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  1. The gun heating due bullets fired model is incorrect. TLDR Version: The gun heating model has the wrong barrel and body mass. Resulting in a rapid rise in gun temps. The mass of the barrel in the game is 2.7 Kg. The mass of the real gun barrel is 10.6Lbs or 4.8kg. The mass of the body in the game is 14.3 Kg. The mass of the real gun minus the barrel is 58.09 lbs or 26.34 Kg There is too much heat per shot. The thermal energy input into the guns in the game is 7.823 Joules per bullet. Tests indicate the variable “shot_heat” should be from 4.62 to 4.023 Joules per bullet. The reduction in accuracy and velocity due to gun heating are too large. Tests of the Real gun barrel indicate that a burst of 365 bullets can be fired without a reduction in accuracy or muzzle velocity. And, that the accuracy and velocity life of the M3 gun barrels are 8 times greater than that of the regular steel barrels. https://www.loc.gov/resource/dcmsiabooks.hypervelocitygun01bush/?sp=499 An accurate model for gun heating would look like: { name = "HeatEffectExt" , shot_heat = 4.62, barrel_k = 0.462 * 4.94, body_k = 0.462 * 26.34 }, With a 20% reduction in accuracy and reduction in muzzle velocity 200 fps being applied at a barrel Temperature of 800c or the equivalent of 350 consecutive shots. Having the guns fire uncontrolled ( a Cook Off model) after a 200 round burst or a body temperature of 900 C would be realistic too. For comparison the current gun heat model in the code is: { name = "HeatEffectExt" , shot_heat = 7.823, barrel_k = 0.462 * 2.7, body_k = 0.462 * 14.3 }, Elsewhere in the code, the values of gun heating model are explained for the 50 cal M2: function M2_heat_effect() --[[ 7.823 kJ - one shot energy , 462 (steel specific heat), 6 kg - barrels mass ]] { name = "HeatEffectExt", shot_heat = 7.823, barrel_k = 0.462 * 6.0, body_k = 0.462 * 32.0} The heat effect model contains 3 variables which describe the thermal dynamics of the gun. The First variable is,. shot_heat = 7.823, This energy input into per bullet fired. It’s set to 7.823 Joules per bullet fired. The variables barrel_k and body_k are the thermal capacity of the gun barrel and body. This variable consists of two numbers: the specific heat of the material and its mass. For the F-86 Barrel, the thermal capacity is, barrel_k = 0.462 * 2.7 .426 is the specific heat of steel and 2.7 is the mass of the DCS F-86’s gun barrel. The specific heat of a material is the energy, in joules, required to raise the temperature of a kilogram of that material, by 1 degree C.The specific heat of steel is.462 joules per gram. Therefore, the energy (Joules) required to raise the temperature of the gun barrel 1 degree C is Joules Need to raise temp by 1c = mass of material * the specific heat of the material. 1.2474 =2.7*.462 Since the code gives the heat input per bullet, 7.823 Joules, we can compute the change in barrel temp after 1 shot is fired. As the change in temp is = (Joules per Shot * Number of bullets fired) / (the specific heating of steel * the barrel Mass) In terms of the Gun heat variables the change in barrel temp = (shot_heat = 7.823 * the number of shots) / (barrel_k = 0.462 * 2.7) For one bullet the temperature of the guns increase by 6.27C 7.823/(0.462 * 2.7)= 6.271C The code tells us, The DCS F-86 is modeling a barrel with a mass of 2.7 kg which is about 5 lbs. The manual for the 50 Cal M3 machine gun. . https://www.scribd.com/document/38654349/TM-9-2190-M3-Browning Notes, the barrel weight is 10.91 lbs which is 4.94 kg. The DCS M3 machine gun barrel has half as much mass as the real one. It seems trivial, but the reduced mass has important implications due to the heat modeling. If we model the gun with the correct barrel mass; the gun temperature increases 3.47C per shot. 7.823/(0.462 * 4.94) = 3.4377C. This is just about half as much heat as is currently modeled 6.7C per shot. The code shows the weight of the body of the gun as 14.3 Kg which is also incorrect. body_k = 0.462 * 14.3 The weight of the gun body in DCS is 14.3 Kg or 31.5 Lbs, The M3 manual gives the weight of total Gun as 64 1/2 lbs + 4 1/2 lbs for the recoil adapter. So 69 lbs total. The total mass - barrel should give us the “body mass” 69-10.91. Or 58.09 lbs / 26.34 Kg. Again about half the mass of the actual gun is in the thermal model. So the body of the gun heats up twice as much as it should too. In DCS, the temperature of the gun body increases 1.184C for every shot. 7.823/(0.462 * 14.3) = 1.184C increase in temp