Why does the F-18 suffer so much from stores-drag?

[Temetre]

edit: My bad, my post was unclear. Im specifically talking how the addition of stores affects the top speed of the F-18.

Im not talking about fuel economy, which I have not compared.

--------

Not saying anything is wrong or unrealistic, I would just like to understand why this is. I know the F-18 is more draggy than an F-16, and has somewhat weak engines. But the way stores add drag to the plane seems counterintuitive to me, and I wonder if someone can explain it. Below im triyng to explain my train of thought:

 

So you put stores on an F-18, even a single fuel tanks, and it already lowers top speed by a good chunk. Put 4x Aim-120 with the double rack, and youre down even further. At this point it already can be tricky to even get supersonic, maybe impossible to get past the transonic region. Similar story with bombs and other kinds of addons.

Yet with any other plane I tried, F14, FC3-planes, Mirage-2000, Mig-21, Ive never seen such a heavy effect of drag. For example, the F-16 handles a lot worse with three fuel tanks and 6x missiles, but its top speed isnt really affected much. Acceleration is slower, but you can go close to mach 1.8 or so at ~30-40k feet, last time I tried it. Even if you dont use full afterburner (which ofc is very high capacity), the speed seems to remain higher.

 

And consider the difference in drag: An F-16 by itself is a lower drag plane than an F-18, but logically I would then assume that the same drag+weight bomb load would have a more adverse affect on the F-16 then, compared to the F-18. Because percentage wise (Im making up numbers), the F16 drag might go up by 20%, but the F18 drag only goes up by 10%. Similar story with weight. Yet the F18s speed seems to go down so much more than the F16s speed.

Can someone explain why the Hornet is slowed down this much more by stores? Or do I have more fundamental misconceptions here?

Edited May 30, 2023 by Temetre

[GGTharos]

Why would you make up numbers?  When you make up whatever numbers you want, you get whatever results you're imagining.   The percentages you made up mean precisely nothing, so right off the bat your logic goes out the window

You need actual, real numbers that represent the drag force and the thrust.   But to make a long story short, yes, the F-18 is draggier, its inlets suck (so it doesn't recover as much pressure/thrust at altitude as a Viper) and thrust-to-weight on the Hornet is just lower to begin with.

That doesn't mean there aren't things to tweak on either aircraft in DCS.

[Temetre]

vor 3 Stunden schrieb GGTharos:

Why would you make up numbers?  When you make up whatever numbers you want, you get whatever results you're imagining.   The percentages you made up mean precisely nothing, so right off the bat your logic goes out the window

I dont get at all how you got there. I was using those numbers to show the idea how differences in proportion work. In the most basic way, an F14 is less affected by an Mk-84s drag than an F-16 is by the same bomb. You get it? Because one is bigger.

vor 3 Stunden schrieb GGTharos:

You need actual, real numbers that represent the drag force and the thrust.   But to make a long story short, yes, the F-18 is draggier, its inlets suck (so it doesn't recover as much pressure/thrust at altitude as a Viper) and thrust-to-weight on the Hornet is just lower to begin with.

That doesn't mean there aren't things to tweak on either aircraft in DCS.

Ive actually read the opposite, that the intake of the F-18 works better at high altitude? And the plane is totally fine when clean. 

That doesnt explain why the Hornet is affected so much more by stores than a Viper.

 

Edited May 28, 2023 by Temetre

[CP400]

The F-16 is smaller and moreover needs to test the same payload in the same positions/configurations. Have you tested this? 

[Temetre]

Okay, Ive actually done a test of straight line flying speeds. Now, I can definitely say the differences are less pronounced than I expected. Maybe its because a lot of my experience with the Hornet is from before the last aero update, which IIRC helped it a bunch. But I did find a big difference in missiles and fuel bags:

See bottom of my post for scenario and more numbers, but heres what stood out to me, at 10k altitude, 30% of empty weight in fuel (+full bags if listed) and full mil thrust in straight flight:

F16, clean: 627 TAS

-> 2xMK-84: 615 TAS
-> 6xAim-120: 626 TAS
-> 3x Fuel Pod (2x330,1x300 gallon), 6xAim-120: 607 TAS

F18, clean: 625 TAS

-> 2xMK-84: 617 TAS
-> 2xAim120+2xAim9 (clean): 620 TAS
-> 2xFuel Pod (330 gallon): 609 TAS
-> 2x2 Aim120 (inner wing station): 605 TAS

So the clean air speed of F-16 and F-18 is almost the same, im sure thats an improvement after the last update. But heres what stands out to me:

1. MK-84s cause more slowdown on F-16 than F-18, making the Hornet just a bit faster. This is what I would expect, a smaller low drag plane suffers more from the same amount of drag in bombs.

