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What’s everybody else’s thoughts on the spin characteristics or even just the stalling for the MiG 15?

 

I did some testing before and the stall seems really benign, very little tendency to wingdrop. With low speed, full rudder, full rear elevator and even ongoing use of aileron after the stall, the aircraft barely spins. Once it is in the spin it must be held in the spin, letting go of the controls results in the aircraft recovering itself in only about 2 revolutions.

 

This doesn’t seem consistent with the real MiGs reputation.

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I concur that the deadly spin and stall characteristics that we read so much about in the primary source material are not modeled in DCS MiG-15. It is very stable at slow speed regimes, in fact, that's where the majority of MiG players prefer to fight PvP. The literature I've come across seems to suggest a MiG would not want to get low and slow precisely because of the unpredictable stall characteristics. In real life, the MiG-15bis also had an airbrake that automatically deployed at .92-.95 mach, and that is also not modeled correctly.

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Can you name some sources?

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1. This is from Sabre v. MiG-15 by Warren Thompson and Thomas Dildey, published by Osprey in 2014 and is mostly related to the Initial design compromises/considerations of the MiG-15: 

 

While the top speed of the two jets seemed equally matched, at high altitudes it is Mach that counts, and the MiG-15 suffered from a relatively low critical Mach number (VNE) of 0.92. Above this speed directional stability deteriorated markedly, resulting in yawing (“snaking”) from side to side – something the jet’s unboosted rudder could not correct. Even the hydraulically boosted ailerons were hard to actuate at high speeds, taking both hands to move (as if the stick was “stuck in cement”), and resulting in an excruciatingly slow roll rate. Most critically, because of the MiG-15’s light construction and poor quality control at the various assembly plants building the aircraft, the wings rarely matched! And near critical Mach, they tended to “warp” due to insufficient stiffness and inconsistent sonic wave attachments, resulting in sudden uncommanded rolling moments (called valezhka, or “wing drop”) that could only be controlled by slowing down.
 

Additionally, above 0.92M, the unboosted elevators experienced control reversal due to sonic wave attachment to the tailplane surface, dramatically changing its control dynamics. Frequently, this would cause sharp pitch-up moments if any “back stick” was applied to pull out of high-speed dives or to initiate a defensive turn. Many times – in at least 56 cases documented during combat – the MiG was seen to “depart controlled flight”, the aircraft pitching up violently into a high speed stall and the yawing moment causing it to “swap ends” and snap into a spin. These were frequently unrecoverable, resulting in the loss of 40 aircraft. In numerous other instances the sharp pitch-up would cause an “over-G” in which G-forces in excess of those for which the airframe was stressed would bend and distort the empennage – some were even seen to shed wings or tail assemblies.

This issue became so critical that the MiG-15bis was soon retrofitted with a new Mach indicator – the M-0.92 – that had an automatic trigger deploying the speedbrakes at 0.92M to slow the jet to below “red line” so that it would not “self-destruct”. In the interim, the early MiG-15s were limited by a flight manual restriction to 1,100km/h (683.5mph).

In high altitude maneuvering at slower speeds the MiG had a noticeable turning advantage over the Sabre. The lighter wing loadings of the early MiG-15 gave it a tighter, faster turn and the more powerful VK-1A engine of the MiG-15bis ensured that the later model could sustain its turn longer, losing less altitude, and was able to zoom and power its way back up, out of reach, to heights beyond the Sabre’s ceiling.

 

However, once below 30,000ft (9,144m), if the MiG pilot turned so aggressively that he shed airspeed, the Sabre’s leading edge slats provided a great advantage. In a turning fight below 330mph IAS (530km/h) the MiG pilot was doomed.


Wolf's Note: This is specifically in comparison with the  A-5 which had slats, rather than the fixed 6-3 wing we have modeled in DCS. 


MiG-15 design

This combination resulted in significant “spanwise flow”, where the air is deflected outwards towards the wingtip, thus reducing lift, decreasing aileron effectiveness and causing premature stall at the wingtip. Consequently, two tall, full chord “wing fences” were needed to keep the airflow going parallel to the longitudinal axis of the aircraft.

