Disintergrating during supersonic manuvers

[WelshZeCorgi]

I confused how you're supposed to handle the aircraft, because it's designed to fly very fast at very low altitudes, but if you need to make a hard evasive manuver, say in my case, to avoid hitting a tree that you thought you weren't going to run into, you immediately disintergrate and die.

 

Is that a bug or are you supposed to be really gentle with her when she's flying supersonic?

[Art-J]

Uhm..... How about specifying which airplane you're writing about exactly. Might be a good start for a discussion :D.

[WelshZeCorgi]

Welp, this is not the right subsection, can I get this moved to the viggen forum?

[Zabuzard]

I'm not sure why exactly you experience such problems. My Viggen is pretty easy to handle.

 

You should use autopilot or trim to trim the aircraft for a level flight at all time. As soon as you go supersonic the Viggen has a tendency to fly nose down to the ground (at least for me). You can easily counter that. Always make sure to trim.

 

In general you don't fly supersonic with the Viggen all the time, just close to it (mach 0.9). Weapon employment is usually done between mach 0.8 and mach 0.95.

 

By using no afterburner you reach about mach 0.8. With first stage you can hold about mach 0.9. Third stage for supersonic.

I approach target AO with no afterburner, hit stage one shortly before attack and after release I go full afterburner to get away at supersonic speed.

 

So you only need supersonic while flying away from the AO, only for a short time. You are supposed to manually fly the aircraft at this point, full attention to the area in front of you. You can't effort looking around or heads down at this stage. After you escaped the enemies you go back to sub-sonic speed (stage 1 or no afterburner) and can again easily fly with autopilot on.

 

Also, flying low doesn't mean to be extremely close to the trees. You should keep 20m safety to the trees in good, extending to 100m in bad visual conditions, maybe 200m safety when flying at night.

Edited March 1, 2018 by Zabuza

[Kozality]

I tend not to crank too hard in the Viggen since the engine can be subjected to compressor stalls at high AoA. I don't know where this point is exactly, but generally speaking I try not to exceed 15 degrees if I can help it, both for those reasons and because it bleeds off so much speed.

 

I have noticed that the pilot model in the Viggen is such that there's no gradual black or red out like there is in say, the F-5E, so if you pull too many Gs at once, then your screen can go immediately black (with disintegration into a hill usually following. =P ) Is it possible that this is what you're seeing?

 

If not and the aircraft is actually coming apart, then my guess is that you're pulling too sharp an angle and the air frame couldn't handle it. The jet isn't fragile per se, but it is a thin wing and while it does supersonic easily, it's not meant to be a dogfighter. So gentle, low AoA turns are preferred.

 

Hope that helps!

[probad]

of course this is what happens when you firewall the throttle and barrel around at m1.2+ on the deck. at 600knots ias you are pushing against a ridiculous amount of air when you try to maneuver, and it's doubly bad for the stol-friendly wing of the viggen.

because it's designed to fly very fast at very low altitudes

'very fast' is a relative term when flying at near stall speeds for fuel efficiency is common in the military. medium to high subsonic is fast enough when you're skimming the treetops. note when you go in for an attack run you accelerate to ~.8-.9 mach and the obvious implication that you cruise below that.

 

realize you have been misled by stupid general knowledge authors who regurgitate sensationalist phrases without understanding what they mean.

Edited March 1, 2018 by probad

[renhanxue]

'very fast' is a relative term when flying at near stall speeds for fuel efficiency is common in the military. medium to high subsonic is fast enough when you're skimming the treetops. note when you go in for an attack run you accelerate to ~.8-.9 mach and the obvious implication that you cruise below that.

 

realize you have been misled by stupid general knowledge authors who regurgitate sensationalist phrases without understanding what they mean.

 

I don't disagree, and going supersonic at low altitude was not really standard procedure or exercised often in the Viggen as far as I know. Low altitude flying at high subsonic speeds over fairly long distances was common though. Just getting your type rating on the Viggen as a fresh cadet right out of flight school (before you started tactical training at all) required a couple of exercises in low altitude navigation flights with a flight instructor in the back seat. First a few lessons at economical speed (roughly 550km/h IAS), but also at least one stretch at M 0.8 at 50m AGL.

[Horns]

I confused how you're supposed to handle the aircraft, because it's designed to fly very fast at very low altitudes, but if you need to make a hard evasive manuver, say in my case, to avoid hitting a tree that you thought you weren't going to run into, you immediately disintergrate and die.

 

Is that a bug or are you supposed to be really gentle with her when she's flying supersonic?

 

The G-limit for the Viggen is 6G peacetime / 7G overall, and it's easy to hit that when you accelerate at afterburner 2 into a weapon release, hit afterburner 3 and evade. I had a few mid-air explosions for reasons I couldn't figure out until I started watching the accelerometer and was ready to relax my turn if I approached the G-limit or a blackout began.

[outbaxx]

How many g were you pulling when it brake?

The viggen has some limitations to how many g it’s possible to pull att different altitudes and speeds, but at mach0.8 at low level it’s possible to pull 12g and that is above what the airframe can take.

But I don’t know what it would take to get there, I guess a fast, full aft pull could do it?

[pyromaniac4002]

The behavior is intended. As stated previously, the G-limit is 6 or 7 G. Since the Viggen has no fancy fly-by-wire setup to proactively inhibit your tendencies to destroy the airframe, you can easily maneuver to induce G well outside the intended limit. At supersonic speeds, especially at low altitude, the G-onset is particularly violent and can surpass the limit much faster than you might be used to in high-subsonic.

 

Just have to learn to tame your pitch inputs at high speed. Keep an eye on the G-meter while your maneuver around and try to keep it at 6 G or lower.

[Nealius]

I've been whipping around with 6G turns, low level, supersonic with no issues. I just let off the stick a little when I hear the airframe rattle.

[F900EX]

If your going Mach 1+ and decide to pull a very hard turn the aircraft will explode...lol