RTU and COM1 connections
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Just updated to 1.1 to see if this behaviour changed from the initial release, but no change.
When you turn on the battery the two RTU's both turn on which makes sense. What doesn't make sense to me, is why the actual radio is not turned on together with it.
What purpose does it serve to use precious battery power to light up RTU's displaying frequencies that you can't actually talk on because the underlying radio is not turned on?To me it makes sense to turn on radios on BAT tp allow for operations with no GPU by having the radio come on as part of the most basic equipment so you can get a startup clearance and start powering up more stuff once you have things going.
The schematics show that the RTU's are on the center bus where COM1 is on the triple fed bus with seemingly loadshedding preventing it from turning on as far as I can tell?Even turning on external power and the EICAS does not give power on the Pilot Tripple fed avionics. It only comes on with the pilot avionics.
Nothing outside the tablet reveals that the underlying radio isn't on, and I feel this would be a very weird design choice IRL. The Starship is full of weird choices though so who knows!Here a pic with battery external and EICAS all on. No indication on the RTU that radios are not actually operating and the manual doesn't mention this as a quirk on the RTU section.
No breaker popped and only used legacy mouse interaction to turn stuff on. No hardware binds I could imagine messing with things. Both ingame ATC and Vpilot sees the radio as not on when COM1 is not powered like this.
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Indeed, that is a rather interesting point. It's also a great example of how I can miss the forest for the trees while developing these aircraft. If I have a schematic that says something, I'm so preoccupied about getting it right that sometimes I don't think about the ramifications.
Looking at the schematics with a more enlightened eye...
The hookups for the RTU's seem to be correct, so the question is about the COM transceivers...
Well, the schematic is very clear that the COM 1 transceiver is off the Avionics No. 2 Power Relay from the Triple-Fed Avionics Bus Feeder No. 1. The avionics distribution schematic also makes it pretty clear that there is only one path for continuity to the Pilot's Triple-Fed avionics bus, and that it's relay is only pulled down when the normally open Pilot's Avionics Switch is closed (the opposite of how a King Air is wired).
I can't find any mention of "ground comm" (other than the one for communicating with ground crew), or anything related to RTU power in any of the manuals.
I completely agree with your assessment of the utility, or lack thereof, in this design, but I can also only tell you what it says in the schematic. I think this might be thoroughly in the "ask the owner" category.
The final level of investigation is looking at the "big boy" schematics in the maintenance manual. Standby...
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Maybe the schematics in the manuals aren't even complete. They never expected nerds of this level
Started looking at that old 600 page manual floating around but of course it is tough to fully read and understand without having a full understanding of all the bus-es and their naming first.
I note that "No.1 +28-V dc power is applied to the RTU power supply"
And for VHF 1 "Operating power is provided by the no.1 +28V dc aircraft supply"
In the Schematics both are listed as NO.1 +28 V DC POWER
Not entirely sure which 28 V bus that is, but it looks to be the same from my cursory overview.Similarly the RTU2 and COM2 looks to be powered by the NO. 2 +28V DC POWER.
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S Sunake referenced this topic
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Indeed, that is a rather interesting point. It's also a great example of how I can miss the forest for the trees while developing these aircraft. If I have a schematic that says something, I'm so preoccupied about getting it right that sometimes I don't think about the ramifications.
Looking at the schematics with a more enlightened eye...
The hookups for the RTU's seem to be correct, so the question is about the COM transceivers...
Well, the schematic is very clear that the COM 1 transceiver is off the Avionics No. 2 Power Relay from the Triple-Fed Avionics Bus Feeder No. 1. The avionics distribution schematic also makes it pretty clear that there is only one path for continuity to the Pilot's Triple-Fed avionics bus, and that it's relay is only pulled down when the normally open Pilot's Avionics Switch is closed (the opposite of how a King Air is wired).
I can't find any mention of "ground comm" (other than the one for communicating with ground crew), or anything related to RTU power in any of the manuals.
I completely agree with your assessment of the utility, or lack thereof, in this design, but I can also only tell you what it says in the schematic. I think this might be thoroughly in the "ask the owner" category.
The final level of investigation is looking at the "big boy" schematics in the maintenance manual. Standby...
@Black-Square said in RTU and COM1 connections:
I can't find any mention of "ground comm" (other than the one for communicating with ground crew), or anything related to RTU power in any of the manuals.
You're going to have to trust me on this - as the GND COMM stuff is in the Collins specific Chapt 23 wiring manuals - and the wiring diagram was furnished individually with each aircraft. Perhaps Raj can share a scan of one for yeah. The GND COMM switch has nothing to do with ground crew intercom option.
It powers the #1 RTU, #1 VHF com, and the audio amplifier and panel, through a relay, off the battery bus - with the main battery switch selected off.
The purpose of this is to get ATC clearance and such without powering up the whole aircraft, and wasting precious battery.
This is identical to its function on King Airs and 1900s.
So basically with it on, you should see the RTU power up, Com1 stuff avail.
Patrick
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Maybe the schematics in the manuals aren't even complete. They never expected nerds of this level
Started looking at that old 600 page manual floating around but of course it is tough to fully read and understand without having a full understanding of all the bus-es and their naming first.
I note that "No.1 +28-V dc power is applied to the RTU power supply"
And for VHF 1 "Operating power is provided by the no.1 +28V dc aircraft supply"
In the Schematics both are listed as NO.1 +28 V DC POWER
Not entirely sure which 28 V bus that is, but it looks to be the same from my cursory overview.Similarly the RTU2 and COM2 looks to be powered by the NO. 2 +28V DC POWER.
