Stickler

According to the RL flight manual, when the compressor inlet temperature (T2) falls below +45°C, the maximum engine rpm is limited to prevent excessive mass airflow through the engine. The rpm maximum speed reduction starts at +45°C and is reduced until, at -54°C, the maximum rpm is approximately 90 percent. The engine also incorporates an exhaust gas temperature (T5) reset during military and full afterburner operation. This T5 reset occurs at the same point as T2 cutback, and reduces EGT at the same time that T2 cutback is reducing rpm. As can be seen in the attached track, even at a T2 of -40°C, maximum engine rpm remains 100% and I could find no evidence of T5 reset. I do not believe these effects are intended to be modelled (though I cannot be sure) so I'll leave this here as a low-priority feature to be implemented in the future. no_t2_cutback.trk

According to RL flight manual, a utility hydraulic system or double generator failure renders the variable bypass bellmouth and auxiliary air doors inoperative. Operation of an engine with an open variable bypass bellmouth and closed auxiliary air doors will allow engine compartment secondary air to recirculate to the engine inlet. During low altitude or ground operation, the temperature of the recirculating air may be high enough to initiate T2 reset. As seen in the attached track on the EFB engine page, switching off both generators after a hot spawn with the corresponding closure of the auxiliary air doors does not cause T2 to increase (T2 remained at OAT = 50°C for 3 minutes, I did not continue the test afterwards), and therefore T2 reset does not occur. Even though the game manual does not mention T2 reset/auto-acceleration as a possible malfunction, I was expecting auto-acceleration due to malfunctioning auxiliary air doors to be implemented since T2 reset due to high-speed flight seems to be accurately modelled. If auto-acceleration is intended to be modelled I recommend to check for a bug here; if it is not intended to be modelled, consideration should be given to model the effect as a low-priority item. no_auto_acceleration.trk

The question of whether the F-4E is supposed to feature G-breath audio was asked several times on Heatblur's Discord (most recently here), but never received a definitive response. Thus, is there supposed to be G-breath audio? If so, it currently does not work (I cannot recall if it ever did).

According to the game manual, the VOR lamp illuminates to indicate that the VOR system is ready and receiving. That is, a valid VOR frequency has been selected, a signal is received and the navigation knobs have been turned to VOR navigation. Conversely, the tooltip when pointing at the VOR lamp indicates that it has "no function". As seen in the attached track, even if the above prerequisites are met and good reception of the VOR frequency is confirmed on the HSI, the VOR lamp does not illuminate. I recommend to either implement VOR lamp illumination (my preference), or change the manual to read that VOR lamp illumination is not implemented. vor.trk

Attached as requested. battery.trk

Consider the attached track. Starting at 40000 ft MSL above sea-level terrain, I command Jester to scan the 0-10k block, resulting in an initial scan elevation of approximately -11°. I then disable Jester. Note how during the subsequent descent to 5000 ft MSL, Jester, despite being disabled, adjusts radar scan elevation to continue focusing on that altitude band, reaching 0° elevation precisely when the aircraft levels off at 5000 ft. While I think Jester should exhibit this behaviour when enabled, I do not think he should auto-adjust radar scan elevation when disabled. rdr_adjust_no_jester.trk

When sitting on the ground with only the engine master switches ON, according to the EFB, one can cause an electrical demand of 355 Watt with all consumers connected to battery and essential DC buses switched on. A 24 volt, 11 ampere hour battery should take around 44.6 minutes to fully discharge when supplying this demand. I just spent about 80 minutes on the tarmac in that condition using time acceleration and the battery was still not empty. Is battery depletion modelled?

According to all RL manuals available, the DC BUS caution light will illuminate when the main DC bus and the essential DC bus are disconnected, and specifically in case of a double generator failure. While I have not been able to deliberately cause a disconnect of the main DC bus and the essential DC bus that does not involve unpowering the essential DC bus completely, and there is currently no way to induce a double generator failure via the failures menu, my assumption is that switching OFF the generators after a ground start or while airborne is likely to be equivalent to a double generator failure. In that case, the DC BUS light currently does NOT illuminate; in fact, I have never seen that light illuminate at all unless during a lights test. Considering that in case of double generator failure in the air, all buses except the battery and the essential DC bus are unpowered, the DC BUS must be powered by either of these buses, otherwise it would not illuminate as per the manual. Since the EJECT light is powered by the battery bus, I assume the fire and overheat warning lights and the DC BUS light should be as well. I recommend the DC BUS light be checked for proper functioning.