If we model the gun with real weight - barrel. The temperature of the body increases by .6428 C 7.823/(0.462 * 26.34) = .6428c. With the correct body weight that shot per heat is reduced by half. If you’re ready for a deep dive on the metallurgy and performance of 50 caliber gun barrels, read on. We’re going to compare the heat modeling of the DCS M3 to some real tests.The tests indicate that the loss of accuracy and the drop in muzzle velocity as a result of barrel heat are too high in the DCS F-86. The construction of the gun barrel used on the M3 machine gun is different from a standard steel barrel. The properties of the materials used in the barrel of the M3 machine gun increase the number of bullets which can be fired before the accuracy or the muzzle velocity of the gun drops when compared to the plain steel barrel. https://www.loc.gov/resource/dcmsiabooks.hypervelocitygun01bush/?sp=499 This chart shows how many M2 AP bullets can be fired on a severe firing schedule, before the muzzle velocity drops by either 200 fps or 20% of bullets impact yawed. The chart shows that a steel barrel can only fire a single 170 burst. The lined and plated barrels, Which are on the F-86’s machine guns, did a 350 round burst and two 500 round burst cycles, for a total of 1350 bullets before the accuracy of the weapon dropped. The test consisted of an initial burst of 350 rounds. The gun is then allowed to cool to room temperature. After the gun is cooled, a burst of 100 rounds are fired. The gun is allowed to cool for 2 mins and then another 100 round burst is fired. This cycle is repeated until 500 bullets have been fired. After the 500 round burst, the gun is allowed to cool to room temperature. The 500 bullet burst cycle is then repeated until either the muzzle velocity drops by 200 fps or the accuracy is degraded by 20%.The accuracy and muzzle velocity of the gun are measured periodically through the test. The model barrel of the M3 machine gun on the F-86, is the same design as the one tested in the chart. Stellite lined with chromium plating. From the M3 weapons manual. The model of M3 barrel is 7265156 and it has the same type of lining and plating as the barrel tested in the chart. Page 23 of manual notes, the barrel has a 9 inch liner and is plated with chromium. A cross section of the barrel is available in the M3’s weapon’s inspectors manual. https://www.smallarmsreview.com/archive/detail.arc.entry.cfm?arcid=2758 And a color picture of the liner. https://apps.dtic.mil/sti/pdfs/ADA472711.pdf The Manufacturing process of the Stellite / Cobalt liner. The 9 inch liner in the F-86’s gun barrel is made of Stellite 21. An Air National Guard memo regarding the recycling of these barrels and liners verifies this. https://www.google.com/books/edition/National_Guard_Bureau_Bulletin/cYhat3J3bmUC?hl=en&gbpv=1&pg=RA7-PA7&printsec=frontcover Note the same barrel model, 7265156, as indicated in the Manual for the M3 machine gun posted above. The lining and plating of these barrels was developed during World War 2 to improve the accuracy and velocity of the 50 caliber aircraft machine gun. The development, metallurgy, construction and testing of these barrels are discussed in detail in the National Defense Research Committee Report. https://www.loc.gov/item/2007498072/ Let’s look at the 9 inch Stellite line and see how this improves the performance of the M3 machine gun barrel. The 9 inch liner is made of a cobalt alloy called Stellite 21. The Stellite / cobalt liner provides two primary advantages over the plain steel barrel. The cobalt liner has a higher heat hardness and is less prone to chemical erosion than the plain steel barrel. The properties of the Stellite / Cobalt liner reduces wear inside the barrel and keeps the grooves (rifling) in the barrel intact. This increases the velocity life of the weapon. Meaning long bursts can be fired through a Stellite /Cobalt lined gun without a reduction in muzzle velocity. The Stellite / cobalt barrel liner is so effective that it actually increased the muzzle velocity of the weapon. The Stellite / cobalt liner is so effective at preventing a drop in muzzle velocity during burst firing, that the limiting factor for burst length is the reduction in accuracy. Since the F-86’s gun barrels have this type of liner. There should be no drop in muzzle velocity for bursts shorter than 350 bullets. The second benefit of the cobalt / Stellite liner was that it reduced the heat input into the barrel. Which helped to prolong the accuracy life of the weapon. Meaning more