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PRMG + SAU command mode?


Fishbreath

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I tried an instrument approach at Senaki, and I couldn't get the SAU command landing mode (flight director bars) to provide reasonable inputs. The glideslope and localizer bars on the KPP and NPP both were working correctly, but the KPP director needles were providing impossible input (demanding 20+ degrees of up pitch while I was on glideslope, not showing the localizer director needle at all). Here's the procedure I've been following:

 

1. Line up on runway radial.

2. RSBN descent mode to airfield vicinity.

3. Landing mode, fly level until glideslope and localizer signals are picked up (black windows in the center of the NPP).

4. SAU landing command mode push button.

5. Deviation bars working correctly, providing error information. Flight director needles not providing correct information.

 

Is it working for other people/do I have some local configuration problem, or am I missing a step in the setup?

Black Shark, Harrier, and Hornet pilot

Many Words - Serial Fiction | Ka-50 Employment Guide | Ka-50 Avionics Cheat Sheet | Multiplayer Shooting Range Mission

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Further testing suggests that, for me, the KPP needles are unreliably unreliable. I tried another two approaches, and at times, the KPP pitch/altitude needle seemed correct, but progressed to demanding changes that would have taken me off of glideslope. Sometimes it didn't appear at all, or disappeared off the bottom of the scale (while I was not far from glideslope) and never came back. Cycling the SAU (cancel landing modes, directed landing mode) occasionally brought them back. The bank/heading needle was never correct as far as I could tell; I was slightly right of centerline for most of the approach, and the needle was consistently commanding right bank.

 

Edit: that certainly could be. For the time being, I'm just flying my instrument approaches with the deviation bars alone, like a caveman, but I'd like to know if I'm just doing something wrong. :P

Black Shark, Harrier, and Hornet pilot

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I know the MiG is old technology, but I think the cavemen flew Bleriots, and not 1950s jets!

Oh no, wait, they still hadn't discovered flight 2000 years ago, silly me! Also, if something is unreliably unreliable, doesn't that make it by default reliable?

 

Please try when making a bug report, do it with a track, and keep emotive language at bay. This is of course if you wish to make a positive contribution, and make the product better rather than just complain.

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I know the MiG is old technology, but I think the cavemen flew Bleriots, and not 1950s jets!

Oh no, wait, they still hadn't discovered flight 2000 years ago, silly me! Also, if something is unreliably unreliable, doesn't that make it by default reliable?

 

Please try when making a bug report, do it with a track, and keep emotive language at bay. This is of course if you wish to make a positive contribution, and make the product better rather than just complain.

... dito.

 

And talking about complaining ... where was he complaining? He was describing what he saw.

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Yup, just making a little joke. (Whenever I have to use a slightly less-technological alternative, like over-the-air high definition TV instead of cable or satellite high definition TV, it's like a caveman.)

 

'Unreliably unreliable' isn't hyperbole, it's a statement of the problem: sometimes SAU command landing mode is closer to correct, sometimes it isn't. It doesn't have a dependable failure mode.

 

And, of course, I remain firmly against the idea that we must always behave as though Eagle Dynamics and third-party devs can do no wrong. Obviously, they're not perfect, and although Leatherneck has done an amazing job with the MiG, they certainly would agree that there are some things remaining to polish to perfection. That's why I made this thread—to see if I ought to promote this problem to a bug report, or to see if there's a problem with my setup, my installation, or my procedures.

 

Can anyone else reproduce my issues? This afternoon, I'm going to try some approaches at other air bases and see if I get the crazy director needles at fields other than Senaki-Kolkhi.

Black Shark, Harrier, and Hornet pilot

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Track and mission files demonstrating the issue. (Mission starts you ~30-35 km from Kobuleti, 600kmh, 600m. Kobuleti is RSBN/PRMG channel 15.) The KPP bank director is correct in this track. As you move closer to the airfield (and closer to glideslope), the pitch director moves up the KPP until it vanishes. I cycle SAU directed landing mode off and on several times. It doesn't come back until final approach, and still indicates incorrectly.

 

I'm uploading a Youtube video too. Will edit post when it's done.

 

Edit:

 

prmg-landing.trk

MiG-21 Landing Test.miz


Edited by Fishbreath

Black Shark, Harrier, and Hornet pilot

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While we're at it, could somebody explain me in simple layman's terms what the purpose of SAU directional mode is? I find chapter of manual related to this mode quite confusing. It says "the SAU won't interfere with the pilot's inputs", quite peculiar for a device which is supposed to be an autopilot :D. So it seems I still have to chase the yellow needles manually? If that's the case, then what's the difference between "normal" chasing the needles without SAU and chasing them with SAU-directional on?

i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.

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While we're at it, could somebody explain me in simple layman's terms what the purpose of SAU directional mode is? I find chapter of manual related to this mode quite confusing. It says "the SAU won't interfere with the pilot's inputs", quite peculiar for a device which is supposed to be an autopilot :D. So it seems I still have to chase the yellow needles manually? If that's the case, then what's the difference between "normal" chasing the needles without SAU and chasing them with SAU-directional on?

 

Without SAU directional mode, you don't have the middle needles on the KPP at all—just the needles on the edges, and the ones on the NPP. SAU directional mode gives you the same sort of ILS direction as the Su-25, as I read the manual, while having it off gives you no direction at all, just error information.

 

Edit: to be clear: chasing the error needles isn't too far from chasing the director needles, but if you're using a director system, you fly onto the director needles, which then move to fly you onto the right course and slope.


Edited by Fishbreath

Black Shark, Harrier, and Hornet pilot

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The horisontal director bar must be always horizontal :)

Also, it appears to us, that glideslope, localizer beacons and DME- are virtually positioned in the center of the RWY, thus making your approach too high and unsafe.

look at the video of approach to Kobuletti, at time 3.20. Distance from RSBN beacon is 9km, hight is 500m so you must be slightly above standard GS, but GS bar shows you that you are below!

(Russian standard GS has angle 2'40, and knowing distance you can adjust your vertical profile, i.e: Dis=10, height must be 5, dis=8 height=4...)

Our russian colleague User has done some researches about KPP. Here

He is very experienced real life mechanic, and has made a real research.

P.S.

Director needles show you where to turn your aircraft. In civ, aviation with that system minimums are cat.II(30mx350m) and with deviation bars just cat.I(60mx550m)


Edited by GUMAR

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(Russian standard GS has angle 2'40, and knowing distance you can adjust your vertical profile, i.e: Dis=10, height must be 5, dis=8 height=4...)

 

On p.119, the English manual says the descent angle is 4 degrees. (Which seems very steep to me!) I don't know if it's in the same place in the Russian manual, and I'm afraid my Russian is too rusty to check. It's right by Image 9.15.

 

Thanks for the link to User's research.

Black Shark, Harrier, and Hornet pilot

Many Words - Serial Fiction | Ka-50 Employment Guide | Ka-50 Avionics Cheat Sheet | Multiplayer Shooting Range Mission

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In russian manual for MiG-21UM the glideslope angle is just how I said. Unfortunately we don't have russian manual for 21BIS, and real pilots say, that the were just paper updates for old modifications, and no complete manual.

Although such high glideslope can be used. In MiG-21PFM Piloting technique there is something similar, and I've seen "300m over middle marker" in manual of Su-7 (same speeds). But I think it is difficult, and now it became an old technique. All russian high-speed airplanes (Su-24, MiG-31) and other fighters, attackers, bombers have standard 2'40 degree GS.

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Реальные хотелки к ЛО3 по Су-25 в основном...

ASRock PG9, i-5 9600KF, MSI 2080Ti, 32GB 3466

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