Coming Soon: Canards
10-21-2008, 10:50 AM
#136
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I'm still waiting for someone to tell me what would happen to a 928 with these canards installed on a treadmill.
10-21-2008, 11:58 AM
#138
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10-21-2008, 12:37 PM
#139
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On topic; no canards on Bird1.
10-21-2008, 01:01 PM
#140
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Discussing sail planes and airplanes is much like surfboards and power boats....the energy source is just not as obvious. The very best sailplanes are about 40 - 1, the Cesna is what 8 to 1 glide ratio unless they find a "wave" to ride they all are going DOWN 
My only two passenger flights in a sailplane were interesting. A very nice high performance tandem. The vibration from the tow plane was a suprise then the calm once the tow rope was released. I asked what the stall speed was so he pointed the noise up until we fell out of the sky . Silly me I asked how fast will it go ? so he pointed it straight down .....that seemed real fast I got two rides because the first one he found no thermals. Or maybe he had more "ballast" than he expected
My only two passenger flights in a sailplane were interesting. A very nice high performance tandem. The vibration from the tow plane was a suprise then the calm once the tow rope was released. I asked what the stall speed was so he pointed the noise up until we fell out of the sky . Silly me I asked how fast will it go ? so he pointed it straight down .....that seemed real fast I got two rides because the first one he found no thermals. Or maybe he had more "ballast" than he expected
10-21-2008, 01:24 PM
#141
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Movable aero devices are BANNED by most racing organizations...WHY ? because they would work. Mercedes in the 1950s had an "air brake" mounted on the back of a sports racer at the end of a long straight something about the size of the front door on your house hinged at the rear would pop up 90 degrees once the car slowed down enough it would crank down horizontal until the end of the next high speed straight. They ruled that it blocked the view of drivers behind the car plus probably scared the hell out of them when it suddenly popped up and the car slowed down very fast !
10-21-2008, 05:50 PM
#142
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10-21-2008, 05:57 PM
#143
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The point i was trying to make with my comments was that a plane needs negative lift, or downforce, if he wants to do an outside loop, or wants to go "down" in excess of the force of gravity. you can get an airplane to go down at greater than 0g, and even 1g or better, by use of the elevators,(canards on the rear of the airplane) or canards, (elevators on the front of the airplane)
Most people dont understand how fast a glider can be in a dive. high aspect ratios give them very low drag.
mk
Most people dont understand how fast a glider can be in a dive. high aspect ratios give them very low drag.
mk
Discussing sail planes and airplanes is much like surfboards and power boats....the energy source is just not as obvious. The very best sailplanes are about 40 - 1, the Cesna is what 8 to 1 glide ratio unless they find a "wave" to ride they all are going DOWN My only two passenger flights in a sailplane were interesting. A very nice high performance tandem. The vibration from the tow plane was a suprise then the calm once the tow rope was released. I asked what the stall speed was so he pointed the noise up until we fell out of the sky . Silly me I asked how fast will it go ? so he pointed it straight down .....that seemed real fast I got two rides because the first one he found no thermals. Or maybe he had more "ballast" than he expected
My only two passenger flights in a sailplane were interesting. A very nice high performance tandem. The vibration from the tow plane was a suprise then the calm once the tow rope was released. I asked what the stall speed was so he pointed the noise up until we fell out of the sky . Silly me I asked how fast will it go ? so he pointed it straight down .....that seemed real fast I got two rides because the first one he found no thermals. Or maybe he had more "ballast" than he expected
10-21-2008, 06:02 PM
#144
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You missed the point as well. if you want to escape thermals, you need negative lift, or downforce (as called on race cars). Wings and elevators/canards can allow for up to near 6G decent, where is falling is just 1G (or 0G depending on how you set the scale)
mk
mk
10-21-2008, 06:12 PM
#145
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Pilot was a nice guy when I commented on how quiet it was little sense of speed he cranked in some yaw and disrupted that smooth flow of air. Very interesting experience many years ago. On the landings it was clear that it really wanted to FLY
10-21-2008, 06:20 PM
#146
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BZZZT. Wrong answer. 1/2 credit. yes, if lift is less than weight the aircraft will ( or can) accelerate downward proportional to the net force due to gravity minus lift, + weight - drag. However, this is progressivly less as the airplane approachs terminal velocity. (remember,drag goes up with the square of speed. double the speed, quad the drag.)
