F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 11:06
by hummingbird
Hello everyone,

As you surely know DCS recently launched their F-16C Blk.50 module, however I've come across something weird with the FM, specifically what appears to be an overly slow G-onset rate as compared with HUD tapes as well as the BMS F-16.

The effect of this slow onset rate is that the DCS F-16 feels quite sluggish to maneuvr, and it takes so long to reach the max instantanous load factor that in a level turn you will need to be going quite a bit faster than corner speed in order to ever reach your max rate.

Thus my question is wether anyone here would happen to have knowledge on the real Blk.50's DFLCS and what G-onset rate it allows for?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 14:09
by sprstdlyscottsmn
The DCS FBW is a port of the Hornets that allows 9G. It is not representative of an F-16.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 15:07
by hummingbird
Not so sure about that, I'm more inclined to believe that they made an error with gains in the FLCS.

Either way my question still stands, as this information could help get the FM right.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 15:22
by sprstdlyscottsmn
G onset could be as high as 9G/s IIRC, but I have seen the DCS F-16 routinely taken above 30-35 AoA. It is NOT an F-16 FCLS.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 16:50
by f-16adf
F-16 rpt.jpg


According to this doc it's >6G/sec. Somehow think it maybe ~6.2-6.4G per sec. I highly doubt it is more than 7G/sec (could be wrong though)-As that paper by Saab's Robert Hilgren puts the Gripen's onset at 6G/sec. I do know for sure that Colonel Virts said that as far as US jets go, the only jet with a higher onset rate is the F-22 Raptor.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 18:09
by sprstdlyscottsmn
Thanks f-16adf

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 20:35
by hummingbird
It's more than 6 G/'s, what the lined document is saying is merely that anything above 6 G/s is considered high.

Keep in mind that aircraft such as the F-14 & F-15 without any FLCS holding them back are able to put on G's even faster. I do believe the F-16 is capable of 9 G/s however, which is more than fast enough. (Keep in mind that 1 sec feels quite long in combat)

This is the same as the Typhoon: https://www.aerosociety.com/news/under-pressure/

Also based on HUD footage as well as BMS it seems as though the later DFLCS allows for 9.3 G's in a level horizontal turn.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 21:00
by f-16adf
I seriously doubt that. Also, look you can believe what you want about the F-14 or F-15 having a warp turbo button or whatever in that game. Just because you don't have a limiter doesn't mean that you can pull off certain moves. It's not reality, it's a game.

From what I have always read, the F-16 had the fastest "G" onset rates of the teen series. That is the whole point of G training in the centrifuge. The Analogue jets, Block 30 and under, could "trick" it into 9.3G or somewhat even beyond. Joe Nawrocki said he took the F-16N to 10G, maybe more. The Digital jets, Block 40 and up not so much. The only people that can add to that here are the actual guys who have flown it. I.E. Gums, JBGator, Meteor, Outlaw, Magnum, Tailgate, and others. And I'm sure JohnWill would know, since he was a structural engineer on the program. And if you still don't believe, ask CW Lemoine aka Mover. I'm sure he can answer this question, I seriously doubt it is classified.


Even in this video, you can see Gripen onset rates (and they basically match with the Saab person's words, it certainly is not 9G/Sec). And the Gripen is a highly unstable canard delta. I doubt the F-16 has much if any advantage in onset rates against it.

https://www.youtube.com/watch?v=eXaPfUs6sQw


Look at the onset in the centrifuge, not anywhere near 9G/sec. And I'm sure it is near equal to the real jet.
https://www.youtube.com/watch?v=q5KxvsJApT8


That link about the Typhoon being 8/9G (say 8.5) is entirely believable. The EF is a completely different animal than the F-16 /Gripen/ F-15. Its real only rival is probably the F-22, in terms of pure power.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 21:06
by basher54321
hummingbird wrote:Also based on HUD footage as well as BMS it seems as though the later DFLCS allows for 9.3 G's in a level horizontal turn.


AFAIK it was positive 9.3G before the Digital FLCS came in as standard.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 31 Oct 2019, 21:52
by f-16adf
https://www.youtube.com/watch?v=Wvjf6SA87BA


At a little past 4:03 mark the F-16 in this vid starts its high G turn, granted they take the camera off the HUD view after something like 5.8G when the jet enters the turn, but going from 1G to 5.8G seems like a bit less than a second, does not seem similar to a 9G/sec onset rate. But as I said, I could be wrong. That is why we need an actual Pilot to answer this.




This is kinda a poor scan, but it is telling. According to Colonel Virts, at high altitude the F-16's G onset is just 3G/sec. And as he says, second only to the F-22 Raptor. So at normal combat altitudes it could be what I said, maybe slightly more. Still doubt at SL it is equal to Typhoons let alone 9G/sec But as I said, I am not certain. Only those that flew it would truly know.

F-16 rate.jpg

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 01:11
by hummingbird
You can doubt it all you want f16adf, doesn't change reality. Without a limiter the G-onset rate is all about lift required vs lift available. Even an F-4 Panthom can break off its own wings a 600 kts easy if the pilot just janks the stick back for an immediate 9 G's at 18 G/s as there's no FLCS preventing him from doing so.

The reason the F-16 is at all limited in terms of G-onset rate is that the FLCS wants to prevent the pilot from overshooting the 9-9.3 G limit with any sudden jank on the stick, and in order to achieve that it has to slow down the onset rate at some point. Based on HUD footage this doesn't really start to noticably happen before 8 G's though.

Furthermore many centrifuges go beyond 9 G/s, including the US TAC ones used for Viper pilot training, they hit 10 G/s:
http://medind.nic.in/iab/t06/i1/iabt06i1p1.pdf

9-10 G/s is also what I believe the F-16 is capable of, same as the Typhoon which has similar AoA restrictions and thus it would also make all the sense in the world if its G-onset rate was similar.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 01:40
by f-16adf
I will defer to an actual F-16 pilot. Also, the pilot in the doc I posted said 3G/sec at high altitude while still touching 9G. That lines up pretty good with the 30-35,000ft Clean EM charts. I seriously doubt the jet will gain an extra 7G/sec by dropping to SL. Why don't you ask Mover he posts on that site anyways?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 08:15
by johnwill
hummingbird wrote:You can doubt it all you want f16adf, doesn't change reality. Without a limiter the G-onset rate is all about lift required vs lift available.No it isn't. There are lags and filters built into the control laws that regulqte how fast the pilot g command is allowed to move the horizontal tail to increase or reduce g. Even an F-4 Panthom can break off its own wings a 600 kts easy if the pilot just janks the stick back for an immediate 9 G's at 18 G/s as there's no FLCS preventing him from doing so.

The reason the F-16 is at all limited in terms of G-onset rate is that the FLCS wants to prevent the pilot from overshooting the 9-9.3 G limit with any sudden jank on the stick, and in order to achieve that it has to slow down the onset rate at some point. Based on HUD footage this doesn't really start to noticably happen before 8 G's though. Minimizing overshoot is indeed one of the reasons for controlling g onset rate. As you say for an abrupt 9g command, g onset rate reduction begins somewhere around 8g. However, for an abrupt 6g pull, it starts around 5g. FLCS modulates g onset at all g levels to make pitch control smooth and not jerky at any g. The F-16 is unstable subsonic and it wants to diverge g at every opportunity.
Remember, the HUD g meter is driven by an accelerometer in the HUD. Thus it is subject to local g in the HUD, which is much more than airplane g at the CG during an abrupt pull, also more than the pilot feels.

Furthermore many centrifuges go beyond 9 G/s, including the US TAC ones used for Viper pilot training, they hit 10 G/s:
http://medind.nic.in/iab/t06/i1/iabt06i1p1.pdf
About that .pdf - The table of centrifuge training conditions shows many very high g onset rates, but the text explanation only mentions 1g/s sec as Rapid Onset Rate (ROR). That confuses me.
9-10 G/s is also what I believe the F-16 is capable of, same as the Typhoon which has similar AoA restrictions and thus it would also make all the sense in the world if its G-onset rate was similar. AoA limit and g onset rate are not related in any way.
Something else most people don't know, the F-16 g/AoA limiter does not limit g or AoA. It limits g command from the pilot.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 10:30
by Patriot
What would have happened if we would change the 16's AOA limit from 25.5° to say 30-35° ? What would it take? Is it only a FLCS software update or requires structural tampering as well? Would that limit change be benefitial or not? Would it improve the control/maneuver/nose-pointing_ability at low speeds (I assume yes) ?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 11:50
by hummingbird
johnwill wrote:You can doubt it all you want f16adf, doesn't change reality. Without a limiter the G-onset rate is all about lift required vs lift available.No it isn't. There are lags and filters built into the control laws that regulqte how fast the pilot g command is allowed to move the horizontal tail to increase or reduce g. Even an F-4 Panthom can break off its own wings a 600 kts easy if the pilot just janks the stick back for an immediate 9 G's at 18 G/s as there's no FLCS preventing him from doing so.


I wasn't talking about the F-16 there John, I am well aware that the F-16's FLCS uses lag & filters to keep the G-onset rate controllable. However an F-14 or F-4 (or any aircraft with boosted controls but without a control limiter) lacks any such filters, and as such it is instead all up to the pilot not to overcontrol and exceed the G-limit's in these aircraft, as either of them are capable of putting on 10+ G's instantly, which in an F-4 is most likely going to cause it to self destruct.

