The Flight Data Recorder (FDR) of Boeing 737Max, which is one of the instruments in Black Box, may have the clues to what led to the Lion Air plane crash despite clear weather. This instrument can store more than a week’s details of speed indications, thrusts and autopilot selections among other parameters of the aircraft.

Divers have retrieved the Black Box from the Boeing 737Max jet of Lion Air that crashed into the Java sea with 189 aboard shortly after taking off from the Jakarta airport last Monday.

Aviation safety expert and former instructor of Boeing 737, Captain Mohan Ranganathan said that now that the FDR has been found, information on the crash may be available within two weeks. Ranganathan believes that there was a technical snag in the Flight Control system which made it unreliable.

A similar technical snag was reported earlier also in the jet. “One will get clues from the FDR as to whether the pilot had put on the Auto Pilot,” said Ranganathan. “What happens is that when there is snag in Flight Control, the Auto Pilot should not be engaged.

After FDR is analysed we will get to know if the Auto Pilot was on,” said Ranganathan. An unreliable Flight Control system is likely to give an erroneous speed indication. “If the speed indication given by the Flight Control is low, the Auto Pilot will push the aircraft to dive to achieve a higher speed.

This will happen when actually the speed is high,” said Ranganathan. Cockpit Voice Recorder may also give some clues as to what happened. “It can record whatever conversation or sound that was there in the cockpit,” said Ranganathan.

Ranganathan said that the aircraft did not experience Clear Air Turbulence (CAT) or turbulence due to weather disturbance. “I have seen the radar. It does not show any CAT. At 3000 to 5000 feet there is no CAT,” said Ranganathan.

Ranganathan has debunked speculation that the contact with the Air Traffic Controller (ATC) might have broken off because the aircraft was far off from the seashore. It is likely that the Boeing 737 Max being the latest version of Boeing would have Airborne Collision Avoidance System (ACAS). “If there is an ACAS, there cannot be any issue in contacting the ATC even if the aircraft is far-off into the ocean region,” said Ranganathan.

He said a four-hour familiarisation session is also given to every pilot to adjust in the environment of any new aircraft for getting type-rated. So, it is being assumed that the pilot was familiar with the system as the aircraft had been in operation since August.

“One or two sessions of familiarisation is the standard practice. It is done for upgradation of pilot’s license irrespective of the make,” said Ranganathan. The cockpit of the Boeing 737Max is the same. Only the presentation is different and there could be additional information displayed on the primary flight display there.