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Difficult landing training


draconus
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I misunderstood. I thought you were holding speed with the brakes applied. Would be interesting to see how braking would affect the lower numbers.

I might add that, when I find the time.

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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Like I promised: the great "Sideslip test"!

In this track I fly 100% heavy Su-25T. I approach Mineralnye Vody as it is the longest runway in Caucasus (although I wasted some of that lenght). There is no wind and temperature is 50°C. Don't mind the flight but the touchdown is gentle to make sure no tires are broken during this phase. Then I apply full wheel brakes and after a while full throttle. In this setting aircraft is accelerating while I try to stay on the runway until finally taking off with tires... wait for it... intact.

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...Don't mind the flight...

 

:crazy:

 

Wow that was scary! No offense, but if I ever meet you in person and you are offering flights, I'm not letting any family members get on board. I think I know how your tires blew previously :P

 

What equipment are you using? That reminds me of when I used to have a Logitech 3D extreme pro, it was soooooo difficult to fly with that thing.

 

Some friendly advice. When you are coming in to land, set yourself up sooner, meaning configure the aircraft. You did not need to be on the edge of a stall like that. At that weight, you should have had the approach flaps (combat flaps) out under 450kph. And you don't need to wait until you put the gear down to set landing flaps either.

 

I am about to leave for a few days on a motorcycle trip, but maybe I can squeeze in one test before I go...

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Just to make sure the entire runways was used, I tested it myself. I did my best to break for the whole length of the runway. Starting weight was 19691kg (191kg over max gross). I did the takeoff and circuit just to get a feel for the aircraft, just fast forward to the landing.

 

 

Can'tBreakAnyMoreThanThat.trk

 

 

Landed as close to the threshold as I could, landed very firm, held the brakes until pretty much the end of the pavement, tried to keep the speed between 290kph and 320kph and had no blown tires.

 

 

Whether the tires were hotter from the braking or not, you cannot blow tires on the SU-25 in this sim by use of the brakes on landing. You can do it a whole lot of other ways, but not by braking.

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Interesting, sorry for the confusion. I thought I had done so in the past (my landings are sufficiently gentle these days I don't blow tires by any way :p

 

I wonder if that is something they do not model at all, or it's a hit and miss thing, a relic flaw of the older AFM intermediary flight modeling. They make me go to work just about the time I get ready to mess with DCS, so I haven't been able to do anything yet =/

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Sideslip, the track I downloaded isn't the track you describe. It's one of you rollinging down the runway without taking off until your tires start bursting at around 445 kph.

 

Draconus, unfortunately your track didn't play back correctly. I'll try it again in the morning, when I'm more awake.

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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Sideslip, the track I downloaded isn't the track you describe. It's one of you rollinging down the runway without taking off until your tires start bursting at around 445 kph.

 

Draconus, unfortunately your track didn't play back correctly. I'll try it again in the morning, when I'm more awake.

 

Are you sure you are playing the right tracks? His track worked fine for me and I have never once rolled an su25 down a runway at 445kph. I only made 270kph about 2/3 down the runway.


Edited by Sideslip

System specs: i7 3820 @4.75Ghz, Asus P9X79LE, EVGA GTX1080SC @2100mhz, 16GB Gskil DDR3 @ 2000mhz, 512GB 960EVO m.2, 2 X 512GB 860EVO SATA3 in RAID0, EVGA Supernova 850W G2, Phantek Entho Luxe White. CPU and GPU custom water-cooled with 420mm rad and lots of Noctua fans.

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Wow that was scary! No offense, but if I ever meet you in person and you are offering flights, I'm not letting any family members get on board. I think I know how your tires blew previously :P

I specificaly said "don't mind the flight" as it was not part of the test :) It was not my best and I was not focused enough. I'm an Eagle driver and don't have a good feel for the Frogfoot yet (and the whole trimming thing). I do it for fun and to try something new. Thanks for advices anyway. I think I wouldn't take anyone on a braking test tour either ;)

 

 

What equipment are you using? That reminds me of when I used to have a Logitech 3D extreme pro, it was soooooo difficult to fly with that thing.
I have T-Filght HOTAS X and actually read good things about that Logitech here on a forum.

