Some things I noticed

[humptydumpty]

Hi,

 

I am more on the Mig21 in a learning curve but do indulge in the excellence of the Flanker.

 

I love flying low and very fast and noticed the control stiffening above Mach 1 around 600 kts (hope that is above mach 1), I could not roll the aircraft , is this correct ?

 

A couple of other things , I am not sure when this happened but noticed the engine RPM off i.e it went all the way back to 0 but as soon as I did some maneuver they started rising like it was an autostart.

 

I needed to ask shouldn't there be a punch kinda thing when the AB is applied ? Is wake turbulence modeled ?

 

I have an extended stick about 2 feet and the flanker is highly sensitive at high speed (not read the speed indicator as to what the speed was ) on the ailerons is this also supposed to be similar in the real one ?

 

Rgds.

[mvsgas]

More information on SU-27 manual, page 114

You have a copy in your game folder

https://docs.google.com/viewer?url=http%3A%2F%2Fcdn.akamai.steamstatic.com%2Fsteam%2Fapps%2F250310%2Fmanuals%2FDCS_Su-27_Flight_Manual_EN.pdf%3Ft%3D1415658308

 

http://www.fighter-planes.com/jetmach1.htm

Edited October 26, 2016 by mvsgas

[humptydumpty]

More information on SU-27 manual, page 114

You have a copy in your game folder

https://docs.google.com/viewer?url=http%3A%2F%2Fcdn.akamai.steamstatic.com%2Fsteam%2Fapps%2F250310%2Fmanuals%2FDCS_Su-27_Flight_Manual_EN.pdf%3Ft%3D1415658308

 

http://www.fighter-planes.com/jetmach1.htm

 

Thanks

[DarkFire]

Hi,

 

I love flying low and very fast and noticed the control stiffening above Mach 1 around 600 kts (hope that is above mach 1), I could not roll the aircraft , is this correct?

 

The roll curves will change as speed approaches and then exceeds M1. The controls will be stiffer above Mach 1 which will result in slower maximum roll rate.

 

A couple of other things , I am not sure when this happened but noticed the engine RPM off i.e it went all the way back to 0 but as soon as I did some maneuver they started rising like it was an autostart.

 

It is an auto-start but was caused by the engines being starved of fuel. The Su-27 has a gravity fed (as opposed to a pressurised) fuel system. So, if the G load on the aircraft is at or less than 0 (e.g. inverted flight or a hard nose-over) the engines will be starved of fuel. There is a small pressurised cache tank which supplies fuel when G is at or less than 0 but it has a tiny capacity. For an example, during inverted flight at sea level at maximum AB the cach tank will be drained in much less than 10 seconds. As soon as the cache tank is empty the engines will begin to spool down. If you catch it in time and restore G to more than 0 then the cache tank will fill and your engines will usually re-start due to ram air pressure.

 

Hope all that made sense. If you watch actual video footage of Su-27s the pilots will never nose-over, rather they roll inverted and pull. It's also true that the Su-27 really, really hates negative G and especially negative AOA.

 

 

I have an extended stick about 2 feet and the flanker is highly sensitive at high speed (not read the speed indicator as to what the speed was ) on the ailerons is this also supposed to be similar in the real one?

 

Apparently the professional flight model that the DCS Su-27 enjoys has been tested and signed off by actual Su-27 pilots, so in that respect it's probably pretty realistic to the real thing. Try using input curvature for pitch and roll. A good setting for a normal size stick is somewhere between 15 and 25, but with your extended stick try between 5 and 15 for pitch and roll - should make the aircraft a lot smoother to fly.

[humptydumpty]

The roll curves will change as speed approaches and then exceeds M1. The controls will be stiffer above Mach 1 which will result in slower maximum roll rate.

 

 

 

It is an auto-start but was caused by the engines being starved of fuel. The Su-27 has a gravity fed (as opposed to a pressurised) fuel system. So, if the G load on the aircraft is at or less than 0 (e.g. inverted flight or a hard nose-over) the engines will be starved of fuel. There is a small pressurised cache tank which supplies fuel when G is at or less than 0 but it has a tiny capacity. For an example, during inverted flight at sea level at maximum AB the cach tank will be drained in much less than 10 seconds. As soon as the cache tank is empty the engines will begin to spool down. If you catch it in time and restore G to more than 0 then the cache tank will fill and your engines will usually re-start due to ram air pressure.

 

Hope all that made sense. If you watch actual video footage of Su-27s the pilots will never nose-over, rather they roll inverted and pull. It's also true that the Su-27 really, really hates negative G and especially negative AOA.

 

 

 

 

 

Apparently the professional flight model that the DCS Su-27 enjoys has been tested and signed off by actual Su-27 pilots, so in that respect it's probably pretty realistic to the real thing. Try using input curvature for pitch and roll. A good setting for a normal size stick is somewhere between 15 and 25, but with your extended stick try between 5 and 15 for pitch and roll - should make the aircraft a lot smoother to fly.

 

Darkfire thanks for the explanation. I am always confused with 0 and Negative G's. I will search for the flanker videos.

 

I was under the impression that the extension would do away with the curves.

 

 

Thnx.

Edited October 27, 2016 by humptydumpty

[DarkFire]

Darkfire thanks for the explanation. I am always confused with 0 and Negative G's. I will search for the flanker videos.

 

I was under the impression that the extension would do away with the curves.

 

Thnx.

 

No problem. To be honest a stick extension usually does mean that you don't need curves. I'm surprised since a 2 foot extension should give you smooth-as-oiled-silk control. I wonder if something else is going on. Is your stick fully calibrated under windows for example? That gave me problems for a while when I changed from Win7 to Win10.