2. Putting 6x Aim-120s on the F16s pylons, slowed it down much less than the clean 2xAim120+2xSidewinder of the F-18. Here the opposite happens, a less draggy loadout had more impact on the F-18.

3. The F-16, with 3x pods, giving it more fuel than the F-18, and 6x missiles, was faster than the F-18 with 2x 330 pods. Again, the F-18 loses from a smaller fuel+bag load, where the F-16 has an easier time handling a bigger increase in weight+drag.

 

Like, does that make clear what confuses me so much? Similar clean speed, and with MK-84s, the Hornet even is faster. Makes sense, same drag, bigger plane is less affected. 

Yet then any missile or fuel bag issuch a big deal. A clean Hornet with 4x missiles in low drag slots, loses 5 nots, where an F-16 with 6x missile in more draggy slots loses 1 knot. And the fully loaded F-16 with three bags and six missiles is just 20 knots slower, just like a Hornet with its 2x smaller underwing bags. Surely this heavy F-16 loadout here is more drag than two bags on an F-18? 

Suddenly it is reverted; where the MK84 benefits the Hornet, missiles and bags penalize the F-18 to a much greater degree. That is even ignoring the dragg Hornets underwing stations.

Can someone explain me, or at least make a guess why that happens? To me that seems so counter-intuitive. There either must be something big happen (or maybe something is inaccurate, I have no clue).

 

 

--------------------------------------

Here the more specific numbers I checked. Mind the internal fuel is 30% of empty weight, not of capacity:

Spoiler

F16 -> 30% empty weight internal fuel fraction, military thrust, 10K
-> No stores:  627 TAS
-> 2xMK-84: 615 TAS
-> 2xFuel Pod (370 gallons): 614 TAS
-> 6xAim-120: 626 TAS
-> 3x Fuel Pod, 6xAim-120: 607 TAS

F18 -> 30% empty weight internal fuel fraction, military thrust, 10K
-> No stores:  625 TAS
-> 2xMK-84: 617 TAS
-> 2xFuel Pod (330 gallons): 609 TAS
-> 2xAim120+2xAim9 (clean): 620 TAS
-> 2x2 Aim120 (inner wing station): 605 TAS
-> 2/2 (clean), 2x2 inner Aim-120,  central pod: 595 TAS

F16 -> 30% empty weight internal fuel fraction, military thrust, 20K
-> 3x Fuel Pod, 6xAim-120: 592 TAS
-> Above in full AB: 822 TAS

F18 -> 30% empty weight internal fuel fraction, military thrust, 20K
-> 2/2 (clean), 2x2 inner Aim-120,  central pod: 585 TAS
-> Above in full AB:  732 TAS

 

Edited May 29, 2023 by Temetre

[Theodore42]

Ok I'm going to be a pedantic aero nerd and call your test arbitrary BECAUSE the F-16 and F-18 have different design philosophies when it comes to lift.

The F-18 is low wing-loaded, so it has a lot more wing area that generates lift. This also generates more drag. But MORE lift at lower speeds.

The F-16 is a thrust-to-weight ratio fighter... it has tiny wings so less drag at high speeds.... but LESS lift at lower speeds.

Compare and contrast the alpha of the Viper and the Hornet at different speeds. The Viper has really high AoA even at 300kts, but past 400 and the Viper's AoA is sleight. So the Viper always gets an advantage in drag when being tested at military power.

THEREFORE, to test without being accused by pedantic aviation nerds of being arbitrary, you should compare the fuel economies of all those different stores, not just military power. Use the CRUS page on the Viper's DED and the similar feature on the Hornet to achieve the greatest range.

Being fuel efficient with the Viper requires going fast enough that your AoA isn't going to drag you into the mud. That means more power is required to overcome the AoA drag during max range flight.

The Hornet on the other hand, utilizing a low wing loaded design philosophy, generates lift much better at lower speeds. So the Hornet can keep the engines at a lower fuel flow with equal amounts of drag from the stores. The drag from the AoA will be less and the relative range will more more.

That's my theory anyway.

[Temetre]

vor 3 Stunden schrieb Theodore42:

Ok I'm going to be a pedantic aero nerd and call your test arbitrary BECAUSE the F-16 and F-18 have different design philosophies when it comes to lift.

