MiG-21, Help with PRMG

Maico · February 23, 2019, 5:31am

Gents,
I need help from this community. In the last month I have dedicated myself to flying the Fishbed in bad weather. I can not get down in one piece to save my virtual life. It has been hilarious crashing into the ocean and sliding across the grass meters before the runway.
This week I began flying and researching PRMG very closely. I believe the system is broken. Went to ED’s site and found out Im not the only one having this problem. However, this could be a coincidence. I need to know if anyone here is catching the glideslope. This is where it falls apart for me. I cant activate command or auto mode. Yes, I am in Landing mode (switch down). I approach from 1000 m right at the base. I have been trying in daytime with good weather. No Joy. Please help.

Thanks All,
Maico

Maico · February 23, 2019, 11:23am

Got an answer at ED. PRMG is working. Apparently im too dumb to use it. How do i get it so wrong?

Aginor · February 23, 2019, 12:09pm

Have you tried learning the PRMG in a plane that is a bit easier to fly (the L-39)?
Maybe that helps with understanding its quirks without the added hassle of piloting one of the hardest to fly planes in DCSW.

Maico · February 23, 2019, 12:47pm

Thanks Aginor,
No i have not. But what you say makes lots of sense. I’m being hard headed because I got so much time invested in this. The '21 is my first love. I did take a ride in the Mirage and found it so easy to fly.
I will the the Albatross. Perhaps i need to be in a trainer lol.

Sryan · February 23, 2019, 1:34pm

I just did a PRMG landing in the MiG-21BiS in automatic mode. We might be on different versions or something, though. I can’t tell if you got it all set up correctly but what strikes me as odd is how you explain that you approach from 1000 metres. I usually enter landing mode at about 25km. For the last 1000-2000 metres, I deactivate the system and fly manually. The system won’t really auto-land you safely (it will slam you into the tarmac with that 4 degree glideslope) it will just get you close enough. Maybe if you try it from a bit further out, it will work?

Maico · February 23, 2019, 5:15pm

Thanks Sryan,
I appreciate your support. You made me realize i cant catch the glideslope at 1k high and 20k away. I just realized it makes no sense. Perhaps i am misreading my YouTube videos. I thought they said activate landing mode at 1000 m. WRONG!! I out tonight. Cant wait to get home and try.
Thanks Again
Maico

Sryan · February 23, 2019, 7:49pm

Roger that, good luck and let us know if you need more help! I crunched the math on your numbers and you should be a little over a degree below the glideslope. Since PRMG transmits in the 2-6 degree range, you should have been getting a signal. Does the white flag for glidescope stay on? Can you capture the localizer in landing or descent modes?

Maico · February 23, 2019, 9:59pm

Sryan,
Thanks for helping out. Another dozen tries tonight. I can get auto to engage but it just wants to kill me. To low? It almost always points down at the ground and must disengage it. In landing mode i don’t get glideslope till its too late. I get only localizer. Again this might be me too low. Maybe i am expecting too much from this old system. I only want it to get me close in bad weather. Im using good weather to learn. I cant trust it yet.
Just to be sure, my runway is 07. I put the double needle on 70 then. Right?
From 5k meters up and at 40 to 30 km away i still cant get glideslope, only the left blinker is black. What gives?

Hangar200 · February 23, 2019, 10:27pm

I have gotten that answer fro various Support and Help Desks for years…I might be upset if they hadn’t been correct.

Well now you have piqued my interest. I have only recently (re-)mastered landing the 21 by hand in good weather. I need to recheck some things I read about AOA…in a Chuck’s Guide…and shoot a few more approaches.

All that said, the Mig-21 is not an all-WX fighter. My understanding is that the command/auto land systems are only there to get you within 1-2 Km of the airfield at 500 m AGL - from there you need to hand fly it in. The Viggen is similar but for a different reason (ILS-esque aid is not aligned with RWY CL).

This is a bit of a different approach (no pun intended) than a lot of western ILS systems where you often could fly the needles all the way down to the threshold but are required to sight the runway at a certain point or GA.

Need a check here form RW pilots. Even after sighting the runway, can you continue on the ILS? If so, where too? Threshold? Or do you automatically go to visual/hand flying once runway in sight?

Sryan · February 24, 2019, 12:05am

@Hangar200 it depends on the quality of the ILS that both the aircraft and the designated runway are equiped with. These qualities are standardized and divided into five different levels. ILS CAT I is the lowest level, and has a minimal decision altitude of 200 feet and a runway visual range of 1800 feet for a properly lit runway, or a minimal visual range of 2600 feet if that is not the case. ILS CAT IIIC, the highest level, has no minima.

@Maico looks like we’re getting somewhere! I think you’re a little to high now before, I thought you were trying to activate the ILS 1000 metres in front of the runway, but what you were actually doing is flying 1000 metres high, which is fine! You won’t get a glideslope signal that far out, it has a maximum range of about 25km. I crunched a little more maths for you, hope it helps, all altitudes are QFE relative to the airfield you are trying to land at. So if you want to use baro, consider practicing on a runway close to sealevel like Krymsk or Sochi.

At 25km, the glideslope altitude should be around 1800 metres.
at 20km, the glideslope altitude should be around 1400 metres.
at 15km, the glideslope altitude should be around 1050 metres.
at 10km, the glideslope altitude should be around 700 metres.
at 5km, the glideslope altitude should be around 350 metres.
at 1km, the glideslope altitude should be around 70 metres.