 

 

You did not need to be on the edge of a stall like that.
Unless you have it already calculated you set the minimum landing speed that way. It's the aircraft feel and experience lacking in this sample.

 

 

 

@zhukov032186: Should we report it then as a bug or missing feature?

 

 

@Ironhand: I hope you're not refering to how the track ends. Shouldn't left it like that but I was so excited to look at the tires externally...

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Are you sure you are playing the right tracks? His track worked fine for me and I have never once rolled an su25 down a runway at 445kph. I only made 270kph about 2/3 down the runway.

That's what I get for trying to do something, when I'm dead tired. In your case, I was watching someone else's track entirely (discovered whose by peeking in the Tacview folder to see what I had viewed last night). So I viewed the correct track just now. Very nice flying, by the way. I'm not surprised that you had no blown tires. Unless you add skidding to the mix, you won't blow anything--as far as I can tell--until you're around +430 kph. That's without brakes applied. And I suspect the numbers won't change, if you apply brakes.

 

...

@Ironhand: I hope you're not refering to how the track ends. Shouldn't left it like that but I was so excited to look at the tires externally...

 

I re-downloaded your track and played it again. Same track I downloaded last night. You land and initially slow down, then gradually increase your speed down the length of the runway until you take off again with tires intact. You then retract the landing gear and flaps, throttle back, extend the gear again and attempt an off-runway landing with too much downward momentum that doesn't end well.

 

Tires at the end of the run in my viewing:

 

attachment.php?attachmentid=192032&stc=1&d=1534254749

Screen_180814_094603.thumb.jpg.c9848fd56aeff34b14f4e4ecef32515a.jpg

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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Well...perhaps I'm wrong about whether or not braking has an effect on the tires. Drakonis, I hope you don't mind but I used your track--too lazy to make my own mission--and took control from the start and made the landing--that aircraft was HEAVY. :)

 

I saved the track and played it back twice taking control at the same point (at 390 IAS on the HUD after landing) after scrubbing flaps and throttling up. In the first I applied brakes starting at 390 IAS on the HUD. In the 2nd trial I did not apply brakes. With brakes engaged, tires started blowing at 430 IAS in the F2 view. Without brakes, I was up around 470 IAS in the F2 view before bad things started to happen.

 

BTW, after landing, the cockpit steam gauge and external view show different IASs). This is true in both the Su-25t and Su-27 and probably others. The F2 view is always higher. I've been taking the readings from the F2 view during the course of all this but perhaps I shouldn't be.

 

Anyway, for your viewing pleasure, the two tracks are attached. If you don't change views, you'll see the cockpit view suddenly snap to a slightly different viewpoint at around 390 IAS on the HUD after the landing. That's the point at which I take control and things become different. Until then, everything (the landing, all inputs, etc) should be identical.

Drakonis Track-Ironhand at Controls-BRAKES.trk

Drakonis Track-Ironhand at Controls-NO Brakes.trk


Edited by Ironhand

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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...You did not need to be on the edge of a stall like that...

 

Unless you have it already calculated you set the minimum landing speed that way...

Just noticed the above exchange...

 

A less exciting way is to maintain a 12° AoA on the way down. That'll keep you at either the right speed or slightly above for your landing weight down the slope. Full flaps, maneuvering flaps, or no flaps. Doesn't matter. It'll adjust your landing speed accordingly as long as you're sitting on that AoA. But, then again, that's one of those things you learn with experience in the aircraft...unless you've already read it in a manual somehwere.

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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...I have T-Filght HOTAS X and actually read good things about that Logitech here on a forum.

 

 

Unless you have it already calculated you set the minimum landing speed that way. It's the aircraft feel and experience lacking in this sample...

 

 

I would rate the VKB (and I assume Virpil) sticks about a 9 or 10, CH as a 5 when brand new, and the Logitech about a 3 from personal experience. From what I've read I think the T-flight might be about a 5.

