What's new

Featured Russia Teases 'Fundamentally New' Military Aircraft to Be Unveiled

Philip the Arab

SENIOR MEMBER
Oct 26, 2018
6,731
6
6,210
Country
Jordan
Location
United States
It surely could be the UAE which would be quite interesting

With UAE acquiring many Denel Dynamics engineers and trying to become a missile producer this could be a great platform where anything can be integrated.

CAATSA could be a problem, but that would hurt America more that it would hurt the UAE.
 
Last edited:

gambit

PROFESSIONAL
Apr 28, 2009
25,479
138
23,455
Country
United States
Location
United States
Also, the lack of horizontal stabilizers was a little perplexing to me at first since I'm sure others who watch a lot of fighters flying as well can notice how much the H-stabs are used to control pitch, even rolls and banking turns etc. The H-stabs are super valuable and play a huge role in an aircraft's maneuverability. Just on takeoffs alone, once the aircraft reaches rotating speed, the ever so slight pull back of the stick lifts the H-stabs just a tad bit and that's enough to raise the nose, bring more airspeed under the wing and immediately creates lift allowing the plane to instantaneously take off.

Suddenly we have an aircraft with essentially the same wing pattern as the Su-57 but sans the H-stabs which is conflicting TBH.

View attachment 763940

View attachment 763941

But then I thought of mostly delta aircraft (not delta/canards, just delta) like Mirages or Delta Dagger etc. They had no issues whatsoever essentially using their ailerons only on their delta wings to substitute for the function of the H-stabs and they did them very well. Looking at the two pics above, one can't help but think the Checkmate is missing something without the H-stabs and will take a while to get used to even when we saw the YF-23 perform incredibly well with essentially the same layout. However, in the YF-23, the canted stabilators were set at a much steeper angle than what we see here on the Checkmate. It was almost like they took the flat 180 degree of a standard H-stab and a standard pitched or canted vertical stabilizer (like what it would be on the F-18 or Su-57) and then split the difference and set them right in the middle middle angle of those two to compensate for the most of both angles. But it doesn't look like we see that here on the Checkmate and that the angle of the V-stabs is that of a normally pitched or canted vertical stabilizer. Strange that they didn't pitch those stabs a bit more but they should work just fine if the ailerons are large enough to compensate for the lack of H-stabs and the current angle of the V-stabs.
What you are wondering out is the v-tail.

When I was taking flight lessons in high school, I had a chance to fly IN a Bonanza with my instructor. I said 'IN' because I had only 10 hrs of stick time so my instructor did not allowed me to take controls. The Bonanza with its v-tail does have unique behaviors that required experienced pilots, so I was there only as an interested passenger. So you can look up the Bonanza.

But also look at this...


The dihedral or 'cant' angle is what you are wondering about, particularly the four images group with the test model with the three different v-tails and one single conventional tail.

The ideal dihedral angle, for each surface, is °45. However, for a low radar observable platform, the joint of a pair of °45 surfaces produced °90 angle, which is a huge no-no. And we see none of that on the current 'stealth' platforms all the way back to the F-117. The Bonanza v-tail have °33 dihedral. The reason for the v-tail design is to reduce mechanical drag, specifically, a physical structure in the airstream.

A conventional tail have three surfaces. A v-tail have two. However, a conventional tail have effective controls in all three axes: x, y, and z. Greater than °45, or more towards vertical from the observer's upright perspective, the surface's effects lean towards the yaw (z) axis. Lesser than °45, the surface's effects lean towards the x/y (pitch/roll) axis. So the sacrifice of one axis control requires the remaining two surfaces to coordinate their actions to produce that of three axes, the result is the Bonanza's unique behaviors and the human pilot must be educated of them, but on the F-117, the FLCC take care of that. Further on the F-117, the wings are sufficiently swept that the ailerons took over the responsibility of the h-stabs, but the wings' high sweep angle required higher TO/L speed, just like any full delta.

So what are we to make of this new Russian aircraft?

The Checkmate is not a true v-tail due to the physical separation of the two surfaces. The F-117 is a v-tail. My suspicion is that the tail surfaces dihedral angle has more to do with the broad wings' turbulence. If the Checkmate's tail dihedral decreases (away from vertical) to less than °45 and more towards the Bonanza's tail dihedral of °33, the Checkmate may produce undesirable MANEUVER related behaviors that computer assisted controls may not be able to compensate. Like it or not, there are limits to what an FLCC can do and there are plenty of modern FBW aircrafts that departed from controlled flight. It is too early at this time so all we have are these images to speculate upon.

