Cessna Stationair/Turbo Stationair 6
Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 55; Flight Crew Total 1340; Flight Crew Type 222
Workload; Situational Awareness; Training / Qualification; Human-Machine Interface; Communication Breakdown
Aircraft Equipment Problem Less Severe; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors
While maneuvering on a training flight operated under VFR with two pilots on board: Pilot flying and pilot not flying. I was the pilot flying. The aircraft was receiving traffic advisories from NorCal Approach. Inadvertently; the radio was switched from the frequency we were supposed to be on to the previous frequency we had been on (both pilots were unaware that this switched occurred). A short time later; we saw an aircraft about 4 miles away and near our altitude. We kept the aircraft in sight and it passed about 300 FT above of our aircraft. Both pilots were confused that no traffic advisory was given by Approach Control. About 5 minutes later; we reported that we were ready to return to our departure airport and ATC informed us that we were on the incorrect frequency. We returned to the correct frequency and ATC informed us that they issued a traffic alert for that previously discussed aircraft. I am unsure how the frequency was switched; however; I believe one pilot accidentally hit the COM switch button (Garmin G530) while adjusting the volume on the unit. More attention to detail can prevent this from occurring in the future. It is important to verify that the correct frequency is in the active window; especially after adjusting something on the G530. Also; having the com switch button redesigned by moving it to a safer location or set deeper into the unit for protection might aid to prevent inadvertently switching the COMs.
Two C206 pilots conducting training discovered that the NoCal Approach frequency was switched on their Garmin G530; but they did not discover the switch until after a near miss.