Yet Another BK90 Accuracy Question

[tn_prvteye]

Ok, is there any way to consistently get the BK90 on target? I've set up a training mission with some APC/Tanks and set that as a Waypoint...right in the middle of the cluster.

 

I've made sure the TERRNAV is 5-0, I've also tried a manual NAV fix using a landmark. I've adjusted the Target Point using the Radar. I've made sure I take off right down the middle of the Runway. I've set the QFE at the Target point using the Kneeboard reading. Everything about the approach is by the book.

 

But my waypoints always seem to be off by just enough to barely miss the targets. The only thing I haven't tried is manually adjusting for Wind in the CK37 (there is wind in the mission). I thought the Doppler Radar would compensate for wind.

 

Also, I've read that you must be in NAV mastermode for three minutes before take-off...is that accurate? I'm not sure I'm waiting that long.

 

Anything else I'm missing? Closing one eye and sticking out my tongue? Sacrificing a chicken?

 

 

[Skysurfer]

I usually switch on NAV when lining up on the runway, visual fix is good but no need to adjust the thing with the radar. Even without a visual fix, keeping the system at 5.0 is usually good enough to get them all mostly on target. BK90's just arent precesion guided munitions by any means and if there is noticeable wind the accuracy might degrade even more.

[tn_prvteye]

Thanks, I guess I'll just need to live with it. If that's realistic, I'll stop beating my head against the desk trying to hit the target. :D

[MYSE1234]

If you got TerNav working and sending fixes to the nav system, doing a radar fix is just going to make it less accurate. If you get a 5 from the system, there's no need to make a fix as the fixes from TerNav are dead accurate.

[tn_prvteye]

Good to know...AND less work for me!

[Machalot]

I wouldn't expect wind to significantly affect the accuracy of an inertially guided weapon. The IMU should detect the disturbance in the motion of the bomb caused by wind and the guidance system should steer to correct it. There's a limit to how much corrective maneuvering it can do, of course, but unless you're shooting at crossrange targets you're probably not hitting that limit.

[Skysurfer]

Problem is not the glide vehicle itself but the bomblets being blown away by the wind. This ain't a CBU97 or 105.

[Eldur]

Also, I've read that you must be in NAV mastermode for three minutes before take-off...

 

IIRC it was the other way round, you mustn't be in NAV all the way prior to takeoff. That's why I and others switch to it literally on entering the runway or when beginning the takeoff roll.

[ghostdog688]

 

IIRC it was the other way round, you mustn't be in NAV all the way prior to takeoff. That's why I and others switch to it literally on entering the runway or when beginning the takeoff roll.

 

Concur, IIRC the manual seems to state you taxi in BER, then once straightened up on the runway, flip to NAV and hit the “reference button”. This makes the fine tune alignment on the compass, one of the elements you need for an accurate INS fix. TERNAV helps, but gets bad if you are flying over flat land/sea, as it stops getting enough meaningful data to detect drift.

 

Don’t forget also, you can input wind speed and direction if it’s known. It will help the BK90s compensate a little for the wind drift.

 

Also ensure the QFE is set for the target area. The BK90 takes its dispersion altitude from good initial data. You have to tell it the correct height it started at ;)

 

But yeah, expect a wider dispersion during higher wind days. All you can do is use more BK90s to compensate (ie increase the concentration of bomblets), change the attack direction to counter the wind a little (avoid dropping perpendicular to the wind to reduce its effect on the bomblets), or use a different weapon.

 

There’s a reason the Met Office is consulted by pilots during briefing and not just on the tarmac :)

 

 

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