Experts weigh in on possible causes

PETALING JAYA: Videos of the flying pattern of a Beechcraft 390 Premier plane that crashed at the Elmina township in Shah Alam suggested the aircraft could have possibly suffered asymmetrical (unbalanced) flight moments before hitting the ground.

Several seasoned aviators who had scrutinised the videos of the light business jet circulating on social media told The Star on condition of anonymity that the “misbehaviour” of the Beechcraft appeared to have occurred just several minutes before it nose-dived.

“Flight control issues are highly likely. The aircraft was in its final moments before landing at the Sultan Abdul Aziz Shah Airport, and it is only natural that the flaps would have been extended by the commanding pilot to slow it down.

“From a video I saw, a violent roll of the aircraft is seen as it heads for the ground. This suggests there could have been flap asymmetry, meaning one flap on a wing extended like it should while the other failed to.

“Another probable cause could be jammed flight controls, which left the Beechcraft unmanoeuvrable,” said the highly-experienced pilot, who has accumulated tens of thousands of flying hours in more than two dozen aircraft types ranging from light to heavy aircraft.

Aircraft flaps are located on the trailing edges of both main wings, and their function is to keep an aircraft in safe flight at lower speeds when extended.

The pilot said another possible cause of the crash is a “high-speed stall” or “high-G stall”, where there is a loss of airflow over a wing.

He said while stalls commonly occur at low speeds, they can occur at high speeds when excessive gravitational force from overmanoeuvring denies the aircraft the critical angle of attack it requires to maintain airflow over its wings and stay in flight.

“As for other causes, pilot incapacitation, though unlikely, should also be investigated. The weather was also not a factor, as it was a clear day and the wind conditions were light.

“My suspicions are merely based on five decades of flying and past data records of this particular aircraft.

“Each aircraft type has its own idiosyncrasies. In the end, only a thorough forensic probe by air crash investigators can determine the cause of the crash,” he added.

Another expert, who is an aircraft maintenance engineer and also holds a pilot’s licence, said he suspects a sudden shift in the aircraft load, possibly from moving passengers, could have altered the weight balance, causing an abrupt change to the aircraft’s centre of gravity.

“This is my suspicion after observing the videos. It could be passengers or even luggage moving and concentrated in one spot. Flight control issues should not cause such sudden and rapid changes to a flight.

“The aircraft can still be controlled, and the pilot would have radioed a ‘Mayday’ (distress call) to the nearest air traffic control.

“It is the same thing if it was an engine failure or engine fire. The pilot would have had a reasonable amount of time to recover from the emergency.

“However, in this case, at low altitude, the pilot appears to have had very little time to get out of the situation before the nose-dive.

“We hope the cockpit voice recorder retrieved by the authorities will shed some light on the cause of the crash,” said the engineer, who has been in the industry for almost 50 years.

As for the absence of a flight data recorder, more commonly known as a black box, he said the law does not make it mandatory for the Beechcraft 390 to have one as it falls under the light aircraft category, which applies to aircraft weighing less than 5,670kg.

In a Facebook post on Friday, Terengganu Mentri Besar Datuk Seri Ahmad Samsuri Mokhtar, who was an aerospace engineer, said he is inclined to believe the problem is related to the wings, possibly either aileron failure or a combination of both rudder and elevator failure.