Quote from Ron Rollo on December 30, 2019, 10:46 pm

As I am doing a little "house keeping", I thought it would be a good idea to update this thread.  Back several years ago, Eric T. was on the verge of making available some really nice looking ACP front light panels, but I don't think that ever materialized.  So in the process of developing an all new Project45 v2.0 panel line, the Audio Control Panels have been updated to reflect exactly what you would expect to find in a well equipped Lear45!  The options include: NAV1, NAV2, VHF1, VHF2, HF1 ADF1, ADF2 and a DME.

The Audio Control Panel is the most challenging area in the Lear45 sim in my opinion.  Unless there are major advancements in the up and coming MSFS 2020 in the area, we will be forced to do the best we can do with what we have.  But with that said, we have DonnyRay Jones on our team!

The following was written by DonnyRay Jones and well worth archiving here:

Any Lear 40/45 can be equipped with one or two ADFs.  It is entirely up to the aircraft operator/owner.  Years ago dual ADF was the standard configuration on nearly all twins and transport category aircraft, but since GPS has become mainstream ADF usage has become less popular.  As a result you see some aircraft today with NO ADF installed and in the near future I think you'll see the ADF navaids decommissioned in the U.S.  HOWEVER - ADF is still in daily use outside the U.S., particularly in parts of the world where there is little or no aviation infrastructure for navigation.  And demonstrating an ADF approach is still a requirement in the U.S. when getting an instrument rating.  So I'd leave both of 'em in there for builders in other parts of the world where ADF is still popular.

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MLS (microwave landing system) was a short-lived technology intended to improve an ILS to the extent that zero-zero landings could be performed in suitably equipped aircraft.  They finally got the bugs out of it about the same time GPS came online.  MLS was an expensive refit to an aircraft and was not popular.  I've never seen a L40/45 with MLS actually installed HOWEVER it IS part of the software load in the RMU so I can't say "never".  I don't believe there is any MLS functionality in FSX or P3D.  Unless someone KNOWS for sure that MLS functionality exists I'd leave it off since this technology is also due to be retired in favor of GPS.

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"Lo Sense" and "Hi Sense" are functions of the marker beacon receiver.  A "marker" is a low-powered transmitter associated with a navigation facility or approach fix.  All marker transmitters are on 75.0 Mhz.  They transmit a directional pattern "straight up" above the ground.  When an aircraft flies over a marker transmitter the marker receiver detects this event and provides an aural and visual annunciation in the cockpit.  On an approach plate "OM" is the outer marker and "MM" is the middle marker. If you are on approach and you get the OM annunciation in the cockpit, you know more or less EXACTLY where you are located on the approach path.  Markers will be with us for as long as we have ILS systems.

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Decades ago, there existed what were known as "fan" markers.  They were located along major airways between airports.  It was very handy to monitor for the "airways" marker along your route as a means of confirming your position.  So think about that a second.  If you are in cruise flight you generally are going to be at a high altitude.  Because the marker transmitters are LOW POWER devices, if you were above 10-12 thousand feet you needed more sensitivity in the marker RECEIVER onboard the aircraft to "hear" that AIRWAYS marker.  That's what "High Sensitivity" or Hi Sens does.  (To be technically correct, that setting of the switch REMOVES an attenuator from the input signal path in the receiver thus producing what *appears to be* a higher sensitivity.  In fact the receiver sensitivity is fixed, but that switch allows you to VARY it between full sensitivity and less sensitivity.) 

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You can still find AIRWAYS markers (fan markers) on many VORs in the U.S., but operationally few pilots use them anymore since DME is a better position fixing method.  But they're there, and still required by the regs, so I'd leave them intact.  The "normal" position for marker sens is "Low", because that is the setting you should use during an ILS approach.  In the Primus 1000 system it's possible to strap the marker sens either high or low permanently.  Operationally, some operators have done this so that crews have "one less thing to configure" during an approach.  If you do that to an existing aircraft, you'll usually see that the Hi/Lo switch selection has been taped over with opaque gray tape.

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"DonnyRay, why is that Hi/Lo thingy located on the AUDIO panel since it only controls the sensitivity of a remote receiver?"  Because ya' gotta put that switch somewhere, and Honeywell decided to put it on the audio panel.  If you look at other aircraft cockpit photos carefully you'll often find that Hi/Lo switch mounted next to the marker annunciator LAMPS.  But there is no separate marker lamp panel on the L40/45 and they had to put the switch somewhere, so it's on the audio panel in the Primus 1000 suite.  It does not CONTROL the marker AUDIO, but it will AFFECT the received audio volume to a degree.  A separate switch/knob on the AV-850A CONTROLS the marker receiver AUDIO level.

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It's worth noting that airway markers are still used in Europe and 3rd world parts of the world where navaids are sparse.  Those operators fly under different regs than we do in the U.S., so I'd leave the Hi/Lo intact for those builders.

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I have a matched set of AV-850As out of a Lear 40 and they both say "COM1" and "COM2".  So they do exist, but that's not the usual terminology.  "COM" is generic.  It does not inherently refer to any particular aircraft radio.  If you have an AV-850A that's labeled "COM1, COM2, and COM3", which one is the HF radio?  You might GUESS that it's COM3 (and you'd usually be right with that guess) but there's no agreed upon definition for "COM" beyond "communication radio".  On the other hand, "VHF1" tells you that is a VHF radio, and every pilot should know that the radios upon which he talks to tower and ATC are VHF radios.  Thus VHF1 and VHF2 inherently suggest the purpose of those radios.  So does "HF" to an even more precise degree.  Some L45XRs actually have a COM3 radio. 

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The L45s configured for air ambulance service have a radio system for talking to the hospitals they serve.  It's on the COM3 knobs, but is usually labeled "FM" or "EMS" or something similar.  L45s used in law-enforcement activities also have additional purpose-specific radios installed in the center pedestal.  AV-850As don't have extra knobs for those, but they do have extra audio INPUTS that can be used to get the audio into the crew headsets.  So - once again, it's up to the aircraft owner/operator as to how these radios are installed and used.  Personally I prefer "VHF1" "VHF2" and "HF" in L45-1001, but my AV-850As are labeled with "Com" so I guess I'll fly with that.

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(End of DonnyRay Jones insert)

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Great information that will help guide us in the right direction during ACP development.  Thanks DonnyRay! In the meantime, you can find the Project45 Audio Control Panel DXF for the front light plate HERE