renhanxue

At longer ranges, chaff should be quite effective - the seeker is fairly "dumb" and won't realize the target is obscured. However, if the missile establishes a lock on the real target and manages to close the distance a bit before the chaff is launched, the antenna lobe will be so narrow that the missile won't "see" the chaff. There's probably nothing that stops the missile from locking on a low flying helicopter, but unless the helo is at exactly the missile's cruise altitude (or below it), it won't hit or detonate. (In reality, that is. In game, no idea.)

The general rule is that if it's older than 40 years* then it shall be declassified... if you ask for it. If it's newer it can be declassified if you ask for it, if the authorities concerned consider it non-sensitive. Almost nothing will be declassified unless someone asks for it. The main thing in the JA 37 that could be sensitive still is the fighter to fighter data link, since that same link was later developed into the Gripen to Gripen data link that supplements Link 16. There could also be multilateral agreements protecting information about the Skyflash, for example, and when I got the AJS 37 manual they didn't want to give me the chapter on ECM (although that seems to have been "just to be safe" - they did tell me that if I really wanted it I could just ask and they'd bring it up with the Air Force, since they couldn't declassify it themselves at the national archives). I haven't actually attempted to request declassification of any JA 37 stuff though. *40 years is the general catch-all term. Stuff related to military intelligence is 90 years (was 70 until very recently), "military-scientific research" is... 70?, and "the fixed defenses of the realm" (fortifications, bunkers etc) is 120 years.

Because this is still a 60's aircraft at its heart. Getting accelerometers precise enough for navigation purposes was very complex, expensive and above all bulky back then, and the Air Force did not at all like the readiness penalties imposed by having to sit around and wait for half an hour and wait for the gyros to stabilize either. 60s INS alignment really could take that long.

Not quite in the same detail, but the flight manuals do cover the RBS 15. I've been thinking I should do a similar writeup but haven't gotten around to it. I think they were upgraded.

I've requested the declassification of a tactics compendium for strike Viggen units from the early 1980's but it's not come through the process of declassification yet. In the works, though, and I'll post it as soon as I get access to it.

The AJS 37 does not have a bitchin' betty. It just beeps and boops at you.

Definitely no hyphen, but space vs no space is debatable - I've seen both in official-ish contexts, but no space seems to be the dominant form.

Nope. The JA 37 got a newer engine (RM8B) that was considerably better at high alpha etc but since it had an extra compressor stage the entire airframe had to be lengthened by about a decimeter to fit it. The AJS 37 was effectively an avionics upgrade only and they didn't want to spend too much on it since the Gripen was just around the corner.

I'm pretty sure I've read somewhere that the original rb 04's targeting "computer" was still powered by mechanical cam discs and that kind of voodoo. Ever read about the mechanical ballistic computers on the last battleships in WW2? Kinda like those. The 04E though I believe at least had vacuum tubes and stuff - most of the electronics were upgraded when it was adopted for service on the Viggen. edit: s1i-dnAH9Y4

On the AJ, yes, only two. On the AJS all six pylons (other than the centerline) are Sidewinder capable.

