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I think that's based on a misreading of the original Swedish flight manual (SFI) for the real aircraft, or it's based on documentation I don't have access to. Here's the relevant passage from the SFI (SFI fpl AJ 37 del 2 kap 1 sida 21): All the normal search modes use a horizon-referenced coordinate system and the antenna elevation angles are explicitly stated to be relative to the horizon. However, note the very last sentence, after the table - in both air-to-air mode and in terrain avoidance mode, the angles stated are explicitly said to be relative to the aircraft x-axis, not relative to the horizon. Note though that this is the original AJ 37 SFI from 1975 so things may have changed later on. I don't have access to a later version of this part of the flight manual though.

Wow, what an undertaking! Amazing work! Super happy someone has the energy to do this.

Procedures for the real aircraft permit but discourage takeoff in mil power, noting that the acceleration is poor and the rate of climb low, and as such even with a long runway available environmental factors (such as wind and temperature) and the presence of any obstacles beyond the end of the runway must be considered carefully. If the afterburner is used, the thrust level must be above the middle of zone 2 - in other words, takeoffs in zone 1 and the lower half of zone 2 are prohibited. The SFI doesn't specify exactly why, it just mentions something about the safety systems that handle afterburner flameouts. As far as I know the usual thing to do was takeoff in max zone 2 when a full length runway was available, and max zone 3 for short takeoffs (on e.g. road bases like the BAS90 800 meter strips) and when carrying heavy payloads. Short takeoff is a special procedure though with its own set of rotation speeds, and the procedures also explicitly say to throttle up to max zone 3 with brakes applied and only letting go of the brakes early if the aircraft starts to skid. Overspeeding the landing gear is mentioned as a concern but as far as I understand it it's mentioned just to remind the pilot not to delay gear retraction. Basically, obey this illustration from the aerodynamics compendium: "Use afterburner, fool!"

That's scans of the official air force magazine (the title literally translates to "Air Force News"). It was published 4-5 times a year between 1960 and 2003. There's a number of interesting articles in there but as an offical propaganda outlet it's not always the most useful source, and it's usually pretty thin on the sort of interesting details nerds love to see. Also, that page only has some articles scanned. Here are scans of every issue 1960-2003: https://www.aef.se/Flygvapnet/Tidskrifter/FV_Nytt/FVN_oversikt.htm

There is a thread about turning the AJS 37 into an AJ 37 here:

Given the way the SFI describes it, it must absolutely move within each zone. Elgon does not translate to just "electrical", it's a very specific technical term (now long out of use, though) that translates to "synchro", and specifically I think it refers to a synchro-transmitter. That's effectively a very simple analog angle sensor, and given that it's explicitly mentioned that the sensor is mechanically attached to the nozzle via a pulley, I'm quite certain this is a very analog instrument that just reads the rotation of the pulley directly and rotates the indicator needle to match. There's nothing in the text that indicates there's any form of quantization going on here. I don't know exactly how the nozzle moves within each zone, though. e: well, as for that last question, it's right there in the manual. Page 141 in the PDF (flik 9 avsnitt 3.2.4.3). I'm not going to post or translate the whole thing but as far as I understand it, the area of the nozzle opening is continuously regulated by a hydromechanical calculator, so yes, it makes a great deal of sense that the indicator is an analog instrument. In fact it seems to me the same pulley system that drives this instrument is also used by the fuel regulation system. See also section 3.2.9.2 which goes into more detail - it's explicitly stated there that the nozzle opening varies with the throttle level within each afterburner zone. I also seem to have already pointed to this section in this thread almost exactly 4 years ago... time flies, huh?

I don't understand what you're trying to say. For a clean aircraft, yes, the diagram ends at VNE before thrust=drag is reached, so we don't know exactly what the thrust-limited top speed actually is, or even if there is another limit other than available thrust (I don't think there is, but as you say, we don't know that). For an aircraft with payload, this is not the case - there is a known top speed (where drag > thrust) and it's below VNE, and we can see this from the diagrams. Hence when Rossmum said that he's seen aircraft doing 1600km/h IAS at sea level with external payload, I responded that I can't see how that could be possible in reality, judging by the data available.