The reason the F-16 is at all limited in terms of G-onset rate is that the FLCS wants to prevent the pilot from overshooting the 9-9.3 G limit with any sudden jank on the stick, and in order to achieve that it has to slow down the onset rate at some point. Based on HUD footage this doesn't really start to noticably happen before 8 G's though. Minimizing overshoot is indeed one of the reasons for controlling g onset rate. As you say for an abrupt 9g command, g onset rate reduction begins somewhere around 8g. However, for an abrupt 6g pull, it starts around 5g. FLCS modulates g onset at all g levels to make pitch control smooth and not jerky at any g. The F-16 is unstable subsonic and it wants to diverge g at every opportunity.


Yup, completely agree.

Remember, the HUD g meter is driven by an accelerometer in the HUD. Thus it is subject to local g in the HUD, which is much more than airplane g at the CG during an abrupt pull, also more than the pilot feels.
Furthermore many centrifuges go beyond 9 G/s, including the US TAC ones used for Viper pilot training, they hit 10 G/s:
http://medind.nic.in/iab/t06/i1/iabt06i1p1.pdf
About that .pdf - The table of centrifuge training conditions shows many very high g onset rates, but the text explanation only mentions 1g/s sec as Rapid Onset Rate (ROR). That confuses me.
9-10 G/s is also what I believe the F-16 is capable of, same as the Typhoon which has similar AoA restrictions and thus it would also make all the sense in the world if its G-onset rate was similar. AoA limit and g onset rate are not related in any way.
Something else most people don't know, the F-16 g/AoA limiter does not limit g or AoA. It limits g command from the pilot.
[/quote]

What I mean is that if you have an unstable aircraft then the AoA limit is indicative of the G-onset rates possible before you risk an overshoot. i.e. it would make much sense if the G-onset rates of the Typhoon & F-16 are similar considering they're both unstable designs with a similar AoA limit and hence would need about the same safety net in terms of FLCS filters to avoid an overshoot.

Also regarding the FLCS G limit's, according to the system charts for later Blocks of F-16's with DFLCS the G limit was raised to 9.3 G's (8.3 in the system) in order to allow 9.0 G's being reached very quickly at corner speed, i.e. no need to be going faster to allow the aircraft time to reach 9 G's before you drop below corner speed.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 13:47
by basher54321
Patriot wrote:What would have happened if we would change the 16's AOA limit from 25.5° to say 30-35° ? What would it take? Is it only a FLCS software update or requires structural tampering as well? Would that limit change be benefitial or not? Would it improve the control/maneuver/nose-pointing_ability at low speeds (I assume yes) ?


Software changes for sure and it should allow the F-16 to reach its CL Max for good or bad. It has actually been done however you may only be able to do such a thing with Thrust Vectoring - Look at the MATV program to get some idea.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 01 Nov 2019, 13:58
by basher54321
hummingbird wrote:Also regarding the FLCS G limit's, according to the system charts for later Blocks of F-16's with DFLCS the G limit was raised to 9.3 G's (8.3 in the system) in order to allow 9.0 G's being reached very quickly at corner speed, i.e. no need to be going faster to allow the aircraft time to reach 9 G's before you drop below corner speed.




Well that guy is better than me if he can make out anything from that horrendous block diagram that he also describes as being a DFLCS for a Block 25.

The Digital FLCS only came in with Block 40/42 and was supposed to implement the same CLaws as the analogue version so outside of a Block 25 being used for testing I don't know what that is - will have to dig a bit. The reason I stated the limit was already 9.3G on the analog version is because I have it given as advise to F-16 pilots 4 years before the DFLCS even hit squadrons.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 02 Nov 2019, 00:04
by basher54321
Interestingly there was an F-16D Block 25 DFLCS Testbed:


USAF F-16D block 25 #83-1176 from the 6512th TS is flying over Edwards AFB on December 12th, 1986 during Digital Flight Control System trials, with the aircraft carrying six AGM-65 missiles, two 370-gallon fuel tanks, one ALQ-119 ECM pod and two AIM-9 missiles. [USAF photo by SSgt. Long]

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 02 Nov 2019, 13:47
by f-16adf
JohnWill,

Wouldn't a non FBW, non RSS jet technically have lower G onset rates than a jet that has FBW/RSS? Possibly, because of the needed momentum necessary to over come the tail download?


Also, 2 documents on Rapid Onset Runs.
https://apps.dtic.mil/dtic/tr/fulltext/u2/a196171.pdf

https://dokumente.unibw.de/pub/bscw.cgi ... _1999_70(7)_709-12.pdf
(This link not working, so I included it down below)




They both give similar Rapid Onset Runs for the F-16, yet it seems Turkey does not include the "check six" run. All those Centrifuge training profiles: 6G for 30 sec, 8G for 15 sec, and 9G for 15 sec all have a 6G/sec onset rate. And the 9G for 15 sec test matches the video of the F-16 pilots in the centrifuge. It must be remembered, that they even before the test begins are at 1G.
https://www.youtube.com/watch?v=yeIDvevEYuw
https://www.youtube.com/watch?v=q5KxvsJApT8


F-16 G ROR.jpg








John, also in this demo from 1993 of a F-16C Block 50. At 4:45 mark of the video 9.4G appears at the lower left of the HUD, but then later goes back down to 9.0, then back to 9.4G. I thought due to the Digital FCS, Blocks 40 and beyond could not do that? Is there an error somewhere in the jets system?

https://www.youtube.com/watch?v=NqGTGVWfAoI

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 02 Nov 2019, 19:44
by sprstdlyscottsmn
Any G onset rates that vary with several factors.

Pitch Force: Rate of deflection of the pitch control surface, airflow over pitch control surface, lift curve slope of pitch control surface

Pitch rate: Pitch Force, Moment arm of pitch force, moment of inertia of the aircraft.

G onset rate: Pitch rate, lift curve slope of wing/body, airflow over wing/body, weight.

A FBW system can ensure that the optimum pitch control surface position and wing position are obtained for a consistent and predictable pitch performance. A non-FBW, but hydraulically boosted, flight control system may allow the pitch control device to exceed its peak position on the lift curve slope resulting in a stalled pitch surface, reducing available pitch moment and increasing drag. Non boosted (e.g. cable-driven) systems require the pilot to physically fight the airflow over the pitch control surfaces.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 02 Nov 2019, 21:09
by johnwill
Spurts, your list of factors is fine for stable non-RSS airplanes, but for airplanes like F-16, the big driver for pitch acceleration and g onset is the lift center of pressure being forward of the CG. In a subsonic pull up or turn, the 1g tail load is up. When the pull is commanded, the tail very briefly will have an incremental trailing edge up movement (down load), enough to start a positive pitch rate and increase AoA and lift. That increased lift forward of the CG is what drives rapidly increased AoA, lift, and g. The tail is then moved slightly leading edge up, with more up load, modulating AoA, lift, and g to prevent unstable divergence. That up tail load is what reduces wing and aft fuselage load, AoA, and drag compared to a stable airplane.

I know you already know this, it is mainly to help others understand it.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 02 Nov 2019, 23:39
by basher54321
f-16adf wrote: At 4:45 mark of the video 9.4G appears at the lower left of the HUD, but then later goes back down to 9.0, then back to 9.4G. I thought due to the Digital FCS, Blocks 40 and beyond could not do that? Is there an error somewhere in the jets system?


I was thinking that was just down to video editing - as in they might have had to stick in a different bit of footage (the one with 9.0) to fill it out.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 03 Nov 2019, 02:33
by hummingbird
As far as I've been told now by two current pilots the F-16C Blk.50/52 (& MLU) DFLCS allows for more than 9 G's (9.3 is what the charts I've seen so far indicate) in the system in order to allow 9.0 G's to be rapidly reached at corner speed before the aircraft slows down too much. Overshooting 9 G's also apparently happens routinely, and 10 G's has been seen, which as John points out is also a combination of where the sensors are located.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 03 Nov 2019, 11:58
by basher54321
If that is the case then it doesn't sound like much changed at all - an over G inspection was apparently required at 105% e.g. 9.5G+ (symmetric) despite uncertainty over the figure being genuine. If they are seeing less than 11.2G as an F-16N pilot reported in the past then that might be considered progress perhaps.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 03 Nov 2019, 21:34
by Patriot
Just a side simple question.. this always puzzled me. Why specifically F-16 AOA limit is set to 25°? Would 35 or more degrees of AOA avilability be worse to have?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 03 Nov 2019, 23:48
by basher54321
One reason being that the F-16 loses a lot of its directional stability between thirty and fifty degrees AoA where most of the vertical tail is blanked out by the fuselage.

Therefore when they did the MATV program they used Thrust Vectoring to provide the needed directional stability meaning it could then go to much higher AoA. It demonstrated something like 85 degrees AoA stable and over 110 degrees AoA transient and could do similar tricks to the YF-22 like the J Turn, helicopter, cobra etc.

Other jets have similar AoA limits like the Typhoon (already mentioned I think) probably for similar reasons.

There must be a lot on the MATV if you go looking - this is not the thread.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 04 Nov 2019, 00:49
by Patriot
Thanks Basher.

Inusfficient directional stability reserve. Gotchya. So I automatically assume that if the Viper would be a 2-tail design and have more vertical surface to stable itself the muzzle for AOA would of been probably a lot less tight..

Does 2-tail alone are enough means to make the airframe free from AOA restrictions - like i.e. Hornet ?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 04 Nov 2019, 00:56
by jbgator
Got a couple of comments on this thread. First and foremost, what difference does it make what the G-onset rate is, or the AOA limit, or any of the other BS discussions that go on here. How fast will it go? The fastest jet is obviously the best. How many G can it pull? The highest G is obviously the best. How much AOA can it do? The higher AOA is obviously the best. How high can it fly? the higher flyer is obviously better. YGBSM.

