JAGflyer From Canada, joined Aug 2004, 3444 posts, RR: 4 Posted (1 year 1 month 2 weeks 21 hours ago) and read 1688 times:
Everyone here loves the "Channel 9" option on the UA and now CO fleet. For those who do not know, Channel 9 is a direct broadcast of the active ATC channel from the cockpit. My question is how does this system work and how does the pilot turn Channel 9 off (nothing to hear) or on? From what I would imagine, the Channel 9 output is controlled the same way the pilot would broadcast VHF/HF audio to either the cockpit speakers, boom mic headset (when using the oxygen mask) or to their headset. Is one of the knobs on the audio panel used to control if Channel 9 is working? Can one of the UA pilots or mechanics explain the technical aspect of the system?
Here is an audio panel from a 737. When you want to allow audio from the respective radio to be heard you can push the knob and it'll pop up. You turn it left or right to adjust the volume. The SPKR is selected when you wish to remove your headset and still hear the audio over the cockpit speakers. The MIC SEL panel selects which radio you are transmitting on (you may listen to multiple radios but you can only transmit on one at a time). Selecting PA is what will allow the pilot to make announcements to the cabin. FLT is for speaking to FAs on the cabin interphone and SVC is for the "cockpit to ground" communication via the service panel (used during pushback).
[Edited 2013-01-22 19:04:26]
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apodino From United States of America, joined Apr 2005, 4096 posts, RR: 6
Reply 3, posted (1 year 1 month 2 weeks 7 hours ago) and read 1577 times:
Quoting JAGflyer (Reply 2): Would that not mean the conversations via the flight interphone would be broadcast on Channel 9 as well? "Betty, we need more ice and peanuts back here".
No because on the audio panel you select what is actually heard. Notice the Flt and Svc are up...meaning they aren't being listened to. In this example, only VHF radio 1 is selected to be heard, and VHF 1 is usually the one they talk to ATC on though this can change. For example, I flew into LGA during the Subway Strike one time and the captain turned on a local NY AM station on the ADF and selected the ADF on instead of the VHF so we could listen to radio coverage of the event.
Also...there are other planes that have the OBS Audio entertainment switch. This is what allows the audio panel to pipe into channel 9. If it is selected off, a jumpseater can still listen using the Audio panel, but it won't be heard in the back on Channel 9. When I have jumpseated, the pilots have reminded me to be careful with my audio panel for that very reason.