supersonic no more
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How is Aerion overcoming this problem which is inherent to that configuration?
I believe part of the solution is to increase pitch and yaw stability by having a larger tail. Stability augmentation (similar to a yaw damper) can also be used.
There have been a lot of new aircraft projects that failed to make it past the prototype phase (many didn't even make it that far - including the Boeing SST). The cost and regulatory challenges to a supersonic commercial aircraft are massive. As I've noted the changes to the FAR and JAR/CS since the 1970s will make it incredibly difficult to certify a supersonic capable bis jet.
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We've had unstable aircraft with computer-controlled control surfaces for over 40 years, the inherent inertia coupling tendencies will be controlled by that same philosophy.
Last edited by KenV; 18th Nov 2015 at 21:05.
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Then there was the Lockheed Starfighter.
It is generally recognised that coupling can be ameliorated by,
1. increased directional stability
2. reducing dihedral effect
3. minimising the inclination of the inertia axis at normal flight conditions
4. reducing undesirable aerodynamic coupling
5. limiting roll rate, roll duration, and angle of attack or load factor for performing roll manoeuvres
The typical high speed aircraft has some sort of roll performance limitation by flight restrictions or automatic control device to prevent reaching some critical condition from which recovery is impossible.
I can't think of any manoeuvre on an aircraft such as this where coupling could be an issue, and assume modern flight control computer systems would look after point (5). They won't be doing twinkle rolls. With Airbus part of the team, whatever is the product produced I'm sure you could take it to the bank.
1. increased directional stability
2. reducing dihedral effect
3. minimising the inclination of the inertia axis at normal flight conditions
4. reducing undesirable aerodynamic coupling
5. limiting roll rate, roll duration, and angle of attack or load factor for performing roll manoeuvres
The typical high speed aircraft has some sort of roll performance limitation by flight restrictions or automatic control device to prevent reaching some critical condition from which recovery is impossible.
I can't think of any manoeuvre on an aircraft such as this where coupling could be an issue, and assume modern flight control computer systems would look after point (5). They won't be doing twinkle rolls. With Airbus part of the team, whatever is the product produced I'm sure you could take it to the bank.
Well if cost is no object and these people are so incredible important they won't have any problem with a 100% VAT paid at the location of manufacture (not some rinky dinky modern day pirate haven place of registration) will they?
No one is that important, although some people might think they are; if Putin and Obama can make do with subsonics and telecoms links so can they.
On a less bitter note, it looks like it might be a bit of a hot ship to handle at low speed, would it be able to get into Citation sized airfields.
No one is that important, although some people might think they are; if Putin and Obama can make do with subsonics and telecoms links so can they.
On a less bitter note, it looks like it might be a bit of a hot ship to handle at low speed, would it be able to get into Citation sized airfields.
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The future will tell what will become of this project.
Seem interesting though and I wish all the luck for those involved.
But I couldn't help myself posting this little picture. I Think that some of you will get it and maybe laugh a little!
Edit: Type-o
Seem interesting though and I wish all the luck for those involved.
But I couldn't help myself posting this little picture. I Think that some of you will get it and maybe laugh a little!
Edit: Type-o
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On a less bitter note, it looks like it might be a bit of a hot ship to handle at low speed, would it be able to get into Citation sized airfields.
What sort of altitude are they planning to fly this thing? Concorde was pretty much on its own up at FL600 where it didn't have to worry about other traffic, I'm guessing this will be flying lower
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Yes the faster you go, the higher you need to fly.
Since the AS2 won't fly as fast as the Concorde, its optimal altitude should be closer to FL450, with service ceiling around FL510.
Since the AS2 won't fly as fast as the Concorde, its optimal altitude should be closer to FL450, with service ceiling around FL510.
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Well if cost is no object and these people are so incredible important they won't have any problem with a 100% VAT paid at the location of manufacture
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What you say does not hold for supersonic flight.
i) The speed of sound is a function of air temperature ONLY.
ii) Temperature remains constant from the beginning of the stratosphere up to 65000 feet, after which the temperature increases again.
i) The speed of sound is a function of air temperature ONLY.
ii) Temperature remains constant from the beginning of the stratosphere up to 65000 feet, after which the temperature increases again.
Being higher, at fixed IMN, will reduce sigma, which will increase the difference between TAS and EAS. In the fixed temperature region of the stratosphere then, the higher you are, whilst TAS will stay fixed, EAS will go down, reducing aerodynamic loads on the aircraft, and potentially drag and thus fuel burn required.
So the higher the better, so long as it stays within the lower stratosphere, and there may be some value in creeping into the middle stratosphere a bit.
I think, it's late, might come back and check my maths in the morning.
G
So the higher the better, so long as it stays within the lower stratosphere, and there may be some value in creeping into the middle stratosphere a bit.
I think, it's late, might come back and check my maths in the morning.
G
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Well if cost is no object and these people are so incredible important they won't have any problem with a 100% VAT paid at the location of manufacture
It's a big world.
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What you say does not hold for supersonic flight.
Aerion make no mention that I can see of planned altitude capability, though they mention approach speeds will be less than 135 Knots.
An interesting paper on inertia coupling, X-2, X-15 and Space Shuttle
http://www.nasa.gov/centers/dryden/p...ain_H-2106.pdf
An interesting paper on inertia coupling, X-2, X-15 and Space Shuttle
http://www.nasa.gov/centers/dryden/p...ain_H-2106.pdf
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This is not the same as aerodynamic instability. This is an inertial instability. It is caused by forces of a rotating mass overpowering the forces of an aerodynamic surface. No amount of computer sophistication can overcome this instability. The aerodynamic control surfaces must be enlarged. Further, look at any relaxed stability aircraft and you will see large control surfaces. Software alone cannot generate the large forces required to maintain control. The software needs powerful control surfaces to work with. Those do not appear to be present on the Aerion AS2.
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If I remember correctly, one of the first warnings the Columbia crew had of impending doom was the low fuel level in the thrusters that were compensating for a molten wing.
For those questioning the economics, not what you would call overwhelming though.
Supersonic Bizjet Math Makes Sense Now, Says Analyst | Business Aviation News: Aviation International News
You can by not allowing the aircraft to encroach the areas where the instability will manifest itself. Think envelope protection, as used in the Airbus. As I previously posted,
In essence, it's not a lot different to the relaxed stability aircraft we have now. A less stable aircraft requires smaller control surfaces, and deflections, to initiate maneuvering; consequently drag and control surface imposed stresses will be reduced and aircraft responsiveness will be enhanced. Since these characteristics will typically make control by the pilot difficult or impossible, an artificial stability will typically be imposed using computers, servos, and sensors as parts of a fly by wire control system.
Supersonic Bizjet Math Makes Sense Now, Says Analyst | Business Aviation News: Aviation International News
No amount of computer sophistication can overcome this instability
coupling can be ameliorated by limiting roll rate, roll duration, and angle of attack or load factor for performing roll manoeuvres
The typical high speed aircraft has some sort of roll performance limitation by flight restrictions or automatic control device to prevent reaching some critical condition from which recovery is impossible.
The typical high speed aircraft has some sort of roll performance limitation by flight restrictions or automatic control device to prevent reaching some critical condition from which recovery is impossible.