ASP Gunsight Discussion

[MBot]

I would like to initiate a general discussion about the ASP gunsight. Has anyone been able to use it succesfully for deflection shooting? To me it seems that it doesn't compute enough lead. Basically I regard the gunsight to be completely useless in practice.

 

Also up to now I was under the impression that the sight could not use radar ranging information and is fixed to 300m, a fact I found extremely surprising cosidering that radar gunsights were mastered 20 years prior the MiG-21bis. Revisiting the manual, I stumbeled upon this tibit on page 132:

 

When in automatic mode, the ASP will draw the pipper according to either Sapphire data (if the airborne/ground target is radar-locked), or pre-set distance, target size and angular corrections that enable optimal use of ASP sight.

[Fishbreath]

The lead computation worked fine for me just now, both in manual mode (with manual ranging/bracketing of the target, like the P-51 sight) and automatic mode (at 300m). Remember, for wingspan, in automatic mode, you use the scale printed on the knob, and in manual mode, you use the scale in the window.

 

I've never been able to get radar ranging information to the gunsight, though. If the sight can indeed do that, awesome—I'd been under the impression that it couldn't, too.

[MBot]

Here I have been stably tracking the target. The tracers don't even touch the pipper.

[Fishbreath]

Huh. That's odd. I'll try on a Phantom later tonight.

[ttaylor0024]

Here I have been stably tracking the target. The tracers don't even touch the pipper.

 

Set your pipper to the correct wingspan (12m for the F-4) and you should be ok. I haven't ran into any issues with it.

 

Edited January 19, 2015 by ttaylor0024

[IvanK]

In the animated graphic above why is the Gyro pipper still on the sight vertical axis in a turn ? Its seems to be computing lead in the vertical plane but not in the plane of motion. In a left turn the sight should be displaced to the right of the sight vertical axis. I see this same erroneous (imo) gyro sight behaviour in the MIG21 as well.

[ttaylor0024]

In the animated graphic above why is the Gyro pipper still on the sight vertical axis in a turn ? Its seems to be computing lead in the vertical plane but not in the plane of motion. In a left turn the sight should be displaced to the right of the sight vertical axis. I see this same erroneous (imo) gyro sight behaviour in the MIG21 as well.

 

That's not true. The reason you compute lead in the first place is for range and forces effecting the aircraft in flight. Since range is 300m, all we compute is the offset for the G loading. In a left turn such as the one pictured above, you are in a coordinated turn, and as such the bullet will fly through the vertically through the gunfight still because the centripetal force and horizontal component of lift cancel out. In this case, the vertical plane IS the plane of motion.

 

Notice in this graphic how in a coordinated, level turn the vertical lift component cancels out the weight, and the horizontal lift vector cancels out the centripetal force.

 

Edited January 20, 2015 by ttaylor0024

[Djent33]

It may be a reasonable to see the gyros not being precise, or as radar Lock at distance could have + - tolerance which could be in meters rather than centimetres.

[ttaylor0024]

It may be a reasonable to see the gyros not being precise, or as radar Lock at distance could have + - tolerance which could be in meters rather than centimetres.

 

The gunsight in the MiG-21 does not take ranging information from the radar, but rather is locked in at 300m

[streakeagle]

From my testing, the gunsight does not take range information in either manual or automatic modes. Adjust the range manually and the pipper still doesn't move up or down to reflect the bullet drop caused by range. Since manual range is always locked at whatever range you select, what would be the point of an "auto" mode if it didn't use range info from the radar?

 

I am going to guess that the MiG-21bis gunsight made decades later would at least be equal to the USA's F-86 gunsight that the USSR surely captured and reverse engineered? Based on my experience in this sim, I pretty much ignore the pipper and use the fixed reference grid with the tracers to correct.

 

I can use the P-51D and F-86F gunsights without issue (notwithstanding the heavy gun smoke blocking the view on the F-86 since the last major patch). So, either the MiG-21bis gunsight sucks in comparison to WW2 and Korean War tech or it has not been implemented correctly by Leatherneck. Leatherneck's main programmer is a MiG-21 pilot, so I wouldn't expect the gunsight to be implemented incorrectly. So that leaves the lack of response to range input to be either an unintentional bug or an intended reflection of reality.

[IvanK]

That's not true. The reason you compute lead in the first place is for range and forces effecting the aircraft in flight. Since range is 300m, all we compute is the offset for the G loading. In a left turn such as the one pictured above, you are in a coordinated turn, and as such the bullet will fly through the vertically through the gunfight still because the centripetal force and horizontal component of lift cancel out. In this case, the vertical plane IS the plane of motion.

 

Notice in this graphic how in a coordinated, level turn the vertical lift component cancels out the weight, and the horizontal lift vector cancels out the centripetal force.

 

 

Actually you are wrong :) the reticle will ONLY sit on the vertical axis if the Vertical axis and the plane of motion are aligned (like in a wings level loop). In just about every other event the reticle will be displaced from the gunsight centreline ... The jpg below was taken many moons ago ( I was a 21 year old flying Mirage IIIO's against the new Wunder machine the F14). This is a guns tracking solution in a right hand turn with a basic LCOS sight. As you can see the lead solution comprises both elevation and azimuth the pipper displaced from gunsight centreline this was fairly low G around 3G

 

In this next shot (again one of mine) in a left hand turn versus F16. In this case G was around 7.5G the pipper is again displaced from the gunsight centreline but to a much lesser degree as the fighters plane of motion and plane of symmetry get closer as G increases.