bullets could be fired through the barrel before the accuracy drops. A 295 continuous burst could be fired through a Stellite / Cobalt lined barrel compared to 167 from a plain steel barrel, for the same loss in accuracy. This is because the cobalt liner is a worse conductor of heat than plain gun steel. Less thermal energy per second is transferred from the Stellite / Cobalt liner into the gun barrel. The Cobalt / Stellite liner reduces the heat transfer into the barrel per bullet fired when compared to the plain steel barrel. A 350 round burst test, on a 50 cal 36 inch aircraft barrel with just the 9 inch liner. Illustrates how effective the Stellite / cobalt liner is in reducing heat input into the steel barrel. The mean barrel temperature was measured to be 750 C after the firing. If we assume an ambient temp of 20c. The temperature of the barrel rose 730C after a 350 round burst. For a 350 burst, The DCS thermal model for the F-86 gun barrel predicts a temperature increase of 2195c. (7.823* 350) / (0.462 * 2.7) =2195C. That’s 3 times more than the test firing of a barrel the cobalt liner. Based on the test data we can compute the thermal energy input into the barrel per shot for a 50 caliber machine gun with a Stellite / Cobalt liner. In game terms we can find the real value for the variable “shot_heat =” Assuming 20 c ambient temperature. The temperature of the lined barrel increased by 730 degrees. Each shot increases barrel temp 2.0857C. Temperature increase per Shot 730/350 = 2.085714 c per shot The energy input into the barrel per shot works out to: Change in Temp =( Joules per shot *Shots fired) /( Barrel Mass * The Specific Heat of the barrel.) Joules per shot = (Temp * ( Barrel Mass * The Specific Heat of the barrel))/ Number of bullets fired. 730=x*350/4.808*.462 730=350x/2.219 x=(730*2.219)/350 = 4.6282 Joules Per shot Testing of the aircraft barrel shows that the energy input into the barrel with the Stellite / cobalt liner is 4.6282 Joules per bullet. The DCS model adds 7.823 Joules per bullet, 1.69 times more than the testing indicates. The reduction in heat transfer to the gun barrel is important because, reducing the temperature input into the barrel improves the accuracy during burst firing. As the gun barrel heats up, it expands. The expansion of the gun bore caused by heating is proportional to the linear coefficient of thermal expansion of the barrel material. Once the temperature of the gun barrel reaches 750c, The barrel expands to the point where the grooves (rifling) in the barrel do not engage the bullet. This causes the bullets to yaw and tumble in flight. Which reduces the accuracy of the weapon. The lack of grooves cut into the bullets 4, 5 and 6, indicate the barrel has expanded to the point where it no longer produces accurate fire. In this test of a plain steel barrel a 100 burst was fired, followed by 2 minutes of cooling. Then a 100 round burst was fired. After the second 100 burst all the bullets from the standard steel barrel begin to impact yawed / tumbled. In a burst test of the Stellite / cobalt lined barrel, the trigger is held down until the bullets begin to tumble and yaw in flight and impact, thus impacting sideways. The Stellite lined gun barrel can fire 350 round before all the bullets impact yawed. In this next series burst tests belts of combat mix ammo were fired. The C-1 schedule is a continuous burst fired until 100 % impact sideways / yawed. The Stellite lined barrel can fire a continuous burst of 295 bullets before the accuracy is degraded. Compared to only 167 bullets for the plain steel barrel. In another set of tests, a Settilte / Cobalt lined barrel was fired until the accuracy was reduced to the same point as the combat mix tests, 100% of the bullets tumbled / “keyholed”. The temperature of the barrel was measured to be 750C when all the bullets tumbled. We’ll use the temperature data from this test and the burst length from the combat ammo test to calculate the heat input per bullet into the plain steel gun and the Stellite / Cobalt lined barrel when belts of combat ammo are being fired. From the temperature monitored heating tests, we get the coefficient of linear thermal expansion of the gun barrel. 16*10^-6 or 0.000016 The coefficient of linear thermal expansion = The change in barrel diameter /( the initial barrel diameter * the change in temperature). This tells us how much the gun has to heat up to expand to the point where all the bullets tumble. The coefficient of linear thermal expansion of gun steel (0.000016) = The increase in barrel diameter due to heating (.006)/ the initial diameter of the barrel(.5) * The change in temperature (750). 