Mesa Flights on Track after Bad Weather

A day-and-a-half after Mesa Air Group took over daily service to Las Vegas from the Merced Municipal Airport, its first flight took to the air Monday night.

"Mesa is back on track now," said Merced Airport Manager Lloyd Partin. "Thank goodness for the small improvement in the weather."

Foggy weather kept Mesa's Beechcraft 1900s from landing in Merced on Sunday and part of Monday. Travelers booked on the first flight were given the option to fly out of the Fresno airport, exchange their tickets for a flight later in the week or get a refund.

But Merced flights weren't the only ones affected by the fog.

A Sky West airline employee out of the Modesto City-County Airport said they had several flights delayed due to weather conditions earlier this week.

On Sunday night, Partin said two corporate jets and a turbo-prop aircraft diverted from Fresno to Merced, because "visibility had dropped below minimums required" to land at the Fresno airport.

Almost every airport has an instrument landing system that requires pilots 200 feet from the surface of the runway to have a half-mile of horizontal visibility before landing.

At Merced's airport, Partin said, that means pilots must be able to see a third of the runway.

This is a requirement of the CAT 1 instrument landing system. There are also CAT 2 and CAT 3 systems, whose requirements change to 100 feet and 25 feet respectively.

"Merced's instrument landing system is the same (CAT 1) system in use at many other commercial airports throughout the Valley," Partin said.

He estimated about 80 percent of all airports use the CAT 1 system.

Partin said switching systems isn't a plausible solution for the Merced airport.

Along with more sophisticated equipment on the airport, he said, comes more stringent training requirements for pilots and much more sophisticated equipment onboard the aircraft.

Although a CAT 2 system would lower the height-off-the-runway requirements for pilots, it still requires the fourth-mile of visibility -- something most pilots didn't have on Sunday at the Merced airport.

"Fog is a safety issue for aircraft," said Gary Sanger, a meteorologist for the National Weather Service office in Hanford.

Fog forms when temperatures cool and the moisture in the air condenses, forming tiny droplets. So lightweight, these droplets stay suspended in the air, Sanger said, until they get large enough to become drizzle.

During the day, sunlight creates enough warmth to burn off most or all of the moisture. This is why fog is thicker in the morning and evenings.

The Central Valley has more fog than other areas because it is just that -- a Valley.

"There are mountains on three sides," Sanger said. "Air mass, once it gets into the Valley, really can't go anywhere."

In the last couple of days, Sanger said there haven't been any mechanisms -- like storms or wind -- to clear the moisture out.

Despite the problems fog causes for those trying to follow instrument landing system requirements, Partin said it is the easiest weather to fly in.

"Fog is very smooth, no bumps," Partin said.

Because fog tops out no higher than 2,000 feet, Partin said pilots only spend about a minute in the fog while rising to their traveling altitude.

Partin should know -- the airport manager has clocked more than 3,000 hours as a pilot, many of them when he was flying commercially.

"I have landed here under the most difficult of conditions," he said. "I have never had a problem getting into Merced."

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