You are flying along in level cruise in fine weather. No traffic in sight, none reported.
Well, there is another aircraft nearby, and its pilot is going to unusual lengths to keep you in sight by extending the climbing portion of the loop the aircraft is flying, then by rolling 90 degrees on the way down to maintain visual contact. And maybe it wasn’t completely accurate to say that there was no reported traffic. The aerobatic pilot was making position reports, but only on the air-to-air frequency, where the locals know to listen for them.
This odd conflict between an en route aircraft and an aerobat came to light for two reasons: One was that the aerobatic pilot wanted to suggest that charts recommend that pilots flying through the area monitor 122.75 MHz . The other reason was because "I possibly encroached on V81 coming less than 4 miles from the center of the airway maneuvering to avoid the other aircraft," the pilot said, describing the event to the Aviation Safety Reporting System.
If your serenity about traffic separation is shaken by the vulnerabilities the event may have revealed, it’s time to refresh on other scenarios where the IFR and VFR worlds may overlap, and where pilot vigilance and situational awareness alone preserve safe margins.
In good weather, some pilots practice instrument approach procedures, or holding, under VFR, perhaps at altitudes below radar contact, without contacting ATC or monitoring the controlling facility. If the flight announces intentions on the common traffic advisory frequency, you will hear it if you happen to be monitoring the CTAF just then.
Still, don’t assume that the VFR pilot is by default the errant party in scenarios where IFR and VFR aircraft are operating simultaneously. Many an instrument pilot has made an IFR arrival at a nontowered airport, usually following a leisurely changeover to the CTAF, only to be rightly excoriated for barging into the beehive against the direction others are flying.
Recall when flying to nontowered airports in low weather that a VFR aircraft could be in the traffic pattern—in Class G airspace—in a mile’s visibility and clear of clouds. That aircraft may not be radio-equipped.
Bottom line: Keep scanning for traffic, and never assume that the fellow flying the loop has you in sight.