nairb121

A g-load that high can't be sustained for long, but the pilot should still last at least 2-3 seconds (and that's all this maneuver was). There's an IRL case of an F-15(C I think) pulling 13-14g in an emergency dive recovery. IIRC they were able to RTB safely, but the plane's structure was permanently bent, so it was written off.

The thing is, the wings don't break because of a specific g-value - they break because they are carrying a force greater than the structure can withstand. The same g with a lighter jet is a lower force (F=ma), so a lighter aircraft can pull more g at the same wing stress. This is what the 1.5 design safety factor is applied to. This is also part of why a clean, light jet typically has higher allowable g-loads (like in my manual excerpt above) than a loaded, heavy one (the main other reason being store carriage limits). If another aircraft in DCS always breaks at the same g regardless of weight - then that is a modeling inaccuracy on that aircraft and shouldn't reflect on the F-5.

It's not impossible, but it would surprise me if this were the case on an older module like the F-5. Also, the original screenshot at the top was taken after several minutes of flying with high g-loads (though I don't know the exact numbers reached) - if that's why it broke at 13g after 2 hard pulls, then it probably would've broken far sooner in the original scenario.

My thoughts as well - I recorded a short track at 10% fuel and 50% ammo. First pull is to 13.1g, second is to 14.0. Third pull to structural failure - interestingly, this occurred at 13g - maybe I introduced some roll inadvertently. F-5 14g.trk

It's neither, just a very hard (but, importantly, smooth and symmetrical) pull at very low weight. The tolerance of the wings is very sensitive to aircraft weight, and the aircraft was clean and, as this point, probably below 1000 lb fuel. Refer to my post above - given the ultimate strength implied by the prescribed g-limits at the maximum applicable weight, at very low weights the aircraft should be able to survive over 14g.

From the manual, for no stores except wingtip - limits are 6.5g above 2200 lb internal fuel (about 45%, gross weight roughly 12,900 lb) and 7.33 g below 2200 lb internal. Full gross weight is around 15,600 lb (all weights including full ammo). 6.5g at 15,600 lb = 101,400 lb "effective" weight supported by the wings; 7.33g at 12,900 lb = 94557 lb. Taking 101,400 as the "rated maximum" weight, and using a 1.5 safety factor, that gives a failure force on the wings of 152,100 lb. If I'm running on fumes and out of ammo (at empty weight of 10,308 lb), that means I can pull 14.8 g at the same wing strength. (Full discosure - I was not aware before that g was limited to 6.5 above 2200 lb internal fuel.)

The structural failure point is highly dependent on stores and fuel weight - clean and at 60% internal the wings fail at around 12g, and near fuel exhaustion it can get to around 14. Rapid G onset might cause it to fail earlier though. (Also I think that's me in the screenshot, hi!)

The critical factor in this testing was the fixed position of the stabilators. As you said, the aft CG results in less tail downforce required in level flight at a given speed; however, with the tailplanes maintained in their position, an aft CG results in a nose-up moment for this reason, with the result of stabilizing at a higher AOA and lower speed. With the stabilator position removed as a variable, and in steady state, the pitch moment equation becomes a relation only of AOA/speed and CG position. However, this is the reason that I'm seeking to perform further, and more straightforward, testing to confirm before submitting a bug report. My intent is to test this based on rotation speed with neutral stick; V^2 will be proportional to Weight * CG distance forward of the wheels.

I was just referring to the way the CG/AOA trend toward the far right side of their respective graphs. And I am indeed comparing, or at least relating, the %MAC and the AOA graphs - the AOA in stabilized level flight at a given stabilator angle is purely a function of the CG location. Correct, it's just a tank that feeds by gravity alone into the aft tank. My only concern with it is its effect on the CG. Unfortunately the manual refers to other documentation for CG calculations, which I have not been able to find. This would be much easier if I could. My purpose in this is to confirm whether the modeling is correct, and provide solid evidence for a bug report if it's not. It's relevant because, if my hypothesis is correct and the tanks aren't being used in the right proportions, it causes the CG to be up to 3% MAC aft of where it should be, causing incorrect flight behavior.

The center cell is mentioned on 1-41 and shown in the figure 1-34 on page 1-42: Using the known system capacities and the CG travel (in the previous post), I was able to determine approximate values for the tank positions and capacities, and produce a plot to confirm these value match the manual: My previous testing was based on determining AOA for straight and level flight at the same stick position for various fuel states (set via mission editor and with unlimited fuel) - a tail-heavy aircraft would hold a higher AOA and lower airspeed, and a nose-heavy aircraft the opposite. In theory the graph of AOA vs. fuel state should follow the same trend as the CG shift shown above - but the trend was quite clearly different: It offsets to the right similarly to the unbalanced trend; however, the fuel was not unbalanced (since it was unlimited and set by the editor, it couldn't be), and the point of the farthest aft CG was at a much higher fuel state. However, after some trial and error I discovered that it matches closely the plot of the CG if the center cell depletes completely before any consumption from the aft cell (the CG is significantly forward of the previous plot as the tests included ammunition): My plan for followup testing this weekend is to do some takeoff roll tests - with neutral stick, the speed at rotation will be a function of the CG and the total weight of the aircraft.