The F-18 is low wing-loaded, so it has a lot more wing area that generates lift. This also generates more drag. But MORE lift at lower speeds.

The F-16 is a thrust-to-weight ratio fighter... it has tiny wings so less drag at high speeds.... but LESS lift at lower speeds.

Compare and contrast the alpha of the Viper and the Hornet at different speeds. The Viper has really high AoA even at 300kts, but past 400 and the Viper's AoA is sleight. So the Viper always gets an advantage in drag when being tested at military power.

THEREFORE, to test without being accused by pedantic aviation nerds of being arbitrary, you should compare the fuel economies of all those different stores, not just military power. Use the CRUS page on the Viper's DED and the similar feature on the Hornet to achieve the greatest range.

Being fuel efficient with the Viper requires going fast enough that your AoA isn't going to drag you into the mud. That means more power is required to overcome the AoA drag during max range flight.

The Hornet on the other hand, utilizing a low wing loaded design philosophy, generates lift much better at lower speeds. So the Hornet can keep the engines at a lower fuel flow with equal amounts of drag from the stores. The drag from the AoA will be less and the relative range will more more.

That's my theory anyway.

Hey, I dont mind being proven wrong by aviation nerds, im writing from the position of relative ignorance. In fact I like hearing from people who know their stuf.^^

Scrutiny als helps me to improve my thought process and communication. I made a mistake in my original post; it said "stores drag", but didnt specify what performance penalty I was talking about. My post wasnt supposed to be about fuel economy with stores; I have clearly not tested that, and I dont think thats a problem for the Hornet. 

I was specifically concerned about top speed. Especially in A2A situations and BVR, the Hornet seems to suffer from its low top speed compared to the F-16, moreso than anything else (like a weak afterburner and lower acceleration). And considering how fast a fully clean Hornet is, the planes problems seems to come how stores create massive amounts of drag.

 

And its really weird. I mean, from the post before, compare these datapoints:

-> 2xMK-84: 617 TAS
-> 2xAim120+2xAim9 (clean): 620 TAS

Two 2xAim120 in body-slots, as well as 2xAim9 in wing tips, almost have the same slowdown effect as a 2000 lb bomb? I know MK84s are well optimized for drag, but doesnt that seem strange? Ofc its a very different plane, but it still strikes me that the F-16 can have 6x Aim-120, two at wingtip, two at (normally more draggy) underwing slots, and loses almost no speed.

Even for top speed I should probably check how the addons affect AOA. Although I dont think those A2A missiles should have a meaningful effect on CoM, and technically I dont think clean slots shouldnt affect CoD/CoL much.

Youre definitely making a good point how Hornet wings create more drag at high speed. I guess the big question would be how stores affect that lift/drag, compared to an F-16. Thats where aerodynamics become insanely complated xD 

Edited May 30, 2023 by Temetre

[GGTharos]

The airflow interaction with the airframe is important so no, you can't assume that an Mk-84 will have the same drag effect when carried on a different airframe.  Even on the same aircraft these effects can be counter-intuitive, ie. on an F-15 the centerline bag as as much drag (actually just a slight bit more) that two wing tanks.  It's the same tank.

The Viper's TWR is much higher as well.  As for what you find in DCS, that's fine, your question's fine but when it comes down to it, what you should be looking at is not DCS performance but the aircraft's performance charts.  DCS doesn't always get it right.

[Temetre]

vor 10 Minuten schrieb GGTharos:

The airflow interaction with the airframe is important so no, you can't assume that an Mk-84 will have the same drag effect when carried on a different airframe.  Even on the same aircraft these effects can be counter-intuitive, ie. on an F-15 the centerline bag as as much drag (actually just a slight bit more) that two wing tanks.  It's the same tank.

The Viper's TWR is much higher as well. 

Yup, Im aware of all those things, thats why im formulating my posts like that. Interesting topic imo, just hard to grasp.

vor 10 Minuten schrieb GGTharos:

As for what you find in DCS, that's fine, your question's fine but when it comes down to it, what you should be looking at is not DCS performance but the aircraft's performance charts.  DCS doesn't always get it right.

Is there actually performance charts detailing this behaviour? Tbh I dont know how to get charts like that, or how to read them.

[GGTharos]

There are charts that show top speed with a certain payload and/or drag index, and the same for acceleration and fuel consumption.

They're probably getting harder to find these days.

 

PS: For the specific aircraft, they assign a 'drag index' to a given piece of equipment that you put on the aircraft so pilots can easily add it up and then reference the charts.