I have 2750 hours in the F-16 and I have no idea what the G onset rate is. All I can tell you is it gets to pain in a hurry and gets grey and dark really fast. Any faster is beyond human capability. But not every jet is doing the same performance at the same G. So, again, WHOGAS

AOA limits....I flew the F-4 Phantom II fighter...Bomber...mostly bomber for 179 hours, after 7 years of flying the F-16. I used to tell people the F-4 represented decades of engineering designed to make a supersonic jet feel like a P-51. The whole feel system was BS. After flying the F-16 side stick it was clear to me there was no reason to have the complex bellows and trim system in the F-4. I came home frequently from an F-4 wresting...BFM....experience with a throbbing arm. When the system failed you were in a very precarious position either unable to move the stick or balancing on a pin head. The lack of a limiter IS NOT an advantage. I flew against Tomcats....forget about it. Thank God I went back to the F-16. I flew without concern about limits....G or AOA, for 21+ years. I would not give you a dime to fly the Tomcat, F-15, or Phantom instead.

To Basher, my understanding of the AOA limiter is different. I have posted and referred to the Joe Bill article on high AOA in the F-16. The problem as I understand it is more that the Jet loves AOA in the 35+ region and actually has a nose up tendency up through 45 AOA. That is the reason for deep stall. The strakes and CG result in pitch up moment in that region that the horizontal tails cannot overcome. When you get in a deep stall the recovery procedure is to INCREASE AOA using the MPO to get into a nose down pitching region and try to rate through the 35-45 AOA range back into the <25 AOA. So the limiter was designed to prevent transition into this region. Not to prevent yaw issues, although they occur at higher altitudes and speeds. As I have articulated earlier, this is actually an advantage in my mind as the Viper driver does not have to worry about getting into a slow speed high AOA death spiral....something very easy to do in the Mighty Phantom II. I also never worried, like Tom Cruise, about hitting jet wash and winding up in a spinning monstrosity. BS I know, but the Tomcat was not a jet for carefree outperformance of other 3-4th Gen jets. It was a high speed, high altitude, long range interceptor. What the Navy needed but not a phone booth killer as many wish to portray it.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 04 Nov 2019, 01:22
by basher54321
Hello jb

The OP is trying to ascertain the accuracy of an F-16 flight model in a computer game called DCS.

The explanation (as One of the reasons) I have given re AoA is pretty much word for word how Joe Sweeney (one of the test pilots on the MATV ) describes it. He is surely talking about stability in the Yaw axis do you not think. Joe Bills article has the jet settling into deep stall around 50 - 60 degrees AoA IIRC.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 04 Nov 2019, 01:44
by jbgator
I'm aware what the OP was trying to do. I was responding to the thread drift into G and AOA limiters and all the other drivel on this site trying to place one jet over another based on criteria X, Y, Z. Which seems to be a common form of drift, most often used to propose the Tomcat...pick your jet, is better than another jet. Total BS.

I don't know Joe Sweeney so I would never try to contradict a test pilot but I can tell you from experience that deep stall occurs at low speed well below 50 AOA and HAL has control of the jet anyway well below 35. Yaw departures were only an issue in roll coupling situations usually at higher altitudes, medium speeds, with a directionally unstable configuration (B/D model with CL tank for example). High AO low speed departures led to deep stall, not yaw departure, even when yaw was present during departure, except in an inverted (negative AOA) departure where the yaw rate limiter was not active. Maybe Johnwill can chime in but yaw stability was not a high AOA concern transmitted to me nor encountered by me....and yes, I have departed an F-16 and rocked it out. No yaw concerns. Maybe with asymmetric stores or, in the case to the MATV, while doing extreme transients in yaw or very low or nonexistent speed while thrust vectoring.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 04 Nov 2019, 02:56
by johnwill
My knowledge of the flight control system is mostly limited to how it affects structural loads. All I know about why the AoA limiter is xx degrees is what knowledgable people have told me. An important reason is to help the airplane maintain energy during hard maneuvering. Lower AoA means lower drag, less speed loss, maintaining energy. Don't argue with me about if that was the right choice. It's both ignorance and apathy for me - I don't know and I don't care.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 04 Nov 2019, 20:42
by hummingbird
I honestly don't see where anyone made this a comparison thread? The F-4, F-15 & F-14 were only mentioned to give examples of jets without any FLCS keeping them within safe limits.

It's obvious the fact that the F-16 has an FLCS automatically keeping the aircraft within structural limits is a great advantage as the pilot then doesn't have to constantly watch his G's or be careful about janking the stick too hard. As an F-15 pilot once told me "A Viper driver can just pull on the stick and he gets 9 G's. I constantly have to watch myself not to pull too hard or too little", which probably a big reason as to why the Viper usually dominates the Eagle in high speed fights, the Viper simply gets to 9 G's quicker than any Eagle pilot is safely & reliably capable/willing of doing him/her-self in an aircraft without a FLCS.

With all that said the actual topic of this thread is that the real F-16's (D)FLCS allows for a very high G-onset rate regardless of the limiter, higher than what we're seeing in the current early access version in the DCS flight simulator. Up to 10 G/s is what evidence seems to suggest the real aircraft is achieving, which is the same as in the EF Typhoon, and plenty enough for in terms of what any pilot would want.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 06 Nov 2019, 12:58
by hummingbird
A video of the Gripen to show that it also has a very high G-onset rate, definitely a lot higher than 6 G/s:


Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 06 Nov 2019, 13:47
by Patriot
How about here? This g-meter seems to be far more acurate. The Gripen's one above looks to me like a post production video add on, rather that an actual feedback from the aircraft FLCS.


Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 06 Nov 2019, 14:18
by f-16adf
Gripen onset rate according to this:

viewtopic.php?f=30&t=1029

"Turn performance: 9 G sustained, G onset rate at least 6 G/s (1-9 G in 1.2 s), min -3 G, 20+ deg/s sustained, 30 deg/s instantaneous"

I think this poster (Ola) got this number from Hilgren, (circa 2002ish). And all his above figures are seemingly correct.

If the jet is at 9G in approx 1.2 sec that means it is about 6.7G/sec, since the jet is already at 1G in normal flight. Hence, at 1 sec he would be at 7.7G. I posted that Gripen video earlier in this thread. And at 5:35 he starts his turn. He is already starting the turn at 1G, (which we all experience). So if we are going to keep on this route, he hits 9G, not before 1 second, but ~1.16 sec. Divide that out and that is approx 6.8G/sec. give or take. It certainly is not 9 or 10G/sec.



And as far as the EF is concerned. I have seen info from 3 sources, and they all give different figures. One says 8/9, the other 10, and the last says 12G/sec. So which is it? And all are from the UK I believe. And does this matter? The Typhoon is a monster and basically outperforms all the teen series with ease.

And time all the F-16 turns to 9G going by the HUD, see what you get-

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 08 Nov 2019, 21:48
by Raptor_claw
Maximum g-onset can have serious physiological impacts. I didn't take time to look through the mil-specs (I'm not even sure there are guidelines there) but I can tell you that for F-16, F-22, etc, the max onsets the FLCS allows are set by pilot feedback (during design), not by aircraft control power or structural loads concerns. As a general rule, I would expect that the 8/9 range is probably typical. I would be very surprised if any pilot would accept 12G/sec. If the aircraft is allowed to generate that, I would expect the pilot would get into the habit of self-regulating how quickly he applies aft stick...
f-16adf wrote:And as far as the EF is concerned...One says 8/9, the other 10, and the last says 12G/sec. So which is it? And all are from the UK I believe. And does this matter? The Typhoon is a monster and basically outperforms all the teen series with ease.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 09 Nov 2019, 02:19
by f-16adf
8 or 8.5 seems much more believable than 10 or 12. The Gripen number is from Saab. I also have another doc that gives a similar figure for that jet. Quick question, if the F-16 can do more, say 7 or 8G/sec why then does centrifuge training have all their ROR's with a 6ish G onset? Wouldn't that seem rather unrealistic? Also, on the first page of this thread I posted a quote from an F-16 Colonel (from the book Viper Force, 56th Fighter Wing-To Fly and Fight the F-16), who said at high altitude it was 3G/sec, and second only to the Raptor. Does that seem correct to you?

I tried to have my brother ask some of his squadron buddies but nearly all the prior F-16 guys moved to different units or retired. So any info on this matter would be great.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 09 Nov 2019, 03:06
by Raptor_claw
My 8-9 number was kind of a wag, it might be a bit lower than that, but definitely 6 would be on the low side. I'm not really too familiar with the capabilities that centrifuges have, it may be 6 is the most they can physically generate. I'm honestly a little surprised they can get that high. I assume the only way they have to increase G is to increase spin rate, and there would be limits as to how quickly they could do that. The other option would be to rapidly shorten the arm (i.e. reduce the diameter of the circle) at a constant rotation speed - but don't think they are built that way.

I can't verify the 3g/sec onset at altitude, but it is natural that the max G-onset you can generate reduces as you go higher. You are at a lower dynamic pressure (~calibrated airspeed) for a given Mach, so you need a proportionally higher change in AOA to get the same change in G that you would get down low. To generate the larger AOA change in the same time (to get the same Nz onset), you would need higher pitch rates. If you let pitch rates get too high, though, you are risking overshoots of the G limiter, because those higher rates take longer to arrest or reverse. So, as usual, it's all a tradeoff.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 09 Nov 2019, 03:30
by f-16adf
Thanks for the info. I think the one at Wright-Pat goes above 10. I could've had him ask, he was there this past summer.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 12 Nov 2019, 01:20
by hummingbird
The centrifuges used for F-16 profiles are usually 10+ G/s, same for EF centrifuges.

