F16 Turn Rate in different fuel states (weight) - what speeds do I need?

[darkman222]

A question which sounds simple but I am not really sure about it.

There are a lot of diagrams out, but when I am fighting on a dogfight server with a clean F16 I start with 5000 lbs of fuel, burn down to bingo, and that F16 starts to become a turn rate monster below 2000 lbs of fuel.

Are there diagrams related to aircraft weight, or if its not allowed to post, what is the advice for best turning speeds starting off with almost full tanks: 5000 lbs -> 450 kts ? And when approaching Bingo below 2000 lbs -> 420 kts? Is that in the ball park?! All speeds close to sea level 5000 ft altitude, where most of the dogfights end up at. Talking about CAS speeds I think, right?

Any advice?

Edited December 18, 2021 by darkman222

[Frederf]

There are charts and it's as you say. Best turning rate is always the slowest speed that you can hit 8-9G (or whatever your limit is at the time). Weight doesn't change the speed at best performance nearly at all. The performance depends on weight a bunch but not so much the speed to attain it. The charts are in Mach for speed. In general the speed is less ~0.6 at low alt climbing to 0.9 or so at higher alts.

Almost always max performance instantaneous turn performance is near 450 KCAS. It might be slower at high alt where M.9 happens at lower KCAS.

But all max ITR turns are negative Ps which means it's not something you can sustain for more than about 90 degrees of turn. Being at max ITR parameters grants maneuver potential. Potential is spent after the first turn. After potential is spent best turn is STR which is slower. And sometimes you want other performance than turn rate, e.g. radius which is a little slower.

[Theodore42]

Removing weight from an airframe mostly just reduces how much lift the airframe needs to produce... when it comes to turning. But AoA lift is different than thrust-to-weight ratio lift.

The F-16's thrust-to-weight ratio, what it's known for, is going to get crazy good with less gas in the tank. In addition to a lack of fuel lbs LITERALLY and DIRECTLY buffing what the F-16 is known for, you get added benefits: faster acceleration, a steeper climb at max climb speed, and reduced loss of speed in vertical maneuvers.

An angles fighter will enjoy these buffs in the vertical as well, just nowhere near as much as the F-16. And even if the F-16 had 1 lbs of fuel in the tank with unlimited fuel on, I can't imagine her out-turning an angles fighter, even if it's full of gas. The airframes are too different.

Any by vertical maneuvers, I mean climbing. Probably shouldn't try to out-dive a heavier aircraft.

[Krippz]

8 hours ago, darkman222 said:

A question which sounds simple but I am not really sure about it.

There are a lot of diagrams out, but when I am fighting on a dogfight server with a clean F16 I start with 5000 lbs of fuel, burn down to bingo, and that F16 starts to become a turn rate monster below 2000 lbs of fuel.

Are there diagrams related to aircraft weight, or if its not allowed to post, what is the advice for best turning speeds starting off with almost full tanks: 5000 lbs -> 450 kts ? And when approaching Bingo below 2000 lbs -> 420 kts? Is that in the ball park?! All speeds close to sea level 5000 ft altitude, where most of the dogfights end up at. Talking about CAS speeds I think, right?

Any advice?

 

EM Diagram's list the drag index, weight and altitude that tests are done at. I would try to match what's in the EM diagram when testing. 

[TEOMOOSE]

10 hours ago, Krippz said:

EM Diagram's list the drag index, weight and altitude that tests are done at. I would try to match what's in the EM diagram when testing. 

and i have also noticed that the values for MIL power and A/B power are off in the F-16C.lua, here: CoreMods\aircraft\F-16C.

So the values are in KGs, thrust_sum_max: 8054 kg or 17756 lbs "MIL power", and thrust_sum_ab: 13160 kg or 29012 lbs. 

The F110-GE-129 should produce 17,155 lbs in mil power and 29,500 lbs in Full afterburner.

Edited December 19, 2021 by TEOMOOSE

[darkman222]

Thanks Krippz, but I am not testing I am just trying to understand.

And @Frederf What you are saying is, no matter if my tanks are full or almost empty (at Bingo fuel). The best turn rate will always be around 450 kts CAS?

