aircraft don't need that much rudder/elevator authority anyway, and the structure required to do that would be significant.
– Ron Beyer
3 hours ago
Some aircraft do (for the horizontal stab). The tail in my Cessna 177 is an "all flying tail", also called a stabilator. I haven't seen this for a vertical stabilizer, which I believe is because if it ever got stuck (which sometimes happens), a full-moving vertical stab would be uncontrollable. Most aircraft don't need that much rudder/elevator authority anyway, and the structure required to do that would be significant.
– Ron Beyer
3 hours ago
@Ron Beyer thanks. I checked the CESSNA 177 and the tail does not look like mine, it looks like a normal tail -> mms.tiger.tw/upload/2009-5/20095154522.jpg . Despite most aircrafts dont really need that much controls surface, on my case I realized I could easily cut my control surface in half and I would still have plenty of control. So that's another good point on my question, why most airfrats dont use the type of tail I built? I still cant understand cause this is so effective and I see no downside.
– amandanovaes
3 hours ago
@Ron Beyer thanks. I checked the CESSNA 177 and the tail does not look like mine, it looks like a normal tail -> mms.tiger.tw/upload/2009-5/20095154522.jpg . Despite most aircrafts dont really need that much controls surface, on my case I realized I could easily cut my control surface in half and I would still have plenty of control. So that's another good point on my question, why most airfrats dont use the type of tail I built? I still cant understand cause this is so effective and I see no downside.
– amandanovaes
3 hours ago
Possible duplicate of What are the pros/cons of all-moving rudder?
– TomMcW
3 hours ago
Possible duplicate of What are the pros/cons of all-moving rudder?
– TomMcW
3 hours ago
1
1
That picture is of a model airplane and isn't accurate (at least not for the 177's that have it, some did not), here is what one looks like: goo.gl/images/gRUxDW . The downside is that there is still a lot of force there, and there has to be structure to hold it. It isn't much on an RC plane, but you are talking literally tons of force that have to be transferred to the fuselage (for an airliner).
– Ron Beyer
3 hours ago
That picture is of a model airplane and isn't accurate (at least not for the 177's that have it, some did not), here is what one looks like: goo.gl/images/gRUxDW . The downside is that there is still a lot of force there, and there has to be structure to hold it. It isn't much on an RC plane, but you are talking literally tons of force that have to be transferred to the fuselage (for an airliner).
– Ron Beyer
3 hours ago
The Lockheed TriStar L-1011 also has an "all flying tail" or stabilator if you want to see something commercial sized. Most airliners have a tail trim system that can move the entire tail some number of degrees, and the elevator takes care of the rest.
– Ron Beyer
2 hours ago
The Lockheed TriStar L-1011 also has an "all flying tail" or stabilator if you want to see something commercial sized. Most airliners have a tail trim system that can move the entire tail some number of degrees, and the elevator takes care of the rest.
– Ron Beyer
2 hours ago
 |Â
show 2 more comments
4 Answers
4
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up vote
1
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Well they do to a degree.
Large commercial aircraft have considerably larger CG ranges than their smaller counterparts do in order to accommodate a wide range of loadings as well as shifts in the Cp due to compresssibility effects at high Mach numbers and changes of AoA. To accommodate this, most airliners make use of a full moving tailplane for pitch trim, thence an additional elevator control surface is added for pitch authority by the pilot. This offers a compromise between excellent pitch and minimal drag and weight as opposed to actuating the entire tailplane. Now fully movable tailplanes for pitch control have been implemented before, as Ron Beyer points out in the L-1011. But it’s not very common.
answered 1 hour ago
Carlo Felicione
38.4k270143
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up vote
1
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For a small RC plane that travels at slow speeds your design would work great. However these type of designs have structural limitations. For an all movable vertical and horizontal stabilizer setup all the forces exerted on the control surfaces would be transferred to a movable bearing. This would be a single point of failure if the bearing were to fail. Normally the vertical stabilizer or horizontal stabilizer would use several bolts to attach it to the airframe. In some airplanes these control surfaces are welded on. This distributes the stresses more equally. I fly a Piper Cherokee with an all movable horizontal stabilizer (stabilator) and one of our pre-checks is to make sure there is no give in the bearing. If the bearing was to give out we would have a bad day.
answered 52 mins ago
DLH
1,952424
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up vote
0
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Some do, for example the entire elevator (on the tail) moves on an Airbus A330
answered 1 hour ago
Steve Kuo
1,194412
add a comment |Â
up vote
0
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The fixed tail surfaces are to provide a passive weathervaning effect for stability. If you have an all-flying tail, it tends to just want to trail into the airflow, so you need one of two things; hydraulic control, where the control surface is rigidly positioned by actuators and the control feel is by springs (The F-86 had an all flying hydraulically operated horizontal tail), or if non hydraulic, the surface needs an anti-servo tab (like the C-177 and just about every cable operated stabilator tail out there) to provide a speed sensitive restorative force that drives the surface to a certain position hand holds it there, and to provide a desirable stick force gradient (increasing force with displacement from trim speed). The anti-servo tab also provides the pitch trim function by changing its neutral point when you adjust the trim, changing the airplane's trim speed.
