Aerodynamics thread

[MiG-29]

Re: J-20... The New Generation Fighter III

Wrong. For equilibrium to exists, all forces and moments must balance out to zero, meaning linear and angular acceleration are both zero. ".

hahahah pure fantasies hahaha longitudinal equilibrium does not mean tailplanes are ineffective, you just made that assertion from fantasy, longitudinal equilibrium means all forces are balanced and is a balanced trimmed condition.


Better buy Yefim Gordon Book`s Su-27 Flanker story" and read page 88, 89 and 90.

 

[Engineer]

Re: J-20... The New Generation Fighter III

hahahah pure fantasies hahaha longitudinal equilibrium does not mean tailplanes are ineffective, you just made that assertion from fantasy, longitudinal equilibrium means all forces are balanced and is a balanced trimmed condition.


Better buy Yefim Gordon Book`s Su-27 Flanker story" and read page 88, 89 and 90.

Just because you are living in a fantasy and think tailplane is effective at high AoA, that doesn't mean other people are living in the same state.

We already know for a fact that tailplane is ineffective at high AoA from Dr. Song's paper:

Control surfaces placed in front of the center of mass, like the canards, are negative load control surfaces. Since the main wing's ability to generate lift tends to saturate under high AOA conditions, the positive load control surfaces' pitch down control capabilities tend to saturate under high AOA as well. Therefore it will be wise to employ negative load control surfaces for pitch down control under high AOA conditions. Figure 7 compares the pitch down control capabilities of the canards and horizontal stabilizers. From the high AOA pitch down control stand point, it will be wise to use canards on the future fighter.

We also know that your own papers contradicted you,

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, which explicitly states tailplane losses effectiveness at high AoA:

It can be explained by loosing of effectiveness of control surfaces... In the range of AoA up to 35[SUP]o[/SUP] the normal increases approximately linearly, then stabilises and practically the tail surface losses its effectiveness.

For equilibrium,

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which analyzed on Cobra maneuver has this to say:

Analysis of maneuvers was preceded by solving the equation of longitudinal equilibrium. These equations can be obtained from dynamic equation of motion assuming that all accelerations and angular velocities are equal to zero.

No acceleration means all forces and moments are balanced. To achieve this balanced state, the analysis solved for trim conditions where tailplane deflection doesn't slow down or speed up the pitch rate in anyway. Thus, the tailplane deflection shown in the paper does not produce moment for recovery, debunking your claim.

The paper explicits mentioned that there is only one method for recovery:

The recovery from high angles of attack to the classical flight mode in a few seconds only is possible due to moving the center of pressure on main wing the center of pressure on main wing back and creating the strong nose-down aerodynamic pitching moment about the center of gravity.

The use of the word "only" means other methods such as active deflection of the tailplane cannot contribute to recovery.

 

[Air Force Brat]

Re: J-20... The New Generation Fighter III

Just because you are living in a fantasy and think tailplane is effective at high AoA, that doesn't mean other people are living in the same state.

We already know for a fact that tailplane is ineffective at high AoA from Dr. Song's paper:


We also know that your own papers contradicted you,

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, which explicitly states tailplane losses effectiveness at high AoA:


For equilibrium,

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which analyzed on Cobra maneuver has this to say:


No acceleration means all forces and moments are balanced. To achieve this balanced state, the analysis solved for trim conditions where tailplane deflection doesn't slow down or speed up the pitch rate in anyway. Thus, the tailplane deflection shown in the paper does not produce moment for recovery, debunking your claim.

The paper explicits mentioned that there is only one method for recovery:


The use of the word "only" means other methods such as active deflection of the tailplane cannot contribute to recovery.

