Chicago — When violent weather conditions hover over an airport, who should decide whether or not aircraft continue to take off and land?
Though airport managers have occasionally closed airports in heavy snows, and the Federal Aviation Administration (FAA) requires certain minimum visibility conditions for landing or takeoff, generally the pilot decides whether or not to go.
But aviation experts are taking a hard second look at whether pilots may need better advice or firmer directions in the aftermath of the tragic July 9 crash of a Pan American 727 just after takeoff from New Orleans Airport during a severe thunderstorm.
Wind shear (a strong change in the direction of surface winds) is currently being considered as a key factor in the crash. New Orleans Airport happens to be one of 57 currently equipped by the FAA with special wind sensors to detect just such a problem. They were installed at the strong urging of the National Transportation Safety Board (NTSB) following a June 1975 crash of an Eastern 727 in New York.
Anemometers in the center of the field and five outlying areas up to two miles away pick up any strong differences in low-level wind directions and sound an alarm accordingly in the airport control tower. In this case two warnings apparently were broadcast by controllers in the tower to the crew before takeoff. It is not yet confirmed, however, whether or not the crew was monitoring the correct radio frequency for the alert and actually heard it. The crew switches rapidly between ground, tower, and departure control frequencies during the course of takeoff.
If the warning was heard, of course, pilot judgment and the degree of pressure on the crew to take off on schedule are again in question as they were in the Air Florida crash in Washington, D.C., last January.
But beyond the issue of pressure on pilots - a topic which the Air Line Pilots Association (ALPA) welcomes further research on - the severity of changing weather conditions as a factor in both crashes may well prod a new call by aviation experts to give controllers more ''say'' in whether or not runways and airports stay open.
After the 1975 New York crash, the NTSB recommended that the location and severity of unstable weather such as thunderstorms be considered by controllers in selecting which runways to use. The FAA countered that existing procedures, requiring pilots to be fully informed of weather conditions and to avoid known hazards, were sufficient. ''A decision of this nature must remain with the pilot ,'' said the FAA.
''I wouldn't be surprised if the board reissued that same recommendation again,'' says Matthew Finucane, director of the Aviation Consumer Action Project. ''The big question is going to be whether or not the tower should have more authority in bad weather conditions. Previously almost everything has been left to the pilot.''
Further technology aids may provide some help. For instance, after an Eastern 727 dropped 625 feet in the course of wind shear buffeting over the Atlanta airport in May 1980, the NTSB recommended that wind shear sensors also be installed at higher ground levels beyond airport boundries for more accurate readings for planes on landing and approach paths.
Also, ALPA for some time has urged installation of a cockpit device to serve both as a warning and a guide to action when wind shear conditions are encountered in flight. An ALPA spokesman contacted by the Monitor said he expects a ruling by the FAA on the subject.
It is probably unlikely that pilots as a group would welcome any further limitations on their decisionmaking authority by controllers. ALPA has long argued that weather conditions at airports are often very unstable and change in a matter of seconds.
But many pilots may at least welcome more advice when they face bad weather conditions.
''If the tower or some other responsible person at an airport advised me as a pilot against flying, I wouldn't fly,'' observes Robert P. Neuschel, a general aviation pilot who is a professor with Northwestern University's Transportation Center. ''Violent thunderstorms do things to airports that man doesn't really know about yet.''