As for the EF being a monster, in terms of maneuvering performance it for sure is, but is not what we're discussing here, we're talking about control limitation set by the designers, and there is no reason to believe the EF would have been given a higher G-onset rate in its FLCS than the F-16, as like Raptor mentioned it is about the max rate the pilot can take & really needs vs not overshooting the AoA/G limit by too much.

Btw 8-9 G/s doesn't sound unrealistic to me either, but I wouldn't doubt 10+ G/s either based on what I've now read several F-16 pilots have written me, as the specs of the centrifuges used for their training usually read 10 G/s, and they are always said to be slower than the real thing.

That said the G-onset of the F-16 in DCS lies around 5-6 G/s atm it seems, and that is definitely too low. Also hitting 9 G takes quite long in DCS as the onset rate slows down to a crawl at 8 G. In BMS the onset rate is noticably higher and it doesn't slow down so drastically and 9+ G is quickly reached. As a result the BMS F-16 feels quite a bit more agile in pitch.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 12 Nov 2019, 03:01
by f119doctor
When I was assigned to the USAF Safety Center, F-16 G-LOC mishaps were one of the big issues. 9G capability is a challenge for the pilots to maintain blood flow and positive partial pressure of oxygen supply to the brain and eyeballs.

In conventional positive stability aircraft with slower G onset rates, the pilot sees vision tunneling, greyout, and vision blackout progressively as the G loads reduce the blood pressure and partial pressure of oxygen supply to the head. With these clues, the pilot can back off the G loads, or improve his L1/M1 straining manuever to increase the blood pressure to the brain to prevent Loss of Consciousness.

The brain and the eyes have several seconds of residual oxygen within their tissues to keep functioning without the blood supply. But if you shut off the blood supply before that residual oxygen is used up with the rapid G-onset of the unstable aircraft such as the F-16, the pilot can blow past his physiological capability to maintain that oxygen supply to the brain without the visual clues. Pull to 9 gs, everything appears perfect, then the oxygen supply is used up and it is lights out without warning.

The rest of the problem is that once the blood flow is restored, it takes several seconds before the pilot wakes up and then another 20-30 seconds before they regain their wits. When they passed out, they let go of the stick and the F-16 returns to 1 G flight. Except they were in a 9 g turn (probably in full AB), and 1 G flight becomes a descending, rapidly accelerating spiral toward the earth. Most of the time the pilot was unable to regain control of the aircraft before it impacted the ground at a very high rate of knots.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 12 Nov 2019, 04:07
by sprstdlyscottsmn
Yeah, the onset rate of the F-16 killed a few pilots IIRC. It was worlds beyond anything seen until then.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 12 Nov 2019, 11:33
by hummingbird
As far as I can tell the F-16's (D)FLCS must allow for 10 G/s, otherwise there would be no point in profiles with such a high G-onset rate in the USAF training facilities. Or that pilots keep saying the onset rates are slower in the centrifuges than in the real airplane.

Measuring times to G on HUD tapes is probably not going to get us far in terms of assessing max onset rate, it will only show us what is at the very least possible, as the G-onset rate also depends on the pressure the pilot applies to the stick. Hence some videos show faster onset rates than others for the same plane, i.e. because the pilots are pulling at different pressure.

Btw F-16adf, keep in mind that a straight horizontal turn which starts with a roll actually will start either at or very close to 0 G in the horizontal plane in which the turn will then take place. I'm not saying the turns you measured started like this, but just want you to keep it in mind.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 12 Nov 2019, 13:36
by f-16adf
Well, on this one i'm going to have to disagree. I have flown many upon many hard turns (near the Utility Category limit) in Cessna 172's and Cherokee Archer's and upon rolling into the turn I have never experienced zero G. (A Coordinated turn ie. keeping the ball centered with rudder) When I have experienced zero or negative G ---is pulling the yoke back for a few moments and then pushing it forward.

Regarding the Gripen video, https://www.youtube.com/watch?v=eXaPfUs6sQw at about 5:33 his G meter is at 1G and stays positive all throughout turn commencement. His turn to hit 9G takes about 1.16 Seconds nearly matching what the Swedish poster said on this forum about its onset rate. viewtopic.php?f=30&t=1029
The jet simply never hits 9G at 1 second or before.

Now as far as the F-16 is concerned, and as what the Colonel said in the article I posted: 3G at high altitude (and only bettered by the Raptor). Dropping down from 30-35,000ft to SL, is the question here. I simply am not going to believe unless told by an actual Pilot that you are going to gain approx. 7G/sec in onset rate from that altitude loss.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 04:25
by johnwill
hummingbird wrote:Btw F-16adf, keep in mind that a straight horizontal turn which starts with a roll actually will start either at or very close to 0 G in the horizontal plane in which the turn will then take place. I'm not saying the turns you measured started like this, but just want you to keep it in mind.


Not true. In an F-16, if the airplane is trimmed for 1g in level flight and a pure roll command (no change in pitch command) is applied, the airplane will roll, but the g command and actual g is still 1g, not 0g. If you roll 90 deg or if you roll 180 deg or 360 deg, the airplane will still be at 1g.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 05:44
by hummingbird
johnwill wrote:Not true. In an F-16, if the airplane is trimmed for 1g in level flight and a pure roll command (no change in pitch command) is applied, the airplane will roll, but the g command and actual g is still 1g, not 0g. If you roll 90 deg or if you roll 180 deg or 360 deg, the airplane will still be at 1g.


Well I am talking aircraft in general, where if you quickly roll left or right from level flight to immediately afterward engage in a horizontal turn, then the G's should briefly drop to near 0 in the horizontal plane before you start pulling back or the aircraft simply settles at that bank angle. I know the F-16 is 1 G trimmed, but if you roll quickly it shouldn't have time to command 1 G before you start the subsequent pull, i.e. it should also depend on the speed of the roll, otherwise the aircraft would be doing a 1 G barrel roll if you just roll the aircraft - and based on BMS or DCS it doesn't trim to 1 G that fast.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 06:05
by hummingbird
f-16adf wrote:Well, on this one i'm going to have to disagree. I have flown many upon many hard turns (near the Utility Category limit) in Cessna 172's and Cherokee Archer's and upon rolling into the turn I have never experienced zero G. (A Coordinated turn ie. keeping the ball centered with rudder) When I have experienced zero or negative G ---is pulling the yoke back for a few moments and then pushing it forward.


With a sufficiently fast roll where you start level with 1 G in the vertical, you should briefly experience 0 G in the horizontal before you pull pitch in the turn - that is unless you barrel roll into a turn.

If you only roll say 30 deg and then just let the aircraft settle in the bank without further stick input, the aircraft will start turning on its own and you will be experiencing G somewhere in between horizontal & vertical depending on your bank angle, speed & trim. But it will happen gradually, not at an instant, hence why I'm saying that in fast 90 deg roll you will be briefly at or close to 0 G before lift is applied in the horizontal, either on its own or by the pilot via pitch command.

Regarding the Gripen video, https://www.youtube.com/watch?v=eXaPfUs6sQw at about 5:33 his G meter is at 1G and stays positive all throughout turn commencement. His turn to hit 9G takes about 1.16 Seconds nearly matching what the Swedish poster said on this forum about its onset rate. viewtopic.php?f=30&t=1029
The jet simply never hits 9G at 1 second or before.


I never said it did, what I did say was that it is definitely noticably above 6 G/s, which it also is. Hence 6 G/s is not the max G-onset rate of the Gripen, not at all.

Now as far as the F-16 is concerned, and as what the Colonel said in the article I posted: 3G at high altitude (and only bettered by the Raptor). Dropping down from 30-35,000ft to SL, is the question here. I simply am not going to believe unless told by an actual Pilot that you are going to gain approx. 7G/sec in onset rate from that altitude loss.


As has already been mentioned the aircraft doesn't lack control surface effectiveness to reach far beyond even 10 G/s if that's what the designers wanted, the designers deliberately make it so it won't pull that quickly. Hence you can't take a figure for 35 kft and then just linearly scale it for SL.

10 G/s centrifuge profiles would also make zero sense if the Viper wasn't actually capable of such an onset rate.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 06:28
by johnwill
What is "aircraft in general" supposed to mean? For a purely mechanical control airplane (is that an aircraft in general?), in level flight, the pitch command holds the horizontal tail at an angle that trims angle of attack so as to develop lift equal to the weight of the airplane. That is called 1g flight. If the pilot commands a roll without changing the pitch command, the airplane rolls and the tail angle remains the same, and the AoA remains the same, and the lift remains the same, and g remains the same, 1g. "g" is load factor, which equals lift/weight.

So, can you explain what in your world makes the "aircraft in general" go to 0 g? Remember 0 g means zero lift. How did the lift manage to disappear? It doesn't matter how quickly you command the roll, the airplane is already at 1 g, so it doesn't need any time to get back to 1 g. The lift vector you have before the roll, rotates with the airplane to maintain 1 g, no matter how fast you command the roll.

Not that it matters.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 09:41
by hummingbird
I agree that it doesn't matter to our discussion, but allow me to demonstrate what I mean:


As you can see even with the F-16, which automatically trims to 1 G, it takes a tiny bit of time before it trims out to 1 G after a fast 90 deg roll.

As for aircraft without the automatic 1 G trim, this happens:

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 14:51
by f-16adf
"10 G/s centrifuge profiles would also make zero sense if the Viper wasn't actually capable of such an onset rate."


Viper Centrifuge ROR's all have a 6G/sec onset rate. I have already posted the documents that prove it. Yes, certain centrifuges can go much higher. But the ROR's just are not flown at those levels. And if they are please show me a DOCUMENT stating specifically so. Meaning true real life empirical evidence vs anecdotal evidence.