Thats correct, and no airplane in the midst of the cobra manuever is by any stretch of the imagination in trim, you cannot trim an aircraft of any type in post stall aerodynamically. Post stall means after the stall, if you slowly bring the aircraft to maximum aoa, and the aircraft stalls or breaks, the nose will begin to fall through, unless you have TVC nozzles, the tailplane will not force the nose higher. The cobra is able to be performed in non TVC aircraft by accellerating through the stall region because of a positive-rapid application of full aft stick and the momentum is sufficient to carry the aircraft nose up through the vertical and beyond. Now the tailplane is deflected full downward and as the center of lift moves aft the aircraft is depitched and the nose rotates back through the vertical, this depitching generates lift and as soon as the tailplane begins to bite the pilot eases off of the forward stick to approx nuetral, in order to prevent the nose from falling through through the horizontal plane to the negative vertical. The forward leading edge strakes prevent assymetrical vortex bursting and maintains a symetrical airflow over the nose and fuselage of the aircraft, other wise you would have transonic roll off. This manuever has limited if any tactical application, in spite of propoganda to the contrary, such as Russia's new Su35 defeats Raptor every day as long as pilot strokes his lucky rabbits foot three times in the morning.

 

[MiG-29]

Re: J-20... The New Generation Fighter III

Thats correct, and no airplane in the midst of the cobra manuever is by any stretch of the imagination in trim, you cannot trim an aircraft of any type in post stall aerodynamically.. This manuever has limited if any tactical application, in spite of propoganda to the contrary, such as Russia's new Su35 defeats Raptor every day as long as pilot strokes his lucky rabbits foot three times in the morning.

The position of the tailplane is not arbitrary, and i know now why you say it is propaganda, The Su-27 tailplane is not in arbitrary position at any moment in fact it is deflected in this sequence, -5 deg, -12, -2, -5, and last -2 in the model.

If the position is arbitrary as you claim then any thing will do, but it does not, and i see you think that Su-27`s stall is a Cobra , stall is in Su-27`s case is uncontrolled flat spin, that is the real stall, Cobra is not a uncontrolled flat spin

---------- Post added at 11:51 PM ---------- Previous post was at 11:44 PM ----------

Just because you are living in a fantasy and think tailplane is effective at high AoA, that doesn't mean other people are living in the same state.

We already know for a fact that tailplane is ineffective at high AoA from Dr. Song's paper:


We also know that your own papers contradicted you,

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, which explicitly states tailplane losses effectiveness at high AoA:


For equilibrium,

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which analyzed on Cobra maneuver has this to say:


No acceleration means all forces and moments are balanced. To achieve this balanced state, the analysis solved for trim conditions where tailplane deflection doesn't slow down or speed up the pitch rate in anyway. Thus, the tailplane deflection shown in the paper does not produce moment for recovery, debunking your claim.

The paper explicits mentioned that there is only one method for recovery:


The use of the word "only" means other methods such as active deflection of the tailplane cannot contribute to recovery.

hahah innefective hahaha the article says the MiG-29 still deflects it and you concept of longitudinal equilibrium was one of your tricks to claim the tailplane is ineffective hahahaha

But see free stick stability means equilibrium or a state in which the tailplane pitch moment is in equilibrium with the aircraft pitch moment and Cobra is dynamic, In Russian is called dynamic break, an not moment is static and is not like the tail slide when the jet achieves 0 speed no it is not like that in fact the jet gains altitude and loses around 150km/h of speed, the jet is breaking hahahaha but of course you just read the article and tried to bring a mathematical concept into one of the worst example to justify your thesis

but the book says aeroplane in longitudinal equilibrium is trimmed by adjusting the tailplane hahahaha

 

[Engineer]

Re: J-20... The New Generation Fighter III

The position of the tailplane is not arbitrary, and i know now why you say it is propaganda, The Su-27 tailplane is not in arbitrary position at any moment in fact it is deflected in this sequence, -5 deg, -12, -2, -5, and last -2 in the model.