By the time I joined the USAF, I already know the basics of flight. So how do I make a turn? Break down the actions. Assume a turn to starboard or a 'right' turn for the civilians.

A starboard turn begin with yoke wheel right then yoke back. Or stick right then stick back. Never mind the rudder action to create a 'coordinated turn' for now. The stick right command would have the ailerons and horizontal stabs to split to initiate a roll (y) axis maneuver. Then all surfaces would return to neutral. Then the stick back command would have both horizontal stabs to pitch up. The 'pitch' perspective here is not from the outside perspective, which is towards earth/sky horizon, but from the aircraft's perspective. It is hard to imagine if you have never taken flight lessons. But if you have a model aircraft or just use your hand, it will be easier to imagine how an aircraft's pitch/roll/yaw perspectives are independent of the horizon line.

Put out your hand palm down. Roll your hand so that the palm is now facing YOUR left and the back of the hand is facing YOUR right. Now flip the wrist so that the palm is now facing YOUR forward. That is the pitch maneuver from the hand's perspective. Not yours. Now push your hand forward and to the right. That is a right turn -- simplified for sake of discussion.

So how would the Checkmate make a turn?

If I go stick right to initiate the roll maneuver, the wing's ailerons will split to create that twisting force. Then when I pull stick back, where does that pitch up maneuver come from? The wings' ailerons are too far forward from the tail. The wings' ailerons are closer to aircraft center-of-gravity (CG). Both ailerons can deflect pitch up but because of their proximity to CG, the deflection would be greater than what the normal horizontal stabs would move to create the same degree and rate of pitch change. This is basic physics: the lever and fulcrum. The further away from fulcrum, the less effort required to move the load. So either the Checkmate's CG (fulcrum) is really far forward, or there is something really funky about the jet. I have much respect for Soviet/Russian aviation, but I hate to see the Checkmate be like Iran's lame attempt to impress the world.
 

CIA Mole

FULL MEMBER
May 1, 2019
1,631
-2
1,406
Country
United States
Location
Pakistan
What you are wondering out is the v-tail.

When I was taking flight lessons in high school, I had a chance to fly IN a Bonanza with my instructor. I said 'IN' because I had only 10 hrs of stick time so my instructor did not allowed me to take controls. The Bonanza with its v-tail does have unique behaviors that required experienced pilots, so I was there only as an interested passenger. So you can look up the Bonanza.

But also look at this...


The dihedral or 'cant' angle is what you are wondering about, particularly the four images group with the test model with the three different v-tails and one single conventional tail.

The ideal dihedral angle, for each surface, is °45. However, for a low radar observable platform, the joint of a pair of °45 surfaces produced °90 angle, which is a huge no-no. And we see none of that on the current 'stealth' platforms all the way back to the F-117. The Bonanza v-tail have °33 dihedral. The reason for the v-tail design is to reduce mechanical drag, specifically, a physical structure in the airstream.

A conventional tail have three surfaces. A v-tail have two. However, a conventional tail have effective controls in all three axes: x, y, and z. Greater than °45, or more towards vertical from the observer's upright perspective, the surface's effects lean towards the yaw (z) axis. Lesser than °45, the surface's effects lean towards the x/y (pitch/roll) axis. So the sacrifice of one axis control requires the remaining two surfaces to coordinate their actions to produce that of three axes, the result is the Bonanza's unique behaviors and the human pilot must be educated of them, but on the F-117, the FLCC take care of that. Further on the F-117, the wings are sufficiently swept that the ailerons took over the responsibility of the h-stabs, but the wings' high sweep angle required higher TO/L speed, just like any full delta.

So what are we to make of this new Russian aircraft?

The Checkmate is not a true v-tail due to the physical separation of the two surfaces. The F-117 is a v-tail. My suspicion is that the tail surfaces dihedral angle has more to do with the broad wings' turbulence. If the Checkmate's tail dihedral decreases (away from vertical) to less than °45 and more towards the Bonanza's tail dihedral of °33, the Checkmate may produce undesirable MANEUVER related behaviors that computer assisted controls may not be able to compensate. Like it or not, there are limits to what an FLCC can do and there are plenty of modern FBW aircrafts that departed from controlled flight. It is too early at this time so all we have are these images to speculate upon.

By the time I joined the USAF, I already know the basics of flight. So how do I make a turn? Break down the actions. Assume a turn to starboard or a 'right' turn for the civilians.

