The Russian captain of a Sukhoi Superjet 100 that crashed in Indonesia last May inhibited the airplane’s terrain-warning system after receiving what he apparently judged to be a spurious nuisance alert, crash investigators say.
Indonesian investigators said the Superjet’s TAWS sounded a warning 38 seconds before the twinjet slammed into a mountain in the jungle near Jakarta, killing all 45 aboard the demonstration flight on May 9. A disastrous link in the accident chain was a conversation unrelated to the flight between the pilots and a company official in the cockpit that distracted the crew from its duties. According to the accident report, the captain requested a descent from 10,000 feet to 6,000 feet and a right-hand orbit, which Jakarta ATC approved. But the crew soon became distracted by a “prolonged conversation.” The captain, who was flying, failed to change heading during the holding pattern. Consequently, the airplane “unintentionally exited the orbit,” according to the report.
An analysis by accident investigators found that the airplane might have been able to avoid the impact up to 24 seconds after the initial terrain warning sounded. The jet crashed at the 6,000-foot level of Mount Salak, which was shrouded in clouds. The jet had been cleared to such a low altitude because controllers mistakenly coded it as a Sukhoi Su-30 fighter and not a Sukhoi passenger jet.
The crew did not have charts on board the airplane for the area, and Jakarta’s ATC facility is not equipped with minimum safe altitude warnings for the sector where the Superjet crashed, investigators noted.