correct as-is Our W.I.P. Viper Too Fast?

[wilbur81]

Hey, fellas.

 

Many of you have probably enjoyed Hasard's YouTube channel (https://www.youtube.com/watch?v=riZYJ8lP3nE) as have I. I was watching his "Clean Viper Max Speed Run" video today and began to think that this would be a good time to test my suspicions that our current (albeit very W.I.P., O.B., and ever-improving) Viper is, frankly, too fast. Either because it's overpowered or drag isn't fully implemented yet. These suspicions began when I was being engaged by a Viper with 2 bags and 6 AMRAAMS and flying level (from a take-off start with full fuel) at Mach 1.5 and 36,000ft (see external screenshot). And yes, though I love and own the Viper (and have BBI's old 1:18th scale Viper hanging above me as I type), I'm one of those guys who's also been shot down from 25 miles away by a Six-AMRAAM-Two-Bags-toting Viper flying at Mach 1.6, so I'm not entirely unbiased about it's realism being accurate as possible when I'm at the wrong end of one.  It just seems like our early access, work in progress Viper needs some dialing back. But I could certainly be entirely wrong as the Viper is a beast and ED does their homework and then some. Anyway...

 

 I tried Hasard's Max Speed run to the best of my ability given the few details he gives in the video (you can find a nice write up about it with these details as well if you'd like to try it yourself - https://www.sandboxx.us/blog/this-is-what-its-like-to-take-an-f-16-to-the-absolute-limit/)
 

Details of his flight by his own account:

- 7000 lbs of fuel

- Clean jet, no pylons

- Climb up to 25K to begin test... then, Mil power at 25k ft to 0.95 m and then full AB

- Begin ramp up to 50K and, after achieving mach 1.4 , then back down to 35K

- He achieved M. 1.9 in a steepened dive

 

Now, I very much understand this is just his account, so this isn't necessarily mil-spec documentation (though he certainly speaks in detail about altitudes and speeds). I also don't know which motor he had (our GE or the Pratt & Wimpy) or how cold it was in South Korea that day, how steep his climbs and dives were, etc. With that said, my humble test has our DCS Viper quite a bit more powerful/fast (see screens for results and compare them to the video or article... and/or test the mission yourself and post your own results). Enjoy. 

HasardLeeTEST.miz

Edited February 1, 2021 by wilbur81

[TobiasA]

The top speed should be alright, top climbing altitude is also fine I think. The A model certainly won't do that, but the '50/'52 can even supercruise when clean. So I am told.

Rated top speed is in a level flight. And keep in mind you are not carrying a jammer with a high drag index. Pop the bags and zoom it goes.

 

https://info.publicintelligence.net/HAF-F16.pdf

We have the GE-129 which is the only model. And it is correctly modelled. Read page 1-42. Above Mach 1.4, putting the throttle to idle will still be MIL since the engine will have so much air flowing through- but this applies on the PW-229 so they did put a lot of research in the engine. See Page 1-46: "When retarding the throttle to IDLE above 1.4 mach, rpm may decrease up to 15 percent from MIL rpm. RPM then decreases with mach number until approximately 1.1 mach, at which time the engine decelerates to normal flight idle rpm."
So we do have the F110-GE-129, this matches the book on spot. And it's awesome, just look at 1-57 when that mach diagram ends at Mach 2.0. Which is the stated top speed in some sources.

The 129 has a whopping 29500 lbs of thrust, compared to the 23800 of the A version. That's quite some horsepower for the little F-16.

 

The deeper I look the more I think the FM isn't that far off- if any, given the available data.

 

 What I do think is that flutter should be modelled. There is a flutter analysis from 1977 on the A model airframe which can be seen here:
https://core.ac.uk/reader/42876251
I'd love to see flutter modelled. Visible for example here:

 

However, the Block 40's Dash-1 seems to say to not exceed mach 1.6 with the external stores apparently, which can be read here:

https://www.f-16.net/forum/viewtopic.php?t=16344

So it seems possible even on the Block 40 with a slightly less powerful engine.