0.000016=.006/(.5* 750) This says for the barrel to expand .006 inches the temperature of the barrel has to be 750C. When the diameter of the gun bore expands .006 inches, The bore diameter is greater than the depth of the rifling, the grooves in the barrel. When the bore diameter increases by .006 inches, The groves in the rifling no longer make contact with the bullet. No spin is imparted to the bullet and it tumbles in flight, resulting in a drop in accuracy. Since we know the barrel has to be 750c to expand enough for 100% keyholing to happen: The burst test conducted to 100% keyholing, provides us with a means to make a direct comparison of the two gun barrels. Since we can assume the barrel Temperature of both guns barrels was 750C when the test was stopped. *note the lower burst length in these tests is a result of the ammunition used. These bullets have a larger powder charges / higher muzzle velocity when compared to 50 Cal M2 AP ammunition We’ll compute the energy input per shot for the steel barrel and Stellite / Cobalt lined barrel. Based on the law of linear thermal expansion and the previous testing. We can assume Both barrels were 750c when 100% keyholing / tumbling occured. The coefficient of linear thermal expansion of gun steel (0.000016) = The increase in barrel diameter due to heating (.006)/ the initial diameter of the barrel(.5) * The change in temperature (750). 0.000016=.006/(.5* 750) If we assume that the ambient temperature of the guns was 20 C, We can solve the specific heat equation, to determine the energy per bullet needed to raise the barrel temperature 730c to 750C. Let's look at the steel barrel first and compute the energy input per shot. Barrel Temperature = ( Joules Per Shot * The number of shots)/ (Specific heat * The barrel Mass. 730 =( x * 167) / (.462 * 4.807) Joules per shot = (Temp * ( Barrel Mass * The Specific Heat of the barrel))/ Number of bullets fired. 9.707 = (730 * 2.220834)/ 167 9.707 Joules per bullet are transferred into the barrel when fired from the plain steel gun. The Stellite / Cobalt lined barrel reaches 750c after firing a 295 round burst. Therefore the energy input per shot is (730 * 2.220834) / 295 =5.495 Joules per shot. The Stellite / Cobalt liner reduces the thermal energy transferred into the barrel by 56%. On a per shot basis, the barrel of a Stellite / Cobalt does not heat up as much as a regular steel gun. Therefore the barrel of the Stellite barrel expands less than the regular barrel per shot. Thus over a large burst, the Stellite barrel is more accurate than the plain steel barrel. While the accuracy and velocity life improvements resulting from the Stellite/ Cobalt liner to gun are impressive. The performance of barrels of the M3 machine gun were also improved by their Chromium plating. The development and testing of the Chromium plating is covered in the same NDRC report. The Chromium plating also improved the velocity life and accuracy life of the gun barrel. However Chromium plating primarily improved accuracy of the gun. The Chromium plating of the barrel chokes the bore. Meaning the plating reduces the bore of the gun near the muzzle. The bore of the Chromium plated barrels is reduced from .5 inches near the breech to .492 inches at the muzzle. This reduces the loss accuracy due to heating. Going back to our calculations of the linear thermal expansion of the gun. We can calculate the temperature need to increase the narrow barrel diameter to the original diameter .5 Since the linear coefficient of expansion is intrinsic to the gun barrel material. algebraically we can compute the temperature needed to make the Chromium barrel expanded from .462 to .5 inches or .006 inches Coefficient = material expansion/(Bore of the Gun * temperature of the gun.) 0.000016=.006/(.492* x) Temp = ( expansion / Coefficient * Bore) 762.1951 =.006/(0.000016*.492). In the report it’s noted that the temperature required to increase the muzzle diameter of the plated barrel to .5 inches is 800C Tests of the Chromium plated barrel indicate that 319 consecutive bullets can be fired before the accuracy is degraded. If we assume 800 C is the critical temperature for this accuracy reduction and 319 bullets are fired we can compute the number if Joules per shot fired were fired to reach 800C. Well assume the ambient temperature is 20C and compute the Joules per bullet based on a 780 C rise in barrel temp. Joules per Bullet = ((Barrel Mass * Spec Heat) * Change in Temperature) / The Number of Bullets fired. 