1980 Bangkok Approach Accident Involving HS-748 HS-THB

Flight Operations and Approach Sequence On 27 April 1980, an HS-748 Series 11 registered HS-THB was operating a scheduled domestic passenger service. The flight number for the outbound leg was TG221, which departed Bangkok International Airport at 0101 h and made scheduled stops at Khon Kaen, Udon, and Nakhon Phanom. The return leg, flight number TG231, departed Nakhon Phanom at 0408 h and returned via Udon and Khon Kaen. After take-off from Khon Kaen at 0550 h, the pilot reported to Bangkok Area Control Centre at 0559 h, stating the aircraft was climbing to 6,000 ft and requesting clearance to Bangkok International Airport via W6-KT-W1-BKK. Bangkok Area Control Centre cleared the aircraft to maintain FL 120. The pilot reported reaching FL 120 at 0614 h and passing over KT at 0626 h. At 0627 h, Bangkok Area Control Centre confirmed radar contact, placing the aircraft 5 miles northwest of KT. At 0642 h, Bangkok Area Control Centre cleared the aircraft to descend to 8,000 ft and provided an altimeter setting of 1,008 mb. At 0644 h, the pilot was advised to contact Bangkok Approach Control on 119.1 MHz. Upon contact, the pilot reported maintaining 8,000 ft. Bangkok Approach Control then instructed a descent to 6,000 ft, again providing the 1,008 mb altimeter setting. Further descent instructions followed, with the pilot reporting reaching 1,500 ft at 0653 h. At 0654 h, Bangkok Approach Control informed the pilot the aircraft was 7 miles from the Outer Marker and cleared it for an ILS approach to runway 21R. At 0656 h, the pilot was advised to contact Bangkok Tower on 118.1 MHz, but no response was received. Bangkok Approach Control attempted to contact the aircraft until 0709 h without success.