Su-57 Stealth Fighter: News #6

LMFS wrote:
Maybe you have seen I am discussing with GarryB precisely about TVC and trimming.

Yes, when I finished with my post I have seen that you two are having an interesting debate, and in my humble opinion both of you have some good and some bad, or should I say somewhat wrong assumptions/conclusions.

I will try to be short this time, but maybe later, if I find more time I can join more detailed discussion.

LMFS wrote:So, as the CoL moves backwards, it may eventually get behind the CoG and actually give the plane the longitudinal stability it does not have in subsonic regime. At this point, my understanding is that you need lift in front of the CoG as you explained above for the LEVCON's.

You can create that lift in a few ways in order to pitch the nose up.
One way is by using the LEVCONS as explained above, the other way is by using the horizontal tail where we apply the downforce on the back of the plane to increase AoA which consequently increases the overall lift needed to pitch the nose up, but at a cost of creating more drag and less overall lift compared to the LEVCON's [by deflecting the tails down we don't create the lift, unlike the LEVCON's].
The third way for example is by using the TVC.

LMFS wrote:I understand that in such situation where trim requires pitching up the nose, TVC, being after CoG, will need to deflect upwards and push the tail down to correct the AoA. Minus de added drag that deflecting tails would imply, this use of TVC would be equally detrimental to the plane's overall lift, do you agree? From your statement above it seems TVC could be actually used for supersonic trim purposes. The plane being unstable I would agree, but having turned stable by the higher flight speed I can't see how it would help. That 14% improvement would be compatible with the reduction in overall lift that negative deflection of the tails would mean, I don't see why creating the same effect with the TVC would not result in the same overall reduction in lift and hence STR

By using the TVC for supersonic trimming purposes we get better lift to drag ratio compared to classic aerodynamic surfaces. The principle of action is the same when we talk about TVC and horizontal tails [or elevon in delta wing etc.], but the difference in drag is significant. Protruding elevators create much higher amount of drag at supersonic speed compared to just a few degrees that are needed for the TVC to trim the plane, and that is the main difference.
In other words, for the same AoA you create less drag and more lift with the TVC because you are not reducing the overall lift by greater downward deflection of the control surface [you do not need that negative deflection of the control surface when you have TVC], and you do not create additional drag by the higher protruding surface.
Since the amount of the lift is the crucial thing for the pitch up of the nose, your plane with the TVC will generally need less AoA to create the same amount of the lift compared to the plane with the classic aerodynamic surfaces that needs higher AoA [which will aditionaly worsen the drag] because that plane will inherently have worse lift to drag ratio.

PeregrineFalcon wrote:I will try to be short this time, but maybe later, if I find more time I can join more detailed discussion.

No problem, if anytime you have the opportunity to explain further, it will be welcome.

You can create that lift in a few ways in order to pitch the nose up.
One way is by using the LEVCONS as explained above, the other way is by using the horizontal tail where we apply the downforce on the back of the plane to increase AoA which consequently increases the overall lift needed to pitch the nose up, but at a cost of creating more drag and less overall lift compared to the LEVCON's [by deflecting the tails down we don't create the lift, unlike the LEVCON's].
The third way for example is by using the TVC.

Yes, no questions here.

By using the TVC for supersonic trimming purposes we get better lift to drag ratio compared to classic aerodynamic surfaces. The principle of action is the same when we talk about TVC and horizontal tails [or elevon in delta wing etc.], but the difference in drag is significant. Protruding elevators create much higher amount of drag at supersonic speed compared to just a few degrees that are needed for the TVC to trim the plane, and that is the main difference.

Agree here too..

In other words, for the same AoA you create less drag and more lift with the TVC because you are not reducing the overall lift by greater downward deflection of the control surface [you do not need that negative deflection of the control surface when you have TVC], and you do not create additional drag by the higher protruding surface.

Since the amount of the lift is the crucial thing for the pitch up of the nose, your plane with the TVC will generally need less AoA to create the same amount of the lift compared to the plane with the classic aerodynamic surfaces that needs higher AoA [which will aditionaly worsen the drag] because that plane will inherently have worse lift to drag ratio.

Wait a second, I will make an example to see where I am getting lost, if you don't mind. Let us say at a given moment of the supersonic flight you need say 20 "points" of net downforce on the tail to trim the plane. Let us assume the horizontal tails in neutral position at that AoA would create 30 points of lift. So if you use them for the trimming, you deflect them negatively and change 30 points of lift for 20 of downforce (I am ignoring effects of the extra drag here). Now with the TVC, you would need to create 50 points of downforce to negate those 30 points of lift behind the CoG plus the amount needed for the trimming? Wouldn't it be better to adjust the horizontal tail for zero lift at that AoA and produce just 20 points downforce with the TVC? That means, no matter what way you are generating that downforce, you end up losing the same amount of lift and the only difference is that TVC is not creating big additional drag. Because all the lift you generate after the CoG is just further pushing the nose down in the end...

The tails or TVC push the tail down to compensate the nose's downwards moment, rotating it upwards around the CoG.

That is correct, but the tail or engine nozzles weren't developing any lift to begin with... it is just generating a force to maintain aircraft body trim...

The result is an effective reduction of overall available lift as explained.

A couple of problems with this... aircraft lift is not a zero sum game... the consequences of not using tail or engine nozzles to raise the nose will generate a negative angle of attack which will have a much more dramatic effect on lift than any trimming effect they do have to rotate the aircraft on its new cg.

The lift that keeps an aircraft in the air comes from the wing and the fuselage for those aircraft with lifting bodies. The forces applied by control surfaces and moving engine nozzles create very specific forces to turn the aircraft in various ways including roll, yaw, and pitch, and in that sense they often generate a little extra drag, but they are airflow deflectors... not lift generating devices as such.

If your aircraft can only maintain flight with the help of canards lifting at the front you have a shit aircraft design.

Maybe I am missing something, I don't design planes for a living, but as far as I see it is pretty simple.

I don't design them either, but ripping the horizontal tail surfaces or canards off a plane does not lead to loss of lift and rapid descent... it more often leads to loss of control... because that is their primary function.

It is not clear to me what do you mean by "shift angle a few degrees": if you mean shifting "a few degrees" upwards, then it is the situation I am describing and there will be a vertical component of the force pointing downwards, I don't know how to get around that

It goes back to boats and trim. With the propeller horizontal the force it generates pushes the boat horizontally through the water, but water is a very high drag medium. With a very small boat with a big engine, what you can do is angle the propeller so the force does not just push the boat horizontally but it actually pushes down and lifts the boat out of the water. It does not make it fly, but it does make it skim or plane on the surface so there is a lot less drag and returning the prop to horizontal means the boat can go faster for a given amount of power because it does not have to push through as much water.

WTF am I on about... a jet aircraft does not skim water.

You don't design aircraft and neither do I but the shape of an aircraft is absolutely critical to move efficiently through the air. Changing the angle of attack will effect how that aircraft moves through the air... there will be a specific angle of attack for a given speed and altitude where the air flows over the wings and it generates the ideal amount of lift with the minimum level of drag... a 90 degree angle of attack to the flight airflow is essentially being an airbrake... no lift and all drag.

Lets say the ideal AOA for aircraft x flying at airspeed y at altitude z is 8 degrees... you might need a canard deflection of 15 degrees to maintain that, or a tail surface deflection of 15 degrees to do the same. The Canard would be lifting the nose and the tail surface pushing the tail down, but the effect is the same because the engine thrust is angled down 8 degrees and the wing angle of 8 degrees creates the ideal level of lift for that aircraft in that configuration etc etc etc.

As the aircraft approaches and then exceeds the speed of sound the balance of the aircraft changes... the cg moves which causes the nose to drop... if you do nothing you will have problems because you will start to lose altitude for a start... while you are flying through this trans sonic speed range the cg moves but as you keep accelerating it moves back, so the shift and also the countering of the effect is temporary anyway.

