Re: New JF-17/FC-1 Fighter Aircraft thread
LOL. I did not say that the F-15 is unstable. I am saying it struck you that it has combined electronic and mechanical controls.
Read the text again. That is incorrect.
What's being done here is quite similar to what airliners use for their FBW which is a feedback and response system running according to control rules.
Based on your definition, analog FBW would not be "intelligent" at all either because that's not much different from analog FBW.
LOL. Can you define what partial FBW means eh?
You're playing desperately with words. What does partial FBW means? It would have meant fractional control between manual and electronic controls. How is that much different from control and stability augmentation/intervention? There is no such things as "partial" FBW because that is a contradiction in meaning, hence you won't see any industry usage of that term.
Except that the industry does not use the term "partial" FBW because suchv a term is self contradictory on its own meaning. The F-20 tried to use it because of "marketing", but it really is hybrid.
Nonsense logic, to use certification times as "proof" that the plane cannot be unstable.
I've already destroyed that logic with real examples, such as how quickly the YF-16, YF-17, X-32, and X-35 are doing aerobatics right off from their earliest prototypes. And along with the F-CK-1 fighter which went from prototype to certification in only three years. Furthermore, certification has a whole lot to do with a lots of other factors other than flight stability. Avionics testing. Reliability testing. Stress testing.
Another clue to the flight testing is that there has been more prototypes built of the FC-1 faster and in any given time than the history of the other "Asian" fighter, which enables the plane to log more flight hours faster.
This is not to mention that certification involved far more factors other than flight stability testing, such as reliability testing, stress testing, avionics integration, specification changes. That's common sense to everyone reading this. It should be noted that the FC-1 did not set very high only reasonable goals on these, and is there is very little specification changes.
It is CAC and AVIC that continues to support the FC-1 and continues to do all all ther tests and validations. So it is CHINA that continues to support the plane, period. They know they have a winner that can make serious money on, and the government sees the diplomatic opportunities provided by the arms sales. Ironically its the PLAAF that may have a tendency to slow things down due to specification changes.
Relaxed stability is just another term used interchangeably with static instability. Again you're playing with words. Do you think that by playing with language you can change reality. And what the heck gradually introduced instability with "increasing" FBW. Note the final product---pitch axis only FBW with relaxed stability (aka negative static stability).
Standard accepted definition of Relaxed Stability.
That's practically sounds like static instability, does it not?
What you described happens in all planes. Instability always enters the system once the aircraft is in flight. That would be "dynamic" instability, and frankly FBW is also meant to reduce that.
What is "fully" instable means? "Fully instable" means that not even the FBW can handle it. So even with a plane that has FBW, it can only be instable to a certain degree, and that degree or static margins is rather small. A plane is either statically stable or not. Even if the plane can still be managed by manual controls (the Japanese F-2 as based on the F-16 can) it can be considered statically unstable.
LOL. How often you make feed back corrections has nothing to do with manual flyability. You can be doing trim corrections to optimize speed and cruising efficiency. If you are making small, very fast corrections, then the control surface deflections should be very small and minor.
And READ AGAIN MY LIPS. It is not CAUSE and EFFECT. Otherwise, based on historical examples, a tyrannical autocracy would be the precondition for a democracy.
The Su-27 by every other account is considered a statically unstable aircraft and it only has a pitch axis FBW.
No. It is to move the center of lift ahead of the CG. If the CL coincides with CG, it would be stable.
Basic encyclopedia reference and terminolory.
That would be dynamic and only does so in acceleration. Static instability means instable at rest (static = rest) as in no control input and stable speed.
You don't seem to get it do you? The LERX by increasing lift area moves the center of lift further forward, and considering they're bigger than the previous LERX, means it simultaneously increases the lifting forces while moving the CL forward. Then add the weight decrease of the DSI to that.
LOL. I did not say that the F-15 is unstable. I am saying it struck you that it has combined electronic and mechanical controls.
The first part of CAS is stability augmentation and the other (and larger part) is CAS itself.
The first part or stab aug system within the CAS assembly, is an autonomous system that counters oscillatory movements in a knee-jerk reaction, principally in the same way that a home appliance UPS handles fluctuating voltages. There is no intelligent or programmed decision-making involved at any stage of this process.
Read the text again. That is incorrect.
What's being done here is quite similar to what airliners use for their FBW which is a feedback and response system running according to control rules.
Based on your definition, analog FBW would not be "intelligent" at all either because that's not much different from analog FBW.
Hence, the JF-17 is definitely a stable airframe, besides having an autonomous CAS in the roll and yaw axes. Had it indeed been like that of the F-20, pac.org would surely have explicitly mentioned that it has partial FBW in those axes. Merely stab aug would most probably only imply a simple autonomous CAS control system.
LOL. Can you define what partial FBW means eh?
You're playing desperately with words. What does partial FBW means? It would have meant fractional control between manual and electronic controls. How is that much different from control and stability augmentation/intervention? There is no such things as "partial" FBW because that is a contradiction in meaning, hence you won't see any industry usage of that term.
.That is exactly what it seems, because had it been one integrated CAS within one FCS then it would surely have been termed as partial FBW in the roll and yaw axes, instead of being called as just "stability augmentation". Besides, there is no reason to halt at partial FBW in those axes, because it would have been more prudent 'go all the way' and convert it into a full FBW.
Except that the industry does not use the term "partial" FBW because suchv a term is self contradictory on its own meaning. The F-20 tried to use it because of "marketing", but it really is hybrid.
This, coupled with the astonishingly low time in which the FC-1 was declared complete and ready for serial production from the date of it's debut flight, has left no doubt that it is not a system that you are claiming or interpreting it to be.
Nonsense logic, to use certification times as "proof" that the plane cannot be unstable.