If the position is arbitrary as you claim then any thing will do, but it does not, and i see you think that Su-27`s stall is a Cobra , stall is in Su-27`s case is uncontrolled flat spin, that is the real stall, Cobra is not a uncontrolled flat spin

This is complete rubbish and shows your desperate attempt to redefine the meaning of "stall". First, let us see the definition of stall from an authoritative source. Taken from the

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:

The classical stall may be defined as a condition in which the airplane wing is subjected to an angle of attack greater than the angle for maximum lift coefficient.

Further down, the manual says the following:

An aerodynamic stall is defined as a condition in which the wing attains an angle of attack greater than the angle of attack for maximum lift, resulting in a loss of lift and an increase in drag.

Thus, stall merely requires that lift decreases as angle-of-attack increases, with no requirement that there is uncontrolled flat spin. While spin is a type of stall, it is not the only type of stall that can happen. The definition for stall is synonymous with the definition of post-stall that occurs in a Cobra maneuver. From this

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:

In the post stall regime, lift no longer increases but decreases with the angle of attack.

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is even more explicit in the definition, pointing out the aircraft has already stalled in post-stall region:

The post-stall region has been a source of considerable interest and research in the aviation community over the past two decades. It is characterized by separated and reverse flow over the wing, loss of lift, and a steep increase in drag. As can be seen in Figure 3, stall occurs at C[sub]L[sub]max[/sub][/sub]. The AOA range past that point is the post-stall region.

Laws of aerodynamics work the same everywhere. Su-27 won't escape stall just because it is a Russian aircraft.

---------- Post added at 09:54 AM ---------- Previous post was at 09:28 AM ----------

hahah innefective hahaha the article says the MiG-29 still deflects it and you concept of longitudinal equilibrium was one of your tricks to claim the tailplane is ineffective hahahaha

Tailplane being ineffective at high AoA is a fact that is asserted by multiple sources, not a claim.

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for example, which specifically analyzed MiG-29 dynamic in post-stall maneuver, explicitly states tailplane losses effectiveness at high AoA:

It can be explained by loosing of effectiveness of control surfaces... In the range of AoA up to 35[SUP]o[/SUP] the normal increases approximately linearly, then stabilises and practically the tail surface losses its effectiveness.

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says the following regarding the effectiveness of tailplane at high AoA:

A concentration of characteristic curves Cm for the tailplane setting angle φ[sub]t[/sub] being varied at post-critical AoA (i.e. very low sensitivity of pitch moment with respect to the tailplane setting angle) reflects the loss of effectiveness of a horizontal tail at higher AoA.

Whether the tailplane is deflected is irrelevant to its effectiveness at high AoA, just like flapping your arms wildly doesn't enable you to fly. So you see, whereas you need to use tricks to claim the tailplane is effective, I do not need to do such thing because I am simply stating facts from your own papers to debunk your claims.

But see free stick stability means equilibrium or a state in which the tailplane pitch moment is in equilibrium with the aircraft pitch moment and Cobra is dynamic, In Russian is called dynamic break, an not moment is static and is not like the tail slide when the jet achieves 0 speed no it is not like that in fact the jet gains altitude and loses around 150km/h of speed, the jet is breaking hahahaha but of course you just read the article and tried to bring a mathematical concept into one of the worst example to justify your thesis

but the book says aeroplane in longitudinal equilibrium is trimmed by adjusting the tailplane hahahaha

You are using a fallacy called

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, where you are lumping a bunch of technical terms together in a desperate attempt to sound knowledgeable. But as you have found out already, these sort of tricks don't work on me. Let see what

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has to say about equilibrium:

Analysis of maneuvers was preceded by solving the equation of longitudinal equilibrium. These equations can be obtained from dynamic equation of motion assuming that all accelerations and angular velocities are equal to zero.

No acceleration means there is no force and no moment, hence the tailplane is not slowing down or speeding up the pitch rate in anyway.

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continue on saying:

Knowing that the supermanoeuvre aircraft has to be stable at the range of high angles of attack and unstable at the range of small angles of attack one can expect that at each, prescribed speed and for assumed canard setting the aircraft has two distinct, steady flight conditions (i.e. states of trim).