During this period of instability you might increase canard deflection to 20 degrees up, or the tail surface to 20 degrees down to maintain the 8 degree aircraft pitch up attitude.

What I am saying is that a 20 degree pitched up or 20 degree pitched down canard or tail surface increases drag and RCS when the aircraft is pitched up a 8 degrees that is an almost 30 degree pitch up angle for the canard, but only a 12 degree pitch down from horizontal for the tail surface, but the nozzles on a thrust vector jet engine have much more control authority than canards and tail surfaces so the ideal low drag angle of attack might not be 8 degrees with TVC... it might only be 4 degrees with the TVC nozzles pitched up 4 degrees in normal flight at that altitude and speed, but the shift in cg it might need a TVC nozzle shift of a further 4 degrees to 8 degrees upwards to counter cg shift until that speed gap is passed through and then it can return to a 4 degree angle up thrust line.

What I am saying is that the engine nozzle pitch angles will be much less to get the same effect but also not really noticeable from the front anyway in terms of IR and RCS factors... and they do their job at any speed including zero forward speed and even negative forward speed in a tail slide.

The canards and tail surfaces can be kept at low drag neutral positions...


It is like talking about super sized HUDs offering the best opportunity for the pilot to keep his eyes outside the plane and not staring at screens in the cockpit, when the obvious solution is really a helmet mounted sight...

Downforce is downforce, a force vector pointing down in the vertical axis, no matter what device created it.

A down force that turns an aerodynamic structure like an aircraft to a nose up attitude increases the lifting performance of the main wing and makes the aircraft climb and not descend... why do you describe it as a loss of lift?

The tails have added drag, the TVC not so much, but drag is not what I am talking about.

Drag and lift are directly related and pretty damn critical if you want efficient long range super cruise.

Having no tail and no canard benefits in terms of drag, but obviously creates risk in terms of loss of control if the TVC fails.

Yes, when I finished with my post I have seen that you two are having an interesting debate, and in my humble opinion both of you have some good and some bad, or should I say somewhat wrong assumptions/conclusions.

Don't hold back ... I have been wrong about plenty of things in the past and I am discussing this not to be right but to compare my view with others to find the truth...
(I am not an engineer so be gentle...)

GarryB wrote:That is correct, but the tail or engine nozzles weren't developing any lift to begin with... it is just generating a force to maintain aircraft body trim...

Tails and foreplanes are airfoils and can generate lift as wings do. In a plane with AoA 2deg. with tails at neutral position re. the fuselage, both wings and tails are generating lift. In fact the lift generated by the tails is crucial to calculate turning rates because on modern planes they do not need to be deflected negatively for the plane to turn (pitch up the nose with a banking angle) since they are unstable, and they add a sizeable amount of the total lift.

aircraft lift is not a zero sum game...

Not if it is produced at the CoG, if it is produced after or behind, it needs to be compensated or it will make the plane lose longitudinal control.

but they are airflow deflectors... not lift generating devices as such.

See above, they are airfoils and they create drag and lift by the same mechanisms the wings do.

If your aircraft can only maintain flight with the help of canards lifting at the front you have a shit aircraft design.

With traditional stable planes it is either canards or tail, and without them you simply crash.

Lets say the ideal AOA for aircraft x flying at airspeed y at altitude z is 8 degrees... you might need a canard deflection of 15 degrees to maintain that, or a tail surface deflection of 15 degrees to do the same. The Canard would be lifting the nose and the tail surface pushing the tail down, but the effect is the same because the engine thrust is angled down 8 degrees and the wing angle of 8 degrees creates the ideal level of lift for that aircraft in that configuration etc etc  etc.

Not really. If at a given point of the flight envelope with a certain AoA you have 100 points of lift produced by the wings and you use the canards to trim, which produce 20 points, you have 120 points of total lift available. If you instead use the tails to trim, creating 20 points of downforce, you have 80 points of total lift available. Obviously you will need either to reduce altitude or to increase AoA or to increase speed, but you will not be able to sustain level flight in the same conditions as the plane with canards. I recommend you to look for this on the many good sites about aerodynamics that you can find on the web, since I don't seem to be able to convince you.

but the nozzles on a thrust vector jet engine have much more control authority than canards and tail surfaces

It depends. Zero airspeed full AB at sea level is not the same as corner speed cruise throttle at high altitude. You would need to crunch some numbers there.

What I am saying is that the engine nozzle pitch angles will be much less to get the same effect but also not really noticeable from the front anyway in terms of IR and RCS factors... and they do their job at any speed including zero forward speed and even negative forward speed in a tail slide.

I am all for TVC, I am only saying on a plane that needs to pitch up the nose, it is better to generate lift in front of the CoG than downforce behind.

The canards and tail surfaces can be kept at low drag neutral positions...

Wings could also be kept low drag at neutral position, only the plane would not fly then... control surfaces contribute to the total lift generation. Of course deflections need to be much smaller than the values you were giving above, above 15 deg almost any airfoil is going to stall.

A down force that turns an aerodynamic structure like an aircraft to a nose up attitude increases the lifting performance of the main wing and makes the aircraft climb and not descend... why do you describe it as a loss of lift?

See above. Every loss of lift through the downforce needs to be compensated by higher AoA which creates more drag.

Having no tail and no canard benefits in terms of drag, but obviously creates risk in terms of loss of control if the TVC fails.

Without surface controls you cannot trim the plane and react to changes in CoG /CoL, there is no way around it. Even a flying wing needs surfaces to substitute tails.

LMFS wrote:Wait a second, I will make an example to see where I am getting lost, if you don't mind. Let us say at a given moment of the supersonic flight you need say 20 "points" of net downforce on the tail to trim the plane. Let us assume the horizontal tails in neutral position at that AoA would create 30 points of lift. So if you use them for the trimming, you deflect them negatively and change 30 points of lift for 20 of downforce (I am ignoring effects of the extra drag here). Now with the TVC, you would need to create 50 points of downforce to negate those 30 points of lift behind the CoG plus the amount needed for the trimming? Wouldn't it be better to adjust the horizontal tail for zero lift at that AoA and produce just 20 points downforce with the TVC? That means, no matter what way you are generating that downforce, you end up losing the same amount of lift and the only difference is that TVC is not creating big additional drag. Because all the lift you generate after the CoG is just further pushing the nose down in the end...

Real data actually shows that you can reduce drag and generate more lift by using the TVC for trimming purposes:

https://issuu.com/defencedog/docs/itp-tvc-eurofighter

A spin-off of using the TVN as a control surface is that thrust vectoring can be used to trim the aircraft and "unload" the flight- control surfaces, thereby reducing drag and/or increasing lift. The conventional control surfaces are meanwhile "liberated" from their role as trim devices and can be used to enhance manoeuvrability.

In supersonic flight, even small flap deflections can cause large amounts of drag.

"If you have thrust vectoring, you can put your aerodynamic surfaces in the best position to give optimum lift and drag, because you do not need to trim the aircraft with aerodynamic surfaces," says Osterhuber.

The use of the Nozzles as a complementary control surface allows the aircraft to better optimize its angle of attack in stationary level flight for a given flight point and load configuration, hence reducing the drag, which in turn leads to strong benefits in SFC, and therefore range.
Similarly to the above case, the nozzles can be used to increase the maximum load factor that is achievable under certain circumstances while maintaining the aircraft trimmed. This applies both for stationary manoeuvres (sustained turn rate) and for transient manoeuvres (rapid deceleration).

For example, at 30000 ft and Mach 1.8 there is an increase in lift coefficient by 14%, load factor by 9% and turn rate by 9%

PeregrineFalcon wrote:Real data actually shows that you can reduce drag and generate more lift by using the TVC for trimming purposes:

https://issuu.com/defencedog/docs/itp-tvc-eurofighter

A spin-off of using the TVN as a control surface is that thrust vectoring can be used to trim the aircraft and "unload" the flight- control surfaces, thereby reducing drag and/or increasing lift. The conventional control surfaces are meanwhile "liberated" from their role as trim devices and can be used to enhance manoeuvrability.

