Possibility of Mig 21 Landing and aerobraking as seen IRL videos.

Out of all the DCS jets, the Mig 21 seems to be the hardest perform an aerobraking flair after the main gear touches. At present, soon as the main gear touches, it just forcefully slams the front gear even when coming at low VVS.

Aerobraking is doable in the F-5, it seems to be the 3rd hardest to aerobrake. 2nd being the F-14B. I've seen Iranian F-14 with full flaps and spoilers still doing some lasting aerobrakes

The Mig 21 main gear feels gummy and feels like its got too much friction and wobble modeled in.

IRL we can see vids of Mig 21 landing in load (wing drop tanks) and still doing aerobraking. Mostly vids of Mig 21 LanceR and Indian Mig 21 Bisons.

I would agree that the gear is feeling odd at the moment. But even though it’s challenging to aerobrake, as of late it seems it’s actually easier than in previous builds. It seems to respond best to aerobraking if it is trimmed to being hands off at the round-out. I have yet to experiment much, but being slightly nose-up trim on short approach could be helpful.

I would agree that the gear is feeling odd at the moment. But even though it’s challenging to aerobrake, as of late it seems it’s actually easier than in previous builds. It seems to respond best to aerobraking if it is trimmed to being hands off at the round-out. I have yet to experiment much, but being slightly nose-up trim on short approach could be helpful.

I was able to aerobrake at least on seldom times before the 2020 updates. But now, I see even more erratic landing gear behavior. Even if the sink rate is low and you touch the main gear, it just forcefully slams down with a bit of wobbling sideways. Then down the runway, it wobbles all the way bobbing up and down, making strange mechanical sounds as if we belly landed.

I've seen at airshows where Romanian Mig 21 even with wing tanks still managing to do a smooth aerobrake landing. Its doable at least in the F-5 and to some extend the F-14 as well. But, the Mig 21 is the hardest.

At current, the main gear feels very "gummy"...

DCS Mig 21 ranks number 1 being the hardest plane to ever aerobrake. Landing physics need some tuning in the module.

I touch down at about 50cm/s vertical rate with 25% aft stick and immediately about 75% aft stick is required to halt the sudden torque trying to pitch the airplane down and to fly at the same attitude as before touchdown.

The issue is perahps most scientifically examined during takeoff. With 25% fuel, landing config, and the pitch axis limited to 40% deflection (axis tune) I can fly at ~125 knots with 83% (F2) RPM.

No way in heck can I rotate the same airplane to the same flight attitude while rolling as I can while flying. In order to pull the nose up in the air I have to be doing ~150 knots.

What this suggests is some kind of nose down torque while rolling that isn't present while not rolling. This is either wheel drag akin to braking or some kind of canned part of the FM when on the ground.

I really don't know why the idea of a touch and go at constant attitude isn't possible like so many other airplanes for a realistic reason.

The wheel drag may be a good point. Yesterday I was flying, and I had some moments while taxiing where the brakes felt like they were applied. It actually needed higher thrust than usual to start and stay moving. But then it mysteriously went back to normal. It almost seemed like a possible bug.

Schmal has been able to do a touch-and-go at constant attitude. I haven't tried yet, might give it a go later. I think the main problems with ground handling have all come from the suspension, though, which is actively being tweaked.

IORC MiG-21Bis had a weak brakes. I recall that in Finnish pilot interview said that they replaced the wheels to bigger ones as they needed to get larger brakes to it so they could stop under 600 m road with chute.

Don't have time to listen it again but something to check out was it Bis or some older version as I recall Finland got MF as well before Bis.

If that is true or so, then Bis in DCS shouldn't nose down because wheels slowing down on touchdown.

Second and third gen 21s had substantially larger wheels than the first gens. He would've been talking about the switch from F-13 to Bis.

Pay attention to the binding of the cockpit lantern. That's how I would like to hid it. Previously, it was more real. Now there is no sense of reality) The sealant was removed for some reason.

I think that the pitch down moment is simply too big and very hard to counter. The aircraft can be aero-braked quite well, but after landing on the MLG it just smaches the nose down even if you do it very very gently. I've watched many Mig-21 landing videos and talked to pilots, after gently touching on the main landing gear the aircraft should be quite stable in pitch and aerobraked easily. There was some tendency to lower the nose, but it was before touchdown, which needed to be compensated by aft stick and landing would be done with stick nearly fully back and this is not the case of our 21. I hope it gets improved in the future.

