Marker beacon knob turns off glideslope indicator

[some1]

Volume off, glideslope inactive

 

Volume on, glideslope active

[DishDoggie]

Have you tried it with the Flip Switch to the right on High?

[some1]

That switch is irrelevant.

On further search, this behavior may be correct if the knob controls the whole glideslope/marker receiver (R-1963/ARN) and not only the marker lights. Not sure, it may also be wired to VOR radio switch. A strange quirk.

Edited March 21, 2022 by some1

[HILOK]

On 3/21/2022 at 9:56 PM, some1 said:

Not sure, it may also be wired to VOR radio switch.

it isnt. currently only affects G/S on ILS frq

[Volator]

I came across this issue today when trying to fly an ILS approach after a cold start, which sets up the aircraft with this knob turned to off. At hot starts, it is set to on.

This seems like a bug to me, as the manual says for the knob:

Quote

Turns the set on/off and adjusts audio signal volume.

... and for the NAV-COMM PWR knob:

Quote

Turns primary power to the radio set and to the R 1963/ARN Marker Beacon/Glideslope Receiver ON or OFF.

 

So clearly, the only means to switch off the Glideslope Receiver should be the PWR knob, not the Marker Volume knob, right?

[Flappie]

I was about to report this, then I read page 60 of the DCS: UH-1H manual, as you spotted it, @Volator:

So it's unclear to me if the glideslope+position indicator should work at all when volume is set to zero...

I'll keep investigating.

Edited March 22 by Flappie

[Flappie]

According to documents I found online, the Marker Beacon Volume knob is supposed to turn off the marker beacon receiver when the volume is set to zero.

• Source 1: https://www.aircav.com/cobra/cockpit/pilot/vor.html
• Source 2: https://f4.manuals.heatblur.se/systems/nav_com/vor_ils.html (Heatblur F-4E manual)

So maybe the glideslope indicator is OK, but the position indicator is bugged, after all.

What do you guys think?

Edited March 22 by Flappie

[Volator]

@Flappie

Thanks for looking into this!

I interpreted the manual in the way that "Marker beacon system on/off" means just that, only the marker system, not the VOR/ILS receiver. Otherwise there would be two on/off switches for the whole same system, which seems illogical. 

The HB F-4 manual says

Quote

The MB VOL knob (3) adjusts the volume of the marker beacon audio in the front cockpit.

so here the ILS system is also not connected to the marker beacon volume.

 

[Flappie]

Ah, it's clearer for me, now. Thank you! I'll keep digging.

[Flappie]

The 1988 UH-1H/V manual which was approved for public release (link ) is a good reference. I quote:

About ARN-82

Quote

VOL control - Controls receiver audio volume.

Power switch - Turns primary power to the radio set and to the R-1963/ARN Marker Beacon/Glideslope Receiver ON or OFF. Allows for accuracy of Course Deviation Indicators and Marker Beacon indicator lamp in the TEST position.

About Marker beacon Receiver

Quote

The Marker Beacon Receiver set is a radio aid to navigation. It receives 75 MHz marker beacon signals from a ground transmitter to provide the pilot with aural and visual information. The marker beacon controls and indicator are located on the instrument panel to aid in determining helicopter position for navigation or instrument approach.

...

VOLUME OFF/INCR control-ON.

Receiver NAV switch (MB switch if SB-
329/AR panel is used) - On.

Volume - adjust.

SENSING HIGH/LOW switch-As desired.

Stopping Procedures. VOLUME OFF/INCR
control - OFF.

...

VOLUME OFF-INCR control - Turns set ON or OFF and adjusts volume.

SENSING switch - HIGH position - Increases sensitivity / LOW position - Decreases sensitivity.

Marker beacon indicator - Flashes when marker beacon receiver is operating and aircraft is passing over the ground transmitter.

 

TL;DR

The AN/ARN82 Power switch turns on/off all three devices: UHF radio receiver, glideslope receiver and marker beacon receiver.

The marker beacon receiver can be turned off using its "Volume OFF/INCR" control.

The marker beacon light should flash whenever the receiver gets a signal.

 

I'll report the glideslope indicator issue (it should NOT be powered off by the marker beacon "Volume OFF/INCR" control). still not sure 

I'll report the marker beacon light not flashing (even THe UH-1H DCS manual states it should flash).

 

EDIT: Another interesting source here.

Edited March 23 by Flappie

[Flappie]

The Marker beacon circuit breaker also cuts the glideslope reception, but this might be normal: this probably cuts power from the R-1963/ARN receiver (which processes both glideslope and marker beacon signals).

I don't know what "R-104I" is, though. Maybe it's the name of that marker beacon light panel. In this case, the CB should not cut glideslope reception.

EDIT: this document differentiates "R-1041" and "R-1963".

EDIT2: It seems that the R-1041 receiver was only able to treat marker beacons. I think it was replaced by the R-1963 receiver after a few years. The latter treats both MB and GS signals and this is what we have in DCS. This means the "Marker Beacon R-1041" circuit breaker should be useless in the cockpit, especially since the DCS manual states the R-1963 receiver is powered on by the ARN-82 receiver, as@Volator noticed.

EDIT3: another source (CH-54 manual, this helicopter was equipped with R-1963 as well).

 

Edited March 23 by Flappie

[Flappie]

I'm still full of uncertainty. I eventually found out that the CH-54 had used the same R-1963/ARN receiver, then I found its manual in a very good state, here.

I was able to cross-check my UH-1H and CH-54 findings, and I get the following facts:

1. The R-1963/ARN receiver processes both marker beacon and glide slope.
2. The R-1963/ARN is basically a repackaged version of the MB/GHS section of the AN/ARN-123 Radio Receiving Set (source), which had two power sources (28 V and 26 V) one for the glide slope receiver, and another for the marker beacon receiver.
3. The R-1963 only has one 27.5 V power source.
4. The On/Off/Volume knob cuts the "marker beacon" receiver power source.
5. The circuit breaker cuts the "R-1963/ARN receiver" power source.

This contradicts this sentence found in the UH-1H manual...

Quote

Power switch - Turns primary power to the radio set and to the R-1963/ARN Marker Beacon/Glideslope Receiver ON or OFF. Allows for accuracy of Course Deviation Indicators and Marker Beacon indicator lamp in the TEST position.

...unless the ARN-82 power switch is mounted in series before the R-1963 power source... but I tested this in DCS: whenever the ARN-82 power switch is set to OFF, the glideslope signal is lost, but the marker signal is not lost.

This R-1963 /ARN diagram seems to confirm this.

 

From the CH-54 manual:

By the way, the CH-54 manual confirms the marker beacon light should flash (reported):

 

Ultimate conclusion:

• I think the glideslope signal being lost whenever the "Marker button volume" knob is turned off is correct as is.
• I think the marker beacon light and sound should stop working whenever the ARN-82 receiver is turned off. I'll report this if you agree with my findings.

 

Please comment. I'd like to be sure I'm not mistaken.

Edited March 23 by Flappie

[Volator]

Well, your conclusions seem to be correct according to the sources you quoted. Good research work by the way.

I still think this way of controlling the glideslope indicator seems kind of odd, but, well… sometimes there are these moments where a pilot wonders “what where they thinking when they constructed this?”