And the feeling that the F16 really starts to perform incredibly well below 2000 lbs fuel is just because it can hold 450 kts for a longer amount of time? Makes sense to me now.

So for the sake of a simple answer to my question: What I need to do is stick with 450 kts ( at 5000 ft) for max turn rate and just dont care about fuel state, but just care about how long I can hold 450 kts due to fuel state. Correct?

[Frederf]

Sorry, more careful analysis. I set up ISA, 22000lb GW, DI 0, infinite fuel, G effects off. Test run is continuous turn at MIL, sea level, and check Tacview graphs.

Max ITR (and STR) is around M0.5 or a little more which is about 325 KCAS for 25 or more dps. At 450 KCAS (M0.85) TR is about 17.5dps.

At higher altitudes the max ITR Mach is higher say 15,000' it's M0.75 which is about 405 KCAS. In general KCAS for best TR will get higher at higher altitudes. Expect it in the area 330-440 KCAS with slower speed down low and higher up high.

[darkman222]

Thanks for the detailed answer @Frederf But I needed something easier to wrap my head around. Sloppy test from a simple gamer I know. But what I did here was to pick a speed the F16 could maintain, while circling around with full, and then almost empty tanks. I should have done this closer to corner speed, but that would have been much harder to compare when the F16 cant maintain speed long enough, or if G forces cant slow the F16 down long enough, for valid results. But I guess it illustrates what I was wondering about.

F16 turning circles with 340 kts:

1300 lbs fuel -> 6,3 G -> sustained TRT 20 deg / second

7100 lbs fuel -> 5,2G -> sustained TRT 16 deg / second

 

But now the same 7100 lbs heavy aircraft and higher speeds.

F16 turning circles with 400 kts:

7100 lbs fuel -> 6,3 G -> sustained TRT 17 deg / second

The heavier the aircraft is, the lower the turnrate gets at the same speed.

But if I fly the 7100 lbs heavy F16 at 400 kts instead of 340 kts, now I am gaining 1 deg / sec in sustained TRT

This is what I was expecting. A heavier aircraft needs higher speeds than a light aircraft to get a "better" turn rates (but just a little) .  But that also proves what you are saying that the speed does not matter too much. 1 degree per second can make a difference, but not a significant one.

 

Disclaimer: Please dont start a how realistic is the DCS F16 turn rate. We have been there, this is not my interest in that thread. I just want to gain understanding how speed, weight and TRT are related to each other.

 

Edited December 21, 2021 by darkman222

[CaptBadTouch]

I can only speak from a layman gamer perspective, but in most dogfight servers (slick + 70-80% fuel) the best sustained speed is around 400-440 on the deck, higher up (say, 15k ft+) it's around 450-550. When the default bingo warning (2000lbs or so) goes, your jet is lighter and the best sustained speed falls to around 380 on the deck (maybe as a lower bound). There's a good range of speeds where the 16 turns well, and from my experience that's 380-480 in general, hope that helps.

[Mars Exulte]

8 hours ago, CaptBadTouch said:

I can only speak from a layman gamer perspective, but in most dogfight servers (slick + 70-80% fuel) the best sustained speed is around 400-440 on the deck, higher up (say, 15k ft+) it's around 450-550. When the default bingo warning (2000lbs or so) goes, your jet is lighter and the best sustained speed falls to around 380 on the deck (maybe as a lower bound). There's a good range of speeds where the 16 turns well, and from my experience that's 380-480 in general, hope that helps.

 I concur, and starting around 3000lbs of fuel it starts getting very thrusty, much lighter and it gets hard to keep it from accelerating no matter how hard you pull or at what speed :p It's very different, but I really enjoyed flying it in the lead up to the FoH tournie.

[darkman222]

What impressed me pretty much in my little test here is that an almost empty (DCS) F16 has at 340 kts a TRT of 20 deg/sec. If the FM was claimed to be complete, I would do some more testing but until then its pointless just to have temporary values to work with in future dogfights.

 

Edited December 24, 2021 by darkman222