You seriously need to throw out this vicarious flight sim life that you seem to buttress all your premises around. Those sims all have errors and they keep correcting them over time or at least try to, with successive "patches". So what does that tell you? When I see F-18's having superior turn rates above .8 mach or see Tomcats with 32 degree per second ITR, or 21-23DPS sustained turns even at SL, and Mirage 2000's not having the best initial turn, or the designers not seemingly understanding decelerated level turns aka -PS ---yes I laugh.



Any evidence of the Gripen having a 7.5G/sec higher onset rate? Even with the Swedish poster (with the link I provided) divide out all his math. And from the 9G turn in the video, both nearly 7G/sec. 10G/sec seems fantasy land levels.



And as far as the F-16 achieving a 10G/sec ROR, I am seriously going to need something other than your word to believe it as so.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 14:57
by f-16adf
https://www.wpafb.af.mil/Welcome/Fact-S ... ed-centri/


"Aircrew acceleration training and research/testing missions are conducted in the centrifuge, which is capable of producing 20 times the force of gravity, or G's, and can accelerate up to 15 G's in one second."


Now does that mean just because the Centrifuge at Wright-Pat is capable of 15G/sec onset rates, that the F-16 or F-15 or F-22 for that matter all have 15G/sec onset rates?





F-16 Centrifuge training vid, once again not anywhere near 10G/sec onset rate. Kinda can connect the dots here....
https://www.youtube.com/watch?v=yeIDvevEYuw

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 22:37
by hummingbird
What document have you posted that proves all F-16 profiles are 6 G/s ? Up until now I've got atleast 3 Viper pilots telling me that they've done 10 G/s profiles. So I know what you're claiming isn't true. 6 G/s might be the std. ROR profile for the USAF, but 10 G/s ones exist.

Also I've yet to hear a single Viper pilot claim that the centrifuges can match the onset rate of the real aircraft, on the contrary all who have ever spoken on that subject have said the exact opposite, i.e. the centrifuges are nowhere near as brutal as the real aircraft.

Also in this very thread you've got actual SME's saying that 6 G/s is "definitely on the low side".

Furthermore the EF Typhoon which features similar AoA limitations as the F-16 is capable of 10 G/s, as designed. Why would F-16 designers limit the Viper to a lower G onset rate than this? Are you going to claim that the F-16's control surfaces can't generate the lift needed for 10 G/s ?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 22:58
by hummingbird
https://static.e-publishing.af.mil/prod ... 11-404.pdf
"Type 2 Aircraft—Aircraft capable of rapid G-onset rates greater than 6.0 G/sec and sustained
G-loading greater than 5 seconds above 7.5 G. Examples of USAF military aircraft meeting this
definition are the F-15 C/D, F-16, and F-22A."

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 23:33
by f-16adf
Read that doc carefully, it is saying that they are: "Aircraft capable of rapid G-onset rates greater than 6.0G and sustained G-loading greater than 5 seconds above 7.5G.

This proves absolutely nothing because I have always said that the onset rates are above 6G/sec. But you seem to think that >6G/sec = 10G/sec onsets which it certainly does not. If anything it further proves my point that the ROR's are all flown with 6G/sec onsets. Which I have already stated numerous times.

So a jet that is supposedly capable of 10G/sec onsets, yet the pilots are only exposed to training with 6G/sec onsets, All the while the centrifuge they train in can do 15G/sec onsets. Hmmm, that makes a lot of sense.......



Finally, I never said that the G loading was not greater than 6G. What I said for the Viper is that it probably is like the Gripen aka 6.7 to maybe 7G/sec. Since when does a 6.7/6.8G/sec or even 7G/sec onset equal to the far off figures that you are postulating aka 10G/sec for the Viper?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 13 Nov 2019, 23:41
by f-16adf
http://www.airforcemag.com/MagazineArch ... glock.aspx


and


"After pilots complete the GOR run, they proceed to the ROR exposures. These consist of onset rates of six Gs per second up to plateaus of ten to fifteen seconds duration at levels ranging from +5Gz to +9Gz. Because fighter Pilots spend a lot of time looking over their shoulders, they are given the opportunity in training to take rapid onset runs while in the "check six" position. These ROR, high-G runs are the brass rings of the training program. On successful completion of this program, the pilot is well trained and confident of his ability to cope with eight or nine Gs in his aircraft. The success of this program has been demonstrated by the marked drop over the past three years in the rate of pilot losses to G-LOC."


See, you were saying that centrifuge training uses 10G/sec onsets, which it once again, does not.
download/file.php?id=31745&mode=view




Also, I don't claim to be anything. But I can read a flight manual. So where does the F-14 get a 21-23DPS SL STR? Why does a Shaw Block 50 weigh the same empty as a Greek Block 50? How come the Block 50 isn't doing 17 second complete 360 degree turns as the jet does in real life? Why is the Hornet on steroids past .8Mach? Why did they dummy down the Mirage 2000?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 00:55
by hummingbird
Again this isn't about std. USAF ROR profiles (esp. since different countrys AFs use different ROR profiles), it's about the max g-onset rate that the real aircraft is capable of, and I've seen nothing that would indicate it should be below at least 8 G/s, and I'm confident it's capable of even more.

Off Topic: Why are you all of a sudden talking about the F-14? Do you feel it is overperforming in DCS? I can tell you for a fact that it isn't. Flying with everything set to auto, as you should, the DCS F-14 is matching the real life performance charts precisely. To achieve anything like 20 dps STR at SL you will need a completely clean aircraft with about half fuel. (Unless you're talking about a few people "cheating" and dropping full flaps not caring they will jam in order to achieve a higher rate ofcourse, but that has actually patched recently)

Same goes for the DCS F-15C btw, it closely matches the real life performance charts for the jet.

As for the DCS F-16, I can do a sub 17 sec 360 turn in it no problem. My three only problems with the DCS F-16 FM atm is the oddly low G-onset rate (much lower than in BMS which by comparison feels right), the too low full mil thrust and finally the inability to apply more than -2 G's, where'as HUD footage shows -3 G sustained negative loops.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 02:28
by f-16adf
It's really simple to find its turn rate at Sea Level, ie standard day. Reference Figure 9-2. Specific Excess Power Diagrams (Sheets 2,3,4 of 12). 3G at SL happens at about .33 mach. 5G at SL at about .46 mach, and 6.5G at SL at .62 mach. Now Superimpose those on the diagram and with the generally same upward curving arch it, should top off at about 18.2 or 18.3 DPS. That is with 4 Sparrow, 4 Sidewinder. Tear off those missiles and 2 pylons and a good, or more realistic number is now about 19.3-19.4DPS. at SL w/50% fuel.

For the Hornet, there are published numbers telling that after .7mach its turn rates go down. Although I will say that there are CF-18 demos from the mid 1980's showing it completing a 360 in under 18 seconds. I have a book that says its max STR is slightly over 20DPS. But not happening at .8 or .9 mach-

It is well known that the Mirage has the best initial turn of all those jets. SL it is around 29DPS. or a little over.



As far as the F-16 there are Solo Turk demos of him completing 360 degree turns, though not at Ps=0 (but above), in crazy minimum times of 14-15 seconds. And he is in a Block 40. Starting at about 2:35 mark https://www.youtube.com/watch?v=q36JblL7IRg

And I'm sure the Block 50 isn't too far off that insane turn figure.


So that is my take on it-





As far as the G onset, (and it's getting to the point of absurdity here). Here is the report of GLOC of Thunderbird jet and his maneuvers. Now I'm certainly not implying max onset is 5.8 as in that one column. But the guy was flying a clean jet, and there are no figures at or around 10G/sec as far as initial onset rates in this report. Or even in pilot error to accidentally induce or go past 6. Although, the maneuver may have not required anything above 6 to get it started. Yet, unfortunately, there was still a fatality here going from -G to +G, i.e Push/Pull. But I'm still sticking to my estimate of 6.7-7G/sec, or until an actual F-16 driver does in fact tell me I'm wrong.
F-16 Thunderbird pg.jpg



From this report:
https://www.acc.af.mil/Portals/92/AIB/1 ... 132501-787

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 09:50
by hummingbird
Said fatality report obviously doesn't show us the max onset rate the aircraft is capable of, it just shows us the onset rates typical for that demo routine. G-LOC fatalities, just like that one, also typically happen after having sustained a high amount of Gs for a prolonged time, not a milisec rapid onset pull / jerk. A report on human physiological limitations concludes that 12 G/s can be pulled unstrained for 1.5 sec before G-loc, as the brain has enough reserve oxygen to last for that long without any blood flow before it starts shutting down.

For context F-15 pilots for example were found to conciously rarely apply onset rates of more than a smooth 4 G/s during ACM training, eventhough said aircraft features no limiter and can go way above 10 G/s. The qouted reason being that they felt if they started applying anything above 5 G/s they no longer felt confident they could reliably stay within the 7 G limit they usually operated under by feel. In short they were self regulating their stick inputs in order to stay both comfortable and safely within the limits. In real combat however they always had the ability to jerk out a way faster onset rate should they need it.

As for the F-16, it has massive control surfaces for its size, hence if the designers wanted it they could have set the g-onset rate way beyond what any pilot would find usable or safe. But since 9-10 G/s was deemed applicable in the EF 2000 there's no reason to believe that the F-16 isn't similar in this regard, esp. since too low an accessible G-onset rate can be deciding disadvantage in a dogfight, as the fighter that can reach a certain G the fastest will have a head start in any angles fight.


As for the DCS F14 again:
Remove the 4x AIM7's + 4xAIM9's plus their glove pylons and I see no reason the F-14B shouldn't be capable of 20 dps at SL - a figure that quickly rises as the F-14 burns through its fuel.