 

So no, I don't think that the viper as it is now is too fast.

[wilbur81]

Good info.  

 What would you say, then, about Hasard's test flight results?

 

 

[Skysurfer]

It 100% is too fast. You can do M1.45+ at sea level far exceeding the operational 800KCAS / M1.2 limitation for said alt. Just lack of damage modelling and consequences. There are also no performance charts or data for said speeds - for a very good reason.  

Edited February 1, 2021 by Skysurfer

[TheBigTatanka]

A few current viper pilots have said the DCS F-16 is under powered in terms of acceleration, and appears too draggy.

I think ED has done a great job modeling some subtleties of the flight model, and you can see that by flying the HARTS maneuvers and seeing how closely the jet matches the real world examples. It has felt a bit underpowered to me though, based on my expectations.

As far as getting killed by a viper 25nm away -- that sounds normal. I shoot at 40nm and go out at 25.

Dances

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[wilbur81]

44 minutes ago, Skysurfer said:

It 100% is too fast. You can do M1.45+ at sea level far exceeding the operational 800KCAS / M1.2 limitation for said alt. Just lack of damage modelling and consequences. There are also no performance charts or data for said speeds - for a very good reason.  

 

Yeah, I'm mostly just trying to understand a). The test-flight of Hasard compared to what we actually have in DCS. It's possible, of course, that he was flying a small-mouth and not a GE-129. b). How accurate the current Viper's performance is with a full load of ordinance. To be able to exceed mach 1.55+ in level flight with two-bags and six AMRAAMS seems, well, incredible. But I have ZERO security clearance.

 

 

13 minutes ago, TheBigTatanka said:

 that sounds normal. I shoot at 40nm and go out at 25.

Dances


 

That may be telling.

Edited February 1, 2021 by wilbur81

[Bunny Clark]

It's pretty hard to make any specific comparisons without knowing which version he way flying. It may not even have been a C model, and it could have been a two-seater. It could easily have been a block 40, 42, or 52. The differences aren't only in engine type, but aircraft weight as well, which can easily throw off these results. 

[wilbur81]

35 minutes ago, Bunny Clark said:

It's pretty hard to make any specific comparisons without knowing which version he way flying. It may not even have been a C model, and it could have been a two-seater. It could easily have been a block 40, 42, or 52. The differences aren't only in engine type, but aircraft weight as well, which can easily throw off these results. 

for sure. You're right.

 

As to my other question about payload speed: I achieved Mach 1.5 in level flight at 35K ft. starting at m 0.90... all starting with full internal fuel, 3 bags, 6 amraams, and the TGP. Again, maybe the Viper really can overcome all that drag. If accurate, that's impressive to say the least!

 

Edited February 2, 2021 by wilbur81

[TheBigTatanka]

It doesn't surprise me at all that the viper can hit 1.5 mach level at that altitude and loaded. The issue is, it takes a long time to get that fast -- so it isn't tactically viable to wait until you are that fast (because your commit criteria is probably going to be 80-100nm) and you CAP in the mid-20s. So by the time you commit, get to expected contact range, meld, target/sort and shoot -- you are most likely down to 35-40nm and only mach 1.0. If you wait until you are closer (and faster) to shoot, you are inside MAR for any long-burn threat by the time your missile goes pitbull.

If guys are capping at 36K to start with, they are going to have issues with look down capability, not to mention the difficulty of holding formation in that thin air.

The eagle, or the Raptor, are true air superiority fighters, because they can get really fast on a commit by the time they hit shoot range, and this give their missiles more kinnematic energy, screwing up the bandits' timelines.

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[TobiasA]

vor 4 Stunden schrieb TheBigTatanka:

A few current viper pilots have said the DCS F-16 is under powered in terms of acceleration, and appears too draggy.

I think ED has done a great job modeling some subtleties of the flight model, and you can see that by flying the HARTS maneuvers and seeing how closely the jet matches the real world examples. It has felt a bit underpowered to me though, based on my expectations.

As far as getting killed by a viper 25nm away -- that sounds normal. I shoot at 40nm and go out at 25.

