The unprecedented power outage that hit Vietnam’s largest airport on Thursday took place because the uninterruptible power supply (UPS) systems that power the Ho Chi Minh City Area Control Center (ACC) went offline, the head of the country’s aviation watchdog said Friday.
The ACC, which oversees flights to and from Tan Son Nhat International Airport situated in the city, has three sources of power supply: the national power grid, generators, and the UPS.
There were no problems with the power from the national grid or generators at the time of the blackout, but one of the three UPS units at the ACC failed, Lai Xuan Thanh, head of the Civil Aviation Authority of Vietnam (CAAV), told reporters in Hanoi.
“As ACC technicians tried to restart the failed UPS, the other two broke down as well,” Thanh added.
The UPS is capable of supplying power to the whole flight operating system at the ACC.
“The center was receiving power from the national grid and the generators via the UPS units, so when all of them broke down, the power was cut,” Thanh elaborated.
The power cut lasted from 11:05 am to 12:19 pm and disabled the radar system that controls air traffic at the airport.
The incident, which Thanh said was the first of its kind in Vietnamese aviation history, affected 92 flights.
At the time the power went out, 54 out of the 92 affected flights were within the city’s flight information region (FIR), according to the CAAV chief.
As of 3:40 pm Thursday, only two out of the three UPS units had resumed operation, while the last device only came back online around noon the following day, Thanh said.
The CAAV suspended two people from the ACC on Thursday for investigation following the power failure.
The suspended are the leader and a technician on the team that was on duty at the ACC when the dangerous incident occurred.
The authority also demanded a review of the technical operations at the center.
The CAAV will continue inspecting the case and release an official report on it by November 29.
Tan Son Nhat, which is the largest airport in Vietnam, handles about 20 million passengers a year.