A starboard turn begin with yoke wheel right then yoke back. Or stick right then stick back. Never mind the rudder action to create a 'coordinated turn' for now. The stick right command would have the ailerons and horizontal stabs to split to initiate a roll (y) axis maneuver. Then all surfaces would return to neutral. Then the stick back command would have both horizontal stabs to pitch up. The 'pitch' perspective here is not from the outside perspective, which is towards earth/sky horizon, but from the aircraft's perspective. It is hard to imagine if you have never taken flight lessons. But if you have a model aircraft or just use your hand, it will be easier to imagine how an aircraft's pitch/roll/yaw perspectives are independent of the horizon line.

Put out your hand palm down. Roll your hand so that the palm is now facing YOUR left and the back of the hand is facing YOUR right. Now flip the wrist so that the palm is now facing YOUR forward. That is the pitch maneuver from the hand's perspective. Not yours. Now push your hand forward and to the right. That is a right turn -- simplified for sake of discussion.

So how would the Checkmate make a turn?

If I go stick right to initiate the roll maneuver, the wing's ailerons will split to create that twisting force. Then when I pull stick back, where does that pitch up maneuver come from? The wings' ailerons are too far forward from the tail. The wings' ailerons are closer to aircraft center-of-gravity (CG). Both ailerons can deflect pitch up but because of their proximity to CG, the deflection would be greater than what the normal horizontal stabs would move to create the same degree and rate of pitch change. This is basic physics: the lever and fulcrum. The further away from fulcrum, the less effort required to move the load. So either the Checkmate's CG (fulcrum) is really far forward, or there is something really funky about the jet. I have much respect for Soviet/Russian aviation, but I hate to see the Checkmate be like Iran's lame attempt to impress the world.

I feel like this and the other designs at MAKS aren’t meant to fly. Just to impress potential investors.




You shouldn’t see this tail configuration in stealth design
 

Gomig-21

SENIOR MEMBER
Oct 16, 2016
5,470
11
10,373
Country
Egypt
Location
United States
A starboard turn begin with yoke wheel right then yoke back. Or stick right then stick back. Never mind the rudder action to create a 'coordinated turn' for now. The stick right command would have the ailerons and horizontal stabs to split to initiate a roll (y) axis maneuver. Then all surfaces would return to neutral. Then the stick back command would have both horizontal stabs to pitch up. The 'pitch' perspective here is not from the outside perspective, which is towards earth/sky horizon, but from the aircraft's perspective. It is hard to imagine if you have never taken flight lessons.
Nope, it's not hard to imagine. That is exactly what I was talking about. When I referred to the way delta configured aircraft would maneuver using only their ailerons, that was the reference to how this aircraft here would probably also use the same methods or processes using its ailerons and those smaller H-stabs at the end of the double tail bases. Then there is also the combination of TVC which is what has been expressed as the eventual, single engine to power this aircraft.

So you'll have the ailerons, the small H-stabs at the end of the V-stab bases and the TVC to assist in that roll and pitch. That would be my guess only ATM.

So how would the Checkmate make a turn?

If I go stick right to initiate the roll maneuver, the wing's ailerons will split to create that twisting force. Then when I pull stick back, where does that pitch up maneuver come from? The wings' ailerons are too far forward from the tail. The wings' ailerons are closer to aircraft center-of-gravity (CG). Both ailerons can deflect pitch up but because of their proximity to CG, the deflection would be greater than what the normal horizontal stabs would move to create the same degree and rate of pitch change. This is basic physics: the lever and fulcrum. The further away from fulcrum, the less effort required to move the load. So either the Checkmate's CG (fulcrum) is really far forward, or there is something really funky about the jet. I have much respect for Soviet/Russian aviation, but I hate to see the Checkmate be like Iran's lame attempt to impress the world.
With all the respect to the Iranian aviation industry, I don't think there is a comparison with the storied Russian tradition in aviation history. One has practically devoted its entire existence on the aviation industry while the other had one attempt at creating a mockup.

At any rate, looking at the pic below, I suspect that the CoG is much more forward to the placement of the trailing edge of the wings where the flaps and especially the ailerons would be. So they most likely would have very decent effects on controlling the pitch of this aircraft, even once it rolls to one side and then needs to execute a turn, the ailerons would snap back to neutral and then both would move in the same direction to execute the turn. Along with the other elements I mentioned.

