New Su-27 Model Avionics Issues

[Azrayen]

Not a chance. The AP should works fine on an ILS approach at approach speeds with no wobble.

 

After checking the manual: Agreed, thanks :)

 

ACS provides:

(...)

¤ Automatic return to the programmed airfield and landing approach down to the altitude of 50-60 m in accordance with input from the navigation system

[TAW_Impalor]

I play the campaign, and "Route following" mode completely ignores the altitude. Almost crashed me into the mountain...

[Shepski]

Use route following plus alt hold "h" together for lateral and vertical NAV.

[wilsonov]

Right on !

[Bozo]

When I had first Downloaded the F-15C (not the Flaming Cliffs, but just the plane itself) It also had uncontrollable pitching issues. Things that happen due to the physics involved yes, but also made the plane really difficult for a new user like myself to pilot.

 

Then came the patch that -to my best guess- added an auto-trim mechanic that fixed everything. New it handles like a dream. Again, I see the same thing happening with the Su-27, but I hear the actual plane doesn't have auto-trimming? If this is so and the game has mimicked it, well...It's sad, because I like the plane, but can't fly it as it is. I'd have to manually trim it I guess. Hopefully I don't need to during flight. Dog fighting would be a nightmare :joystick:.

 

My issues with the plane are:

 

1) Taxing (takes a dangerous amount of throttle just to get the plane moving, and then when you reduce throttle, because you're now moving fast enough to roll the plane it all of a sudden doesn't have enough momentum to continue forwards and comes to a dead stop, unless I "again" add more throttle).

 

2) The uncontrollable pitching upwards when exceeding certain air speeds.

3) The need for the plane to straighten out as if the auto-pilot kicked on when banking at times.

4) The tires blowing easily, but that's a known issue according to the person who replied to my support ticket.

 

Sorry about length, just hope this plane gets some fixes. It's my fave -- unless it stays as it is lol.

[Valium]

1) I don't see anything special here. To move the plane you have to add more power but after that you have reduce it because the plane will accelerate.

It's like in car. If you still have the gas pedal pressed, the car will be still accelerating. If you accelerate the car you have to give more power at the beginning but after that you have to reduce it to keep constant speed, right?

2) You have to use trimming ( alt + t or ctrl + t ) It's not that difficult. You have to pay attention if you begin to fall the nose because if you do it too fast, you'll lose control.

3) After using auto-pilot I usually trim the plane, after that I press ALT+1 ( you set the altitude but your plane can fly higher ) and then I use H. It's important to hold joystick until you notice that plane flies at the same level ). If you want to control the plane you have to switch off the auto-pilot by using ALT+9 combination.

4) The tires blowing easly. You have to make a good landing and after that use P button to open parachute. That's how russians plane're landing.

One thing here : you have to choose an airport where you can make refueling, etc. If parachute was used, you should have to ask Ground Crew about 'refueling and rearming'. After that parachute will be able to use once again.

 

And never use 'S' button during flight with Su-27. Every move of joystick will cause doing 'cobra manoeuvre'.

Edited March 27, 2015 by Valium

[DarkFire]

3) The need for the plane to straighten out as if the auto-pilot kicked on when banking at times.

 

Sorry about length, just hope this plane gets some fixes. It's my fave -- unless it stays as it is lol.

 

Do you mean that when you bank the aircraft it begins to return to wings-level? If so, I also wondered about this and to my lasting astonishment it's apparently how the real Su-27 - at least the one modelled in DCS - behaves.

[bolek]

1) I don't see anything special here. To move the plane you have to add more power but after that you have reduce it because the plane will accelerate.

It's like in car. If you still have the gas pedal pressed, the car will be still accelerating. If you accelerate the car you have to give more power at the beginning but after that you have to reduce it to keep constant speed, right?

No, I think that what the OP meant was that there is no way to taxi at safe speed at a constant throttle setting (which is certainly possible in a car :)). But AFAIK, this is realistic and has to do with how the nozzles operate in the 70-80% throttle range (it was explained somewhere here, can't find it now). You have to keep adjusting the throttle all the time (basically short bursts of power). Don't wait until you reach your target speed before pulling back on the throttle.

