Information on the cause of the Sukhoi crash into Mount Salak is slowly emerging. It is clear that air traffic controllers may not have provided the right guidance to a pilot unfamiliar with local conditions. And there seems to be an effort to conceal these errors. Tempo obtained a recording of the final communication from the Sukhoi Superjet 100.
Pilot Aleksandr Yablontsev sent word to air traffic controllers in the East Terminal of Soekarno-Hatta Airport, Cengkareng. It was 2:24pm on Wednesday, May 9. He was piloting the Sukhoi Superjet 100 with registration number RA 36801 out of Halim Perdanakusuma airbase, East Jakarta, 12 minutes earlier.
One personnel in Cengkareng a senior air traffic controller, who in the interest of privacy will be referred to as 'N' replied, "RA36801 radar contact, maintain 10,000 proceed area." According to procedure, Yablontsev repeated the instruction given by the controller: "Maintain level 10,000 feet 36801." The jet headed for Pelabuhan Ratu, according to the flight plan.
Everything appeared normal. The pilot was flying the plane according to Instrument Flight Rules. This means that he followed the information from the navigational equipment in the cockpit and the guidance given by air traffic controllers. Before the plane took off, air controllers at Halim contacted N. They communicated closely: "Hello, approach request release, Mas. RA36801 to the Bogor Area in five minutes." The controller even joked, "RA36801 OK. Direct or through Tangerang?"
Carrying a crew of seven and 37 passengers including top officials of private airlines and reporters this first Russian-built passenger jet was holding a promotional flight. But this joy flight ended tragically: the plane crashed into a ridge on Mount Salak in Bogor. Over a month after the tragedy, pieces of information have begun to be uncovered, including the details of the conversation between the pilot and air traffic controllers.
After two minutes at an altitude of 10,000 feet, the pilot contacted the controller: "Tower, 36801 request descend 6,000 feet." Controller N replied, "36801 say again request." Yablontsev repeated his request to descend to 1,828 meters above sea level. N immediately replied, "OK, 6,000 copied." Then the pilot repeated, "Descend to 6,000 feet 36801."
As usual each afternoon, the traffic in the skies over Jakarta was hectic. On duty in the East Terminal one of five sectors of air traffic control: East, West, Lower North, Lower East, and Arrival North N was personally serving 13 flights simultaneously. He responded to requests to descend, circle, or climb from 13 pilots that day.
The controller became busy responding to requests from other pilots. According to one tower worker, although five people were listed as being on duty at that hour of the day, N was alone and unassisted. Ahmad, a controller who is actually an assistant, was guiding airplanes over in the East Terminal.
Over the radio, at 2:28pm, Yablontsev was again heard asking for approval. "Tower, 36801 request turn right circle present position." Not asking why the pilot wanted to turn right, N gave immediate approval: "RA 36801 approve circle to the right 6,000."
Chairman of the National Air Transportation Safety Committee (KNKT), Tatang Kurniadi, did not deny this when asked to confirm the communication between the pilot and the controller. "That was normal communication, without any guidance. We have more complete information," he said, on Tuesday last week. All of the communication data, radar readings, and airplane black box have been turned over to that institution. All of the controllers have been asked to give statements as well.
The request to turn the plane was the last communication from the pilot. Nearly five minutes later, the plane crashed into the ridge. From the black box recording, according to one Russian investigator, a moment after the request was approved, the pilot shrieked, "O Bozhe, chto eto takoe? (Oh God, what is this?)"
The controller only realized what had happened 24 minutes later. The plane was no longer on the radar screen. He tried to contact the Sukhoi three times, but there was no reply. Only dead silence...
A commotion broke out in the control room at Soekarno-Hatta Airport just as the Sukhoi was officially declared missing. Salahuddin Rafi, Director of Operations and Engineering for Angkasa Pura II gathered all of the controllers who were on duty that day. "Those who had not gone home had to stay on, and those who had already gone home were asked to return," said one controller.
At 11pm they met at the Sabda meeting room. About 20 controllers were present. Some stood because there were not enough chairs. Some ate noodles or fried rice from the cafeteria, given the suddenness of the meeting and the lack of time for meals. Salahuddin Rafi presided over the meeting, accompanied by Vice President of Air Traffic Services, Sutrisno Jaya Putra.
According to one participant, Sutrisno stressed the importance of reaching the same conclusion. He asked everyone there to take a look at the recorded communication with the Sukhoi. Then he made a simulation of the possible questions which could point to the controllers. "Let us close the gaps," said Sutrisno, as cited by another participant at the meeting.
The meeting ended at 3:30am, without any minutes being taken. The following afternoon, a similar meeting was held. This time it was led by Wisnu Darjono, Head of the Sub-Directorate of Air Navigation of the Transportation Ministry. There were about 31 participants. The President of the Indonesia Air Traffic Controllers Association (IACTA), I Gede Ketut Susila, was present.
The results of this meeting which ended near midnight was noted. It contained the approved version of the timeline surrounding the crash, but several points seemed peculiar. For instance, it was mentioned in the meeting report that, the "tower controller instructed the Sukhoi to head for the Bogor Area." In the transcript of the conversation, the controller was never heard to have mentioned any particular area to the pilot.