There are some gliders that have all flying tails with no servo tabs, and these depend on a bungee spring in the elevator control circuit for all of their stick free pitch stability. I used to fly a glider called an LS-1 that was like this, and the bungee wasn't particularly stiff, and the airplane was divergent in pitch if I let the stick go, but it was fine if I was holding it.
And airplane like the Cardinal or Cherokee, with a manually operated stabilator tail, would be pretty difficult to control without the anti-servo tab. The tab's control rod is a very critical inspection item on a pre-flight. The principal advantage of flying tails is more control authority for a given surface area (the Cardinal has MASSIVE tail power compared to similar aircraft), and the ability to fine tune the pitch feel gradient by how the anti-servo tab is geared.
Your RC airplane gets away with no anti-servo tab because the electric servos hold the surface at a given position. Basically the same as hydraulic
controls.
The Zenith family of homebuilts use an all-flying rudder with no fixed vertical fin. This wouldn't normally work so well without a fixed fin to provide a passive weathervaning force, but the Zenith gets away with it by having a very large fuselage vertical surface area aft of the wings. Otherwise it would have to have an anti-servo tab for the rudder in the absence of a vertical fin.
answered 46 mins ago
John K
9,7421030
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
Well they do to a degree.
Large commercial aircraft have considerably larger CG ranges than their smaller counterparts do in order to accommodate a wide range of loadings as well as shifts in the Cp due to compresssibility effects at high Mach numbers and changes of AoA. To accommodate this, most airliners make use of a full moving tailplane for pitch trim, thence an additional elevator control surface is added for pitch authority by the pilot. This offers a compromise between excellent pitch and minimal drag and weight as opposed to actuating the entire tailplane. Now fully movable tailplanes for pitch control have been implemented before, as Ron Beyer points out in the L-1011. But it’s not very common.
answered 1 hour ago
Carlo Felicione
38.4k270143
add a comment |Â
up vote
1
down vote
Well they do to a degree.
Large commercial aircraft have considerably larger CG ranges than their smaller counterparts do in order to accommodate a wide range of loadings as well as shifts in the Cp due to compresssibility effects at high Mach numbers and changes of AoA. To accommodate this, most airliners make use of a full moving tailplane for pitch trim, thence an additional elevator control surface is added for pitch authority by the pilot. This offers a compromise between excellent pitch and minimal drag and weight as opposed to actuating the entire tailplane. Now fully movable tailplanes for pitch control have been implemented before, as Ron Beyer points out in the L-1011. But it’s not very common.
answered 1 hour ago
Carlo Felicione
38.4k270143
add a comment |Â
up vote
1
down vote
up vote
1
down vote
Well they do to a degree.
Large commercial aircraft have considerably larger CG ranges than their smaller counterparts do in order to accommodate a wide range of loadings as well as shifts in the Cp due to compresssibility effects at high Mach numbers and changes of AoA. To accommodate this, most airliners make use of a full moving tailplane for pitch trim, thence an additional elevator control surface is added for pitch authority by the pilot. This offers a compromise between excellent pitch and minimal drag and weight as opposed to actuating the entire tailplane. Now fully movable tailplanes for pitch control have been implemented before, as Ron Beyer points out in the L-1011. But it’s not very common.
answered 1 hour ago
Carlo Felicione
38.4k270143
Well they do to a degree.
