Officials are working to resolve a problem with a visual guidance system at Poplar Bluff Municipal Airport that began shortly after new lights were installed a year ago.
A warning concerning the issue has been posted for pilots with the Federal Aviation Administration.
This is not a safety hazard and pilots can land without the system, said interim director Gary Pride, who was hired in November.
The problem occurs when one or more of the four lights that make up the precision approach path indicators shut off or blink, he explained.
All four lights are needed to make an instrument assisted landing using the PAPI system.
The contractor who installed the lights and the manufacturer are now working with the city to identify the problem, Pride said.
The problems began about a month after the lights were installed, but were reported infrequently.
"In the past two weeks, it has been more or less every day," Pride said, adding, "The glitch will not cause (pilots) to have an accident. They can either use it or not use it, but it's not going to mislead them."
The increased frequency may make it easier to identify the problem, which may be caused by faulty circuit boards, Pride said.
Repair technicians have visited the airport since November, but the visits did not coincide with a malfunction, he said.
PAPI lights are more critical during low visibility, such as Monday morning's foggy conditions.
"That's where pilots ... make the decision as to whether it's important enough to them to approach or not," Pride said. "If you're on a glide slope coming into land, the PAPI lights give you the visual indication that you're on the correct descent. If you don't have that visual aid, you can still do it."
The lights were replaced with a grant from the Missouri Department of Transportation. The equipment that was replaced was about 50 years.
A new LED light system was expected to be brighter and more reliable. The $454,200 project included other upgrades.