What? I just posted a thrust-drag diagram that clearly shows even the JA37 not having enough thrust to reach its VNE at sea level with the lightest loadouts listed. Just follow the line marked 1 in the diagram and you'll reach T=D well below M 1.2. Or just extrapolate where the line marked 0 (clean aircraft) is going and it's pretty obvious that you'll run out of thrust just above M 1.2/1450 km/h IAS even then. I can easily see 1500 km/h being possible with a clean aircraft and you can probably do a bit better than that on a cold day even. With any payload at all though you're gonna get limited by drag below that.

Yeah, doing 1600km/h on the deck with external payload seems extremely unrealistic to me, there's no way I can see it having enough thrust to do that. Clean maybe, it's at least conceivable, but with payload? Can't see it happening.

Not by very much. The JA37 only has maybe 5 kN more thrust at M 1.1 at sea level. Thust-drag diagrams below. The main advantage of the RM8B is that it deals better with high alpha and is less susceptible to compressor stalls in general. AJ 37: JA 37: See this thread for most of the original Swedish flight manuals, where these performance charts are taken from.

Triple posting, sorry about that, but it's relevant. In the book System 37 Viggen, Kenneth Nilsson (longtime Saab employee, head of the applied aerodynamics department 1992-2001) relates the following story regarding work he did at Saab in the early 1970's studying the feasibility of beating a few FAI records with the Viggen, in the hopes that it would help it on the export market. My translation. edit: to be clear, I think going much beyond Mach 1.2 at sea level in an AJ37 is probably unrealistic, but I have never seen anything that indicates that engine, intakes or airframe in general would give up the ghost if you exceed 1350 km/h IAS. The only sort of related thing I know of is that in 1978, during development of the JA37 and the RM8B, the first prototype aircraft (37-8) was lost due to an engine fire caused by overheating issues in the lubrication system at high speed and low altitude, and this did lead to temporary operational restrictions for all Viggens for a while. This problem was fixed though, at great expense, and all RM8A's were modified with this fix as well and the restrictions were lifted afterwards. The flight manual sections that discuss restrictions, stability and behavior in various flight regimes do not mention any particular risks related to overspeeding at low altitude at all. The closest thing is a mention that roll authority is reduced at M>0.98 at altitudes below 2000 meters because of elastic deformation of the wing. I'd bet that the restriction to 1350 km/h IAS at low altitude is as much for airframe and engine longevity as anything else. For one thing in the real aircraft any intentional load factor < 0 G is forbidden, not because it'll make the aircraft fall apart, but because it causes a lot of airframe stress and reduces lifetime.

The F-111 is from the same time period as the Viggen and is limited to Mach 1.2 at sea level for the same reason hilmerby mentions (skin temperature). The F-111 has equipment for warning about skin overheating, though, and the Viggen does not. There is nothing magical about neither of these aircraft, nor their engines.

There is no such part of the manual to my knowledge. It just lists VNE as 1350km/h IAS on the AJ37, 1450km/h IAS on the JA37. The JA37 has a slightly different engine with an extra compressor stage that makes it more resistant to compressor stalls and it has a few percent more power, but is otherwise extremely similar to the AJ37 in most ways relevant to this issue. I believe that the aerodynamics compendium discusses some issues with available pitch authority/load factor at very high dynamic pressures because of limitations with the amount of force the hydraulics can exert on the elevons, but as far as I can recall it doesn't really go into much detail. JA37 does have a lot more pitch authority available throughout the entire flight envelope, as an aside. Another concern pointed out in the aerodynamics compendium is that the aircraft decelerates extremely quickly from supersonic speeds at low altitude when engine power is reduced. When the dynamic pressure rapidly falls so do the elevon deflection angles required to achieve a particular load factor. While the Viggen isn't fly-by-wire it does have a system that attempts to keep "stick force per G" at least in the same neighborhood throughout most of the envelope, and in a situation where the dynamic pressure is quickly reduced this system has to react very quickly. The problem is though that it really can't do that - it's a pretty primitive system and the pitch gearing can take 15 seconds to move from supersonic to subsonic mode, while the aircraft is capable of decelerating faster than that. There is no time limit for the afterburner listed in the declassified flight manuals for the real aircraft. If an operational restriction for time limits in zone 3 has ever existed I've never any evidence whatsoever for it. Presumably because you'll run out of fuel before you could realistically run into problems. Perhaps hilmerby knows more than the manual though.

