renhanxue

More specifically:

It's not really a cobra in the modern sense of the word - the Draken really isn't very capable in the high alpha/low speed regime and has a rather restrictive flight envelope. What you're looking at is actually a "controlled" (scare quotes very intentional) entry into deep stall by exceeding the allowed alpha limit, followed by an immediate recovery from it. The entire maneuver hinges on retaining sufficient elevator authority for just long enough to recover before the aircraft starts falling like a brick. The maneuver is very violent (you pull a lot of positive G's for a very short time), it's not controllable to any meaningful degree, and you also lose a lot of energy doing it. The Viggen is potentially capable of doing the same kind of thing (according to the flight manual, at least) but its much riskier there. The Draken predates computer aided design and its thick stubby wings ended up being quite overbuilt for its rated G limits, so it can actually pull this kind of thing off in exercises without too much danger to the aircraft.

That’s a neat rule of thumb for ballpark estimates, but it’s off by more than 10% at sea level even at ISA.

The generally accepted conclusion in hindsight seems to be that except maybe at the very tail end of the Cold War (later half of the 1980's), as long as E1 was at least mostly operational, a naval invasion was simply too risky to attempt. To make it work, there would need to be a preparatory phase first with extensive bombing (possibly nuclear) of E1's bases, and that would take some time. But dragging the situation out like that wasn't a bad use of E1 either; it'd give the army and the navy time to mobilize and prepare defenses (mine fields, etc), and it'd allow the fighter squadrons and ADA to take some small bites out of the Soviet strike assets as well, leaving less for later.

Very nice writeup, Farks! Regarding forming up the strike package, in the Viggen FB group a former A 32 and AJ 37 pilot related this anecdote (my translation): I'll see if I can find the original source comments.

The basic position calculation is just dead reckoning. The computer takes course and accelerations in all three axes from the ADI and autopilot, as well as temperature and air pressures from the air data unit, to calculate a true airspeed vector. Then it converts this to an estimated ground speed vector by compensating for the wind speed using either doppler radar-measured speed over the ground if possible, or forecast wind (as input from the data cartridge) if the doppler isn't working. Then it integrates this every 103 ms to continuously calculate the current position. The only kinda inertial components are the accelerometer gyros. Setting the land/sea switch (LAND/SJÖ) to sea mode when over water is advisable to help the doppler out (according to the manual the doppler spectrum tends to be shifted lower over sea and the sea mode is supposed to compensate for this - it also states that in level flight and with moderate waveheights the error is on the order of "a few percent"). The manual also states that the doppler will not work reliably at pitch or bank angles above 15° when in sea mode. If the doppler has failed to track for two minutes straight you should get a NAVSYST warning on the announciator panel. You can override the doppler by inputting forecast wind manually while in the air (input done on the ground does not do this) - input wind direction in degrees with three digits followed by wind speed in km/h with two digits in VIND/RUTA/MÅL IN, confirm with LS/SKU. Input wind direction 000° and speed 00 km/h in the same way to re-enable doppler measurement. You can also see what CK37 thinks the current wind is by going VIND/RUTA/MÅL UT - output is just like input (three digits direction in degrees, two digits speed in km/h) with the addition that the sixth digit is a - (minus) if it's using forecast wind or a 0 (zero) if it's using the doppler. 10-20km of drift sounds gigantic, though. Are you flying acrobatics the entire time?

Snabbresning = fast erect. For the main ADI, presumably. e: oops that was a few weeks ago

The SFI (flight manual for the real aircraft) says ADI alignment is done in two stages, starting immediately on main power on (or as soon as there is AC power from the generator, if ground power isn't connected). In the first stage, the gimbal arms are pre-aligned, which takes 32 seconds. The second stage starts immediately thereafter, automatically fast erecting the ADI for a maximum of 70 seconds (the minimum time is not stated). During the second stage the NAVSYST warning should be lit on the annunciator panel (or you might only get a "flag" warning on the ADI itself, unsure). None of the manuals or checklists mention having to wait for the ADI to align though so presumably it aligned fast enough in practice that you never had to wait for it. Keep in mind the Viggen's navigation system isn't really an INS - what's aligning here is just the course and vertical gyros. There is no inertial navigation in the conventional sense, although the nav system does use f.ex. course info from the ADI gyros.

The only way to turn nose wheel steering off is by losing hydraulic pressure in system 2. Would not recommend.

The scarf was (is?) a Thing in the Swedish Air Force, you got a silk scarf matching your squadron's color when you joined. Red = 1st squadron of the wing, blue = 2nd, yellow = 3rd. These colors are the same as the ones used in callsigns, so Martin blå = 132nd fighter squadron (13th air wing, Norrköping).

The switch label is accurate... for a JA 37. It's the same switch in the same place for both aircraft but on the AJ and AJS 37 it controls countermeasure release mode and is labeled as such, but on the JA 37 it's some backup radio transmitter mode setting (IIRC controls if the push-to-talk button on the stick should transmit on the backup radio or not, or something like that).

Yes. The reason they're so huge was IIRC an accident during air combat training where two Viggen collided because they lost sight of each other and/or mistook the orientation of the other aircraft.

The link to the PDF itself still works.

There are only really two "meaty" books on the Viggen and its development - Sven Stridsberg's Viggen and SFF's anthology System 37 Viggen. Both are unfortunately long out of print. However, SFF has now graciously made System 37 Viggen available for free in PDF form! Get it and read it ASAP. It's a collection of essays by a number of people involved with the Viggen in various ways - engineers, mechanics, pilots, air force higher-ups, etc - and it's pretty much the single best accessible source of info on the aircraft and its historical context.

Since I'm so awesome, I'll just take this opportunity to quote myself from a previous discussion on the same topic:

At the very end of the Viggen's career there were a handful of international exercises in which it participated. Don't think the AJS 37 ever got to do it though, I think it was mostly the JA 37 and the SK 37E.

Not much in the way of planes, but Flygvapenmuseum is only around two hours away by car. It's easily doable in a day trip, but, well, if you only have two days...

That's a misunderstanding. The terrain avoidance mode is the same, dark is a radar return.

I did, but it's still in limbo. It's "only" been like 8 months, so it's not quite time to email and ask if they've forgotten me just yet (they almost definitely haven't, these things just take forever and a half).

It's written from memory by an old Lansen pilot at least 30 years after the last time he did it, and he did say he didn't remember the exact timings. :)

O yea, that. I forgot about that one. I'll try to remember when I'm there next time (probably next week).

Well, without further ado... Enjoy.

It's everything you ever wanted to know about flying Drakens. That is, it's the Swedish Air Force fighter tactics manual from 1965, including how the Swedish data link system was to be used tactically, tactical radio terminology in Swedish, engagement ranges, mission profiles etc etc. no it's not viggen related, really, but come on now, it's awesome

Soon.

There's a reason it has illumination bombs, and it's not for supporting ground forces. Rb 04 strikes could of course be done in any visibility, but for the unguided munitions, you kicked it old school, that is to say in the exact same way as on the Lansen back in the day: (Source, mandatory reading) Tactics was exactly the same on the Viggen, just faster. One aircraft in the flight of four breaks off and uses the radar to toss the illumination bombs behind the target, the rest make a very precisely timed turn and arrive to deliver the actual strike just in time. It seems to have been a pretty spooky business.