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Magnitude3 New Year’s Update Bye Phant

I was quite excited by the new F4U but have heard some criticism of the flight model and engine power. So, I wanted to take a closer look to see how it compares to both the quantitative and qualitative metrics published in the wonderful article entitled “Ending the Argument” by John M. Ellis III and Christopher A. Wheal, published in EAA Sport Aviation, June 1990. Now, for the caveats… The article was a pseudo-controlled experimental flight-test designed to evaluate performance differences between the FG-1D Corsair, P-47D Thunderbolt, F6F-5 Hellcat, and P-51D Mustang. I know we do not have a true representation of the FG-1D, however the engine (R-2800-8) and airframes are close enough for my lackluster piloting skills. Interestingly, it also had two stores pylon installed for the flight tests. Airframe and engine stresses were limited owing to the age of the airframes and using 100LL fuel. This effectively limited the Corsair to Maximum Except for Takeoff (METO). I used 55” of manifold pressure, which is likely too high, but at least my assumptions have been documented. The engine was officially rated for 2000 BHP as in the DCS model. Superchargers were limited to low-blower, and altitudes to 10,000 ft. This makes a difference as I will demonstrate. CG was located at ¾ aft, and there was no mention of fuel load. I selected ½ tanks but will likely revisit my data with another series of tests at full fuel. I removed all ammunition weight as the test aircraft had dummy 50 cals, but no ballast ammo (near as I can tell). My controls setup uses a curve of 25 on all axes, and a 70% saturation on the rudder deflection. I performed some tests multiple times when I suspected higher variance due to my shoddy pilot skills. That being said, I did not perform detailed error analysis on the data presented herein. I welcome others to try the tests and post your results. On to the data… Test 1: Takeoff distance: As per the manual, takeoff distance for the aircraft at 11,000 lbs is approximately 900 ft at sea level, and 1,300 ft over a 50 ft obstacle in no-wind conditions. I won’t say much here other than my takeoffs were all around 1,200-1,300 ft, which I am certain is dominated by inferior pilot skill on my part. The test pilots note a takeoff roll of 1,200 ft at METO power, which is more or less in line with my tests. Test 2: Climb Performance: I will not reprint the graphs from the article as I want to ensure full credit to the original authors and not run afoul of copyright concerns. However, I have used plot digitizer to extract relevant FG-1D data for comparison to our DCS model. The first test is a time-to-climb test, started from the runway up to 10,000 ft. The flight was conducted at full METO power with a climb speed of 135 kts, takeoff weight of 11,055 lbs, and surface temperature of 77 F (as per Table 1 in the article). The figure below shows the time history of MSL altitude for the FG-1D, DCS F4U, and two data points from the F4U-1D manual corresponding to full Mil-Power climbs to 5,000 and 10,000 ft. How I did it: I started on the runway with 50% fuel and executed a standard takeoff. I reduced power to full METO power which was giving ~55 in of manifold pressure @ 2700 RPM. I trimmed the aircraft for 135 kts which required substantial trimming on all axes. The remainder of the flight was relatively hands off, only requiring small corrections to attitude to maintain airspeed. I put the mixture into auto-lean as per the flight manual, and did not engage the blower. Discussion: First off, the flight data presented in the report starts at ~1,000 ft MSL with no discussion of initial conditions. I time aligned my data to overlap the altitude at ~2,000 ft MSL to discount the takeoff and trim transients. After this point, there is a slight climb-gradient difference between the DCS and FG-1D aircraft, however it may be within the test margin of error with time-to-climb difference of 15 seconds. In the article, the Corsair, Thunderbolt, and Mustang were all tightly grouped, with the Hellcat outperforming all by nearly 30 seconds. So, in this case our data would group more closely with the F4U/P47/P51 as it should. The flight test and DCS data align well with the manual to 5,000 ft, however the 10,000 ft mark is quite offset, requiring another 50 seconds of climb. I suspect this is related to the weight of the aircraft and will repeat the tests with full fuel when able. Test 3: Level Accelerations: This