The EMS helicopter was returning to Shenandoah Valley Regional Airport in Virginia, having dropped off a patient in nearby Charlottesville. Reports differ on whether the Cessna was departing the airport or returning to the airport for landing. The Cessna and the helicopter collided. Though the helicopter landed safely, both occupants in the Cessna were killed.
No Control Tower
There’s no control tower at Shenandoah Airport. The primary means of preventing collisions at airports like Shenandoah is called “see and avoid.” That means that pilots are supposed to look out their windows, see other aircraft, and avoid them.
Helicopters and Airplanes Don’t Mix Well
Though the "see and avoid" method may sound primitive, over the years it has worked well, and mid air collisions are relatively rare. But helicopters don’t mix well with airplanes in a "see and avoid" environment. Helicopters tend to fly slower than airplanes and, because they have a small cross section, they are hard for airplanes to spot — especially when viewed from directly behind.
Because of that, when near an uncontrolled airport, helicopter pilots are supposed to "avoid the flow" of airplane traffic. In other words, as best they can, helicopters are supposed to stay out of the way of airplanes. Sometimes that’s easy enough. For example, if the airplane traffic flies on one side of the airport (see below), the helicopters generally should fly on the other side. Or, the helicopter can fly at an altitude that is lower than the altitude at which the airplanes are flying.
The above diagram depicts a left-hand traffic pattern for fixed-wing (airplane) traffic similar to the pattern used at Shenandoah Airport. Airplanes typically fly the traffic pattern at 1000 feet. To avoid the flow of that traffic, helicopters might fly a right-hand traffic pattern on the other side of the runway, and fly no higher than 500 feet.
One question will be whether the Cessna was operating within the "flow" of fixed wing traffic when the collision occurred and, if so, why the EMS helicopter did not avoid that flow.