SU-24 outrun the F-5E?

In DCS why does the SU-24 outrun the F-5E when afaics they both have a very similar top speed in real life?

General web search. Anywhere I looked, the max speed is specified as around 1700kph for both.

If you want to beat the air Defence mission you have to climb and dive on the SU-24s on full burn.

It takes tactics to win besides brute speed or overwhelming firepower.

If you want to beat the air Defence mission you have to climb and dive on the SU-24s on full burn.

It takes tactics to win besides brute speed or overwhelming firepower.

Of course, but I'm just asking the question out of interest, not relating to that mission.

AI in DCS has some advantages like flying with empty weight..and so on.

As an Example the AI MI-26 Helicopter in DCS outclimbs an KA-50 with an Player by far.

Of course, but I'm just asking the question out of interest, not relating to that mission.

F-5E has rather weak engines and thus acceleration, while the Su-24 was designed for supersonic low level air defense penetration so that's not surprising. It would go over Mach 2 at altitude if they kept the variable ramps.

a simple number like a top speed is meaningless -- you have to ask questions like how quickly you can get up to that speed, at which altitude, at what weight, and how long you can sustain it for.

a simple number like a top speed is meaningless -- you have to ask questions like how quickly you can get up to that speed, at which altitude, at what weight, and how long you can sustain it for.

Right, but I am talking about chasing a SU-24 at maximum speed at around 20,000 feet and watching it get further and further away.

Like others said the SU24 is a beast. You have to keep flaps retracted and dive on it to get a shot. Jettison your external tanks and convert potential energy to kinetic, fire from 1 to 1,5 miles out and you should get a hit. I don’t think you can keep up with him for any reasonable amount of time though.

I shot the SU24s down on that mission but it was long ago so I don’t remember the specifics.

This makes me realize how much a SU24 is needed in DCS. She’s a damn beast....

Guys, thanks for your help, but I'm not asking about combat with the SU-24, or acceleration, I'm simply asking why it massively outruns the F-5E in terms of speed when in real life that doesn't appear to be the case. From the data I've seen at least, both seem to have at max of around 1700 kph.

If I follow a SU-24 when I'm at maximum speed in the F-5, then the SU-24 just gets further and further away.

Is this realistic, or an issue with DCS AI?

"Su-24 outruns the F-5E". Nothing surprising here. The F-5 has very weak engines and is the slowest afterburner equiped jet that I can think of. Okay maybe faster than the Mig-17... but that's pretty much it.

Just been trying out another chase and also watching my wingman disappear over the horizon chasing the same SU-24!

Noticed that the maximum speed I can get in level flight is around 425 knots. That doesn't seem right, does it? This chase is happening around 16,000 ft.

RW: Su-24 M1.35 vs. F-5E M1.63. So this would be indeed surprising.

The problem is that usually credible sources like Jane's quote the Su-24 max speed as M1.35 while other sources state M2.0. That's quite a large gap.

Su-24 speed limit is M1.35 only at sea level. The F-5E can only reach M 1.63 at high altitude, where the Su-24 is able to reach Mach 2.18.

That's only M0.85. There's something seriously wrong with your test since the F-5 should easily exceed this speed even with MIL thrust. Max speed at 16000ft should be around M1.25

That's what I'm thinking.

I'm using the Airbase Defence mission and chasing the SU-24 after it has bombed the airfield and started to run for home.

Give it a try and see if you get the same thing. Max speed around 425 knots at 16,000 ft for me.

What could be wrong?

I'll try another scenario as well.

Su-24 engines make a total of 220 kN with afterburner engaged. F-5E engines only 44 kN. That makes less than a quarter of the power...

That's what I'm thinking.

I'm using the Airbase Defence mission and chasing the SU-24 after it has bombed the airfield and started to run for home.

Give it a try and see if you get the same thing. Max speed around 425 knots at 16,000 ft for me.

What could be wrong?

I'll try another scenario as well.

OK, so, I tried the Instant Action Free Flight Mission in Caucasus, dumped the external tank and was getting 650 knots.

So, there is something going on with the Airbase Defence Mission. Can someone else try it?

That's a totaly useless comparison since are you apparently disregarding the rather significant difference in weight and size.

Yes the Su-24 is bigger and heavier but remember, it has folding wings. It reduces its drag coefficient by a huge amount. So not a very draggy plane at all and when you add up the fact it's five times the power of the F-5E... ;)

The Su-24 is a low level attack aircraft from the "fly fast and low to avoid SAMs" era. It is meant to go long distances at very high speeds while carrying a payload.

The F-5 is a lightweight fighter/trainer design. It's meant to be cheap, reliable, and highly maneuverable at low to medium altitudes when at medium to high subsonic speeds.

