SU-27 questions: trim, flaps, autopilot

[stray cat]

2 questions about the su-27

 

1. On neutral trim it feels very hard to keep the plane level. It wants to pitch up unless the trim is set vertical to counter it very agressively. Is that normal or something being wrong with it?

 

2. What are the things that look like flaps on the front edges of the wings? How to control them?

 

3. Is it required to make use of the different autopilot settings to keep the plane steady (like on the KA-50) or is it just a matter of having a firm grip on the stick?

[Weta43]

That's 3 questions :)

 

1/ it is normal, you have to trim whenever the flight parameters change (speed, altitude, fuel, weapons, etc.)

2/ leading edge slats - devices to increase lift. They're controlled automatically by the FCS (as are the flaps if you look back) to maintain the best trade off of lift and drag.

 

3/ No, (& no), just trim a lot and with practice you'll find it becomes quite controllable (even with a gentle grip :) )

[Svend_Dellepude]

1: according to the manual this is normal.

 

2: Those are slats, or leading edge flaps. operation is automatic in elation with AoA.

 

3: Trim out the plane to make it steady. big changes in speed (especially subsonic) and altitude will require more trimming.

when maneuvering, try to make more fluid movements with the stick until you get a better feel for the FM.

The autopilot can be used at your discretion. It seems a little unfinished right now, but maybe thats how it's supposed to be.

make sure you have a trimmed aircraft before engaging and manage your speed wile engaged.

 

Hope i made sense.

[stray cat]

Thanks.

[Comes]

The auto pilot seems to have problems with the new flight model. When I use it to follow a route, it wobbles all around as soon as the plane turns to another heading. It does not crash and after a few minutes the plane flys straight again. But I don't think that this behaviour is normal.

[51GRIZZLY]

The auto pilot seems to have problems with the new flight model. When I use it to follow a route, it wobbles all around as soon as the plane turns to another heading. It does not crash and after a few minutes the plane flys straight again. But I don't think that this behaviour is normal.

 

I can confirm that problem .... allso using "Attitude Hold" the plane starts Rocking left-right like a boat with wawes coming in from the side.:pirate:

[Ironhand]

The auto pilot seems to have problems with the new flight model. When I use it to follow a route, it wobbles all around as soon as the plane turns to another heading. It does not crash and after a few minutes the plane flys straight again. But I don't think that this behaviour is normal.

The AP follows the course line between WPs. So, as you leave WP1 and turn toward WP2, the AP in Enroute mode will cut back beyond the direct heading for the next WP to intercept the course line. If the new direction is severe enough, it'll often cut back and forth across the course line until it can settle in on it. If that's what's happening, then that is how it should be working. I was playing with the various AP modes this morning and didn't notice anything out of the ordinary.

 

 

Rich

[51GRIZZLY]

Maybe i should mention that i got a CH fighterstick, throttle and pedals.

And im absolutely sure its not a hardware problem since it all Works smooth as butter when im flying my MIG-21.:joystick:

BTW welcome back to the forums Ironhand .... still a big fan of your tutorials.

[159th_Viper]

I can confirm that problem .... allso using "Attitude Hold" the plane starts Rocking left-right like a boat with wawes coming in from the side.:pirate:

 

Trim first to the desired attitude and then hit LAlt-1 for Attitude Hold.

[Ironhand]

Trim first to the desired attitude and then hit LAlt-1 for Attitude Hold.

In my case--where it worked as advertised--I wanted to hold a banked climb. I was reasonably (but not perfectly) trimmed for my starting point and then pulled up into my banking climb. Selected Attitude Hold and everything went smoothly.

 

EDIT:

...using "Attitude Hold" the plane starts Rocking left-right like a boat with waves coming in from the side.:pirate:

This I definitely haven't experienced. Could it be speed related? As in too little of it?

Edited November 14, 2014 by Ironhand

[dartuil]

The flanker is harder to control then the eagle but the flanker still seems more maniable in turn fight when u can handle all the trim thing.(Noob me :) )

Crazy plane i like it.

