[REPORTED] Too low ITR

Noticed that one cannot attain the ITR illustrated in the F-16C blk.50's performance charts.

Specifically at SL I can at most attain 8.8-8-9 G in ITR at M 0.76, where'as the real aircraft can attain 9.0 G in ITR already at M 0.66.

Specific condition: 26,000 lbs, DI = 50, Sea Level

Track provided below.

ITRerror.trk

Just thought I report back and say this issue is still very much there with no improvement.

At SL I am still only able to reach 8.8 G ITR at M 0.76 when the real thing should be able to hit 9 G already at M 0.66.

In addition to this the max speed specific ITR drops when you close the throttle, which it shouldn't as thrust has no impact on instantanous rate, only the sustained one.

Really hoping to see some improvements here soon because this is a big error, and I still think it's connected with the oddly low G onset rate the DCS F-16 possesses.

Can not confirm. ITR seems to be perfect

I get rates according the rw charts (DI50, sl, 26000lbs) . Below logs

Mach 0.590 22.4 dgs

Mach 0.578 22.6 dgs

Mach 0.573 22.6 dgs

Mach 0.561 22.5 dgs

Mach 0.555 22.4 dgs

Mach 0.549 21.8 dgs

itr f16 sl di50 .trk

Can not confirm. ITR seems to be perfect

 

I get rates according the rw charts (DI50, sl, 26000lbs) . Below logs

 

Mach 0.590 22.4 dgs

Mach 0.578 22.6 dgs

Mach 0.573 22.6 dgs

Mach 0.561 22.5 dgs

Mach 0.555 22.4 dgs

Mach 0.549 21.8 dgs

I am reading G's directly in the sim, not dps from a third party program, and you cannot reach 9.0 G's at M 0.66 @ SL @ 26,000 lbs (DI=50) in the sim atm.

Here's a recording & trk file to confirm:

5pzZmjd6sf4

Peak G attained @ M 0.66 is 8.7 G.

Std. day, 15 C

26,000 lbs

DI = 50

ITRerror2.trk

and another one:

6s7XfzAVrrk

Again 8.7 G's @ M 0.66.

ITRerror1.trk

At M 0.66 you get 8.7 g in game? that corresponds nicely to rw data.

According the rw chart you need to dive with more than 36`000ft per minute (600fps) to get the `corner` rates between M0.54 and M 069.

So you need to dive for testing...

In attached track file I start to dive at ~M.071 at 1800ft. I dive with approx 13`500ft per minute and start pulling harder at M0.7. That way I reach 9g at M0.69 which is according the book.

I have tested different speeds. all logs are turn rates measured in game again, no third party program:

M0.710 21.2 dgs

M0.685 22.0 dgs

M0.682 22.1 dgs

M0.667 22.1 dgs

M0.640 22.3dgs

M0.613 22.6 dgs

M0.606 22.7 dgs

Rates are looking good to me

itr f16 sl di50 m0.68 .trk

At M 0.66 you get 8.7 g in game? that corresponds nicely to rw data.

 

According the rw chart you need to dive with more than 36`000ft per minute (600fps) to get the `corner` rates between M0.54 and M 069.

So you need to dive for testing...

According to the real world data 9.0 G's instantanous can be obtained @ ~M 0.66, not 8.7 G's. (Refer to chart B8-48 in the supplements to the manual and follow the lift line)

Also no point in diving to achieve instantanous rate, diving would only help sustained rate as ITR is all about lift. You are refering to the Ps -600 curve, which again concerns STR not ITR.

Small correction: According to the official charts 9.0 G's instantanous can be pulled at M 0.67, not 0.66.

Ingame however 8.7-8.8 G's is all that can be managed under the same conditions.

What? then how come they can produced the chart at sea level if they dive at 600ft per second?

Ps is less than 0 (Ps < -500 fps)

indicating either speed or altitude must be decreased

to maintain the turn.

At M 0.66 you get 8.7 g in game? that corresponds nicely to rw data.

 

According the rw chart you need to dive with more than 36`000ft per minute (600fps) to get the `corner` rates between M0.54 and M 069.