Careful reading too much into that Collins Systems manual.
The "No.1 +28 V DC Power" does not mean any specific aircraft bus. It is simply a Collins descriptor for the actual Pin on the tray where the power would come from to power that component, transciever, etc.
Every aircraft (indeed every Beech Aircraft) of that era was furnished with an airframe specific avionics wiring book that would correspond to the avionics installation and correspond with the airframe side of the wiring diagrams found in the airframe Wiring Diagram Manual.
The aircraft has 3 Avionics Feeder Buses. Without those specific wiring diagrams it's hard to tell what is exactly powered by what.
For a simplified overview you can browse the aircraft POH and look at page 3-43.
Patrick
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Indeed, that is a rather interesting point. It's also a great example of how I can miss the forest for the trees while developing these aircraft. If I have a schematic that says something, I'm so preoccupied about getting it right that sometimes I don't think about the ramifications.
Looking at the schematics with a more enlightened eye...
The hookups for the RTU's seem to be correct, so the question is about the COM transceivers...
Well, the schematic is very clear that the COM 1 transceiver is off the Avionics No. 2 Power Relay from the Triple-Fed Avionics Bus Feeder No. 1. The avionics distribution schematic also makes it pretty clear that there is only one path for continuity to the Pilot's Triple-Fed avionics bus, and that it's relay is only pulled down when the normally open Pilot's Avionics Switch is closed (the opposite of how a King Air is wired).
I can't find any mention of "ground comm" (other than the one for communicating with ground crew), or anything related to RTU power in any of the manuals.
I completely agree with your assessment of the utility, or lack thereof, in this design, but I can also only tell you what it says in the schematic. I think this might be thoroughly in the "ask the owner" category.
The final level of investigation is looking at the "big boy" schematics in the maintenance manual. Standby...
@Black-Square said in RTU and COM1 connections:
Well, the schematic is very clear that the COM 1 transceiver is off the Avionics No. 2 Power Relay from the Triple-Fed Avionics Bus Feeder No. 1. The avionics distribution schematic also makes it pretty clear that there is only one path for continuity to the Pilot's Triple-Fed avionics bus, and that it's relay is only pulled down when the normally open Pilot's Avionics Switch is closed (the opposite of how a King Air is wired).
Sorry for the repeat of posts here. Just excited
I'm not sure where you were seeing that behaivour, It should be identical to how a King Air/1900 is - unless i'm misinterpreting what you were saying.
Here, it's pretty clear the avionics relays only energize, with the respective pilot/copilot avionics switch set in the 'off'/closed position. Therefore opening the avionics feeder buses from their respective L/R/C/TPL DC buses.
Patrick
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@Black-Square said in RTU and COM1 connections:
Well, the schematic is very clear that the COM 1 transceiver is off the Avionics No. 2 Power Relay from the Triple-Fed Avionics Bus Feeder No. 1. The avionics distribution schematic also makes it pretty clear that there is only one path for continuity to the Pilot's Triple-Fed avionics bus, and that it's relay is only pulled down when the normally open Pilot's Avionics Switch is closed (the opposite of how a King Air is wired).
Sorry for the repeat of posts here. Just excited
I'm not sure where you were seeing that behaivour, It should be identical to how a King Air/1900 is - unless i'm misinterpreting what you were saying.
Here, it's pretty clear the avionics relays only energize, with the respective pilot/copilot avionics switch set in the 'off'/closed position. Therefore opening the avionics feeder buses from their respective L/R/C/TPL DC buses.
Patrick
@plhought How interesting that the ground comm functionality evaded me (and all the descriptive manuals, from what I could see), despite how many details I have learned about this aircraft. You are also correct about the avionics relays functioning the same as a King Air. I was also looking at section 24-56-00 in the wiring diagram manual, but my rush to answer before Flight Sim Expo must have gotten the better of me.
I will add the ground comm functionality immediately. Do you have a page/section in the wiring diagram manual for the ground comm switch? I would assume that the master battery switch also closes the same connection between the RTU1 + COM1 transceiver and the hot battery bus, such that the ground comm switch could be released after the battery is connected, and the RTU1 + COM1 will remain energized.
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@plhought How interesting that the ground comm functionality evaded me (and all the descriptive manuals, from what I could see), despite how many details I have learned about this aircraft. You are also correct about the avionics relays functioning the same as a King Air. I was also looking at section 24-56-00 in the wiring diagram manual, but my rush to answer before Flight Sim Expo must have gotten the better of me.
I will add the ground comm functionality immediately. Do you have a page/section in the wiring diagram manual for the ground comm switch? I would assume that the master battery switch also closes the same connection between the RTU1 + COM1 transceiver and the hot battery bus, such that the ground comm switch could be released after the battery is connected, and the RTU1 + COM1 will remain energized.
@Black-Square Unfortunately I have no drawing available for the Gnd Comm. Those wiring drawings were unique to each airplane and provided seperately in hard copy for each airplane. You'd have to reach out to an owner to try and get the set. The drawings are numbered with a 129-34xxxxx dwg no.
I've moved on from my previous employer where I could grab an example from 1900 wiring set, so don't have a specific example available.
But the behaviour you describe with power applied with the switch still seems correct, although I'd maybe be something you'd have to ask an owner, because my gut isn't sure if the vhf com 1 box is powered just with the battery on?
