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Old 09-13-2021, 10:19 AM
Piper J3's Avatar
Piper J3 Piper J3 is online now
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,523
Default Flightcom 403 Intercom Muting…

I bought my RV-12 from original builder six years ago. My plane is an early SN with D180 instrumentation, SL40 Comm, and 403 Intercom.

Recently I have experimented with the Isolate/All switch on the intercom and discovered that radio reception is very much improved in the Isolate switch position. Isolate mutes the intercom so the comm radio does not “hear” cabin noise or passenger talking over radio reception. A little research shows that a set of jumpers can be added to the 25 pin connector on the 403 intercom which will give the comm radio full authority to mute the intercom when transmitting or receiving.

Pins 23, 24, and 25 can all be jumpered together to provide automatic muting. Flightcom ships the 403 with this jumper in place. It appears that Van’s did not replicate this Factory Shipped Muting Configuration when they made the wiring harness for the early legacy RV-12.

I’m in the process now of obtaining pins and D-sub crimping tool to make this change.

Below are screen shots of RV-12 electrical schematic and info from Flightcom Installation Manual.
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 717

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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Old 09-13-2021, 08:37 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,559

What you discovered is an option to make this configuration in flight selectable. There are dip switches on the circuit board inside the intercom that permanently select these functions. This diagram shows how to add wiring to make them in flight selectable.
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
RV-6A (aka "Junkyard Special ")
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