RF Quiet/Silent Switch Too Restrictive?

[Frederf]

From what I’m reading the BMS RF Switch is too restrictive. It should be possible to initiate DL rounds, have ACM radar locks, etc. at least in the Quiet mode.

[Dee-Jay]

Run Silent (RF) Switch Operation. The RF switch positions are NORM, QUIET, and SILENT. The switch controls
transmissions from the following subsystems:

FCR (Fire Control Radar)
CARA (Combined Altitude Radar Altimeter)
IFF (Identification Friend or Foe)
TACAN (Tactical Air Navigation)
ECM PODS (Electronic Countermeasures)
IDM (Improved Data Modem)
MIDS (Multifunctional Information Distribution System)
ATD (Advanced Towed Decoy).

Status of the RF switch, QUIET or SILENT, is displayed on both MFDs on all pages except for the TEST format
and the SMS BIT page. No status is displayed when set to NORM. NO RAD is also displayed in the HUD when the FCR is not
radiating.

NOTE
When RF switch is placed from NORM to QUIET or SILENT, and the ECM ENBL light is on (transmit consent
via CMS aft), the MMC will remove transmit consent and the ECM ENBL will go out. If the consent switch is
subsequently activated (i.e., CMS aft again) and RF switch is in QUIET or SILENT (ECM ENBL light off), the
ECM ENBL illuminates and the ECM pod is activated. The consent (CMS) switch overrides any RF switch
position. The RF switch must be moved back to NORM then to QUIET or SILENT to turn off ECM ENBL.

When the RF switch is in NORM, all subsystems operate normally. When the RF switch is placed in the QUIET
position, the FCR, IFF, TACAN, ATD, and ECM pod (if enabled) do not transmit. When the RF switch is placed in the SILENT
position, the FCR, IFF, TACAN, CARA, ATD, IDM, ECM pod (if enabled), and MIDS do not transmit. Each subsystem returns
to the last selected mode when switched from QUIET or SILENT to NORM.

When the RF switch is positioned to NORM, automatic acknowledgement of a received data link message and data
link transmissions can be enabled or disabled. When the RF switch is positioned to QUIET or SILENT, automatic acknowledgement
is automatically disabled. Refer to DATA LINK INITIALIZATION MANAGEMENT (1.31.2) for additional
information.

All ECM systems are inhibited when the RF switch is moved from NORM to either QUIET or SILENT. The ECM
systems are not affected by any other RF switch actions and may be re-enabled via the CMS switch regardless of the RF switch
position. The XMIT OSB (16) on the ECM page provides consent to the ATD regardless of the RF switch position.

[l3crusader]

DJ, from what I read, the IDM can be emitting on Quiet mode. In BMS, it does not. So OP has a point on this.

For ACM radar locks, if the FCR cannot emit, I dont see how that is possible.

[Dee-Jay]

… no time to study it, just posted what I’ve found.

but yep … looks like IDM should work under QUIET operation.

• When the RF switch is placed in the QUIET position, the FCR, IFF, TACAN, ATD, and ECM pod (if enabled) do not transmit.
• When the RF switch is placed in the SILENT position, the FCR, IFF, TACAN, CARA, ATD, IDM, ECM pod (if enabled).

[Eagle-Eye]

@l3crusader:

For ACM radar locks, if the FCR cannot emit, I dont see how that is possible.

Perhaps an IDM feature that allows to track a received target? Then, once the target is within kill distance, the FCR is enabled and already looking in the right spot for a quick shot. Maybe even a firing solution without need to enable own FCR, but relaying all received data to the AIM?

Just guessing, though… Could just as well be miles from the truth.

[Blu3wolf]

@Eagle-Eye:

Perhaps an IDM feature that allows to track a received target? Then, once the target is within kill distance, the FCR is enabled and already looking in the right spot for a quick shot. Maybe even a firing solution without need to enable own FCR, but relaying all received data to the AIM?

Just guessing, though… Could just as well be miles from the truth.

this discussion has come up several times before… L-16 tracks to not have enough data to fire an AIM-120 - whilst in theory all the needed stuff is there, in practice the software is not in place to shoot unless through the FCR (maybe this has changed on new tapes?)

[caper]

:munch:
<waiting to=“” be=“” amazed=“” when=“” the=“” op=“” reveals=“” his=“” source=“”></waiting>

[Blu3wolf]

@caper:

:munch:
<waiting to=“” be=“” amazed=“” when=“” the=“” op=“” reveals=“” his=“” source=“”></waiting>

probably a -34-1-1 Im guessing.

[Frederf]

@l3crusader:

DJ, from what I read, the IDM can be emitting on Quiet mode. In BMS, it does not. So OP has a point on this.

For ACM radar locks, if the FCR cannot emit, I dont see how that is possible.

It’s because RF switch position is a pilot preference, not a physical disconnection.

