[FIX UNDERWAY] ASP AA gun pipper IAS dependence

[Szit]

In close range air to air combat i have been using the pipper to hit a non maneuvering/low-g maneuvering target. I found it to be really weird that even though i am placing the pipper right on the target at a range to the target that corresponds to the mode i am in (automatic or manual mode) my bullets are way off target.

So i did some testing shown in the following figure:

 

In Figure a and c the aircraft is in a level flight at IAS =1000 km/h (a) and IAS = 500 km/h ©. In Figure b and d the aircraft is in a stable turn at IAS corresponding to a and c. In all figures the IAS (top), g load (middle), AOA (bottom) gauges are displayed. The track where i took the screenshots from can be found in the attachements.

 

ASP settings

Gun / Missile-Rockets

Shooting / Bombardment

Auto / Manual

Missile / Gyro

Wingspan set to 17m

 

Level flight

At 1000 km/h and almost 0 AOA the trail of bullets are below the pipper and the position of bullets shortly after exiting the gun with respect to the fixed net (called Boresight in the figures) is below the 1. cross (see Figure b).

When decreasing the IAS to 500 km/h the situation changes. Now the piper is below the trail of bullets and the Boresight is at the position of the 1. cross.

 

Turn flight

When turning the effect becomes more visible. In Figure b at 1000 km/h you can see that the bullet trail is only slightly above the pipper. But in Figure d at 500 km/h the bullet trail is significantly above the pipper.

 

This leads to a situation where you dont hit the target when using the pipper for aiming (especially at low IAS).

This dependency of the Mig21bis pipper on IAS is not present in the P51 (gyro mode) and F86F (gyro mode).

 

 

PS:

Using the Manual mode instead of Auto shows the same behaviour.

Mig21bis_gunsight_test.trk

Edited March 12, 2015 by Cobra847

[Szit]

Still present in 1.2.11.33866

[Dolphin887]

Noted.

[streakeagle]

I have done some extensive testing/experimentation with the sight in both manual and automatic modes. As far as I can tell, the gyro compensated pipper never receives range input. If you go into manual and move the range out and than back in, the pipper should drop at long range and come back towards the center at short range. It does not do this. Likewise, in auto with a radar lock, I see no evidence that the motion of the pipper is ever affected by the range to the target.

 

Maybe I am crazy for thinking this, but the purpose of a gyro compensated gunsight is largely defeated if it is locked to one range setting?

 

I understand the early MiG-21 gunsights were ineffective under moderate g-loads due to their gyros tumbling. I believe that problem was corrected by the time the MiG-21bis was being produced. But either way, the gyro sight should have generally worked as well or better than the WW2/Korean War era gryo sights that they were developed from. The whole point of "Auto" is to feed radar range rather than having to twist the throttle to estimate the range visually. So, I don't really buy that auto would lock the range input to 300m, as you could achieve that by simply twisting your stick to minimum range. I can understand locking the reticle to 300m to act as an obivious indication that you are at optimum range, but I would expect the pipper movement to still compensate for the radar range input.

 

Of course, you have a real MiG-21 pilot on your team, so his experience/knowledge trumps anything I think. But how much does a pilot know about the inner workings of their avionics and how often did he employ the gunsight with live fire on aerial targets?

[xxJohnxx]

Of course, you have a real MiG-21 pilot on your team, so his experience/knowledge trumps anything I think. But how much does a pilot know about the inner workings of their avionics and how often did he employ the gunsight with live fire on aerial targets?

 

Probably quit much, because they sure have the full maintenance and possible also other manuals for the aircraft available, else a simulation to this depth wouldn't have been possible.

 

But as you already wrote, the ASP gunsight does not receive any data from the radar when used in Air-to-Air engagements. It calculates lead for the optimum firing range, which is as you already know, 300m.

 

I am also not sure why the Auto mode must get the data from the radar in your opinion. Yes, it would be more practical if it would get data from the radar, but even if it is fixed range only, it is still much easier to use than completely manual lead.

[Art-J]

I think the sight works quite right in manual adjustment mode. It's been many months since I made an experiment in gunnery tutorial mission and started dialing in any distances between 300 and 600 manually, while trying to hit the A-10 drone, which was loitering over Krymsk (?). I remember though, that the bullet drop was calculated more or less properly, the piper was moving lower and I was hitting the drone as intended (although the experiment also confirmed that trying to shoot and hit anything turning at distances further than "fixed" 300 is useless/stupid anyway).

 

Haven't checked it in recent versions.

[MBot]

Is the gunsight actually working correctly now? I just ran some tests trying to shoot down an F-4 doing lazy orbits and aiming with the pipper always produced bullets passing behind the target.

 

Also I remember that previously when setting the ASP to auto, the Intercept Angle knob on the right would adjust automatically when pulling Gs. Now it stays fixed at zero whatever you do.