It was the second time this month the runway lights failed
As a Horizon Airlines flight was making its final approach into Wenatchee shortly before midnight Sunday the runway lights at Pangborn Memorial Airport suddenly went dark.
The plane circled the field while a Horizon dispatcher contacted the airport but the pilot eventually had to return to Seattle for refueling. It then headed back to Wenatchee, where the lights had been repaired. Sleepy-eyed passengers finally arrived close to 2:30 a.m. Monday.
In total, Pangborn was without runway lights for more than an hour, said operations manager Ron Russ. It was the second time this month the lights had gone dark as an airliner was on final approach.
The problem in both cases, Russ said, was the failure of a capacitor in a current regulator that controls the airport lights. When the capacitor failed, the entire lighting system shut down to protect itself from further damage, he said.
Capacitors are like large fuses encased in metal and each unit of the runway lighting system holds several of them.
In the case of the Horizon flight in early January, airport officials had already been alerted to the problem by another pilot and were able to make repairs in time for it to make its early evening landing, though after spending time in a holding pattern.
In the Sunday incident, there was no such warning, Russ said.
”As the Horizon aircraft was on final approach, they attempted to increase the intensity of the airport lights” Russ said. “The lights can be controlled by a pilot when they’re on final approach to adjust the intensity based to their needs. When they did that, it shocked the current regulator that controls the output to the airport lights and a capacitor in that regulator failed.”
When the Horizon dispatcher notified airport officials about the problem, it took about 20 minutes for on-call airport personnel to arrive and about another 45 minutes for the problem to be diagnosed and repaired, Russ said.
There have been previous runway lighting failures but it has been four or five years since the last incident, Russ said.
Control of runway lights by pilots is not unusual for airports without air traffic controllers, he said. The lights are automatically turned on to a dim level as dusk approaches and stay that way until full light, or they’re adjusted by a pilot. Airliners could land with the dimmer lights but pilots often prefer brighter runways.
When asked how future issues with the lighting can be avoided, Russ said good preventative maintenance is the most likely solution.
“We have a regular maintenance schedule where we replace those capacitors about every three years. We have three regulators and we replace the capacitors in one regulator each year, so we get on that three-year cycle to try to prevent this from happening.”
After the first incident this month, the airport replaced the damaged capacitor but didn’t have enough capacitors on hand to replace all of them, Russ said.
“We ordered them after that incident but they were back-ordered.”
He said there was a shipment due to arrive Thursday.