VHF preset not loaded after DTE load?
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Hi all,
In our sqn we made a default <callsign>.ini file with sqn default frequencies and some other stuff. We have made some frequency preset changes with WDP and set default UHF to 19 and default VHF to 15.
When checking the .ini file we correctly see
[COMMS] Comm1=19 Comm2=15 ```When in 2D map of a TE, in the DTC window confirms the UHF19 & VHF15 being default (green box default checked). However when doing a cold start, after loading DTE via the MFD's, and switching CNI to UFC, we get UHF19 correct, but VHF always comes up at channel 13. Going commit taxi or fly gives correct VHF15, only loading DTC manual at rampstart gives VHF13 instead. Confirmed by 2 other sqn mates they have the same issue. Any idea?</callsign> -
Try switching CNI to UFC before loading DTC.
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As one of the other 2 squadron mates, I wanted to add this to Faan’s words:
Actually, the problem is easily fixed by loading the DTC a second time (it then sets both UHF and VHF to the correct default channels), but I don’t think it’s normal we have to do it twice to get it working the way we want it to.
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It only works if COM2 is on and CNI is set UFC before you do the load sequence. If the COM2 is turned on after and/or CNI was in B/U then VHF radio wasn’t paying attention during the load kick to preferred channel.
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If you follow the checklists:
BEFORE ENGINE START
Step 9 COM 1 & 2 Vol knob Set both CW (turns radio ON)
then . . .
AFTER ENGINE START (Continued)
Step 6 CNI (C&I) knob: UFC
Step 7 DTC: Load (always load the DTC prior to setting up the UFC subpages)
Step 8 UFC radio: Set COM1 & COM2 frequency as briefed.If your VHF radio does not come up on preset 15 after the DTC load, you can set it as desired in Step 8.
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Manual bms 4.33 pag. 14-230: automátic DTC load happen at taxi or takeoff.
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Thx guys, seems I need to recheck the checklists. We are basing ourselves on real life checklists and I have 3 versions. Two also sets C&I to UFC before DTC load, the other loads DTC first and only laters switches on UFC & COM2. Either some logic has changed over the years, or even real lists can have a mistake.
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Either some logic has changed over the years, or even real lists can have a mistake.
Oh, yes, T.O.s and checklists are routinely updated/corrected.
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I doubt that the real VHF radio initializes to channel preset 13 like in BMS in absence of DTC info. That would be odd. As far as I can tell the default channel/freq feature with DTC in BMS is possibly fictitious.
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Thx guys, seems I need to recheck the checklists. We are basing ourselves on real life checklists and I have 3 versions. Two also sets C&I to UFC before DTC load, the other loads DTC first and only laters switches on UFC & COM2. Either some logic has changed over the years, or even real lists can have a mistake.
It still works good in 4.33. I do full ramp starts all the time and what SLangner/Frederf said is right on. VHF off and CNI to UFC won’t work. VHF on and CNI to B/U won’t work. VHF on and CNI to UFC and DTC loads swap the channels per the defaults saved in 2D just fine.
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It still works good in 4.33. I do full ramp starts all the time and what SLangner/Frederf said is right on. VHF off and CNI to UFC won’t work. VHF on and CNI to B/U won’t work. VHF on and CNI to UFC and DTC loads swap the channels per the defaults saved in 2D just fine.
I know, I do aprox 5 ramp starts a week in BMS.
As said, we recently switched to a custom checklist based on real life checklist and one of three real ones had C&I in BU when DTE is loaded, and that was copied into our list, since then we had this issue.
So, problem solved. VHF needs to be ON and CNI in UFC before loading DTC.
Weird though it has to be in UFC already. DTC data can be loaded into the computer, wether the CNI knob is in UFC or BU. When you are in UFC and have a custom freq/chan set, go to CNI BU, and then return to UFC, the previously set freq isn’t lost either normally. It’s just a preset saved into UFC-computer. UFC is powered with the UFC switch on the avionics power panel, not the CNI knob. -
It’s just a preset saved into UFC-computer.
The computer running the UFC is called the DEEU/XDEEU etc. Atleast in block 25-42s.
UFC is powered with the UFC switch on the avionics power panel, not the CNI knob.
Yeah I know I worked the aircraft for 19 years. I know how the system turns on.
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The computer running the UFC is called the DEEU/XDEEU etc. Atleast in block 25-42s.
Yeah I know I worked the aircraft for 19 years. I know how the system turns on.
Cool.
Do you recall what the default uhf/vhf channels are when booted if no dtc is loaded? What was set previous flight, or a default for the computer? -
Double post
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Cool.
