investigating Takeoff rotation is too slow

[Cyborg71]

5 hours ago, RogueSpecterGaming said:

Thats just you not holding the nose at 13 degrees AoA. I've consistently gotten to 95-100 kts with 2xtanks, 2x 120s, 2x9, 2x WWPs. With a slick jet I can get all the way to 70-75 knots.

I will try that. 

Slick. 13 degrees. 75 knots. Every time. 

Thank you.

[skywalker22]

Mover's words 8 months ago on this topic.

[BIGNEWY]

4 minutes ago, skywalker22 said:

Mover's words 8 months ago on this topic.

and adjustments were made.

[TobiasA]

vor 4 Stunden schrieb BIGNEWY:

and adjustments were made.

Didn't read that in a changelog, but then, it wasn't a placebo effect. Nice 

[RogueSpecterGaming]

I found the problem and will post everything tomorrow. Everyone, please sit tight.

[VarZat]

3 hours ago, RogueSpecterGaming said:

I found the problem and will post everything tomorrow. Everyone, please sit tight.

Looking forward to it

[RogueSpecterGaming]

Ok, I've finally had time to look at this stuff. Let me breakdown everything I found and observed. This is going to be a bit long so bear with me.

Let's start with the loadouts. The pilot taking off in the real-world video had: 2x AIM-120B, 1x GBU-12, 1x GBU-38 (on BRU-57), 1x Litening TGP, 2x Wing tanks. With max fuel his weight before startup would've been 36,718lbs

--NOTE--
In the real-world video you posted the first F16 seen has one GBU-12, one GBU-38, one Litening TGP, two AIM-120Bs, and two tanks, while the jet taking off has the same loadout but has the GBU-38 as a single-by on the BRU57 Smart bomb rack, a pretty common occurrence. In DCS we can't do that so we will stick with the one-by GBU-38 on the WWP, not too big of a change. Also, the weights are relatively close to the same.

Your loadout was: 2x AIM-120C, 2x GBU-12, 1x Litening TGP, 2x Wing Tanks. Weight before startup 36,815lbs.

Charlies are heavier than bravos. That gives us a weight difference of 97lbs. (48.5lbs per wing)

Another factor for weight though, is the real-world pilot didn't start off on the runway with full fuel like you are doing. He burned some sitting there starting the jet, getting the systems ready, and taxi meaning he probably took off with a fuel weight of about 11,019lbs vs your fuel weight of 12,113lbs. Depending on certain factors he could've burned anywhere between 1,100lbs to 1,500lbs of fuel. So, accounting for that we will go with the middle and say he burned 1,300lbs bringing his new weight to around 35,418lbs.

So now we have both weights factored.
Yours: 36,815lbs
IRL Video: 35,418lbs
--Difference in weight = 1,397lbs

Let's get our numbers now (All numbers are rounded to the nearest ones).
For a 10 Degree pitch
Yours: Rotation Speed = w/AB 164 w/o AB 169 | T/O Speed = 179
IRL Video: Rotation Speed = w/AB 160 w/o AB 165 | T/O Speed = 175

For an 8 Degree pitch (increase takeoff speed by 8 percent)
Yours: Rotation Speed = w/AB 178 w/o AB 183 | T/O Speed = 193
IRL Video: Rotation Speed = w/AB 174 w/o AB 179 | T/O Speed = 189
Only going to do AB takeoffs

You can see for the 10 degrees pitch your numbers were just a bit off.

Now, let me talk about what I noticed in the video, because this will be important later.

The real-world pilot is at Balad AB which has an elevation of 144ft above MSL (judging by the background he is taking off from runway 30) vs you, taking off from Batumi which is only 33ft above MSL, but that isn't too much of a factor here. Now, if we take into account that in early October, which is when this video is uploaded the temperature would've been around 98 to high 80s. But giving the chances the video was upload immediately is very slim meaning this was most likely shot in June to August time frame meaning the temps would've been around 100 to 115 degrees. The runway temp would've been around 160-180 degrees (based on real world flight line experience as a maintainer at Nellis AFB, the ground gets super-hot on the flight line). So, you got to take that into account for engine performance. Can't really tell what the winds were but I will just put a 2-knot wind in since judging by the trees I couldn't really see any movement but I'm sure there was some type of wind that day across the runway. I made a mission with these parameters: Iraq Takeoff Example.miz

And last but not least, probably the biggest factor in all of this, is what he does at the end. The 45 degrees vertical climb. Because he did that and judging by how he took off, I can tell he did an 8-degree pitch instead of a 10-degree pitch. You can tell because he stays pretty low before starting the climb. With that he had a whole (if I'm right about his weight) 13 knots on you when he started his rotation.

