performance charts for different weights V1/R/V2/APP/Vne/Vgx/Vfe

[WildBillKelsoe]

as above, Is there charts for calculating takeoff and landing V speeds? how about other V speeds?

 

Also, iirc, there was a glisade voice saying nizhe/vyshe glisade guiding you, what happened to it?

[Sideslip]

I don't know if you can find the charts online, but you can calculate your own Vref (landing speed) anyway. Load it up to max gross and find the stall speed with flaps and gear down. Vref is 1.3 X Vso (stall speed in landing configuration). If you know the stall at max gross you can estimate it for all weights by multiplying the stall speed by the square of actual weight divided by max gross.

 

Vref = 1.3 X Vso X squareroot(weight/max gross)

 

So making up numbers here, but say Vso is 250kph and max gross was 20000kg:

Vref @ 20000kg = 1.3 X 250 = 325kph

Vref @ 16000kg = 1.3 X 250 X squareroot(16000/20000) = 290kph

 

The only other important V speeds are Vfe Vle and maybe Vne. For flaps and gear you can do what I did. Fly around lowering and raising them while increasing speed until it breaks. After testing I settled on 400kph for landing flaps and gear extension in SU-25. Above 350 the plane shakes like crazy with gear down but I didn't have a gear problem until over 500kph. For Vne you could just dive at the ground full AB from 10000m until the plane falls apart, but really are you ever going to encounter Vne? This isn't real life we are talking about.

 

The rest of the V speeds really aren't as important as one might think in a sim environment. Approach at what's comfortable, rotate when it wants to lift off, V1 is almost meaningless in a plane that can take off easily with 1 engine and likewise with V2. Vmc is also not much concern with centrally mounted engines. It has afterburners, it's not a fat lethargic airliner that was designed to use 10000ft runways.

 

And what the heck is Vgx? Gear extension? That is Vle or Vlo.

 

I do wish better manuals were provided with FC3 aircraft. The SU-25 one is almost a joke. The few weapons that are described seem to have had their blurbs written by pulling a stat out of a hat. One cluster bomb it states the maximum dispersion and the other states the altitude and airspeed for release.

[esb77]

I've never seen such charts. There are partial answers in the documentation, and there's a manual in Spanish that you might be able to find by using advanced search of this forum. Not enough to calculate it for a particular runway and conditions though.

 

Most of this stuff you can flight test in the sim if you want to. At one point I did most of them for the Su-25T in DCS, and I think it took me about a week of flying test missions a couple of hours per day.

 

For landing speed, the best solution is to not do it based on speed.

 

Instead do it based on AoA.

 

When you're on final get yourself in landing configuration with gear and flaps, speed to around 300 km/h IAS, and then trim to your desired landing pitch. I can't remember what that is supposed to be for the Su-27, but my guess would be somewhere around 12 to 15 degrees. A few degrees less than what would produce a tailstrike on the runway. Use the stick for fine control of AoA to keep it exactly on target, and then use the throttle to control your altitude and stay on glideslope (increase throttle to gain alt, decrease to lose alt). This method will automatically manage your airspeed to be appropriate for your aircraft weight if you are staying on slope and at the correct AoA.

 

That said, if your IAS is below 240 or above 330 you might want to abort and go round.

 

 

Vne generally requires a clean plane and several minutes of full AB, so isn't really an issue unless going for a speed or climb to altitude record. If you have more than just a few stores there will be so much drag that you won't be able to reach Vne.

 

I know the flaps are controlled by the flight computer in normal operation, but I don't remember if having manual control set to down will override this and allow you to break them by overspeeding. I'd have to fly it to check.

[Ironhand]

...

 

For landing speed, the best solution is to not do it based on speed.

 

Instead do it based on AoA.

 

When you're on final get yourself in landing configuration with gear and flaps, speed to around 300 km/h IAS, and then trim to your desired landing pitch. I can't remember what that is supposed to be for the Su-27, but my guess would be somewhere around 12 to 15 degrees...

I think it might be an AoA of 10°. At least that number always seems to give me the right airspeed for my landing weight.