In a dogfight, the design of the F-5 gives it a large advantage over the Su-24.

In a race, the design of the Su-24 is generally going to give it a large advantage over the F-5.

Not that the F-5 can't get up to a reasonable speed, or that the Su-24 can't pull some turns, but in terms of primary design purpose the Su-24 is much better suited for going fast and the F-5 is much better suited for agility in a dogfight.

They are built for different tasks, and if one tries to outdo the other at the other's intended task it's not surprising that difficulties are encountered.

Pull your airbrake in before you take off.

That's what I'm thinking.

I'm using the Airbase Defence mission and chasing the SU-24 after it has bombed the airfield and started to run for home.

Give it a try and see if you get the same thing. Max speed around 425 knots at 16,000 ft for me.

What could be wrong?

I'll try another scenario as well.

Pull your airbrake in before you take off.

This and also put flap switch to off. Also DCS ai cheats.

Pull your airbrake in before you take off.

Thanks, I occasionally forget, but that's not the answer in this case - sadly!

Just took off with 100% fuel and reached M0.95 at MIL and M 1.25 at MAX thrust at 16000ft.

This is in the Airbase Defence mission, yes? I can't get anywhere near that. Dumping missiles and with a slight descent, I can get 500 knots with full thrust at 16,000, but that's it!

Don't know what to make of all this.

What flap setting are you using?

Nope that was in free flight and at ISA conditions.

 

The OAT in the Airbase Defence mission is +41°C !!! That's the reason for the much lower top speed ;)

 

I'm amazed how precise the BST F-5E performance matches the RW performance data. At IS +20° (35°C) the top speed at 16000ft should be M1.09 and at that what I'm getting as well.

 

IF there's wind unfortunately a serious bug in the F-5 FM results in different top speeds (IAS+TAS) depending if you are flying in a head or tailwind.

OK, thanks again.

Inevitably my original simple question has thrown up a multitude of side issues in my mind now.

1) In very simple terms, what effect does temperature have on speed at the same altitude?

2) I notice that you are always using Mach numbers rather than knots. I thought that up to 25,000 feet it was appropriate to use knots, no?

3) I noticed by observing the instrument, that there is not a linear relationship between Mach and knots as the scale was adjusting - presumably something to do with the variation of the speed of sound at different altitudes?

4) If there is indeed not a constant relationship between Mach and knots, why is it that when typing into to Google x knots always comes out as a linear relationship? Are there built-in conditions with these converters?

5) When looking at reference sites, why is there a stated maximum speed for aircraft without any statement of altitude or temperature?

Any help appreciated!

OK, thanks again.

Inevitably my original simple question has thrown up a multitude of side issues in my mind now.

1) In very simple terms, what effect does temperature have on speed at the same altitude?

It has a huge effect on engine thrust.

2) I notice that you are always using Mach numbers rather than knots. I thought that up to 25,000 feet it was appropriate to use knots, no?

You use what's most convenient. If your chart is in mach numbers, you'll use those.

3) I noticed by observing the instrument, that there is not a linear relationship between Mach and knots as the scale was adjusting - presumably something to do with the variation of the speed of sound at different altitudes?

Exactly.

4) If there is indeed not a constant relationship between Mach and knots, why is it that when typing into to Google x knots always comes out as a linear relationship? Are there built-in conditions with these converters?

They assume sea level.

5) When looking at reference sites, why is there a stated maximum speed for aircraft without any statement of altitude or temperature?

Any help appreciated!

'Just because' :D

The basic limit is indicated airspeed. If for an aircraft it's 850kts, that's going to be a very different mach number at SL vs. 50000'.

Imacken,

Coincidentally, I'm also at the same point in my F-5E learning curve. I just flew the Airbase Defense mission for the first time the other night, and gave it two more attempts last night.

My experience is that I CAN overtake the Su-24s in a tail chase after they drop on my airfield, but it's very slow and requires dropping centerline tank, full burner and trimming for level flight. I don't have the precise airspeed numbers, will check later when I fly again tonight. My best result in three attempts so far is a head-on AIM-9P5 launch on both Su-24s to dissuade them. They both pulled off to avoid, and my wingman shot one down before it could drop. The other recovered quickly and bore in for a drop on my airfield, but I chased him down afterwards with guns and killed him ~20 miles out as he raced for home. I like the suggestion about getting a high altitude perch first and then diving on them, although there isn't much time in this mission before they're over the airfield. Will try that tonight.

Separate question:

Once the two Su-24s are dispatched, I'm instructed to RTB. Wizard (AWACS) is calling clear or very distant targets at 100 mi+. When I check F5, I see four other Su-24s with external ordnance somewhere over the Caucasus mountains. Am I supposed to refuel and rearm and be ready for them or is the mission over after those initial two Su-24s?