Thus, the use of the word "trim" refers to steady-state flight conditions or states of equilibrium, and in an equilibrium the tailplane does not change the pitch rate. In short, the tailplane has no role in arresting the angle-of-attack to bring the aircraft back into regular flight condition. This also exposes your pathetic word-game at trying to distort statements of the authors to claim tailplane is effective.

In another part of

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, the mechanism for recovery is given:

The recovery from high angles of attack to the classical flight mode in a few seconds only is possible due to moving the center of pressure on main wing the center of pressure on main wing back and creating the strong nose-down aerodynamic pitching moment about the center of gravity.

The use of the word "only" means active deflection of tailplane has no contribution to recovery.

 

[Air Force Brat]

Re: J-20... The New Generation Fighter III

The position of the tailplane is not arbitrary, and i know now why you say it is propaganda, The Su-27 tailplane is not in arbitrary position at any moment in fact it is deflected in this sequence, -5 deg, -12, -2, -5, and last -2 in the model.

If the position is arbitrary as you claim then any thing will do, but it does not, and i see you think that Su-27`s stall is a Cobra , stall is in Su-27`s case is uncontrolled flat spin, that is the real stall, Cobra is not a uncontrolled flat spin

MIG 29, BRO, I AM a PILOT as in FAA certificate #--- -- ----, I am beginning to think you are a slow student, you would wash out of flight school with that explanation on your FAA exam. An Su27 stalls for the same reason as a Cessna 150, when the wings angle of attack exceeds the maximum angle of attack for lift production and flow is disturbed or separates from the top of the wing, and the wing produces less lift than the aircraft weight, if you persist in applying back pressure the stall will break, or depart from controlled flight as the aircraft depitches itself, in spite of the fact that you may be holding full aft stick. The aircraft may tend to break right or left and arresting that roll off with opposite rudder prevents the aircraft from spinning. A spin occurs after the aircraft is departed because of wing roll off or loss of yaw control.
Quick, go to the nearest airport offering flight instruction and take a couple of hours of dual, explain to your instructor that you would like to do airwork, specifically slow flight and stalls. Power off are easy, power on stalls result in a higher deck angle, with a more pronounced break.

 

[MiG-29]

Re: J-20... The New Generation Fighter III

MIG 29, BRO, I AM a PILOT as in FAA certificate #--- -- ----, I am beginning to think you are a slow student, you would wash out of flight school with that explanation on your FAA exam. An Su27 stalls for the same reason as a Cessna 150, when the wings angle of attack exceeds the maximum angle of attack for lift production and flow is disturbed or separates from the top of the wing, and the wing produces less lift than the aircraft weight, if you persist in applying back pressure the stall will break, or depart from controlled flight as the aircraft depitches itself, in spite of the fact that you may be holding full aft stick. The aircraft may tend to break right or left and arresting that roll off with opposite rudder prevents the aircraft from spinning. A spin occurs after the aircraft is departed because of wing roll off or loss of yaw control.
Quick, go to the nearest airport offering flight instruction and take a couple of hours of dual, explain to your instructor that you would like to do airwork, specifically slow flight and stalls. Power off are easy, power on stalls result in a higher deck angle, with a more pronounced break.

No offence, but do you fly a Su-27? the stall characteristics of each aircraft are different, to start a Cessna does not execute the Cobra, not even the F-18E which is the closest jet to a Su-27 besides MiG-29.

A straight wing won`t have the same stall characteristics of a delta wing.

Here we are talking of the only jet fighter that has demostrated the Cobra without TVC nozzles besides the MiG-29.

You have not understood what is a stall on the Su-27, the Su-27 stalls easily at 60 degrees of AoA if the conditions are static, what i mean by static is if you try to fly it for let us say 50 seconds on a 60 degrees of AoA.
In fact the limit set for the Su-27 is only 30 degrees, i mean that is the operational limit, the tailplane is limited in its deflection.

