Su-25T vibrations on the ground and seemingly weak nose gear... - ED Forums
 


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Old 08-07-2018, 08:53 AM   #1
umkhunto
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Default Su-25T vibrations on the ground and seemingly weak nose gear...

I'm not sure whether this should here or in the DCS World 2.5 sub, so feel free to move it if you deem necessary.

Running on OB:

I'm curious whether other people have noticed the extreme amount of vibration while taxing in the Su-25T. Also, the nose wheel feels extremely fragile. (Maybe this is what's causing the vibration at taxi.)

I would say since about a week ago, maybe more, I've noticed the vibration and have not been able to land the 25T successfully, without losing the nose wheel, even when at 320km/h with about 2-3m/s rate of descent, especially if there's a cross wind. I've also lost the nose wheel under braking whilst taxing.
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Old 08-07-2018, 08:55 AM   #2
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320kph seems to high, at what weight are you landing? I normally pass the runway threshold at around 300kph and touch down around 275kph. Try this, no weapons, no gun ammo and only 40% fuel. Are you still breaking the landing gear on touchdown?
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Old 08-07-2018, 09:25 AM   #3
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Originally Posted by mvsgas View Post
320kph seems to high, at what weight are you landing? I normally pass the runway threshold at around 300kph and touch down around 275kph. Try this, no weapons, no gun ammo and only 40% fuel. Are you still breaking the landing gear on touchdown?
SU 25T landing .trk
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Old 08-07-2018, 09:39 AM   #4
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I'll modify my parameters and test again. Each of my recent landings was with about 40-50% fuel and winchester.
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Old 08-07-2018, 11:32 AM   #5
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umkhunto, check my thread of similar concern:
https://forums.eagle.ru/showthread.php?t=215409
Currently modeled nose wheel is very fragile so be extra careful and keep your rudder inputs minimal.
As for vibrations I see nothing wrong unless of course you already lost some wheel.
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Old 08-07-2018, 01:30 PM   #6
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Thanks, I'll have a look.
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Old 08-07-2018, 02:20 PM   #7
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I fly the 25T a lot.

#1 Landing speed is 250/280kmh. You're way over. Waaay over.

#2 You should land with the nose raised a few degrees, which is hard to do at that speed. The nose is for steering and supporting the front, not absorbing shock from landing. That's why the rear gear are several times larger than it is.

#3 The heavier you are and faster you're moving the more important it is you make a gentle and very controlled touchdown. You are coming down too fast for 320kmh and damaging the gear.

#4 There's a thing called friction. It causes heat. When you land at this much higher than safe speed and lock up the brakes they overheat and the tires blow or catch on fire. This is because you're going too fast. -edit High speeds are enough to blow tires all other considerations aside. The plane weighs 30,000lbs+ and you're traveling over 200mph. They're not racing tires.

#5 You don't use the brakes to stop on a Russian aircraft. That's what the drogue chute is for. But you have to slow down first or you'll rip the chute off when you deploy it.

#6 Crosswinds aggravate all of the above. Use the correct runway for the wind direction you have (read the weather data when the mission starts, it's not just decorative) and if necessary use a different airfield.

#7 You're not using flaps most likely, because 320kmh and full flaps makes the plane very floaty. I you are using flaps, you're probably tucking the nose in and collapsing the gear. See #2.

TLDR
The game is fine, the nose gear is fine, your landings suck. 300+ kmh is 'battle damage and can't lower flaps' kind of situation.

Proper landing: Full flaps, nose raised 5-8 degrees, 1-2ms sink rate, touchdown on main gear at whatever speed gives you that, usually 270ish let the plane stabilise several seconds, then pop the chute. Only brake at the very end IF necessary so you can taxi to parking.

TIP: When you land you should be able to hold the nose off the ground, apply full power and climb back up immediately. If you are cannot do that, you are landing too hard.
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Old 08-07-2018, 08:24 PM   #8
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Quote:
Originally Posted by zhukov032186 View Post
...the nose gear is fine, your landings suck...
Yes, but tell us what you really think.
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Old 08-07-2018, 10:01 PM   #9
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Another thing - If you're not using the chute, don't try to brake and turn at the same time - makes sense if you think about it - you throw all the weight on the front wheel then peel off the tire by turning it sideways - so pulse your brakes : Brake hard, release and correct track, brake hard, release and correct track.

This is a very low quality video, but it's landing the SU-25T at 19500kg.
Because it's so heavy, you'll see from the HUD I came in a bit low and fast, but if you look carefully at the status bar you can see that as I crossed the threshold I cut the engines and flared, and touched down at 260 km/h. There's a lot of runway left after stopping. I tried without using the chute, and at 19500kg that resulted in a stop much further down the runway :-) - but apart from pride (or a big crosswind), why not use the chute ?

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Old 08-08-2018, 07:55 AM   #10
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Quote:
Originally Posted by Weta43 View Post
Because it's so heavy, you'll see from the HUD I came in a bit low and fast, but if you look carefully at the status bar you can see that as I crossed the threshold I cut the engines and flared, and touched down at 260 km/h.
I see 280 @touchdown. And it's not extremely heavy if it's 30% fuel
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