Boeing Official Played Down Scenario That May Have Doomed Ethiopian Jet
Talking to pilots, executive suggested sensor troubles could be nuisance rather than serious hazard
By Alison Sider and Andy Pasztor
Updated May 21, 2019 11:59 a.m. ET
Four weeks after faulty sensor data led a 737 MAX jet to crash in Indonesia last year, a high-ranking Boeing Co. BA 1.69% executive raised and dismissed the possibility of a bird collision triggering a similar sequence of events that could cause a second accident.
U.S. aviation authorities increasingly believe that a version of that scenario, described by Boeing executive Mike Sinnett at a November meeting with American Airlines pilots, may have led to the Ethiopian Airlines crash nearly four months later, according to officials familiar with the details. The crash happened after a sensor sent faulty data—possibly due to a bird strike—causing an automated flight-control system known as MCAS to misfire and repeatedly push the nose of the plane down.
At the meeting, Mr. Sinnett, vice president of product strategy, expressed confidence that well-trained pilots following established procedures could safely respond to a potential repeat of such equipment trouble, according to a recording of the meeting, which was reviewed by The Wall Street Journal. He also said he felt “absolutely” confident that heightened pilot awareness of potential dangers further reduced the chances of another accident.
Now, Ethiopian Airlines is pushing back against criticism of its pilots by complaining the plane maker didn’t do enough to warn them. The carrier suggests that Boeing’s failure to provide functioning cockpit alerts about problems with sensors made it more difficult for the Ethiopian crew to recognize the hazards they confronted before the second MAX accident in March.
The plane’s computers received erroneous data from a sensor known as an “angle of attack” or AOA vane about the pitch of the aircraft’s nose, activating a system that strongly pushed down the nose and ended in a fatal, high-speed dive.
“Although the pilots followed the procedures” spelled out by Boeing and U.S. safety regulators to counteract the automated commands, “none of the expected warnings appeared in the cockpit, which deprived the pilots of necessary and timely information,” Ethiopian Airlines said Friday.
Cockpit alerts such as a speed indicator and a stall warning called the “stick shaker”—which vibrates the pilot’s controls—did activate during the flight, according to a preliminary report issued by the Ethiopian government. But an indicator warning that the AOA sensors were out of sync didn’t go off, and excerpts from the cockpit voice recorder released as part of the preliminary report also indicate that despite those clues, it took the crew about five minutes to realize the AOA sensor problem.
U.S. aviation authorities regard a collision with one or more birds as the most likely reason for trouble with the sensor, according to industry and government officials familiar with the details of the crash investigation.
In his discussion with the American pilots months earlier, Mr. Sinnett raised the possibility of a bird hitting or damaging a sensor on a MAX jet shortly after takeoff. But he then appeared to play down the resulting risks, suggesting that pilots could quickly resolve such a situation and that the result of relying on what are called AOA alerts could be nothing more than the nuisance of flying back to the departure airport.
“The vast majority of AOA problems come from bird strikes after the airplane departs,“ Mr. Sinnett said. “You don’t want to have to return to base after a bird strike on an AOA vane.”
Ethiopian crash investigators said in a preliminary report that they “found no evidence of foreign-object damage” on the sensor. The point was reiterated last week in the airline’s statement, which specifically said no evidence of a bird strike has been found.
When birds hit such sensors, it is often difficult to find evidence conclusively proving that is what occurred.
U.S. government and industry safety experts, however, have said information downloaded from “black box” flight-data recorders points strongly to a sensor that was sheared off or otherwise rendered inoperable shortly after takeoff.
A Boeing spokesman declined to comment.
The October crash of the Lion Air jet in Indonesia and the Ethiopian crash in March took a total of 346 lives. The global fleet of 737 MAX aircraft has been grounded since shortly after the second crash.
Whatever caused the faulty data on the Ethiopian jet, Boeing has been on the defensive about its onboard alerting system. Alerts to inform pilots whether such sensors are transmitting incorrect data haven't been working on much of the global MAX fleet due to a software error stretching back to production, though they did function on American’s planes.
Despite the criticism of Boeing by Ethiopian Airlines, acting FAA chief Daniel Elwell last week said that the pilots of the Ethiopian jet didn’t fully adhere to required procedures. He also told a House aviation panel that the agency concluded working alerts “wouldn’t have changed either accident.”
Some pilots and safety experts disagree with his conclusion.
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