Edited May 30, 2023 by GGTharos

[Tenkom]

Does it sound reasonable that the hornet loses 20kts from carrying 2x amraams on its cheek stations and the Viper loses 1(!)kt from carrying 6x amraams?

No, it doesn't. I am not saying that it's definitely wrong mind you. But it does warrant looking into.

 

Edit: 
I propose a different test.

Since drag is very non-linear when approaching mach 1 it might make more sense to test at speeds around 400 kts.

So get both planes stable at, as close to possible, 400kts and note the fuel consumption with different loadouts. That will take the speed out of the equation. Of course it will introduce the unknown factor of thrust/consumption which is probably not entirely linear and also the AoA will change. But with only testing with a few amraams they should be minor factors.

Edited May 31, 2023 by Tenkom

[Exorcet]

On 5/28/2023 at 12:05 PM, Temetre said:

Not saying anything is wrong or unrealistic, I would just like to understand why this is. I know the F-18 is more draggy than an F-16, and has somewhat weak engines. But the way stores add drag to the plane seems counterintuitive to me, and I wonder if someone can explain it.

The F-16 was built for speed, the Hornet less so. This not only impacts the drag/performance of the clean aircraft but also the aircraft with stores. The USAF uses smaller and less draggy pylons because they wanted more performance out of their plane. The Navy had the Tomcat to handle air to air for a lot of the Hornet's lifetime, so it was fine with the Hornet getting draggy pylons. While the plane is multirole, most of the time it was used as a strike platform. The Swiss actually have different pylons with less drag, and so have better performing Hornets. This is why your made up estimates for the Hornet and F-16 don't work. The drag change isn't the same, not even close. Adding pylons to the Hornet increases drag much, much more.

You can still go fast in the Hornet, but you want to avoid fuel tanks and wing pylons. Wing tip AIM-9's and fuselage AIM-120's are very low drag on the F-18 and if you only take those four missiles you can actually compete with the F-16. You will still be slower, but not worlds slower.

You mentioned not seeing the same effect on other planes, but I'd suggest rechecking. The F-14 can be slowed down tremendously by AIM-54's. The Mirage 2000 doesn't like to be loaded with fuel tanks. The F-16 suffers massively when loaded with some AG loadouts.

 

[Temetre]

Okay, said, done. Test at 400 knots:

-> F16, 10k alt example from before, 400 knots:
- Clean: 2.1 AOA, 4550 PPH fuel usage
- 6x Aim-120: 2.2 AOA, 4760 PPH fuel usage

-> F18, 10k alt example from before, 400 knots:
- Clean: 1.7 AOA, 40.5/40.5 FF*100 fuel usage
- 2x2 clean missiles: 1.8 AOA, 41/41 FF*100 fuel usage

 

And a look back at full military, this time with AoA, the F-16 with fuel usage:

F-16 clean military: 1.5 AOA, 627  knots, 12.880 PPH

-> Aim120: 1.6 AOA, 626  knots, 12.860 PPH

F-18 clean military: 1.1 AOA, 626  knots

-> Aim120: 1.1 AOA, 620  knots

-------------

So, thats kinda interesting. The F-16 sees a not insubstantial increase in fuel consumptions at 400 knots when carrying 6 missiles. Yet it uses a tiny bit less fuel when at full military speed with the missiles.

Meanwhile the Hornet only sees a tiny change of fuel consumption at 400 knots, with the four missile attached.

AoA changes by 0.1 degree for F16 in both scenarios. Maybe one explanation would be that the F-16s intake works better at the higher AoA, so producing more power during 400 knots? But thats just 0.1 degree of AoA, and a notable increase in fuel burn. And why the full military thrust is actually a tiny bit more efficient, I cant tell.

AoA changes can affect intake performance, wings and engine, but Im just confused at this point. This seems weird.

 

 

[bies]

Small hint:

F/A-18 has been designed for A-A configuration with 2x AIM-7 Sparrow/AMRAAM on semi-recessed low drag fuselage pylons plus 2x AIM-9 on wingtip low drag pylons. And internal gun. In this configuration Hornet created low drag and it was capable in air combat.

Taking A-A weapon on wing pylons was possible, but at the expense of disproportional drag increase, making F/A-18 practically a subsonic aircraft. Wing pylons are designed to carry A-G ordinance, they require additional rack in order to accomodate A-A missile and the missile itself create full drag. It's enough to compare drag index of semi-recessed pylon with conventional wing pylon+rack.

