Insane climb performance

Discovered what must be a FM bug, we were testing the full performance climbs of several DCS a/c, and to our surprise the Viggen absolutely outstripped every other jet reaching an astounding 20+ km (67+ kft in its climb). F-14, F-15, F-18, Mirage, MiG29 etc., qall were left in the dust, nothing can currently touch the Viggen in the climb.

Something is off.

Did you collect any data? Did you measure time or rate of climb?

I mean Wikipedia lists it as having

Service ceiling: 18,000 m (59,000 ft)

Rate of climb: 203 m/s (40,000 ft/min)

The Viggen is a tremendous interceptor and will reach 40K feet in under a minute. 28K rated engine.

No matter how unrealistic it feels for you, not a single developer will look into something based on feelings. The least you could have done is make some simple comparisons with other aircraft (actual numbers) and maybe pull up some performance charts or something. I thought somebody with a post count like that must know better, but this looks more like utter laziness to me.

With a constant M 0.9 climb profile even a clean aircraft should top out at around 15500m. To get higher than that you need to zoom climb. The climb performance is very good below 10km but falls off quickly after that.

I mean Wikipedia lists it as having

Service ceiling: 18,000 m (59,000 ft)

Rate of climb: 203 m/s (40,000 ft/min)

 

The Viggen is a tremendous interceptor and will reach 40K feet in under a minute. 28K rated engine.

While he didn't mention all that, we know that he knows. The situation has a smell and should be looked into.

Sorry but I simply didn't have time to post a video of it, I just thought I would raise the issue so that it would be looked into because something is definitely off as the Viggen shouldn't be outstripping all the other jets mentioned in the climb like that.

All aircraft were clean and at 100% fuel btw.

Alright here's a quick comparison between the F-15C & AJS-37 starting a climb at approx. 1,100 kph, full fuel & clean. Now watch what happens:

rC-DZRy5uf4

Note that the Viggen not just keeps its speed in the ~40 deg climb, it actually accelerates much of the way. Then suddenly at around 14.5 km height this super performance tanks, and the aircraft rapidly slows down, but not before reaching over 18.5 km in height, a good 3 km higher than the F-15C.

Alright here's a quick comparison between the F-15C & AJS-37 starting a climb at approx. 1,100 kph, full fuel & clean. Now watch what happens:

rC-DZRy5uf4

 

Note that the Viggen not just keeps its speed in the ~40 deg climb, it actually accelerates much of the way. Then suddenly at around 14.5 km height this super performance tanks, and the aircraft rapidly slows down, but not before reaching over 18.5 km in height, a good 3 km higher than the F-15C.

At around 15 km, the Viggen's afterburner flames out, so that explains the sudden decceleration you're experiencing.

Valkyries assist the Viggen during climbs.

Valkyries assist the Viggen during climbs.

First stage A\B is provided by Huginn and Muninn, second stage by Freya's cats and THEN it's Valkyries...

:D

First stage A\B is provided by Huginn and Muninn, second stage by Freya's cats and THEN it's Valkyries...

 

:D

Haha :thumbup:.

Or Tanngrisnir and Tanngnjóstr (the goats pulling Thors chariot) hauling Mjolnir to its date.

Well I trust the issue is obvious to anyone :)

Well I trust the issue is obvious to anyone :)

Not to me, I never take the Viggen above 500ft AGL :D

Well, these special aircrafts can surprise many their performance. Like even today the Harrier holds climb speed record to 9000ft (~2700m), and only after that does a F-15C get faster climbing.

After all the Viggen is equipped with an airliner engine, designed for high speed performance at lower altitude can as well perform greatly at thin high altitude air as an interceptor variant.

The reason why you get two engines in aircraft instead one, is not redundancy but thrust-weight performance (F-14 designer words). You put two smaller engines and get more thrust for the total weight, than what a single less weighting engine could give.

And the Viggen engine is huge but heavy.

One F100-PW-220 F-15c engine gives 105.7 kN wet thrust, but weights 1467kg

dry.

One Volvo RM8 engine gives 125 kN wet thrust, but weights 2,350 kg dry.

So one huge heavier engine gives more than one light small, but when you can put two smaller and lighter together, you get far better performance for the space and weight.

Compare full empty weight of F-15C, it is 12700kg and Viggen is 9500kg.

Mig-23MLD in empty weight is 9595kg, and engine is capable for 127.49 kN wet thrust while weights 1760 kg as empty.

Now design aircraft to overcome drag etc, and you might be better with two little weaker engines than one more powerful.

The RM8(A) produces 115,6 kN of thrust, the one we have on our Viggen.

The RM8B however does produce 125kN of thrust, and is used in the JA37.

Sorry :smartass:

I just hope they will look into this soon because performance like that is hardly a simulation of the real thing :)

Funny, I just noticed this last night as well. I was able to climb above 70,000ft with full fuel and no weapons. I was supersonic for nearly the entire climb too.

I also noticed on the way back down pitch control was wonky. Slight stick back would hit 8g almost immediately, and slight stick forward would peg it the other way.

Obviously none of the above was scientific. The last time I had an issue like this was with the mig29, when you were able to climb halfway up to the moon. They fixed that though.

I haven't tried climb testing, though there was a time when I broke off one wing at high speed. To my surprise, this caused the Viggen to accelerate, well beyond Mach 2 if I recall, while at 60 or so AoA. This was a while ago so I don't know if this still exists, or even if it was found and addressed already, but if not there may be some odd things hidden in the Viggen's flight model.

Now you stop accelerating at Mach 1.72 no matter what attitude/power. Definitly worth a look.

This is the exact reason the Viggen is an amazing inetrceptor in DCS currently. You can be on the deck in a valley, see someone contrail and just shoot up vertically, stay supersonic and reach him.

SU33 will run around circles and all the way to space vs the Viggen .. best I can get the Su33 is 125,000ft

SU33 will run around circles and all the way to space vs the Viggen .. best I can get the Su33 is 125,000ft

Question is not altitude, but speed to altitude.

Guys this is not a competition, it's about the FM obviously being broken, which is kind of a big problem for a study flight simulation.

They're still tuning up Tomcat FM, my guess is that when this task is finished they will drop an eye on this