The horizontal stabilizer was swept 40 degrees, and being structurally difficult to fit atop the fin, it was set two-thirds up the vertical stabilizer and mounted as far aft as possible. This was to provide the greatest possible pitching moment (for pulling G and turning tightly) so that the fighter was as maneuverable as possible for air-to-air combat.

The prototype – designated I-310 (serial S-01) – was first flown on December 30, 1947 by V. N. Yuganov, and not surprisingly it was found to be “generally satisfactory, but pulling too much G caused a sudden flick into a spin [due to limited yaw stability/ control] and there were problems with yaw and roll”. Additionally, the deep-set cockpit – done to minimize the height, size and resultant form drag from the low-profile bubble canopy – resulted in very poor forward visibility at slow speeds, such as on final approach for landing.


2. This is from an interview with Vladimir Zabelin, who was credited with 9 kills and the Order of Lenin during the Korean War describing tactics: 

 

— You said that you shot all your planes in horizontal maneuvers?

When I talked to the pilot of the division that replaced us, if I remember correctly it was 97th Division from Baku (97th IAD returned to the USSR simultaneously with the pilots of ther 190th IAD, therefore it was 216th IAD that arrived from Baku in August 1952. I. Seidov), I told them:
— However strange it may be, I shot them down in horizontal maneuvers.
But what was it exactly? There is no way to make me fight them in sustained turns. Then he easily would have made it to my tail. When I made it to their tails, they knew that their only escape was in horizontal maneuvers. Everybody knew that this type of maneuvers was much better in Sabres than in MiGs, and the Americans used it very often. Another choice for them was to make a half roll and go straight down – the MiG couldn’t catch them. I knew that they were going to use these maneuvers and waited for them to initiate. I usually chased them from behind and a bit below. Their rear-looking radar identified us at a distance of about 2 kilometers. It warned the pilot of our presence in his rear sphere, and I almost felt that he was going to start turning. There was no other option for him. When he began to roll, I tried to intercept him. If I did not shoot him down during his first 1\3 of a turn, I had to abort the attack and zoom away.
http://www.airforce.ru/history/cold_war/zabelin/chapter5_en.htm

 

 

I will post more later, but if you spend a significant amount of time in DCS PvP with MiG and Sabre, you will see that MiGs love fighting Sabres in sustained turns because on doghouse charts, the MiG-15bis has an advantage over the F-86F-35. However, as you can see above, this is precisely the opposite of the approach taken by accomplished Soviet MiG-15bis pilots.  In the words of Zabelin, this is something that "everybody knew."


Edited by Wolf_ofthe_North
Had more to say about PvP disparity in DCS and real life
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I'm bored so I'll continue.

3: https://www.aopa.org/news-and-media/all-news/2013/april/04/mig-15-flying-the-enemy-fighter
 

Quote

The aircraft is less responsive and difficult to handle at low airspeeds, I learn during a slow flight maneuver. After I make gentle turns at 140 knots, Salganek takes the controls for a moment, deflecting the stick full left and full right. The MiG just wallows, barely rolling a few degrees. I try it myself with the same results. Even with two stall fences on each wing, the ailerons are ineffective at slow airspeeds (A third row was added to the MiG-17, which considerably helped the low-speed handling characteristics, Salganek says.). It’s an eye opener of what to expect on final approach to landing 10 knots slower at 130 knots. (I can also see why it can’t handle more than a 20-knot crosswind.)
 

Slowing to 120 knots, I stall the aircraft. It usually breaks to the left, Salganek says, but this time the right wing drops. Bring the throttle full forward, slightly lower the nose to recover. It takes a while for the turbojet to accelerate after operating at low power settings, but after my airspeed increases to 160 knots, Salganek raises the flaps. It will feel “as if the bottom has dropped out from underneath you, but it hasn’t,” he says. It feels as if I’m falling tail first toward the earth, but the aircraft hasn’t sunk. “The rate of climb stopped for momentarily,” Salganek explains, noting that the altimeter never decreased.
 

At the opposite end of the speed spectrum, the MiG performs beautifully.

