nairb121

Yes, that is correct. I'm not disputing the stall AOA (in units) - the manual is very clear on that. The sources I've posted seem to indicate that the F-5 should be able to pull more beyond stall than we can currently, depending on CG position. The manual supports that the F-5 should have some degree of post-stall AOA capability (page 6-4): It's difficult to properly correlate units and degrees, since no source seems to use both, each using either one or the other. The only factor I've seen relating them is the stall AOA, which is stated in the Taylor/Skow report to be 23 degrees, and in the -1 manual to be 27-28 units - however, in DCS 27-28 units corresponds more closely to 20° AOA. See below, from my track attached in my original post. null Is it possible that the relation between true AOA (in degrees) and indicated AOA (in units) is slightly off in DCS, with the stall and maximum AOA being based on the incorrect indicated AOA and therefore falling short of the true values?

Yes, the numbers referenced in my post are true AOA in degrees, as reported by the status bar. The NASA and Taylor/Skow documents are both also measuring true AOA.

There's no independent bar selection, but it does switch from 1-bar to 2-bar depending on scope range selected. Azimuth will always be the full 90 degrees. Your main controls are the elevation knob, the range selector, the TDC, and the ACQ switch.

There's a mic switch on the throttle which should be used for this.

Isn't the reticle collimated, projected to infinity? Unless there's an issue with how that's simulated, seat position should have no effect on the reticle's alignment.

The F-5E in DCS, when clean, has an angle of attack at full aft stick of approximately 21° when gun ammunition is loaded, and approximately 25° when the guns are empty. Based on the public sources I've found, these are too low; capability should be approximately 30° (presumably with guns empty). The paper here https://arc.aiaa.org/doi/10.2514/3.45660 concerns the departure characteristics of the F-5E and the means by which an impending departure could be detected and the pilot warned. This section (found at the top of the second page) states that pitch acceleration follows stick position up to about 30 degrees, at which point further pitch up is prevented by the aircraft's aerodynamic stability. Fig. 7 also supports this - it shows time history of various flight parameters during an extended full-aft stick stall. The angle of attack can be seen as approximately 30 degrees for the majority of the time, further increasing to 40 degrees at the onset of post-stall gyration. (It should also be noted that the DCS F-5E shows little tendency toward PSG in this regime) An additional source for the F-5E's AOA capabilities is this NASA report regarding the development of the "shark nose" used in the F-5E and F-5F. https://ntrs.nasa.gov/api/citations/19790001876/downloads/19790001876.pdf . This report mostly concerns the F-5F, but also includes some F-5E data. Figure 6 shows flight data for 1g power-off stalls for the F-5E - the charts are more difficult to read, but they do show similar AOA tendencies of 30 degrees at full aft stick, and up to 40 degrees upon departure. I've attached a track in DCS attempting to replicate these tests by performing an extended wings-level 1g stall with guns unloaded. Upon full application of aft stick, the AOA remains between 25-26°, never approaching 30. F-5 1g stall test.trk Edit: I didn't realize the first document linked was incomplete; a full version is attached. F-5E_Depature_Warning_System2.pdf

I found a few relevant sections in the F-5E-34 manual (accessible at https://www.digitalcombatsimulator.com/en/files/1946809/) : From page 1-89, in the section relating to the Snakeye: From pages 1-119 and -120, in the section on the FMU-54/B tail fuze used in the Snakeye: And page 1-134, showing arming wire/lanyard installation for the Mk-82 Snakeye: There only seems to be one swivel and link, rather than two as used on typical GP bombs. If I'm understanding the diagrams and descriptions correctly, the swivel and link (if the station is armed) pulls the fin release wire, causing the fins to open. The tail fuze, if present, is linked to this wire and is also pulled. The nose arming wire is linked to the fins, and pulled out by their opening action. This is supported by the first excerpt, "As the retarding fins open, the noze fuze arming wire is withdrawn from the nose fuze". However, it seems like it would be possible to have an additional swivel and link connected to the nose fuze arming wire, which would be connected to the nose fuze arming solenoid. The manual makes no mention of this for the Snakeye, though it's similar to the arrangement used on GP bombs. It would have the effect mentioned though - if this was pulled, but not the swivel and link connected to the fin release wire, this would arm the nose fuze but not release the fins or arm the tail fuze. Maybe this is the setup used on the other Snakeye-equipped modules?

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