Small plane downed near Oak Hill Road in Williston
By Greg Elias
A pilot’s mistakes and an air traffic controller’s failure to notice low-altitude warnings were factors in a plane crash last year in Williston, a report by the National Transportation Safety Board concludes.
The Nov. 22 crash occurred in a wooded area not far from homes on Partridge Hill, a dirt road off Oak Hill Road just south of Interstate 89. The plane was on a landing approach to Burlington International Airport when the crash occurred, killing pilot Donald Roberge of Ellington, Conn.
The NTSB report released last week cited Roberge’s failure to follow proper flight procedures as the primary reason for the crash. But the report also cited as contributing factors an unnamed air traffic controller’s failure to notice alerts that showed the plane’s landing approach was too low and a delay in telling the pilot to climb.
The alert system gives controllers both audible and visual alarms when a plane is flying too low. The system emits a five-second beeping tone and flashes a green low-altitude warning.
Steve Walsh, an air traffic controller at Burlington International Airport and local union representative for the National Air Traffic Controllers Association, said he has spoken with controllers who were on duty when the crash occurred. He said they never heard the alarm.
A replay of the radar display indicated that the low-altitude warning did flash, the NTSB report said. But Walsh said no alarm was heard when audio recordings of the incident were reviewed.
Without the audible alarm, a controller may never notice the radar warning is flashing, he said. Controllers are also monitoring the sky though windows in the control tower and tracking other planes’ positions.
“The controller has got a lot of things to be scanning,” Walsh said.
Roberge, 49, held a commercial pilot’s license. He had 479 hours of flight experience and 92 hours of instrument flight time, the NTSB report said.
Roberge left Hartford-Brainard Airport in Connecticut at 5:30 p.m. He was flying alone in a four-seat, two-engine Piper Aztec aircraft. It was snowing, with the wind blowing at 17 mph and gusting to 23 mph.
At 6:22 p.m., Roberge first contacted the arrival controller, according to the report. He was told to maintain course.
Control of the plane then was handed off to the local controller at Burlington International Airport. Roberge was cleared to land on runway 33.
At 6:43 p.m., the arrival controller, who had continued monitoring the plane, noticed a problem, the report said. “Hey, that Aztec is a little low on the approach there,” he said.
But he told ground control, which directs runway traffic, rather than the controller who guides landings, the report said. Sixteen seconds later, he notified the correct controller. A second later, the landing controller ordered the pilot to “climb immediately.”
There was no response. Roberge’s airplane had disappeared from the radar screen five seconds earlier, according to the report. The plane first struck 30-foot-tall trees, then crashed in a field.
Nearby residents said they heard what sounded like a plane with engine trouble, followed by a loud boom and a fireball. It was snowing heavily at the time.
The NTSB’s inspection of the plane showed no evidence of mechanical failure.
Departures and arrivals at Burlington International Airport show up as symbols on a radar screen, Walsh said. But he said when an accident occurs “the human aspect hits you in the gut.”
“The (air traffic controller) involved feels terrible,” Walsh said. “It’s the last thing anyone wants to happen.”