 

 

And finally another against an F5E in a left turn taken around 4G

 

And here is the whole LCOS lead problem explained this from an F4 manual

 

The reason you need lead is for ballistics and LEAD FOR TARGET MOTION during the bullet time of flight. The actual amount of lead is quite a complex business as it accounts for Lead for target motion, Gravity drop, Trajectory shift (velocity jump), Angle of gunfire, Fuselage flexure,and parralax :) ... its not just the basic turning forces on your aeroplane :)

 

Here is a description of pipper behaviour from an old USAF Fighter Weapons Newsletter article on sight handling:

 

In summary the LCOS pipper will only sit on the gunsight centreline if the Shooters plane of motion and plane of symmetry are the same.

go and have a play with the K14 sight in the P51 and the Sabre sight and you will see ... they are working as they should :)

Edited January 20, 2015 by IvanK

[ttaylor0024]

Actually you are wrong :))

 

I realized about an hour after I wrote that when thinking about it that I don't think I had all the info. Good info!

[IvanK]

your welcome

[MBot]

Set your pipper to the correct wingspan (12m for the F-4) and you should be ok. I haven't ran into any issues with it.

 

I set the wingspan to 11.5m on the outer scale, which shuold be close enough. But regardless of the set wingspan, the trajectory of the tracers should be crossing the pipper at some point. This is not the case here.

[MBot]

In the animated graphic above why is the Gyro pipper still on the sight vertical axis in a turn ? Its seems to be computing lead in the vertical plane but not in the plane of motion. In a left turn the sight should be displaced to the right of the sight vertical axis. I see this same erroneous (imo) gyro sight behaviour in the MIG21 as well.

 

To answer this question, you have to set the ASP mode switch at the lower left of the gunsight (CU19) to gyro (down) position. In the missile position (up) the pipper will only move in the vertical axis.

[CoBlue]

Based on my experience in this sim, I pretty much ignore the pipper and use the fixed reference grid with the tracers to correct.

I can use the P-51D and F-86F gunsights without issue . So, either the MiG-21bis gunsight sucks in comparison to WW2 and Korean War tech or it has not been implemented correctly by Leatherneck. Leatherneck's main programmer is a MiG-21 pilot, so I wouldn't expect the gunsight to be implemented incorrectly. So that leaves the lack of response to range input to be either an unintentional bug or an intended reflection of reality.

 

This is my experience also & I really would want someone to answer this:

Is the piper working correctly & why does it differ so much from F-86 & P-51?

Edit/ Ok I have done some tests & the piper is only effective <300m which is really close, see pictures below taken from 800m, 500m, 300m...in other words you have to be really close;).

Edited January 20, 2015 by CoBlue

[Fishbreath]

I've never had any issues using it to shoot at bombers, at least. I find that it takes long enough for the sight to settle that I can only rarely line up a shot on a fighter steady enough for the sight to be accurate.

[IvanK]

Thanks MBOT I will give that a try

[MBot]

Yesterday we did some air-air practice in my squad, including various opportunities to use the gunsight. Again it showed that putting the pipper on target results in missed shots.

 

Consider this. When putting the sight in manual mode, you can set the range to a value between 400m and 2000m. Now if you set the range to a ridiculous large range such as 2000m, when pulling just a little Gs the pipper should make huge movements off the gun bore line (since time of flight for the shells to such a distance is very long). This is not the case. Even at if you set the ASP to 2000m and pull, the pipper only makes relatively minor movements.

Edited January 23, 2015 by MBot
typo

[ttaylor0024]

Yesterday we did some air-air practice in my squad, including various opportunities to use the gunsight. Again it showed that putting the pipper on target results in missed shots.

 

Consider this. When putting the sight in manual mode, you can set the range to a value between 400m and 2000m. Now if you set the range to a ridiculous large range such as 2000m, when pulling just a little Gs the pipper should make huge movements off the gun bore line (since time of flight for the shells to such a distance is very long). This is not the case. Even at if you set the ASP to 2000m and pull, the pipper only makes relatively minor movements.

 

When I set wingspan in the inner scale in auto mode it works perfectly. Not sure that's the correct way, however I get the results I need.

[MBot]

When I set wingspan in the inner scale in auto mode it works perfectly. Not sure that's the correct way, however I get the results I need.

 

According to the manual, for the auto mode wingspan should be set using the outer scale.

 

Regardless, wingspan is irrelevant to the fact that in my first screenshot in the thread the tracers go below the pipper. Wingspan is only needed to determine distance to target. The tracers should meet the pipper at 300m, with any wingspan setting. This is clearly not the case here.

[ttaylor0024]

According to the manual, for the auto mode wingspan should be set using the outer scale.

 

Regardless, wingspan is irrelevant to the fact that in my first screenshot in the thread the tracers go below the pipper. Wingspan is only needed to determine distance to target. The tracers should meet the pipper at 300m, with any wingspan setting. This is clearly not the case here.

 

It looks like I keep my reticle in MSL mode instead If gyro, so the inner scale works in that situation according to the RL manual. I don't know why the other way isn't working, but I'd suggest staying in MSL mode, as it's very accurate for me.

[Andrei]

I would also like to bring the topic of A2G mode of the ASP where it seemingly receives ranging information to the target even with radar off which makes A2G employment way too precise compared to the real thing was. As far as I know IRL ASP-PFD-21 recieved no information from neither radar, nor radar altimeter.

[Stealth_HR]

This has been confirmed in another thread as something the developers willfully included in order to fit the aircraft better into the DCS experience.

[Andrei]

This has been confirmed in another thread as something the developers willfully included in order to fit the aircraft better into the DCS experience.

 

Yes, however this doesn't make too much sense with the DCS: xxx title. It's not a bug then but a rather severe (in my opinion) simplification. For several DCS products there is an "arcade" mode where this approach does indeed make perfect sense. But not in the proper simulation.

 

Wonder how does this actually "fit the aircraft better into the DCS experience"? Just to be explicit: I am under no circumstances criticizing you or your explanation; rather the LNS approach regarding this particular issue.