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Indonesia investigates airprox incident involving a Cessna 172 and an ATR 72-600
3 January 2018

The Indonesian NTSC has released a preliminary report on an airprox incident involving a Cessna 172 and an ATR 72-600.

On 21 November 2017, a Cessna 172S aircraft registered PK-BYK was being operated by Balai Pendidikan dan Pelatihan Penerbangan Banyuwangi (BP3B) on a cross-country training
flight from Blimbingsari Airport (WADY) to Sumbawa Besar Airport (WADS). On board the PK-BYK were two student pilots.
PK-BYK departed from Banyuwangi with the intention to cruise at an altitude of 7,000 feet. When approaching point KUBU TAMBAHAN, the pilot requested permission from the Bali Approach controller to climb to 9,000 feet, which was approved.
At the same day, an ATR 72-600 aircraft registered PK-WHS was being operated by Wings Air as a scheduled passenger flight from Sumbawa to Lombok International Airport (WADL), with flight number WON1861.
WON1861 departed from Sumbawa with a cruising altitude of 8,000 feet. On board the aircraft were two pilots, two flight attendants and 62 passengers, the Pilot in Command (PIC) acted as Pilot Monitoring and the Second in Command (SIC) acted as Pilot Flying.
When PK-BYK approached point NAMP ISLAND, the pilot saw the ATR 72-600 aircraft flying through clouds from the opposite direction with the aircraft nose slightly up. The pilot then decided to descend from 9,000 feet with the intention to avoid the ATR 72-600 that was maintaining 8,000 feet.
While descending, the Pilot Monitoring of PK-BYK requested descent clearance to the Sumbawa Tower controller who then provided traffic information of WON1861 which was maintaining 8,000 feet. PK-BYK pilot did not respond to this traffic information.
The pilot of WON1861 then received a TCAS RA (Resolution Advisory) and performed a maneuver to the right to avoid the Cessna. The Bali radar screen recorded that the altitude of PK-BYK was passing 8,000 feet and the horizontal distance with WON1861 was 2 Nautical Miles. Both flights continued safely to their destinations.

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