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Posted (edited)

I'm using this subforum since I don't know exactly where it should belong.

The other day right after the latest patch I was flying a mission with some people in the Syria map (Bassel Al-Asad airport) with -21s. Finished the task, RTB, I believe RSBN was behaving weird (yellow line in KPP perhaps fits better) after just previous patch in which it was working flawlessly but that's another story and I'll have to further check. We all were set to land, I was going first.

I have to explain first I use a particular procedure I kind of invented for myself after watching some real MiG-21 videos, I come @400Km/H to the end and just chop the throttle at threshold and make a not so long and nice flare to let the aircraft set by itself on the ground, hence trying not to get into the lower side of the power curve. To my surprise the aircraft bounced 😲, made it to the air again at less than 300Km/H and finally, and luckily, I could set it again on ground though I was baffled on what did I made differently (and wrongly) from other times to that result. Anyway, I was thinking on what happened but then my two teammates came and bounced either, so it wasn't me and something definitely changed from last week before the patch.

One of my squadmates said it might be related to the map instead, he recalled some bug of "oily surfaces" fixed either in the previous patch, but I'm not sure if that's on the map or the plane since I guess it should happen for all modules and not only MiG-21.

I have a track but it's for the whole mission, many minutes long (about an hour), and I don't know how I could cut it.

 

S!


Edited by Ala13_ManOWar
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"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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Hmm, I was wondering about that, too, thinking I was just doing shitty landings. So I'm not the only one who can't seem to stop bouncing around. At least the carriage is sturdy enough to take it. Maybe it was tuned to be a little too springey.

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As I said, I also thought it was a bad landing from my part at first, but since the rest of the flight had it too, and we are flying MiG-21 every week since several months ago, I can confidently say it's a change from last week to this one.

 

S!

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"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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The suspension has been fixed (finally), so it offers more resistance now. You came down hard and bounced, before it probably would've just bottomed out without resistance. This was the same fix as the problem with the wheels clipping through the ground and the aircraft riding the brake drums in hard turns on the ground. Simplest answer is not to touch down slower than 280km/h, and if you bounce slower than that, immedately apply mil thrust and initiate a go-around.

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The suspension is worse then ever, we fought several years for a fix, they fixed it some months ago & now it's broken again. No other airplane bounces like Mig-21 ATM. I greased it down & it still bounced. Look at this video they are coming down pretty hard & not a single bounce!

 

i7 8700k@4.7, 1080ti, DDR4 32GB, 2x SSD , HD 2TB, W10, ASUS 27", TrackIr5, TMWH, X-56, GProR.

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Have yet to experience a bounce personally, and in any case I'm glad to be able to make sharp turns on the ground without slowing to a glacial pace to avoid the suspension bottoming out, even with a light load.

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Posted (edited)
10 hours ago, rossmum said:

The suspension has been fixed (finally), so it offers more resistance now. You came down hard and bounced, before it probably would've just bottomed out without resistance. This was the same fix as the problem with the wheels clipping through the ground and the aircraft riding the brake drums in hard turns on the ground. Simplest answer is not to touch down slower than 280km/h, and if you bounce slower than that, immedately apply mil thrust and initiate a go-around.

And that's why I explained the whole situation, not just the possible "bug"? or whatever it is. With the technique I explained I don't settle the aircraft on the ground, it does on its own once the flaring speed is just the right one at it "falls" slowly and gently (the gently a delta winged MiG-21 can) to the ground. Besides, how on Earth is an aircraft bouncing back to the air with no speed at all?? Indeed, how on Earth is an aircraft bouncing back to the air at or below stall speed?? Once settled on the ground I always keep my (25cm long) stick back and, on the contrary to RL images seen on YT, it never holds the nose up after touch down, that tells me there's no speed to fly at all (and that the module wasn't correct in that regard either, but that's another story). I know what a bounce is, bounces always happens on excess of speed, and I hadn't any excess in speed, that's why you flare in the first place. So, something has changed, but I'm not sure it's correct.