In supersonic flight, even small flap deflections can cause large amounts of drag.

"If you have thrust vectoring, you can put your aerodynamic surfaces in the best position to give optimum lift and drag, because you do not need to trim the aircraft with aerodynamic surfaces," says Osterhuber.

The use of the Nozzles as a complementary control surface allows the aircraft to better optimize its angle of attack in stationary level flight for a given flight point and load configuration, hence reducing the drag, which in turn leads to strong benefits in SFC, and therefore range.
Similarly to the above case, the nozzles can be used to increase the maximum load factor that is achievable under certain circumstances while maintaining the aircraft trimmed. This applies both for stationary manoeuvres (sustained turn rate) and for transient manoeuvres (rapid deceleration).

For example, at 30000 ft and Mach 1.8 there is an increase in lift coefficient by 14%, load factor by 9% and turn rate by 9%

The case in that example you link compares a 5º deflection of the TVC with a 4º deflection of the flaps, and of course, TVC wins due to inferior drag. Interestingly they make the comparison this way, even when the Eurofighter has canards and therefore a way of creating the same effect by forward lift instead of rear downforce, that comparison would answer exactly the case under discussion but I guess it would not allow to make such a clear case in favour of the TVC: from the point of view of drag they are quite likely worse than TVC, but from the point of view of lift and hence contribution to overall plane AoA they should be better, those two effects partially cancel each other and so the advantages of TVC would not be so clear to see.

Tails and foreplanes are airfoils and can generate lift as wings do.

They can generate lift.... but like the torque generated by the tail rotor on a helicopter they don't really effect lift because any lift force lifting one end forces down the other end of the aircraft... the lift force that far from the cg creates a rotational effect around the cg... that is its purpose... rather than a keeping the aircraft in the air lift effect you seem to think it does.

In a plane with AoA 2deg. with tails at neutral position re. the fuselage, both wings and tails are generating lift.

In a statically unstable plane the canards or tail surfaces will be generating up or downward force to keep the nose pointing the way it is pointing.

If the canards and tails are in neutral then any lift they do generate in level flight will be needed to keep the nose level.

The neutral position also minimises drag and RCS in that position.

In fact the lift generated by the tails is crucial to calculate turning rates because on modern planes they do not need to be deflected negatively for the plane to turn (pitch up the nose with a banking angle) since they are unstable, and they add a sizeable amount of the total lift.

The lift or downwards force the tail generates in its neutral position is determined by the instability of the aircraft and which direction the nose naturally wants to go.

An unstable design might be great for instantaneous turn rates but the effect that even in level flight the tail surface or canard is bobbing up and down with tiny corrections to keep the nose pointing forward.

The best description of a flight control system for an unstable aircraft is like sitting on the front of a car holding the steering wheels of a bicycle facing backwards... dozens of tiny corrections a second are needed to keep that bike rolling in a straight line backwards in front of the car.

Not a good example of drag or lift.

Not if it is produced at the CoG, if it is produced after or behind, it needs to be compensated or it will make the plane lose longitudinal control.

Are you saying a horizontal tail or a canard on their own being one side of the cg or the other cannot control the aircraft longitudinally...

The wing generates the lift at the cg or near it... it keeps the aircraft in the air. The Canard or the tail surface or both or TVC engine nozzles use an up or downwards directional force to keep the nose of the aircraft pointing where you want it to point... if you took away the canards and the tail surfaces and replaced them with the engine nozzles that move you can still control the aircraft longitudinally... the aircraft flys around its cg no matter where it has moved to, and its primary control surface... in this example the engine nozzles.

Lift or downwards force is for controlling where the nose points.... the same as with canards and tail surfaces...

If you deflect the engine nozzles downwards in an Su-35 on takeoff the downward thrust will lift the rear of the aircraft but if you don't have canards also lifting the nose then the aircraft would rotate around the cg and the nose would drop into the ground... but by your view the upward angling of the engine nozzles creates lift at the rear which is a good thing isn't it... extra lift at takeoff?

A Harrier has four engine nozzles either side of the cg so the rear downward nozzles don't raise the rear and push the nose down because there are two more nozzles in front of the cg also pushing up which balances the rotation of the rear engines so the rotation around the cg is balanced and cancelled out but the lift from all four nozzles lifts the aircraft into the air and when angled backwards impart forward speed so the wings do generate some lift to offload the engines from having to carry the entire weight of the aircraft.

See above, they are airfoils and they create drag and lift by the same mechanisms the wings do.

You can't call it lift... because it is used to create a downward force as much as it is used to create an upward force... whether you want the nose to point up or down the purpose of the canard or tail surface is to achieve that... they are tiny and create a tiny fraction of the force the wing does... certainly not enough to hold the aircraft in the air.

With traditional stable planes it is either canards or tail, and without them you simply crash.

TVC could maintain control if needed... and the Mirage 2000 is a good example of an aircraft with a wing and no canards or tail surfaces and no thrust vector control jet engine either...

Not really. If at a given point of the flight envelope with a certain AoA you have 100 points of lift produced by the wings and you use the canards to trim, which produce 20 points, you have 120 points of total lift available.

There is no way a canard would generate that much lift in comparison to the main wing... that is just silly.

The main wing holds the aircraft in the air... the canards and tail surfaces merely point the nose... or the arse.

Look at the ailerons on a wing... that is closer to the effect of canards in terms of directing airflow for manouvering...

Not really. If at a given point of the flight envelope with a certain AoA you have 100 points of lift produced by the wings and you use the canards to trim, which produce 20 points, you have 120 points of total lift available. If you instead use the tails to trim, creating 20 points of downforce, you have 80 points of total lift available.

No, because the tail surface does not generate the lift needed for flight... the tail generates the force needed to shift the angle of attack which increases the main wing angle which means the main wing now generates 500 lift because the 20 points of down force from the tail lifted the nose to a new more efficient angle.

An aircraft does not fly by adding the lift from the wings and lift from the control surface... the lift from the wings keeps the aircraft in the air... the force generated by the tail or canard or directed engine nozzle manouvers the aircraft and can be used to increase lift by increasing the angle of attack, but once the change as been made the control surface... canard or tail or nozzle should be able to return to neutral to maintain the new angle unless there is a problem like you are flying too slow to maintain that nose attitude so you need to continue to use your canard or tail or nozzle to maintain perhaps a nose up attitude...

The point is that the effect of teh canard or tail or nozzle on the main wing will have much more effect on the lift and drag caused by the main wing or lifting fuselage than the tiny lift and increased drag the tail or canard have created to use that turning force to change the wing angle. Moving the nozzles does not cause drag increases to the same degree.

Obviously you will need either to reduce altitude or to increase AoA or to increase speed, but you will not be able to sustain level flight in the same conditions as the plane with canards. I recommend you to look for this on the many good sites about aerodynamics that you can find on the web, since I don't seem to be able to convince you.

Perhaps you need to look at the B-2 and the Mirage 2000... neither of which have canards or horizontal tail surfaces or thrust vector control engines... they do have ailerons, which they use like tailerons obviously because they have no choice, but the B-2 is considered to be a pretty clean and efficient aerodynamic shape isn't it? How can that be true when all flight controls generate a downward draggy anti lift force using the airflow from the main wing and only source of lift?

It depends. Zero airspeed full AB at sea level is not the same as corner speed cruise throttle at high altitude. You would need to crunch some numbers there.

When crunching those numbers don't forget to allow for stall effects in hard turns.... TVC nozzles don't stall BTW but severely deflected tail and canard surfaces can, and also allow for the momentum arm from the nozzle to the cg will always be greater than the distance from the canards an the cg and the tail surfaces and the cg.