Since you have trouble acquiring the glideslope, and I know that the glideslope emits in a 2-6 degree angle, I also calculated the min and max QFE altitudes you should be getting an (extreme high or low) glideslope signal.

at 10km, the min and max altitudes for a GS signal are in between 350-1050 metres.
at 1km, the min and max altitudes for a GS signal are in between 35-105 metres.

If there are obstructions, it might not always be possible to get a signal at the minimum described altitude. I think Nalchick and Sukhumi or Gudauta have buildings close to the runway.

If the SAU (autopilot) is trying to get you killed, be sure to give it plenty of speed and atleast take-off flaps! Remember that the SAU cannot control your throttle, so keep the speed close to/over 400km/h. The fishbed doesn’t really mind landing at higher speeds with a lower rate of descent.

The PRMG doesn’t really care about the position of the RSBN/ARC needle. You can put it on 70 (or whatever the magnetic bearing of your runway may be) for your own reference (it’s nice for getting close the localizer signal) but it is not required.

Hope it helps! Hopefully you can do a full PRMG approach soon for me it works. It gets me to within 1000 metres of the runway so I can complete the landing. (it will fly me all the way to touchdown… but it will impact the runway with a 10m/s* descent rate which will send you bouncing and cartwheeling).

*equals 2000 feet per minute

Maico · February 24, 2019, 4:01am

WOW! Now this is useful information!
@Sryan, Thank you for going all out. Its is much appreciated. These calculations make my mental picture much clearer. My basis for Auto land is Pick that Banjo’s Youtube video. I totally misunderstood his guidance. With your calculations i should avoid the dreaded Pitch down i m experiencing.
Ill give it a whirl!

Maico · February 24, 2019, 2:12pm

EUREKA!!! YES! Success at last. Sryan, you are the man!
Here is how it worked out. I start at about 4000m. I come down to about 2000 m using Proceed mode. (Top position) At about 25 km away from Kobuleti, I go to Landing mode(Bottom position) and hit the Automatic Landing mode. The Glideslope is captured and the aircraft glides down to the lit runway. I then take over and land by hand. This is amazing. I let the Auto mode go too long once and as you said it bounced me pretty good. At least I did not blow a tire.
So to be fair, I crashed a bunch trying to do it in bad weather. I then did it at night and faired much better. Got two in a row now. I am so pleased. The Acid test of course will be this mission where I have to land in Zero vis. But for now, I am very happy. It took me a lot longer to get this than I thought. Your help was indispensable and your last post is going in my MiG-21 Book. (Yes, how sad, I have a MiG-21 binder) LOL
To be clear, here were my mistakes.
Trying to aquire the signal to far away. As you stated it only reaches out to about 25km.
Going to low and close to the ground (following the Proceed Mode) then cant acquire because I’m too low.
Fixing these two things was easy once you pointed them out.

Thanks a bunch.
Maico

Sryan · February 24, 2019, 3:05pm

Extremely glad you got it to work! Good luck on the zero vis attempts! For me this is what Mudspike is all about teaching and learning cool stuff. I slightly changed the topic title, should a needing soul stumble upon this topic in the future

Maico · February 24, 2019, 6:54pm

Good Call, Its got a lot of good info in here.

wheelsup_cavu · February 24, 2019, 8:15pm

Too bad the solution “Approved Answers” tag only applies to questions in the “Hardware and Tech Questions” forum. Imo, This is one of those times it would be appropriate for a thread outside that forum.

Wheels

Sryan · February 25, 2019, 4:16am

Maybe that is something @fearlessfrog can assist with? Perhaps a special tag for answerable questions or a section for flight sim questions (if multiple people agreed on having that)?

fearlessfrog · February 25, 2019, 5:39am

There you go, added. Under the ‘…’ icon on each post you can now ‘Mark Post as Solution’ and it’ll bring it up to the first post as the answer. That setting used to be more in-you-face in terms of boxes etc, but now it seems subtle enough we can use it anywhere.

Hangar200 · February 25, 2019, 1:02pm

After reading all the posts I decided to give it a go…a dark night landing…I followed the manual and the most excellent posts above…I really like how everything you need to follow is on the KPP. At 30 Km things were looking good…

…but then I got “behind the jet”

…well…yes and no…it broke off my landing gear…but that may have cushioned the impact…I would have stopped about halfway down the runway…if I had been on the runway…as it was I ended up almost 5 km to the north…

It was kind of surreal…I was all dirtied up and had slowed down to about 300 kph…was looking for the runway when the plane just sort of bumped and stopped.

But, as they say, any landing you can walk away from…etc.

(Note to self: Try practicing in CAVU first.)

Maico · February 25, 2019, 5:01pm

You have to land it yourself. If you catch it kind of late, it will still scare you by bouncing real good.
System is meant to get you down to make a safe visual landing. Works great for me in Daytime. I can get down at night using proceed but automode eludes me in bad weather or nighttime ops. Daytime no problem. Who cares. I guess I will just have to learn to hate it.
After 3 weeks of it. I am officially DONE WITH IT. Sorry for the rant.

Bearhedge · February 25, 2019, 7:45pm

I have to say you haven’t gone about this the easy way! As far as I know the L-39 system works similarly (although not sure - I haven’t tried it in the MiG yet): if it does, ironing out the procedure at just about half the speed would have been a lot less stressful!