5.42 = ((4.807 * .462)* 780) / 319 The accuracy of the Chromium plated barrels was remarkable when compared to the accuracy life of the plain steel barrels. On the same 100 round burst 2 min of cooling schedule. The line barrels can fore over 1000 rounds without a reduction in accuracy. The plain steel barrel, on the same firing schedule, loses accuracy halfway into the second 100 round burst. The chromium plating also helps to reduce the heat input to the barrel, While not as effective as the Stellite / Cobalt liner, it still helps. Temperature monitored tests of the barrel give an indication of the effect. The plated barrel was seen primarily as an accuracy enhancement, While the Stellite / Cobalt lined barrel was seen as velocity enhancement. Since the two improvements were complementary, The Stellite liner was combined with Chromium plated barrel to provide a gun with the best features of both materials. When the Stellite / Cobalt liner and Chromium plated were combine, the barrel was known as a “combination” barrel. The performance of the combination barrels was remarkable. The guns equipped with these barrels, could be fired without a loss of accuracy and minimal velocity drop until the barrel melted. Given the increased performance of these barrels, why does the 50 Cal M3 have a 200 round burst limit? The burst limit is not the result of decreased velocity or accuracy. The burst limit is pure a function of the cook temperature of the ammunition. The manual for the 50 caliber M3, actually notes ``The treatment of the barrel gives it exceptional velocity and accuracy life, but does not affect the cook off point.” A cook off is an uncontrolled firing of a bullet inside of the gun. https://www.smallarmsreview.com/archive/detail.arc.entry.cfm?arcid=13265 The cook off point is temperature in the breach which will cause the bullet to fire on its own, without a trigger pull. The M3 weapons Manual notes that a 200 burst is the cook off limit. The NDRC report gives the temperature above which a misfire / cook off can occur. 900 F = 482C the cook off temp. Using the specific heating capacity of the real gun we can calculate how many bullets in a burst it would take to heat the gun up to 482 C. We’ll assume the ambient temperature of Barrel is 20 C. The barrel reaches the cook off / misfire temperature after a burst of 221 bullets have been fired. As the number of shots fired = ((Barrel Mass * Specific Heat) * delta Temp) / Joules Per shot Assuming the ambient temp of the gun is 20 c. The temp has to rise 462C to reach 482C, the cook off temp. 221.6 = ((4.807 * .462) * 462) / 4.63 By using the test data, we can compute the burst limit within 21 rounds of the limit given within the manual. When we compare the burst limit to the performance tests of the real gun barrels, it is obvious that the burst limit of the F-86’s are not reflective of a performance drop of the guns. f86 gun heat .trk
  2. per the report cited in the OP. The peak power figures come from this Public Canadian radar assessment. https://www.collectionscanada.gc.ca/obj/s4/f2/dsk2/ftp04/mq22118.pdf
  3. Problem : After the GAR-8 is launched, it takes about 2 seconds before the missile will begin to maneuver to intercept the target it is tracking. The GAR-8 in game may also not pull enough G. According to various official sources, The missile should begin to maneuver 0.5 seconds after it leaves the rail and pull up to 12 g. Details Below. The GAR-8 and the Sidewinder B are the same missile. Per the 1971 Air Force Data Sheet for the GAR-8. According to the Declassified 1966 Manual for Sidewinder B the missile should begin to maneuver 0.5 seconds after firing. https://archive.org/details/OP23093rdAIM9B The manual describes the operation of the missile: The Time line for the operation of the missile is as follows. 1. The Trigger is pulled, The seeker gyro / gimbal is unlocked. The seeker has +-30 degree FOV. null And will track the target through +-30 degrees. 2. 0.8 seconds after the trigger is pulled, the missile leaves the rail. The seeker is tracking the target. However maneuver commands are inhibited 3. 0.5 seconds after the missile has left the rail; Steering capabilities are initiated, as command signals are applied to the control servos. The missile will now pull up to 12g's to intercept the target. 