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Problems in Air Traffic Control and Proposed Solutions
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
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 maintenance testing. The
second power source failed unexpectedly. When technicians tried to bring the
third power source on-line, a faulty circuit board failed in a critical power
panel, preventing power from being restored. Oakland Center was completely dead.
This was the story of one air traffic control facility's system failure.
Don't think this was an isolated incident though. A partial list of this years
ATC radar failures:
? Chicago Center lost their primary radar system when the 1970's technology IBM
9020E host computer went down for 29 hours.
? ASR-9 radar failure at Miami TRACON possibly due to a lighting strike. Miami
switched to a back-up ASR-9 system at Fort Lauderdale. The Fort Lauderdale
system then failed just as technicians at Miami brought their radar on-line.
Miami failed again forcing controllers to revert to non-radar procedures.
? Fort Worth Center's host computer lost power while technicians were replacing
some related processing equipment. Back-up radar was on-line for almost three
hours. All departures experienced a 60-90 minute delays.
? Pittsburgh TRACON briefly lost communication and radar with 38 flights in the
air. Radar contact was lost
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Air traffic control, Area Control Center, Federal Aviation Administration, National Air Traffic Controllers Association, Procedural control, Tracon II, Transponder, Free flight, Oakland Air Route Traffic Control Center, National Airspace System, Anchorage Air Route Traffic Control Center, federal aviation administration, oregon boarder, air traffic control, traffic control center, san luis obispo california, radar screens, radar coverage, oceanic routes, flight aviation, california control, radar system, equipment failure, artcc, route traffic, control towers, morning departure, level flight, adjourning, operational test, proposed solutions
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