Weight and balance data would be good too (even better really). The reason I'm looking for this is that I believe there's an error in the modeling of the fuel consumption between the center and aft cells; Figure 2-2 in the -1 shows CG travel due to fuel consumption (also present in higher quality in the NATOPS): However, based on my observations and testing, the CG movement with the system balanced is not consistent with the travel shown. Instead it travels much farther back, then rapidly back forward. I determined values for tank capacity and locations from the figure; however it would be much easier and more accurate if there were known true values I could use. To match the travel shown in the figure, the center cell drains simultaneously with the aft cell, but empties first; this is consistent with the "CENTER CELL EMPTY" indicator shown. However, CG travel in DCS is consistent with a model in which the center cell drains completely before the aft cell begins to be used. I'm hoping to do some testing this weekend to produce clear data on this, so weight and balance data for the fuel cells (and the aircraft as a whole) would be extremely valuable.

Why the difference between left and right in "left missile (selection not required) or from right missile, if selected"? And "the left audio tone is not affected"? The way these are worded to specifically call out the left missile strongly indicates (in my opinion) that its behavior is different enough (more than just being priority) that it deserved additional attention. Could this be a variant difference between the F-5E/N and the F-5E-1/E-3? It seems like a stretch, there are only minor differences in the armament panel between the E and the E-1/E-3, and the E-1/E-3 have the same panel (and presumably same logic) as the N. It's frustrating how the NATOPS is missing these specifics on the left missile audio, while the -34 is missing the specifics on the wingtip selector switches - it makes it hard to piece together how it actually works. And, while we can assume that the same logic as the N and E-1 apply, neither of these actually contain data for the E-3.

According to the -1 (https://docdro.id/51orrvC), the fuel system has 3 internal cells - the Left system is served by the Forward fuel cell, while the Right system is served by the Center and Aft fuel cells. The manual lists the capacities of each system, but I'm not able to find the individual capacities of the center and aft cells - does anyone have information on this?

@dolfo Replying to this here to keep this discussion under the correct topic. I don't agree with your interpretation of the "Adjusts volume of audio tone... from left missile (selection not required)" passage. That the missile doesn't need to be selected, for the volume knob's position to be effective when it does get selected, is intuitively obvious, and would not need to be communicated to the aircrew. Furthermore, this interpretation is contradicted by the following "or from right missile, if selected." It doesn't make sense that the volume knob works on an unselected left missile but only on a selected right missile - unless the statement refers to the audible tone from an unselected left missile or a selected right one. I don't believe the NATOPS passage "The audio tone of either missile is activated or shut off by the corresponding wingtip armament position selector switch without arming the missile." contradicts this. It indicates that the missiles need not be armed for selection to produce tone; this is simply a missing feature and should be added. The passage from the -34, "To obtain the right missile audio tone, place left wingtip armament positions selector switch OFF and right wingtip armament position selector switch at up position", I believe indicates that the right missile tone and firing priority will override the left one if right is selected and left isn't. Finally, the -34 as shown above notes that the left missile audio tone is not affected by the External Stores Selector being moved out of SAFE - this inhibits firing but tone will still be present. I believe this is the same logic that provides the left audio tone when the left missile is deselected and the Guns, Missile and Camera switch is set to GUNS, MSL & CAMR. So to amend my proposed missile logic (on the other thread) based on the added information: Guns, Missile and Camera Switch set to OFF or CAMR ONLY: Left missile growls if selected but cannot be fired. Right missile growls if selected, and left missile is unselected, but cannot be fired. Guns, Missile and Camera Switch set to GUNS MSL & CAMR: SELECT JETTISON Switch set to OFF: EXTERNAL STORES Selector set to SAFE: Left AIM-9 growls if present, if selected or both missiles are unselected, but can only be fired if selected. Right AIM-9 will only growl, and can only be fired, if selected and left missile is unselected or missing. EXTERNAL STORES Selector set to BOMB, RIPL, or RKT/DISP: Left AIM-9 growls if present and selected, or both missiles are unselected, but cannot be fired unless DM/DG mode is activated and the station is selected. Right AIM-9 will only growl, and can only be fired, if DM/DG mode is activated and the station is selected, and the left missile is unselected or missing. SELECT JETTISON Switch set to SELECT POSITION or ALL PYLONS: EXTERNAL STORES Selector set to SAFE, BOMB, RIPL, or RKT/DISP: Left AIM-9 growls if present and selected, or both missiles are unselected, but cannot be fired under any circumstances. Right AIM-9 will only growl if the station is selected, and the left missile is unselected or missing, but cannot be fired under any circumstances.

