In northern California this summer, the Federal Aviation Administration (FAA) unintentionally performed it's first operational test of "free flight"; aviation without direct air traffic control. This was an unintentional experiment because it was a result of a total shut-down of the Oakland Air Route Traffic Control Center (ARTCC).
Although Oakland is only the 16th busiest ARTCC, it's responsible for the largest block of airspace of any ATC facility; 18 million square miles. Oakland directs all upper-level flight from San Luis Obispo, California to the California/Oregon boarder, including most Pacific oceanic routes. The failure happened at 7:13 a.m. local time during the morning "departure push". Controllers estimated there were 60-80 aircraft under their control when the power died. All radar screens went dark and all radios went silent. It took 45 minutes to restore radios and bring up a backup radar system. It was more than an hour before the main radar presentations came on line.
One controller described the sudden quiet in the control suite as "the loudest silence I've ever heard" (UPI , 1995). He went on to say there was "panic on everybody's face" as they realized they had been rendered deaf, dumb, and blind by this catastrophic equipment failure. It took a few minutes for controllers to realize the shut-down had affected the entire facility. There was no book procedure to cover this emergency scenario, so most controllers improvised.
Controllers in adjourning Los Angeles, Salt Lake, and Seattle ARTCCs and various Terminal Radar Approach Controls (TRACON; the level of radar coverage below upper-level ARTCC radar) were asked to take control over all airspace within their radar coverage, and divert aircraft under their control inbound to Northern California. Control towers in San Francisco, Oakland, San Jose, Sacramento, and other airports in the area were instructed to hold all IFR departures on the ground. The most difficult problem was getting notification to the airborne flight crews. In one case, controller Mike Seko said, "We had Napa tower telling high altitude aircraft Oakland Center had lost everything, and to switch to emergency frequencies" (Seko, UPI, 1995). But most airborne aircraft on Oakland Center frequencies were in a state of "lost-comm" unless they figured out what happened on the ground and switched to another ARTCC or TRACON.
Flight crews did their own improvising. Some pilots squawked VFR and continued the flight on their own. Others continued on their previously issued clearance, while others climbed into or descended out of Class A airspace without a clearance.
Later analysis tells us one of the biggest problems was nobody believed a prolonged outage like this could occur. Both controllers and supervisors worked on the assumption their radar and radios would come back "any moment now". The same thought process prevailed at Bay (Oakland) TRACON where operations were paralyzed by the Center's blackout.
It's impossible to say how many separation losses occurred during the hour-long episode. Some near mid-air reports were filed, but the vast majority of separation-loss situations will probably go unreported. After power was restored, and the primary radar system was returned to operation, extensive air traffic delays, diversions, and flight cancellations persisted for many hours at Bay area airports, especially departures from San Francisco International.
We may never know the full aftermath of this incident. Changes will be made as to how power is fed to ATC facilities, and how maintenance is performed. Contingency plans will be rewritten and controllers will be trained how to implement them. Meanwhile, controllers nation wide are brushing up on their non- radar and lost-comm procedures.
After an extensive investigation, it's now clear why the failure occurred. One of three power sources was down for...