 

4. This is a video summary of Operation Moolah which offers contradictory evidence: 

 

At 9:05: "The MiG is most effective as a combat fighter at lower speeds, where its lower thrust-loading allows greater manuverability [than at higher speeds]."
The study included the following relevant desirables: 
2. High rate of climb
3. Rapid acceleration from low speeds

4. Short turning radius 

Operation Moolah also indicated the following undesirable characteristics: 
1. Uncontrolability at high mach number
2. Poor rearward visibility
3. Poor lateral directional stability at high altitudes
4. Slow rate of roll. 

5. Equipment requires constant pilot attention. 

Notice that poor stalling characteristics did NOT make it onto Moolah's list. 
Contradicts my main point, but hey, we have to stay honest. 



5. United States Air Force Operations in the Korean Conflict 1952-1953 (declassified)
https://www.afhra.af.mil/Portals/16/documents/Studies/101-150/AFD-090529-031.pdf

 

p. 56/101 "The MiG was unstable at high altitudes and at high speeds. 
p. 60/101 "[F86-E] Sabres demonstrated the ability to out-turn the MiG at altitudes below 30,000ft."
p. 61 "There were a good many pilot reports that the MIG was unstable at high speeds, subject to unintentional spins, especially at altitudes above 35,000ft, and very difficult to bring out of a spin. During 1951-52, 32 instances were reported in which a MiG was observed to go into a spin for causes other than battle damage. In a shorter but more intensely studied period between September 1952 and April 1953, there were 24 instances of MiG spins--12 of which were assessed as accidental and 11 of which resulted in losses to the enemy. In the first half of May 1953 when there were seven incidents in which the MiGs went into inadvertent spins from manuevers at or above 35,000ft, and in most instances, the pilot immediately ejected." 

6. "The Jet that Shocked the West" Air & Space Magazine, Dec. 2013, p. 2: 

 

Quote

With the MiG challenging U.S. air superiority, Americans worked hard to get their hands on the Soviet technology, but they wouldn’t obtain a flyable MiG-15 until September 1953, when defecting North Korean pilot No Kum-Sok landed his jet at Kimpo Air Base, South Korea. Flying the Korean MiG would fully reveal what U.S. pilots were up against. To evaluate the Soviet fighter, the best of the U.S. Air Force test pilots—Captain Harold “Tom” Collins of the Wright Field Flight Test Division and Major Charles “Chuck” Yeager—were sent to Kadena Air Base, Japan. On September 29, 1953, the first Western pilot took to the sky in the mysterious MiG. The flight revealed the expected formidable performance, but also the MiG’s more unpleasant characteristics. “The defector pilot told me that the MiG-15 airplane had a strong tendency to spin out of accelerated, or even one ‘G,’ stalls and, often, it did not recover from the spin,” said Collins in 1991 for Test Flying at Old Wright Field, a collection of memoirs. “A white stripe was painted vertically down the instrument panel to be used to center the control stick when attempting spin recovery. He said that he had seen his instructor spin-in and killed.”
 

The flight tests revealed that the MiG’s speed was limited to .92 Mach. Above that, the aircraft’s flight controls were ineffective in dives or tight turns. During air-to-air combat in Korea, U.S. pilots witnessed MiG‑15s that were flirting with design limits suddenly enter dramatic, high-speed stalls, then snap end over end, frequently losing wings or tails.

 


 

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The uncommanded roll is modeled. It's mentioned in the DCS MiG-15 Manual, section 9.1.5. However this is not present in the AI aircraft as they use the simple flight model.

From the Manual.

"The DCS: MiG-15bis model features a randomized wing rigidity calculation. As such, the specific airspeed, at which uncommanded roll occurs, and its intensity depend on flight conditions, however the direction of the roll condition (left or right) is randomized with each aircraft "spawn".

 

"Uncommanded roll can occur at high flight speeds throughout the altitude envelope. At altitudes below 4000 m, this can occur at TAS greater than 1070- 1090 km/h (small needle on the airspeed indicator). As altitude increases, the true airspeed, at which uncommanded roll can occur, decreases. At altitudes above 11000 m, the true airspeed, at which uncommanded roll can occur, stabilizes in the 1010 - 1090 km/h range."