Large commercial aircraft have considerably larger CG ranges than their smaller counterparts do in order to accommodate a wide range of loadings as well as shifts in the Cp due to compresssibility effects at high Mach numbers and changes of AoA. To accommodate this, most airliners make use of a full moving tailplane for pitch trim, thence an additional elevator control surface is added for pitch authority by the pilot. This offers a compromise between excellent pitch and minimal drag and weight as opposed to actuating the entire tailplane. Now fully movable tailplanes for pitch control have been implemented before, as Ron Beyer points out in the L-1011. But it’s not very common.
answered 1 hour ago
Carlo Felicione
38.4k270143
answered 1 hour ago
Carlo Felicione
38.4k270143
answered 1 hour ago
Carlo Felicione
38.4k270143
answered 1 hour ago
Carlo Felicione
38.4k270143
38.4k270143
add a comment |Â
add a comment |Â
up vote
1
down vote
For a small RC plane that travels at slow speeds your design would work great. However these type of designs have structural limitations. For an all movable vertical and horizontal stabilizer setup all the forces exerted on the control surfaces would be transferred to a movable bearing. This would be a single point of failure if the bearing were to fail. Normally the vertical stabilizer or horizontal stabilizer would use several bolts to attach it to the airframe. In some airplanes these control surfaces are welded on. This distributes the stresses more equally. I fly a Piper Cherokee with an all movable horizontal stabilizer (stabilator) and one of our pre-checks is to make sure there is no give in the bearing. If the bearing was to give out we would have a bad day.
answered 52 mins ago
DLH
1,952424
add a comment |Â
up vote
1
down vote
For a small RC plane that travels at slow speeds your design would work great. However these type of designs have structural limitations. For an all movable vertical and horizontal stabilizer setup all the forces exerted on the control surfaces would be transferred to a movable bearing. This would be a single point of failure if the bearing were to fail. Normally the vertical stabilizer or horizontal stabilizer would use several bolts to attach it to the airframe. In some airplanes these control surfaces are welded on. This distributes the stresses more equally. I fly a Piper Cherokee with an all movable horizontal stabilizer (stabilator) and one of our pre-checks is to make sure there is no give in the bearing. If the bearing was to give out we would have a bad day.
answered 52 mins ago
DLH
1,952424
add a comment |Â
up vote
1
down vote
up vote
1
down vote
For a small RC plane that travels at slow speeds your design would work great. However these type of designs have structural limitations. For an all movable vertical and horizontal stabilizer setup all the forces exerted on the control surfaces would be transferred to a movable bearing. This would be a single point of failure if the bearing were to fail. Normally the vertical stabilizer or horizontal stabilizer would use several bolts to attach it to the airframe. In some airplanes these control surfaces are welded on. This distributes the stresses more equally. I fly a Piper Cherokee with an all movable horizontal stabilizer (stabilator) and one of our pre-checks is to make sure there is no give in the bearing. If the bearing was to give out we would have a bad day.
answered 52 mins ago
DLH
1,952424
For a small RC plane that travels at slow speeds your design would work great. However these type of designs have structural limitations. For an all movable vertical and horizontal stabilizer setup all the forces exerted on the control surfaces would be transferred to a movable bearing. This would be a single point of failure if the bearing were to fail. Normally the vertical stabilizer or horizontal stabilizer would use several bolts to attach it to the airframe. In some airplanes these control surfaces are welded on. This distributes the stresses more equally. I fly a Piper Cherokee with an all movable horizontal stabilizer (stabilator) and one of our pre-checks is to make sure there is no give in the bearing. If the bearing was to give out we would have a bad day.
answered 52 mins ago
DLH
1,952424
answered 52 mins ago
DLH
1,952424
answered 52 mins ago
DLH
1,952424
answered 52 mins ago
DLH
1,952424
1,952424
add a comment |Â
add a comment |Â
up vote
0
down vote
Some do, for example the entire elevator (on the tail) moves on an Airbus A330
answered 1 hour ago
Steve Kuo
1,194412
add a comment |Â
up vote
0
down vote
Some do, for example the entire elevator (on the tail) moves on an Airbus A330
answered 1 hour ago
Steve Kuo
1,194412
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Some do, for example the entire elevator (on the tail) moves on an Airbus A330
answered 1 hour ago
Steve Kuo
1,194412
Some do, for example the entire elevator (on the tail) moves on an Airbus A330
answered 1 hour ago
Steve Kuo
1,194412
answered 1 hour ago
Steve Kuo
1,194412
answered 1 hour ago
Steve Kuo
1,194412
answered 1 hour ago
Steve Kuo
1,194412
1,194412
add a comment |Â
add a comment |Â
up vote
0
down vote
The fixed tail surfaces are to provide a passive weathervaning effect for stability. If you have an all-flying tail, it tends to just want to trail into the airflow, so you need one of two things; hydraulic control, where the control surface is rigidly positioned by actuators and the control feel is by springs (The F-86 had an all flying hydraulically operated horizontal tail), or if non hydraulic, the surface needs an anti-servo tab (like the C-177 and just about every cable operated stabilator tail out there) to provide a speed sensitive restorative force that drives the surface to a certain position hand holds it there, and to provide a desirable stick force gradient (increasing force with displacement from trim speed). The anti-servo tab also provides the pitch trim function by changing its neutral point when you adjust the trim, changing the airplane's trim speed.