I am all for TVC, I am only saying on a plane that needs to pitch up the nose, it is better to generate lift in front of the CoG than downforce behind.

The canard is normally located in front of the wing which is the cg.... the tail surface is generally further back on the aircraft so the momentum arm will be longer... the engine nozzles will be even further back with the longest arm...

When raising the nose... why do you think pushing the back down is any different from lifting the front... the result is the same... wing gets new higher angle of attack and more lift so you climb faster, fuselage body lift directed down at a greater angle equals even more lift and jet engines conventional or TVC are now pointing down angling the aircraft also up into the air through the cg line of thrust.

Do you think aircraft with tails temporarily descend on takeoff because the negative lift from the tail reduces lift and the aircraft is pushed into the runway... while aircraft with canards are thrown upwards with the sudden lift bonus of a super lifting canard?

When you run do you lift your feet up in the air in a jumping motion to run, or do you hammer your feet down into the ground to push your body into the air?

BTW before you reply I would add that the information I have seen is that of the fastest olympic sprinters the fastest ones are the ones that slam their feet downwards into the ground the hardest... quite counter-intuitive in my opinion, but facts are facts.

Wings could also be kept low drag at neutral position, only the plane would not fly then

Do you think the razor thin wings of the MiG-31 are high drag high lift wings ideal for high speed flight?

Modern wings can have leading edge slats that bend down and trailing edge flaps that form a highly curved high lift wing for takeoff and landing, while flatten and retract to a thin low drag aerofoil for high speed flight at high altitude...

The wings will be optimised for the intended optimum flight speed of the aircraft.

There is no sense in putting MiG-31 wings on an An-2, just like wings of the aerofoil used on the An-2 would make no sense on the MiG-41.

control surfaces contribute to the total lift generation.

The ones on the wing do, and other high lift devices that could be present...

Of course deflections need to be much smaller than the values you were giving above, above 15 deg almost any airfoil is going to stall.

I hope not... landing flaps are generally 20-25 degrees on most aircraft.

Angles of movement for tail and canard surfaces are usually rather more than 15 degrees... they are not tank gun barrels.

Every loss of lift through the downforce needs to be compensated by higher AoA which creates more drag.

Are you suggesting a canard works by allowing an aircraft in stable level flight to climb by being deflected upwards to increase the total lift so the aircraft climbs?

I would suggest the canard is temporarily deflected upwards or downwards which causes the nose to start moving in that relevant direction... but if you keep the canard at that deflected angle the nose will just continue to move and you will end up doing loops.

In level flight to start to climb you deflect the canards for half a second to turn the nose up say 30 degrees, but you have to then return the canard to neutral or the nose will just keep turning up and you will end up doing a loop.

The half a second you deflect the canard to raise the nose for a 30 or 40 degree climb it does generate a net lifting force, but for half a second and then it is returned to normal and the increased angle of attack of the main wing to 30-40 degrees is what makes the aircraft climb and lose a little speed because increased lift comes with increased drag... a bit more throttle for more power to maintain speed and you start to climb.

With tail surfaces it is exactly the same except a half second push down at the rear of the aircraft to lift the nose 30-40 degrees and then back to neutral to stop raising the nose... half a second of down force at the rear of the aircraft and you think this is important?

I think you favour aerodynamics that is pro european and therefore fascinated by canards.

I don't hate canards, but as shown by the Su-57 there are better options...

It was designed for manoeuvrability.

Without surface controls you cannot trim the plane and react to changes in CoG /CoL, there is no way around it. Even a flying wing needs surfaces to substitute tails.

Ailerons on conventional wings can do the job if the TVC fails, but the TVC does the job much better than tailerons or canards... lighter weight less drag no RCS.

Real data actually shows that you can reduce drag and generate more lift by using the TVC for trimming purposes:

And it becomes more important for long range high speed cruising aircraft... the right trim is very important in terms of natural drag.

A bit like a smooth golf ball vs a dimpled ball.

GarryB wrote:They can generate lift.... but like the torque generated by the tail rotor on a helicopter they don't really effect lift because any lift force lifting one end forces down the other end of the aircraft... the lift force that far from the cg creates a rotational effect around the cg... that is its purpose... rather than a keeping the aircraft in the air lift effect you seem to think it does.

Imagine a plane with 4 wings, two in the front and two in the rear, could it not fly, if the lift of both pairs of wings is balanced around CoG? Yet the lift of those planes is not at the CoG. On a plane in level flight the lift of one non-centered lifting element is compensated by another symmetrical lift.

Not a good example of drag or lift.

Of course it is. On a stable plane you would detract the lift of the tails to point the nose up and turn, on an unstable you can still sue part of it.

The example linked by PeregrineFalcon shows this, with a turn in which the TVC is used for improved STR where flaps are used at a reduced deflection which allows them to still produce lift while turning, because the trim is done by the TVC. I have seen several calculations of this kind considering the lift of the tails in the STR, don't be stubborn and look for such information. Now I don't have time to search them for you.

If you deflect the engine nozzles downwards in an Su-35 on takeoff the downward thrust will lift the rear of the aircraft but if you don't have canards also lifting the nose then the aircraft would rotate around the cg and the nose would drop into the ground... but by your view the upward angling of the engine nozzles creates lift at the rear which is a good thing isn't it... extra lift at takeoff?

Obviously not. But if you had canards to compensate for that moment and could use the TVC as you say, would that lift not need to be considered for the total amount of lift generated by the plane?

and the Mirage 2000 is a good example of an aircraft with a wing and no canards or tail surfaces and no thrust vector control jet engine either...

On delta wings rear flaps are used as elevators.

There is no way a canard would generate that much lift in comparison to the main wing... that is just silly.

The contribution of canards or tails is normally a double digit percentage of the total lift, you can search for this instead of being in denial. Blaming me is not going to make you get any more knowledgeable.

and also allow for the momentum arm from the nozzle to the cg will always be greater than the distance from the canards an the cg and the tail surfaces and the cg.

It depends on the plane, look F-22 for instance, the nozzles are relatively close to the CoG, more than the elevators.

With tail surfaces it is exactly the same except a half second push down at the rear of the aircraft to lift the nose 30-40 degrees and then back to neutral to stop raising the nose... half a second of down force at the rear of the aircraft and you think this is important?

Trimming the plane means exerting that force continuously to keep the AoA right...

I think you favour aerodynamics that is pro european and therefore fascinated by canards.

I don't hate canards, but as shown by the Su-57 there are better options...

Sukhoi had them on many planes and now with the LEVCONS they are including some of their functions in the Su-57 too, in fact PeregrineFalcon demonstrated their use generating moment for take-off rotation exactly as a canard would do. They are showing you, exactly as I am saying, that generating lift in front of the CoG is better than pushing the tail down.

No matter how many times we repeat it, the only thing missing here is for you to go and check this on a site you respect, really.

EDIT:

One last try, don't blame me for this example being kindergarten level:

Imagine an aircraft in level flight which apart from two wings has two foreplanes and two horizontal tails perfectly identical and symmetrical from CoG. Now the foreplanes are deflected positively, creating an increased lift whose effect is to point the nose up. Then, the horizontal tails are deflected positively too, to level the plane. They create the same amount of lift as the foreplanes, perfectly symmetrically. Will the plane ascend or descend? What is the amount of lift generated by each of the airfoils? Each pair generates half of the total amount of increased lift the plane sees now right?

Now do the same considering negative deflection. Will the plane go up or go down this time? What will be the amount of downforce generated by each pair of airfoils? Exactly the same as before, each will produce half of the resulting downforce.

I hope it is clear now...

Saw this in the TVC paper that PeregrineFalcon linked. I had it already but had not given the deserved attention to this:

ESTOL
The ESTOL concept (Extremely Short Take-Off and
Landing) is becoming more and more appealing to
military aircraft operators, and it consists of performing
the Take-off and Landing manoeuvres with the aircraft
stalled. It reduces take-off and landing runs by a large
amount.
This is only possible with Thrust Vectoring Nozzles, that
operate when the aerodynamic controls are no longer
useful.
ESTOL could allow operations from/to improvised
runways and also carrier-borne operations without
catapult or arrestor.