21 seconds after launch; Guidance stops as the gas generator burns out. 24 seconds after launch; the missile self destructs. What I think is happening in game is, 1.the missile comes of the rail instantly, 2. maneuvering is prevented until the time of flight is +1.2 to 2 seconds. 3. After 1.2 to 2 seconds the missile begins to track the target. Meaning that, Either maneuvering is being inhibited for too long or the missile is not pulling enough G to intercept after it leaves the rail. The result of the current implementation is; Shots which are within parameters miss, because of the missile is prevented from maneuvering for to long, or wont pull enough to intercept it's target. Attached is a track which illustrates this. In this mission I've attached a 4000 foot zone to a non maneuvering MIG 15. Shooting from within 4000 feet will give the missile a time of flight of 1 to 2 seconds depending on the closure rate. When firing the GAR-8 with good tone, within 4000 feet, and within the seekers +-30 degree FOV, the missile will not track. Kills can be achieved but the missile has to be ballistically aimed. IE it functions like a rocket with a proximity fuse. In closing, the GAR-8 should be pulling up to 12 g's 0.5 seconds after it leaves the rail. Gar 8 test.trk
  4. https://www.enginehistory.org/Turbochargers/TSCtrlSys/TSCtrlSys1.shtml The regulator has 2 pressure bellows. The top bellows is exhaust pressure + ambient pressure. The bottom is a vacuum or partial vacuum. With the boost lever forward , at sea level and the waste gate open, and therefore, zero tubro RPM. The force acting on the regulator to keep the waste gate open is ambient pressure . As ambient pressure drops, the waste gate closes and the tubro RPM increases. Maybe you can just 64 inches of manifold with water injection alone. Edit, Looks like the water injection system bias the tubro regulator to allowing the tubro to spool at low alt.
  5. They in the encrypted Database files. https://github.com/Quaggles/dcs-lua-datamine/tree/master/_G/db/Units/Planes/Plane
  6. 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 Stability issues are noted above Mach .92. However they can be counteracted by ~5 degrees of alieron. Also, as mach increase the force to command more g increase above mach .86 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. 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 evidenced of this instability is noted in the pilots manual too. 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. https://ntrs.nasa.gov/citations/19930087699 However the fence also reduced Cl max of the aircraft from ~1.4 to ~1.2. 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. 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.
  7. FA-18A.lua has the old Cl Max of 1.2 FA-18C.lua has the old Cl Max of 1.2 FA-18C_Hornet.lua has a Cl max of 2.4
  8. 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. 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
  9. It looks like a change to lift coefficient in the simple flight model also increased the drag 6 times. Resulting in degraded performance. In the last patch, the Cl max in Simple Flight Model for the F-18C was doubled. It went from 1.2 to 2.4. This also caused the drag to increase. In the SFM the drag is computed directly from the lift. The drag computation is given as: Cx = Cx_0 + Cy^2*B2 +Cy^4*B4. Where B2 and B4 are coefficients also defined in the SFM. Cx is the drag and Cy is lift coefficient. Previously Cl max was capped at 1.2. it is now 2.4 This meant the drag at Cl max with flaps was Cx = (Cx0 + Cx Flaps) + (Cy^2*B2) + (Cy^4* B4) The old SFM F-18C, at mach .2 at CL max, 1.2, with the flaps down, had a drag coefficient of .584 Cx .584 = (Cx0 .0154)+ .(Cx Flaps. 23) + (Cy Max 1.2)^2*(B2 .134) + (Cy max 1.2)^4* (B4 .056) The new SFM at Cl max, 2.4 with flaps down has a drag coefficient of 2.905 Cx 2.905= (Cx0 .0154)+ .(Cx Flaps .23) + (Cy Max 2.4)^2*(B2 .134) + (Cy max 2.4)^4* (B4 .056) The previous version, Cl max of the F-18C was capped at 1.2 it is now 2.4. Based on the the ratio of Cl to alpha as defined in the SFM; If the current SFM F-18C goes over 13.8 AOA with the flaps down, then it will have more drag than previous previous version of the SFM F-18C was capable of producing.
  10. It's both. The bullets have to much drag and the barrel heating penalties (accuracy and velocity drop) are to high. However the MiG-15 also has issues with it's armament. The 23mm HEI shells don't fire. So the 23mm cannon only has half the ammo. 40 rounds not the 80 it's supposed to have. Also, the 23 mm AP rounds have their caliber set to 37 mm. Which I assume was a hack to get the 23 mm cannon to work.