There are some gliders that have all flying tails with no servo tabs, and these depend on a bungee spring in the elevator control circuit for all of their stick free pitch stability. I used to fly a glider called an LS-1 that was like this, and the bungee wasn't particularly stiff, and the airplane was divergent in pitch if I let the stick go, but it was fine if I was holding it.
And airplane like the Cardinal or Cherokee, with a manually operated stabilator tail, would be pretty difficult to control without the anti-servo tab. The tab's control rod is a very critical inspection item on a pre-flight. The principal advantage of flying tails is more control authority for a given surface area (the Cardinal has MASSIVE tail power compared to similar aircraft), and the ability to fine tune the pitch feel gradient by how the anti-servo tab is geared.
Your RC airplane gets away with no anti-servo tab because the electric servos hold the surface at a given position. Basically the same as hydraulic
controls.
The Zenith family of homebuilts use an all-flying rudder with no fixed vertical fin. This wouldn't normally work so well without a fixed fin to provide a passive weathervaning force, but the Zenith gets away with it by having a very large fuselage vertical surface area aft of the wings. Otherwise it would have to have an anti-servo tab for the rudder in the absence of a vertical fin.
answered 46 mins ago
John K
9,7421030
add a comment |Â
up vote
0
down vote
The fixed tail surfaces are to provide a passive weathervaning effect for stability. If you have an all-flying tail, it tends to just want to trail into the airflow, so you need one of two things; hydraulic control, where the control surface is rigidly positioned by actuators and the control feel is by springs (The F-86 had an all flying hydraulically operated horizontal tail), or if non hydraulic, the surface needs an anti-servo tab (like the C-177 and just about every cable operated stabilator tail out there) to provide a speed sensitive restorative force that drives the surface to a certain position hand holds it there, and to provide a desirable stick force gradient (increasing force with displacement from trim speed). The anti-servo tab also provides the pitch trim function by changing its neutral point when you adjust the trim, changing the airplane's trim speed.
There are some gliders that have all flying tails with no servo tabs, and these depend on a bungee spring in the elevator control circuit for all of their stick free pitch stability. I used to fly a glider called an LS-1 that was like this, and the bungee wasn't particularly stiff, and the airplane was divergent in pitch if I let the stick go, but it was fine if I was holding it.
And airplane like the Cardinal or Cherokee, with a manually operated stabilator tail, would be pretty difficult to control without the anti-servo tab. The tab's control rod is a very critical inspection item on a pre-flight. The principal advantage of flying tails is more control authority for a given surface area (the Cardinal has MASSIVE tail power compared to similar aircraft), and the ability to fine tune the pitch feel gradient by how the anti-servo tab is geared.
Your RC airplane gets away with no anti-servo tab because the electric servos hold the surface at a given position. Basically the same as hydraulic
controls.
The Zenith family of homebuilts use an all-flying rudder with no fixed vertical fin. This wouldn't normally work so well without a fixed fin to provide a passive weathervaning force, but the Zenith gets away with it by having a very large fuselage vertical surface area aft of the wings. Otherwise it would have to have an anti-servo tab for the rudder in the absence of a vertical fin.
answered 46 mins ago
John K
9,7421030
add a comment |Â
up vote
0
down vote
up vote
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The fixed tail surfaces are to provide a passive weathervaning effect for stability. If you have an all-flying tail, it tends to just want to trail into the airflow, so you need one of two things; hydraulic control, where the control surface is rigidly positioned by actuators and the control feel is by springs (The F-86 had an all flying hydraulically operated horizontal tail), or if non hydraulic, the surface needs an anti-servo tab (like the C-177 and just about every cable operated stabilator tail out there) to provide a speed sensitive restorative force that drives the surface to a certain position hand holds it there, and to provide a desirable stick force gradient (increasing force with displacement from trim speed). The anti-servo tab also provides the pitch trim function by changing its neutral point when you adjust the trim, changing the airplane's trim speed.
There are some gliders that have all flying tails with no servo tabs, and these depend on a bungee spring in the elevator control circuit for all of their stick free pitch stability. I used to fly a glider called an LS-1 that was like this, and the bungee wasn't particularly stiff, and the airplane was divergent in pitch if I let the stick go, but it was fine if I was holding it.