In relation to this:



Will try to research further on that ESTOL concept (it was an old research by NASA it seems) and see whether someone else has already thought to use this for a fighter, it would be pretty amazing.

Imagine a plane with 4 wings, two in the front and two in the rear, could it not fly,

Of course it could but the drag would be enormous and the lift from all four wings will be very strong so the moving control surfaces needed to change the lift balance and effect flight control movements would be enormous.

Each wing would have an enormous effect on the rotation of the aircraft around the cg, and so the movements would need to be computer controlled to prevent the control forces damaging the aircraft structure.

if the lift of both pairs of wings is balanced around CoG?

That is how it works.

Yet the lift of those planes is not at the CoG.

We have already established on a conventionally winged aircraft that as it moves through transsonic speeds to supersonic speeds the cg shifts away from where the cg should be... the main single pair of wings, and that as the aircraft flys through that phase the tail or canard needs to compensate to maintain attitude or AOA until the cg shifts back again at higher speeds.

On a plane in level flight the lift of one non-centered lifting element is compensated by another symmetrical lift.

With only the tiny penalty of enormous heavy surfaces being used both as control surfaces and as wings.


A bit like a two wheel bicycle and a unicycle... the bicycle is like a two winged plane... only one needs to be steerable to shift the lift balance to match the location  of the cg... but it means turning performance is much much worse than with one wing or one wheel on a unicycle where the turning force is provided by the riders body weight and sense of balance to stabilise or to turn the unicycle...

The extra wing concept of the normal bicycle or even tricycle offers stability and control but it is not the most efficient way of building an aircraft.

Of course it is. On a stable plane you would detract the lift of the tails to point the nose up and turn, on an unstable you can still sue part of it.

You are not getting it... if the tail surface is bad because it pushes down instead of pushing up why do so many aircraft have them?

The Su-57 has a levicon so why have a tail surface too?

Obviously not. But if you had canards to compensate for that moment and could use the TVC as you say, would that lift not need to be considered for the total amount of lift generated by the plane?

But it is not about lift it is about angle of attack... an angle of attack at takeoff creates extra lift in the wings and fuselage which will be 100 times more lift than a canard or tail surface could ever generate... angling the nose up also angles the engines down which further increases upward progress for the whole aircraft.

On delta wings rear flaps are used as elevators.

They are, but by your definition they are bad because to lift the nose for take off they have no option but to push the tail down... meaning by your logic the entire main wing is now generating negative lift which means Mirage 2000s can't take off.

But I have seen pictures of Mirage 2000s in flight... quite a nice clean looking aircraft so that can't be true... perhaps you are overstating the significance of the negative lift needed to fly an aircraft.

Besides sometimes with an aircraft, there is actually a need to lower the nose because the fuel state or flight speed or weapon load or the settings of the flaps and slats and control surfaces that the nose is up to high and needs to be pushed down a bit in which case a tail surface adds to the lift of the aircraft and is good and the canard has to push down in which it becomes evil and demonic and must be destroyed... negative lift... my god... the world as we know it is about to end...  

The contribution of canards or tails is normally a double digit percentage of the total lift, you can search for this instead of being in denial. Blaming me is not going to make you get any more knowledgeable.

Well that is bullshit right off the bat... as I said... for a B-2 and a Mirage 2000 it is zero percent, and do these figures include fuselage lift in their equation and how horizontal tail surfaces on the inside of the vertical tail surface have an effect on lift as well rather something a canard cannot replicate...

Throughout the flight envelope of a fighter aircraft (as opposed to say a bomber or cargo plane) the control surfaces can generate drag as well as lift and in most turns their lift is used to redirect the aircrafts direction of movement rather than supporting it in the air in normal flight.

It depends on the plane, look F-22 for instance, the nozzles are relatively close to the CoG, more than the elevators.

I mean the longitudinal cg, not the vertical centre of the aircraft... the vertical centre only matters in roll control and in which case the lift from the tail or canard on one side is totally countered by the downward force of the tail or canard on the other side differentially deployed to effect a roll.

Trimming the plane means exerting that force continuously to keep the AoA right...

And is tiny compared with the forces needed to move the nose to manouver, unless you are flying near stall speeds.

They are showing you, exactly as I am saying, that generating lift in front of the CoG is better than pushing the tail down.

If they were better then why bother with TVC and tail surfaces?

Imagine an aircraft in level flight which apart from two wings has two foreplanes and two horizontal tails perfectly identical and symmetrical from CoG.

OK.

Now the foreplanes are deflected positively, creating an increased lift whose effect is to point the nose up.

But the turbulence they create reduces the lift over that inner portion of the wing which will likely reduce lift a little.

It will also increase drag and RCS from the canards deflection angle.

Then, the horizontal tails are deflected positively too, to level the plane.

The increase in lift will also increase drag... the aircraft will slow down a little.

The amount of lift generated might result in a minor change in altitude, but not worth the extra drag and weight of duplicating control surfaces... an increase in flaps would increase the lift from the main wing with an increase in drag too, but without the complication of extra control surfaces...

They create the same amount of lift as the foreplanes, perfectly symmetrically.

Canards are generally smaller than tail surfaces... getting that perfect would be a trick.

Canards operate in clean air while tail surfaces are behind the main wing...

I hope it is clear now...

It is clear what you are trying to suggest is true... but in context of a fighter plane it is stupid... canards and tail surfaces are control surfaces used to manouver an aircraft... thinking they are wings or trying to use them like an extra set of wings is just stupid and pointless... there are wings... make them the right size and shape to start with and you don't need any more. There is fuselage shaping for body lift. and there are canards and tails and TVC engine nozzles.... notice the Su-57 has these in some form or another.

If you replace the fixed tail surface of a side winder missile with another set of moving surfaces or five sets of moving surfaces will the missile suddenly become much more manouverable and deadly?

Surely all that extra lift it would no longer need a rocket motor any more and could fly like a bird.

More importantly if canards and tail surfaces generate lift then they can be coordinated to both be used together to generate lift all the time because to balance an aircraft with a cg that is anywhere it is just a case of both canards and tail surfaces lifting all the time but one lifting more than the other to effect the actual balance... the advantage then is that when you are not swanning about looking like a twat floating like a butterfly with all this excess lift pretending to be an airship or something and have to do some real work like manouvering... fighter planes are not theoretical lift models after all, when manouvering using canards and tail surfaces together differentially then they should achieve turn and manouver rates twice as good as any aircraft with just canards or tails... an effect magnified multiple times by having widely spaced engine with TVC nozzles... you know... sort of like the Su-57.

Almost like they know what they are doing...

Will try to research further on that ESTOL concept (it was an old research by NASA it seems) and see whether someone else has already thought to use this for a fighter, it would be pretty amazing.

Can't be that amazing... they are doing it without canards and they are using conventional tail surfaces.

Actually I remember a video on the internet showing an Su-33 doing this landing on the Kuznetsov... it looked like a rookie trying to land from a superstall... perhaps it was a test and the people who saw it mistook what was happening and thought it was a near crash... which is what most landings are really.

PeregrineFalcon wrote:

LMFS wrote:Wait a second, I will make an example to see where I am getting lost, if you don't mind. Let us say at a given moment of the supersonic flight you need say 20 "points" of net downforce on the tail to trim the plane. Let us assume the horizontal tails in neutral position at that AoA would create 30 points of lift. So if you use them for the trimming, you deflect them negatively and change 30 points of lift for 20 of downforce (I am ignoring effects of the extra drag here). Now with the TVC, you would need to create 50 points of downforce to negate those 30 points of lift behind the CoG plus the amount needed for the trimming? Wouldn't it be better to adjust the horizontal tail for zero lift at that AoA and produce just 20 points downforce with the TVC? That means, no matter what way you are generating that downforce, you end up losing the same amount of lift and the only difference is that TVC is not creating big additional drag. Because all the lift you generate after the CoG is just further pushing the nose down in the end...