I originally wrote this as a post in the "big" Viggen thread but decided to break it out now that we finally have a subforum so people won't have to dig through 3000 posts to find it. I've made some minor corrections and updates, nothing really significant though. Robot 04E (with "robot", abbreviated "rb", being military Swedish for "missile") was the AJ 37 Viggen's signature weapon: a radar-guided, sea-skimming, fire-and-forget anti-ship missile, developed from the rb 04C which had originally entered service in the 1961 on the A 32 Lansen. The E version entered service in 1975, with 315 missiles produced. Let's have a look at how it works. Rb 04C or D on a A 32 Lansen. Missiles on the assembly line at the air force's Central Aircraft Workshops in Arboga. First, some background on the doctrine and use case that shaped the design of the missile. The Swedish armed forces expected the Warsaw Pact to attempt to secure a beachhead on the Swedish coast with a D-Day style invasion: a massive fleet of hundreds of ships with surface combatant screens protecting a core of various landing craft. The AJ 37's raison d'être was to attack a fleet like this. The rb 04E was mainly intended to be used against the screening combat ships, since if their AA was silenced the Viggens would be able to go to town on the vulnerable landing craft with less expensive weapons like bombs, autocannons and unguided rockets. In order to achieve saturation of the defenses and a reasonable chance to actually sink mutually supporting surface combatants, the plan was to deploy at least four but preferably six or more full squadrons in each attack wave (one squadron in the air was two flights of four aircraft, so six squadrons would be 48 aircraft). Since the plan involved launching up to close to a hundred missiles at the same time (or slightly less - some aircraft would be carrying countermeasures instead of missiles), getting the missiles to spread themselves out between different targets and not collide with each other or lock on each other was a very real concern, which will be apparent when we get into discussing the seeker. Onwards to the technical details! The missile's about four and a half meters long (14 ft 9 in), weighs around 625 kg total (1378 lbs), has a shaped charge warhead that weighs about 200 kg (441 lbs) and is powered by a solid rocket motor that produces a nominal thrust of 195 kp (1.9 kN, 430 lbf) for a nominal burn time of 65.5 seconds (can vary between 60 and 75 seconds depending on propellant temperature). The control surfaces are pneumatically actuated. The seeker is a frequency hopping monopulse radar with a parabolic antenna located under the radome in the front of the missile (the text "TRYCK EJ HÄR" on the radome means "do not press here"). The antenna sweeps horizontally only, 28 degrees to each side. The missile cruises at an altitude of 10 meters above sea level, which it maintains by the use of a radar altimeter. The AJ 37 can carry two rb 04E's on the inner wing pylons. When pre-flighting the missile, the mechanic had a panel with five switches and a knob available to him for programming the missile - there really isn't much the pilot can configure from the cockpit. The panel looks like this: The switches are intentionally only labeled with numbers for opsec reasons - the seeker electronics were highly classified and the conscripted flight line mechanics were not allowed to know anything about how it worked or what the switches actually did. Switch 1 ("balkläge") is the missile's position on the aircraft; V (vänster, left), C (center) or H (höger, right). The centerline pylon © was initially planned as a possible launch position on the AJ 37 but the electronics to actually launch the missile from there were never implemented. The rest of the switches we'll cover when we get to the functionality they affect. The missiles can be launched one by one or both together - in the latter case there's an automatic delay of about two seconds between the two, to avoid collisions. Targeting is simple: the pilot simply points the entire aircraft at the desired target, guided by the head-down radar screen, on which either a PPI or a B-scope is presented together with a wind-compensated aiming line (wind speed is taken from the aircraft computer, where it is either doppler calculated by the radar altimeter system or taken from the weather forecast as input during pre-flight procedures). The presentation looks like this: B-scope and PPI, respectively. The number 60 shown in the bottom right means that the range of the display is set to 60 km. The two short, curved lines on the PPI represent the ranges 12 and 24 km respectively, while the line marked "raktframlinje" is the wind-compensated aiming line. Originally, the 12 and 24 km lines represented minimum and maximum firing ranges for the missile, but at some point the procedure was improved to calculate the engagement envelope dynamically based on air pressure, temperature and speed of the launching aircraft (later manuals recommend a max launch range of about 20 km). The pilot can select if the missile's seeker should be in single ("ENKEL") or group ("GRUPP") targeting mode. In single target mode, the missile will simply lock on the first detected target. In group mode, the target selection process is more involved and we'll get back to it in a little bit. The missile can be launched at altitudes between 50 and 425 meters above sea level and airspeeds between Mach 0.7 and 0.92. The aircraft's radar does not need to be radiating to launch the missile, since the targeting is done just by pointing the aircraft the right way. In fact, the missile can be launched completely "blind" - this was particularly desirable on the Lansen, which did not have a radar in every aircraft. The flight lead could do the radar thing and the rest of the flight just launched when he did - a tactic that was also technically usable on the AJ 37. Once launched, the missile is completely autonomous and can no longer be controlled in any way by the launching aircraft. When the launch signal is given, the missile activates its internal batteries, releases its gyro from being slaved to the aircraft's attitude gyros, unlocks and pressurizes the aileron actuators, and when the batteries have reached full power (after about 0.6 seconds), it separates from the aircraft. 