A navigational aid system that helps pilots land at the airport during low visibility and bad weather conditions conked out on Saturday morning, forcing aviation authorities to temporarily suspend night operations at the Ninoy Aquino International Airport (NAIA).

The Very High Frequency Omni Radio Range (VOR) station located at the intersection of Runways 06/24 and 13/31 suddenly conked out, forcing the Civil Aviation Authority of the Philippines (CAAP) to suspend night operations while technicians are trying to repair the system.

However, CAAP Director General Alfonso Cusi left it to the discretion of airline companies if they would still allow their pilots to land at the Manila airport although its VOR navigation aid system is down.

In a meeting with officials of the Airline Operators Council who had appealed to allow their flights to land using Visual Flight Rules (VFR), Cusi said he left it to the discretion of the airline companies if they will proceed or not.

The VOR provides landing aircraft with bearing information and enables pilots to determine their relative direction to and from the runway. This navigational aid, which is used with the Distance Measuring Equipment (DME), provides pilots with an electronic guide in landing their aircraft during low visibility and bad weather conditions.

“We were able to establish a set of procedures for landing without VOR,” Cusi said. “However, they will only be allowed to land if and only the visibility is good and if the weather is clear.”

“The safety of the passengers is our utmost concern. We strongly urge the airline companies to delay their flights until the morning when visibility is better,” Cusi added.

Lito Casual, the technical assistant of Cusi, said that with the navigational aid down, they were forced to issue a Notice to Airmen (Notam) informing the aviation community about the temporary suspension of night operations at the Manila airport and that they are implementing Visual Flight Rules (VFR) until sunset.

The Instrument Landing System (ILS), another navigational aid to help pilots land their aircraft, could not be used as it is presently undergoing rehabilitation.

Casual said all their radar systems are working properly and assured that the system continues to safely guide all aircrafts up to the visual approach point, which is about eight kilometers from the edge of the runway. “It is at this point that the VOR should kick in,” Casaul said.

Since the weather and visibility was good on Saturday, the CAAP allowed aircrafts to land using VFR but only up to sunset, while there was still visibility.

Casaul explained that VFR is visually and weather dependent. “Good thing we have good weather so we were able to allow airplanes to keep on landing.”

He added that the CAAP's Navigation System Group is busy trying to fix the problem so that they can resume with normal operations at the soonest possible time.

Casaul, however, said that even if they don't get to finish the repairs on the navigational aid, all airplanes en route to Manila can be safely diverted to other airports in the country, including Clark, Cebu, and Subic.

Meanwhile, airline companies have started cancelling several flights that will be affected by the suspension of runway operations. As of 3:30 p.m., Cebu Pacific has already cancelled a total of 28 domestic flights.

International air carriers are still waiting for the outcome of the repair works and will make an announcement of affected flights after sunset.