  11. I also noticed that the 23 MM HEI shells don't seem to be firing. Perhaps because their caliber is set to 23mm and there is some type of engine limit that prevents aircraft from having multiple caliber weapons. I tested it by placing a static on the runway and firing the 23mm guns only. No 23mm HEI shells show up in the logs. Only API Rounds.trk The 23 mm HEI should show up in the logs as user_name = "23mm HEI T", based on the shell table entry. The API do appear in the logs. They match their reporting name as defined in the shell table. user_name = "23mm API" However the 37 MM HEI shells seem to be working. Tested by firing on a static with only the 37mm firing. The HEI rounds show up in the logs. 37 MM API and HE Rounds.trk It may be, that the 23 mm shells need to have their caliber also set to 37mm for them to work too. Right now the 23 mm HEI have their caliber set to 23mm. In the files it looks like this. AP_cap_caliber = 23, Da0 = 0.0007, Da1 = 0, Dv0 = 0.005, _file = "./CoreMods/aircraft/MiG-15bis/MiG-15bis.lua", _origin = "MiG-15bis AI by Eagle Dynamics", _unique_resource_name = "weapons.shells.NR23_23x115_HEI_T", caliber = 23,
  12. One of the shells that MIG 15 uses is the "NR23_23x115_API.LUA". Has the caliber is set to 37, not 23. Not sure if it effects any of the modeling. Just thought I would bring it your attention. First in the shell table. weapons_table/weapons/shells/NR23_23x115_API.lua NR23_23x115_API.lua ["weapons_table"]["weapons"]["shells"]["NR23_23x115_API"] = { AP_cap_caliber = 37, Da0 = 0.0007, Da1 = 0, Dv0 = 0.005, _file = "./CoreMods/aircraft/MiG-15bis/MiG-15bis.lua", _origin = "MiG-15bis AI by Eagle Dynamics", _unique_resource_name = "weapons.shells.NR23_23x115_API", caliber = 37, Then in db/Units/Planes/Plane/MiG-15bis.lua }, <6>{ AP_cap_caliber = 37, Da0 = 0.0007, Da1 = 0, Dv0 = 0.005, _file = "./CoreMods/aircraft/MiG-15bis/MiG-15bis.lua", _origin = "MiG-15bis AI by Eagle Dynamics", _unique_resource_name = "weapons.shells.NR23_23x115_API", caliber = 37, Also in Eagle Dynamics\DCS World\CoreMods\aircraft\MiG-15bis\MiG-15bis.lua declare_weapon({category = CAT_SHELLS,name = "NR23_23x115_API", user_name = _("NR23_23x115_API"), model_name = "tracer_bullet_crimson", v0 = 680, Dv0 = 0.0050, Da0 = 0.0007, Da1 = 0.0, mass = 0.199, round_mass = 0.340+0.071, -- round + link cartridge_mass = 0.0, -- 0.111+0.071, cartridges are ejected explosive = 0.000, life_time = 5.0, caliber = 37.0,
  13. The correct Muzzle Velocity for the M2 AP should be 2,840 FPS, 865 MPS. The reduction in accuracy and velocity due to barrel heating should be reduced to reflect the qualities described in weapons manuals. Possibly replaced with either a cook off event or a jam. With regards to the correct muzzle velocity for these rounds. The manual for the AN-M2 and AN-M3 both give the same muzzle velocity for the various rounds. From the 1947 version of the AN-M2 manual, TM9-225 1947. http://www.nj7p.org/Manuals/PDFs/Military/TM 9-225 28-Jan-47 Google.pdf The AN-M3’s ammo table and muzzle velocity from the 1955 version of the AN-M3 manual, TM 9-2190 Both manuals also refer to the same document, which provides the ballistic profile of the ammunition. Ballistic Data Performance of Ammunition TM-9-1907 https://ia800909.us.archive.org/22/items/TM91907BalisticDataPreformaceOfAmmunition/TM%209-1907%20Balistic%20Data%20Preformace%20of%20Ammunition.pdf A cleaner version of this chart is available in https://cgsc.contentdm.oclc.org/digital/collection/p4013coll8/id/2374 TM 9-1907 also gives the muzzle velocity as 2,835 FPS. So this appears to be the correct muzzle velocity for M2 AP round. However, in some of the literature, the muzzle velocity is quoted as 2700 fps. This lower velocity 2700 fps comes from 1940 version of the AN-M2 manual -TM 9-225 https://ia601208.us.archive.org/21/items/TM9-225/TM9-225.pdf It gives the velocity of the M1 AP Round as 2700 fps at 78 