We tested the F-14B @ 55,600 lbs w/ 4xAIM7 + 4xAIM9 and unlimited fuel (50%) and it matched the performance charts to within -/+0.05 G in sustainable load factor. (we dont measure dps as there's no reliable way of doing this for dcs except calculating it from the load factor reached. And using tacview is a big no no)


Btw the F-15C is capable of 18.5 dps at SL with the same load out as pr. its performance charts, and since it's in general ~0.5 dps lower than the F-14 in max STR I'd expect about 18.7-19.2 dps for the F-14B with afforementioned load out at SL. Remove the drag & weight of the missiles and pylons and you're at 20+ dps easy.


As for the DCS F/A-18 we agree, something is off with its FM, it shouldn't be outrating the F-16, esp. not above 400 knots, but I believe this stems of ED lacking actual EM charts for this aircraft.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 11:05
by hummingbird
Also in the RAF the std. ROR centrifuge profile for EF pilots is 9 G reached at 6 G/s and sustained for 15 sec (NATO standard), despite the aircraft itself being capable of 9-10 G/s, hence a 10 G/s profile is made available by the new Thales centrifuges in the UK, and an onset rate capability of atleast 10 G/s is recommended for all new centrifuges constructed in NATO countries (the Poles recommended this in the early 2000's).

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 15:33
by f-16adf
If the onset is truly 8G/sec, yes, that seems more believable than 10G/sec. But as I said earlier, it would not make too much sense if the Centrifuge at Wright Patterson AFB can attain 15G/sec, while the Jet is capable of 10G/sec onset, yet (as all the docs/videos say) F-16 pilots are only trained to about 6G/sec onsets in their ROR's. But, you do bring up a good point about what the Brits do with the EF.



Concerning the Tomcat, I have taken those SL SEP chart numbers from the manual, and I come up with ~.5DPS (give or take) lower than what you come up with. I figure it out to be in the mid 19's (again-give or take) with a clean jet at 50% fuel, SL. I extrapolated the weight of the 8 missiles and their effect on performance/ differences from the other 57,193 and 59,695lb load out charts. Losing that weight/drag from 8 AAMs/pylons is going to effect it less since it is a giant airplane to begin with. But either 19.4 or 19.5, or as you say maybe near 20 is not a big deal. My issue is watching some vids of it going beyond that. For instance I witnessed slightly over a 32 degree TRT. Yes, at an instant (and tac view or not). But even with Flaps down (and we must remember lowering flaps increase lift, BUT, beyond a point it also starts to increase drag) and the temp down to -15. That figure seems like an embellishment (lift limit out to 9G or not). The only jets that can attain near 32 degrees or slightly over are the F-22 and the Rafale/possibly Typhoon. The Gripen is 30 degrees and change. And the Mirage 2000's is slightly over 29 degrees. Additionally, there exists absolutely zero videos of the B Tomcat pulling off Sea Level turns in under 19.6 seconds (And with zero armament). The 14.7 second 360 degree decelerated turn of Solo Turk Block 40 has nearly a 5 second advantage over it.




The reason why the YF-17 failed the LWF competition was because it, at .7 mach and beyond, was outperformed by the YF-16 (together with other issues -- Acceleration, Fuel, etc). And from what I read- by an increasing margin. Conversely, .7mach and under the YF-17 did best the YF-16, but not by a large amount. There is also a chart posted on the net, of it having an approx 2DPS disadvantage to the F-16A at .9mach and 15,000ft. The F-16 is about 14.3, Hornet is about 12.3. And a book from the mid 1990s says near the same, that at .8-.9mach the F-16 out turns it by increasingly larger margins. According to WAJ and IAC, the Hornet does in fact have a STR a little over 20DPS, but not at .8-.9IMN.





Other than that, some of these sims don't seem too bad. I guess the guys that attempt to develop them try their best as far as you can attain with VR.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 17:16
by sprstdlyscottsmn
f-16adf wrote: Additionally, there exists absolutely zero videos of the B Tomcat pulling off Sea Level turns in under 19.6 seconds (And with zero armament). The 14.7 second 360 degree decelerated turn of Solo Turk Block 40 has nearly a 5 second advantage over it.

Just remember, all demo pilots have to keep under 5.5G due to peacetime NATOPS limits.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 17:28
by f-16adf
Don't you mean 6.5G?

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 17:39
by sprstdlyscottsmn
I do not. 6.5G was the "wartime" NATOPS restriction and 5.5G was the "peacetime" NATOPS restriction.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 14 Nov 2019, 17:56
by f-16adf
Ok, cool, then I learned something. But, if we are going to estimate SL turn rates. Even if it is say 19.7DPS that theoretically still falls below the 6.5G line. If it is 5.5G, still turn rate is near upper 18's. My point is, either of those figures pale in comparison with Solo Turks. And after 6.5G, turn rates on the Tomcat go down according to data.

Also, as stated by Nance he in fact did hit 7-8G as a Tomcat demo pilot on occasion.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 13:36
by hummingbird
F/A-18 G-onset rates vs speed:
Image

That's up to 27 G/s for the F/A-18C. Also note that at 0.6 Mach it's 3 G/s @ 40 kft and 19 G/s @ SL, that's a ratio of 6.33 to 1 for that altitude difference. So if the F-16 is capable of 3 G/s at 35 kft, I would be surprised if it couldn't hit at least 9 G/s at SL, a 3 to 1 ratio.

Hence why I say it wouldn't make much sense if designers wouldn't have allowed for the F-16 to attain 10 G/s via the FLCS when other relaxed static stability fighters with similar AoA & G limitations were allowed that much. The control surfaces are certainly capable of providing the necessary force.




As for the subject of measuing turn times at demos, first of all I find that quite unscientific because there are way too many unknowns, and also keep in mind that a max rate turn limited to 5.5 G is quite a handicap for the F-14.

To achieve the 14 sec 360 turn that you claim a Solo Turk did you would have to hit atleast ~9 G's of instantanous load factor, max ITR, something no F-14 was allowed to do in a demo eventhough it could easily take it. So the 19 sec turn around for the F-14 in a demo is pretty damn impressive if the pilot wasn't even allowed to pull max ITR or go above 5.5 G's sustained. (Note: Loaded F-14 hits ~6 G's at its max STR @ 5 kft, at SL it would be over 7 G's)

That said we don't have to guess regarding turn rates, we have the official performance charts for both the F-14 & F-16, and we know that if both are maxed out performance wise (with similar load out), and with no regard for G limits, then below ~0.65 mach the F-14 wins in ITR or STR, whilst above that speed the F-16 wins STR wise. Again this is assuming the F-14 pilot doesn't give two sh*ts about the 6.5 G limit ofcourse, which in peace time they certainly did, whilst they obviously wouldn't so much in combat with as much as 11 G's having been reached by Tomcat pilots without any damage to the airframe.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 16:09
by f-16adf
Solo Turk is achieving his average rate of 24.5DPS becasue he is Decelerating throughout his turn. He is coming in at 9G and probably around .62-.63mach and basically flying -250Ps throughout his turn. And he is finishing his turn at around 5G's and probably . 4mach. He is not flying a Sustained Turn, and notice going from 9G on down his turn radius is decreasing. And most importantly he is not losing any vertical feet.

You seem to think that a -Ps means you are solely losing vertical feet, no, it's an acceleration/deceleration value. For instance, take a 5.56 round and fire it out of a rifle (say an AR). At the muzzle it may have around 2900F/Ps in velocity, while 300 meters down range it might be around 1900F/Ps in velocity. Meaning in another words it has slowed down, i.e. lost energy.


If you use the F-14B Specific Energy Charts and plot for Sea Level, his Max sustained turn rate will still occur prior to 6.5G. It occurs somewhere between 6.5G and 5G. Notice that when going from 25K to 15K to 10K to 5K there is an average increase of around 2-2.1DPS. So at SL I would expect the generally the same. At 5K it is 16.1-2. At SL, with using the SEP charts, and the near 2.1DPS gain it probably will be around 18.3-4, and that is with the 8 AAMS and 50% fuel. Again, seeing that with the SL SEP numbers the nature of the curve is still nearly identical to the 5K chart. Meaning it should bow upwards a little between 5G and 6.5G. Now strip off the weapons which weight basically is close to but less than 3,700lbs Notice that from going from 59,695lbs to 55,620lbs a difference of 4,075lbs turn rate only increases maybe max by 1.4DPS. So even using that liberal figure, lets add that to 18.3, so now we are at 19.7DPS. Again, a liberal figure. That still falls slightly below 6.5G. Now lets say he does come in fast at SL and at 9G, He at 9G would be bleeding near twice the -Ps in energy than the Turkish Viper. The F-16, according to the Block 30 big inlet chart, bleeds a little over -400Ps at 9G and near -500 at 8G. Look at the Tomcats 5K chart, if you were to draw out a 9G line he would be losing over -1600Ps. And even from explicit data from the chart, with it at just 6.5G he is already at near -1000Ps. So a theoritical SL 9G Tomcat turn, means he probably will see a 27.5-28PDS ITR, but at a fleeting instant, then after losing energy at copious amounts.


So there is basically no way for any F-14 to match the time of Solo Turk, and he is flying a Block 40. If he were in a Block 30 it would be even faster since he is around 700lbs lighter. The only jets that can come close to his time are the "striped down" Anatoly Kwotschur (Kvotchur) Su-27 or another GE powered F-16.


