L-39 Radio Navigation in the NTTR (how to)

I see many L-39 pilots that do not know it is possible to fly radio navigation in the NTTR with the L-39. This thread will explain how to make it happen and what to expect. While I am not qualified to teach IFR, I can help with learning from the L-39 user manual, which can be pretty confusing. Most of this is applied to MP flight. This, in some ways, limits how you can fly the L-39 as some items are controlled only from the back seat.

I know I had some trouble learning from the manual and I've talked with others that posed the same questions. I hope this can help get around that for some.

Beacons.lua file

The beacons.lua file.

To fly radio navigation in the NTTR, the beacons.lua has to be modified to include RSBN and PRMG beacons. I forget who first modified the file to do this. I think I can remember 'Tarres' making a mod and I *think* this is where the attached file originally comes from. All due credit goes to the mod maker. I know others have fixed errors along the way to get to this final version, which is 100% tested as of 2.1.1.6837. It works online or offline, no difference. You may use any modified beacons.lua you wish, as long as you know the frequencies and they work (some don't from the original files).

In the modified file, copies of original ILS and VORTAC beacons are re-created as PRMG and RSBN beacons. These beacons act just like the original RSBN/PRMG beacons are supposed to, they do not interfere with the original ILS and VORTAC beacons, they do not add objects to the map to affect performance, they do not generate any log file errors (the original N Las Vegas ILS does, though) and it does not affect any integrity checks.

The zip file contains a readme.txt, beacons.lua file, RSBN PRMG 211 NTTR.txt file and ARK NDB 211 NTTR.txt file.

File can easily be installed manually or with JGSME. Location of file is usually:

C:\Program Files\Eagle Dynamics\DCS World 2 OpenAlpha\Mods\terrains\Nevada\beacons.lua.

Copy or rename the original file before installing.

Any bad points? Only known bad points of using the beacons.lua mod is when in the Mission Editor (ME), the blue modified beacons are inlayed across the tops of the original beacons when looking at the ME map. F10 map VORTAC beacons are also overlaid and can be difficult to read.

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JGSME version is available here - Note this version does not contain txt files. I cannot edit this file to add txt files. This beacons.lua does not have added NDB markers.

Zip file below contains beacons.lua with NDB Marker beacons and txt file contains all RSBN/PRMG info. No txt file for NDB's just yet, but all should work.

L-39 Controls you will use

1. RSBN Channel Selector.

2. PRMG Channel Selector.

3. RSBN/PRMG Mode Switch

After RSBN and PRMG channels are selected, the RSBN mode switch controls the following:

PRMG Landing mode. This works like an ILS. RSBN callsign button is to PRMG beacon. Distance to the PRMG beacon is measured in KM (instead of RSBN beacon).

RSBN Navigation mode. This works like a VOR/DME receiver. The RMI pointer will point towards the RSBN beacon and distance from the RSBN beacon will be measured in KM. RSBN callsign button is to RSBN beacon.

RSBN Glidepath mode. Each RSBN beacon has a glideslope built in and distance from the RSBN beacon will be measured in KM. This switch allows you to follow it down to pattern altitude.

4. SDU Remote switch is used to slave the ILS crosshairs to the ADI. I remember this worked great in the Su-27, but the code for this in the L-39 is not as polished. It might be helpful to some. When slaved, the red T and K flags will match the white T and K flags of the HSI/RMI and you will have pointers to show where to move your controls to follow the selected path.

5. ZDV-30 RSBN pressure setting.

This must be set to match the RSBN beacon you want to use a glidepath.

PU-26E Control panel for GMK-1AE DG

This panel will slave the HSI to the Magnetic compass (MC) or the Digital Gyro (DG). You can set the 6. DG/MC switch to DG, then use the switch below it (switch #7) to move the DG heading left/right as needed to match the magnetic heading.

8. RSBN Radio button

Pushing and holding this button will allow the RSBN/PRMG Morse code identifier to be heard on the intercom. You may have to hold it until the repeated codes play completely.

RKL-41 ARK-22 ADF/RMI

The RKL-41 ARK-22 RMI/ADF (radio magnetic indicator/automatic direction finder) can allow you to cross check your position. The RMI will point at an A.M. band frequency it is tuned to. If you are flying north, and your RMI points 090* to your NDB, you are somewhere due west of this beacon. It can be used as a backup for the PRMG if there are inner/outer marker beacons at that airport. You would fly over the outer beacon, start a timer, then time yourself as you fly over the inner beacon and hopefully can then see the runway while under your altitude minimum. Each NDB has a unique Morse code identifier. The RMI/ADF is located on the front instrument panel, under the VVI gauge.

1,2,3 are tuners for the "Far", "Outer" or "O" NDB. The left non-numbered wheels control the "I", "near" or "Inner".

1. Right/left click here for hundreds and thousands of the frequency.

2. Right/left click here for tens of the frequency.

3. Mouse wheel here for the decimal of the frequency.

4. "Off / C Automatic" - on off switch.

"Aut" or automatic means when you have inner and outer marker NDB beacons set and this will switch automatically when you fly over these beacons.