[Gnark1ll]

Ah Im glad others have been having problems with the current autopilot...(and its not just me..phew!)

 

I have to say that it has tried to kill me a couple of times since the new FM release ; D (my fault activating it before being nicely trimmed and stable)

 

I shall be watching with interest if this is resolved or is the expected behaviour... Not the 'trying to kill me ' bit...but the very noticeable (and thus likely innefficient) 'wobble' that is introduced in all modes of autopilot (Radar alt hold, H hold, baro alt hold)....

 

Sometimes it seems to 'settle down' after a while, and sometimes it gets worse and worse.... I take it others have been seeing the same thing? The only mode I have not tried yet is 'route following AP'...

[merlin851526]

Ah Im glad others have been having problems with the current autopilot...(and its not just me..phew!)

 

I have to say that it has tried to kill me a couple of times since the new FM release ; D (my fault activating it before being nicely trimmed and stable)

 

I shall be watching with interest if this is resolved or is the expected behaviour... Not the 'trying to kill me ' bit...but the very noticeable (and thus likely innefficient) 'wobble' that is introduced in all modes of autopilot (Radar alt hold, H hold, baro alt hold)....

 

Sometimes it seems to 'settle down' after a while, and sometimes it gets worse and worse.... I take it others have been seeing the same thing? The only mode I have not tried yet is 'route following AP'...

Having the same problem and it has actually inverted me over a few times and Isaac Newton took over after that:music_whistling:. Have tried engaging after trim but still get the same wobble.Moreover once it settles on route and turns to the next way point it begins to wobble again in the turn. Don't know might be rudder related.Or maybe I'm going wrong somewhere.

[Svend_Dellepude]

I've noticed that the autopilot has some problems where it seems it keeps chasing itself.

This happens at high altitude and/or at low speeds.

It still stands that you should trim before engaging and if there is significant change in speed when engaged you should disengage and trim again and re-engage as needed.

It still seems a bit buggy and I'm sure it'll get fixed.

If you take a look in F2 when autopilot is wobbling you'll notice that rudder and elevator (lateral) movements are a bit clunky, so there is probably something fishy in those channels.

[Nedum]

I got this "dutch roll" behavior in Autopilot if my IAS(? The speed shown in the HUD in nav modus) is under 610 kph. Above that speed the "dutch roll effect" is gone.

And I got this dutch roll effect at each landing under 280 kph. It begins with a little effect and if you slow your speed down to 240 kph (ILS landing), the effect isn't to counter anymore.

 

Another strange thing is, that the Su27 has no big signs before a stall accours. You can pull at very slow speeds from 1 ms to another a full stall. No shaking, no left or right slew, there is mostly an instand stall at speeds around 400 kph. You bleed in less a second 150 kph without pulling the stick hard. It's more like the Su27 is drifting with her back from one second to another.

I have tried some barrel rolls and I was with ease in a stall @ about 300 meters high and 400+ kph speed.

The question is: why can I pull with so less stick use so much AoA if there is not enough drag and speed to do so? And as long as I power up the thrust during a stall, it makes the stall even more a stall. At a nose down stall with full afterburner the AC is not accelerating anymore! Why?

Is the FM really all about physics or is there always a little bit "Cobra" in this FM?

Without to hit the "S" button I can pull the Su27 nose in less of 2 seconds 90 degrees up @450 Kph. I have tried this with the F15 and can't do this not nearly as with the Su27. And the F15 has no dutch roll behavior even at low speeds.

Edited November 26, 2014 by Nedum

[Svend_Dellepude]

The SU-27 has relaxed stability and the F-15 is more stable not to mention that F-15 has a very different control system compared to the SU-27, so that is why the react so differently to pilot input.

[Thumper1606688436]

Nedum, watch this video to understand how greater AOA causes stalling.

 

ItMgrp8Cgfg

[Nedum]

Nice trolling indeed! :censored:

[bernp]

Fun and informative video. Thanks for posting it Thumper.