1626999332237.png
 

gambit

PROFESSIONAL
Apr 28, 2009
25,479
138
23,455
Country
United States
Location
United States
When I referred to the way delta configured aircraft would maneuver using only their ailerons, that was the reference to how this aircraft here would probably also use the same methods or processes using its ailerons and those smaller H-stabs at the end of the double tail bases. Then there is also the combination of TVC which is what has been expressed as the eventual, single engine to power this aircraft.

So you'll have the ailerons, the small H-stabs at the end of the V-stab bases and the TVC to assist in that roll and pitch. That would be my guess only ATM.

At any rate, looking at the pic below, I suspect that the CoG is much more forward to the placement of the trailing edge of the wings where the flaps and especially the ailerons would be. So they most likely would have very decent effects on controlling the pitch of this aircraft, even once it rolls to one side and then needs to execute a turn, the ailerons would snap back to neutral and then both would move in the same direction to execute the turn. Along with the other elements I mentioned.
Yes, post 218 made a credible argument that those structures are flight control surfaces.


The more forward the CG, the more the aircraft move towards DYNAMIC INSTABILITY. Not the same as 'relaxed static stability' (RSS). The CG is affected by arbitrary load distribution on the longitudinal aspect, from one flight to the next. That is not RSS which is from design and the CG would be more towards aft of the fuselage. At this early point, we simply cannot know from pictures where is the Checkmate's CG.

The CG also affects maneuvering stability and here is an interesting factoid from Boeing...


Maneuvering stability, like static stability, is influenced by CG location. However, when the CG is aft and near the neutral point, then altitude also has a significant effect. Since air density has a notable impact on the damping moment of the horizontal tail, higher pitch rates will result for the same elevator deflections as altitude increases. From the flight crew's perspective, as altitude increases, a pull force will result in a larger change in pitch angle, which translates into an increasing angle of attack and g. While a well-designed flight control system, either mechanical or electronic, will reduce the variation of stick force with CG and altitude, it is very difficult to completely eliminate the variation due to design limitations.
We can safely assume that the Checkmate will be RSS-ed and FBW-ed.

We know that there is an inverse relationship between air density and altitude. The greater the air density, the lower the altitude. The lower the air density, the higher the altitude. Simply put: thicker and thinner air. Flight controls and engines of all types prefers thicker air which mean any aircraft would maneuver best at lower altitudes.

Air density is a calculated value from the Central Air Data Comp (CADC) and fed to the FLCC which calculate the surface deflections. So a stab pitch up deflection at Angels Five will have lesser degree than at Angels Ten, and lesser than at Angels Twenty.

If we assume that those relatively smaller structures in post 218 are flight controls structures equivalent to larger horizontal stabs, using an F-16 as reference for now, those smaller structures will have to deflect more than expected at all altitudes to make the same pitch up maneuver. The areal size of a flight control surface have direct effects on how quickly an aircraft change attitudes in all axes. These structures are small. In your post 188 page 13, they are much smaller compare to the horizontal stabs on the -57, even accounting for photographic scaling and perspective. We can go out on a limb, for entertainment's sake, and speculate that the Checkmate would be for medium down to low altitudes.

Here are the generally accepted values:

Very Low: < 500
Low: > 500 but < 5000
Med: > 5000 but < 25000
High: > 25000

When I was on the F-111, sometimes we go VL TFR and if there is any FLCS error, there is no room for recovery. For the F-111, TFR emergency auto pitch up by the FLCC is the only life saving maneuver, so any other man-made action on the sticks, the EF have only one stick, the surface deflection would be enough to send the jet into departure. So when TFR is engaged, both pilots spread their knees and move hands away from center, and trust their lives to the FLCS.

Finally, still assuming these are flight control structures equivalent to horizontal stabs, we can assume their locations are for low radar observable reasons. We have two less structures protruding into the radar stream.
 

Gomig-21

SENIOR MEMBER
Oct 16, 2016
5,470
11
10,373
Country
Egypt
Location
United States
Yes, post 218 made a credible argument that those structures are flight control surfaces.
Take a look at the edges on those surfaces. They make you think a little because they're about 3 inches thick all around. Any movable surface such as an H-stab, aileron, flap, leading edge flap and even rudder all have a sharply tapered trailing edge. These things are about as thick as they could make them which seems a bit strange? If they function on the same premise as the LEVCONs on the Su-57, even those are tapered super sharp at the leading edge (leading edge since they face forward). Even on canards which face rearwards, they all have sharp, trailing edges but not on the Checkmate with these little and interesting surfaces. So it's interesting that they made them that thick and how effective will they be like that. There is an aerodynamic reason why movable surfaces taper sharp at the trailing edge, they're more efficient at manipulating the airflow to the benefit of the aircraft.