Do you recall what the default uhf/vhf channels are when booted if no dtc is loaded? What was set previous flight, or a default for the computer?This is the problem I have of being retired. Questions like this never came up for the real aircraft. I looked through my CDCs and through the 34-1-1 but neither addresses these particular questions (DTC load fail if in CNI B/U and UFC channels on start up) directly. They do talk about a few limitations for DTC loading but the CNI switch was never mentioned as a factor so my educated guess would be that is an artificial BMS limitation and not a real aircraft one. Thankfully the work around is easy to put into play. As far as BMS is concerned for the UFC it really is academic if the real aircraft loads the default or is still set to the last stations as BMS doesn’t track aircraft that way hence no way for it to know what to set it to other than default channels.
IIRC during the SFM we would set the CNI switch to UFC prior to spinning up the aircraft and would only put it in backup if needed for a specific test of a fault. I don’t ever recall that happening so any checks I would have made with the DTE system would have been in UFC anyways. We never turned on systems that we didn’t need to check or use to check another broken system so all of my DTC loading would also have been done with UHF and VHF radios off and I don’t recall the DTE ever complaining about having an error loading comms. That being said I also never knew what was programmed into the DTC (we would just borrow one from ops. As long as it was programmed with something it fit our testing needs) and never turned on the radios to attempt to verify anything there. Wasn’t required per the T.O.s.
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A bit of theorizing on this point.
F-16 (at least the kind modeled) would have some kind of AN/ARC-186 VHF and AN/ARC-164 VHF radio, relatively standardized pieces of equipment. Normally the 186 consists of a finger-touchable human interface panel box RT-1354 connected via cable to the RT-/CM- part number radio in the avionics bay (there are several, let’s say RT-1300). Instead the UFC set plugs into the same 20+ pin connector socket that the normal radio control head (the box with the faceplate you touch) to replicate that data stream.
When the DTC is loaded by the DTE, is the file (and they call them files) loaded straight into the ARC-186, failing if it isn’t on? I doubt it. I bet there is some MMC or UFC memory where that radio channel data is loaded which doesn’t require the box in the avionics bay to be on at all. There is some mention of a “UFC battery” as well.
My guess is that the data plugged into the avionics bay box is strictly frequencies (no channels) and that it is the control head (UFC/MMC in F-16) that has understanding of channel preset-frequency table. So the jet is loaded with ch1 = XXX.XX Mhz, ch2 = YYY.YY Mhz, and so on. When it comes times to tune the radio the electronic tickle down the cable into the avionics bay is just “tune XXX.XX Mhz.”
I’m also guessing that the VHF radio would still be tuned to the last frequency set on the last flight similar to how when you CNI BUP you can still key VHF because it’s tuned but you have no control over future frequency changes. Unless UFC initializes the VHF to some frequency every time it’s powered on (and why ch13 of all things?) or perhaps the VHF memory is volatile and it isn’t tuned at all at initialization.
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When the DTC is loaded by the DTE, is the file (and they call them files) loaded straight into the ARC-186, failing if it isn’t on? I doubt it. I bet there is some MMC or UFC memory where that radio channel data is loaded which doesn’t require the box in the avionics bay to be on at all. There is some mention of a “UFC battery” as well.
There is no backup control to the VHF radio system and it is controlled strictly through the UFC system so obviously as far as DTC loading is concerned it is going to the UFC system.
The UFC battery is for the scratchpad memory of the DEEU/EXDEEU. It makes the volatile memory (kinda like the RAM in your computer) non-volatile while the battery is connected. That holds all of the information like steerpoints, radio channels, ILS freqs, TCN freqs, etc. between flights.
My guess is that the data plugged into the avionics bay box is strictly frequencies (no channels) and that it is the control head (UFC/MMC in F-16) that has understanding of channel preset-frequency table. So the jet is loaded with ch1 = XXX.XX Mhz, ch2 = YYY.YY Mhz, and so on. When it comes times to tune the radio the electronic tickle down the cable into the avionics bay is just “tune XXX.XX Mhz.”
Yes the radios only need to be told what to tune to. The channel number is irrelevant to the radio itself. The MMC isn’t really getting involved in radio tuning. That would be the UFC alone for VHF or the UFC or the UHF radio head for UHF comms.
Although this is an aside the DEEU is in the cockpit right behind the ejection seat so for UHF comms all of the controlling happens right there in the cockpit and not in an avionics bay.
I’m also guessing that the VHF radio would still be tuned to the last frequency set on the last flight similar to how when you CNI BUP you can still key VHF because it’s tuned but you have no control over future frequency changes. Unless UFC initializes the VHF to some frequency every time it’s powered on (and why ch13 of all things?) or perhaps the VHF memory is volatile and it isn’t tuned at all at initialization.
The UFC would be the controller of the VHF and tell it what to tune to. Yet another case of something I don’t have an exact answer for as no one ever tries to turn on the aircraft except for the UFC and then tries to transmit on VHF to see what happens.
