All 737 Max aircraft worldwide are grounded.
The FAA informs CNN that they received the four submissions to the hotline on April 5 and may have a completely new perspective on what went wrong in the crashes of two Boeing 737 Max airliners – Lion Air Flight 620 in October and Ethiopian Air Flight 302 in March.
The complaints include a previously unknown problem in which the wiring of the angle of attack sensor was damaged by a foreign body to the source.
Boeing reportedly had problems with foreign body waste in its manufacturing process; The New York Times reported that metal shavings were found near the wiring of Boeing 787 Dreamliner aircraft, and the Air Force halted delivery of the Boeing KC-46 tanker after some debris was found on some aircraft.
Other whistleblower reports raise concerns about the MCAS control triggers, which shut down the MCAS software according to the source.
A preliminary report Ethiopian investigators found that a sensor for a faulty incidence of flight 302 of the Ethiopian Airlines was sending false data to the MCAS system. The MCAS, behaving like a stable, repeatedly pushed the nose of the plane down while the pilots fought for control and eventually crashed the plane.
The problems aboard the Ethiopian Airlines plane seem similar to those of the Lion Air flight, which crashed in October. Between the two crashes 346 people were killed.
The CEO of Boeing has recognized the role of the erroneous angle of attack angle that triggered the MCAS system in the two crashes crashes.
MCAS is triggered by a single-angle sensor, and critics have asked why Boeing would design the aircraft without redundancy and why the FAA approved the system.
In a statement, the FAA defended its certification
"Safety is a top priority at the FAA, and we have a long-established aircraft certification process that has always produced safe aircraft," the FAA statement told CNN. "When certifying an aircraft, we do not consider a single factor as isolated, instead we look at the interaction of all elements and systems alongside human and other external factors."
"The single-angle sensor has been considered in terms of a variety of other factors, in particular, well-known pilot schemes that would mitigate the effects of a failure. MCAS design, certification testing and cockpit procedures have been evaluated using a standard industry standard error analysis approach. "
Boeing did not respond immediately to a request for comment on whistleblowers.
The airline's CEO will hold a press conference on Monday after a shareholder meeting in Chicago and a meeting of international civil aviation authorities on Monday in the Dallas area to discuss the issues surrounding the 737 Max.