Vikhrs in wind

So did anyone ever figure out how to fire the Vikhrs in high wind so that it will see the laser and track? I followed Vipers instruction and I still can't get it to work.

i just side-slip downwind until i have effective 0 lateral AS

it'd be good to know what the wind direction is. Usually at high wind (above 25m\s) Vikhrs often miss if you don' fire them parallel to the wind direction. If you fire in other way you must adjust plane nose to the wind course.

I could successfully launch them in such conditions, but luck has great impact here as well.

Wihrlwind (Vikhr) Gone with the Wind.

Please don't :poster_ban:me

i just side-slip downwind until i have effective 0 lateral AS

Good one! Never thought about that!

Good one! Never thought about that!

plank drivers never do

;)

plank drivers never do

 

 

 

 

;)

Got more time in the Shark than in that plank :). For now.

Plank :lol:

it'd be good to know what the wind direction is. Usually at high wind (above 25m\s) Vikhrs often miss if you don' fire them parallel to the wind direction. If you fire in other way you must adjust plane nose to the wind course.

 

I could successfully launch them in such conditions, but luck has great impact here as well.

You can use the PVI to determine wind direction & Speed. I don't know how it works, but you can.

Is for example the Hellfire also so dependent on wind direction?

You can use the PVI to determine wind direction & Speed. I don't know how it works, but you can.

I just noticed he asked about Ka-50, I thought Su-25T

My sentence was related to the Frog :)

Is for example the Hellfire also so dependent on wind direction?

No, it is not. It doesn't have to be in the beam tunnel - similar to Kh-25ML...

Vikhrs problems in the wind aren't caused by its guidance method but by its steering method. It only has one steering axis (up/down) which combined with spiral flight path provides steering to all directions but as a result it's not very responsive and it can turn in only one direction at a time. If it needs to make a sharp correction and the missile isn't in a proper bank it can't turn until it has rolled to proper angle. Swedish Bolide MANPADS uses similar laser beam riding guidance as Vikhr but the missile has two axis steering like normal missiles and has no problems with high winds or fast lateral movement of targets.

Can you specify what gate size Swedish missiles' launcher vehicle creates? For Vikhr its launcher makes ~7 meters diameter beam gate. It is not too big when we take in consideration rocket is being launched from the tube first, then it catches beam ahead of the plane often flying quite fast... and having cross wind :P

The basic problem is not the beam size in itself but Vikhrs inability to stabilize it's trajectory in the center of it except in optimal conditions, ie. no crosswind and static target and launch platform. With crosswind or decent LOS rate the missile can't stabilize itself to the center of the beam but keeps spiraling slightly all the way to the target. When crosswind or LOS rate gets high enough the spiral gets so wide that the missile flies out of the beam. Missile with 2-axis steering will stabilize itself to the center even with crosswind or LOS rate as long as the disturbance doesn't change but stays static. With 2-axis steering the missile would follow a narrow beam easily as long as the disturbances aren't too rapid regardless of their strength. With Vikhr it's not only the rapidness of the disturbance but also it's strength that's a problem.

Technically it should be possible to build a missile with 1-axis steering that can fly almost like a 2-axis missile but it would probably be simpler to use 2-axis in the first place.

I tried with 180km/h crosswind and the vikhrs fly slowly at 250km/h directly to the ground. then i've got rotor intersections. :D

Then i tried with 85km/h crosswind, and the vikhr misses the target by 50m. (4km far)

tried with laser designating or laser painting (20secs). same results.

didn't tried with the KH-25.

yeah, 180 km/hr is hurricane-force wind, you're not gonna get any hits in that. 85 km/hr is gale-force wind. in either wind condition, helis should probably not be flying, much less fighting.

Never mind flying, they start advising against driving with wind speeds like that around here.

The basic problem is not the beam size in itself but Vikhrs inability to stabilize it's trajectory in the center of it except in optimal conditions, ie. no crosswind and static target and launch platform. With crosswind or decent LOS rate the missile can't stabilize itself to the center of the beam but keeps spiraling slightly all the way to the target. When crosswind or LOS rate gets high enough the spiral gets so wide that the missile flies out of the beam. Missile with 2-axis steering will stabilize itself to the center even with crosswind or LOS rate as long as the disturbance doesn't change but stays static. With 2-axis steering the missile would follow a narrow beam easily as long as the disturbances aren't too rapid regardless of their strength. With Vikhr it's not only the rapidness of the disturbance but also it's strength that's a problem.

 

Technically it should be possible to build a missile with 1-axis steering that can fly almost like a 2-axis missile but it would probably be simpler to use 2-axis in the first place.

Well, having ie. 20 meters wide makes larger area for missiles' adjustments. In such way missile will not go out of the beam and continue flying to the center of it.

You can use the PVI to determine wind direction & Speed. I don't know how it works, but you can.

I thought I read somewhere that this is set at mission creation time? I could be completely wrong but I'm pretty sure it's not a real time read out. (i'm away from my flight computer for 3 months so bare with me :D)

The flight computer is able to calculate wind speed and direction by combining GNSS (satellite) velocity and airdata measurements.

Manual page 6-65: On the PVI

“delta/V” (Wind direction/speed) button. Indication of the wind direction and wind speed. Used meteo wind direction (from) that differs on the 180° degrees from navigation wind (to). [RALT + D]

However it does not. Bug or a feature?

Hmm, I had it only looked up from the manual, not tried in flight yet. I'll see if I can get some wind data on the PVI.

On the topic of dealing with crosswind: the Vikhr has a tendency to weathercock into the wind directly after leaving the launch tube. This is due to the big vanes on the backside of the missile body. Before picking up speed the missile has no aerodynamic steering effectiveness. But the wind creates a turning moment pointing the missile's nose into the wind slightly. Only a moment later the missile can start steering to the laser cone center. But it might well have flown out by that time.

From a hover you can get much better results by pointing the nose a few degrees with the wind. How much is a matter of experience though.

In any case, the crosswind component is not taken into account in the aiming cue on the HUD. So I verify cross wind direction by the smoke stacks and point the Vikhr aming cue just outside the target ring into the direction where the wind is going ("with" the wind). That way, the weathercocking effect puts the missile in to the laser cone. You may have to select the manual launch override to get a missile off the rail.

Hmm, I had it only looked up from the manual, not tried in flight yet. I'll see if I can get some wind data on the PVI.

You can but it does not change according to location, altitude etc. When you land at a different airport, the ATC will give you different wind values than what you have on the PVI. Also the values vary at different altitudes, PVI does not.

Are the nose vanes instrumented as they are the only sensors on Ka-50 capable of providing airspeed vector required for calculating wind. Besides, GNSS is limited to ABRIS only but PVI does have doppler radar to make it up.

Ok, then perhaps it only uses the data set in the ABRIS meteo page.

I don't know which part of the avionics is connected to the nose boom either. It is an interesting question. Anyone?

I was merely saying it is possible to calculate wind from the available sensors. Although there is a problem with airdata on helis once they fly so slow that the sensors are inside the rotor downwash. Then you have no reliable free stream data anymore. Above about 50 km/h though, it should work fine. Perhaps the wind data in the PVI are only updated when flying faster than a certain speed?