Boeing says the 737 Max is based on software, not hardware

US government test pilots who have conducted various flight scenarios for the Boeing 737 Max in recent weeks have revealed a potential ground plane failure, but the builder and industry insiders claim that it is a software rather than a hardware failure.

The aircraft's flight system attempted to lower the nose of the aircraft several times during simulator tests, motivated by incorrect flight data, Bloomberg reported Saturday. The Federal Aviation Administration (FAA), the US regulator, concluded that pilots may not have enough time to react and avoid a tragedy in a real scenario.

This flaw, revealed by the FAA last month, created additional uncertainty as to when Boeing's best-selling aircraft will be put back into service and prompted engineers to find a solution.

We are confident that there is a software update and not a hardware update. This is a good update and we are doing it.

Dennis Muilenburg, Managing Director Boeing

The failure triggered several aggressive moves to lower the nose of the aircraft, which alarmed the FAA pilots and other officials, but the dive motion was not caused by a computer problem, said Bloomberg.

This confirms Boeing's claims that it can solve problems with a software change.

"We are confident that it is a software update, not a hardware update," said Dennis Muilenburg, Boeing's chief executive officer on Wednesday. "It's an update, and we're doing it."

The 737 Max has been stuck worldwide since March after the model was involved in two fatal crashes in Ethiopia and off the Indonesian coast in the space of five months. Muilenburg said Boeing could develop a software patch by the end of September, but warned that the timing remains uncertain. The FAA, which must approve all the solutions under the spotlight of the 737 Max investigations,

did not set a deadline or accept Boeing's badessment that software changes alone would be sufficient.

Bloomberg, citing informed sources on the flight tests, provided more details on this failure.

A wing at the tail of the Boeing jet, known as the horizontal stabilizer, was turning to lower the nose, he said. This same scenario occurred during the two fatal accidents when a safety device known as the Manning Enhancement System (MCAS) was activated during a malfunction.

But the problem recently discovered was not triggered by MCAS, according to Bloomberg. Instead, it was triggered by several erroneous data streams in a flight computer that occurred simultaneously. It was simulated during tests even though it was never demonstrated that it occurred in flight.

It is common to say that pilots would mitigate the risks badociated with a malfunction, but that's partly for that reason that the FAA initially approved MCAS, a controversial decision being examined by the US Congress and other panels. Although it was possible for the pilots of the two fatal accidents to neutralize the MCAS, they could not do so.

When the last computer crash discovered began to reduce the nose in the recent test, it was more difficult than expected for the test drivers to thwart.

Another source could not confirm that faulty data flows triggered the dive movements.

One of the ways pilots learn to react to what's called the computer problem is to activate switches on the control column moving the horizontal stabilizer. This could compensate for the malfunction, even temporarily, so that pilots have more time for other emergency actions.

The use of trim switches to stop the movement of the horizontal stabilizer proved difficult, even though the test pilots were able to react to the failure and keep control. As a result, they concluded that a typical driver might not be able to react adequately.

According to the Bloomberg report, a new hotfix can be designed to monitor the computer to detect this very unusual condition and prevent the stabilizer from moving when it occurs.