The Bogor Area in question is the Atang Sendjaja training area, located 20 nautical miles from Halim. The mention of this safe area for maneuvering is what led N to approve Yablontsev's logical-sounding request to descend and turn. Yet, according to the flight plan, this area was not the Sukhoi's final destination.
The Atang Sendjaja area, as seen on the flight map shown by Tatang Kurniadi, is indeed a place where planes traverse when flying from Halim to Pelabuhan Ratu. The problem, as recorded in the communication between Halim and Cengkareng, the Sukhoi planned to fly at an altitude of 10,000 feet. "It is still being investigated why the request to descend to 6,000 feet was approved," said Tatang.
Tatang did not consider the inclusion of the 'Bogor Area' in the chronology of the accident put together by Angkasa Pura as being anything strange. Sutrisno also denied that his office manipulated any communications or data in order to cover up any suspected error on the part of the controllers. "What for? Such a thing would certainly be uncovered when the KNKT investigates," he said.
Sutrisno ensured that the official response of Angkasa Pura regarding the Sukhoi was in line with the data and facts. "We reached a conclusion about what happened to the Sukhoi, but (how it is assessed) would be the jurisdiction of the KNKT," Mulya Abdi added.
TATANG Kurniadi did not want to speculate about the main cause of that 45-ton airplane crash. He said the analysis of the contents of the black box will only be completed 12 months later. However, he said that the pilot was fully in control of the plane. "The tower controller did not know there was a mountain (in the way)," he said.
Tatang persisted that according to the Sukhoi's flight plan, the plane was flying according to instrument readings at an altitude of 10,000 feet from Halim, heading towards Pelabuhan Ratu. He said the reason Yablontsev requested to descend to 6,000 feet remains a mystery.
One possible clue came from the National Institute of Aeronautics and Space (LAPAN), which recorded the appearance of cumulonimbus clouds over the peak of Mount Salak that day. These clouds which indicate imminent rainfall and lightning floated at about 6,000 feet above sea level. The clouds spanned 5 kilometers. "The interim assumption was that he was avoiding those clouds," said Tatang.
A Russian investigator who has seen the interim analysis of the black box said that Yablontsev wanted to conduct a maneuver after the request to descend was approved by the tower in Cengkareng. "He wanted to fly through the gap between the two mountain peaks," he said. Mount Salak has three peaks with deep ravines.
Aleksandr Yablontsev was a senior pilot. At age 57, he had flown 221 types of plane and had 14,000 hours of flight time. This former fighter pilot had also been involved in building the Sukhoi since 2004. With this experience and expertise, said the investigator, Yablontsev wanted to show off the sophistication of the Sukhoi to his guests.
Not familiar with the contour of the route to Pelabuhan Ratu, the pilot was surprised when turning right led to the ridge of Mount Salak. The damage to the ridge as a result of the collision indicated that Aleksandr was trying to bring the plane up, but did not have sufficient distance or time to evade it.
According to Gde Ketut Susila, President of IATCA I, according to the coordinates at the time of final contact, the plane was only 14 kilometers from Mount Salak. At a speed of 290 knots or 450 kilometers per hour, the pilot only had nine seconds to avoid the mountain ridge.
According to Transportation Minister, E.E. Mangindaan, both Yablontsev and copilot Aleksandr Kochetkov ignored the warning system which sounded 11 times an indication that the plane was headed towards danger. However, one controller in Cengkareng concluded that the controller contributed to the accident. "The controller should not have approved the pilot's request to turn right because the mountain was actually shown on the radar," he said.
If the controller had said 'negative' and ordered the plane to turn left, Yablontsev would have had two minutes to avoid the mountain summit. As N was busy monitoring many other flights at the same time, he may have been caught off guard. In the transcript of the conversation, he was not heard directing the Sukhoi or rejecting the pilot's request.
Mulya Abdi, Senior General Manager of Air Traffic Services at Soekarno-Hatta, said that the descent to 6,000 feet and right turn were approved by the controller because the Sukhoi was in the Atang Sendjaja training area. "This is a clear area. Even if a plane asked to descend to 3,000 feet it would surely be approved," he said.
Atang Sendjaja is a virtual space over Bogor which stretches 50 kilometers from Tangerang to Cikeas, and 20 kilometers wide. It is located 20 nautical miles or 37 kilometers away from the Halim airbase. This area is often used for training flight students because there is little air traffic.
There are conditions to flying in the training area. According to Heruyanto Sutiyoso, a senior instructor at flight schools, the maximum speed in this region is 250 knots. "And the pilot must fly visually, not on instruments," he said.
When it crashed into Mt Salak, the Sukhoi was traveling 40 knots over the maximum speed allowable in the training area. "The controller should have told him the conditions of flying in the training area," said one tower controller in Cengkareng. As a result of this negligence, N is currently suspended from work. He was treated two days for depression at the Mayapada Hospital in Tangerang.
By Bagja Hidayat, Wahyu Muryadi, Pramono
No. 43/12, June 20, 2012