Dances

Sent from my Pixel 3 XL using Tapatalk
 

I think if the Viper is off, then it is too draggy on higher AOA's. It feels a bit like that. 

Depending on the altitude, the 40 miles number is a good rule of thumb if you have at least a solid 10k altitude advantage on someone heading towards you on angels 20.

Near 15 miles make it almost impossible to outrun the missile. 

 

Talking about Vne at sea level, the main thing that is missing is the punishment for exceeding it. Like blown blades. Also, the 129 has an overspeed protection iirc, that might kick in but I can't tell since I lack RL experience. 

After all, I think the FM is pretty good, and the only thing one could wish for is punishment for exceeding G or Vne like hung stores, flutter or even damage to the engine and a corrected lift on higher AOA's, especially on slow speed. 

[TheBigTatanka]

That all sounds legit Tobias. I believe the low altitude speed issue has to do with a limit on the canopy glass with heat from friction.

Here's the other thing..... Who is flying 800 knots on the deck? In formation, you don't want to get much above 450-500 so you stay a steady platform for your wingman -- and you'll only be at those speeds going IP-TARGET. Otherwise, you'll burn too much gas to get to your target. And in any kind of BFM, if you are above 450knots, your turn circle is measured in miles instead of feet -- and you are going to soak up a fox-2. If someone in DCS going that fast on the deck, maybe there should be some "punishment" but I just laugh when I see people flying single ship and crazy.

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[TobiasA]

Yes I remember some canopy issue. I also recall an accident with a lost Viper and a dead pilot in the gulf of Mexico due to overspeeding which broke the engine. 

 

But you are totally right. Who does that? Alone the insane fuel flow should worry you. Like you could lose a wing tank by small arms fire and still get further than that. 

I just think the punishment should be there for the sake of realism and for keeping people from exploiting it on PVP. The Viggen can have compressor stalls, it would only be fair. Power comes with responsibility, that is very true for the Viper in terms of hung stores for example. 

But that is currently nice to have, there are more important things on the module. 

 

You can't keep up any tactical formation on full burner either. And tacturns on angels 35 are not easy to do. 

[wilbur81]

"Who does that?"

 

Haha! You haven't spent much time on Growling Sidewinder's public server I guess.   But seriously, good thoughts and discussion, Tobias and TBT! 

[TobiasA]

vor 2 Stunden schrieb wilbur81:

"Who does that?"

 

Haha! You haven't spent much time on Growling Sidewinder's public server I guess.   But seriously, good thoughts and discussion, Tobias and TBT! 

Tbh I don't even know about it.

I don't even know how to start with MP in DCS but I don't want to hijack this thread. 

Thank you for the cool input and nice discussion

[SCPanda]

Just quit flying the Hornet (truck) and start flying the Viper (sports car) in BVR.

LOL just kidding.

 

Honestly, the Viper's FM is underpowered compare to the Hornet in terms of ITR and STR. The AOA is off during turning according to ED and other player's tests. So in BFM, Hornet can kick Viper's ass easily. Also, with DCS's current G-model, Viper pilots cannot utilize the jet's 9G turning ability and its advantage of having a inclined seat. 

 

Yes, the Viper is supposed to beat the Hornet in terms of speed and climbing. ED also marked this as "correct as-is" so I guess the Viper IS that good.

[wilbur81]

15 hours ago, SCPanda said:

 

 

Yes, the Viper is supposed to beat the Hornet in terms of speed and climbing. 

This is true... And the real Hornet bests the Viper in terms of nose authority, AoA, and low speed maneuvering.

Edited February 3, 2021 by wilbur81

[Spurts]

Ugh, the 800/1.2M sea level limit being brought up again...  In the previously mentioned HAF-1 a GE powered Block 50 will still be accelerating at 1/4G when at that sea level limit.  It is a placard limit there for thermal reasons.  It is NOT a power limit.  It IS a safety limit.  The PW motor would explode past that, don't know about the GE.  The canopy would also overheat to failure.

[TobiasA]

The HAF manual mentions an overspeed protection.