feet. Then in 1942, the revised TM 9-225 manual states muzzle velocity for the M2 AP round is 2900 fps. https://digital.library.unt.edu/ark:/67531/metadc29988/m1/50/ It appears the correct muzzle velocity for the M2 AP rounds is 2840 FPS, As the most current sources list it. On burst length. The manuals for both guns, indicate barrel heat affects 4 aspects of the guns performance, velocity, accuracy, stoppage, and cook off. The 150 round limit cited before, a 11 second burst, is the stoppage limit (the gun locks up) of the AN-M2, due to overheating. There is also a burst limit due to the possibility of a ammunition cook off. That is, the rounds heating up to point where the powder charge ignites and causes inadvertent firing. For the AN/M3 the 200 rounds burst limit is due to the possibility of a cook off, not a reduction in accuracy or velocity. The reduction in accuracy or velocity due to barrel heat occurs at different temperatures. The accuracy reduction is referred to as Key-holing in the manual. The AN/M2 manual notes, the circumstance in which the accuracy is degraded separately from the conditions that result in a reduction of the bullet’s velocity. The conditions depend on the barrel type and the number of rounds fired.. The 50 Cal AN/M3 has a plated and lined barrel and the ammo is more likely to cook off, before the velocity and accuracy are reduced. As the cook off limit is 200 rounds and the accuracy degradation occurs at 300 rounds. The maximum burst length before there is a reduction accuracy, is 300 rounds. This should happen without a reduction in velocity. The AN/M3 manual also notes that the operating parameters described are for temperate conditions at low altitude. So perhaps the increase in barrel temp can be reduced to reflect operation at high altitude.
  14. The drag on the bullets the Sabre uses are to high. The F-86 uses the bullets as defined in the lua files as. shells = {"M2_50_aero_AP","M20_50_aero_APIT"}, mixes = {{1,2,2,1,2,2}}, -- In the shell table the drag currently is defined as M20_50_aero_APIT.lua cx = { 0.5, 0.61, 0.8, 0.27, 2 }, M2_50_aero_AP.lua cx = { 0.5, 0.61, 0.8, 0.27, 2 } The variables are defined as. -- Drag (Сx) = { 0.5 , -- Cx_k0 Cd0 at low mach ( M << 1) 0.61 , -- Cx_k1 Peak Cd0 value 0.8 , -- Cx_k2 steepness of the drag curve before the transonic wave crisis 0.27, -- Cx_k3 Cd0 at high mach (M>>1) 2 , -- Cx_k4 steepness of the drag curve after the transonic wave crisis } Drag profiles for all the rounds are available from primary sources. Primarily, the US Ballistic Research Lab. The first two drag profiles are from the Ballistic Research Lab's 1990 range test. "The Aerodynamic Characteristics of .50 Ball, M33, API, M8, and APIT, M20 Ammunition. By Robert McCoy. https://apps.dtic.mil/dtic/tr/fulltext/u2/a219106.pdf Lets start with the API M8 Then The M20. Finally We have a drag profile for the M2 AP round. This chart is in older format Kd. However this can be converted to the standard notation for the Drag Coefficient Cd / Cx. The conversion is Cd = (8/Pi) * Kd The method is given in McCoy's work. The drag profile is from Report 620, Aerodynamic Data for Spinning Projectiles” H.P. Hitchcock Ballistic Research Laboratories, Aberdeen Maryland 1947. https://apps.dtic.mil/sti/pdfs/AD0800469.pdf From the chart, peak drag occurs at Mach 1.2 and the Kd is ~ .161 Converting using McCoy Cd = (8/Pi) * .161 Cd = .4099 At mach 2 the Kd is = .14, therefore the Cd = .35 The slope of drag curve at Mach > 1 is = .4 - .35 / .8 = .05 The drag at low Mach is ~.078 Kd = .1985 Cd The slope of the drag profile before area transonic appears flat. Therefore the drag for the rounds should look more like, M2_50_aero_AP.lua cx = { 0.198 0.4, 0.0, 0.4, .05 }
  15. This is from 1995, I dont know if the accuracy has been increased since then. https://apps.dtic.mil/sti/pdfs/ADA299307.pdf
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