The Cobra was first executed not even by Victor Pugachev but by Igor Volk in 1987, so do not tell me the aerodynamics of a Cessna or even a F-16 compare to the Su-27.

The Su-27 now is not unique, F-22 can do the Cobra, but i have never seen any other jet doing the Cobra on pure aerodynamic controls.

Eugeny Frolov developed the Cobra even further wen he execute the Frolov`s Chakra but this was on the Su-37 which has TVC nozzles.

If you try to force a Su-27 to fly at 60 degrees of AoA for 50 seconds you will stall it, it will flat spin, it will fall into a flat spin.

That is the real stall of the jet, however stall as the article mentions is not an inmediate loss of lift, in fact it might have another peak and hysteresis is delaying the stall, so if you do a brief incursion at 110 degree AoA you won`t fall into flat spin.

Will the Su-27 stall at 110 degrees of AoA yes it will if you want to force to fly beyond 5-7 seconds of what Cobra lasts, but if you do it for 3-5 seconds it won`t.

Cobra is not a break of aerodynamic rules, it is just a manoeuvre where the delay caused by hysteresis of vortex burst offers to the Su-27 pilot the window to bring back the jet to horizontal flight.

Now i will tell you what features allow the Su-27 to do the Cobra.

First the LEX generate vortices and add lateral stability at high AoA, an another fact is its flattened
fuselage also adds extra lateral stability, because they straight up the vortices at high AoA.

Does the Su-27 experiment some instability? yes, it does, but is not enough to stall it.

it keeps some lift and if you do not believe me see who wrote this



POSTGRADUATE
NAVAL SCHOOL
MONTEREY, CALIFORNIA
THESIS
Approved for public release; distribution is unlimited.
TIME-OPTIMIZATION OF HIGH PERFORMANCE
COMBAT MANEUVERS
by
Benjamin R. Carter
June 2005

TIME-OPTIMIZATION OF HIGH PERFORMANCE COMBAT MANEUVERS
Benjamin R. Carter
Lieutenant Junior Grade, United States Navy
B.S., United States Naval Academy, 2002
Submitted in partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING


and he says what?


What the previous two observations mean is that an aircraft can still be flyable in
the post-stall region provided that several criteria are met:
1. The aircraft has enough thrust to overcome the huge drag increase.
2. The aircraft has controls that will not be rendered ineffective by separated
flow over the wings and tail.
3. CL remains great enough in post-stall to overcome the aircraft’s weight.

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So honestly do you think this guy will be wash out of a test come on!

 

[Engineer]

Re: J-20... The New Generation Fighter III

No offence, but do you fly a Su-27? the stall characteristics of each aircraft are different, to start a Cessna does not execute the Cobra, not even the F-18E which is the closest jet to a Su-27 besides MiG-29.

A straight wing won`t have the same stall characteristics of a delta wing.

Stall characteristics of each aircraft being different does not mean the definition of stall is different for each aircraft. Furthermore, if your argument is that Air Force Brat does not fly a Su-27 hence does not have authority to talk about the aircraft, the same argument would equally be applicable to you.

Here we are talking of the only jet fighter that has demostrated the Cobra without TVC nozzles besides the MiG-29.

You have not understood what is a stall on the Su-27, the Su-27 stalls easily at 60 degrees of AoA if the conditions are static, what i mean by static is if you try to fly it for let us say 50 seconds on a 60 degrees of AoA.
In fact the limit set for the Su-27 is only 30 degrees, i mean that is the operational limit, the tailplane is limited in its deflection.

The Cobra was first executed not even by Victor Pugachev but by Igor Volk in 1987, so do not tell me the aerodynamics of a Cessna or even a F-16 compare to the Su-27.

The Su-27 now is not unique, F-22 can do the Cobra, but i have never seen any other jet doing the Cobra on pure aerodynamic controls.

Eugeny Frolov developed the Cobra even further wen he execute the Frolov`s Chakra but this was on the Su-37 which has TVC nozzles.