I've already destroyed that logic with real examples, such as how quickly the YF-16, YF-17, X-32, and X-35 are doing aerobatics right off from their earliest prototypes. And along with the F-CK-1 fighter which went from prototype to certification in only three years. Furthermore, certification has a whole lot to do with a lots of other factors other than flight stability. Avionics testing. Reliability testing. Stress testing.
Another clue to the flight testing is that there has been more prototypes built of the FC-1 faster and in any given time than the history of the other "Asian" fighter, which enables the plane to log more flight hours faster.
This is not to mention that certification involved far more factors other than flight stability testing, such as reliability testing, stress testing, avionics integration, specification changes. That's common sense to everyone reading this. It should be noted that the FC-1 did not set very high only reasonable goals on these, and is there is very little specification changes.
I think the PLAAF has ceased all support to the FC-1 and it is upto PAF to complete the remaining tests and validations, which is why even after 2 years since the production facility in Kamra was declared to begin production, prduction has not yet begun. Instead, PAF is still carrying out tests.
It is CAC and AVIC that continues to support the FC-1 and continues to do all all ther tests and validations. So it is CHINA that continues to support the plane, period. They know they have a winner that can make serious money on, and the government sees the diplomatic opportunities provided by the arms sales. Ironically its the PLAAF that may have a tendency to slow things down due to specification changes.
This says that Su-27 gradually introduced instability with increasing FBW, obviously only so long as the pilot managed to keep the aircraft under control at all times and conditions. If at all the JF-17 would have any instability it would only be slight that can be manageable by the pilot with whatever controls he has been provided.
Relaxed stability is just another term used interchangeably with static instability. Again you're playing with words. Do you think that by playing with language you can change reality. And what the heck gradually introduced instability with "increasing" FBW. Note the final product---pitch axis only FBW with relaxed stability (aka negative static stability).
Standard accepted definition of Relaxed Stability.
In aviation, relaxed stability is the tendency of an aircraft to change its attitude and angle of bank on its own accord. An aircraft with relaxed stability will oscillate in simple harmonic motion around a particular attitude at an increasing amplitude.
This can be contrasted with the tendency of an aircraft with positive stability, which, when trimmed to fly at a certain attitude, will continue to do so in the absence of control input, and will oscillate in simple harmonic motion on a decreasing scale around the trimmed attitude, eventually returning to its trimmed attitude. A positively stable aircraft will also resist any bank movement. A Cessna 152 is an example of a stable aircraft. Similarly, an aircraft with "neutral stability" will not return to its trimmed setting without control input, but will oscillate in simple harmonic motion around the trimmed setting continuously and be susceptible to bank influences.
That's practically sounds like static instability, does it not?
It can't be fully instable (instability is a quantitative measure and not a yes/no aspect) because the pilot won't be able to handle it.
What you described happens in all planes. Instability always enters the system once the aircraft is in flight. That would be "dynamic" instability, and frankly FBW is also meant to reduce that.
What is "fully" instable means? "Fully instable" means that not even the FBW can handle it. So even with a plane that has FBW, it can only be instable to a certain degree, and that degree or static margins is rather small. A plane is either statically stable or not. Even if the plane can still be managed by manual controls (the Japanese F-2 as based on the F-16 can) it can be considered statically unstable.
Note that the full-FBW in the other Asian combat jet sends out corrective signals every 10 or 12 milliseconds to keep the aircraft flying stably. This would be beyond the manual control of a pilot.
LOL. How often you make feed back corrections has nothing to do with manual flyability. You can be doing trim corrections to optimize speed and cruising efficiency. If you are making small, very fast corrections, then the control surface deflections should be very small and minor.
Please read page 177 of that e-book. It clearly states that instability was mooted only after FBW was introduced and that the PACT-4 aircraft were built only after full FBW was incorporated into the F-4. It is implied that full FBW was the prerequisite for PCAT-4, though it is not mentioned explicitly.
And READ AGAIN MY LIPS. It is not CAUSE and EFFECT. Otherwise, based on historical examples, a tyrannical autocracy would be the precondition for a democracy.
The Su-27 by every other account is considered a statically unstable aircraft and it only has a pitch axis FBW.
The objective of introducing instability is to coincide the CG with the Center of Lift.
No. It is to move the center of lift ahead of the CG. If the CL coincides with CG, it would be stable.
Basic encyclopedia reference and terminolory.
Relationship to aircraft and missile stability and control
* If the center of gravity (CG) of an aircraft is forward of the neutral point, or the CG of a missile is forward of the center of pressure, the vehicle will respond to a disturbance by producing an aerodynamic moment that returns the angle of attack of the vehicle towards the angle that existed prior to the disturbance.
* If the CG of an aircraft is behind the neutral point, or the CG of a missile is behind the center of pressure, the vehicle will respond to a disturbance by producing an aerodynamic moment that continues to drive the angle of attack of the vehicle further away from the starting position.
The first condition above is positive static stability. In missile analysis this is described as positive static margin. (In aircraft analysis it may be described as negative static margin.)
The second condition above is negative static stability. In missile analysis this is defined as negative static margin. (In aircraft analysis it may be described as positive static margin.)
It is only in the supersonic regimes that CG shifts backward which is a phenomenon observed in all aircraft.
That would be dynamic and only does so in acceleration. Static instability means instable at rest (static = rest) as in no control input and stable speed.
You said earlier that LERXs would increase instability, but their weight addition was more or less neutralized by the
weight reduction by DSI (to what extent, I can't tell).
You don't seem to get it do you? The LERX by increasing lift area moves the center of lift further forward, and considering they're bigger than the previous LERX, means it simultaneously increases the lifting forces while moving the CL forward. Then add the weight decrease of the DSI to that.