See and avoid

 

A recent mid-air collision between two aircraft near the Corona airport southeast of Los Angeles brings to light the way in which pilots seek to avoid collisions. The primary rule that governs pilot responsibility for collision avoidance is within the Code of Federal Regulations Part 91.113.

The rule states in part, “When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft.” The concept of “see and avoid” puts the responsibility of separation between aircraft squarely on the shoulders of the pilot in command of each aircraft.

In the case of the two aircraft involved in the Corona incident, both were operating on a clear day, visibility was excellent with no clouds to obstruct vision, and both were in the immediate vicinity of an airport without a control tower. The aircraft involved were both single engine Cessna’s with wings above the fuselage.

 

Most mid-air collisions occur in the vicinity of airports without control towers, otherwise known as uncontrolled airports, between aircraft during the take-off or landing phase of flight. Aircraft are converging near airports during this time and as their proximity to each other increases so does the chance of collision. Pilots are trained to maintain a higher level of vigilance during this phase of flight by following good operating procedures.

The first and foremost operating procedure that pilots must follow is a good scan of the airspace. Dividing the visible airspace into sections and scanning that section keeps the pilot’s attention outside the cockpit and directed towards possible targets he is responsible for seeing and avoiding. The pilots flying these two Cessna’s had the wing of the aircraft over their heads and possibly obstructing a view of the other aircraft as it approached.

 

A pilot who contacts air traffic control may have available to him services that allow the controller to identify his aircraft on radar and advise him of other aircraft in the vicinity. This service is not always available to pilots operating visually, as the service is provided on a controller workload basis. If the controller is too busy assisting aircraft on instrument flight plans, the workload may preclude assisting those pilots operating visually. Still, a flight plan is no guarantee that traffic will be announced by a controller, and the pilot is still responsible to “see and avoid” another aircraft while operating in visual conditions.

A common scenario of a mid-air collision is a high wing aircraft approaching an airport at a lower altitude at the same time as a low wing aircraft approaches from a higher altitude. The view of the high wing aircraft is blocked in an upwards direction and the view of the low wing aircraft is blocked in a downward direction. Pilots must maneuver their aircraft during approaches to “clear” those areas visually blocked by parts of the aircraft structure.

 

A good radio announcement of an aircraft’s position is another procedure that pilots should use to keep other aircraft in the vicinity appraised of their position. Uncontrolled airfields have published radio frequencies that pilots are able to access that allow two way communications between aircraft. Pilots should announce their position and altitude at least 10 miles out, stating their intentions during the approach and landing. Additional announcements are made as the aircraft approaches and during the entry into the landing pattern. Aircraft on the ground monitor these transmissions and make their own announcements of their movement on the ground, when they take the runway for takeoff, and their intentions during the departure phase of flight.

Landing patterns at an airport are published and available to pilots from a number of sources. Airport facility directories contain complete information on airports including radio frequencies, traffic patterns, and ground facilities. Pilots are required by regulation to become familiar with information on airports at which they intend to land. Aeronautical charts that pilots are required to have on board during a flight have information on traffic patterns, frequencies, and airport elevation that a pilot must consult before an approach to the airport.

 

Traffic patterns for an airport also are indicated and visible from above the airport by a segmented circle. This pattern, laid out on the ground and generally surrounding the airport windsock, is identified by a circle of white segments with “L” shaped extensions. The extensions indicate the direction that an aircraft should approach the corresponding runway using right or left hand turns during the landing approach.

General aviation travel remains one of the safest methods of travel, second only to airline travel. The National Transportation Safety Board compiles data on fatalities in the transportation industry. During 2005, the latest year for which data has been published, the NTSB reported that 40 fatalities occurred in airline travel in the U.S. During that same year 792 people died in boating or marine accidents, 760 in railroad accidents, and nearly 43,000 in highway or automobile accidents. During this same period 632 people died in general aviation accidents.

 

In view of this statistical data, it is no wonder why pilots understand that the most dangerous part of a flight is the drive to the airport.