4) The tires blowing easly. You have to make a good landing and after that use P button to open parachute. That's how russians plane're landing.

The problem is that the tires blow up when you hold the brake for a few seconds even at something like 30km/h. This does not seem realistic. But, you get used to it. Basically, on the ground, both throttle and brakes are best applied only in short bursts (< 2 seconds).

[Ironhand]

...

1) Taxing (takes a dangerous amount of throttle just to get the plane moving, and then when you reduce throttle, because you're now moving fast enough to roll the plane it all of a sudden doesn't have enough momentum to continue forwards and comes to a dead stop, unless I "again" add more throttle)...

As Bolek noted, you need to play with the throttle and this, evidently, is how it is if you are using both engines for thrust. I talk about it toward the end of the following video after I land at around 15:00 minutes. Watch the tach as I taxi back from the runway:

 

 

 

Rich

[Bozo]

Great input, thanks all who replied! Good video too! I use keyboard controls, so I think things get a bit more hairy because of this.

Edited March 29, 2015 by Bozo

[uboats]

@Ironhand nice vid!

[Shepski]

There is too much drag after the jet starts rolling at taxi speed. you should be able to taxi at idle thrust once you have momentum.

 

The strength of the tires is poorly modeled and there is no way they should be blowing so easily.

 

The 2 bugs could be related in that there is too much friction drag associated with the modeling of the tires which is why the jet slows down too quickly and the tires blow too easily.

[Ironhand]

There is too much drag after the jet starts rolling at taxi speed. you should be able to taxi at idle thrust once you have momentum...

I'm going to disagree with you at least partially on this one. There might be a bit too much drag--not sure about that--but I do know that I have watched a number of videos of Flankers taxiing with those nozzles (or at least one) opening briefly and, then, closing as they move down the taxiway. So there seems to be more to the story than just an error on DCS's part.

[Shepski]

I'm going to disagree with you at least partially on this one. There might be a bit too much drag--not sure about that--but I do know that I have watched a number of videos of Flankers taxiing with those nozzles (or at least one) opening briefly and, then, closing as they move down the taxiway. So there seems to be more to the story than just an error on DCS's part.

Hi Rich!

 

I have seen videos as well and this Russian Knights video,

after making a 90 degree turn you see thrust being added(nozzle movement) in order to get to get momentum back. This is normal because you slow down for sharper turns.

 

In DCS you can't taxi in a straight line at idle thrust once you are at taxi speed. It feels like the brakes are being applied and you are slowed and stopped.

 

Watch the following video of a Flanker at taxi speed and idle thrust taxiing in a straight line followed by a Falcon at idle thrust.

 

Edited March 30, 2015 by Shepski

[karambiatos]

The tyres only blow at full fuel, if you have low fuel you can happily have them at full all the time.

Edited March 30, 2015 by karambiatos

[Ironhand]

Hi Rich!

 

I have seen videos as well and this Russian Knights video,

after making a 90 degree turn you see thrust being added(nozzle movement) in order to get to get momentum back. This is normal because you slow down for sharper turns.

 

In DCS you can't taxi in a straight line at idle thrust once you are at taxi speed. It feels like the brakes are being applied and you are slowed and stopped.

 

Watch the following video of a Flanker at taxi speed and idle thrust taxiing in a straight line followed by a Falcon at idle thrust.

 

I see what you mean in that video. He had the same length roll that I've managed from time to time in the sim. :) Wish I had made a YouTube Playlist of the taxiing samples I was referring to. They all involved straight line taxiing (no turning) where you'd see the feathers close and open. When I have a chance, I'll see if I can find some again if you'd like.

 

Idle thrust? You sure about that?

[Shepski]

Idle thrust? You sure about that?

Yup. We taxi the 737 at idle thrust and if we are light we have to ride the brakes to keep our speed down. The Learjet was taxied at idle thrust as well.