 

"Applying opposite pedal during uncommanded roll at speeds of Mach 0.86 and greater in an attempt to correct the effect can lead to increased roll rate and significant lateral stick force. Roll can be reduced in this case by carefully applying pedal in the direction of the roll. For example, if uncommanded roll is to the left, apply slight left pedal or if uncommanded roll is to the right, apply slight right pedal. "

 

The go to source for aerodynamic data on the MiG-15 seems to be. МиГ-15бис. Техническое описание. Книга I.

https://www.digitalcombatsimulator.com/en/files/2365583/

It does show a loss of alieron effectiveness at high mach high angle of attack situations. image.png

image.png

 

At Mach .86 at 15 degrees of AOA the ailerons alone can not counter act the roll tendency. Some rudder would be needed.  Just like the DCS manual says

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Sorry if my rambling through the primary source material added to the confusion, so I'll try to be more specific here: 

 

1. The MiG-15bis had problems with both uncontrolled spin and roll. 

2. It had an automatic airbrake that deployed at .92mach to deal with uncontrolled roll. 

3. Uncontrolled spin is a different animal. I've attached an image which shows how the MiG design bureau tried to test the airframe and alleviate the spin problems. I'll quote the inset which is taken from Foxbatfiles.com: 

"MiG I-310 prototype S-02 during its V-VS Scientific Research Institute flight trials in late 1948. The black cannisters beneath the wings are "anti-spin" rockets used to help the pilot recover from spins. This aircraft and its pilot, S. Bogdanov, were lost when it failed to recover from a test spin. (FoxbatFiles.com)" Sabre v. MiG, p. 16. Osprey Publishing 2014. 

Matters are not aided by the fact that pilots of this era seem to use the terms equivocally. From Kramarenko's Air Combat Over the Easter Front and Korea, p.145 Pen and Sword 2008: [The sabres] flipped and went into a dive, and transmitting to Goglev (the third pair leader): "Cover the commander!" I followed them. Seeing that a Sabre was diving doggedly at an angle of nearly 60 degrees, I aimed and shot off a burst. The shells exploded around his cockpit area and I clearly saw a smoky cloud above it. The Sabre increased its diving angle and dropped away, but at this moment Goulyy transmitted: "I'm spinning!" I look back and see his plane nearly upside down. I order: "Let out the brakes and pull out of it!" I see Goulyy pull his plane out of its overturned attitude and then we leave off diving, climb to one side, and come back again..."

p.  133: "The Sabres, not expecting this, find themselves above me but far behind, and begin chasing me. What to do? Climbing is not an option: the Sabres [because they are higher] will close quickly and open fire. I keep descending at a maximum speed but at a height of about 7,000 meters (my speed was more than 1,000 km/hour) the plane begins to spin. The control levers don't work. I bring the speed down a bit by using the airbrakes: the plane straightens out but the Sabres exploit my reduction in speed and close in fast."

 

Wolf's note: I believe in both instances Kramarenko is describing wing-drop but in neither instance did the planes enter an accelerated stall. 

 

See also Zabelin interview: 

— Could you compare the Sabre and the MiG. I know that there was a high speed problem – valezka (wingdropping).

Yes. Weak wing. You should expect it as you passed 900 kilometers per hour. A lot of pilots were killed by it, but I wasn’t afraid – it was sufficient to give opposite rudder. Then you had to reduce throttle. 

 


But the source material seems to suggest these may be two different but related phenomenon: Sabre v. MiG p. 25: 

 

1. Wing Drop/Valezkha/Uncontrolled Roll

 

While the top speed of the two jets seemed equally matched, at high altitudes it is Mach that counts, and the MiG-15 suffered from a relatively low critical Mach number (VNE) of 0.92. Above this speed directional stability deteriorated markedly, resulting in yawing (“snaking”) from side to side – something the jet’s unboosted rudder could not correct. Even the hydraulically boosted ailerons were hard to actuate at high speeds, taking both hands to move (as if the stick was “stuck in cement”), and resulting in an excruciatingly slow roll rate. Most critically, because of the MiG-15’s light construction and poor quality control at the various assembly plants building the aircraft, the wings rarely matched! And near critical Mach, they tended to “warp” due to insufficient stiffness and inconsistent sonic wave attachments, resulting in sudden uncommanded rolling moments (called valezhka, or “wing drop”) that could only be controlled by slowing down.

