Reputation from renhanxue - Page 4

renhanxue got a reaction from Belesarius in J35 Appreciation Station October 1, 2015

le epic meme face XD

Have a copy of a post I made a while ago:
Here are some words about the JA 37 intercepts of the SR-71 during the 80's. Most of the text is translated or adapted from the book "System 37 Viggen" (Flyghistorisk revy, 2009).
The JA 37 tactics development unit got started quite early on with working on a mission profile for intercepting targets at very high altitudes. The targets considered were the SR-71 Blackbird and the MiG-25 Foxbat; both types were capable of mach 3 at altitudes above 20,000 meters (65,000 ft).
Since the Viggen obviously wasn't fast enough to catch up to the target, the profile they came up with involved the intercepting aircraft meeting the target on a directly opposite course, with intercept vectors and combat control provided by ground-based installations over datalink and/or regular speech radio (in Swedish terminology, the air combat control system was known as "Stril", portmanteu for "Stridsledning och luftbevakning", which means something like "combat control and aerial surveillance"). This meant the JA 37's PS-46 radar would be supported by the ground-based Stril ones, since the intercepting aircraft couldn't catch the target on its own radar in time to climb and accelerate to intercept.
The tactics and armament systems were developed in the JA 37 systems simulator at Saab, with the simulator connected to Stril. For obvious reasons there were no opportunities to practice against our own aircraft in reality. The mission profile started with acceleration in level flight to mach 1.35 at 8000 meters (~26,000 ft). Then the nose was raised to 3-5 degrees above the horizon in order to climb while accelerating further. The maximum altitude was kept within the 16000 meter envelope ceiling mandated during training.
The USAF SR-71 recon missions were commonly known as the "Baltic Express". Usually, the SR-71's entered the Baltic at an altitude of about 21,500 meters (70,000 ft) about 80 km south of Copenhagen, accelerated to mach 2.98-3.0, continued eastwards and then northwards along the coasts of East Germany, Poland and the Baltic states, followed by a left turn westward, crossing the Baltic sea to the Swedish side just south of Åland, then another left turn southward and flying through the narrow corridor of international airspace between Öland and Gotland. Initially the left turn westward south of Åland was so wide that the SR-71's ended up violating Swedish air space, which led to a diplomatic protest which caused the SR-71's to slow down to mach 2.54 during the turn before accelerating to mach 3 again on the southbound leg. Between 1977 and 1988, 322 such missions were flown; in a few cases the mission was also flown in reverse.
Map of a typical SR-71 flight (note the times - wallclock time - noted along the flight path, the violation of Swedish airspace near the top and the Soviets running circles in the top right):

The intercepts would typically be done around the place that says "0910" on the route, or slightly north of it.
Simulator training on the mission profile started in Norrköping at the 13th air wing (one of the first wings to receive JA 37's; it had been equipped with them during 1981) for both pilots and air combat controllers. You couldn't know who ended up getting the intercept, so everyone was trained. The first real intercept opportunity came on October 26th 1982, when a pair of Viggens encountered an SR-71 for the first time. One of the pilots tells the story:

The second intercept occurred a week later, on November 1st, 1982, with another pair of Viggens from the 13th air wing:

Another intercept worth mentioning involved a group of three Viggens and occurred on January 9th, 1986. The group started southward from Norrköping with the intention of intercept training, but immediately after takeoff it was ordered to prepare to intercept a target that was suspected to be a SR-71. The group climbed to 8000 meters on a southeasterly course and then turned northward over the Baltic sea southeast of Västervik, forming up in a column. At this point the JA 37 had been equipped with the fighter-to-fighter data link, so the Viggens could share targeting data with each other, not just with the ground. All three aircraft conducted a simulated missile firing independently. The intercept started at 13:14 local time and was complete at 13:25; the intercept point was about 50 km west of Visby, on the island of Gotland.
The target was flying at an altitude of 21,500 meters at mach 2.9 and as usual attempted to jam the PS-46 radar. The Viggen group had had plenty of time to climb and accelerate, so when the lead and the second aircraft had passed the target the flight lead called to continue at maximum speed since the mach number at that point was around 2.0. The third aircraft did not reply, though, so the leader asked for his status. The answer was "I'm gliding". The third aircraft had suffered a high temperature engine stall. The engine had stalled briefly, the exhaust temperature rose and the warning light "EXHAUST TEMP." was lit. The pilot followed procedure and turned the engine off, and then restarted it when he descended below 12,000 meters. Having the engine stall at that kind of altitude was very scary since without bleed air from the engine, the cabin would lose pressurization within minutes. The entire group exceeded 18,000 meters of altitude during the intercept.
The fighter version of the Viggen really wasn't what you'd normally consider well suited to high speed/high altitude intercepts. It had fixed engine intakes, which meant it couldn't exceed mach 2 and it ordinarily had a ceiling of 16,000 meters, where its performance was decent for its time but not really comparable to that of purpose-built high altitude interceptors. Flying it at such high altitudes could be risky; the engine and the intakes were operating at the very edge of their capabilities and there was a passage in the flight manual that cautioned against "hammershocks" in the intakes that could possibly tear the aircraft apart if the engine stalled at high speed and high altitude. Nevertheless, in many cases it succeeded with intercepting even such a difficult target as the SR-71 anyway (over 50 successful intercepts recorded by the air force during the 1982-1988 period). The success can be attributed in part to the predictable flight paths but also to the aircraft's excellent data links, which were quite exceptional for its time and made it a lot more capable interceptor than it would otherwise be. Catching up to the target is one thing, but you also need to know where to find it.

renhanxue got a reaction from Zyklon in The Swedish AFV Thread: Not Just Strv 103s March 4, 2017