If you try to force a Su-27 to fly at 60 degrees of AoA for 50 seconds you will stall it, it will flat spin, it will fall into a flat spin.

That is the real stall of the jet, however stall as the article mentions is not an inmediate loss of lift, in fact it might have another peak and hysteresis is delaying the stall, so if you do a brief incursion at 110 degree AoA you won`t fall into flat spin.

Will the Su-27 stall at 110 degrees of AoA yes it will if you want to force to fly beyond 5-7 seconds of what Cobra lasts, but if you do it for 3-5 seconds it won`t.

Cobra is not a break of aerodynamic rules, it is just a manoeuvre where the delay caused by hysteresis of vortex burst offers to the Su-27 pilot the window to bring back the jet to horizontal flight.

Now i will tell you what features allow the Su-27 to do the Cobra.

First the LEX generate vortices and add lateral stability at high AoA, an another fact is its flattened
fuselage also adds extra lateral stability, because they straight up the vortices at high AoA.

Does the Su-27 experiment some instability? yes, it does, but is not enough to stall it.

Wrong. In the post-stall region, the aircraft has already stalled. This is taken from

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, one of the sources that you have quoted:

The post-stall region has been a source of considerable interest and research in the aviation community over the past two decades. It is characterized by separated and reverse flow over the wing, loss of lift, and a steep increase in drag. As can be seen in Figure 3, stall occurs at C[sub]L[sub]max[/sub][/sub]. The AOA range past that point is the post-stall region.

The Figure 3 mentioned above is attached here for your convenience:

As you can see, stall occurs at the same location where maximum lift occurs, with evidences of flow separation. When AoA of the aircraft goes beyond that point, the aircraft is in a post-stall region. Thus, by being in a post-stall maneuver called the Cobra, the aircraft has already stalled, and aerodynamic surfaces for control become ineffective.

it keeps some lift and if you do not believe me see who wrote this


POSTGRADUATE
NAVAL SCHOOL
MONTEREY, CALIFORNIA
THESIS
Approved for public release; distribution is unlimited.
TIME-OPTIMIZATION OF HIGH PERFORMANCE
COMBAT MANEUVERS
by
Benjamin R. Carter
June 2005

TIME-OPTIMIZATION OF HIGH PERFORMANCE COMBAT MANEUVERS
Benjamin R. Carter
Lieutenant Junior Grade, United States Navy
B.S., United States Naval Academy, 2002
Submitted in partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING


and he says what?


What the previous two observations mean is that an aircraft can still be flyable in
the post-stall region provided that several criteria are met:
1. The aircraft has enough thrust to overcome the huge drag increase.
2. The aircraft has controls that will not be rendered ineffective by separated
flow over the wings and tail.
3. CL remains great enough in post-stall to overcome the aircraft’s weight.

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So honestly do you think this guy will be wash out of a test come on!

I have taken the liberty to simply take a screenshot of that page, and highlighted the important part for you. The bullet points quoted by your are near the bottom of the screenshot:

The highlighted portion says:

As can be seen in Figure 3, stall occurs at C[sub]L[sub]max[/sub][/sub]. The AOA range past that point is the post-stall region.

From Figure 3, we can see that stall occurs at exactly the same place where maximum lift occurs, debunking your silly definition of stall that requires lift to disappear completely. It is amusing to see you so desperately trying to redefine the meaning of "stall" by

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, and conveniently ignore the very definition for "stall" given on the same page as you obtained your quotes from.

Another definition for post-stall comes from

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:

In the post stall regime, lift no longer increases but decreases with the angle of attack.

This is the same definition as stall where lift decreases as angle-of-attack increases. From an authoritative source on the definition of stall:

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:

The classical stall may be defined as a condition in which the airplane wing is subjected to an angle of attack greater than the angle for maximum lift coefficient.