Lift equal to weight creates steady altitude flight.
a steady rate of decent would equal a differential force of gravity and weight plus lift, and the force of drag dictating its terminal velocity.
The pilot must vary the elevator (canard) setting to keep any particular rate of decent constant ,
Mk
Lift equal to weight creates steady altitude flight.
a steady rate of decent would equal a differential force of gravity and weight plus lift, and the force of drag dictating its terminal velocity.
The pilot must vary the elevator (canard) setting to keep any particular rate of decent constant ,
Mk
10-21-2008, 06:29 PM
#147
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If you want to go down faster than 1 G, you just push down on the stick. you can then not only fall at 1G, you can fall at as fast as the airplane has structure to support negative Gs (as well as your brains ability to get the blood out! )
However, if you want to pull hard Gs, faster than just a free fall, you would do a combat aircraft manuver to reverse directions, and keep G loading positive on the wings. Learned from Birds, they roll over and do an "Emmelman".
However, negative Gs, such as found when doing an outside loop gets you down much faster than gravity, as you are then able to convert potetial energy of your airplane based on its altitude to kinetic energy (speed of decent) and fall (dive) far faster !
Again, the point is, wings can provide forces in both directions with a little help of pointing them in the desired AOA via canards, or elevators.
mk
)However, if you want to pull hard Gs, faster than just a free fall, you would do a combat aircraft manuver to reverse directions, and keep G loading positive on the wings. Learned from Birds, they roll over and do an "Emmelman".
However, negative Gs, such as found when doing an outside loop gets you down much faster than gravity, as you are then able to convert potetial energy of your airplane based on its altitude to kinetic energy (speed of decent) and fall (dive) far faster !
Again, the point is, wings can provide forces in both directions with a little help of pointing them in the desired AOA via canards, or elevators.
mk
to be pedantic if they want to get down, they need less lift than the force exerted by gravity giving a net downwards force. They still have wings producing lift even when descending, else they would fall straight out of the sky with an acceleration equal to nearly 1G.
Unless of course they fly inverted into a dive with an AoA which would cause "lift" in the direction of the pilots head in which case they can theoretically pull more than 1G downwards
Does anyone know if birds initiate a dive by rolling inverted to benefit from the downwards "lift"
Unless of course they fly inverted into a dive with an AoA which would cause "lift" in the direction of the pilots head in which case they can theoretically pull more than 1G downwards
Does anyone know if birds initiate a dive by rolling inverted to benefit from the downwards "lift"
10-21-2008, 08:56 PM
#148
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Lets leave the flying to the birds (and pilots) :P
Ok, where to start. There have been a couple of pages + worth of discussion on aircraft, downforce, birds, and all things aero and I'd like to contribute a little to clearing up some assumptions and misconceptions. I guess I can start with myself. I have a BS and MS in Aero, and I'm a test pilot with around 1500 hours in 30+ types of aircraft. Hopefully that's enough not to make a fool of myself. I'll start with a little basic aero and then address some of the earlier comments in this thread.