 

2. Snaking, yawing, sudden departure from controlled flight causing unrecoverable spins: 

 

Additionally, above 0.92M, the unboosted elevators experienced control reversal due to sonic wave attachment to the tailplane surface, dramatically changing its control dynamics. Frequently, this would cause sharp pitch-up moments if any “back stick” was applied to pull out of high-speed dives or to initiate a defensive turn. Many times – in at least 56 cases documented during combat – the MiG was seen to “depart controlled flight”, the aircraft pitching up violently into a high speed stall and the yawing moment causing it to “swap ends” and snap into a spin. These were frequently unrecoverable, resulting in the loss of 40 aircraft. In numerous other instances the sharp pitch-up would cause an “over-G” in which G-forces in excess of those for which the airframe was stressed would bend and distort the empennage – some were even seen to shed wings or tail assemblies.

Thus I believe there should be two ways to produce the MiG-15bis' historically dangerous spin characteristics: 1. ignore the wing drop effect until you enter a spin 2. apply too much back-stick at high speeds. If I may, I believe the following short youtube clip is illustrative: You're going to see the plane enter an accelerated stall on the left wing. This is most closely related to the wing-drop phenomenon. (Annoying, ok, but recoverable.) But then you're going to see the plane REALLY spin, and my primary argument is that this is not modeled correctly in the DCS MiG-15bis as is. You're not surviving that by deploying airbrakes and reducing throttle because the Bis did not have boosted elevators or rudder, just ailerons. 

I could be wrong but I think it's an interesting topic to discuss. 

 


 

Screen Shot 2021-08-03 at 7.29.38 PM.png


Edited by Wolf_ofthe_North
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2 hours ago, Ziggy123 said:

Am I correct I thinking the DCS MiG15 does not have air brakes that automatically deploy at 0.92 M ?

 

You are correct

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There two drivers of the MiG 15's characteristics.  The handling qualities and the basic aerodynamics. The Soviet Technical Manual for the MiG 15, linked above, notes some interesting handling qualities.  Aspects of the handling qualities could make the aircraft dangerous for poorly trained pilots, who might be unaware of it's quirks.  

 

In the high transonic regime. Roll and pitch handling qualities change quite dramatically. 

 

At mach .82 alieron effectiveness drops rapidly to zero at mach .85. They then enter an area of reverse command until mach .95

image.png

Stability issues are noted above Mach .92. However they can be counteracted by ~5 degrees of alieron.

 

image.png

 

Also, as mach increase the force to command more g increase above mach .86

 

image.png

image.png

Notably the amount of elevator per G required reduces from mach .72 to mach .88. 

 

Aerodynamically the MiG 15 is pretty well designed. The designers went to a fair bit of trouble to ensure the aircraft was stable and paid some performance penalties to do so. To compensate for the roll stability, the wing was given anhedral, angled down. This done to increase the roll rate of laterally stable aircraft.  However, anhedral lowers the lift a wing generates. As the lift is a function of the cosine of the dihedreal angle ^2 times the angle of attack and the lift curve slope of the airfoil.

image.png

 

The wing fences  reduce spanwise flow as the angle of attack increases. This prevents the wing tips from stalling before the root. Which prevents adverse yaw at high angles of attack. It also increase alieron effectiveness at high angles of attack. This makes the aircraft much more stable and safe. However the fences reduce the over Cl max of the wing.  The result was an aircraft that was not prone to spinning at high angles off attack.  To get the aircraft to spin you have to apply opposing alieron and rudder inputs.

just like in DCS.

Lets go back to alieron handling and see how this could get deadly fast. First, entering high angles above mach .86 may cause the aircraft to spin, as uncommaned roll begins to occur. At the same time ailerons lose effectiveness and reverse at high mach.  If you try and oppose inadvertent roll with alieron and rudder inputs, you are now inputting the only control combination which spins the jet. Which is why the spin and roll correction techniques call for stick neutral. 

