By Fergus Jensen and Kanupriya Kapoor
JAKARTA (Reuters) - Indonesian investigators may release some initial findings next week into last month's crash of an AirAsia passenger jet that killed 162 people, but the full preliminary report will not be made public, a government official said on Wednesday.
The Airbus A320-200 vanished from radar screens on Dec. 28, less than halfway into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore. There were no survivors.
Data from radar and the aircraft's two "black box" flight recorders is providing investigators with a clearer picture of what occurred during the final minutes of Flight QZ8501.
Transport Minister Ignasius Jonan on Tuesday told a parliamentary hearing that the plane had climbed faster than normal in its final minutes, and then stalled.
Three days after the crash a source familiar with initial investigations had told Reuters the plane appeared to have made an "unbelievably steep climb" that may have pushed it beyond its performance envelope.
Investigators are expected to submit a preliminary report to the International Civil Aviation Organization (ICAO) early next week, in line with ICAO regulations that the preliminary report must be filed within 30 days of the date of the accident.
"One month after the accident we will just make a preliminary report. No comment and no analysis," Tatang Kurniadi, chairman of the National Transportation Safety Committee, told reporters.
"This will not be exposed to the public. This is for the consumption of those countries that are involved."
The NTSC will hold a press conference on the AirAsia crash next Wednesday, but it was not clear how much will be disclosed.
The final report of the crash investigation findings, which will be made public, must be filed within a year.
Kurniadi reiterated that investigators have found no evidence of foul play in the disaster.
Transport Minister Jonan on Tuesday gave the first detailed information about the final minutes of Flight QZ8501 based on radar data. Data from the black box flight recorders would give a more detailed picture, Kurniadi said.
At 6:17 a.m. on Dec. 28, three minutes after air traffic control unsuccessfully tried to make contact and asked nearby aircraft to try to locate QZ8501, the A320 turned to the left and it began to climb from its altitude of 32,000 ft (9,750 meters), Jonan told a parliamentary hearing.
The rate of the climb increased rapidly within seconds to 6,000 ft a minute, before accelerating further to 8,400 ft a minute and finally 11,100 ft. The aircraft reached 37,600 ft just 54 seconds after it began to climb before it appeared to stall.
The aircraft began to fall at 6:18 a.m., dropping 1,500 ft in the first 6 seconds before reaching a rate of descent of 7,900 ft per minute until it reached 24,000 ft, at which point it disappeared from the radar.
Pilots and industry observers told Reuters that if an aircraft makes a rapid climb and start to lose speed, it would be likely to stall and suffer from a loss of control.
Indications the aircraft stalled aerodynamically imply the cockpit would have been filled with warnings alerting pilots to the danger, calling for them to tip the nose of the plane downwards in order to restore lift.
Airbus pilots say such warnings include an automated voice saying "Stall Stall" as well as an audible electronic signal and red warning light. In the 2009 crash of an Air France jet in the Atlantic, pilots appeared to ignore the warnings, prompting industry-wide efforts to reform pilot training.
Based on Jonan's data, there did not appear to have been a controlled descent in the case of QZ8501 and the aircraft appeared to have fallen rapidly before crashing into the sea, according to pilots and industry observers.
Bad weather in the area has been cited a possible factor in the crash, with the other aircraft close by at that time flying at altitudes of between 34,000 and 39,000 ft.
The investigators were looking into why this was the case, as well as QZ8501 pilots' reaction to the storms and clouds in the area, according to a source close to the investigation.
Industry experts say that the margin for error at higher altitudes is smaller than at take-off or lower down.
While the A320's systems usually prevent pilots from doing anything outside usual safe flight parameter, these protections can be disabled in some circumstances, handing control to the pilots and leaving it to manual flying skills.
(Additional reporting by Siva Govindasamy in SINGAPORE and Tim Hepher in PARIS; Writing by Randy Fabi; Editing by Alex Richardson)