So you need to dive for testing...

 

In attached track file I start to dive at ~M.071 at 1800ft. I dive with approx 13`500ft per minute and start pulling harder at M0.7. That way I reach 9g at M0.69 which is according the book.

 

I have tested different speeds. all logs are turn rates measured in game again, no third party program:

 

M0.710 21.2 dgs

M0.685 22.0 dgs

M0.682 22.1 dgs

M0.667 22.1 dgs

M0.640 22.3dgs

M0.613 22.6 dgs

M0.606 22.7 dgs

 

Rates are looking good to me

What? then how come they can produced the chart at sea level if they dive at 600ft per second?

 

Ps is less than 0 (Ps < -500 fps)

indicating either speed or altitude must be decreased

to maintain the turn.

Yes, he's mistaking STR (Ps curve) for ITR (lift line).

According to the real world data 9.0 G's instantanous can be obtained @ ~M 0.66, not 8.7 G's. (Refer to chart B8-48 in the supplements to the manual and follow the lift line)

 

Also no point in diving to achieve instantanous rate, diving would only help sustained rate as ITR is all about lift. You are refering to the Ps -600 curve, which again concerns STR not ITR.

Thanks for your small but important correction. So we agree that up to M0.66 ITR (and g) looks according rw chart.

Let‘s have a look at the above mach numbers, where energy loss (speed, altitude

or both) is gigantic (more than 600fps)

Instantaneous turn-rates are turns which are above the maximum sustainable-rates (fps= 0). you can not sustain -600fps, you loose altitude, speed or both. Remember, sustain means no energy loss.

Beside L(max), there are other factors for ITR, like (achievable) g and speed.

Diving has obviously an impact on achievable g , as shown in my trk.

By descending, speed decreases slower in the turn and g can build up, up to 9g as proven.

I recommend to read the part ‚turn performance‘ in the manual page B8-4. There is a good example for how to read the chart (a f16 @ sl di=0, can turn 9g and climb instantaneously almost 36‘000ft (600fps) at mach 0.9) .

Tested ITR (and achievable g) in game do correspond with rw charts as far as i can see.

Just a side note, Ps = (v/g)*(dv/dt) + dh/dt.

So if you keep a constant altitude (dh/dt = 0), the SEP can be derived from aircraft velocity (v) and the change of velocity between timeframes (dv/dt). This is often the way to calculate SEP from flight test raw data.

Also,

Sustained rate. The rate an aircraft can generate while maintaining airspeed and altitude (Zero Ps).

The issue might be the pitch integrator as some users have pointed out, for example:

The DCS viper is using an early NASA FLCS. Which is problematic due to the pitch rate integrator not allowing maximum pitch rate through the envelope. Remember that FLCs was designed to prevent the so called deep stall not maximum performance. It was seen as the starting off point for designing the modern FLCS.

In a diving turn, you actually provide an easier task for the pitch integrator to eliminate the difference between commanded g and actual g, with the help of gravity. Decrease/increase in speed or thrust settings also has an impact. Maybe this explains why you're able to reach 9g faster when diving.

Thanks for your small but important correction. So we agree that up to M0.66 ITR (and g) looks according rw chart.

 

Let‘s have a look at the above mach numbers, where energy loss (speed, altitude

or both) is gigantic (more than 600fps)

Instantaneous turn-rates are turns which are above the maximum sustainable-rates (fps= 0). you can not sustain -600fps, you loose altitude, speed or both. Remember, sustain means no energy loss.

 

Beside L(max), there are other factors for ITR, like (achievable) g and speed.

Diving has obviously an impact on achievable g , as shown in my trk.

By descending, speed decreases slower in the turn and g can build up, up to 9g as proven.

 

I recommend to read the part ‚turn performance‘ in the manual page B8-4. There is a good example for how to read the chart (a f16 @ sl di=0, can turn 9g and climb instantaneously almost 36‘000ft (600fps) at mach 0.9) .

 

Tested ITR (and achievable g) in game do correspond with rw charts as far as i can see.