It should be noted as well, Keith "Okie" Nance in his Aircrew Interview Q&A explicitly said (at 1:27:20) he flew many airshow demos at 7-8G.
And the words of an email from an F-14 pilot to me from years back: "In training, it was not unusual to go beyond 6.5 Gs accidentally. This would be written up in the logbook and an inspection would be made. A pilot would not get into trouble by exceeding the G-limits, unless he made a habit of it; did not write it up, or overstressed the aircraft causing significant damage. I believe I may have hit 8Gs a time or two, and certainly a number of times over 7Gs. It happens."

Now you can believe it or not, I don't really care-




Solo Turks time (at 2:40) is not a claim, it is reality. Time it, see with what you come up with. The F-14's time is not anywhere even close.
https://www.youtube.com/watch?v=q36JblL7IRg

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 18:43
by f119doctor
hummingbird wrote:Hence why I say it wouldn't make much sense if designers wouldn't have allowed for the F-16 to attain 10 G/s via the FLCS when other relaxed static stability fighters with similar AoA & G limitations were allowed that much. The control surfaces are certainly capable of providing the necessary force.


The F-16 has negative static stability under most subsonic conditions. The control surfaces actually do not have to provide the force to generate G-onset -- if they stop moving, the aircraft will immediately depart controlled flight, either pitching up or down something greater than +/-60 AOA, generating G loads of +/- 10 to 15 Gs depending on airspeed, and basically stopping forward flight. The tailplanes are actively working to keep the pointy end facing forward at all times. And once the pilot gives a G command with the sidestick, the tailplanes move enough to start the increase of AOA in the desired direction, then are actively moving the other way to slow and stop the increase in AOA as the commanded G is reached. So the FLCS is actually working to manage the G-onset rate below what the airframe is capable of subsonically.

Early in the F-16 operations, there were a few events where FLCS lost electrical power, the tailplanes froze in their neutral rig position, and the aircraft departed with a -15 G pitch down and crashed. The immediate response was a TCTO to re-rig the horizontals so that the aircraft would pitch up instead in that condition, but it was still going to be a 15 G departure with loss of all flying speed. There was some debate as to whether this re-rig was a good thing, but the pilot community was reflexively against the nose down departure - can't say I blame them.

The original FLCS power source was the main aircraft Constant Speed Drive Generator, with little Ni-Cad batteries (of unknown charge state or condition) in the FLCS computers as backup. Via TCTO, a trickle charge from the main aircraft battery to the FLCS batteries was added to ensure they were fully charged, and then a Variable Speed / Constant Frequency PMG generator dedicated to provide 100% reliable power to the FLCS system was developed and retrofitted to fix the problem for good.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 20:22
by hummingbird
f-16adf wrote:Solo Turk is achieving his average rate of 24.5DPS becasue he is Decelerating throughout his turn. He is coming in at 9G and probably around .62-.63mach and basically flying -250Ps throughout his turn. And he is finishing his turn at around 5G's and probably . 4mach. He is not flying a Sustained Turn, and notice going from 9G on down his turn radius is decreasing. And most importantly he is not losing any vertical feet.

You seem to think that a -Ps means you are solely losing vertical feet, no, it's an acceleration/deceleration value. For instance, take a 5.56 round and fire it out of a rifle (say an AR). At the muzzle it may have around 2900F/Ps in velocity, while 300 meters down range it might be around 1900F/Ps in velocity. Meaning in another words it has slowed down, i.e. lost energy.


I know solo turk didn't achieve a 14 sec 360 via STR f-16adf, that's what I was trying to tell you, that he had to hit max ITR, which means riding the max lift curve from start to finish. The F-14 wasn't ever allowed to do that at demos as it would bring it way above the 5.5 or even 6.5 G limit.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 20:40
by f-16adf
And I pointed out to you that, say if it did, it wouldn't have the available Ps to complete the turn in that time since it in fact is bleeding near twice the -Ps at 9G vs the F-16C. Theoretically, if i'm at 9G I certainly would rather be in the jet that bleeds -500Ps vs the jet that bleeds -1000Ps.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 20:54
by hummingbird
f-16adf wrote:And I pointed out to you that, say if it did, it wouldn't have the available Ps to complete the turn in that time since it in fact is bleeding near twice the -Ps at 9G vs the F-16C. Theoretically, if i'm at 9G I certainly would rather be in the jet that bleeds -500Ps vs the jet that bleeds -1000Ps.


You don't seem to understand that the F-14 doesn't need to hit 9 G's to beat the F-16 round a turn. It can beat it round the turn with a lower G, which is the point you're entirely missing.

A few facts here:
1) The F-14 has a higher ITR than the F-16 across the board (no limiter)
2) F-14 has a higher STR than the F-16 below 0.6 Mach, and importantly almost exactly the same max STR. (within 0.1 dps)

In short your mistake is assuming that the F-14 pilot goes to his max ITR (28 dps) or tries to match the F16 in G's pulled, but he doesn't need to, he can simply match the F-16's rate, lowering his speed loss as well, until speed drops to 0.6 mach, at which point the F-14 can now maintain a higher rate than the F-16. And same rate at a lower speed = smaller radius = eventual gun solution.

It's pretty simple.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 21:01
by hummingbird
f119doctor wrote:
hummingbird wrote:Hence why I say it wouldn't make much sense if designers wouldn't have allowed for the F-16 to attain 10 G/s via the FLCS when other relaxed static stability fighters with similar AoA & G limitations were allowed that much. The control surfaces are certainly capable of providing the necessary force.


The F-16 has negative static stability under most subsonic conditions. The control surfaces actually do not have to provide the force to generate G-onset -- if they stop moving, the aircraft will immediately depart controlled flight, either pitching up or down something greater than +/-60 AOA, generating G loads of +/- 10 to 15 Gs depending on airspeed, and basically stopping forward flight. The tailplanes are actively working to keep the pointy end facing forward at all times. And once the pilot gives a G command with the sidestick, the tailplanes move enough to start the increase of AOA in the desired direction, then are actively moving the other way to slow and stop the increase in AOA as the commanded G is reached. So the FLCS is actually working to manage the G-onset rate below what the airframe is capable of subsonically.

Early in the F-16 operations, there were a few events where FLCS lost electrical power, the tailplanes froze in their neutral rig position, and the aircraft departed with a -15 G pitch down and crashed. The immediate response was a TCTO to re-rig the horizontals so that the aircraft would pitch up instead in that condition, but it was still going to be a 15 G departure with loss of all flying speed. There was some debate as to whether this re-rig was a good thing, but the pilot community was reflexively against the nose down departure - can't say I blame them.

The original FLCS power source was the main aircraft Constant Speed Drive Generator, with little Ni-Cad batteries (of unknown charge state or condition) in the FLCS computers as backup. Via TCTO, a trickle charge from the main aircraft battery to the FLCS batteries was added to ensure they were fully charged, and then a Variable Speed / Constant Frequency PMG generator dedicated to provide 100% reliable power to the FLCS system was developed and retrofitted to fix the problem for good.


Yep, in other words if they wished the designers could've given the F-16 the ability to pull over 20 G/sec in onset rate, but that just wouldn't be in anyway useful to the pilots or worth the risk in terms of G overshoots. Hence I believe they probably stuck to ~10 G/s as max commandable onset rate, same as the EF designers did.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 21:40
by sprstdlyscottsmn
f-16adf wrote:Theoretically, if i'm at 9G I certainly would rather be in the jet that bleeds -500Ps vs the jet that bleeds -1000Ps.

Theoretically, if BOTH planes are starting a 9G pull from the same speed (lets say .9M for the sake of discussion), the F-16 will lose speed slower (retain more speed) but the F-14 will turn quicker and tighter because by decelerating it is moving "left" up the 9G line faster to higher DPS and smaller radii, and since the max lift line of the F-14 is "to the left" of the F-16 then there will be a time where the lift limited Tomcat is still turning with higher DPS and a smaller radius.

Now, only an idiot Viper driver would keep playing this turning game once he saw the Tomcat go from wings back to wings forward in mere seconds. He should then take his game vertical while still holding G. This will tighten the horizontal radius and give a definitive position advantage against the F-14.

In this setup, the F-14 would have dropped from .9M to .7M in the first 90 degrees of turn or so, while the F-16 is still at .8M. If the F-16 pilot goes vertical here while still turning at 9G, he will lose speed, but he has speed to lose. The F-14 pilot is now stuck with a bad choice, reduce G to try and save speed, go vertical at the expense of more speed, or both.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 21:52
by f-16adf
If the Tomcat pilot wants to stay at Ps=0, and .55-.65mach, fine. As JbGator said, the F-16 can be at -Ps. So lets say the F-14 pilot drills around in circles at Sea Level at .55-6IMN. So he would still have a turn rate as I said at SL of (and going by charted info from the manual ---the Specific Excess Power sheets, for 3G, 5G, 6.5G) around 19.7DPS. And a radius of 1600ft. Now lets take Solo Turk He comes in at 9G and .64 Mach starting radius of about 1800ft. By the time he is done with the turn (at around 5G, his ending radius is now about a little over a 1100ft.) It doesn't take a genius to figure out who wins here. The F-16 is flying with basically the same turn radius while at a far higher turn rate. All throughout this maneuver the Viper's turn circle is shrinking. Look at the video it shows the exact same thing.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 21:56
by f-16adf
Spurts, I am fully aware of that. The question is (and I had the numbers) since the F-14 is at blazing high -Ps, throughout this turn, does he even ever finish or get close to finishing that turn before he is basically down to landing speeds. We have already seen what Solo Turk can do.


Use that formula for what you did with the F-16 v Gripen thread. I plugged in estimated numbers, using that formula. That is what I'm inferring here.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 15 Nov 2019, 22:23
by sprstdlyscottsmn
I see. In my (admittedly DCS) experience, no. If I ever start at 9G and hold through max lift AoA then I will either black out or be down to .4M within one turn. Best bet is to hold around .55-.6M and 15 "units" AoA. I can't look at the G meter when doing this because of where it is located and the HUD does not provide any ADC info.