 

Think of the amount of thrust coming from the huge engines on the Flanker, even at idle, and the rolling resistance of the jet. I wouldn't be surprised if they have to ride the brakes.

 

Read the bit here on taxiing the F-15...

 

https://books.google.ca/books?id=oJ6wvqUMWkUC&pg=PT13&lpg=PT13&dq=f-15+eagle+taxi+at+idle+thrust?&source=bl&ots=uFLRLxqCa5&sig=KYmGMoPGAHKD_xnNriQEIVUQCoI&hl=en&sa=X&ei=FtsZVeXgFYy0sAT3moKoBg&ved=0CCUQ6AEwAg#v=onepage&q=f-15%20eagle%20taxi%20at%20idle%20thrust%3F&f=false

[uboats]

The tyres only blow at full fuel, if you have low fuel you can happily have them at full all the time.

 

80% w/o payload does not agree with you;)

[karambiatos]

80% w/o payload does not agree with you;)

80% fuel is low fuel?

[uboats]

80% fuel is low fuel?

you said blow ONLY at full fuel

[Ironhand]

Yup. We taxi the 737 at idle thrust and if we are light we have to ride the brakes to keep our speed down. The Learjet was taxied at idle thrust as well.

 

Think of the amount of thrust coming from the huge engines on the Flanker, even at idle, and the rolling resistance of the jet. I wouldn't be surprised if they have to ride the brakes.

 

Read the bit here on taxiing the F-15...

 

https://books.google.ca/books?id=oJ6wvqUMWkUC&pg=PT13&lpg=PT13&dq=f-15+eagle+taxi+at+idle+thrust?&source=bl&ots=uFLRLxqCa5&sig=KYmGMoPGAHKD_xnNriQEIVUQCoI&hl=en&sa=X&ei=FtsZVeXgFYy0sAT3moKoBg&ved=0CCUQ6AEwAg#v=onepage&q=f-15%20eagle%20taxi%20at%20idle%20thrust%3F&f=false

Based on what you're saying, that would make the Flanker the exception. It'll be interesting to see how this might change in the future. I still keep thinking, though, that I've seen the throttles being played with in a number of videos. Of course we have no idea if there's a gentle slope involved or if they are trying to gain speed or whatever the reason for it might be.

[esb77]

A few physical traits of the Flanker to keep in mind:

 

The fan is only 905 mm. I suspect that the nozzles at full open are close to this wide or even wider. That's going to be a huge loss of exhaust velocity and consequently thrust compared to when the nozzles constrict.

 

It's designed for unimproved strip operations. This means that at the very least the tires are likely to be built in a way that creates significantly higher rolling resistance (the price you pay for durability and high flotation), and it's possible the mechanical resistance in the bearings is greater if they have a higher surface area to cope with shock loadings from a rough strip.

 

Combine that with 25 to 30 tonnes of load, and the rolling resistance might reasonably soak up all of the idle thrust.

 

 

My impression is that most high bypass turbofans on commercial passenger and cargo planes either don't have variable nozzles or even if they do, don't constrict anywhere near as much in terms of proportion as the Flanker's do. Plus having a bypass ratio 5-10 times greater than the AL-31 is going to produce a large performance gain in terms of thrust at low speeds, you'd expect the passenger planes to have a greater proportion of engine thrust available at idle than a Flanker.

Edited March 31, 2015 by esb77

[Shepski]

If the tires had as much rolling resistance as you assume it would greatly increase take off distance which sacrifices payload on shorter runways so I don't think the tires have a noticeable effect.

 

The Su-27 is similar to the F-15 in all regards with the exception of avionics so if Eagle pilots have to ride the brakes taxiing at idle thrust do you not think the Flanker should be able to taxi at idle thrust too?

 

If the Su-27 had to taxi with more than idle thrust it would waste a lot of fuel on the ground prior to take-off which is the primary reason jets are designed to taxi at idle thrust.

[dartuil]

I would like the su33 to go PFM.

Air refueling and naval option would be crazy!!

[Shadowless]

Is the Su-27 have to trim forward a lot in the reality after take-off and gear-up?