SU-24 outrun the F-5E?

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?

I replied to you in the thread I started about this mission here https://forums.eagle.ru/showthread.php?t=203771

This thread wasn’t supposed to be about that mission, it was just a general question. However, in regard to you asking the same question, I don’t know, that’s why I started the other thread.

No one has come up with an answer yet, and that is why I asked how to contact Belsimtek. No one has answered that one either!

Having dabbled in the other missions in that series, I’m not sure how they are ended either. Be nice to know!

Imacken - I saw the reply in the other thread, thanks. I just didn't have anything else to add. I don't know the answers, nor do I know how to contact Belsimtek on this particular mission question. Like you, I'm watching to see if anyone else has additional experience with these questions. Cheers.

The DOW is 5 times higher on the Su-24 and even with the wings swept back, span and thickness are still significant higher and we are not even talking about the fuselage cross sections/area... ;)

 

And it would be really nice to know if the Su-24 top speed is M1.35 or M2.0......

DOW has a negligible impact on an aircraft's speed. Drag and thrust are the factors to take into account here.

The F-111F has similar size, shape, weight and thrust as the Su-24 and its top speed is Mach 2.5. How could the Su-24 possibly be stuck at Mach 1.35? Unless it had a major design flaw it would make no sense at all.

DOW has a negligible impact on an aircraft's speed. Drag and thrust are the factors to take into account here.

 

The F-111F has similar size, shape, weight and thrust as the Su-24 and its top speed is Mach 2.5. How could the Su-24 possibly be stuck at Mach 1.35? Unless it had a major design flaw it would make no sense at all.

Intakes.

Early Su-24s had variable geometry inlets and could do Mach 2+. Later on, they got simplified, but this limited the aircraft's max Mach. Since low altitude speed mattered more for Su-24 than absolute top speed at high alt, this wasn't seen as an issue.

Anyway, those huge engines and well swept wings would probably give Su-24 a pretty decent acceleration advantage over F-5. And at that fairly low-ish altitude, their max Mach is probably close. So I don't think it would be surprising if Su-24 would be hard to catch for F-5E in a tail chase at that altitude. Then, like others have said, there's the whole "DCS AI always cheats" thing. For example, I doubt temperature difference affects AI aircraft's thrust performance the way it does for high quality flight models in player flown aircraft.

I'd be curious to hear Su-24M2 flight performance from people who know their Fencer stuff, or better yet from some actual documents if any are available.

That is expected. At low level SU-24 is faster then F-5E. In DCS almost anything 4th gen can outpace and out accelerate F-5E. However its turn rate is great.

Intercept head on with AIM-9P5, or from side aspect (of target). TU-22M, SU-24, and TU-160 at their best performance are difficult or impossible to intercept from any pursuit aspect. However when they turn, to avoid SAM, AAA, or missile, they slow down, that may give you an opportunity.

SU-24M can carry R-60M for self defense, so take that into consideration. SU-34 can carry latest AA radar and all aspect R-73 missiles.

2) This depends on speed as well. Once you are approaching high subsonic speeds you usually use Mach.

If you are talking about performance you always use true airspeed, either knots or Mach. If you use IAS (or EAS) you need to convert is to TAS. When using Mach you don't need to convert anything.

As GGTharos pointed out it depends on the table layout as well, and in case of the F-5E (and most other jets) the flight envelope table is in Mach.

 

5) The quoted maximum speed is usually given at S.L. and/or at the altitude where the true airspeed/Mach is highest. In case of the F-5E in clean config the max speed can only be reached at 36000ft.

That's why I initially asked if the altitude is stated in your sources. Without this piece of information the quoted max speed is of limited value.

In the super sonic regime many jets reach their max speed at around 36000ft, e.g. the F-14, F-15 and F-16.

Performance is always valid for ISA conditions (15°C, 1013hpa SLP) since temperature has a big impact on performance, takeoff run, climb rate, max speed, max alt, etc.

Thanks again. I don't understand a lot of your jargon, but I'll try and translate later!

http://www.hochwarth.com/misc/AviationCalculator.html

Put this on another panel, assuming you have more then 1. You can convert various indicator.

IAS indicated airspeed . Also called Calibrated Air Speed. Speed that your instrument shows.

TAS - True Air Speed. Speed of aircraft through airmass, regardless of altitude. Indicated airspeed is affected by altitude, as air density lowers as altitude increases. TAS is closer to ground speed then IAS.

ISA (not IAS above) is International Standard Atmopshere. How altimeter calculates altitude, and how speedometer calculates Indicated Air Speed.

https://en.wikipedia.org/wiki/International_Standard_Atmosphere

Most vital function for aviation calculator is calculation of QNH. The altimeter setting that is set prior to landing.

Put in height of landing airfield , in meters, and put in Tower QFE given to you, when you declare Inbound. The calculator computes QHN which you set the altimeter setting to. F-5E does not have radar altimeter, like other aircraft in DCS. So altimeter is the only height reading you have, in cockpit. Important if you are approaching field in low visibility, and in dangerous terrain. Or taking off in low visibility in dangerous terrain.

Most vital function for aviation calculator is calculation of QNH. The altimeter setting that is set prior to landing.

Put in height of landing airfield , in meters, and put in Tower QFE given to you, when you declare Inbound. The calculator computes QHN which you set the altimeter setting to. F-5E does not have radar altimeter, like other aircraft in DCS. So altimeter is the only height reading you have, in cockpit. Important if you are approaching field in low visibility, and in dangerous terrain. Or taking off in low visibility in dangerous terrain.

Thanks for that.

I know it's a topic that is discussed a lot on these forums, but personally, I use the QFE given by the tower for landing. Then I know my height above ground during landing.

Higher weight = more lift = higher drag.

Of course but the impact is very small. The added AoA needed to compensate for the weight is very limited. Test it for yourself (aircraft loaded with 100% fuel vs 30% fuel for example) and you will see that differences in speed are quite negligible for an aircraft flying straight and level.

F-5E altimeter is designed for QNH. QFE is an artifact of RUssian procedures programmed by ED. If you do not convert, and use QFE as altimeter setting, you get altitude above the field, not actual barometric above MSL altitude. Maps have feature terrain marked in feet MSL. If you are landing on airfield at elevation of 1840 feet MSL (Nellis), you want the altimeter to read about that altitude, and not zero. It is too easy to get confused, and low visibility makes things worse. So use QNH.

As far as I know, QFE is used in only DCS: Mig-21Bis, KA-50.

Western platformsuse QNH.

Don't forget that regardless of altimeter setting prior to takeoff, or prior to landing. When flying above 18,000 feet MSL, the setting is set to 29.92. When desending for flight below 18K, QNH of nearest friendly field. You have to declare inbound to that field, get QFE, then cancel inbound. In enemy territory, 29.92 is used.

If you want to be precise standard (29,92) is set at transition altitude which is 18000 feet in the USA but in other areas of the world varies and is usually lower.

Russian procedures also use the metric system as altitude measuring speed wind velocity etc. a remnant of Soviet procedures and a real pain especially when assigning flight levels to incoming traffic that is flying in feet...

DCS really needs to get its sh!t straight and address these stuff at some point.