is one of my favorite flight test maneuvers as it requires some pilot skill (yikes) and tells you quite a bit about the power and drag characteristics of the aircraft. In brief, the test starts at 10,000 ft and pattern speed, which is ~100 kts in the Corsair in the clean configuration. Full METO power is smoothly applied, and every attempt is made to maintain a constant altitude. The time history of airspeed is logged and is an indicator of excess power from the engine. Flying this test in the Corsair is a real challenge owing to the massive change in trim and quick dance on the rudder pedals necessary to maintain straight, coordinated flight during the maneuver. How I did it: I matched the flight test OAT at 50 F, and started straight and level at 10,000 ft. (I actually began the flight at closer to 150 kts and decelerated to 100 kts without retrimming, which makes the initial acceleration easier to deal with as you only need relieve pressure on the controls to maintain straight and level flight.) I repeated the test three times, once with the blower in neutral, another with the blower in low, and the final test with the manifold pressure limited to 40 in. Discussion: The plot below shows the time history of indicated airspeed for the FG-1D, and three tests corresponding to METO neutral, METO low blower, and 40 in. of manifold pressure settings. The low blower allowed for close to 60 in. of manifold pressure at 10,000 ft, whereas the neutral blower case was closer to ~45 in. Clearly none of the test cases capture the flight test data of the FG-1D, indicating a mismatch in the excess power (Thrust*V_inf-Drag*V_inf). I cannot comment on the sea-level max airspeed debate, but as far as this test confirms, the engine thrust (I said thrust, not power) seems to overpredict the measured performance data of the FG-1D. I.E. the velocity scaling seems to be off, allowing for higher accelerations that would otherwise be possible while still achieving roughly the same top-end speed. I suspect this is due to incorrectly predicting the slope of the C_T vs advance ratio curve at low – medium advance ratios or perhaps a lower induced drag from the airframe. Test 4: Stalls Power on and off stall characteristics were evaluated at 10,000 ft in the clean and dirty configurations (gear, 40 deg flaps). Slow deceleration rates on the order of 3 kts/s were used, though the flight tests were conducted with an even lower gradient of 1 kt/s. Test data in the table below indicates reasonable agreement except for the power-off, clean configuration. In this case, repeated tests were conducted to verify that the aircraft does stall repeatably at a much lower airspeed than the flight test aircraft. This could be due to a mismatch in vehicle weights, but similar tests conducted with full fuel will need to be performed to comment further. Stall performance FG-1D DCS F4U Power off (clean) 85 kts 74 kts Power on (clean) 76 kts 74 kts Power off (dirty) 69 kts 75 kts Power on (dirty) 55 kts 55 kts Qualitatively, the test pilots noted that the FG-1D had no propensity to drop a wing in either direction, favoring instead any turn towards the uncoordinated slip direction (slow wing). In my testing, I attempted to initiate stalls to either side and was unsuccessful in getting the right wing to drop. Asymmetric stall is a complicated aerodynamic phenomenon, but it appears the propeller torque dominates for the DCS module. Test pilots noted that there was little stall warning, perhaps only a few knots with light buffet. In a simulator this can be the best indication of impending stall, even if it’s slightly overdone (Tomcat anyone?). They did note a peculiarity with the Corsair in that the stick force gradient gets very light approaching stall, which would/will be fun when we all get force feedback joysticks! Test 5: Static Lateral-Directional Stability This test sheds light on the rudder authority in a steady, wings-level sideslip. The test pilots noted that the Corsair’s rudder control was extremely heavy compared to the other aircraft tested. Between 180-190 kts, the aircraft required ~50-60% aileron deflection to maintain level flight. In the landing configuration with full flaps and gear, ~20-50%. This wide margin corresponds to the increased influence of the engine torque and spiraling slipstream from the propeller at lower airspeeds. The test pilots noted a peculiarity with the Corsair in that, “The Corsair's only response to left rudder in either configuration as to drop its nose, suggesting weak or non-existent