And airplane like the Cardinal or Cherokee, with a manually operated stabilator tail, would be pretty difficult to control without the anti-servo tab. The tab's control rod is a very critical inspection item on a pre-flight. The principal advantage of flying tails is more control authority for a given surface area (the Cardinal has MASSIVE tail power compared to similar aircraft), and the ability to fine tune the pitch feel gradient by how the anti-servo tab is geared.
Your RC airplane gets away with no anti-servo tab because the electric servos hold the surface at a given position. Basically the same as hydraulic
controls.
The Zenith family of homebuilts use an all-flying rudder with no fixed vertical fin. This wouldn't normally work so well without a fixed fin to provide a passive weathervaning force, but the Zenith gets away with it by having a very large fuselage vertical surface area aft of the wings. Otherwise it would have to have an anti-servo tab for the rudder in the absence of a vertical fin.
answered 46 mins ago
John K
9,7421030
The fixed tail surfaces are to provide a passive weathervaning effect for stability. If you have an all-flying tail, it tends to just want to trail into the airflow, so you need one of two things; hydraulic control, where the control surface is rigidly positioned by actuators and the control feel is by springs (The F-86 had an all flying hydraulically operated horizontal tail), or if non hydraulic, the surface needs an anti-servo tab (like the C-177 and just about every cable operated stabilator tail out there) to provide a speed sensitive restorative force that drives the surface to a certain position hand holds it there, and to provide a desirable stick force gradient (increasing force with displacement from trim speed). The anti-servo tab also provides the pitch trim function by changing its neutral point when you adjust the trim, changing the airplane's trim speed.
There are some gliders that have all flying tails with no servo tabs, and these depend on a bungee spring in the elevator control circuit for all of their stick free pitch stability. I used to fly a glider called an LS-1 that was like this, and the bungee wasn't particularly stiff, and the airplane was divergent in pitch if I let the stick go, but it was fine if I was holding it.
And airplane like the Cardinal or Cherokee, with a manually operated stabilator tail, would be pretty difficult to control without the anti-servo tab. The tab's control rod is a very critical inspection item on a pre-flight. The principal advantage of flying tails is more control authority for a given surface area (the Cardinal has MASSIVE tail power compared to similar aircraft), and the ability to fine tune the pitch feel gradient by how the anti-servo tab is geared.
Your RC airplane gets away with no anti-servo tab because the electric servos hold the surface at a given position. Basically the same as hydraulic
controls.
The Zenith family of homebuilts use an all-flying rudder with no fixed vertical fin. This wouldn't normally work so well without a fixed fin to provide a passive weathervaning force, but the Zenith gets away with it by having a very large fuselage vertical surface area aft of the wings. Otherwise it would have to have an anti-servo tab for the rudder in the absence of a vertical fin.
answered 46 mins ago
John K
9,7421030
answered 46 mins ago
John K
9,7421030
answered 46 mins ago
John K
9,7421030
answered 46 mins ago
John K
9,7421030
9,7421030
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Some aircraft do (for the horizontal stab). The tail in my Cessna 177 is an "all flying tail", also called a stabilator. I haven't seen this for a vertical stabilizer, which I believe is because if it ever got stuck (which sometimes happens), a full-moving vertical stab would be uncontrollable. Most aircraft don't need that much rudder/elevator authority anyway, and the structure required to do that would be significant.
– Ron Beyer
3 hours ago
@Ron Beyer thanks. I checked the CESSNA 177 and the tail does not look like mine, it looks like a normal tail -> mms.tiger.tw/upload/2009-5/20095154522.jpg . Despite most aircrafts dont really need that much controls surface, on my case I realized I could easily cut my control surface in half and I would still have plenty of control. So that's another good point on my question, why most airfrats dont use the type of tail I built? I still cant understand cause this is so effective and I see no downside.
– amandanovaes
3 hours ago
Possible duplicate of What are the pros/cons of all-moving rudder?
– TomMcW
3 hours ago
1
That picture is of a model airplane and isn't accurate (at least not for the 177's that have it, some did not), here is what one looks like: goo.gl/images/gRUxDW . The downside is that there is still a lot of force there, and there has to be structure to hold it. It isn't much on an RC plane, but you are talking literally tons of force that have to be transferred to the fuselage (for an airliner).
– Ron Beyer
3 hours ago
The Lockheed TriStar L-1011 also has an "all flying tail" or stabilator if you want to see something commercial sized. Most airliners have a tail trim system that can move the entire tail some number of degrees, and the elevator takes care of the rest.
– Ron Beyer
2 hours ago