Real data actually shows that you can reduce drag and generate more lift by using the TVC for trimming purposes:

https://issuu.com/defencedog/docs/itp-tvc-eurofighter

A spin-off of using the TVN as a control surface is that thrust vectoring can be used to trim the aircraft and "unload" the flight- control surfaces, thereby reducing drag and/or increasing lift. The conventional control surfaces are meanwhile "liberated" from their role as trim devices and can be used to enhance manoeuvrability.

In supersonic flight, even small flap deflections can cause large amounts of drag.

"If you have thrust vectoring, you can put your aerodynamic surfaces in the best position to give optimum lift and drag, because you do not need to trim the aircraft with aerodynamic surfaces," says Osterhuber.

The use of the Nozzles as a complementary control surface allows the aircraft to better optimize its angle of attack in stationary level flight for a given flight point and load configuration, hence reducing the drag, which in turn leads to strong benefits in SFC, and therefore range.
Similarly to the above case, the nozzles can be used to increase the maximum load factor that is achievable under certain circumstances while maintaining the aircraft trimmed. This applies both for stationary manoeuvres (sustained turn rate) and for transient manoeuvres (rapid deceleration).

For example, at 30000 ft and Mach 1.8 there is an increase in lift coefficient by 14%, load factor by 9% and turn rate by 9%

I will add another element to this interesting debate having, in a way, "introduced" the argument about sustained supersonic operations at engine's military regimes, and the role that TVC (in particular those with independent multi-axis thrust redirection) and the very peculiar levcon's design ,as rightly observed by PeregrineFalcon , play at those regimes offsetting the significantly increased parasitic drag that would be caused by the aigmented deflection angles of classical aerodynamics actuator surfaces necessary.

The element is the very high alttitude at which those sustained supersonic operations happen and in particular one of its effects -the decrease of aerodynamic damping- that affect a peculiar kinematic requirement very important in modern medium to long range air to air engagements.

Sustained supersonic manoeuvrability basically follow two main requirements in modern air superiority operations at medium and long range:

1) Gain positional advantage for BVR missile delivery purposes over the enemy air group ,placing each aircraft of its own formation in the most advantageous geometrical point of delivery of medium/long range missiles in relation with the position of each single aircraft of the enemy formation.

2) Missile evasion manoeuvers.

While for the first requirement supersonic maneuvrability contribute with other factors, among which field of view of the radar/radars on-board each aircraft and the data sharing performances of the group, to the success for the second requirement it become truly fundamental.

Anti-missile maneuvers ,in particular against the most advanced ones at medium range in theirs coasting phase, involve the execution of a sequence of two high-G turns in oppsite directions with a 180 degrees roll between to two to allow the best sustained turning performance for the second one.

The incoming medium range missile , that moreover proceed coasting unpowered, will be forced to lead for the interception after the first turn but will bleed an enorm amount of energy following for the lead the second sudden high-G turn cause its high speed and the lack of the the necessary lifting surface to execute the same rapid counter-turn.

At the high altitude and high supersonic speed where the most advanced dedicated air superiority aircraft operate the decrease of aerodynamic damping, force an aircraft devoid of TVC to apply greater opposite-control movements accepting a much greater induced drag and therefore a significantly worst time for manuevre's execution; the difference become even more marked with TVC with widely separated exausts like the Су-57 ones even more if paired with its unique levcon design.

The anti-missile performance at high-altitude high-supersonic speed between aircraft with the two different layouts, all the other being equal, can be dramatic : in the order of 25-30 m of increased distance from incoming missile interception's point.
This increased distance will likely not save your aircraft from the warhead potential of a C-300 or C-400 but will almost assure defeat of all medium range air-to -air missiles now operative Worldwide.

TVC potential is now limited mostly by structural limits of the hull and ,even more, bioplogical limits of the pilots; Су-57 has been conceived from the drawboard for widely increased hull's G-force limits (for potential future integration of full authomomous IA) and for pilots employing the new anti-G suit purposely developed by НПП "Звезда for Су-57.

I hope it is clear now...

How about this. The design of an aircraft means to can position internal fuel tanks and the main wing anywhere you please, you can position the wing at the rear of the aircraft away from the cg and make the aircraft unstable so you constantly need a force at the front to keep it flying straight and level most of the time, which means instantaneous turns will be faster because it naturally does not want to keep flying straight and level.

You claim the canard is superior because to raise the nose of the aircraft it generates lift which adds to the overall lift of the aircraft, but I am arguing that you could balance the aircraft so the nose naturally climbs all the time so the canard will not be generating lift most of the time it will be holding the nose down and stopping it from rising.

Equally the horizontal tail surface you claim is bad for lift because it pushes the tail down to rotate the aircraft to lift off for takeoff and pushes down during landing to increase AOA to cause drag to slow the aircrafts flight speed down, but I would argue that the aircraft that these tail surfaces are always attached to could just as easily be designed to have the nose rise naturally so in normal level flight the tail is continuously turning up to generate lift to raise the tail and keep the nose oriented downwards... thus generating lift in normal level flight... not that it means anything anyway, but you seem to think it is important...

GarryB wrote:You are not getting it... if the tail surface is bad because it pushes down instead of pushing up why do so many aircraft have them?

The Su-57 has a levicon so why have a tail surface too?

I have addressed that a few times already: modern planes are unstable, that means, they don't need, in subsonic flight, more input beyond onset of the maneouver to keep a nose-up attitude (as seen by TO of Su-57 and other planes from the F-16 onwards).

Therefore, in those planes tails make total sense, since their subsonic trimming contribution is additional lift (they try to lift the tail to keep the nose down)

As also explained, the best configuration is a triplane where control surfaces before and after the CoG, as the Su-30, 33, 34, 47 and 57 have. That gives the best options to trim the plane with different loads and speeds, maximizing always the lift. MFI had it, too, and it is completely logical that the Su-57 uses a variant of this configuration too.

I mean the longitudinal cg,

I mean it too, please look at the plane.

But the turbulence they create reduces the lift over that inner portion of the wing which will likely reduce lift a little.

But nothing, I am creating a simplified example for you to understand some primary school level physics, but you prefer hiding behind third order effects... at least I have tried

@Mindstorm:

it is logical that the only two fighters intended for high supersonic cruise (F-22 and Su-57) both have TVC. Knowing the longitudinal margin at their combat speeds would be very interesting, in order to know to what extent they still count on the advantages of instability for turning at high speed / high altitude, when lift is very difficult to find and the plane tends to need more input to point the noise up. There can be substantial gains from an optimized aero design and all elements in Su-57 indicate that it was designed to surpass any rival in that flight regime.

Anti-missile maneuvers ,in particular against the most advanced ones at medium range in theirs coasting phase, involve the execution of a sequence of two high-G turns in oppsite directions with a 180 degrees roll between to two to allow the best sustained turning performance for the second one.

The incoming medium range missile , that moreover proceed coasting unpowered, will be forced to lead for the interception after the first turn but will bleed an enorm amount of energy following for the lead the second sudden high-G turn cause its high speed and the lack of the the necessary lifting surface to execute the same rapid counter-turn.