Yes, exactly. In level flight the aircraft isn't actually level with respect to the horizon, it's always somewhat nose-up, and so the radar beam points slightly up as well. I don't know why they did it like this on the real aircraft because it seems it removes some margin of error that you would otherwise have, but as far as I understand the SFI that's how it works.

On the real aircraft, switching to TA mode sets the "neutral" antenna elevation (that is, the elevation that you get if the elevation knob is centered, in its middle snap position) to 0° relative to the aircraft X-axis, but since you have some positive alpha in level flight, your attitude is somewhat nose-up, so that ends up showing obstacles slightly above your actual flight altitude. In normal A1/A2 modes the neutral antenna elevation is actually slightly negative relative to the aircraft X-axis, between -0.5° and -3° depending on range setting and whether the altitude is above 600 meters or not (more negative at short range settings and at altitudes above 600 meters, there's a table in the SFI if you're really interested). For reference the elevation knob has a range of +/- 10°. The antenna elevation knob adjusts the elevation relative to this neutral position, so switching modes or range settings changes the actual antenna elevation a bit even though the knob position stays the same. That's all I know, I think. edit: oh, one more thing: in A2A mode the neutral elevation is +1.5°.

In reality, you would not be able to use the navigational computer at all in most of the areas on the maps currently available or announced for DCS (the exceptions being the western half of Caucasus and the small part of Normandy that lies east of Greenwich). The reason for this is that on the real nav computer, you can enter the longitude and latitude in any order, and it'll autodetect which is which. It can do this because it comes programmed with the restriction that longitude must be greater than 0° but smaller than 40°, while latitude must be greater than 40° but smaller than 90°. If you're east of Sochi-Adler, west of Greenwhich or south of Madrid, you better have brought a paper map and your dead reckoning A-game, because the computer is completely useless to you. Not that you would have been entering latitude/longitude manually all that often in reality though, the computer came preprogrammed with plenty of common Swedish landmarks and airfields accessed via the REF codes. They're input via the same entry mode on the data panel as the lat/lon coordinates (REF/LOLA, remember?) so that's why the seemingly pointless latitude restriction of 90° is there - the computer knows you're inputting a REF code rather than a coordinate if the first digit is a 9. On the JA 37 I think they reduced the max latitude to 85° to make room for more preprogrammed points, though.

"Stigning med max släckt" = climb at max dry thrust "Plané med flygtomgång" = descent at flight idle "Planflykt distansekonomisk" = distance-economical level flight "Kvarvarande bränsle %" = remaining fuel in percent "Tid i minuter" = Time in minutes Vi = indicated air speed (in km/h) Basically this chart tells you how far you want to climb to get the most distance out of your fuel. You want the dashed lines (remaining fuel) to go as far to the right on the chart as possible (you want as go as far as possible with as much remaining fuel as possible). Looking at the chart you can easily tell though that if you want to go a long distance this means that you climb to about 7000 meters with max dry at 675 km/h IAS or M 0.9, and then you stay there at whatever thrust level keeps you at M 0.9, and then you descend at flight idle, again at 675 km/h IAS or M 0.9. If you do this for as long as you have fuel you'll cover almost 1700km and it'll take you about an hour and 50 minutes. That's all the chart tells you.

Right, only two rb 75/rb 05 too.