0.7 seconds after separation, the elevators and rudders are unlocked and pressurized and the missile immediately starts diving at an angle of about 7 degrees. About 1.1 seconds after separation, the missile starts yawing either 2.5 or 7.5 degrees to either the left or the right - which direction and by how much is determined by the position of the knob (marked 6, "kurstillskott") on the switch panel on the missile. After 8 seconds, the missile returns to the launch course. The reason for this is to separate the missiles horizontally. When the missile's radar altimeter detects that the missile has had an altitude under 120 meters above sea level for more than 100 milliseconds, the automatic 7 degree dive stops and the missile instead follows a descent profile that takes around 10 seconds to reach its cruise altitude of 10 meters. Missiles launched from the right pylon ignite their rocket engine when descending below 130 meters, while missiles launched from the left pylon ignite it upon reaching the cruise altitude, to further separate them in time and in altitude. When the cruise altitude is reached, the seeker starts scanning for targets; the scan area (and lock envelope) is shown above. When a possible target is detected, the seeker activates a function called "three-view logic", which means that the ranging function continues seeking forward about 80 meters. Then, the antenna sweep is reversed and the ranging seeks about 250 meters backwards, then the sweep is reversed again and the ranging seeks about 300 meters forwards. If the seeker gets a return again during the first or second reversed sweep, the target is considered valid. If no return is received during the first or second reversed sweeps, the target search continues. On the other hand, if the seeker gets another return immediately after the first indication, caused by the size of the target, the three-view logic function is blocked and the seeker accepts the target immediately. When the seeker has locked on a target, the range to the target is monitored. The range should be decreasing, since the missile is approaching it. If the closing speed is too low, for example because the seeker has locked on another missile flying in the same direction, the missile releases the lock and starts a new search. The seeker will not lock on targets that are located such that the missile cannot be maneuvered to hit them, either. In group targeting mode, the seeker will assume that the target ships are traveling in columns, and can be programmed to lock on a target in the first, second or third row as seen from the attacking aircraft, using the target selection switch (marked 5, "målval") on the switch panel on the missile. In order for the missile to lock in group mode, two or more targets have to be detected in the same range sweep, and they have to be a maximum of 2700 meters from each other (this number looks arbitrary, but it's just about 1.5 nautical miles). In other words, from the point of view of the missile, the targets have to be directly in line with each other, along the antenna lobe. In order to allow for at least some flexibility in the line up, the seeker performs a fictional widening of the antenna lobe by copying detected targets and considering them for the next range sweep as well. This is all perhaps best explained with a picture: The "angle jump" function, which can be enabled on the switch panel using the switch marked 4 ("vinkelhopp") makes the missile skip the first possible target it sees and lock on the next one instead, if one is found before the antenna sweep reaches the end position and turns around. The missile also has an additional targeting mode, called "active + passive", which can be selected on the switch panel (switch marked 3, "följemod"). When this is selected, the missile has fallback targeting mode that is effectively home-on-jam - it will attempt targeting as normal, but if it detects it is being jammed, it will lock on the jammer after one full horizontal radar sweep has been done. While locked on the jammer (passive targeting mode), the antenna is kept pointed at the signal source and the missile tracks the bearing to it - tracking range obviously isn't possible. The range search stays active during the passive target tracking though, and if a target is detected in the jammer's direction, the missile will lock on that. If the jammer stops transmitting, the missile will keep going "blind" for two seconds; after that it resumes active targeting. Rb 04 seeker unit, "apparat 642". This is for the older rb 04D version though (used on the A 32 Lansen); it's a continuous wave radar rather than the monopulse design used on the rb 04E. This photo was previously captioned incorrectly as being a rb 04E seeker unit. EDIT 2025-06-23: third time's the charm, right? This is a rb 04E seeker, as originally captioned. I was told it was actually for the 04D a long time ago and didn't question that, but if you look closely near the bottom of the photo you can see the manufacturer's nameplate, which reveals it was made by Svenska Philips. That company made 04E seekers but not 04C/D seekers (those were made by AGA). References: image source in high resolution, and Arboga Elektronikhistoriska Förening. The seeker keeps the missile pointed straight at the target until it is less than 4000 meters away, at which point the missile starts accounting for the target's speed and leads it. The seeker keeps tracking the target until the missile has closed to 250 meters from the target. At that point, the missile switches to a terminal mode - the seeker is deactivated, making the missile blind, and the warhead fuzes are armed. The missile is not intended to actually hit the target - the warhead is a shaped charge that is focused downwards, so it is supposed to be detonated above the target. There are three different proximity fuzes - one magnetometric, one temperature-sensitive and one based on the radar altimeter, which triggers on the sudden altitude change when passing over the target. There are two proximity fuze modes, selected with the switch marked 2 ("zonrör") on the switch panel - in mode 1, only the radar altimeter is active, while in mode 2, any two fuzes both giving the detonation signal is required. Presumably, mode 2 is for use in rough seas to prevent accidental detonations from high waves. Additionally, there is also a contact fuze in the nose of the missile, which detonates it after a small delay if it should hit the target directly. The terminal mode has a timeout on it - if the warhead hasn't detonated when the target should have been passed, the seeker is re-activated and simply locks on the first thing it sees (disregarding the single/group target selection and any previous considerations). In summary, I find the group mode to of questionable utility since it requires the targets to line up almost perfectly, but I guess they did what they could to try to get the missile to be able to work against large ship formations. In the single target mode though the missile seems to be a pretty nasty piece of business for 1975, especially considering the radio silent mass usage doctrine and the fact that very few aircraft needed to actually radiate to enable a launch. The main weakness was probably that there were so few missiles purchased - about two missiles per AJ 37, total. It is also interesting to note that the missile's targeting is completely autonomous and does not rely on input from the aircraft in any way whatsoever - every launch is a "mad dog" (missile is fired without any control over its target selection). Better be sure there's no friendlies in the area! In the Viggen's operational context this made perfect sense and the air force and navy coordinated to agree on a line beyond which the Viggens were free to engage anything on the surface, but in other contexts this might've been a problem.

