[CORRECT AS IS] Odd rocking in G-onset

The only thing I see suspicious is the G-onset rate at high G’s like from 8-9. As is seen on NineLines graph aswell. Humlingbirds videos also show this aswell. The initial onset rate reens to be fine in both ninelines graph and hummingbirds videos. Also I don’t think that a pilot can control that region at all so that would be an isse in the FM. Not an expert just my two cents on it from the evidence.

To be specific in what I've noted so far:

At 500 kts IAS and below, it's only from approx 7 G's on that the DCS F-16 seemingly falls way behind the real aircraft in terms of onset rate, up until that point it seems OK. At very high speeds however, above 600 kts, the DCS F-16 is now very slow to pick up in the beginning, but then atleast the onset rate is now a little bit quicker than before from 8 to 9 G.

In short the onset rate is very inconsistent and different between speeds where 9.0 G's can only be hit instantaneously, and where it can be sustained.

MIL-STD-1797A (DEPARTMENT OF DEFENSE INTERFACE STANDARD, FLYING QUALITIES OF PILOTED AIRCRAFT) could have some guidance. For pitch response verification, usually a step input is used, which means pulling the stick as abruptly as possible. But pulling a 25 lbsf force sensing stick under Gs is not the same as pulling a near-zero stick force joystick under 1G condition. The former would actually take more time to reach the maximum stick deflection/force since you have to confront such a large stick force, so it's not a true step input under test flight conditions.

Pulling a zero stick force joystick abruptly would be closer to a true step input.

5.2.1.2 Short-term pitch response-verification.

 

In practice a true step is not usually feasible. Time may be measured from the midpoint of the control input transient, as sketched, for the most abrupt input feasible. Good instrumentation will be needed to measure the time delay accurately.

Besides, the F-16 FLCS (including Analog and Digital) has a first-order filter at the end of the pitch command block to limit input rate and make the system a first-order system. A typical response curve of a first-order system is shown as below:

In DFLCS, the filter rate is variable dependent on dynamic pressure. Basically if airspeed over 400kts, the k of the first-order filter (k/s+k) would reduce from 8.3 to 6.0, which means a slower filter rate. This is also to be keep in mind when testing the pitch response at different speeds.

The only thing I see suspicious is the G-onset rate at high G’s like from 8-9. As is seen on NineLines graph aswell. Humlingbirds videos also show this aswell. The initial onset rate reens to be fine in both ninelines graph and hummingbirds videos. Also I don’t think that a pilot can control that region at all so that would be an isse in the FM. Not an expert just my two cents on it from the evidence.

Yes, that's my impression as well.

It seems to slow at 7 G's until it reaches a crawl at 8 from where it takes a long time reach 9, which is not what we see in the RL footage where it shoots quickly to 9+ G rather linearly. As a result the RL footage shows the F-16 hit 9 G's about twice as fast as the DCS F-16 if you measure it.

That said I've been going at it for 7-8 hours now almost non stop testing the onset rates (as well as ITR & STR) at all sorts of speeds & weights/drag indexes, timing everything and comparing with EM charts etc. So my mind is filled to the brim atm and I think it's about time I take a break, get some sleep and then look at with a fresh set of eyes tomorrow. In the meantime, please test away guys, the more people we get to collect results the better - esp. since undoubtedly there are people better at compiling & illustrating it on video than me.

Doesn't it matter what RL block you are comparing with DCS?

I know nothing but i would assume the FLCS etc. changed slightly between blocks?

Again, FLCS isn't designed to compensate for every type of control on the market, its designed real-world F-16 controls. How could a sim be programmed to compensate for every variation of every stick that can possibly be used in DCS? I mean you know you can make unrealistic maneuvers in any aircraft in DCS because the control principals between something sitting on a desk and something actually connected to control surfaces are different.

 

I can put two Warthogs (controllers) next to each other and they may not be exactly the same.

I cannot understand how a maximum force input on a real F-16 stick and a full deflection on an axis of a directX devices aren't interpreted the same in the game.

Also: Is there any hardware product rated by ED that will work properly with this? Can't be a warthog by what NineLine said in the quote.

What do I need to buy to get top performance out of my virtual airplane? (and how absurd is it that I have to ask that question?)

I think what irks me quite a bit is that there's a pretense that this is a test that has to be done under very specific conditions.

What we're testing is nothing but the aircraft response to the maximum digital input value DCS can register with any controller. This has nothing to do with the type of controller used, as we are simply pulling to the limit of what DCS allows us to feed it as an input value.

When at this limit the G-onset rate of the DCS F-16 noticeably slows down as the aircraft hits 8G, resulting in a very slow G increase between 8.0 and 9.0G. Other sources (HUD tapes, the other sim, graphs shown in this thread) don't seem to corroborate this behaviour.

This behaviour almost exactly matches Nineline's personal findings as shown below:

PS if it wasn't clear, the blue line was my flight vs the charted results.

 

Again, this test is simply based on the maximum possible input value in DCS. Hardware has nothing to do with this.

I am only considering the green and blue lines. Nineline's result corresponds with my own in the sim when yanking the stick fully aft at speeds well over the minimum required to hit 9G (above 0.9M to make sure we stay well within the 9G band on the EM graph all the time while loading up).

The difference isn't big, but causes a noticeable delay between 8.5 and 9.0G compared to expected results.

So @Nineline to be extremely specific for me personally:

1. I do not consider G-onset rate as a whole too slow by any significant margin.
   
2. I do not consider turn rate/ITR to be off by any significant margin.
   
3. I do not consider controllers to be a contributing factor for this test as it is simply based on the maximum allowed input value in DCS.
   

What I would like verified is the following:

The G-onset rate noticeably slows down in the DCS F-16 between 8.0 and 9.0G specifically. This is not corroborated by HUD tapes or public data. Is this verified as correct behaviour?

If so, would it be possible to get an explanation why the DCS F-16CM Block 50 differs so much from other data as brought forth by users in this thread?

And again, the FLCS cannot be programmed for a desktop controller because a desktop controller can do different things depending on the make, model and even stick to stick. You like evoking Mover, as him if the controls he has used for DCS are anything like what he has used in the real jet. So no, its just like a WWII bird, the stick in a P-47 doesn't move like that of one on your desk, so you will get some variation, even though the FM is programmed to interact like a real P-47 stick, anything short of that will have variations that will throw off your comparison.

 

You are not flying a real F-16, you are flying as close as we can to it, we cannot control what flight stick, gamepad or keyboard you use. We cannot account for that, there are no documents that allow us to program an FM to match all those variables, again, like a WWII aircraft, the FM expects the exact same controls as is in the real thing, its why we try to add things like control freezing, etc.

So what do we need to purchase to have the most believable and correctly simulated experience if our controllers are not up to par to work with DCS: F-16?

You are asking me to ask Wags if he is willing to prove that his 4200 hour SME knows how to check G-onset? Based on nothing solid I can see so far?

 

I will need a little more solid proof before I step on that landmine. Especially when I showed my simple test already backing up our claims.

 

I am willing to go to Wags on it, but I have not been given anything to do so yet.

yes Sir. I am, I believe we all want to know how did they reach the conclusion.

Please take a look the thread Number 78, just few post below you.

We all try to provide the prove for you to step in. And you also admitted yourself you don`t fly Viper much, so why don`t just push our information to Wags and see what he thinks.

:joystick:

Second question is did ED use real world NASA FLCS data for the Viper ?

Because we all know that one is outdated.