Following the news on Boeing’s 737 MAX 8 erroneous AOA sensors bulletin, the list of all forty airlines that operate the aircraft already began circulating in the media. But the speculation surrounding the manufacturer’s safety bulletin and the airlines affected only touches upon the surface, and here is why.

It became known on November 7, 2018, that the previous day, Boeing had issued a bulletin to operators of the 737 MAX 8 aircraft, warning them to stick to procedures in case a plane experiences problems with AOA (Angle of Attack) sensors. This malfunction can cause such dangers as difficulty in controlling an airplane, excessive nose-down attitude, significant altitude loss, or, eventually, a crash.

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In the wake of Lion Air Flight JT610 crash investigation, Boeing issues a bulletin, warning MAX aircraft operators about erroneous Angle of Attack (AOA) sensors input and safety procedures in this case.
 

The bulletin, in which the 737 MAX’s manufacturer urges to follow “existing flight crew procedures” in order to “address circumstances where there is erroneous input from an AOA sensor” was issued in relation to an ongoing Lion Air Flight JT610 crash investigation.

In particular, once the attention shifted to the aircraft model after it became known that:

  1. The crashed plane was brand new - delivered two months before and having logged only 800 flying hours at the time of the crash.

  2. It had experienced problems with its AOA sensors and had them changed a day before the crash.

Now, the media is counting other Boeing MAX 8 operators - there are 40 of them. The underlying message here is, presumably, that they operate “unsafe” aircraft. But the situation is much more complex - both in and against Boeing’s benefit.

So speculation surrounding MAX 8 safety also casts a shadow of doubt on other planes of the family, one of which - the MAX 7 - is to enter service within months (in January 2019).

In its safety release, Boeing stresses exclusively that it is a standard practise for the manufacturer to issue bulletins or recommendations of its aircraft operations. The bulletin in question, it claims, directs “operators to existing flight crew procedures”. In other words, telling them to do what they already know they should do (hence, gently suggesting a possible “human mistake” in light of the JT610 crash). The fact that AOA sensors were changed before the fatal flight also works in Boeing’s favor.

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Now that the black box of the Lion Air Boeing 737-8 MAX has been found, the investigation will try to determine why a months-old plane would crash into the sea minutes after takeoff. While the data is being recovered, several details surrounding PK-LQP already emerged.
 

But here is where the situation get complicated. MAX 8 is part of the new generation of Boeing 737 MAX family; the problem is, the aircraft in this this family are known to be very similar.

For instance, while introducing MAX 10 landing gear, Boeing’s description reads: “From an engineering standpoint, this new airplane will be a straightforward stretch of the MAX 9, which entered service in 2018. More than 95 percent of the design and 90 percent of the build of the MAX 10 will be identical to previous models. The primary difference in the MAX 10 compared to other models is in the new, levered design of the main landing gear”.

So speculation surrounding MAX 8 safety also casts a shadow of doubt on other planes of the family, one of which - the MAX 7 - is to enter service within months (in January 2019).

Swiftly responding to Boeing safety bulletin, on November 7, 2018, the U.S. Federal Aviation Administration (FAA) issued an emergency airworthiness directive. In it, the authority orders flight crews to comply with the operating procedures manual, thus re-affirming Boeing’s position. But here’s the catch: the directive addresses both MAX 8 and MAX 9 aircraft, and is, accordingly, sent to operators of both models.

Boeing declined AeroTime’s emailed request to clarify whether AOA sensors on MAX 8 and other MAX family planes are the same.