I think that the pitch down moment is simply too big and very hard to counter. The aircraft can be aero-braked quite well, but after landing on the MLG it just smaches the nose down even if you do it very very gently. I've watched many Mig-21 landing videos and talked to pilots, after gently touching on the main landing gear the aircraft should be quite stable in pitch and aerobraked easily. There was some tendency to lower the nose, but it was before touchdown, which needed to be compensated by aft stick and landing would be done with stick nearly fully back and this is not the case of our 21. I hope it gets improved in the future.

So far...out of all DCS fighters, this is the only plane that is hardest to land on an aerobrake format. And I have seen on clear airshow videos Mig 21 lands with load on, with wing tanks and still aerobrake good. I can even aerobrake the F-5 pretty good...

The USN F-18 hornet is also almost impossible to aerobrake with FULL flaps on landbased runways. Sometimes the F-14 as well...you can see the Iranian F-14 land in aerobrake fashion.

So far...out of all DCS fighters, this is the only plane that is hardest to land on an aerobrake format. And I have seen on clear airshow videos Mig 21 lands with load on, with wing tanks and still aerobrake good. I can even aerobrake the F-5 pretty good...

 

 

 

The USN F-18 hornet is also almost impossible to aerobrake with FULL flaps on landbased runways. Sometimes the F-14 as well...you can see the Iranian F-14 land in aerobrake fashion.

In my opinion you can absolutely aerobrake the 21, just dont slam it like a twat and keep holding and pulling the stick upon touchdown. I'll make a video later on to demonstrate.

What I don't understand is you can fly forever 1cm off the ground in a steady state condition but the second you make the slightest contact (1 kgf) the stabilizer angle required for the same attitude increases dramatically. What is the explanation for that?

I can aerobrake all aircraft in DCS world, but Mig-21BIS is the hardest. If you do not touch down absolutely gently and do not counter that pitch down moment when MLG touches/kisses the runway you will hit the runway with fron gear. The RL approach works, but you need to level out at less than 1 meter above the runway and be extremely smooth on touch down with power on (of course not lowering below SPS) and catch the moment of touch down at the same time smoothly decreasing power.

A Frederf said, I also do not understand what creates that strong pitch down moment after the MLG touches the ground, I have not seen in it in any video. Mig-21BIS can definitely be landed on MLG and aerobraked, however I think it is way harder than in real life. I can do it maybe 7-8/10 times after hundreds of landings.

In my opinion you can absolutely aerobrake the 21, just dont slam it like a twat and keep holding and pulling the stick upon touchdown. I'll make a video later on to demonstrate.

Cheap insults aside...:noexpression:

I did manage to aerobrake the Mig 21....SOMETIMES, at a certain specific sink rate and angle. Demonstration is not necessary. I know it can.

What I am trying to say is that, it is the HARDEST of all DCS planes to aerobrake, I mostly manage it via fluke. Sometimes even possible with light load at a specific angle. Still, it is hard.

I just made a short video of Aerobrake landing of Mig-21BIS, even there you can see that I touch absolutely gently from a height of less than 1 meter I still have to work the elevator and counter the big pitch down moment and then immediately neutralize elevator not to fly away from the runway, it is really very difficult and requires a lot of practice. I think that the plane should be much more stable in pitch after such touchdown.

That's really the question. It's possible to hold the airplane in the two-point attitude while in contact with the runway but the different in required aft stick position is not explained.

Height

1m: 27% aft stick

1cm: 27% aft stick

1 N2 molecule diameter: 27% aft stick

1 wavelength of ultraviolet light: 27% aft stick

contact: 77% aft stick

I'm talking same speed, same attitude throughout so the lift is 100% (or at least 99%) of the weight of the airplane. E.g. the weight on wheels is essentially zero.

I think that the plane should be much more stable in pitch after such touchdown.

Can you elaborate why do you think so, with numbers? What's the amount of counter-rotating moment of force on the wheels for example?

Can you elaborate why do you think so, with numbers? What's the amount of counter-rotating moment of force on the wheels for example?

No I do not have numbers for this, I doubt any graphs or numbers for this exist. Frederf has given you numbers which show there is a problem in modeling, making the landing unnecessary hard.

I have several technical manuals for different versions of Mig-21 and I also have a special manual with the methodology of pilots' training in our airforce for aircraft Mig-21F-13 and Mig-21UM, where the process of landing is described in a very detailed manner direct translation from the Mig-21UM manual (this is the same description as in F-13 manual):

The plane has to be levelled out at 1 meter above runway. Corresponding to the sink rate of the plane pull the control stick back at first smoothly and later more energetic, because 1.5 - 2 seconds before touch down the plane has a tendency to lower its nose (NOTE: before touchdown) Touchdown occurs at a speed of 270 km/h with normal landing weight, practically with the stick completely pulled back. After touchdown put the throttle to IDLE and release the chute. After putting down the nose gear, retract flaps and begin to brake.