dihedral effect with right sideslip.” How I did it: This one is pretty straight forward. Trim for 180-190 kts at 10,000 ft, then smoothly apply full rudder control. Estimate aileron deflection necessary to maintain zero turn rate as measured by the slip/skid indicator. I repeated this several times in both the left/right directions and at lower airspeeds ~100 kts with full flaps and landing gear extended. Again, all flights were at 50% fuel and no ordinance. Discussion: At airspeeds between 180-190 kts, the aileron deflection is on par with the 50-60% noted by the test pilots, indicating that the rudder authority at higher airspeed is about correct with the 70% saturation limit (first figure below). At lower airspeeds, the aircraft requires almost the same level of aileron control (second figure below), indicating that the rudder control derivatives do not have the correct velocity scaling or the influence of the prop slipstream is not correctly captured. This is certainly an area where the flight model could be improved. Additionally, I think there’s an opportunity to add in the Corsair quirk of little roll with left rudder and nose drop as the current model is quite symmetric (albeit maybe somewhat visible in the bottom left plot). Figure: Full left rudder (left) and right rudder (right) with ~50-60% aileron deflection. High-speed condition, 190 kts, 10,000 ft, 50% fuel. Figure: Full left rudder (left) and right rudder (right) with ~50-60% aileron deflection. Landing configuration (gear + flaps 40), 110 kts, 10,000 ft, 50% fuel. Test 6: Roll Performance Full left/right aileron deflections were used to assess roll rates for a 1-G, full 360 deg roll. As with most other tests, this one was flown at 10,000 ft, and ~200-220 kts indicated. This test was also repeated in the landing configuration at ~100 kts with full flaps and landing gear deployed. Obviously, a full 360 deg roll would be inappropriate with full flaps and gear, so the test was terminated at 90 deg of bank. At high speed, the aircraft needed full continuous power, and only ~28” manifold pressure in the landing configuration. A follow-on test of “rolling under G” was performed by executing the same high-speed maneuver with a steady 3-G load on the airframe (sort of a barrel roll I guess). The pilot reports indicate a significant reduction in roll performance under load with the Corsair giving up ~26-38% of its 1-G roll rate. Of note, these tests involved a 180 deg roll, not the full 360 used for 1-G testing. Data for all tests used the time to perform the complete roll in lieu of instantaneous roll rate data which is often much higher. Discussion: The table below highlights the difference in roll rates at high and low speed for the FG-1D and DCS F4U. Measured roll rates for the DCS F4U align reasonably well at high speed for the left-hand rolls. However, as is obvious from the data, the right-hand turning capability is off the mark. Low speed performance is symmetric, but slow. This again is a straightforward fix in the flight model, and I hope it makes its way into the next update. The accelerated data should be taken with a massive grain of salt as it is quite pilot dependent and holding a 3G turn without using your bottom as a G-indicator is difficult to say the least. I would appreciate community feedback on your numbers for this maneuver. Roll Performance FG-1D DCS F4U Right (high speed) 4.5 s (81 deg/s) 5.4 s (66 deg/s) Left (high speed) 4.9 s (73 deg/s) 5.1 s (70 deg/s) Right (low speed) 2.3-4 s (38 deg/s) 2.9 s (31 deg/s) Left (low speed) 2.3-4 s (38 deg/s) 2.8 s (32 deg/s) Right 180 deg (3G high speed) 3.1 s (58 deg/s) 6.1s (30 deg/s) Left 180 deg (3G high speed) 3.7 s (49 deg/s) 5.4s (33 deg/s) Test 7: Dynamic Stability I’ve seen quite a bit of chatter about the rudder authority and “wagging” (aka Dutch roll) of the F4U online, so I was particularly interested in assessing the directional dynamic response. Pilot reports indicate that all aircraft were deadbeat (aka, no overshoot) in the roll and pitch axes, and that the Corsair was notable for its pronounced Dutch roll. How I did it: Dynamic stability tests should be made with relatively small control inputs so as not to significantly alter the aircraft’s speed or altitude. I used either singlets (rapid fore/aft or side) motions to induce oscillations and noted any overshoot in the short-period, or oscillation in the long-period modes. Discussion: The pitch and roll axes were well behaved with little overshoot and no noticeable oscillation. The pitch axis is