 

S!


Edited by Ala13_ManOWar

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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Posted (edited)

I was able to produce a fairly aggressive nosewheel bounce by conducting an extremely (as in, full fuel, full drop tank, 4 missiles) overweight landing and letting the nose drop as soon as the wheels touched, but even on subsequent overweight landings avoided any bounce at all by holding the nosewheel off a little longer and then letting the stick out gently. Aerobraking is possible, it can just be difficult to get the right stick deflection unless you have a substantial stick extension (I don't, I have none and it sits on a desktop), as you need more precision to do it.

 

Despite that, the bounces I produced weren't enough to make me airborne again unless I already had the stick pulled right back as though trying to aerobrake, and I had enough flying speed to waste a few seconds fumbling for my flaps to bring them back up to T/O so I could plug in burner and go around.

 

I don't know how you guys are regularly encountering bounces. My first theory would be landing overweight, my second would be touching down too slowly so descent rate is allowed to build out of control. The only advice I can give sounds really jerky but in all honesty: just work on your landings, because this is not a problem I've encountered outside of intentionally causing it just now. The fact you're qualifying "gently" like that tells me that your descent rate is too high because you're too heavy, too slow, or both, because there should be no need to qualify it. There is absolutely no reason the DCS 21 can't be greased in so gently you barely notice the wheels touch, it just needs practice.

 

Do some landings as you normally would, and keep an eye on both airspeed at time of touchdown, and vertical speed in m/s. I'm curious now.


Edited by rossmum
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Well, then I guess it's not impossible it's something on the map, and/or the airbase, with this module and not just a MiG-21 thing as I also said.

 

 

Quote

I don't know how you guys are regularly encountering bounces.

That's the question, I don't 😉 . I'll try some more tests anywhere else either since I was sticking right now to the place and mission we are currently using.

 

S!

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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I have no way of testing it, but I feel like there is some variation in airfields, if that makes sense. PG's Lar always feels really rough even in the F-5, to the point it stands out in my mind. I don't know if that'd be enough to explain it, though.

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From the manual; Short final speed for a clean -21 which is under the maximum landing weight (fuel gauge reads 700 L or less) is 330 - 340 km/h. Flare smoothly at 8-10 m to arrest and stop the descend while reducing the thrust slightly to settle at 290 - 300 km/h. If carrying ordinance or overweight then the speeds are even higher and closer to tire speed limit which is 330-340 km/h.

 

Aerobraking is a recipe for disaster with the current flight model, and frankly I do not see the point as you don't even need the chute to slow down.

 

 

 

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The 21 is my ride since it came out in 2014 so I am confident when I say that I never experience bounces, I always tend to make smooth landings around 270/280 to 310 (when in overweight and using 2. stage flaps) and keeping the nose up in the air and then gently drop it down (since I have the opportunity to watch such landing IRL). Lets say that 7 out of 10 landings are smooth (some wind and turbulence always activated).

It is very much possible and I have been doing it with every FM/Ground physics change to date (guess I can adapt easily). It takes long practice and I even use a 25cm extension since the beginning and fly 99% of the time on the Caucasus map. Sometimes it's really hard to explain to someone exactly what technique to use or how much to move the stick etc. because it's a case of, as we would say here, getting a feeling for the AC and also personal preference on the controls setup (curves, deadzones,...). I very rarely and if ever watch the gauges except the speedometer on landing because of muscle memory and it rarely fails..ILS is another matter ofc. I talked to RL Fishbed CroAF drivers who tried the DCS module and all of them agreed that if it were so easy to fly it in RL, everyone would fly them 😃

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On 5/30/2021 at 9:13 PM, CoBlue said:

The suspension is worse then ever, we fought several years for a fix, they fixed it some months ago & now it's broken again. No other airplane bounces like Mig-21 ATM. I greased it down & it still bounced. Look at this video they are coming down pretty hard & not a single bounce!

 

Post a track.