Basic aero (non-compressible flow) is fairly simple from a balance of forces view. In straight and level, unaccelerated flight. Lift = Weight, Drag = Thrust. Notice the emphasis. Anytime you change those two conditions, the above equalities break down and you have to use vector addition/subtraction to figure out what is going on. Some things to note about the four forces listed above - Weight always acts towards the center of the earth (i.e. down), lift always acts perpendicular (normal) to the wing (usually up). Drag always acts in the opposite direction from the velocity vector, and thrust always acts in the same direction as the velocity vector (Ok, not always [F-22 vectored thrust] - and we're assuming zero angle of attack for the following discussion)
I had a long discussion with various examples here, but this page explains it better: http://www.auf.asn.au/groundschool/index.html
Here's the pilot's version:
Ok, now I'll address comments:
More accurately, the vertical component of the lift vector is reduced below that of the weight. You can reduce it in a couple of ways. Slow down - lower velocity generates less lift. Bank - now the normal lift vector is off to the side of pure vertical, so the vertical component is smaller, so the plane decends. Push the nose over - same thing.
Now, here's where the crux is. Once you have the vertical velocity desired, you re-establish the balance of forces, and stop accelerating.
The same plane in a constant velocity descent is shown on the page linked earlier.
Correct.
Birds generally pull in their wings, reducing the surface area, reducing the lift, to start a dive.
Not entirely true, the correct vector sum for the vertical portion of a steady rate of descent is this:
(Vertical component of Lift) + (Vertical component of Drag [up] ) = Weight + (Vertical component of Thrust [down] )
This is fundamentally incorrect. Elevators and canards are used to balance an aircraft about its' center of gravity. Here is a good picture:
Of note is a conventional tail has downforce, and a canard will always have upforce (lift) due to the balance about the CG.
When the elevators (or canards) are moved, it rotates the aircraft about its' center of gravity putting the main wing at a different angle of attack to the relative wind. This change is angle of attack is what causes the aircraft to climb or decend.
Only half score here Mark. High aspect ratio wings have lower induced drag, but higher parasite drag (compared to a lower aspect ratio wing with the same surface area). And because of the high aspect ratio wings, gliders generally have a lower maximum allowable airspeed before the wings rip off.
Nope, as stated earlier, you just need to reduce your vertical component of lift, which can be done in a number of ways.
Yikes! Repeat after me: Airplanes don't fall - they accelerate down (unless the wing "stalls" and makes no lift). Also, if you are "falling ballistically", then you (the observer/pilot/aircraft) experiences 0 g.
Most tactical (fighter) aircraft are stressed to +9/-3 g. Why? Because the human body can stand about those limits. So if you want to get down in a hurry, you roll inverted, and pull 9g. If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)
And birds don't really do this.
Bingo!
Hope this clears some things up.
Cheers!
-Jason
Basic aero (non-compressible flow) is fairly simple from a balance of forces view. In straight and level, unaccelerated flight. Lift = Weight, Drag = Thrust. Notice the emphasis. Anytime you change those two conditions, the above equalities break down and you have to use vector addition/subtraction to figure out what is going on. Some things to note about the four forces listed above - Weight always acts towards the center of the earth (i.e. down), lift always acts perpendicular (normal) to the wing (usually up). Drag always acts in the opposite direction from the velocity vector, and thrust always acts in the same direction as the velocity vector (Ok, not always [F-22 vectored thrust] - and we're assuming zero angle of attack for the following discussion)
I had a long discussion with various examples here, but this page explains it better: http://www.auf.asn.au/groundschool/index.html
Here's the pilot's version:
Ok, now I'll address comments:
Now, here's where the crux is. Once you have the vertical velocity desired, you re-establish the balance of forces, and stop accelerating.
The same plane in a constant velocity descent is shown on the page linked earlier.
Unless of course they fly inverted into a dive with an AoA which would cause "lift" in the direction of the pilots head in which case they can theoretically pull more than 1G downwards
Does anyone know if birds initiate a dive by rolling inverted to benefit from the downwards "lift"
Does anyone know if birds initiate a dive by rolling inverted to benefit from the downwards "lift"
Birds generally pull in their wings, reducing the surface area, reducing the lift, to start a dive.
