Traffic around the Washington area's three major airports is more tightly controlled than it is at San Diego's Lindbergh Field and Washington National Airport, the area'a busiest, receives the tightest controls the Federal Aviation Administration has to offer.
Since those controls were applied at National and the 20 other busiest airports around the country in 1968 there has been only one collision in the air at those airports and it did not involve a commercial airliner.
The controls were established "specifically to reduce the likelihood of a midair collision" said Gene Lawing of the FAA. Similar but less intensive controls are in effect at Dulles International and Baltimore-Washington International airports.
The degree of control and the question of mixing general aviation aircraft with commercial airliners are old issues that are certain to be debated again in the aftermath of the San Diego collision.
General aviation - which includes business jets and small single-engine crop dusters - is an enormous business in the United States. There are about 18,500 general aviation aircraft registered in this country but only about 2,500 commercial airliners.
The biggest problems with all that potential traffic occur around big-city airports. National Airport is located inside what the FAA calls a "terminal control area."
Airplanes that enter such a narea - a clearly defined section of airspace that resembles an upside-down wedding cake - make be equipped with multichannel radios and altitude-reporting devices. A pilot cannot fly through a terminal control area without being in radio contact with controllers.
The altitude - reporting device can cost as much as $2,000 and the radio around $1,200. Those statistics alone keep a lot of small-plane operators out of terminal control areas.
There are additional controls at Washington National that are unique.
National has an hourly quota that theoretically permits a total of 60 takeoffs or landings by all kinds of aircraft. Forty of those slots are allocated to regular airlines: eight slots go to air taxi operations and 12 are given to general aviation. To get into National, planes must have a reservation. The quota is voluntary, however, and is regularly exceeded by general aviation traffic in clear weather.
Another limiting factors is that National charges a higher landing fee than Dulles International. It costs a minimum of $4 to land at National, plus 12 cents per 1,000 pounds for propeller planes and 30 cents per 1,000 pounds for jets. At Dulles, the minimum is 75 cents plus 25 cents per 1,000 pounds for all kinds of planes.
In 1977, there was a total of 345,452 takeoffs or landings at National and three out of four of them were by commercial airliners or air taxis. The rest, 86,388 takeoffs and landings, were by general aviation and military aircraft.
The picture is quite different at Dulles International, where there were a total of 186,391 takeoffs or landings in 1977 and almost three out of five were by general aviation aircraft.
At Baltimore-Washington International, almost half the 242,960 takeoffs and landings in 1977 were by general aviation aircraft.
Both Dulles International and BWI are located within the FAA's second echelon of air traffic control - the "Terminal Radar Service Area" (TRSA). There are 83 such areas in the United States and they include 103 airports.
Less sophisticated radio and navigation equipment is required of the plane that flies into a TRSA and the pilot's participation in the air traffic control system is voluntary, not mandatory.The FAA's Lawying said that "90 percent of the pilots get into the system in a TRSA."
San Diego's Lindbergh Field is not even in a TRSA, despite the fact that it had 205,000 takeoffs and landings in 1977, including 76,694 by commercial airliners. However, nearby Miramar Naval Air Station, where the regional radar control center is located, is in a TRSA. Miramar has heavy jet fighter traffic that must be meshed with the primary north-south flyway along the Pacific Coast, according to Lawing.
The Aircraft Owners and Pilots Association (AOPA), one of the loud voices in the general aviation community, is generally opposed to increasing the number of terminal control areas or TRSAs. It has formally proposed a revision in traffic patterns that would keep high performance jet aircraft at top altitudes until the last minute before a landing, then bring them down quickly and in tightly controlled corridors to the airport.
The big need, according to AOPA spokesman Charles Spence, "is to increase the number of airports around major cities and to make sure that these airports have proper instruments."
The Cessna involved in the San Diego accident was practicing an instrument landing at the main airport, something not permitted at Washington National.
"You can't sterlize airspace no matter what you do," said John Galipault of the Aviation safety Institute, an Ohio-based organization that regularly infuriates the FAA hierarchy. "What we really need to do is make it easy for the general aviation pilot not to have to land at that primary airport."
There is a split in the aviation community about whether "see and avoid" or "see and be seen" is a reasonable means of separating aircraft in hightraffc areas.
"It is painfully obvious there is a need for something to supplement 'see and avoid," William B. Cotton, chairman of the air traffic control committee of the Air Line Pilots Association (ALPA), told a congressional committee last week.
The FAA tended to emphasize ground-control solutions to aircraft separation problems. ALPA vigorously supports a cockpit-based warning system. Some systems to be totally effective would require every plane to carry another piece of expensive equipment, and that raises the hackles of the weekend pilot.