No, you are again using the Ps curve which is for sustained turns only. Diving does not help ITR, it only improves sustained rate by reducing energy/speed loss.

This thread concerns instantanous turns, and the DCS F-16 is atm pulling 8.7-8.8 G's ITR at the speed (M 0.67) where it should be pulling 9 G ITR. So the DCS F-16 is NOT corresponding with the real world data.

The issue might be the pitch integrator as some users have pointed out, for example:

 

In a diving turn, you actually provide an easier task for the pitch integrator to eliminate the difference between commanded g and actual g, with the help of gravity. Decrease/increase in speed or thrust settings also has an impact. Maybe this explains why you're able to reach 9g faster when diving.

Yes I agree, there seems to be an error with the pitch integrator, which also explains the suspiciously low G onset rate, as well as the odd pause it onset rate when quickly commanding full pitch up above 480 kts or so.

No, you are again using the Ps curve which is for sustained turns only. Diving does not help ITR, it only improves sustained rate by reducing energy/speed loss.

 

This thread concerns instantanous turns, and the DCS F-16 is atm pulling 8.7-8.8 G's ITR at the speed (M 0.67) where it should be pulling 9 G ITR. So the DCS F-16 is NOT corresponding with the real world data.

you are probably wrong again.

Guess teachers from usaf test pilot school would disagree with your thesis too:

9.9 instantaneous maneuverability

9.9.2 structural limitation

...

Even among high performance aircraft, there is only a small portion of the flight envelope in which limit load can be maintained in level flight, although it can be achieved in maneuvers such as dives and pullouts through a much larger portion of the envelope.

source: Performance flight test phase, Chapter 9 Energy, August 1991, usaf test pilot school, edwards afb.

 

In a diving turn, you actually provide an easier task for the pitch integrator to eliminate the difference between commanded g and actual g, with the help of gravity. Decrease/increase in speed or thrust settings also has an impact. Maybe this explains why you're able to reach 9g faster when diving.

So it's a software rather then a hardware issue? Interesting :thumbup:

Have ED came out about this and that it's how they implemented it?

you are probably wrong again.

Guess teachers from usaf test pilot school would disagree with your thesis too:

 

9.9 instantaneous maneuverability

9.9.2 structural limitation

...

Even among high performance aircraft, there is only a small portion of the flight envelope in which limit load can be maintained in level flight, although it can be achieved in maneuvers such as dives and pullouts through a much larger portion of the envelope.

 

source: Performance flight test phase, Chapter 9 Energy, August 1991, usaf test pilot school, edwards afb.

You apparently don't understand what it is you're posting. I tried to help you, but can't help those who refuse to be helped.

I've been trying the F-16 these days, so I'll post my impressions regarding what I felt about its performance in BFM.

I've been flying it against "the new kid on the block" the JF-17's A.I.

And I know it already: the A.I. flight model is not very realistic because of several reasons.

... the point is: I've also flown other types in similar conditions against the JF-17's A.I., and I noticed differences.

Essentialy my "experiment" consisted at:

- JF-17 (A.I.) : 2 x IR A-A missiles ; 3000 lbs internal fuel ; (pilot level 'excelent')

- F-16 and other types (flown by me) : 2 x IR A-A missiles ; 3000 lbs internal fuel

(or quantity for roughly the same amount of flight time as in the A.I. JF-17)

- tried mostly 2 circle fights, started at 3.000 ft altitude at the merge , in which the A.I. JF-17 also went for the vertical frequently;

- keeping my F-16 above 380 kts eventualy seemed to give me some advantage;

- but when needed to cash energy for angles (otherwise he would go into scissors or 1 circle), my speed dropped to near 300 kts... at which point the JF-17 starts gaining speed much quicker than my F-16, and thus giving him an higher Sustained Turn Rate than mine... and I can't follow him anymore.

And now you will all say: "Hey, but the in the A.I. pilot level 'excelent' the aircraft gains UFO like flight properties."

True, but when I've flown the above conditions in the F-15, F/A-18, Su-27 and even in the Mirage 2000, it was somewhat easier / faster to get on the JF-17's six o'clock and also easier to stay there.