It would also be interesting to see how this would work at 50 or 60 kft. From what I have seen, extremely reduced air density makes it very difficult to generate more than a few degrees per second of turning, that compared with an incoming 3-4 M missile means actually dodging (or simply defeating it by making it turn) is quite difficult. In dense air the missile losses speed very fast, at high altitude the calculations I have seen show this takes a little longer. Lets say a Su-57 manages 4 deg per second at 2 M and 60 kft (no idea if the number is close to reality, I take two times the value of the MiG-31 because of the much better design for manoeuvrability), that would mean two 90 deg turns would take 45 seconds, not considering times to bank. In that time a missile flying 4 M on a tail chase undercuts almost 30 km. By the time the plane initiates the second turn, the missile is still min. at 12-15 km and therefore still with a big margin for a lead pursuit. Plus the time to make an U-turn (say another 45 seconds) while the missile and aircraft are approaching each other (head-on shot) which is probably above 50 km, means the maneuver time needed to dodge an AAM are comparable to the entire flight time of the missile, and of course it all depends at what time the launch is detected. It would be also interesting to calculate this against missiles like Meteor whose propulsion remains active during the coasting phase and can therefore maintain speed during turning. In general planes that fly high and fast are very vulnerable to long shots, if the attacking missile is well within range, because their manoeuvrability and acceleration will be poor, but of course their advantage is that they normally have much better conditions to launch first and avoid getting within the engagement zones of rivals.

What seems clear to me is that if the Su-57 has early information about the location of rival aircraft, it has all the tools to position itself favourably for the attack (i.e. aligning with the leading edge angle for best radar return to the missile's ARH in case of stealth opponents) and perform an early shot before the rival's missiles are even in range. In such conditions extremely lopsided exchange rates are indeed possible and I don't see how any number of F-35s could compensate for the terrible disadvantage in which they would find themselves in.

LMFS wrote:The case in that example you link compares a 5º deflection of the TVC with a 4º deflection of the flaps, and of course, TVC wins due to inferior drag. Interestingly they make the comparison this way, even when the Eurofighter has canards and therefore a way of creating the same effect by forward lift instead of rear downforce, that comparison would answer exactly the case under discussion but I guess it would not allow to make such a clear case in favour of the TVC: from the point of view of drag they are quite likely worse than TVC, but from the point of view of lift and hence contribution to overall plane AoA they should be better, those two effects partially cancel each other and so the advantages of TVC would not be so clear to see.

This example shows that the use of TVC can be beneficial for both, reducing the drag and increasing the lift [it is practically confirmed with the F-22 during supersonic flight/maneuvering], but I get your point!
The reason they use the flaps deflection for supersonic trim, and not canards probably has its roots in the fact that the downwash from the canards at positive deflection and supersonic speed can obstruct the main wing in the way that the overall lift is actually decreased. Of course, this is only my guess because I can't do realistic simulation of the supersonic airflow over or under the main wing in mu head , but on the other hand there wouldn't be such concern with the LEVCON's.

PeregrineFalcon wrote:The reason they use the flaps deflection for supersonic trim, and not canards probably has its roots in the fact that the downwash from the canards at positive deflection and supersonic speed can obstruct the main wing in the way that the overall lift is actually decreased. Of course, this is only my guess because I can't do realistic simulation of the supersonic airflow over or under the main wing in mu head , but on the other hand there wouldn't be such concern with the LEVCON's.

I assume the far coupled canards + AoA + canard in higher plane should avoid that downwash from being detrimental, in fact canards are normally designed to improve lift through downwash and that they were using the Eurofighter in the paper as example simply because ITP works on the EJ2000 and therefore has real data, not as an assumption that the plane would not use the canards for supersonic trimming (maybe there is some confirmation available on the web about how this is actually done ?) At the moment it remains just my opinion too...

Question. Why does everyone (mostly Yanks) say dog fighting is obsolete and 5th gen fights are like Mohammad Ali and Mike Tyson in a phone booth ? Doesn't it totally just depend
on where or when fighting starts ?

Say in a war between Ukraine supported by the US and Russia. Russia has su 57's staged at their western most air base. And the US is landing F-35's at one of the main bases in central Ukraine. Isn't this basically the phone booth ?

Say war breaks out and Russia was more ready than the US/Ukraine (it would be. Home team advantage). F-35's are just taking off but the su 57's are already arriving into the area. This just turns into a close range dog fight doesn't it ?

Or even say the su 57's are arriving late ? Couldn't they make it a dog fight by coming in at high altitude and speed ?

Isos wrote:F 35 would be bombed as soon as they land in Ukraine by missiles.

War isn't fair. T-90 won't fight only M1A2, su 57 won't be the only solution to f-35 neither would a russian carrier be the answer to a US carrier.

Yeah but why do people think it is so out of the realm of possibility that F-35's and su 57's will end up in the same air space ?

I mean it too, please look at the plane.

I would say they are about the same... or do you think the tailplane apply their lift at the tip of the tail surface rather than where the tail surface rotates where it is connected to the aircraft?

That is just another design decision they made designing the aircraft... they could easily have placed the engines further back or further forward if necessary.

But nothing, I am creating a simplified example for you to understand some primary school level physics, but you prefer hiding behind third order effects... at least I have tried

Yeah.... ignore reality and you are right a canard raising the nose of an aircraft adds lift, but put reality back into the equation and creates all sorts of extra problems including weight and drag whether it was generating lift or not.

From what I have seen, extremely reduced air density makes it very difficult to generate more than a few degrees per second of turning, that compared with an incoming 3-4 M missile means actually dodging (or simply defeating it by making it turn) is quite difficult.

Perhaps difficult for control surfaces, but does that apply to TVC nozzles... the Soviets and Russians commonly used side mounted thruster rockets to SAMs to allow last second manouvers to get as close to the target as possible for detonation.

The reason they use the flaps deflection for supersonic trim, and not canards probably has its roots in the fact that the downwash from the canards at positive deflection and supersonic speed can obstruct the main wing in the way that the overall lift is actually decreased.

Reality strikes again?

But of course the Euro canards that have canard foreplanes are your usual fighters who wont waste fuel flying around at supersonic speeds anyway so this wont matter.

Yeah but why do people think it is so out of the realm of possibility that F-35's and su 57's will end up in the same air space ?

Personally I think they will only be dogfighting because both are sophisticated and capable enough to likely defeat each others missiles, which leaves guns...

I think the Russians think the same hence the focus on manoeuvre and flight performance for the Su-57...

@Backman:

Americans say if a 5G fighter pilot gets to the merge he is doing something wrong, they assume they can control combat by receiving external information about where the opponent is, position themselves properly and down it while in BVR without committing to highly risky dogfights. But with the level of threat AWACS would suffer against peer rivals fighting in their own territory, EW deployed plus their own early warning means and stealth fighters, I don't see how they would actually avoid ACM. If all, a fight between stealth fighters on their own would start notably closer than between 4G fighters and then evolve much more easily (and faster due to supercruise) towards close combat.

GarryB wrote:Perhaps difficult for control surfaces, but does that apply to TVC nozzles... the Soviets and Russians commonly used side mounted thruster rockets to SAMs to allow last second manouvers to get as close to the target as possible for detonation.

Those are placed at the CoG and therefore they need little compensation to be used. Something like that would allow lift to be produced in a plane that could massively help maneouvering, I think the Harrier in fact used their nozzles that way.

LMFS wrote:It would also be interesting to see how this would work at 50 or 60 kft. From what I have seen, extremely reduced air density makes it very difficult to generate more than a few degrees per second of turning, that compared with an incoming 3-4 M missile means actually dodging (or simply defeating it by making it turn) is quite difficult. In dense air the missile losses speed very fast, at high altitude the calculations I have seen show this takes a little longer. Lets say a Su-57 manages 4 deg per second at 2 M and 60 kft (no idea if the number is close to reality, I take two times the value of the MiG-31 because of the much better design for manoeuvrability), that would mean two 90 deg turns would take 45 seconds, not considering times to bank. In that time a missile flying 4 M on a tail chase undercuts almost 30 km. By the time the plane initiates the second turn, the missile is still min. at 12-15 km and therefore still with a big margin for a lead pursuit. Plus the time to make an U-turn (say another 45 seconds) while the missile and aircraft are approaching each other (head-on shot) which is probably above 50 km, means the maneuver time needed to dodge an AAM are comparable to the entire flight time of the missile, and of course it all depends at what time the launch is detected. It would be also interesting to calculate this against missiles like Meteor whose propulsion remains active during the coasting phase and can therefore maintain speed during turning. In general planes that fly high and fast are very vulnerable to long shots, if the attacking missile is well within range, because their manoeuvrability and acceleration will be poor, but of course their advantage is that they normally have much better conditions to launch first and avoid getting within the engagement zones of rivals.

