The New York Times published an article a few hours ago about the TK1951 crash in 2009 titled "How Boeing’s Responsibility in a Deadly Crash ‘Got Buried’". I remember the Turkish side claiming some of the things mentioned in the article but these objections were treated as biased.https://www.nytimes.com/2020/01/20/business/boeing-737-accidents.html
After a Boeing 737 crashed near Amsterdam more than a decade ago, the Dutch investigators focused blame on the pilots for failing to react properly when an automated system malfunctioned and caused the plane to plummet into a field, killing nine people.
The fault was hardly the crew’s alone, however. Decisions by Boeing, including risky design choices and faulty safety assessments, also contributed to the accident on the Turkish Airlines flight. But the Dutch Safety Board either excluded or played down criticisms of the manufacturer in its final report after pushback from a team of Americans that included Boeing and federal safety officials, documents and interviews show.
"Turkish Airlines disputes crash inquiry findings on stall recovery"http://archive.is/steYU
But cockpit-voice recorder analysis shows that the captain also called that he was taking control, just as the thrust levers had been pushed halfway forward. "Assumingly, the result of this was that the first officer's selection of thrust was interrupted," says the final report into the crash.
Crucially, as the first officer relinquished the thrust levers to hand over control, the still-engaged autothrottle immediately retarded them again to the idle position.
"Directly thereafter, the autothrottle was disengaged," says the inquiry report. "But for a period of seven seconds the thrust levers were not moved forwards from the idle position."
While the investigation could not determine whether the captain had placed his hands on the thrust levers, it says that nine seconds passed between the activation of the stick-shaker and the movement of the thrust levers to maximum.
By this point the aircraft had already stalled and the remaining height of 350ft was "insufficient for the recovery procedure", it adds.
Turkish Airlines says the autothrottle "kicked back unexpectedly" and that Boeing "had not mentioned", in its documentation, a need to disconnect the autothrottle during the procedure.
The carrier also describes the relationship between the left-hand radio altimeter and the autothrottle as "error-prone", adding that it was not explained in Boeing's documentation for flight crews until after the crash.
While acknowledging that disengagement of the autothrottle is not described in the recovery procedure, the Dutch Safety Board highlights the problems of incomplete knowledge of the aircraft's interdependent systems. It points to the crew's suffering from "automation surprise" with respect to the autothrottle's behaviour - during both the original loss of thrust on approach and the attempted stall recovery.
Turkish Airlines also claims that simulator tests show that a height of at least 500ft is required for the 737-800 to recover successfully from a stall, and that the ill-fated jet was already below this level when the pilots initiated the recovery procedure.