The 737 line, which has flown for more than 50 years, is the world’s best selling modern passenger aircraft and viewed as one of the industry’s most reliable. However, the 737 Max 8 aircraft has only been in commercial use since 2017.
The engine is a bit further forward and a bit higher in relation to the wing, compared to the previous version of the plane. Jakarta-based aviation analyst, Gerry Soejatman said the size of the engine affects the balance of the plane. The new MAX 8 variant, with bigger engines was designed to use less fuel.
System under scrutiny
An advanced control system designed to stop Boeing 737 MAX 8 from stalling in mid-flight is now under scrutiny following the crash. The aircraft’s state-of-the-art Maneuvering Characteristics Augmentation System (MCAS) was also implicated in the downing last year of Lion Air Boeing 737 MAX 8 in Indonesia, when all passengers and crew members also died.
In both cases, the aircraft were just a few months old and crashed minutes after take-off. Both planes were reported to have flown erratically, climbing and descending steeply before finally crashing.
“We are hearing that the problem was similar to the Lion Air accident; unreliable airspeed, difficulty in controlling the aircraft, and both had asked to return to the airport,” Soejatman, said.
An initial investigation in the Lion Air accident suggested a faulty sensor had triggered the plane’s automated MCAS system possibly resulting in the nose of the aircraft being pushed down.
“New planes do have issues,” said Soejatman. “But they are usually solved before delivery.”
The MCAS, introduced with the launch the 737 MAX 8 in May 2017, was the result of an effort to equip the new model with larger and more fuel-efficient engines. These were placed further forward and higher on the wing, altering the aircraft’s balance. This resulted in the plane’s nose pitching upwards in certain circumstances.
To solve the problem, Boeing added the MCAS flight-control system, which automatically pushed the aircraft’s nose down when a sensor indicated the plane was at risk of stalling.
The MCAS is designed to only activate when the wing flaps are retracted after take-off and the aircraft has gained altitude. However, it is speculated this system may have played a part in both accidents.
Following the Lion Air crash in October 2018, which killed 189 people, it was reported that the addition of the MCAS flight-control system had not been adequately explained to pilots, possibly making them ill-prepared if it were to activate during flight. At the time, Boeing denied the company had “intentionally withheld” information about the new system.
According to digital aviation publication Air Current, citing an internal Boeing memo, company CEO, Dennis Muilenburg told staff the “relevant function of MCAS is described in the Flight Crew Operations Manual.”
“We routinely engage with customers about how to operate our airplanes safely,” Muilenburg said in the memo, according to an Air Current report.
But pilots flying the aircraft for SouthWest Airlines were reported to have been told that it was likely they would never see the system at work as it operates in situations where the aircraft is under relatively high load and near stall.
Air Current, citing a Q&A document provided to pilots at SouthWest Airlines, said staff were told this was why “Boeing did not include an MCAS description in its Flight Crew Operations Manual”. In the wake of the Lion Air crash, Boeing stepped up its efforts to make pilots familiar with the new system, but the relations between to two companies soured, with Lion Air threatening to cancel billions of dollars of orders.
By the end of January this year, Boeing had delivered 350 of the new jets to customers, with another 4,661 on order.