Thus, an aircraft that is in a Cobra maneuver is in a stall, because Cobra maneuver is a post-stall maneuver. An alternative definition is given in the same manual:

Stalls. The stall may be defined by either airflow separation with increasing angle of attack causing loss of lift, control difficulty, or excessive buffet/vibration (see 6.2.2 and 6.2.5)

Again, there is no requirement that lift has to disappear completely for stall to happen. The above quote also mentions control difficulty, and the reason is explained in

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:

if the aircraft can fly at angles of attack of 80[sup]o[/sup] - 120[sup]o[/sup] with the ability to maintain stability in all channels. In this flight regime the ability for conventional control is usually lost.

Thus, the tailplane being a conventional aerodynamic surfaces becomes ineffective, as pointed out by

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:

A concentration of characteristic curves Cm for the tailplane setting angle φ[sub]t[/sub] being varied at post-critical AoA (i.e. very low sensitivity of pitch moment with respect to the tailplane setting angle) reflects the loss of effectiveness of a horizontal tail at higher AoA.

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, says the following statement statement with regards to tailplane effectiveness:

It can be explained by loosing of effectiveness of control surfaces... In the range of AoA up to 35[SUP]o[/SUP] the normal increases approximately linearly, then stabilises and practically the tail surface losses its effectiveness.

Therefore, the tailplane is inefficient in generating nose-down moment for recovery.

 

[Air Force Brat]

Re: J-20... The New Generation Fighter III

No offence, but do you fly a Su-27? the stall characteristics of each aircraft are different, to start a Cessna does not execute the Cobra, not even the F-18E which is the closest jet to a Su-27 besides MiG-29.

A straight wing won`t have the same stall characteristics of a delta wing.

Here we are talking of the only jet fighter that has demostrated the Cobra without TVC nozzles besides the MiG-29.

You have not understood what is a stall on the Su-27, the Su-27 stalls easily at 60 degrees of AoA if the conditions are static, what i mean by static is if you try to fly it for let us say 50 seconds on a 60 degrees of AoA.
In fact the limit set for the Su-27 is only 30 degrees, i mean that is the operational limit, the tailplane is limited in its deflection.

The Cobra was first executed not even by Victor Pugachev but by Igor Volk in 1987, so do not tell me the aerodynamics of a Cessna or even a F-16 compare to the Su-27.

The Su-27 now is not unique, F-22 can do the Cobra, but i have never seen any other jet doing the Cobra on pure aerodynamic controls.

Eugeny Frolov developed the Cobra even further wen he execute the Frolov`s Chakra but this was on the Su-37 which has TVC nozzles.

If you try to force a Su-27 to fly at 60 degrees of AoA for 50 seconds you will stall it, it will flat spin, it will fall into a flat spin.

That is the real stall of the jet, however stall as the article mentions is not an inmediate loss of lift, in fact it might have another peak and hysteresis is delaying the stall, so if you do a brief incursion at 110 degree AoA you won`t fall into flat spin.

Will the Su-27 stall at 110 degrees of AoA yes it will if you want to force to fly beyond 5-7 seconds of what Cobra lasts, but if you do it for 3-5 seconds it won`t.

Cobra is not a break of aerodynamic rules, it is just a manoeuvre where the delay caused by hysteresis of vortex burst offers to the Su-27 pilot the window to bring back the jet to horizontal flight.

Now i will tell you what features allow the Su-27 to do the Cobra.

First the LEX generate vortices and add lateral stability at high AoA, an another fact is its flattened
fuselage also adds extra lateral stability, because they straight up the vortices at high AoA.

Does the Su-27 experiment some instability? yes, it does, but is not enough to stall it.

it keeps some lift and if you do not believe me see who wrote this



POSTGRADUATE
NAVAL SCHOOL
MONTEREY, CALIFORNIA
THESIS
Approved for public release; distribution is unlimited.
TIME-OPTIMIZATION OF HIGH PERFORMANCE
COMBAT MANEUVERS
by
Benjamin R. Carter
June 2005

TIME-OPTIMIZATION OF HIGH PERFORMANCE COMBAT MANEUVERS
Benjamin R. Carter
Lieutenant Junior Grade, United States Navy
B.S., United States Naval Academy, 2002
Submitted in partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING


and he says what?