With the help of the awesome EFB, I have been able to get close to what the underlying issue is: The battery, despite being a 24V battery, powers the battery bus, essential and main DC buses to 26 V, and voltage does not drop as the battery depletes since battery depletion does not currently seem to be modelled (see the in-game manual and this report). When disconnecting external power with the generators set to EXT ON, the voltage on the combined buses therefore never drops below 24.5 + 0,5 - 0 V, and the DC bus tie never opens UNLESS you use the battery bypass switch to force a disconnect, in which case the speed brakes and the auxiliary air doors retract as expected. It is noteworthy that when using the bypass switch that way and then switching it OFF again, the essential and main DC buses do NOT reconnect despite the essential DC bus reaching 25.5 +/- 0.5 V, even after the generator switches are simultaneously recycled. Conversely, when reconnecting external power, the DC bus tie closes WITHOUT having to do the simultaneous recycling. I would expect the DC bus light to come on instead in that case until recycling is accomplished (compare this report). Now, I have no idea to what voltage the battery powered the buses in the RL F-4E. As posted above, I suppose the voltage was probably less than 24.5 + 0,5 - 0 V since: If either the speed brakes or the auxiliary air doors were able to operate on battery power without external (or internal generator) power, there would be no need for the -1 warning. The operative equipment chart with battery power seems to include all equipment tied to the essential 28V DC bus, but none of the equipment tied to the main 28V DC bus, which likely indicates that the latter bus could not be powered from the battery. The manual only speaks of the battery powering the essential dc bus "for a period of time", not the main 28 V dc bus. As per the manual, "the dc tie control circuit is designed to disconnect the two dc buses during double generator failure so that loads from the main 28 volt dc bus will not discharge the battery". It is not immediately apparent from the electrical charts in the flight manual why manually disconnecting the generators from the bus system via the generator switches would cause the DC bus tie to open whereas removing electrical power by disconnecting the GPU would not. Specifically, there is no indication that the generator switches controlled the DC bus tie directly.

First of all, I really appreciate the new EFB feature. Good job! With regard to the original questions: The fuel quantities in the cells as per the EFB strongly point to a 68-495 fuel system, albeit without the tank depressurization switch. Open. Very low priority in my opinion. I was not able to attain the aircraft state depicted in the manual showing the wings as well as cells 5 and 6 empty but the remaining cells essentially full. I do not have access to sufficient RL material to determine whether this indicates a problem with the manual or the fuel system modelling. With regard to the additional question brought up, I could find no evidence that the fuel state as per the EFB or the fuel state indicated on the fuel totalizer is influenced by external temperature or air pressure in the game.

The cx function seems to be described in the respective weapon.lua at dcs-lua-datamine/_G/weapons_table/weapons/bombs at master · Quaggles/dcs-lua-datamine · GitHub, for example for the Mk-82 it's cx_coeff = { 1, 0.29, 0.71, 0.14, 1.28 }. I am almost certain one could reconstruct the actual formula used based on these coefficients, but I am too bad at math to do so or to even know for sure it would be possible. I do know how to datamine so I went the inductive route. Let me know if you figure out a deductive one.

OK, thanks, sounds reasonable. Without access to the full radar specs it is likely impossible to determine if increased radar reflectivity due to antenna elevation/focus and increased attenuation due to greater distances from the emitter factor into each other "correctly". More so due to DCS engine limitations.

Thanks Zabuzard, that was helpful.

They depend on the weapon. For the Mk-82, for example, you can obtain charts like the below (x-axis: Mach, y-axis: cx) from having the AI mass drop the weapons and determining/calculating cx for different Mach numbers from Tacview telemetry.

Compare the attached tracks. Both show me in an identical aircraft (airspawn with empty centerline tank) during AAR. Scenario 1 (AAR_EFB_wings): Spawn fuel 3725 lbs. The centerline tank starts filling up immediately upon contact. The internal wing tanks start filling up only once fuselage cells 1, 2 and 7 are full. Scenario 2 (AAR_EFB_wings_centerline): Spawn fuel 6155 lbs. Both the internal wing tanks and the centerline tank start filling up immediately after contact even though cell 7 is empty/still in the process of being topped off. Why is cell 7 being full an apparent prerequisite for the internal wing tanks starting to fill up in scenario 1, but not in scenario 2? AAR_EFB_wings.trk AAR_EFB_wings_centerline.trk

Thanks for the tip, however, MAP-PPI exhibits the same behaviour: For completeness' sake, I included MAP-PPI with circular polarization, but the issue is the same. Plus, MAP only has linear polarization IRL, so the picture should not change (I reported this as a bug separately): Before somebody asks: RDR 1-bar also apparently focuses its radar energy as seen above.