The AJ and AJS 37 only have a "pseudo-inertial" system. The system is based on dead reckoning, that is it continuously calculates the aircraft's position based only on time elapsed and airspeed (while correcting for wind speed, either forecast wind as pre-flighted into the computer or wind measured by comparing airspeed to speed over ground as measured by the radar altimeter system). The upside of this is that you never need to wait for INS to align before takeoff. The downside is that it drifts quite significantly. It's not so bad at all if you're flying in a straight line with the radar altimeter on, but if you start maneuvering it can get sorta confused pretty quickly. To compensate for this you occasionally need to take "fixes", that is update your known position by the use of some recognizable terrain feature. You can either take a radar fix (measure the distance and angle to the feature in question) or an optical fix (press a button when you fly over it). On the AJS 37 they added a height map database that will try to correct your position automatically by fitting your estimated position and the radar altimeter measured altitude against the height map, but the devs mentioned in the reddit AMA that this of course only works if you're flying over terrain with some recognizable height differences...

try my post history ;V

petition to move this thread to the shiny new subforum

Flight manual just says "don't launch above 500m AGL". No idea why. Yep - you were not supposed to be able to tell from the paint if you were looking at a fighter or a strike aircraft.

The JA 37 F13 wing tribute with Top Gun music that was posted earlier, rehosted by the creator on a site that probably won't block on copyright grounds.

