PRMG RSBN & SAU Bugged? OR Is it just me?

[Weegie]

So I'm learning the Nav in the MiG-21

 

Chuck's guide, the manual and JohnXXX's videos have been a big help and I'm hoping to do some myself, explaining some more on what I've found.

 

To practice I have a very simple, take off from Kobuleti, fly over the sea until 50-60 clicks out then navigate to Batumi. In the evening in clear weather. This way I have visual clues to see what is going on while using the NPP/KPP to do the navigation

 

BUT

 

Problems

 

1) Sometimes I find the when in range with no flags on the KPP that the ILS bars on the KPP are indicating above the circle telling me to climb when I'm actually too high in the first place. I'm unsure if its a reversal of the bars, I need to experiment more. Other times it works as described

 

2) Selecting the directional Autopilot for landing to get clues I get nothing. If I'm understanding when in directional mode the Director on the KPP (the yellow bars) should also give you clues for ILS approach.

 

3) On the same topic when I select Auto for landing both green lights on the Autopilot panel light, yet the manual states the modes are mutually exclusive????

 

4) In nav mode on approach to Batumi if I fly the director nearly every time I don't get needle convergence, I've got the heading set for 180deg from runway heading and I start 50-60 Ks out, so plenty time for the system to respond. Usually I end up with one needle are 11 O'Clock and the other at 1 O'Clock. Then sometimes it works.................this has also forced me to learn how to manually intercept my chosen radial. Is this a bug or is it just intended to be deliberately unreliable?

 

I'm not knocking the MiG I think Leatherneck have done a fantastic job I love the pit, the textures, the flying characteristics and scary landing. I just wondered if others were experiencing the same frustrations

 

I'd love to see it finally debugged but that probably will not happen until some time well after Viggen release (which I've also bought). I've also been following the "State of the MiG-21" thread and seen Nav mentioned but no specifics

[grunf]

1) Sometimes I find the when in range with no flags on the KPP that the ILS bars on the KPP are indicating above the circle telling me to climb when I'm actually too high in the first place. I'm unsure if its a reversal of the bars, I need to experiment more. Other times it works as described

Never noticed it, but I usualy use NPP, not KPP. Was the NPP glideslope bar also in wrong position?

 

2) Selecting the directional Autopilot for landing to get clues I get nothing. If I'm understanding when in directional mode the Director on the KPP (the yellow bars) should also give you clues for ILS approach.

Are you picking the PRMG signal? Both flags off?

 

3) On the same topic when I select Auto for landing both green lights on the Autopilot panel light, yet the manual states the modes are mutually exclusive????

The modes are mutually exclusive, not sure about the lights :). In the past only one light was on, now in auto mode they are both lit. Not sure what is correct.

BTW don't use auto mode, it can't cope with the recent flight model changes.

 

4) In nav mode on approach to Batumi if I fly the director nearly every time I don't get needle convergence, I've got the heading set for 180deg from runway heading and I start 50-60 Ks out, so plenty time for the system to respond. Usually I end up with one needle are 11 O'Clock and the other at 1 O'Clock. Then sometimes it works.................this has also forced me to learn how to manually intercept my chosen radial. Is this a bug or is it just intended to be deliberately unreliable?

I'd suggest learning how to intercept the radial, because that's how it is in the real plane. The director needle is functional only in landing mode.

[Frederf]

1. The KPP T/K flags aren't to be trusted. They hide at times they aren't supposed to. Primary PRMG indications are the white bars on the NPP which are repeated as the yellow bars on the top and left of the KPP. Look for the white Kappa and Gamma flags to go out on the NPP for localizer (K) and glideslope (G) signal.

 

The director needles should only function when the approach command or auto modes are on to signify valid pitch and bank commands. Under every other condition the flags should show and needles should not deflect (yes even with RSBN navigation and letdown).

 

Yes if you fly level with the director needles active you will be ~1.5 dots above center GS when the directed pitch equals your actual pitch. However if you actually follow the pitch director you'll arrive on GS by ~7km. This whole thing is bananas as the pitch director should never tell you to climb realistically (it commands level flight if below GS). On top of that the GS is much too steep compared to real practice. Realistic angle would have you 3-3.5 dots below the DCS GS.

 

If you lose the GS signal entirely the position bar on the KPP will be at the top. This is its "hidden" or "no indication" position despite the fact you can still see it. The white Gamma flag on the NPP will attest to losing the GS signal.

 

2. The command and automatic modes of PRMG approach are controlled by two push-lights on the AP panel (the 3rd being stabilize). If you are within the localizer signal zone (DCS module also unrealistically requires you be in the GS signal zone) then when pressing this buttonlight it should stay on. Also the T/K director valid flags should hide and the director needles should provide steering direction. If there is any doubt if the command or auto modes are on check that their buttonlights are burning.

 

4. Don't fly the bank director needle in any other mode except command PRMG approach. It's not realistic. Whatever bank director behavior LNS invented for RSBN navigation kinda-sorta works. Inside 20-30 degrees is proportional and so the intercept angle approaches zero as the needle misalignment reaches zero which is a very weak intercept. You'll do much better ignoring the directors and just looking at the position bars or even just the course and bearing needles directly.

 

In professional flying the technique to intercept and track a relative bearing is to use big angles for coarse intercepts (e.g. 90) and small angles (e.g. 30) for small ones. When the needles are merged pick the course heading and watch for drift. If you aren't aligned or are drifting away pick a new heading 5 or 10 degrees corrected and observe the effect for a short while and repeat. With wind the process might take a few shrinking corrections e.g. +10 -5 +2 -1.

[Weegie]

Thanks Guys :thumbup:

 

granaf, you picked up on my problems and gave me some ideas it's appreciated

 

Fredref thanks so much for going to the trouble of laying out clearly the weaknesses of the module in detail, you're post explained so much

 

I was ASS-uming when the KPP flags were out I had valid Glidescope

BUT this is actually what was happening

 

 

 

As you can see no flags on the KPP but a Glidescope NOT VALID flag on the NPP, and of course the Glidescope inidicator on the KPP glued to the top of the its scale.

 

This is also why the SAU isn't behaving either, I noticed last night that it flicked on then off almost certainly due to an invalid Glidescope

 

I'm well aware I am waaaaaaaaaaaaaay too high and steep there this was just an experiment, I noticed if I fly a shallower approach the Glidesope flag on the NPP goes out, but it can be pretty dammed sensitive.................well for my ham fisted, sausage fingered approaches at the moment :joystick:

 

I'll never be an adequate let alone good pilot, but right now I am improving in leaps and bounds with this module

 

Apologies to LeatherNeck :poster_oops: as the module is more or less, working as intended but now I know the weaknesses I can "fly around them"

 

John :clown_2:

Edited January 3, 2017 by Weegie
spelling & grammer

[slicker55]

@Frederf,

 

.. another stunning reply - very impressed with your intimate knowledge of this model and learning so much from you - thank you once again.

[CoBlue]

Can't get PRMG working on Kobuleti rwy 07 (ch's 15 & 15), PRMG is behaving like back-course on the localizer & is very sensitive. I can't engage SAU command?

 

Can someone check if PRMG Kobuleti rwy 07 works as intended? thanx.

 

 

EDIT: PRMGs localizer is bugged, it gives reversed turn directions, tested on Caucasus map.

Edited December 28, 2019 by CoBlue

[Rolds]

I think the PRMG localizer is backwards as well, if the needle is left fly right and vice versa. I just did an approach to rwy 4 at maykop that behaved like this.

[Dr_Arrow]

It is unfortunately not working again :( Every second patch is breaking PRMG/SAU command/auto modes :(