The attached track shows my aircraft at exactly 15 nm plan range from a discrete ground target and 3815 ft above it. The background terrain is completely flat and uniform (southernmost edge of Caucasus, over Türkiye). From trigonometry we obtain that the target is 2.4° below the horizon. 2.4° happens to be the radar depression below the horizon obtained when asking Jester to scan 7500 ft below the aircraft at 30 nm, which I command him to do. The target should therefore be in the center of the MAP 1-bar radar beam. Looking at the track and the below screenshot which shows the radar picture immediately before exiting the aircraft, we can see that from visual interpretation of the radar, the reflected radar energy seems to be highest at around 11 nm slant range from the aircraft, and not at 15 nm, as I expected. How can this be explained? null mbc.trk

The game manual (confirmed by the RL flight manual) states that during AAR, fuel can be delivered to the Phantom at a rate of up to 3900 lbs per minute. The attached track recorded on a standard day in a reference aircraft and the corresponding chart below show that the in-game F-4E can be refuelled with up to 4800 lbs per minute. Specifically, this is the case when refuelling either a clean F-4E (shown in track), an F-4E with external tanks and the ALL TANKS/INT ONLY switch set to INT ONLY (not shown in track), an F-4E with a centerline tank and the ALL TANKS/INT ONLY switch either set to INT ONLY or to ALL TANKS (not shown in track). In these cases, refuel rate will be 4800 lbs per minute until the fuel totalizer indicates approximately 5000 lbs. In cases 1 and 2, refuel rate subsequently drops to 4150 lbs per minute until the fuel totalizer indicates approximately 8500 lbs, then to about 830 lbs per minute until the end of AAR. In case 3, refuel rate subsequently drops to about 3900 lbs per minute until the fuel totalizer indicates approximately 8500 lbs, then to about 830 lbs per minute until the end of AAR. AAR_fast.trk

In the F-4E, the position of the elevation strobe indicates the antenna elevation angle. In RDR 2-bar mode, the strobe will jump at the end of each azimuth scan. As shown in the attached track, in the game, this jump only occurs in STAB OUT. Regardless of whether the strobe jumps or not, the actual scan takes account of the RDR 2-bar setting, i.e. the jump can be observed on the radar screen. It's just that the elevation strobe remains stationary except in STAB OUT. elevation_strobe.trk

Already reported:

While it may be true that the lack of coincidence of the markings is an issue in the real F-4 as well (I don't have a real aircraft immediately available I could use to check), it is certainly not a parallax issue. Regardless of head position, the "zero" elevation mark of the radar symbology is always at the same 1-2° positive elevation scale position (in NORM mode, STAB OUT is a different story of course). On the contrary, in the rear seat, the misalignment can be eliminated with an appropriate head position.

One might add that with the radar scanning along the horizon (elevation +- 0), the elevation bar is not coincident with the 0° mark on the elevation scale in the front cockpit.

Thanks for the clarification. Returning to the main question at hand, why does AGC gain out the contact in 100 nm and 200 nm range, but not below these settings?

Why does AGC gain out the contact in 100 nm and 200 nm range, but not below these settings? On a related note, I understand AGC to be a feature of track mode (see here). During Manual Search (e.g. when holding the first-stage trigger and not attempting lock-on with the second-stage trigger), we are not in track mode which implies that ACG is not active. I should have mentioned (but this is also visible in the track) that I do not press and hold the first-stage trigger ON the contact, but centered horizontally and vertically on the radar scope with target dead ahead.

The attached track shows a B-52 straight ahead at 45 nm. Note how its radar contact is clearly visible in MAP and BRST modes in the 50, 100 and 200 nm range scales as well as when holding the first-stage trigger in MAP mode in scales up to and including 50 nm. Conversely, the contact is not visible when in MAP mode in a greater scale than 50 nm when holding the first-stage trigger. first_stage.trk