 

 

Regarding the 25, when I started flying the 27 the first thing I noticed was "wow this thing is sensitive". In the 25 everything is a little sluggish and you have to stay ahead of the aircraft, I assume much more so than the F15.

 

 

Regarding landing and flap speeds, most of these aircraft have an AoA gauge. For most aircraft, 10 degrees is as high as you want to be for landing (or any level flight really). I don't know where Ironhand got 12 from, but I just use 10 as it's easy. Also, I took a look at the SU-27 with 10 degrees nose up and it's scary close to scraping the exhaust nozzels on the runway. So basically, any time you have more than 10 degrees AoA either speed up or lower more flaps.

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Well...perhaps I'm wrong about whether or not braking has an effect on the tires...

 

 

Well I think that proves it, the heat from braking (not necessarily the brakes themselves) is definitely modeled, so don't be applying breaks when you land at 400kph in the su25. :pilotfly:

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ASUS PG348Q. VKB Gladiator Pro w/MCG, X-55 throttle and MFG Crosswind.

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...

 

Regarding landing and flap speeds, most of these aircraft have an AoA gauge. For most aircraft, 10 degrees is as high as you want to be for landing (or any level flight really). I don't know where Ironhand got 12 from, but I just use 10 as it's easy. Also, I took a look at the SU-27 with 10 degrees nose up and it's scary close to scraping the exhaust nozzels on the runway. So basically, any time you have more than 10 degrees AoA either speed up or lower more flaps.

:) I find 12° brings me to the runway at a good airspeed and pitch angle for landing. But 10° works, too. It just lands you at a higher airspeed and a bit flatter. The Su-27 is a different airplane and for that airframe you should be below 10°. At 10° or more in the -27, you have a difficult time seeing the runway. So 8° is about right.

 

As to the effects of braking, yes, there is definitely something there.

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:) I find 12° brings me to the runway at a good airspeed and pitch angle for landing. But 10° works, too.

10-12° is a too high approach AoA IMO. Just watched a few RL Su-25 videos and the pitch attitude on final is usually between 2-3° nose up.

 

On a 3deg glideslope this translates into a 5-6° approach AoA which is in line with many slats equipped airplanes.

 

Touchdown does occur with a close-to-10° nose up attitude and on a few videos.


Edited by bbrz

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...On a 3deg glideslope this translates into a 5-6° approach AoA which is in line with many slats equipped airplanes.

 

Touchdown does occur with a close-to-10° nose up attitude and on a few videos.

 

 

Are you actually seeing the gauges on the videos or just mathing it? Don't forget the angle of incidence. Either way I'll stick to 10 degrees.

 

 

Also, don't quote me on it but at max gross I think the 25A can only get as low as about 5 degrees AoA at cruise speed without shaking from the turbulence of some rocket pods. It just seems a tiny bit low to me.

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1. Are you actually seeing the gauges on the videos or just mathing it?

2. Don't forget the angle of incidence.

3. Either way I'll stick to 10 degrees.

4. Also, don't quote me on it but at max gross I think the 25A can only get as low as about 5 degrees AoA at cruise speed without shaking from the turbulence of some rocket pods.

 

 

1. Seeing it on the gauge and measuring it on the screen.

2. Doesn't apply.

3. Whatever makes you happy.

4. You are comparing apples and oranges. With the flaps extended the usable AoA reduces a lot, especially with large flaps like on the Su-25. (and you usually don't land at max gross weight)


Edited by bbrz

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10-12° is a too high approach AoA IMO. Just watched a few RL Su-25 videos and the pitch attitude on final is usually between 2-3° nose up.

 

On a 3deg glideslope this translates into a 5-6° approach AoA which is in line with many slats equipped airplanes.

 

Touchdown does occur with a close-to-10° nose up attitude and on a few videos.

I stand corrected then.

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You said that 10-12° is ok for you and there's nothing wrong with that. I just wanted to mention that the Su-25 is usually flown faster on approach.