While I'm flattered, I'll have to confess that I do not actually know everything about the Viggen by heart (yet). You're remembering right though - I went to look it up, and in short, the main wing spar suffered from a design flaw that caused unexpected cracks. After being subjected to sufficient stress over a period of flying it would eventually succumb to metal fatigue and break, which resulted in the entire wing snapping off. After the two crashes in quick succession in 1975 the entire fleet was grounded for months until they figured out what was going on. The pilot in the first crash in 1974 wrote this about the event in a Viggen group on Facebook: Also from the Facebook group, an article in Ny Teknik from 1976 that explains what happened in detail:

Squadrons were dimensioned for keeping one flight of four aircraft in the air or at highest readiness 24/7. The flight of four was the normal tactical unit, but for most missions the squadron would operate two flights at once. This required at least 16 pilots, and there were 108 AJ 37's manufactured for six squadrons, which gives 18 airframes per squadron (so really, 16 plus two spares to account for crashes and other write-offs during the service life of the aircraft). I think tail numbers were initially assigned based on the last digits in the aircraft's serial number but that soon led to conflicts and aircraft were reassigned between wings and got new numbers and so on, so that convenient relationship was often broken. Tail numbers were assigned on a wing level btw and there's no way of telling which squadron an aircraft belonged to based on the tail number. Numbering was not sequential either. Example: the only flying AJS 37 today is "Gustav 52" (7-52), which has serial number 37098 (one of the last AJ 37's manufactured). No relation in that case and I know for a fact that F7 did not have all tail numbers between 1 and 51 assigned.

No, I think it's gonna get declassified no problem, E1 hasn't been a thing for over 20 years and neither has the anti-ship missile spam doctrine. It just takes a long time for the poor overworked archivists to get around to looking at stuff.

Still waiting for declassification of the 80's strike squadron tactics stuff, requesting more stuff isn't going to make it go faster.

I didn't translate it, no. For some reason (Austria possibly?) there is an official English translation. If I wanted to translate 500 pages by myself I wouldn't have picked the wrong version of the aircraft to translate :V Basically what RaXha said.

For the linguistically impaired, I proudly present Aircraft JA 37 flight manual, volume 1, chapter 1 - the unclassified part of the flight manual for the JA 37C, in English. It's the air superiority version, not the strike version we're getting, but many things are similar and there is no English flight manual for the AJS 37 so you gotta take what you can get. See my post in the documentation thread if you want to read my complaining about what goes into making these.

It's good that you ask that right now because I finally got done with PDF-ifying the English version of the JA 37C flight manual (the unclassified part only). It's the wrong version of the aircraft - air superiority, not the strike version we're getting - but many subsystems are similar or even identical in some cases. You people better appreciate this one because for some dumb reason I got it into my head that previous PDF's weren't pretty enough, so I went through the entire thing and manually perspective-corrected almost every single one of the five hundred pages. :| Seriously, it's a pain. You start with this: It's not straight at all and I didn't hold the camera right above the paper so there's keystoning (top of the paper appears narrower than the bottom) and stuff. So out comes the geometric distortions tool and you fit this blue rectangle to the edges of the paper (or to the text, just make sure stuff lines up straight): You end up with this, which of course isn't entirely straight anyway but urrrgh I can't be bothered to get it pixel perfect and it's better than it was. Now repeat this for five hundred pages and yeah, it takes a while.

peep my post history for all the best charts and graphs and discussions thereof it's me, i'm chartman

People tend to steal the clocks out of combat aircraft to keep as souvenirs. Nope. What we're looking at here is originally an early 70's maritime strike aircraft with limited multirole capability, designed for short field operations (it is equipped with a thrust reverser) and high speeds at very low altitude. The original armament was a radar-guided anti-ship missiles (rb 04E), Mavericks (rb 75), pilot-controlled missiles similar to the AGM-12 Bullpup (rb 05A), unguided rockets, unguided bombs, autocannon pods and Sidewinders (rb 24). It can also carry flare/chaff and ECM jamming pods. The version we're getting though was updated with two new weapons in the early 90's, namely the newer anti-ship missile rb 15F and the bk 90 standoff submunitions dispenser (basically a guided glide bomb that covers a large area in cluster submunitions). This version never got any radar guided air-to-air missiles, though. It has pretty good thrust to weight ratio, easily does Mach 1.1 at sea level (it is in fact quite easy to accidentally overspeed a clean aircraft in level flight at sea level) and can reach Mach 2 at high altitude, but if you're ever above 50 meters AGL for any extended period of time you're probably doing something wrong. It is however fairly "short legged" and is not capable of in-flight refueling. For a more extensive summary see RahXa's excellent thread.