This is where it gets interesting. I watched your track in slow motion countless times and here is what I noticed.
You started to rotate at 164. This is the speed you initially started pulling the stick back. So, your horizontal stabs were not fully deflected yet.
At 169 your horizontal stabs were fully deflected which started your rotation.
Takeoff was at 197 for both wheels. At 194 you were kind of taking off with a roll, so you didn't have both wheels off the ground yet. The controls indicator showed you applied a slight roll to the right when pitching. Obviously, those numbers aren't what you were looking for.

Now let's get to my tracks because this is where it gets good. I also did this on the Caucasus map for those who don't have the Iraq map.

Replicating the real-world video as close as possible.
In my first track Iraq 10 degrees 156.trk
I started pull the stick for rotation at 156 and had full horizontal stab deflection at 161 which started my rotation. I achieved takeoff at 185.
In the 2nd track Iraq 10 degrees 160.trk
I started to pull the stick for rotation at 160 and had full horizontal stab deflection at 162 which started my rotation. I achieved takeoff at 186.
In the 3rd track Iraq 10 degrees 161.trk
I started to pull the stick for rotation at 161 and had full horizontal stab deflection at 165 which started my rotation. I achieved takeoff at 187.

That was all with using the speed on the HUD. I then decided to test the speed using the external view. I did one take.
My rotation needed to start at 154 in the HUD which would be 161 on the external cam. So, I pulled at 154 and had full horizontal stab at 160 in the HUD, which started my rotation. I achieved takeoff again at 186Iraq 10 degrees 154 in HUD.trk

Having tested the 10-degree pitch numerous times, I then moved onto the 8-degree pitch. Remember 8 degrees = Rotation Speed = w/AB 174 | T/O Speed = 189
1st track I started pulling the stick at 170 and had full stab deflection at 174 which started my rotation. I achieved takeoff at 189. Iraq 8 degrees 170.trk
2nd track I started pulling at 171 and had full stab deflection at 177. I achieved takeoff at 190. Iraq 8 degrees 171.trk
3rd track I started pulling at 171 and had full stab deflection at 176. I achieved takeoff at 191. Iraq 8 degrees 171 2.trk

These three tracks show the problem. The F16 in DCS cannot do a 10-degree pitch and achieve calculated numbers. It can however hit or come close to hitting the numbers for the 8-degree pitch. It should be able to do both.

I provided a track from an external view as well to compare with the real-world video doing an 8-degree pitch, and I roughly found the location of where the person was standing when recording. You will see it closely replicates the real-world video. Don't take control, I move the camera into position. Iraq 8 degrees external view.trk

Done on Caucasus:
8 degrees - takeoff was 189 Caucasus 8 degrees 189.trk
10 degrees - takeoff was 185 Caucasus 10 degrees 185.trk

I even went a step further and tested out Mover's loadout, which was a pretty similar loadout to what I had during my incentive ride. And I can confirm that it still needs a bit of tuning in this area for the Viper. It is so close to being on point.
Same results:

10 degrees Caucasus 10 degrees dif lo.trk
Takeoff speed = 159 | rotate w/AB at 144
Pulled back at 141, full deflect at 147 w/ t/o at 166

8 degrees Caucasus 8 degrees dif lo.trk
Takeoff speed = 172 | rotate w/AB at 157
Pulled back at 153, full deflect at 159 / t/o at 172

I concluded that no matter the speed, with this loadout or a lighter loadout, and going for 10 degrees, that I would takeoff ~10 knots faster than what the calculated takeoff speed is.
An 8-degree pitch and flying for those speeds was way more consistent. After watching real world videos in slow motion and watching my tracks in slow motion and analyzing every little detail I almost thought it was the scheduling of the LEFs but came to the conclusion that those are operating correctly every single time. WOW comes off and the LEFs actuate accordingly. So it isn't that.
I now suspect two things could be the problem: low engine thrust, or too much drag against the aircraft when the nose comes up.
The drag seems like the more probable cause as there is no issue when going for 8 degrees. You are going faster essentially pushing past that drag because you have the speed to do so. Whereas, going slow and aiming for 10 degrees the jet just doesn't want to get up until it is faster. Almost as if the 8 degrees speed is the only speed the jet can get off the ground with.

The reason I suspect the engine is because when holding the brakes and running the engine to 90rpm there should be a brief moment where the brakes hold but quickly slip due to the amount of thrust. This is something that is noted in the -1 as well and is noted to not push past 90rpm when holding brakes, and to come off the brakes as soon as the jet moves on its own.

It can be one of them or both. 

I hope this helps with the investigating from team @NineLine @BIGNEWY