The radar system is known as the ASDE-X and when it breaks down, the screen air traffic controllers use to help track aircraft and vehicles on the ground goes blank.
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A whistleblower air traffic controller at LAX tells Eyewitness News that the repeated failures of the ASDE-X system is "a disaster waiting to happen."
"For days or weeks at a time we are left without a necessary piece of safety equipment," the controller says. "At LAX, the entire airport community is not visible from the tower and the ASDE-X is our eyes."
About 87.5 million people traveled through LAX in 2018, setting a new all-time record for airport traffic at what's now the nation's second busiest airport. The radars are at the top of two towers -- one on the north side of LAX and one on the south side. Each radar scans and tracks the surface movement of planes and vehicles for its half of the airport.
The Federal Aviation Administration owns and is responsible for maintaining the air traffic control radars at LAX. The FAA declined our repeated requests for an interview, would not allow us inside the air traffic control tower and would not allow air traffic controllers to speak with us.
So, we tracked down Caesari Vallente, one of the LAX radar technicians that has to fix the system every time it breaks down.
"If I was a regular citizen and I knew about this, I would not fly," says Vallente, who is also a union representative for the Professional Aviation Safety Specialists.
Vallente and other technicians have to climb the 100-foot towers to make repairs because the elevators have not been certified for "human use" for more than two years.
"It's a fairly old system, some of the parts in there are from when the date they were installed," Vallente told Eyewitness News. "These outages have been happening for the last year and a half."
Eyewitness News also tracked down two retired FAA engineers with a combined 50 years of experience on this radar system. Rick Castaldo helped to design and install the radars back in the nineties as the FAA's chief engineer on the system.
"These radars should be replaced immediately," said Castaldo. "The rotating parts are ancient and the high failure rates are going to continue. They've been rotating 24 hours a day, seven days a week, 365 days a year since the early 90s."
GROUND RADARS DEPLOYED AT LARGEST AIRPORTS AFTER SERIES OF DEADLY COLLISIONS
The ground radars were put in place at LAX and 35 other major airports across the nation after a series of deadly crashes, including a runway disaster at LAX in 1991 that killed 35 people.
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U.S. Air Flight 1493, a 737, landed on top of a SkyWest commuter jet after a confused air traffic controller cleared the larger plane to land on the same runway where the smaller plane was waiting to take off.
"It was well recognized that as the airports got busier, that it was harder for controllers to keep track of every airplane everywhere," Castaldo said. "The only reason they're there is to prevent airplane accidents. Well, if they're broke - they can't do that."
The parts that have been breaking down are inside the dome, which you can see spinning at the top of each of the two towers at LAX. Those surface movement radars and its components are the 30-year-old parts of the overall system now known as ASDE-X. That older-style radar can only see "blobs" on the runway.
"That radar sees stuff - a reflection comes back - but it doesn't know if it's a truck or an airplane," said retired FAA engineer Bobby Nichols.
But the overall ASDE-X system combines that data with more precise information from newer multilateration sensors placed around the airport and GPS satellite tracking from aircraft equipped with transponders known as ADSB.
All of that information gets fused together and suddenly the air traffic controllers can see more than a blob - they can see if it's a plane, its flight number, its speed and altitude.
"You've got a system that actually gives you not only the location of everybody and which way they're moving, how fast they're moving - it also identifies them," said pilot and ABC News Aviation Consultant John Nance.
But when those 30-year-old spinning radars break down, the retired FAA engineers say the whole system is knocked out. It also shuts off the runway safety lights that tell pilots to stop when a runway is not safe to enter or cross. And it shuts off the "safety logic" system which alerts controllers to potential collisions.
"The controllers don't necessarily stare at those screens, but they do listen for alerts," said Castaldo.
"You've got a tool and you shut off the tool, it might be similar to driving on a highway with your lights on... and then you go shut the lights off," said Nichols.
FAA: MAJOR COMPONENTS OF GROUND RADARS HAVE BEEN REPLACED
The FAA refused over a course of four months to do an interview with Eyewitness News, but said in a statement that major components of the system have been replaced and since then there have been no unscheduled outages.
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An FAA spokesperson said the ASDE-X system does not replace the need for controllers to visually scan the airport with their eyes and that the outages "have not resulted in a reduction in runway safety."
"You were told that the outages haven't led to a reduction in runway safety," said Castaldo. "I can't even think of a nice word to call that - it's a vulgarity! It's BS, let's be clear."
Eyewitness News obtained an internal FAA report from November 2018 which clearly states that one or both of these radars "was out of service" for 1,627 hours in 2018 -- that's a total of 67 days. But the FAA insists that one sentence in the report is not accurate, was poorly written and reflects times when only part of the system was malfunctioning.
Meanwhile, the whistleblower air traffic controller tells Eyewitness News that one or both radars was out of service for at least a month total in 2018.
What are the real numbers? We don't know because the FAA refuses to tell us.
"The meaningful part of those statistics is that the problems are increasing, the maintenance demands are increasing, and that should be an alarm," said Nance.
Photographs from that internal FAA report show busted bearings, a busted idler, a busted sprocket and worn-out belts inside the spinning dome.
The report also notes that the broken tower elevators and a backlog for replacement parts contributes to the delays in fixing the radars.
And while that report recommends repairing the tower elevators, FAA emails obtained by Eyewitness News indicate that the elevators cannot be repaired because the needed parts are obsolete and no longer exist.
Replacing the elevators would cost at least $300,000 apiece, according to those emails. An FAA spokesperson says the current plan is to refurbish the ladders used by technicians or building a stand-alone staircase.
Castaldo said the broken elevators and failing radars are part of a bigger picture we should all be concerned about. The FAA's latest "Capital Investment Plan" indicates the air traffic control infrastructure had a repair backlog estimated at $4.3 billion as of July 2017.
"Our national airspace is falling apart," said Castaldo. "This radar is the tip of the iceberg."
Got a tip? Email ABC7 Investigative Producer Lisa.Bartley@abc.com