TEMPO.CO, Jakarta - The National Transportation Safety Committee (KNKT) has found that there are two separate radio communication links that were active at the time of the taxiway collision between Batik Air's Boeing 737-800NG and TransNusa ATR-42 at Halim Perdanakusuma Airport on Monday, April 4, 2016.

Air traffic controllers (ATC), the airport's ground crew, and the cabin crew in control of the aircrafts were communicating through different radio pathways, just moments before the collision occurred.

KNKT Chief, Soerjanto Tjahjono, explained before the House of Representative's (DPR) Commission V in Jakarta on Monday, that communication between the flight crew and the ATC officials were done using Very High Frequency (VHF) radio, while communications between the ground handling support crew and the ATC officials were done in using Ultra High Frequency (UHF) radio.

VHF and UHF airwaves are used differently in commercial aviation. VHF frequency - which spans between 3-300 MHz - is usually limited to 118-137 MHz to be used for global communications between aircrafts in flight, while 121,5 MHz is allocated exclusively for emergency communications.

Meanwhile UHF spans between 300 MHz to 3 GigaHertz. The broad spectrum makes it particularly adaptable for hand-held communications devices, such as handy-talkies, cellular phones, microwave, personal radio, as well as satellite imaging and video transmission.

"ATC officers should not use VHF devices to communicate with ground staff - they won't be able to understand it clearly," said Soejanto. "And it works both ways, ground controls should contact cabin crew using UHF devices because it is not meant for such purposes."

According to Soerjanto, the improper use of frequency could cause inaccuracies in crucial information relating to aircraft movements in the taxiway of an airfield. "Had they used the same frequency, the Batik Air crew will be more aware that there was a TransNusa ATR-42 that was still trying to clear the runway - they'd crosscheck with ATC officers and probably, delay and/or abort their take-off," he said.

At the same occasion, the Executive Director of the AIRNAV Indonesia, Bambang Tjahjono, said that these findings had only be found once. "KNKT wants to see whether this blunder is a one-off case, or has it become a de facto standard operating procedure in other airports as well," he said.

Tjahjono said that all communications at all airports in Indonesia should be streamlined and simplified to utilize only VHF frequencies - a recommendation that KNKT has long prior to the incident.

The Directorate General for Air Transport, Novie Riyanto, said that under Law No.1/2009 on Aviation, all airports have been mandated to use only VHF frequencies. "And that applies to all airports - including Soekarno-Hatta International Airport," she said.

Authorities are now currently investigating whether the law has been enforced uniformly by all airports under Indonesian jurisdiction.

ANTARA