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Holy moly. What is it now. The suspension was actually fixed recently and is fine now. Don't land overweight and too hard otherwise you'll bounce. 

 

Fly this profile and you gucci:

 

76586867.PNG

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16 hours ago, cro_mig_21 said:

The 21 is my ride since it came out in 2014 so I am confident when I say that I never experience bounces, I always tend to make smooth landings around 270/280 to 310 (when in overweight and using 2. stage flaps) and keeping the nose up in the air and then gently drop it down (since I have the opportunity to watch such landing IRL). Lets say that 7 out of 10 landings are smooth (some wind and turbulence always activated).

It is very much possible and I have been doing it with every FM/Ground physics change to date (guess I can adapt easily). It takes long practice and I even use a 25cm extension since the beginning and fly 99% of the time on the Caucasus map. Sometimes it's really hard to explain to someone exactly what technique to use or how much to move the stick etc. because it's a case of, as we would say here, getting a feeling for the AC and also personal preference on the controls setup (curves, deadzones,...). I very rarely and if ever watch the gauges except the speedometer on landing because of muscle memory and it rarely fails..ILS is another matter ofc. I talked to RL Fishbed CroAF drivers who tried the DCS module and all of them agreed that if it were so easy to fly it in RL, everyone would fly them 😃


Can you elaborate on the pros and cons of using an extension with the-21? Any curves?

 

1 hour ago, Skysurfer said:

Holy moly. What is it now. The suspension was actually fixed recently and is fine now. Don't land overweight and too hard otherwise you'll bounce. 

 

Fly this profile and you gucci:

 

76586867.PNG

 

Would you be able to re-draw this in English? I know it’s self explanatory but I would really love to read the pilot’s notes. 

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26 minutes ago, Maxthrust said:

Can you elaborate on the pros and cons of using an extension with the-21? Any curves?

 

Pros: you have more finesse in your controls,  as the real aircraft also uses a substantial stick extension and is very sensitive in both pitch and roll

 

Cons: uh, you need some more room for your setup, I guess.

 

Curves should only really be needed without an extension (or with a very short one), IMO. Flying with an extension-less TM Warthog I have like 2 degrees of stick throw between documented AoA limit and THE WOBBLE ZONE and it makes it quite hard to ride the edge when I need to.

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Posted (edited)
5 hours ago, MiG21bisFishbedL said:

Post a track.

Here 7% fuel I think. Those landings are deliberately a little hard. Sure you can do ok landings, but if a little hard the suspension shouldn't throw the 21 up in the air like a glove, also look at the absence of wheel damage.

 

I had alot of crashes, so I couldn't show everything that I wanted. Those are the only tracks I could get.

mig21 land 1 .trk mig21 land 3 b .trk mig21 land ok stol chute .trk


Edited by CoBlue

i7 8700k@4.7, 1080ti, DDR4 32GB, 2x SSD , HD 2TB, W10, ASUS 27", TrackIr5, TMWH, X-56, GProR.

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2 hours ago, Maxthrust said:

Would you be able to re-draw this in English? I know it’s self explanatory but I would really love to read the pilot’s notes. 

 

Actually yes, been meaning to translate these pilots notes to some people for a while. You can mostly make it out as a non-russian speaker if you stare at it long enough but I guess some people would always like it the easy way. 

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Your approach is kinda unstable, I'd suggest approaching closer to 400 IAS and then slowing to cross the fence at 350. You slammed down so hard the ventral tank came off in the first landing, going to F2 view right at touchdown probably didn't help with arresting the descent rate. With that said, it's hard to tell exactly what's going wrong... looks like not enough flare? I've had 'harder' landings in terms of descent rate, but only ever experienced a bounce like what you did there when I straight up crunched it into the ground due to battle damage.

 

From the looks of it your problem is coming specifically from the nose gear slamming into the ground, maybe the suspension on it is a little too stiff, but again this is something I can't say I've ever encountered. I get slight nosewheel bounces (by slight I mean, barely noticeable), but maybe it's just down to flare timing. Either way, here's a pair of trackfiles, approaches are a little sloppier than I'd like and slower than I'd usually fly but the landings are pretty typical. Flew these in default DCS weather, ~40% internal fuel, 4 AAM (2 medium/2 light, since that's my usual).