"Man" or manual means you must switch the "O"/"I" switch yourself as you fly over these beacons.

"Ant" or antenna mode "is used to adjust RKL ADF to NDB frequency" and does not show the direction to the NDB (from DCS manual).

'Loop' mode is for "finding radio stations be hearing" (from DCS manual). I am guessing you use L/R switch to rotate the antenna and listen for the loudest signal.

5. "TLF/TLG" - TLF is normal direction finder operation. TLG uses the meter "8" so you can tune for maximum reception. The exact listed tuning is not always the optimal setting. TLG stops the Morse code identifier from playing in the radio intercom.

6. Front / Rear seat control of ARK-22. Untested.

8. Meter - shows signal strength when in the TLG mode. No Morse code ID is played.

9. "O" / "I" switch. Switches between the two ARK-22 channels.

10. ADF switch slaves the ID signal to the intercom for identification.

About RSBN/PRMG/ARK

RSBN beacon

The RSBN beacon is very much like a VOR/DME. It has 360 radial radio beacons that you can fly outbound or inbound. RMI pointer will always point at this beacon and distance in KMs will be displayed. By using your course heading selector that you can set as inbound or outbound, you can intercept these radial beacons, allowing you to fly to any location on a chart (with radio signal). Each RSBN beacon has a glideslope that, when pressure is set correctly, will display on your HSI/RMI:

21km and less - 600m altitude level.

132km-21km is a glidepath from 8km altitude to 600m.

The RSBN has a steeper glidepath than a PRMG. It is meant for penetrating a cloud layer and coming in level at pattern altitude. At 21km or so, the End of Descent annunciator will light up. This will signal you to swith to PRMG landing mode. The PRMG glidepath will be high above you. You fly level until you intercept it again.

The ZDV-30 RSBN pressure setting must match the landing airfield QFE pressure setting! If pressure is not set correctly, you have a high likelyhood of CFIT (controlled flight into terrain).

Each beacon has a unique Morse code identifier.

PRMG beacon

These work like ILS beacons and extend out to 70km. You must have the channel selected and the RSBN mode switch set to landing. T and K flags will turn off when you are receiving these signals and KMs to the PRMG beacon are displayed. Each beacon has a unique Morse code identifier. You can choose to fly this from 70km out and ignore the RSBN glidepath. Runways that are sloped matter a lot to ILS. Uphill runways mean low angle approaches (as in North Las Vegas). Fly above the glidepath on these.

NDB beacon

Non-directional beacons are used for homing with RKL-41 avionics. They do not emit radials (no inbound or outbound) and there is no distance measuring equipment (DME). These transmit A.M radio station frequencies and can even play music instead of Morse code identifiers (no longer modeled in DCS). Often used as marker beacons for landing.

Standard Landing Procedure

The L-39 Manual is quite confusing when it teaches operation of the RSBN/PRMG. Here is a quick run-down of what the manual says:

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Sector A/B - you are either making a straight-in approach or must maneuver to get into position for approach and receive PRMG. Sector A is within the PRMG localizer and glideslope.

Please note you don't have to set the Inner/Outer NDB beacons. It is a redundant back-up and can confuse you at first. The markers will work without these frequencies being used.

The RSBN Glidepath mode is used when descending from cruise altitude, which is generally 5-8km MSL (mean sea level), and it is usable anytime within 132KM of your RSBN beacon. It is used to descend through a cloud deck to pattern altitude of 600m, 21KM from your selected RSBN beacon. The "End of Descent" lamp will light and you then fly level until you intercept the PRMG glideslope or make a visual landing. You are expected to fly at 400-500kmh.

If you are in the before mentioned "sector A", you can bypass the glideslope mode and use landing mode instead.

Landing procedures from the L-39 manual for RSBN/PRMG can be quite slow and a bit confusing. I've come up with this procedure that is based on the book numbers for a long PRMG landing after completing the RSBN descent.

Metric

- 600m alt, 400kmph, neutral trim.

- Distance X, 80-85%, airbrake out, -6 VVI.

- 340kmph, extend gear, -6 VVI.

- 310kmph, flaps out, -4 VVI.

- 260kmph, full flaps, airbrake in, let nose droop to prevent blooming, throttle 90-95%, -4 VVI.

- 230kmph approach until flare.

- Outer beacon marker = 200m, 260-300kmh.

- Inner beacon marker = 80m, 230kmh.

Imperial Units:

Added soon.

Note Distance X is your choice and the same procedure is always used. For doing PRMG/ILS, it is best to be in the landing configuration a long way out and fly the approach at 230 kmh. The L-39 needs to be flown all the way to the ground under power. When the L-39 decelerates, it can fly a bit crooked and it is easier to keep straight when under power.

By changing Distance X, you can use this landing procedure all the time, VFR or IFR. When you do this landing procedure and time it perfectly, it is a very satisfying experience (and landing).

Using this in the NTTR

Summary:

I used to think this flying the L-39 PRMG/ILS was difficult, but I have found it a lot more simple if:

You understand and can operate the avionics.