(Vertical component of Lift) + (Vertical component of Drag [up] ) = Weight + (Vertical component of Thrust [down] )
The point i was trying to make with my comments was that a plane needs negative lift, or downforce, if he wants to do an outside loop, or wants to go "down" in excess of the force of gravity. you can get an airplane to go down at greater than 0g, and even 1g or better, by use of the elevators,(canards on the rear of the airplane) or canards, (elevators on the front of the airplane)
Of note is a conventional tail has downforce, and a canard will always have upforce (lift) due to the balance about the CG.
When the elevators (or canards) are moved, it rotates the aircraft about its' center of gravity putting the main wing at a different angle of attack to the relative wind. This change is angle of attack is what causes the aircraft to climb or decend.
If you want to go down faster than 1 G, you just push down on the stick. you can then not only fall at 1G, you can fall at as fast as the airplane has structure to support negative Gs (as well as your brains ability to get the blood out! )
However, if you want to pull hard Gs, faster than just a free fall, you would do a combat aircraft manuver to reverse directions, and keep G loading positive on the wings. Learned from Birds, they roll over and do an "Emmelman".
However, negative Gs, such as found when doing an outside loop gets you down much faster than gravity, as you are then able to convert potetial energy of your airplane based on its altitude to kinetic energy (speed of decent) and fall (dive) far faster !
)However, if you want to pull hard Gs, faster than just a free fall, you would do a combat aircraft manuver to reverse directions, and keep G loading positive on the wings. Learned from Birds, they roll over and do an "Emmelman".
However, negative Gs, such as found when doing an outside loop gets you down much faster than gravity, as you are then able to convert potetial energy of your airplane based on its altitude to kinetic energy (speed of decent) and fall (dive) far faster !
Most tactical (fighter) aircraft are stressed to +9/-3 g. Why? Because the human body can stand about those limits. So if you want to get down in a hurry, you roll inverted, and pull 9g. If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)
And birds don't really do this.
Hope this clears some things up.
Cheers!
-Jason
10-21-2008, 11:52 PM
#149
Instructor
I have a Bachelor of Engineering Degree in Aeronautical Engineering, so none of this is news to me. All I was trying to do was to point out - simply - that the assertion that an aircraft needs to maintain nett downforce to descend is fundamentally incorrect.
10-21-2008, 11:59 PM
#150
Rennlist Member
re
Here is my response
This is fundamentally incorrect. Elevators and canards are used to balance an aircraft about its' center of gravity. Here is a good picture:
Of note is a conventional tail has downforce, and a canard will always have upforce (lift) due to the balance about the CG.
When the elevators (or canards) are moved, it rotates the aircraft about its' center of gravity putting the main wing at a different angle of attack to the relative wind. This change is angle of attack is what causes the aircraft to climb or decend.
You must have misunderstood the comment. elevators and canards are used to set the angle of attack of the main wing. You say what i have said, at the end of your statement.
Also, a canard and and elevators can have downforce or up force depending of whether you want their forces to lift the nose or the tail up or down. on straight and level flight you are right .
you keep on loosing the point of the entire discussion. its about, what do the wings or canards do on the front of a car or airplane ?
Only half score here Mark. High aspect ratio wings have lower induced drag, but higher parasite drag (compared to a lower aspect ratio wing with the same surface area). And because of the high aspect ratio wings, gliders generally have a lower maximum allowable airspeed before the wings rip off.
Your point about the gliders. I mentioned that the limit of gliders speed was a structural limitation. thanks for the half credit though!
Nope, as stated earlier, you just need to reduce your vertical component of lift, which can be done in a number of ways.
veritical component of lift, or negative lift, or downforce, arent they the same thing? semantics! common, if you are going to be a know-it-all, you are going to have to do better than that.
Yikes! Repeat after me: Airplanes don't fall - they accelerate down (unless the wing "stalls" and makes no lift). Also, if you are "falling ballistically", then you (the observer/pilot/aircraft) experiences 0 g.