21 landing 1.trk 21 landing 2.trk

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1 hour ago, CoBlue said:

Here 7% fuel I think. Those landings are deliberately a little hard. Sure you can do ok landings, but if a little hard the suspension shouldn't throw the 21 up in the air like a glove, also look at the absence of wheel damage.

 

I had alot of crashes, so I couldn't show everything that I wanted. Those are the only tracks I could get.

mig21 land 1 .trk 492.59 kB · 2 downloads mig21 land 3 b .trk 383.85 kB · 2 downloads mig21 land ok stol chute .trk 252.28 kB · 2 downloads

 

Well, that's more like 40% fuel I'd estimate. Certainly not 7%.

First landing had the sink rate way too high. 4m/s at time of touchdown. That's almost 800 feet per minute descent rate.
Second landing you kinda botched the flare. The saying 'butterfly with sore feet' is something to always keep in mind. It's also good practice to keep the chute deploy in your mind on landing in the same way you're ready to slam the throttle to the firewall on a carrier landing.
Third landing, you popped the chute too early. You were well over an aircraft height above the tarmac. Get nice and low, reduce sink to almost 0m/s, then pop it. You hit pavement at around 5m/s. 2-3m/s is what you should shoot for.

I've also noticed you aren't re-centering your gear handle to neutral. 

That all said, you really did not give yourself much room to play with on that approach. Give yourself an actual landing pattern. What @Skysurferposted makes a great reference. Start in the downwind leg at about 600kmh to allow gear deployment. Be down to about 450kmh when you start your base. I'd actually recommend keeping 450 at the start of the approach and work down to 350 by the time you reach the fence. Once you begin the flare, you will hemorrhage that airspeed and it provides you enough energy to soften the landing to 2m/s.

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Posted (edited)
2 hours ago, rossmum said:

going to F2 view right at touchdown probably didn't help with arresting the descent rate.

 

From the looks of it your problem is coming specifically from the nose gear slamming into the ground, maybe the suspension on it is a little too stiff, but again this is something I can't say I've ever encountered. I get slight nosewheel bounces (by slight I mean, barely noticeable), but maybe it's just down to flare timing

I was in the cockpit all the time, when I watched the track I went to F2, dunno why it came out like that...

 

Definitely something wrong with suspension IMO.

 

 

1 hour ago, MiG21bisFishbedL said:

Well, that's more like 40% fuel I'd estimate. Certainly not 7%.

First landing had the sink rate way too high. 4m/s at time of touchdown. That's almost 800 feet per minute descent rate.
Second landing you kinda botched the flare. The saying 'butterfly with sore feet' is something to always keep in mind. It's also good practice to keep the chute deploy in your mind on landing in the same way you're ready to slam the throttle to the firewall on a carrier landing.
Third landing, you popped the chute too early. You were well over an aircraft height above the tarmac. Get nice and low, reduce sink to almost 0m/s, then pop it. You hit pavement at around 5m/s. 2-3m/s is what you should shoot for.

I've also noticed you aren't re-centering your gear handle to neutral. 

That all said, you really did not give yourself much room to play with on that approach. Give yourself an actual landing pattern. What @Skysurferposted makes a great reference. Start in the downwind leg at about 600kmh to allow gear deployment. Be down to about 450kmh when you start your base. I'd actually recommend keeping 450 at the start of the approach and work down to 350 by the time you reach the fence. Once you begin the flare, you will hemorrhage that airspeed and it provides you enough energy to soften the landing to 2m/s.

It was between 4-10% fuel in ME as I tested different fuel-loads, no way 40%!, 3rd landing was deliberate chute-before-touch-down to check suspension. Reread my post again, as this was a quick suspension test, not a check-ride including perfect traffic-patterns etc.