[humptydumpty]

No problem. To be honest a stick extension usually does mean that you don't need curves. I'm surprised since a 2 foot extension should give you smooth-as-oiled-silk control. I wonder if something else is going on. Is your stick fully calibrated under windows for example? That gave me problems for a while when I changed from Win7 to Win10.

 

It's properly caliberated and even in Xplane it is fine.

 

On high speed the roll is hyper sensitive. I will check again though.

 

Could be due to the logitech potentiometers, but I have bought hall sensors now so I need to mod it not that I know how to :).

Edited October 27, 2016 by humptydumpty

[humptydumpty]

This is not correct!

What DarkFire said concerning the joystick setup. Even above Mach 1 you should be able to roll the Su-27 without any problems.

 

Ok I will test it again, in the F15 and the Mig21 it seems fine above mach 1 but I will retest.

[Pocket Sized]

If you're doing Mach 1 at low altitude the roll rate will reduce a lot.

 

It's because there's so much air going over the control surfaces that the hydraulics can't move them very far. The 27 has very big ailerons that require a lot of pressure to move unlike the smaller rolling surfaces of the F-15 and MiG-21.

 

In other words, stay below 1100-1300 kmh indicated and you'll be fine. For maneuvering you don't want to be above 800-900 anyway because you can easily overstress the wings and rip them off ;)

[DarkFire]

If you're cruising around in the Su-27 you should be at cruise throttle setting. It varies between 83% and 87% RPM depending on altitude but 85% is always a good choice.

 

Through no coincidence, unless you're flying at above ~8,000m this will always give you an IAS and a TAS that's effective for beginning combat in that you can carry out a maximum ITR turn which will then bring your speed down in to the best STR range for the Su-27.

 

When I watch YouTube videos of people flying the Su-27, I really don't understand why so many people zoom around at 100% RPM. Unless you're climbing to altitude or accelerating for a BVR F-pole all it does is waste fuel.

 

Roll rate will decrease with TAS for exactly the reason Pocket Sized explained.

[Weta43]

It's because there's so much air going over the control surfaces that the hydraulics can't move them very far. The 27 has very big ailerons that require a lot of pressure to move unlike the smaller rolling surfaces of the F-15 and MiG-21.

 

That's interesting- not something I've given a lot of thought.

I'm curious about the mechanism.

Thinking out loud here...

Surely if it were simply that the hydraulics can't deflect the control surfaces as far at low altitude because the higher air density of the air increases the mass of air they're moving for a given deflection, then as the amount of roll inducing torque generated by the control surface is presumably proportional to the reaction of the airframe to the force needed to move that air, then you just get a higher reaction force / amount of roll inducing torque per degree of control surface deflection, and all other things being equal, would ultimately have the ability to get a higher roll rate for a given hydraulic pressure at low altitude (as the pressure isn't the limiting factor at high altitude, it's the maximum deflection angle / stalling of the surface).

Is the problem actually that the rest of the wing has to displace air in order to rotate, and with the increased density of air, the force needed to rotate the wing against the air increases, so even though the control surfaces generate more torque around the aircrafts COG, the resistance of the denser air to the rotation of the wing's main lifting surfaces also increases, decreases the net torque and so decreasing the roll rate ?

 

So the force needed to deflect the surface goes up as the density of air increases, and so proportionally does both the roll inducing force generated by the control surface, but at the same time, the roll resisting forces generated by the rest of the wing go up more quickly because of the greater area of the wing, and so you can't get the same amount of roll for the same amount of force applied to the control surface ?

Edited October 29, 2016 by Weta43

[humptydumpty]

THanks Guys, that's some explanation, I know about the air density thing but I have noticed the twitchy at high speed also at altitudes I am not really sure what is happening, is it my logitech attack 3 that is the issue or what. I got myself some hall sensors so maybe that could help with the precision but they don't seem to work with the magnets.

 

About the control stiffness above mach 1 at low altitude is only noticed in the Flanker but it seems to be random.

 

I have put the Y Saturation to 70% for the roll and the twitch seems to be a lot better at least I can land the flanker without the asymmetric roll.

 

I need to fly more to check with the other aircraft like the F15 / Mig21 will revert back with the tests.

 

Rgds.

[humptydumpty]

It is twitchy even in the Mig21 , this is strange as it shud not be the case , I had to give 5 curves to Pitch and 10 for roll.

 

Anyone have knowledge about using the Hall Sensors on the joystick ? I got hall sensors but they are not working with Magnets instead if I hold it then I can move the axis

Edited November 3, 2016 by humptydumpty

[winchesterdelta1]

I notice myself that i always fly with 100% engine power in the 27. And i also notice it's not even needed most of the time. It's a habit from the F-15 i can not simply get rid of. I try to change this for a long time now. But i keep going back to 100%.

[DarkFire]

I notice myself that i always fly with 100% engine power in the 27. And i also notice it's not even needed most of the time. It's a habit from the F-15 i can not simply get rid of. I try to change this for a long time now. But i keep going back to 100%.

 

I know what you mean, but going from 95% to 100% RPM gives you exactly 0 extra speed. Have a read of this thread:

 

https://forums.eagle.ru/showthread.php?t=147556

 

And this thread:

 

https://forums.eagle.ru/showthread.php?t=165967

 

For a scientific analysis of Su-27 flight performance and why cruise throttle is between 83% and 87% RPM. AFAIK the Russian VKS uses 85-87% RPM as their real cruise throttle setting. The only times you need 100% RPM are if you're climbing to altitude or accelerating to Vmax with wet thrust.