Don't really know if it's supposed to be like this in real life, but it really is an anti-climax that way in the F-16.

You apparently don't understand what it is you're posting. I tried to help you, but can't help those who refuse to be helped.

Just to finally clear up some definitions:

There are two different types of turn rates, rates that can be sustained (ps=0 or ps>0) and instantaneous turn rates (ps<0).

Sustained turn rates means no energy is lost, speed and altitude can be maintained because there is enough thrust...

There is no way to improve str by diving, because one of the two preconditions (no speed and altitude loss) is obviously not met then.

Instantaneous turn rates are momentarily, you loose energy (altitude and/or speed) in this ps<0 region. It is the region between the envelope limits (aoa, g) and the ps=0 curve.

A slice is an instantaneous maneuver, since you loose altitude while maintaining speed.

Therefor diving can improve your it turn rate if you are not at the border of the envelope already.

You messed that up in your post #7, 10 and 14.

For further info this link might help

https://books.google.ch/books?id=kaqvC4e_EKcC&pg=PA135&lpg=PA135&dq=what+does+instantaneous+turn+rate+mean&source=bl&ots=BLIavb0_ZA&sig=ACfU3U1qKxDq9KK6w_aDZ2TNSOGIdy995g&hl=de&sa=X&ved=2ahUKEwjF_ZbJgpXpAhUjyKYKHR70AMIQ6AEwEXoECAkQAQ#v=onepage&q=what%20does%20instantaneous%20turn%20rate%20mean&f=false

Page 135, 136

 

You messed that up in your post #7, 10 and 14.

 

Nope.

One last attempt:

1. Max instantanous rate/load factor, which is what this thread concerns, is all about the lift available vs the weight of the aircraft (up until FCS limit), i.e. you follow the lift limit curve.

The DCS F-16 is incapable of reaching its max rate/load factor at the speeds where it should, in this case 9 G's @ M 0.67 @ SL:

2. Ps+/- curves (specific excess power) are there to show you what rates/load factors the aircraft can maintain, the number telling you wether the aircraft needs to lose alt to achieve it, or wether it can do so whilst maintaining or even gaining alt.

Example:

Ps=-600: Sustainable rate/load factor at -600 ft/sec alt

Ps=0: Sustainable rate/load factor at 0 ft/sec alt

Ps=+100: Sustainable rate/load factor at +100 ft/sec alt

Nope.

 

One last attempt:

 

Example:

 

Ps=-600: Sustainable rate/load factor at -600 ft/sec alt

Ps=0: Sustainable rate/load factor at 0 ft/sec alt

Ps=+100: Sustainable rate/load factor at +100 ft/sec alt

I really hope so.

If one thinks your strange thesis to an end, then instantaneous turn rate would not even exist at all. Then even corner speed would be sustainable at -680fps.

Nope, no way to sustain rates above the ps=0 region. Your loosing speed and/or altitude. It is the instantaneous region.

I really hope so.

 

If one thinks your strange thesis to an end, then instantaneous turn rate would not even exist at all. Then even corner speed would be sustainable at -680fps.

 

Nope, no way to sustain rates above the ps=0 region. Your loosing speed and/or altitude. It is the instantaneous region.

...

You should be able to ride the 9G curve as you lose airspeed in a level turn starting above the Ps=0 line, which is exactly what his videos are showing, except that they're maxing out at 8.8G or so, so the FLCS is over-limiting the aircraft. Looks like a valid bug to me.

...

 

You should be able to ride the 9G curve as you lose airspeed in a level turn starting above the Ps=0 line, which is exactly what his videos are showing, except that they're maxing out at 8.8G or so, so the FLCS is over-limiting the aircraft. Looks like a valid bug to me.

Probably you should. I am not saying that it isn’t a bug for sure, just saying that by diving one can get 9 g at M0.69 and that you can achieve the rates according the chart.

If you do the very same test with the hornet, you neither achieve max g (7.5) during the hole maneuver… one can not climb the hill up do corner speed on the g-limit line neither.