 

The version of F-86 in DCS is also not without it's handling issues either. DCS models the non- slatted F-86 F with the "6-3" wing. The 6-3 wing was designed to increase the maximum lift coefficient of the aircraft while reducing the drag. However this version of the wing was noted for a rapid reduction in lift and being longitudinally unstable post stall. 

https://ntrs.nasa.gov/citations/19930087007

 

image.png

image.png

evidenced of this instability is noted in the pilots manual too.

Screenshot 2021-08-06 at 18-06-06 Avialogs Aviation Library - T O 1F-86F-1 Flight Manual F-86F.png

Screenshot 2021-08-06 at 20-18-58 Avialogs Aviation Library - T O 1F-86F-1 Flight Manual F-86F.png

The 6-3 wing, without slats, also tended to roll at the stall. The small fence installed on the wing was an attempt to elevate this issue.image.png

https://ntrs.nasa.gov/citations/19930087699

 

However the fence also reduced Cl max of the aircraft from ~1.4 to ~1.2.

image.png

https://hdl.handle.net/2027/mdp.39015086432781?urlappend=%3Bseq=8

 

The slatted version of the 6-3 wing  gave the Sabre a higher Cl max than fenced non slatted, A gentler stall and reduced rolling tendencies at the stall. Which is why Sabre went to a slatted 6-3 wing.

image.png

https://ntrs.nasa.gov/api/citations/19930089460/downloads/19930089460.pdf

 

The  F-86's pilots manual also seems to indicate this also reduced the stability issues.

Screenshot 2021-08-06 at 20-18-58 Avialogs Aviation Library - T O 1F-86F-1 Flight Manual F-86F.png


Edited by Curly
Anhedral, Dihedral fix.
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  • 4 weeks later...
On 8/4/2021 at 3:05 AM, Wolf_ofthe_North said:

Sorry if my rambling through the primary source material added to the confusion, so I'll try to be more specific here: 

 

1. The MiG-15bis had problems with both uncontrolled spin and roll. 

2. It had an automatic airbrake that deployed at .92mach to deal with uncontrolled roll. 

3. Uncontrolled spin is a different animal. I've attached an image which shows how the MiG design bureau tried to test the airframe and alleviate the spin problems. I'll quote the inset which is taken from Foxbatfiles.com: 

"MiG I-310 prototype S-02 during its V-VS Scientific Research Institute flight trials in late 1948. The black cannisters beneath the wings are "anti-spin" rockets used to help the pilot recover from spins. This aircraft and its pilot, S. Bogdanov, were lost when it failed to recover from a test spin. (FoxbatFiles.com)" Sabre v. MiG, p. 16. Osprey Publishing 2014. 

Matters are not aided by the fact that pilots of this era seem to use the terms equivocally. From Kramarenko's Air Combat Over the Easter Front and Korea, p.145 Pen and Sword 2008: [The sabres] flipped and went into a dive, and transmitting to Goglev (the third pair leader): "Cover the commander!" I followed them. Seeing that a Sabre was diving doggedly at an angle of nearly 60 degrees, I aimed and shot off a burst. The shells exploded around his cockpit area and I clearly saw a smoky cloud above it. The Sabre increased its diving angle and dropped away, but at this moment Goulyy transmitted: "I'm spinning!" I look back and see his plane nearly upside down. I order: "Let out the brakes and pull out of it!" I see Goulyy pull his plane out of its overturned attitude and then we leave off diving, climb to one side, and come back again..."

p.  133: "The Sabres, not expecting this, find themselves above me but far behind, and begin chasing me. What to do? Climbing is not an option: the Sabres [because they are higher] will close quickly and open fire. I keep descending at a maximum speed but at a height of about 7,000 meters (my speed was more than 1,000 km/hour) the plane begins to spin. The control levers don't work. I bring the speed down a bit by using the airbrakes: the plane straightens out but the Sabres exploit my reduction in speed and close in fast."

 

Wolf's note: I believe in both instances Kramarenko is describing wing-drop but in neither instance did the planes enter an accelerated stall. 