 

It's what happening after a little "hard" landing that is disturbing, the "strange bounce", if you're doing perfect landings all the time you never going to notice it. You've got to be testpilots.

 

Re-watch my video above & this & tell me why you don't see any bounces???

 

Former FM during touch-down was spot on IMO, the 21 has beefy landing-gear, it was build for landings on unprepared strips & "hard" landings. Currently it behaves like a 737.

 

 

 


Edited by CoBlue

i7 8700k@4.7, 1080ti, DDR4 32GB, 2x SSD , HD 2TB, W10, ASUS 27", TrackIr5, TMWH, X-56, GProR.

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You came down like a sack of bricks, ripped the fuel tank off on at least 2 of the tracks.

These were not "a little hard." You should have blown tires on these (if that was modeled). Vertical speed nowhere close to the the video footage. Simulator pilots are a terrible judge of sink rates on touchdown.

 

You bounce because you bash the nose wheel. Just like when people complained about the 29. They bashed the nose wheel too. Stop bashing the nosewheel and you'll stop bouncing like that.

Watch your source videos. They don't bash the nosewheel. Watch for smoke from the nosewheel. You smack it right on.

You claim "not a single bounce." Yeah they did. You can't see it? It's generally less than 1/2 the height of the main wheels but they absolutely are bouncing. You can even hear the bounce in the audio.

Its the same thing all over again.. simulator pilots really have no frame of reference when it comes to landings. They post landings they think are "okay" or "a little hard," that in reality would be serious events possibly causing structural damage (in this case ripping a tank off it's mount).

 

Landing on the nosewheel is not acceptable.

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Posted (edited)

To help demonstrate just how hard the smack really was,

I changed the view of "mig21 land 1.trk" and moved the free camera to approximate the perspective seen in the timestamped youtube clip, "Mig-21 landing on a highway"

of course I can't replicate the telephoto effect which compresses the perception of distance, so I'm a little closer to the touchdown point than the videographer.

mig21 land 1 Youtube View .trk


Edited by randomTOTEN
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1 hour ago, CoBlue said:

It's what happening after a little "hard" landing that is disturbing, the "strange bounce", if you're doing perfect landings all the time you never going to notice it. You've got to be testpilots.

 

Re-watch my video above & this & tell me why you don't see any bounces???

 

Former FM during touch-down was spot on IMO, the 21 has beefy landing-gear, it was build for landings on unprepared strips & "hard" landings. Currently it behaves like a 737.

 

a) As noted, that wasn't just "a little hard". You came down with quite a thump. The ironic thing is that you probably would've been fine (since DCS doesn't model tyre bursts under excess pressure, as far as I can tell, only overspeed) if you'd held the nose off longer. The main gear can absorb quite a shock before it bounces, the nose gear not so much. And as also noted... the MiG-29 exhibits this same behaviour, but even less forgiving. I stopped playing kangaroo down the runway in the 29 when I realised I was flaring too little, too late.

 

b) There is an incredibly obvious nosewheel bounce...

 

c) The "former FM" (actually it was purely suspension modelling, the flight model itself hasn't changed) also caused your wheels to clip through the ground and grind the brake drums on the concrete while landing, and caused the aircraft to lean over so severely that the same thing would happen while steering on the ground, which in turn rendered differential braking ineffective.

 

At best, the nosewheel bounce may be too strong in that maybe it shouldn't spring the aircraft back into the air quite so hard - but I don't know, I haven't exactly tested a real 21 to destruction to say that with authority and don't know what the damping force on the suspension is. From a landing like you've uploaded, you're still looking at some fairly serious structural damage from a landing that hard, regardless if it bounces or not.

 

I hate to say it, but all I see going on here is bad landing habits catching up to people, just like when the "use AB to get out of a dangerous approach" avenue was finally fixed, and just like when the FM was fixed after the month and a half or so where the aircraft's stall behaviour broke and it was acting like it had fly-by-wire. Improve your landings and the problem will go away.

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