Another Boeing document warned that if a pilot failed to respond in more than 10 seconds to the software, activation could lead to a "catastrophic" failure.
In both fatal crashes, faulty data from one of two angle-of-attack sensors, which measure the pitch of the plane against the oncoming stream of air, caused the MCAS to drive down the jet's nose, which pilots struggled to counteract before ultimately entering a fatal dive.
"Boeing has not told the whole truth to this committee and to the families and to the people looking at this ... and these families are suffering because of it", a visibly angry Duckworth said as she pointed to relatives of passengers who died. Muilenburg mentioned the corporate had repeatedly requested the identical query.
"The design and certification of the MCAS did not adequately consider the likelihood of loss of control of the aircraft", the report mentioned. On the contrary, Muilenburg boasted in his written testimony that when the 737 Max returns to service, it will be one of the safest airplanes ever to fly. It'll take knowledge from the assault sensors and never let MCAS activate greater than as soon as earlier than a scenario has been resolved.
DeFazio also questioned why Boeing scrapped initial plans to install an MCAS "annunciator" alert and how pilots could be expected to recover if the system failed, when Boeing failed to disclose details on MCAS system to pilots. You said you're accountable.
"I've talked to a lot of pissed off pilots", DeFazio said.
"We need answers. We need reforms on how commercial aircraft are certified", and how manufacturers like Boeing "are watched" by regulators, he added.
Asked about whether Boeing supported a new legislation on the oversight process, Muilenburg declined to give a clear backing.
Muilenburg shortly listed Boeing's failure to reveal for months that it had made elective a cockpit alert flagging disagreement between the airflow sensors. And finally he said the company should have been more "efficient and comprehensive" in its communications and documentation "across all of our shareholders".
The company's development and assumptions around a key flight control system known as MCAS - at the center of twin crashes in Ethiopia and Indonesia - also took front and center at the hearing.
The two accidents killed 346 people and have thrown the company into crisis and roiled the global aviation industry.
An worldwide panel of safety regulators reported this month that the FAA outsourced its regulatory tasks to Boeing employees for 737 Max's safety, and Boeing put "undue pressures" on its employees working on 737 Max certification. Boeing did not comment Tuesday on the allegation.
Muilenburg told reporters he believes the allegation was in response to concerns about a change in the increase of the production rate.
"We need to know if Boeing and the FAA rushed to certify the Max", Wicker said.
About 20 relatives of crash victims attended Tuesday's Senate hearing, and Commerce Committee Chairman Roger Wicker opened the session by promising them that the inquiry would get to the bottom of what went wrong. "It was tough to hear", he mentioned, including the corporate was making "the fixes we need to make". "We're improving and we're learning", he mentioned.
On Tuesday, U.S. senators expressed dismay that 2016 instant messages discussing erratic behaviour of simulator software - a replica of the system aboard the jetliner - did not prompt an immediate reaction from the company.
Multiple lawmakers questioned Muilenburg on decisions to remove information on the MCAS system from the pilot training materials for the 737 Max as well as whether concerns about profit motivated the company to make decisions to reduce costs for production or additional training for pilots.
In his opening statement on Wednesday, before the House Committee on Transportation and Infrastructure, Muilenburg apologized to the family members of the victims who were in attendance.
Muilenburg said that he hasn't offered to resign, and that it's up to the company's board to decide whether to dock his pay. Multiple senators asked Mr Muilenburg to address families of crash victims seated behind him.