Are the wheel chocks in place? If so, you'll need to ask the ground crew to remove them. If it were just brakes the engines should be able to overcome them.

Hell no. Thanks for pointing this out, this suggests my interpretation above is incorrect or at least inaccurate. I've not been able to find a publicly accessible F-5E NATOPS, is there a source where we can find it?

Yes, I agree. Based on what I've read, I believe correct behavior should be: Guns, Missile and Camera Switch set to OFF or CAMR ONLY - No growl under any circumstances2. Guns, Missile and Camera Switch set to GUNS MSL & CAMR: SELECT JETTISON Switch set to OFF: EXTERNAL STORES Selector set to SAFE: Left AIM-9 growls if present, regardless of selection3, but can only be fired if selected4. Right AIM-9 will only growl, and can only be fired, if selected4. EXTERNAL STORES Selector set to BOMB, RIPL, or RKT/DISP: Left AIM-9 growls if present, regardless of selection3, but cannot be fired unless DM/DG mode is activated5 and the station is selected4. Right AIM-9 will only growl, and can only be fired, if DM/DG mode is activated5 and the station is selected4. SELECT JETTISON Switch set to SELECT POSITION or ALL PYLONS: EXTERNAL STORES Selector set to SAFE, BOMB, RIPL, or RKT/DISP: Left AIM-9 growls if present, regardless of selection (conjecture based on the behavior above) but cannot be fired under any circumstances6. Right AIM-9 does not growl (conjecture based on the behavior above) and cannot be fired under any circumstances6. The MISSILE VOLUME Knob should be effective at any time the growl is audible, including the unselected left missile1. The source states that "The audio tone cannot be manually turned off." 1T.O. 1F-5E-34-1-1, Figure 1-28, #1 2T.O. 1F-5E-34-1-1, Figure 1-28, #4 3T.O. 1F-5E-34-1-1, Figure 1-28, #5 4T.O. 1F-5E-34-1-1, Figure 1-28, #6 5T.O. 1F-5E-34-1-1, Figure 1-28, #9 6T.O. 1F-5E-34-1-1, Figure 1-29, #3

I read deeper into the -34 and it's become clear that the left sidewinder doesn't follow the weapon selection rules as expected. It actually appears to be correct for it to produce a growl when deselected or when the External Stores selector is out of SAFE - if this is the case, I believe it's likely it will also ignore the jettison switch position. Has this particular issue been tested to determine if the left and right missiles behave differently? (I hope whoever fixed the "bug" didn't delete the old code...)

The thread above was concerning a reported bug where the sidewinder growl would continue with the missiles not selected. It was later determined that the left missile was the source of the problem. However based on this section (Figure 1-28) in the -34 (https://www.digitalcombatsimulator.com/en/files/1946809/) it appears that it's correct for the left AIM-9 to growl regardless of selection, as long as the Guns, Missile, and Camera switch is set to GUNS MSL & CAMR and there is a missile on the station. However, the the volume knob should still control the volume of the audio tone. This will also be the case when the External Stores selector is out of the SAFE detent - the missile cannot be fired but the left AIM-9 will still produce an audio tone. Selecting DM or DG mode should allow the missiles to be fired and (I assume) the right missile to be heard, regardless of the External Stores selector position. It's not clear why the left launcher behaves differently. The only difference appears to be the left launcher's provisions for the TDU-11/B target rocket - maybe something about this implementation causes the unexpected behavior.

Reading the -34 (https://www.digitalcombatsimulator.com/en/files/1946809/), I'm definitely leaning towards the growl being incorrect when the select jettison switch is moved out of OFF. It specifies that the AIM-9, when jettisoned, is launched unguided - meaning the seeker should be inactive. Additionally, it notes the select jettison switch as disabling normal release and arming circuits - so it should be expected that the seeker and fuze are unpowered when the switch is moved out of the OFF position. The section on the wingtip launch rails indicates that there are 3 connection points to the missile, one for the guidance/control section, one for the fuze, and one for the motor. It seems likely that when jettison is selected, the guidance and fuze sections are unpowered and only the motor igniter is powered.

Note that the 1977 manual is for the earlier F-5E and not the F-5E-3 variant we have - the 1984 F-5E/F manual (https://docdro.id/51orrvC) incorporates all E/F variants up to E-3 and F-2. In this case it doesn't matter much (there is a slight difference in the armament panel, but not relevant to selective jettison) but there are some changes that are significant.

From the same table in the manual - the select jettison switch activates the jettison circuits and inhibits normal release. It doesn't mention whether it removes normal power to the station, but in the case of AIM-9 I would expect not, since they're "jettisoned" by launching them.

Has any tester been able to reproduce this yet? Is there any additional information I can provide?

What sort of AoA numbers are you testing this at? In my experience, at higher AoA (over 20 units or so) you statement seems to accurately describe its behavior in DCS - the ailerons become ineffective and rudder is necessary to control roll.