 

See also Zabelin interview: 

— Could you compare the Sabre and the MiG. I know that there was a high speed problem – valezka (wingdropping).

Yes. Weak wing. You should expect it as you passed 900 kilometers per hour. A lot of pilots were killed by it, but I wasn’t afraid – it was sufficient to give opposite rudder. Then you had to reduce throttle. 

 


But the source material seems to suggest these may be two different but related phenomenon: Sabre v. MiG p. 25: 

 

1. Wing Drop/Valezkha/Uncontrolled Roll

 

While the top speed of the two jets seemed equally matched, at high altitudes it is Mach that counts, and the MiG-15 suffered from a relatively low critical Mach number (VNE) of 0.92. Above this speed directional stability deteriorated markedly, resulting in yawing (“snaking”) from side to side – something the jet’s unboosted rudder could not correct. Even the hydraulically boosted ailerons were hard to actuate at high speeds, taking both hands to move (as if the stick was “stuck in cement”), and resulting in an excruciatingly slow roll rate. Most critically, because of the MiG-15’s light construction and poor quality control at the various assembly plants building the aircraft, the wings rarely matched! And near critical Mach, they tended to “warp” due to insufficient stiffness and inconsistent sonic wave attachments, resulting in sudden uncommanded rolling moments (called valezhka, or “wing drop”) that could only be controlled by slowing down.

 

2. Snaking, yawing, sudden departure from controlled flight causing unrecoverable spins: 

 

Additionally, above 0.92M, the unboosted elevators experienced control reversal due to sonic wave attachment to the tailplane surface, dramatically changing its control dynamics. Frequently, this would cause sharp pitch-up moments if any “back stick” was applied to pull out of high-speed dives or to initiate a defensive turn. Many times – in at least 56 cases documented during combat – the MiG was seen to “depart controlled flight”, the aircraft pitching up violently into a high speed stall and the yawing moment causing it to “swap ends” and snap into a spin. These were frequently unrecoverable, resulting in the loss of 40 aircraft. In numerous other instances the sharp pitch-up would cause an “over-G” in which G-forces in excess of those for which the airframe was stressed would bend and distort the empennage – some were even seen to shed wings or tail assemblies.

Thus I believe there should be two ways to produce the MiG-15bis' historically dangerous spin characteristics: 1. ignore the wing drop effect until you enter a spin 2. apply too much back-stick at high speeds. If I may, I believe the following short youtube clip is illustrative: You're going to see the plane enter an accelerated stall on the left wing. This is most closely related to the wing-drop phenomenon. (Annoying, ok, but recoverable.) But then you're going to see the plane REALLY spin, and my primary argument is that this is not modeled correctly in the DCS MiG-15bis as is. You're not surviving that by deploying airbrakes and reducing throttle because the Bis did not have boosted elevators or rudder, just ailerons. 

I could be wrong but I think it's an interesting topic to discuss. 

 


 

Screen Shot 2021-08-03 at 7.29.38 PM.png

 

From what I´ve gathered on different sources including the Mig15bis manual, the airbrake would automatically deploy in the later versions of the mig 15bis (post summer 1952) only below 5000m of altitude. This was where the high speed uncommanded roll was notably dangerous. At high altitude, the mig 15 pilots overcame the issues at high mach numbers using aileron reversal with rudder imputs as curly pointed out, in the same direction of the roll. This is modeled in DCS very well. when you get to mach 0.95 mig starts vibrate heavily just as indicated in the manual and different sources.

 

I was asking myself this question not along ago, how the hell did mig pilots score kills on sabres if the sabres were above mach 0.9?

 

As for the spins I´m not so sure either. All of the sources I´ve read on the spins are from western ones mostly regarding the test pilots comments following the mig 15bis defection. I too have the feeling  that it is too easy get out of one. On one hand it´s a sim and modeling has limitations. On the other... a lot of simmers spend a lot more hours perfecting out skills than the actual pilots had in real life. After not flying for a couple months came back in the mig and got myself into a nasty spin and wouldn´t have pulled out if i had been at 1000m. So to me it´s probably a combination of the two and I don´t thinkg the mig was that much more dangerous in spins than other aircraft.

 

Kong.

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