quite sensitive, but pilot reports indicate that it had the lightest control force gradient (stick force per G) of all aircraft tested. I cannot really say for sure, but it’s plausible that we need to fly it more like an Extra 300 and less like a P-47, so go light on the controls. Perhaps. The rudder control, on the other hand, does show substantially lower damping than indicated by the test pilots. They noted the worst case was three overshoots before the oscillation was damped. In my tests, I was routinely experiencing 6-8 (see plot below) with corresponding lower amplitude, but higher damping oscillations in roll. Again, from a flight model perspective this is a relatively easy fix (C_N_β anyone?), so I hope it too is incorporated in future updates. Test 8: Dive Test This test can also give some indication of the excess power/drag behavior of the aircraft, and how much trim control is necessary to compensate for speed buildup. This test is initiated at 10,000 ft MSL and ~100 kts, followed by a -1G pushover to a 30 deg dive and applying full METO power. Recovery is initiated at 5,000 ft noting the max speed at pullout. The pilot reports indicate that the Corsair had high rudder forces requiring retrimming during the dive. Discussion: From the table below, the DCS F4U is not far off the mark in the dive test. Starting at 100 kts, it matched the test aircraft to within 7 kts passing through 5,000 ft. Of note, my dive angle was slightly higher with an average of ~34 deg. I used the gunsight to estimate the angle, but precise control is tricky without some sort of digital readout. Of note, the aircraft does require increased rudder deflection as the speed builds and is relatively easy to trim as indicated by the pilot reports. This indicates again that the excess power and drag characteristics of the airframe are mismatched as the dive time is significantly faster than the measured data. As with the level acceleration, this seems to point to a mischaracterization of the thrust and/or drag at low to medium speeds. That being said, the required rudder trim at different airspeeds is probably correctly modeled. Dive Test FG-1D DCS F4U Start Speed 100 kts 100 kts Max Speed 348 kts 341 kts Time 32 sec 23 sec Conclusion: In summary, I think we have a wonderful start at one of my favorite aircraft. I hope Magnitude 3 will continue to develop the module and address some of the flight model issues that make the Corsair unique and a challenge to extract maximum performance. Specifically, I see the following issues that could use a bit of tweaking: Takeoff: Find a better pilot . Climbs: Reasonable agreement, engine power may be slightly overpredicted Level Accelerations: Tune the low-medium speed thrust and drag model to better approximate measured accelerations. Stalls: Uncoordinated stalls seem to always break left; this should not happen. Clean, power-off stall is too slow. Static Directional Stability: Low-speed rudder sensitivity too high, high-speed just about right with 70% saturation. Incorporate Corsair pitch quirk with left rudder and tune roll coupling. Roll: Resolve the left/right disparity in roll performance. Dynamic Stability: Directional damping needs to be increased to match the three-overshoot oscillation noted in flight test. Dive Test: As noted with the level accelerations, tuning of the thrust and drag models are needed to better match available data. I would like to repeat many of these tests with full fuel to further explore the flight model and ascertain if any of the noted discrepancies persist in a heavier configuration. I am also exploring sustained and instantaneous turn data, but it is somewhat complicated by scatter and self-imposed structural limits in the flight test data. I would greatly appreciate any constructive feedback and additional references that may have been used in developing the flight model to augment this analysis.

Evening, Was doing a multiplayer mission at night today. I needed to bind some of the external light switches (Recognition lights - amber/green/red - cycle/Flash/Off/Steady), and while the keybinds where all there, binding the button didn't do anything. I bind the buttons to my throttle (TWCS Thrustmaster), but pressing the designated button on my throttle doesn't do anything (all the other binds i've tested work so far). Absolutely LOVE this plane! You people have done a fantastic job developing it! Been waiting for this plane to come out for a while and the reward was ABSOLUTELY worth it so far! I salute you! peter_121_GR (Platypus)