LMFS the example you propose contain totally unrealistic figures that inpair at the foundation its applicability.

I understand that you believe that an A-A missile (let put an AIM-120C/D or a P-77/РВВ-СД) has a speed of mach 4 at medium range interception point ....i want even to leave a part the immense amount of kinetic energy -speed- it will lose even with sustained relatively low-G maneuvers and even less two very high-G manoeuvers in sequence and counterturn.

A missile like AIM-120C have a speed of around Mach 4 only within the first 8-9 seconds after release and under propulsion of its boost stage; at a releasing point of 10.000 meters of altitude and an optimized lofted trajectory at 30 km its coasting speed decrease already in the 2,5 Mach area without executing a single turn !...you can well undestand that it could never achieve a downing of an enemy high maneuvrable aircraft also at less than this distance if this target would become aware of the attack.


You can read this brief fluid-dynamics simulation of AIM-120 missiles ,in-atmosphere and different altutitude and release speed:

https://therestlesstechnophile.files.wordpress.com/2020/05/aim120c5-performance-assessment-rev23.pdf

Not 90 but even a 35-40 degrees sustained turn at Mach 1.6-1.7 at high altitude  degrees turn is what is used today by high-performance air superiority aircraft devoid of TVC to avoid incoming medium-range A-A missiles operative today.

This is the reason the almost totality of downing of enemy aircraft by medium range missiles at distances greater than 10-11 km has been completed with the target totally unaware of the attack (mostly from rear emisphere) and not executing any counter maneuver; when that requisite of surprise was not achieved almost systematically the attacks resulted in several miss (including lately in Syria and India)    

The requirements of Су-57 has been established and also modified long ago to deal at high-altitude not with today A-A missiles but with future models with ramjet propulsions and or full throttleable sustaining engines; the high-G maneuvre described, in particular the first turn , must be maintained for no more than 5-6 seconds before the violent turn in the opposite direction after the roll ; any air to air missile, today even at the draving board stage, could not follow a similar maneuvre for inescapable aerodynamic surfaces reasons.

The solution to this situation ,in particualr against future air superiority UAVs with G-limits multiple of times greater than today aircraft, could be only a warhead of same size and several times increased potential  -not likely- or one or more detacheable warheads to be released in the terminal phase of the interception.


Majority of multirole aircraft operative today ,optimized for transonic operations, employ in anti-missile maneuvres the solution of descending abruptly at lower altitude (as you have suggested) but merely because they cannot structurally challenge at high-altitude and high supersonic regimes the kinematics turning performances of air to air missiles delivered within 30-40 km of distance.

FWIW this video keep me up with the discussion about supercruising in some previous pages.

Mindstorm wrote:LMFS the example you propose contain totally unrealistic figures that inpair at the foundation its applicability.

I understand that you believe that an A-A missile (let put an AIM-120C/D or a P-77/РВВ-СД) has a speed of mach 4 at medium range interception point ....i want even to leave a part the immense amount of kinetic energy -speed- it will lose even with sustained relatively low-G maneuvers and even less two very high-G manoeuvers in sequence and counterturn.

A missile like AIM-120C have a speed of around Mach 4 only within the first 8-9 seconds after release and under propulsion of its boost stage; at a releasing point of 10.000 meters of altitude and an optimized lofted trajectory at 30 km its coasting speed decrease already in the 2,5 Mach area without executing a single turn !...you can well undestand that it could never achieve a downing of an enemy high maneuvrable aircraft also at less than this distance if this target would become aware of the attack.

Of course, if the speed of the missile is not substantially higher than that of the aircraft under attack, things change and if they are similar, a chase like the one you describe would happen. On the other hand, if the speed delta between the missile and the aircraft is substantial, then the missile has an easy time predicting where the plane is going to be and will undercut its movements with its superior speed, so it does not actually need to perform such tight turns and bleed so much energy (the target is, so to say, almost "static" compared to itself)

There are some simulations of the AMRAAM online, I had seen the one you mention but I have seen others too. I am not an aerodynamicist so I cannot judge which one is correct, from what I can see the document you linked establishes a smaller speed and altitude of launch and less optimized loft than this for example (by Spurts, an aerospace engineer working in the industry):



You see the little penalty a missile has flying very high. The peculiarity of this analysis is the optimization of lofting that Spurts did.

Here there is another analysis, studying the influence of launch conditions too:

https://jaesan-aero.blogspot.com/2018/10/aim-120c-study-using-missile-sim-part-1.html
https://jaesan-aero.blogspot.com/2018/10/aim-120c-study-using-missile-sim-part-2.html

These are relatively easy to find analysis that I think are rather well known to the enthusiasts out there, I don't have access to AAIA or similar papers that could have more authoritative data...

So it may be that a launch under conventional conditions (4G fighters at medium altitudes, specially with not so modern missiles with not so optimized loft) follows the rules you say, while one at bigger altitude with carriers flying also very high looks a bit different. Of course a plane that is faster is always going to be more challenging to catch, given it maintains capability to maneuver.  

Not 90 but even a 35-40 degrees sustained turn at Mach 1.6-1.7 at high altitude  degrees turn is what is used today by high-performance air superiority aircraft devoid of TVC to avoid incoming medium-range A-A missiles operative today.

I am very interested in these maneouvers, do you have some link that you can share? Thanks!

This is the reason the almost totality of downing of enemy aircraft by medium range missiles at distances greater than 10-11 km has been completed with the target totally unaware of the attack (mostly from rear emisphere) and not executing any counter maneuver; when that requisite of surprise was not achieved almost systematically the attacks resulted in several miss (including lately in Syria and India)  

That makes a lot of sense because the launches of MRAAMs are relatively abundant and by what is conventionally claimed they should shot down planes by dozens... which is not the case in reality as we see, the last case of the MKIs in India come to mind for instance. What is not always clear in these cases is the role of EW and the role of kinematics, that is of course not going to be explained in detail by any airforce.

The requirements of Су-57 has been established and also modified long ago to deal at high-altitude not with today A-A missiles but with future models with ramjet propulsions and or full throttleable sustaining engines; the high-G maneuvre described, in particular the first turn , must be maintained for no more than 5-6 seconds before the violent turn in the opposite direction after the roll ; any air to air missile, today even at the draving board stage, could not follow a similar maneuvre for inescapable aerodynamic surfaces reasons.

I agree the Su-57 follows clearly other standards, just comparing its lifting surface to that of a Flanker indicates completely apart turning characteristics at high altitude. Or F-22 compared to F-35, look at the difference in AoA (this is part of the video zepia linked above, where both planes fly level, 2:55 onwards):



Obviously one plane is designed to create lift and turn in rarefied air while the other is not...

The solution to this situation ,in particualr against future air superiority UAVs with G-limits multiple of times greater than today aircraft, could be only a warhead of same size and several times increased potential  -not likely- or one or more detacheable warheads to be released in the terminal phase of the interception.

The last option having been actually announced by Russia...

Majority of multirole aircraft operative today ,optimized for transonic operations, employ in anti-missile maneuvres the solution of descending abruptly at lower altitude (as you have suggested) but merely because they cannot structurally challenge at high-altitude and high supersonic regimes the kinematics turning performances of air to air missiles delivered within 30-40 km of distance.

Sure, at high altitude most planes have neither the propulsion nor the aero to turn...

zepia wrote:FWIW this video keep me up with the discussion about supercruising in some previous pages.

That was a nice video indeed, I am going to watch some more from that guy