B737 MAX airliners continue to accumulate at Boeing Field while the type remains grounded.
Last month Boeing hit back strongly in comments about industry criticism on the AOA (angle of attack) disagreement information. “On every aircraft delivered to our customers, including the MAX, all flight data and information needed to safely operate the aircraft is provided in the flight deck on the primary flight deck displays. This information is provided full-time in the pilots’ primary field of view, and it always has been,” said the manufacturer.
“Airspeed, attitude, altitude, vertical speed, heading and engine power settings are the primary parameters the flight crews use to safely operate the aircraft in normal flight. Stick shaker and the pitch limit indicator are the primary features used for the operation of the aircraft at elevated angles of attack.
“All recommended pilot actions, checklists, and training are based upon these primary indicators. Neither the angle of attack indicator nor the AOA Disagree alert is necessary for the safe operation of the aircraft. They provide supplemental information only, and have never been considered safety features on commercial jet transport aircraft.”
The Boeing design requirements for the B737 MAX included the AOA Disagree alert as a standard, standalone feature. In 2017, within several months of beginning B737 MAX deliveries, engineers at Boeing identified that the B737 MAX display system software did not correctly meet the AOA Disagree alert requirements. The software delivered to Boeing linked the AOA Disagree alert to the AOA indicator, which is an optional feature on the MAX and the NG. Accordingly, the software activated the AOA Disagree alert only if an airline opted for the AOA indicator.
When the discrepancy between the requirements and the software was identified, Boeing followed its standard process for determining the appropriate resolution of such issues. That review, which involved multiple company subject matter experts, determined that the absence of the AOA Disagree alert did not adversely impact aircraft safety or operation. Accordingly, the review concluded, the existing functionality was acceptable until the alert and the indicator could be delinked in the next planned display system software update.
Senior company leadership was not involved in the review and first became aware of this issue in the aftermath of the Lion Air accident.
About a week after the Lion Air accident, on 6 November 2018, Boeing issued an Operations Manual Bulletin (OMB) which was followed a day later by the FAA’s issuance of an AD. In identifying the AOA Disagree alert as one among a number of indications that could result from erroneous AOA, both the OMB and the AD described the AOA Disagree alert feature as available only if the AOA indicator option is installed.
Boeing is issuing a display system software update to implement the AOA Disagree alert as a standard, standalone feature before the MAX returns to service. All MAX production aircraft will have an activated and operable AOA Disagree alert and an optional angle of attack indicator. All customers with previously delivered MAX aircraft will have the ability to activate the AOA Disagree alert.
Media are now reporting the changes are looking acceptable to airline operators. Airline Ratings says, in a major endorsement of the B737 MAX changes, that the world’s largest pilots’ union will not ask the FAA to require additional mandatory simulator training on the MCAS scenarios before pilots can fly the aircraft again.
According to Aviation Week, ALPA will just recommend scenario training as part of routine recurrent training and that ALPA “will make its views known in comments on a draft of proposed minimum B737 MAX training standards out for public comment. The Flight Standardization Board (FSB) draft report does not recommend simulator sessions as part of transition training for B737 Next Generation pilots upgrading to the B737 MAX, opting for less costly computer-based training instead.”
But it adds: “A person with knowledge of ALPA’s comments tells Aviation Week that the pilots’ union will go a step further, calling for hands-on simulator training at the earliest scheduled opportunity.
“Some regulators are expected to require simulator training as conditions for removing their operations bans, and Air Canada has said it is already using its MAX simulator—the only one in airline hands in North America—to run its 420 MAX pilots through MCAS-related scenarios.”
When Fiji Airways was recently asked how it was coping with its two B737 MAX 8s out of the air, the airline said like everyone it was awaiting the outcome of all the Boeing updates and regulatory approvals. Fiji Airways is managing with its existing fleet plus a Miami Air B737-800 on wet lease.
- Report by John King.