[SCPanda]

On 2/3/2021 at 10:39 AM, wilbur81 said:

This is true... And the real Hornet bests the Viper in terms of nose authority, AoA, and low speed maneuvering.

 

Yes it does...But Viper's FM is off and the jet is under performing. This is a FACT that ED has confirmed and they said they will tweak Viper's FM in 2021.

 

Also, I didn't compare Viper's nose authority, AOA, and low speed maneuvering with the Hornet's. All I said was Viper's AOA is off when turning, and the STR and ITR is not as good as they should be. In the real world, the Viper is equal to the Hornet in terms of BFM. The outcome of the dogfight depends on which pilot can utilize the advantage of his/her jet. 

 

Additionally, according to C.W. Lemoine, who has flown both the Viper and the Hornet. Hornet's ability to pull high AOA sometimes might not be a good thing since if you pull too much and cash your energy but did get the kill, you are stuck in a low energy state. However, Viper can just ease the pull and recover its energy very fast due to its superior thrust to weight ratio

[wilbur81]

51 minutes ago, SCPanda said:

Yes it does...

Well said!

[bies]

11 hours ago, SCPanda said:

Additionally, according to C.W. Lemoine, who has flown both the Viper and the Hornet. Hornet's ability to pull high AOA sometimes might not be a good thing since if you pull too much and cash your energy but did get the kill, you are stuck in a low energy state. However, Viper can just ease the pull and recover its energy very fast due to its superior thrust to weight ratio

 

I agree but one thing to add: C.W. Lemoine flown F-16C block 30, half ton lighter "fighter" variant with higher T/W than our block 50CJ.

Block 30 is universally praised by real life F-16 pilots as being better for close in combat than later heavier models.

 

And when it comes to max speed at low alt: according to pilots relations clean Viper with GE would go easily above the limit (power to drag wise), but the airplane would be destroyed at some point - engine comressor or canopy. This is not modeled in DCS F-16 yet.

Edited February 4, 2021 by bies

[Hodo]

The only issue with the Falcon is it doesn't have hung stores modeled.  Over G with bags on or bombs and they will get stuck.  

 

So far I think only the JF has that modeled.

[Blaze1]

On 2/1/2021 at 11:44 PM, wilbur81 said:

Yeah, I'm mostly just trying to understand a). The test-flight of Hasard compared to what we actually have in DCS. It's possible, of course, that he was flying a small-mouth and not a GE-129. b). How accurate the current Viper's performance is with a full load of ordinance. To be able to exceed mach 1.55+ in level flight with two-bags and six AMRAAMS seems, well, incredible. But I have ZERO security clearance.

 

 

That may be telling.

 

Hi wilbur

 

He was flying a PW-220 small mouth jet, because he mentions the five stages of afterburner.  The GE engines have a continuously progressive AB system and the PW-229 engine has eleven stages of AB.

Edited February 4, 2021 by Blaze1
Typo

[wilbur81]

9 minutes ago, Blaze1 said:

Hi wilbur

 

He was flying a PW-220 small mouth jet, because he mentions the five stages of afterburner.  The GE engines have a continuously progress AB system and the PW-229 jets have eleven stages of AB.

Nice! Good catch. 

[wilbur81]

7 hours ago, bies said:

 

I agree but one thing to add: C.W. Lemoine flown F-16C block 30, half ton lighter "fighter" variant with higher T/W than our block 50CJ.

Block 30 is universally praised by real life F-16 pilots as being better for close in combat than later heavier models.

 

And when it comes to max speed at low alt: according to pilots relations clean Viper with GE would go easily above the limit (power to drag wise), but the airplane would be destroyed at some point - engine comressor or canopy. This is not modeled in DCS F-16 yet.

 

Agreed on all counts, and good observation.  There's a nice little write up that pertains to the Viper vs Hornet 'debate' on the Fighter Pilot Podcast site by Trevor "Boat" Boswell. It's a good little read. Here's a pertinent excerpt, but the whole article is really worth the read:

 

Edited February 4, 2021 by wilbur81