Narrative:

While being vectored for the ILS 10R approach in VMC conditions, I instructed the student to set up portland tower frequency in the unused communication radio. During this time I was looking for traffic that ATC had reported. Our vector at the time was a downwind vector for the ILS. After several mins I thought ATC had forgotten about us and I was about to call when we received a call to make an immediate turn (this was probably for terrain that was to our 1 O'clock and 2-3 mi). At this time, ATC told us to contact approach control and this is when I realized my student had put tower frequency on the communication radio being used instead of the standby radio. Approach control said that they had been trying to get a hold of us. We got vectors for the approach and went uneventful.

Related reports:

Google
 

Original NASA ASRS Text

Title: GA SMA ACFT ON IFR TRAINING FLT LOST COM WITH APCH CTL DURING APCH WHEN THE STUDENT INADVERTENTLY RESET THE RADIO IN USE TO THE TWR INSTEAD OF 'IN THE STANDBY RADIO.'

Narrative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

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.