What the previous two observations mean is that an aircraft can still be flyable in
the post-stall region provided that several criteria are met:
1. The aircraft has enough thrust to overcome the huge drag increase.
2. The aircraft has controls that will not be rendered ineffective by separated
flow over the wings and tail.
3. CL remains great enough in post-stall to overcome the aircraft’s weight.

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So honestly do you think this guy will be wash out of a test come on!

No, but he wouldn't buy your definition of a stall either, a stall is separation of airflow, watch some ytube vids of tufted wings, nobody on here loves the raptor or the flanker more than I, but, straight wing, swept wing, hi wing, lo wing, the wing is the thing, dude, love you bro, but this is aero 101, and no offense really I do like you a lot but calling your forum brothers liars is uncool. So lets not, every one on this forum is putting forth an honest opinion, even you, the engineer is very patient with you, but a couple of flying lessons would help you understand that aerodynamics are not a bunch of divergent theories in divergent papers, you have a lot of head knowledge and some really good points. But no aircraft can be trimmed while it is stalled,,,,controlled with TVC nozzles, maybe, trim is a steady state, if you deflect the controls to manuever and take your hand off the controls, it will return to its trimmed state.

And what version of the Su27 do you fly little bro?

 

[MiG-29]

Re: J-20... The New Generation Fighter III

No, but he wouldn't buy your definition of a stall either, a stall is separation of airflow, watch some ytube vids of tufted wings, nobody on here loves the raptor or the flanker more than I, but, straight wing, swept wing, hi wing, lo wing, the wing is the thing, dude, love you bro, but this is aero 101, and no offense really I do like you a lot but calling your forum brothers liars is uncool. So lets not, every one on this forum is putting forth an honest opinion, even you, the engineer is very patient with you, but a couple of flying lessons would help you understand that aerodynamics are not a bunch of divergent theories in divergent papers, you have a lot of head knowledge and some really good points. But no aircraft can be trimmed while it is stalled,,,,controlled with TVC nozzles, maybe, trim is a steady state, if you deflect the controls to manuever and take your hand off the controls, it will return to its trimmed state.

And what version of the Su27 do you fly little bro?

Well that is up to you.
He does say what he says and his paper says the same that the Russians are saying, so sorry, i do not believe your theory, niether Engineer`s.

I can use a computer but i does not mean i know how many things of my computer work.
You are claiming because you fly an aircraft you know more than a master in aerodynamics, who happens to be a US naval school member.

So i ask you why i have to believe you?

Sorry but i believe him, and the reason is his paper agrees with several other papers i have read about the Cobra plus he was a United States Naval Academy member and a MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING, so now i ask you, have you written a paper of post-stall aerodynamics as he has?
Do you have a paper that has been presented before the academia and the US Naval academy?
Sorry Brat, your explanation of stall goes well for a Cessna but not for a Su-27.

In Yefim Gondon`s book "Su-27 Flanker Story" in pages 89 to 93 they have a very good explanation of why Cobra happens and they mention Hysteresis, Inertia and what the pilot does to execute it.

Now His book was made in Russia, with direct Sukhoi input, why i have to believe you?
And by the way i have family who made parts for aircraft in Mexico and family in Russia who flew Soviet aircraft.

Do you think they have a master to explain me the Cobra? no they have not in fact they can explain me something but not all.
Why because a real mathematical model of Cobra is too complex, and the guys who have made them like this guy

You say he is wrong that Su-27 is stalled when he says based upon mathematical models post stall aircraft need to maintain some lift and control devices still working.

Sorry but against that evidence i prefer TIME-OPTIMIZATION OF HIGH PERFORMANCE COMBAT MANEUVERS by
Benjamin R. Carter rather than your explanation.