That is a bit off topic for this thread though, as that has little to do with onset rates and control laws.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 16 Nov 2019, 12:14
by hummingbird
sprstdlyscottsmn wrote:
f-16adf wrote:Theoretically, if i'm at 9G I certainly would rather be in the jet that bleeds -500Ps vs the jet that bleeds -1000Ps.

Theoretically, if BOTH planes are starting a 9G pull from the same speed (lets say .9M for the sake of discussion), the F-16 will lose speed slower (retain more speed) but the F-14 will turn quicker and tighter because by decelerating it is moving "left" up the 9G line faster to higher DPS and smaller radii, and since the max lift line of the F-14 is "to the left" of the F-16 then there will be a time where the lift limited Tomcat is still turning with higher DPS and a smaller radius.

Now, only an idiot Viper driver would keep playing this turning game once he saw the Tomcat go from wings back to wings forward in mere seconds. He should then take his game vertical while still holding G. This will tighten the horizontal radius and give a definitive position advantage against the F-14.

In this setup, the F-14 would have dropped from .9M to .7M in the first 90 degrees of turn or so, while the F-16 is still at .8M. If the F-16 pilot goes vertical here while still turning at 9G, he will lose speed, but he has speed to lose. The F-14 pilot is now stuck with a bad choice, reduce G to try and save speed, go vertical at the expense of more speed, or both.


Spot on.

Entering and staying in a purely horizontal turn fight is playing the Tomcats fiddle for no good reason, esp. when you're in the rocket ship that is the F-16. Use the vertical in the F-16 and the Tomcat will soon start to struggle.

Hence like Okie has said, given a choice between the two aircraft in a dogfight, I would generally choose the F-16. It's just a much easier aircraft to get max performance out of, and any screw up (which is less likely to happen due to the carefree handling) can more easily be saved due to the higher level acceleration & climb rate.

IMO the F-16 is the ultimate dogfighter of the teen series fighters, an absolute monster in overall performance, outturning anything it can't outclimb or outrun, and outclimbing or outrunning anything it can't outturn, and it wasn't beat until the arrival of the eurocanards & F-22.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 16 Nov 2019, 12:37
by hummingbird
f-16adf wrote:If the Tomcat pilot wants to stay at Ps=0, and .55-.65mach, fine. As JbGator said, the F-16 can be at -Ps. So lets say the F-14 pilot drills around in circles at Sea Level at .55-6IMN. So he would still have a turn rate as I said at SL of (and going by charted info from the manual ---the Specific Excess Power sheets, for 3G, 5G, 6.5G) around 19.7DPS. And a radius of 1600ft. Now lets take Solo Turk He comes in at 9G and .64 Mach starting radius of about 1800ft. By the time he is done with the turn (at around 5G, his ending radius is now about a little over a 1100ft.) It doesn't take a genius to figure out who wins here. The F-16 is flying with basically the same turn radius while at a far higher turn rate. All throughout this maneuver the Viper's turn circle is shrinking. Look at the video it shows the exact same thing.


Again, the F-14 pilot can simply choose to match the F-16's instantanous rate and lose less energy as well. The F-14 pilot has the option of pulling a higher ITR & tighter radius if he so wishes. At 5 kft the 55,600 lbs loaded F-14 can pull a 1300 ft level turn if he wants, something the 26,000 lbs loaded Viper simply cannot match.

In short, in purely horizontal fight all the F-14 pilot has to do is to match the F-16's ITR (which is lower than the F-14's) until both aircraft drop to ~0.6 mach, at which point the F-14 is now better able to hold its rate than the F-16 and can thus sustain a tighter & higher rate turn.

But again, why would the Viper pilot ever engage in such a foolish game? If I was the Viper pilot I would stay way above 0.6 mach at all times, and instead quickly climb up over the F-14 and maintain a nice max STR circle above him at around 0.75-0.8 mac. Then when I see the F-14 try to come up to follow me I would gradually tighten the turn until I see his nose start to drop in his effort to pull lead in the climbing turn, then roll over and slide right down in behind him.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 16 Nov 2019, 15:09
by f-16adf
Spurts, this is my point about so called ITR.

I have done an experiment with the Mirage 2000's 15,000ft chart. Now obviously the Mirage has a better ITR than the B Tomcat. And I believe, it at that altitude and 9G, bleeds slightly less energy too or they are similar if you were to equalized war loads for both jets (50% gas and 2-AIM-9). My top bleed for the Mirage 2000 and 9G is at -1600Ps. Estimated for the Tomcat nearly -1600Ps. I remember you estimated a -2200Ps bleed at 10,000ft for it a while back -granted with 8AAMs.


Now this is what I did, I took the Mirage 2000 numbers. I started off with -1000Ps @.8mach, -1400Ps @.7mach, -1600Ps @.65mach, -1400Ps @.6mach, -1000Ps @ .5mach, and -450Ps @ .4mach.

Here is an exmaple of first problem.
-1000fps @.8mach
.8 (1056)= 844.8 , I used 1056 as speed of sound at 15,000ft. I took 720*5280/3600 = 1056
-1000fps/844.8=1.18
1.18 (32.2) = 38.0
38.0/1056 = .0360


So each successive figure:

.0576 for -1400
.0710 -1600
.0674 -1400
.0576 -1000
.0326 -450



I came up with

44.08 degrees of turn in 2.14 sec
17.82 degrees of turn in .78 sec
16.7 degrees of turn in .73 sec
32 degrees of turn in 1.6 sec
38.5 degrees of turn in 2.2 sec


Total of 149.1 degrees of turn in 7.45 sec from .8mach to .4mach, and with an average of 20.01dps turn rate.



Please look at my numbers and see if I made any errors. I have no problems being corrected.


So if these figures are in fact correct, the Mirage 2000, a jet with a great 9G ITR, high lift curve; Doesn't even make it to half of the turn before he is basically at 200KCAS (.4IMN) and out of airspeed/decreasing if he so wishes to ride this curve. And that is why you never see the jet attempt to perform in fact such a maneuver. I would imagine the like for the F-14. They don't even make it to 180, so no pilots of these jets are dumb enough to attempt this high ITR or not.



I also have another question to ask you about computing this.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 16 Nov 2019, 16:11
by hummingbird
Comparing the M2000 with the F-14 is where you're making your first mistake, the former being a pure delta wing will loose a lot more energy in the turn than the variable sweep F-14 due to the much higher lift induced drag penalty of the low AR delta planform.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 16 Nov 2019, 16:17
by f-16adf
True, it's a delta. No argument there. But, As I said, very high -Ps are a bad thing. And the Tomcat's Ps spike is surrounded by them, that is if you indeed want to draw it out to 9G. So lets let the person with the Aerospace Engineering Degrees answer this one.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 16 Nov 2019, 17:55
by sprstdlyscottsmn
Assumptions: Speed of sound at 15,000ft is 1,056ft/s, I’m seeing 1,057ft/s from https://www.digitaldutch.com/atmoscalc/ . Assumed value is within any future rounding error of actual value.
.0360 is M/sec deceleration
You averaged 0.0360M/s and 0.0576M/s decelerations between 0.8 and 0.7M to get your time of 2.14s.
I assume you also averaged the turn rates between these two based on the Mirage chart to get degrees turned in the unit of time.
That is my understanding of your analysis. If that is correct, then I see no mathematical errors and your answer should be within an expected margin of error from reality.

I will do a few DCS Tomcat tests, one at 50% fuel 2 AIM-9s at 15,000ft, another at 5,000ft 8AAM “chart matching”, another SL clean “airshow” test. I will turn blackout off and turn unlimited fuel on so my weight stays constant to perform multiple tests.
What I expect to see is two fold, it will be hard to maintain a given G or AoA as there is no limiter for me to hold against, and I will decelerate rapidly during hard pulls.

Oh, and a few G onset rate tests.

Followup, I saw G onset rates from 3-7G/s depending on speed. It is near impossible to do "x G to y AoA at steady altitude" test in real life in the Tomcat. I either end up slowly building G or overshooting the AoA and stalling out even at .7M.

Re: F-16 DFLCS control law & G-onset rate

Unread postPosted: 17 Nov 2019, 04:57
by hummingbird
I can get onset rates of 20+ G/s in the DCS Tomcat quite easily by just janking the stick back. Just be prepared to lose your wings if you're going too fast.

At 55,600 lbs w/ 4xAIM7 + 4xAIM9 @ 5 kft the DCS F-14B matches the real life F-14B/D EM charts to within 0.05 G in sustainable load factor. Peak STR is reached at 5.6 G's @ 0.56 Mach, and peak sustainable load factor is 7.3 G's @ 0.88 mach.

It's the same story for the DCS F-15C, it matches the real life EM charts very well, and G-onset rate is near instant. The DCS F/A-18 also has a lightning fast onset rate (20+ G/s), despite of thos however it is almost instantly halted by the FLCS at the G limit, a 0.5 G overshoot being the most I've seen.

The DCS F-16 is the only one of the teen fighters so far with a comparatively low G-onset rate and a sort of hesitation to increase the load factor above 8.5 G, the onset rate being slowed much earlier, and as a result it has a hard time reaching 9 G's at its corner speed plateau unless going much faster to begin with. This is not what you see in BMS or can observe on HUD footage, here the F-16 seems to build up G's very rapidly and reaches 9+ G's (9.3) very fast & without any hesitation. Hence this is my biggest gripe with the DCS F-16 atm, as this lack of onset rate makes it feel very sluggish in pitch as compared with the other fighters.