Most tactical (fighter) aircraft are stressed to +9/-3 g. Why? Because the human body can stand about those limits. So if you want to get down in a hurry, you roll inverted, and pull 9g. If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)
The point was is that you can pull negative Gs and go down faster than the force of gravity. that was the ONLY point of that. Now, airplanes dont fall? what the heck does that mean? if you are in a dive, you accelerate at a rate of 32f/s/s, (in a vacuum) however,not in a vacuum you will accelerate at some lower rate due to the net force going down as speed increases. at terminal velocity, (somewhere generally, between 140 and 200mph), you dont accelerate anymore, and you as the pilot will experience 1g again. I ment to say a reverse split S which i thought was a half roll and a positive G dive. I think you say the same thing twice above referencing an Immelmann manuever. you pull up and do a half roll at the end of you half loop.
Bingo!
yep, its what i said in the prior posts.
This is not complicated, this is aero 101 stuff. Im trying to make the point that canards and elevators are airfoils and can create negative lift, even if they are asymetrical air foils.
Hope this clears some things up.
Cheers!
-Jason
This is fundamentally incorrect. Elevators and canards are used to balance an aircraft about its' center of gravity. Here is a good picture:
Of note is a conventional tail has downforce, and a canard will always have upforce (lift) due to the balance about the CG.
When the elevators (or canards) are moved, it rotates the aircraft about its' center of gravity putting the main wing at a different angle of attack to the relative wind. This change is angle of attack is what causes the aircraft to climb or decend.
You must have misunderstood the comment. elevators and canards are used to set the angle of attack of the main wing. You say what i have said, at the end of your statement.
Also, a canard and and elevators can have downforce or up force depending of whether you want their forces to lift the nose or the tail up or down. on straight and level flight you are right .
you keep on loosing the point of the entire discussion. its about, what do the wings or canards do on the front of a car or airplane ?
Only half score here Mark. High aspect ratio wings have lower induced drag, but higher parasite drag (compared to a lower aspect ratio wing with the same surface area). And because of the high aspect ratio wings, gliders generally have a lower maximum allowable airspeed before the wings rip off.
Your point about the gliders. I mentioned that the limit of gliders speed was a structural limitation. thanks for the half credit though!
Nope, as stated earlier, you just need to reduce your vertical component of lift, which can be done in a number of ways.
veritical component of lift, or negative lift, or downforce, arent they the same thing? semantics! common, if you are going to be a know-it-all, you are going to have to do better than that.
Yikes! Repeat after me: Airplanes don't fall - they accelerate down (unless the wing "stalls" and makes no lift). Also, if you are "falling ballistically", then you (the observer/pilot/aircraft) experiences 0 g.
Most tactical (fighter) aircraft are stressed to +9/-3 g. Why? Because the human body can stand about those limits. So if you want to get down in a hurry, you roll inverted, and pull 9g. If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)
The point was is that you can pull negative Gs and go down faster than the force of gravity. that was the ONLY point of that. Now, airplanes dont fall? what the heck does that mean? if you are in a dive, you accelerate at a rate of 32f/s/s, (in a vacuum) however,not in a vacuum you will accelerate at some lower rate due to the net force going down as speed increases. at terminal velocity, (somewhere generally, between 140 and 200mph), you dont accelerate anymore, and you as the pilot will experience 1g again. I ment to say a reverse split S which i thought was a half roll and a positive G dive. I think you say the same thing twice above referencing an Immelmann manuever. you pull up and do a half roll at the end of you half loop.
Bingo!
yep, its what i said in the prior posts.
This is not complicated, this is aero 101 stuff. Im trying to make the point that canards and elevators are airfoils and can create negative lift, even if they are asymetrical air foils.
Hope this clears some things up.
Cheers!
-Jason
Last edited by mark kibort; 10-22-2008 at 12:55 AM.