The faster you go, the higher the speed stability and controllability. The higher required power setting also means better engine acceleration.

Furthermore (especially in gusty conditions) it's nice to have a certain amount of energy/speed to trade.

Once you are really close to the runway you can start reducing the speed of course.

 

A higher approach speed doesn't automatically mean a higher landing speed.

 

If you fly the approach at 10-12° AoA you simply can't reduce the thrust to idle before or above the threshold (if you can reduce it at all before touchdown).

 

Last but not least, the higher the speed, the greater are the chances for a greaser and at least IRL the Su-25 seems to touchdown very smooth most of the time. :)

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You said that 10-12° is ok for you and there's nothing wrong with that. I just wanted to mention that the Su-25 is usually flown faster on approach.

The faster you go, the higher the speed stability and controllability. The higher required power setting also means better engine acceleration.

Furthermore (especially in gusty conditions) it's nice to have a certain amount of energy/speed to trade.

Once you are really close to the runway you can start reducing the speed of course.

 

A higher approach speed doesn't automatically mean a higher landing speed.

 

If you fly the approach at 10-12° AoA you simply can't reduce the thrust to idle before or above the threshold (if you can reduce it at all before touchdown).

 

Last but not least, the higher the speed, the greater are the chances for a greaser and at least IRL the Su-25 seems to touchdown very smooth most of the time. :)

We're pretty much on the same page for all the reasons you mention. In the Su-27, for instance, I normally leave the IAP at around 380-390 and cross the threshold at landing speed. That requires slowly retarding the throttle on the way down to hit the fixes properly. For someone new to an airframe holding a steady speed is usually a bit easier which is why I suggested 12° which seems to work well for "weatherless" missions. At any rate, good points.

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You land and initially slow down, then gradually increase your speed down the length of the runway until you take off again with tires intact. You then retract the landing gear and flaps, throttle back, extend the gear again and attempt an off-runway landing with too much downward momentum that doesn't end well.

You overinterpret this. After take off I retracted gear and flaps by muscle memory, then it came to me I should check the tires, so gear down again just to see it externally with no regards to what the aircraft is doing whatsoever.

Good finding though on the braking influence. At least something is there.

As for the approach alpha you all make a good point. Seems like simple Rtfm would suffice for a lot questions asked but not really much about tires there. Flying and testing Frogfoot I'm having a good time. Sure I miss that velocity vector but that sluggish feeling that makes you think like it's a few times heavier is what I came for. And because it's russian. And it's for free. Such a steal.

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You overinterpret this. After take off I retracted gear and flaps by muscle memory, then it came to me I should check the tires, so gear down again just to see it externally with no regards to what the aircraft is doing whatsoever.

Good finding though on the braking influence. At least something is there.

As for the approach alpha you all make a good point. Seems like simple Rtfm would suffice for a lot questions asked but not really much about tires there. Flying and testing Frogfoot I'm having a good time. Sure I miss that velocity vector but that sluggish feeling that makes you think like it's a few times heavier is what I came for. And because it's russian. And it's for free. Such a steal.

Ahhh...so you weren’t trying to land on a hillside. Too bad. You should try it sometime. Loads of fun. :)

 

Unfortunately, the tires, when you let the gear down again, looked just fine in my viewing. Guess I should have posted that screenshot instead.

 

And the T’s a hoot to fly as long as you don’t load her down too much. Have a great time with her.


Edited by Ironhand

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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Seems like simple Rtfm would suffice for a lot questions asked but not really much about tires there.

Rtfm doesn't help much since it says nothing about weight takeoff or landing weight when mentioning the speeds!

 

Just tested with 10% fuel for the minimum approach speeds written in the DCS manual and I get the following AoA values.

Final approach 290km/h = 5°AoA

50m height 260km/h = 8° AoA

5m height 250km/h = 9° AoA

 

Haven't flown the Su-25 in a while and I have forgotten that it's a really nice plane with nice handling :) If it would have a clickable cockpit I would fly it much more often!

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