RF Switch
The RF switch, often called the “run silent” switch, is located at the inboard portion of the HMD/RF
Control Panel immediately below the EWMU. The switch was added to the MLU aircraft to provide the pilot
with a single point aircraft emissions control capability. In NORM, RF emitters such as the FCR, CARA,
TACAN, IDM, Jammer Pods, and AIFF operate normally. However, when QUIET or SILENT is selected,
the emitter operation is modified as depicted in Table 7-1. In addition, the RF switch status, QUIET or
SILENT, is displayed on all MFD pages except TEST and SMS BIT.
Table 7-1 RF Switch Functionality
NOTE 1: NO RAD is displayed in the HUD when the FCR is in a non-radiating mode. The FCR, which
normally does not transmit in QUIET, will transmit under the following conditions:
• If there is a bugged target in any A-A mode except TWS when QUIET is selected, the
bugged target will continue to be tracked. During the search portion of the scan, the FCR
goes silent and passively detects other RF sources through the receiver.
RF SWITCH POSITION
RF SYSTEM NORM QUIET SILENT
FCR Transmits
Conditionally
Transmits–-Note 1
Conditionally
Transmits—Note 2
CARA Transmits Transmits Transmits
TACAN Transmits Does Not Transmit Does Not Transmit
AIFF
TRANSPONDER
Transmits Does Not Transmit Does Not Transmit
AIFF INTG.
Transmits On Pilot
Command Only
Transmits On Pilot
Command Only
Transmits On Pilot
Command Only
IDM DEMAND
and ASSIGN
Transmits On Pilot
Command Only
Transmits On Pilot
Command Only
Transmits On Pilot
Command Only
IDM CONT.
Normal Continuous
Transmissions On
Pilot Command
Completes
Transmission of
Continuous Round
in Progress—Note 3
Completes
Transmission of
Continuous Round
in Progress—Note 3
ECM PODS
Transmits
Conditionally
Transmits—Note 4
Conditionally
Transmits—Note 4
16PR14341
210
• If there is a FTT ground target in an FCR A-G mode when QUIET is selected, the ground
target will continue to be tracked.
• If an ACM submode is commanded (TMS-right).
• If ACM is exited with a bugged target, the bugged target will be retained.
NOTE 2: NO RAD is displayed in the HUD when the FCR is in a non-radiating mode. The FCR, which
normally does not transmit in SILENT, will transmit under the following conditions:
• If an ACM submode is commanded (TMS-right).
• If ACM is exited with a bugged target, the bugged target will be retained.
NOTE 3: If the IDM is transmitting continuous rounds as the switch is moved to QUIET or SILENT, it will
complete the current round in progress and stop transmitting.
NOTE 4: If the ECM pod is transmitting as the switch is moved to QUIET or SILENT, the pod will go to
a non-transmitting state. Placing the CMS aft after entering QUIET or SILENT enables the pod
to continue to transmit.
NOTE 5: When the RF switch is returned to NORM, each subsystem except the IDM and ECM pod returns
to the emissions state that was active just prior to entering QUIET or SILENT. The IDM and
ECM pods will remain in the last emissions state occurring while in SILENT or QUIET.
When the RF switch is returned to NORM, each subsystem except the IDM and ECM pod returns to
the emissions state that was active just prior to entering QUIET or SILENT. The IDM and ECM pods will
remain in the last emissions state occurring while in SILENT or QUIET.

I know it’s from MLU M1 guide which is “old news” but it establishes a pattern and design philosophy unless contradicted.

ACM-One Switch Action To NO-RAD (RDP-626)
The Target Management Switch (TMS) aft (RTS) function was changed as follows:

1. Any ACM radiating submode, TMS aft enters ACM 30x20 NO-RAD.
2. From 30x20 NO-RAD, TMS aft enters ACM 10x60 radiating submode
   TMS aft is the only switch action that commands a break lock from an ACM track mode.
   When ACM is entered and a submode is requested, the FCR will radiate regardless of the
   position of the RF switch. Moving the RF switch from NORM to QUIET or SILENT while in
   ACM has no effect on the radiate state. While the RF switch is in Quiet or Silent, the FCR will
   continue to radiate until you exit ACM without a bugged target.

This is from MLU M2 tape which continues this pattern.

The only difference between QUIET and SILENT in table 7-1 is NOTE 1 vs NOTE 2 which relates to what FCR tracks will remain if entering QUIET or SILENT. In QUIET tracks of any AA mode (except TWS) are retained so all of ACM, RWS, STT, SAM, etc. In SILENT only ACM tracks are allowed. If CARA is inhibited (by Table 7-1 it never is) then it should only be during SILENT and allowed to give radio altimetry in QUIET.

So yes if you put RF Switch into QUIET/SILENT normally things get inhibited… but that doesn’t mean you can’t re-enable some transmissions while the switch is in a quiet position. The event of moving the switch reconfigures things but only at that instant. There is a lot of freedom still after that event. Also CONT IDM when enter silent/quiet state should resume CONT loop if you don’t change anything while in quiet/silent.

[caper]

hmmm, nothing about AG FCR slant ranging for CCIP,DTOS, non-locking CCRP solutions.

[Blu3wolf]

@caper:

hmmm, nothing about AG FCR slant ranging for CCIP,DTOS, non-locking CCRP solutions.

from the table copied, it suggests that you cannot do that in QUIET or SILENT.

[Frederf]

Piecing together the pattern it seems that RF Q/S justifies narrowly focused radar energy (STT, FTT, ACM, the track half of SAM) but not “willy nilly” energy (AGR, GM, GMTI, the search portion of SAM, TWS). If there’s no specific track being used when RF Q/S is selected, it’s inhibited unless commanded otherwise. And the only commands that make sense are using ACM because SAM-track or FTT require having a wide scan picture to select from.

DL rounds can be initiated in RF Q/S but automatic replies aren’t. So if the initiating ship is the only member RF Q/S then the DL is fine because the quiet ship volunteered his data and the others joined in. However if the entire flight is RF Q/S then while any member can initiate a round, no one else will reply and only the initiating member’s info will appear to the passive receivers. At least that appears to be the “old school way.”

In a BLK50/52 document it says RF switch doesn’t inhibit automatic IDM reception acknowledgements, but later it says the RF switch disabled auto ack in Q/S. Such decisions are made by the MSS program from DTC. The automatic acknowledge setting is one of the few that can be changed in the DED page “ACK” setting. I would conclude that DL ACK only happens in RF NORM and ACK enabled are both true.