Should be as sharp as the vertical base section to the left of it.
1627162508036.png


The more forward the CG, the more the aircraft move towards DYNAMIC INSTABILITY. Not the same as 'relaxed static stability' (RSS). The CG is affected by arbitrary load distribution on the longitudinal aspect, from one flight to the next. That is not RSS which is from design and the CG would be more towards aft of the fuselage. At this early point, we simply cannot know from pictures where is the Checkmate's CG.

The CG also affects maneuvering stability and here is an interesting factoid from Boeing...

fo01
Maneuvering stability, like static stability, is influenced by CG location. However, when the CG is aft and near the neutral point, then altitude also has a significant effect. Since air density has a notable impact on the damping moment of the horizontal tail, higher pitch rates will result for the same elevator deflections as altitude increases. From the flight crew's perspective, as altitude increases, a pull force will result in a larger change in pitch angle, which translates into an increasing angle of attack and g. While a well-designed flight control system, either mechanical or electronic, will reduce the variation of stick force with CG and altitude, it is very difficult to completely eliminate the variation due to design limitations.We can safely assume that the Checkmate will be RSS-ed and FBW-ed.
Good read. Looking at most new designs and not even mostly new, if we go back to the legacy F/A-18 Hornet and on, it's not hard to notice that most wing structures have been pushed aft as much as possible to the fuselage and hence, to the CG. You can see it on all the new, 5th gen LO aircraft from the US built ones to the Russian Su-57 and this Checkmate. It's clearly visible on the F-35 in all 3 models more so on the C as the wings are bigger and by shoving them backwards, they had to cut into the plain of the H-stabs. The same thing happened on the Su-57 where the wings are pushed so far back that they had to make a considerable notch in the wings to make room for the H-stabs' leading edge to blend into the fuselage. I suppose this also benefits the aircraft in other ways like lift, in general, since now the wing surface has practically combined with the H-stab surfaces to make for a much larger square foot area, hence more lift. It just seems like that would be either an unintended or quite possibly an intended result for the wing's push-back.

Either way, the result favors the moving surfaces in the H-stabs and the ailerons since they also push them back further from the CG, giving them more authority when used. This is most likely where the Checkmate's design comes in handy as they've taken that concept and used it to their advantage in eliminating the need for H-stabs.

Here's a cool overlay of the Checkmate and the F-35C, where you can see how its H-stabs cut into the wing's trailing edge as it meets the fuselage as well as how the wings on both aircraft are pushed aft quite a bit. At the same time, it's clear the V-stabs on the Checkmate are angled steeper than the F-35s'. Most likely making up for the lack of H-stabs.

1627169226386.png


We know that there is an inverse relationship between air density and altitude. The greater the air density, the lower the altitude. The lower the air density, the higher the altitude. Simply put: thicker and thinner air. Flight controls and engines of all types prefers thicker air which mean any aircraft would maneuver best at lower altitudes.

Air density is a calculated value from the Central Air Data Comp (CADC) and fed to the FLCC which calculate the surface deflections. So a stab pitch up deflection at Angels Five will have lesser degree than at Angels Ten, and lesser than at Angels Twenty.

If we assume that those relatively smaller structures in post 218 are flight controls structures equivalent to larger horizontal stabs, using an F-16 as reference for now, those smaller structures will have to deflect more than expected at all altitudes to make the same pitch up maneuver. The areal size of a flight control surface have direct effects on how quickly an aircraft change attitudes in all axes. These structures are small. In your post 188 page 13, they are much smaller compare to the horizontal stabs on the -57, even accounting for photographic scaling and perspective. We can go out on a limb, for entertainment's sake, and speculate that the Checkmate would be for medium down to low altitudes.

Here are the generally accepted values:

Very Low: < 500
Low: > 500 but < 5000
Med: > 5000 but < 25000
High: > 25000
I'm trying to think if the air density is a reason why they designed those with the thick trailing edges but it doesn't make sense, unless the material is all composite and doesn't have the required strength to be used in that way, but that doesn't even add up. Perhaps it's because of the eventual TVC and the thicker they are, the more resistant they'll be to the heat blasting from the directional nozzle.
 
Last edited:

Users Who Are Viewing This Thread (Total: 1, Members: 0, Guests: 1)


Top Bottom