[Tenkom]

2 minutes ago, Temetre said:

Okay, said, done. Test at 400 knots:

-> F16, 10k alt example from before, 400 knots:
- Clean: 2.1 AOA, 4550 PPH fuel usage
- 6x Aim-120: 2.2 AOA, 4760 PPH fuel usage

-> F18, 10k alt example from before, 400 knots:
- Clean: 1.7 AOA, 40.5/40.5 FF*100 fuel usage
- 2x2 clean missiles: 1.8 AOA, 41/41 FF*100 fuel usage

 

And a look back at full military, this time with AoA, the F-16 with fuel usage:

F-16 clean military: 1.5 AOA, 627  knots, 12.880 PPH

-> Aim120: 1.6 AOA, 626  knots, 12.860 PPH

F-18 clean military: 1.1 AOA, 626  knots

-> Aim120: 1.1 AOA, 620  knots

-------------

So, thats kinda interesting. The F-16 sees a not insubstantial increase in fuel consumptions at 400 knots when carrying 6 missiles. Yet it uses a tiny bit less fuel when at full military speed with the missiles.

Meanwhile the Hornet only sees a tiny change of fuel consumption at 400 knots, with the four missile attached.

AoA changes by 0.1 degree for F16 in both scenarios. Maybe one explanation would be that the F-16s intake works better at the higher AoA, so producing more power during 400 knots? But thats just 0.1 degree of AoA, and a notable increase in fuel burn. And why the full military thrust is actually a tiny bit more efficient, I cant tell.

AoA changes can affect intake performance, wings and engine, but Im just confused at this point. This seems weird.

 

 

This makes sense to me. The reason the f16 uses more fuel without missiles is because it's going a little faster. Fuel consumption at 100% throttle will increase with the speed.

The f16 will be producing more power at 400kts with missiles simply because it needs to due to the increased drag. So you have to increase throttle and thus increase fuel consumption.

[Temetre]

vor 14 Minuten schrieb Tenkom:

This makes sense to me. The reason the f16 uses more fuel without missiles is because it's going a little faster. Fuel consumption at 100% throttle will increase with the speed.

The f16 will be producing more power at 400kts with missiles simply because it needs to due to the increased drag. So you have to increase throttle and thus increase fuel consumption.

Its just 1 knot difference, but I guess that alone could explain away the ~20pph difference. Its basically the same. But then you get:

- >So at 400 knots, same speed, we got more fuel usage to overcome drag for F-16. But at full military, we got basically the same fuel usage for both loads.

Doesnt that seem strange? Why is the additional missile drag at 626-627 knots suddenly not a problem anymore, when it is an issue at 400 knots? 

Edited May 31, 2023 by Temetre

[Temetre]

edit: Removed a section about a weird bug, went away with restart.

vor 38 Minuten schrieb bies:

Small hint:

F/A-18 has been designed for A-A configuration with 2x AIM-7 Sparrow/AMRAAM on semi-recessed low drag fuselage pylons plus 2x AIM-9 on wingtip low drag pylons. And internal gun. In this configuration Hornet created low drag and it was capable in air combat.

Taking A-A weapon on wing pylons was possible, but at the expense of disproportional drag increase, making F/A-18 practically a subsonic aircraft. Wing pylons are designed to carry A-G ordinance, they require additional rack in order to accomodate A-A missile and the missile itself create full drag. It's enough to compare drag index of semi-recessed pylon with conventional wing pylon+rack.

 

I know how pylons work, and that the 2x AA pylons of the Hornet are very slow. Thats why im noting that I even see a big impact of just 2x fuel tanks, or body-slot missiles.

No config im using has stock pylons removed btw.

Edited May 31, 2023 by Temetre

[Tenkom]

1 minute ago, Temetre said:

Its just 1 knot difference, but I guess that alone could explain away the ~20pph difference. Its basically the same. But then you get:

- >So at 400 knots, same speed, we got more fuel usage to overcome drag. But at full military, we got basically the same fuel usage for both loads.

Doesnt that seem strange? Why is the drag at 626-627 knots suddenly not a problem anymore, when it is at 400 knots?

It does seem strange to me I agree. The 400kts test makes sense, sort of.
At 400kts you spend 4,6% more fuel to haul along the missiles. But at 626/627 kts they are along for free. Nothing in this world is free.