No, the cartridge is a 1990's thing, there was no way you could fit that much memory into something that small in the 1960's. The original ferrite core memory for the CK37 in all its glory was a box roughly the size of a microwave oven that weighed something like 15 kg. This contained 8192 28-bit words, or about 28 kilobytes in modern units. The data cartridge has 8 megabytes of storage powered by a 3,5 V battery. The entire TERNAV system is on the data cartridge, both the altitude database and the TERNAV program itself. Oh and I forgot one thing, you can't carry the U22/A pod on the AJ 37, and even if you could, you can't do ELINT missions on the AJ 37 either because the RWR data is saved to the cartridge, not to the pod or to the CK 37. As an aside, how do you load flight plans into other aircraft that are contemporary with the AJ 37? I don't think I've recalled hearing anything about things like data cartridges for the F-14, for one.

Maverick is OK, it was integrated on the AJ 37. Rb 74 is out though, you're right on that part. In practical terms I think that should be it, I can't think of anything else off the top of my head that's relevant to DCS. Technically you shouldn't use the data cartridge either and just manually enter the flight plan yourself, but that's just pointless self-flagellation IMO.

The TRÅD "screw" is actually a transmit button (push-to-talk). When the aircraft is parked on the ground, the flight line mechanic can hook you up to both his own headset and to the air base's wired communications network, "slingan" (assuming you're on a Swedish military air base that has that system, of course). To talk to the mechanic you just talk into the helmet mic - the connection to the mechanic headset works just like a telephone. To transmit on the wired network though (that is, to talk to ATC, an intercept controller, your wingman, or whoever else is hooked up to the local loop without breaking radio silence), you need to press and hold TRÅD. Most of this isn't really relevant to DCS of course since wired communication local communication isn't modeled or even meaningful - radio silence isn't exactly a thing. IIRC a dev said somewhere they made TRÅD open the crew chief menu instead even though it's unrealistic. Don't remember the details though. TRÅD just translates to "wire" btw. SM-omkopplare means something like "send/receive switch" (SM expands to sändning/mottagning).

I can't point to a specific doctrinal answer to that but my guess would be that guided weapons replaced them. The 1961 air force tactics manual for strike squadrons has a table of recommended weapon options against various targets on page 26. The heavier bombs (mb, minbomb, bomb with little or no splinter effect, as opposed to sprängbomb) are recommended as the first-hand alternative for use against: Small ships such as MTB's, minesweepers, escort ships and small cargo ships Radar installations and missile control systems Air base ammunition depots Runways Railroads, railway stations and rolling stock Bridges Harbours and harbour equipment Army FOB's etc For many of these the 120 kg splinter bombs are a secondary or equally good alternative. Many of the others are point targets like bridges, piers, ammo depots or small ships, where the rb 75/rb 75T/rb 05 would probably be preferred. What remains then is basically runways, and I guess the air force didn't consider that important enough of a target to keep the heavier bombs around.

Most books about military aircraft (and tanks, etc) consist to some degree of made-up nonsense presented as fact. This is a good example of that. While there were 250, 500 and 600 kg bombs for the A32 Lansen, that (and its bombs) had been retired for 15 years by 1993. To my knowledge the Swedish Air Force has never used a 120kg bomb with the designation m/63 either, so heavens know where that came from. If it doesn't cite any sources, disregard it. If it does cite sources, look them up. Even experienced writers make mistakes.

Nobody actually works on the Viggen full time as far as I understand it, and in fact they all have other full time jobs outside of heatblur on the side (source: swither on reddit). It's better to think of this as hobbyist software and expect support accordingly. Still, as far as bug handling goes, having bug triage status exclusively in someone's head isn't a great way of communicating. People who put time and effort into writing bug reports are not just customers asking for support of the product, they're also doing some level of QA/product improvement work that would otherwise have cost the company money. Even if you can't or won't actually take any action on the report, it should at least get some minimum response. Even unpaid volunteers on github usually manage this. Privately, while I appreciate the module and the fact that it got made, I have serious doubts about the sustainability of this kind of hobbyist-commercial business, especially when it comes to something like software that needs constant support. I learned the hard way to not mix work with hobbies. It's not for me to judge though.