Giant US aerospace and defence group Boeing has announced that it has concluded the development of updated software for its 737 MAX single-aisle airliner type, as well as the associated simulator testing and engineering flight test. The updated software is for the 737 MAX’s Manoeuvring Characteristics Augmentation System (MCAS).
The MCAS has been implicated in two 737 MAX crashes in just five months, in late 2018 and early 2019, that killed a total of 346 people. Boeing reported that it has, to date, flown the 737 MAX with the updated MCAS software on 207 flights totalling more than 360 hours.
The company added that it was providing the US Federal Aviation Administration (FAA) with further information which the regulator has requested. This includes information on the interaction between pilots and the flight controls and displays in various flight scenarios. Once this has been done, Boeing will cooperate with the FAA to schedule the certification test flight and present its documentation for final certification.
“With safety as our clear priority, we have completed all the engineering test flights for the software update and are preparing for the final certification flight,” affirmed Boeing chairperson, president and CEO Dennis Muilenburg. “We’re committed to providing the FAA and global regulators with all the information they need, and to getting it right.”
The group has also created improved educational and training materials that are now being evaluated by the FAA and regulators in other countries, as well as by customer airlines. These are to support the return to service and subsequent operations of the 737 MAX. Part of this is a number of regional conferences that are being held around the globe.
“We’re making clear and steady progress and are confident that the 737 MAX with the updated MCAS software will be one of the safest airplanes ever to fly,” he assured. “The accidents have only intensified our commitment to our values, including safety, quality and integrity, because we know lives depend on what we do.”
The 737 MAX is the fourth generation of its hitherto renowned 737 single-aisle airliner family. The previous generations were the original models – the 737-100 and 737-200; the classic models– the 737-300, 737-400 and 737-500; and the next-generation (NG) models – the 737-700, 737-800 and 737-900ER.
The MCAS was developed for the 737 MAX series, because this has different aerodynamic characteristics to all previous 737 types. The 737 MAX is powered by two CFM LEAP-1B engines, which are the biggest power plants ever fitted to the 737. The LEAP-1B has a fan diameter of 69 inches (175 cm), whereas the CFM56-7B engine, which powers the 737NG family, has a fan diameter of 61 inches (155 cm). For reasons that go back to the original design of its original model in the early 1960s, the 737 has a relatively short undercarriage and the LEAP-1B, unlike all previous power plants, could not be fitted under the aircraft’s wing (even with the MAX being given a longer nose wheel strut). So new pylons had to be designed, which position the LEAP-1B engines further forward and higher than the CFM56-7B engines on the 737 NG. This affected the thrust line of the engines, and moved the aircraft’s centre of gravity forward.
The result was that, in certain circumstances, the nose of the aircraft could pitch up. The MCAS was developed to automatically counteract any such pitch-up, the system relying on angle-of-attack sensors to ascertain the aircraft’s attitude. If the angle of attack became too great, threatening to stall the aircraft, the MCAS would activate flight controls to push the aircraft’s nose down. This would be done without any input from the flight crew. Until after the first of the 737 MAX crashes, pilots flying the aircraft had no idea that the MCAS existed.