[Temetre]

vor 16 Minuten schrieb Tenkom:

It does seem strange to me I agree. The 400kts test makes sense, sort of.
At 400kts you spend 4,6% more fuel to haul along the missiles. But at 626/627 kts they are along for free. Nothing in this world is free.

Neat, so we probably found a potential inconsistency?  

edit: Also theres this weird bug I found, where sometimes the clean mil thrust top speed becomes 633 instead of 627 after dropping stores. But it only happens sometimes, and normaly (or clean starts) its 627. Independant of fuel. Maybe its limited to MT, not sure.

Edited May 31, 2023 by Temetre

[Tenkom]

I just did a quick test of my own.

So at 10k feet everything identical:
F16 Clean : 646kts TAS @ Mil power
F16 with 6x120s(other pylons removed) : 628kts TAS @ Mil power

[Temetre]

vor 39 Minuten schrieb Tenkom:

I just did a quick test of my own.

So at 10k feet everything identical:
F16 Clean : 646kts TAS @ Mil power
F16 with 6x120s(other pylons removed) : 628kts TAS @ Mil power

Thx. I didnt remove any pylons. Is your clean F-16 without pylons? 

Edited May 31, 2023 by Temetre

[Tenkom]

45 minutes ago, Temetre said:

Thx. I didnt remove any pylons. Is your clean F-16 without pylons? 

 

Yes. Everything that can be removed is removed. Fuel was 100%, I disabled fuel consumption so that wouldn't be a factor.

 

[Theodore42]

As for the increased drag from fuselage stores at high speeds,

I've noticed both the Hornet and Viper hold the stores from their pylons at a slightly downward angle from the chord of the airframe. But the FUSELAGE stores for the Hornet conform to the shape of the fuselage and point at a slightly different angle. If the Viper and Hornet's pylon's stores are calibrated for max stability at the maximum safe speed for the stores, then perhaps (I assume) that also means they're producing the least amount of drag. In other words, at top speed they're pointed exactly into the wind for the least amount of drag possible while the airframe has an AoA of 1G. The fuselage stores have to conform to the angle of the airframe so they can't be calibrated to minimize drag. This would be why fuselage stores perform badly at high speeds-- they're sideways into the wind. At 600+ knots just a degree or two of AoA would produce a lot of drag. Sparrows and even AMRAAMs have great big fins on them you don't want flat into the wind.

Since the Hornet's airframe produces more lift at lower speeds it isn't a big deal to have stores / pylons that produce lots of drag. At slower, more fuel efficient speeds the drag is relatively less inhibiting than at higher speeds.

As far as weight goes, 2x Mk-84s aren't going to reduce your top speed very much just because they add 4000lbs. They will affect your acceleration and maneuverability, but actual top speed is going to be inhibited much more by the drag they produce than the weight they are. ie, compare top speed of the Viper and Hornet with 10% fuel vs 100% fuel (in other words, WAY more than 4000 lbs). The top speed is going to be basically the same, it just takes longer to get there.

[AngelAtTheTomb]

On 5/31/2023 at 9:17 PM, Theodore42 said:

As far as weight goes, 2x Mk-84s aren't going to reduce your top speed very much just because they add 4000lbs. They will affect your acceleration and maneuverability, but actual top speed is going to be inhibited much more by the drag they produce than the weight they are. ie, compare top speed of the Viper and Hornet with 10% fuel vs 100% fuel (in other words, WAY more than 4000 lbs). The top speed is going to be basically the same, it just takes longer to get there.

4000 lbs is a lot, and will requires 4000 more lbs of lift. This means you need more AoA for that lift, and you get more induced drag. Top speed - at least in the real word - is not just a factor of drag, but of weight.

 

This whole thread highlights some of the problems of parametric simulation, especially with a paucity of data like military aircraft. I would assume ED has drag index factors for all available stores, but that's mostly an estimation for fuel planning purposes and the rest is going to involve some guestimation.

[Temetre]

Am 5.6.2023 um 02:22 schrieb AngelAtTheTomb:

4000 lbs is a lot, and will requires 4000 more lbs of lift. This means you need more AoA for that lift, and you get more induced drag. Top speed - at least in the real word - is not just a factor of drag, but of weight.

 

This whole thread highlights some of the problems of parametric simulation, especially with a paucity of data like military aircraft. I would assume ED has drag index factors for all available stores, but that's mostly an estimation for fuel planning purposes and the rest is going to involve some guestimation.

I guess thats about the best answer we can give. Its just a bit messy, with estimations everywhere and stuff. Hopefully the flight model gets more polished over time if theres something wrong.