Our Mig-21BIS does not behave like this, you cannot land with stick pulled back, because the plane is unstable and it will lift its nose and even lift from runway at very low speeds. As Frederf said you need to pull the stick to 27% before landing to obtain correct attitude after touchdown it suddenly needs 77% or it will smash the nose down. The transition is sudden and therefore hard to counter.

I am also attaching the picture of the manual I use as a reference.You might argue that it is not for BIS, but UM should generally behave in a very similar manner.

The procedure described above (same for the bis manual as UM) doesn't say that the nose will always tend to fall off on all landings but describes instead what will happen when the specific procedure in the manual is used.

The manual describes leveling off at 1m and then throttling back to the SPS gate and increasing stick to counter the descent until the aft stick is practically maximum and landing is unavoidable. It's not entirely clear why the nose has an intensive down moment 1.5-2s before landing. I think it's simply the stalling of the wings (before the tailplane) due to low airspeed and less likely some kind of aerodynamic ground effect favoring the tailplane over the wings. I'm guessing a faster landing (e.g. 300km/h) not using this 1m level-off-and-idle technique would not experience the same nose moment.

If it is some kind of aerodynamic near-ground interaction (instead of a stall behavior) then that would suggest that the moment would smoothly increase at height <1m and not suddenly occur on ground contact.

The next paragraph says "after touchdown, hold the control stick in the same position as at the moment of touchdown... as soon as the aircraft starts rolling steadily, shift throttle to idle, smoothly lower the nosewheel..." That suggests that upon touchdown a constant stick input retains the nose wheel out of contact of the runway at least for enough time to accomplish the other tasks described between touchdown and lowering the nosewheel. Plus it mentions smoothly.

some kind of aerodynamic ground effect favoring the tailplane over the wings

In most aircraft with non-elevated(not like in MiG-15) position of tailplane is affected by wing wash and even vortices if any present. Usually the wash goes back - down. When ground approaches, it begins to redirect the wash direct-back or even back-up instead of back-down dramatically affecting the AOA of the tailplane and requiring very large amounts of stick travel to counter. But if it does not occur untill the touchdown then it's not this but either scripted switch of some mode of the modeling, or wheels behave like they have brakes all the way on.

My case in aerobraking is interesting - the nosewheel touches the ground but after it touches I'm again able to put it back in the air and aerobrake with good efficiency. So my guess is amount of force wheels need to start rotating is exaggerated.

My case in aerobraking is interesting - the nosewheel touches the ground but after it touches I'm again able to put it back in the air and aerobrake with good efficiency. So my guess is amount of force wheels need to start rotating is exaggerated.

Yes, this is what is happening, it might have to do something with suspension/wheels/tyres drag modeling.

Yes, this is what is happening, it might have to do something with suspension/wheels/tyres drag modeling.

Yeah, when all the wheel touches and THEN you try and do an aerobrake. Its much easier.

But while landing, when the main gear touches for now, it just feels very "gummy" and this automatically forcefully forces the nose down movement. It is SOMETIMES doable, when you get THAT RIGHT angle to touch the main wheels along with the sink rate. Still, it is very hard. You can see in airshow videos the Mig 21 landing even with load like wing tanks etc...

The other jets are OK...just needs some practice, minus the Hornet on full flaps. Try landing the Hornet on full flaps on land bases. I SOMETIMES see on airshows where it does the aerobrake. Mainly other nations users.

So yeah, then ground handling or landing physics need to be remodeled again.

Out of all the DCS jets, the Mig 21 seems to be the hardest perform an aerobraking flair after the main gear touches. At present, soon as the main gear touches, it just forcefully slams the front gear even when coming at low VVS.

 

Aerobraking is doable in the F-5, it seems to be the 3rd hardest to aerobrake. 2nd being the F-14B. I've seen Iranian F-14 with full flaps and spoilers still doing some lasting aerobrakes

 

The Mig 21 main gear feels gummy and feels like its got too much friction and wobble modeled in.

 

IRL we can see vids of Mig 21 landing in load (wing drop tanks) and still doing aerobraking. Mostly vids of Mig 21 LanceR and Indian Mig 21 Bisons.

You can aero-brake just about any aircraft with tricycle landing gear as long as the elevators have enough control effect. Doesn't matter what brand of plane it is.

Just hold the nose up after touchdown and there ya go. Some planes will plunk the nose gear down hard after main gear touchdown, so you have to 'grab' it with back-stick and hang onto it--ideally without dragging the exhaust nozzles on the runway, which really miffs the maintenance crew :)

I'm lazy so I just use the drag chute.

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