You understand how the beacons work.

You learn and practice a standardized landing procedure.

You center the ILS crosshairs, matching the glideslope to the VVI. (yellow lines)

Match the localizer to your heading, which is matched to your level Artificial Horizon. (red lines)

Simple as that. With practice that is...

T, K flags? I used these teasers to help me learn and remember

"loKalizer"

"gliTeslope"

It works. Extra points for silly accents.

Addmentum

FLIGHT PLANS AND EXAPMLES OF AVIONICS USE

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Finding QFE at destination airfield/RSBN

To find QFE of your destination airfield and RSBN beacon:

1. Note Current runway altitude and QFE.

2. Note destination runway altitude. Note difference between the two numbers.

3a. Destination is higher than departure - subtract difference from departure runway alt (using altimeter QFE setting knob).

3b. Destination is lower than departure - add difference to departure runway alt.

4. Note new QFE setting on altimeter.

5. New QFE setting is your destination runway altitude (very close) and this value can be entered into the ZDV-30 RSBN Pressure setting.

EXAMPLE

1.5.7 AO server is currently at 76.00 QFE (from briefing), Sukuhmi altitude is 11m. Mozdok altitude is 155m. 144 is subtracted on the altimeter using QFE setting knob. New value is 74.7.

Altimeter will now read at or near '0' at Mozdok. Entering 74.7 on the ZDV-30 means we get a 600m altitude when the End of Descent lamp comes on during our RSBN approach.

I recommend rounding the number 'up'.

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Setting Off the Scale QFE

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Manual RSBN Use

w.i.p.

I am offering this file here for a friend. It is a beacons.lua for 1.5.7 that has some working PRMG runways.

MODIFIED BEACONS:

I added a RSBN beacon at Kutaisi as RSBN channel 8. I did not add any more of these.

Airfield Runway heading PRMG

============================================

Kobuleti 070 Chan 11

Maykop 219 Chan 36

Maykop 037 INOP

Krasnadar Center INOP INOP

Senaki 095 Chan 13

Sukhumi 296 Chan 21

Krymsk 220 Chan 26

Mozdok 263 Chan 23

Mozdok 083 INOP

Please note: Kobuleti runway heading is 070 and not 078 as I originally posted.

That's a great writeup and very useful indeed! Thank you!

Is there any guide to using the RSBN equipment without any signal (manual input, mid flight updates, using with ARC stations)?

That is a great idea, Fred. I haven't done any advanced functions with the avionics. I'll be happy to write up what and when I learn it. Anyone with info on this is welcome to post it here.

I wrote an example in the Caucasus map. Not at home now.

I'm preparing a flight example to send to Smil.

Edit: found

https://forums.eagle.ru/showpost.php?p=2518544&postcount=9

Outstanding! Thank you Tarres. I love the flight plan examples and hope to include more of those.

I never knew that about the RKL-41. There is supposed to be some bad weather coming and it should allow me extra time to edit the original posts about this.

I can remember seeing a post about roughly estimating QFE settings with known altitude changes. If anyone could remember or find that one it would be very helpful.

Looks great man. Really looking forward to the next version including the ndbs. Up to now you had to make a choice whether to have a modded beacons.lua active that either gave you ndbs or rsbns...and switching around depending on which aircraft you fly isn't the greatest thing. The latest 2.1.1 release linked in you second post does not contain any txts or info on the different RSBN/PRMG channels, where can i get the latest files on that?

Nice work. Thanks.

Very useful, thank you!

Looks great man. Really looking forward to the next version including the ndbs. Up to now you had to make a choice whether to have a modded beacons.lua active that either gave you ndbs or rsbns...and switching around depending on which aircraft you fly isn't the greatest thing. The latest 2.1.1 release linked in you second post does not contain any txts or info on the different RSBN/PRMG channels, where can i get the latest files on that?

Thank you for pointing this out. Really need those to enjoy flying with the beacons. I will have the link to the file here very soon.

I have added a link (post #2) to a zip file containing the txt file that lists RSBN/PRMG.

The DCS L-39 uses true north for navigation and RL uses magnetic north.

The DCS L-39 uses true north for navigation because in the Caucuses, it would have been realistic and a typical equipment spec.

An RSBN azimuth uses a reference signal aligned with the Northern meridian (true north) at the transmitter. AFAIK the L-39 RSBN azimuth needle on the RMI points to a 'true' bearing and the RMI is calibrated to use the same.

A VOR transmitter on the other hand is aligned to magnetic north (radials 1 to 360 with 360 aligned to magnetic north).

A civilian L-39 flying in Nevada, would have a different spec. with western VOR, ILS and DME equipment and navigate using magnetic bearings and a RMI/HSI calibrated to match.

Thanks very much Ramsay! I enjoy learning about this and how it works.

Have added section on finding QFE on post #8. This post will contain examples and flight plans for radio navigation flight.

Thx for adding those txt files.

This is a very useful and helpful thread Smil, but I hurt myself trying to soak in all the information- VERY in-depth. Nice work! Bookmarked for further reference. Thank you. :thumbup: