LATAM 787 Sudden Drop due to 'Technical Incident'

[Evan]

Our definitions are not aligned.

That seat moves pretty fast. Probably 2-3 seconds from where he was to the full forward position.

[Gabriel]

rapidly

Our definitions are not aligned.

[Evan]

Some further clues here:

In a message to 787 jet operators that was sent late Thursday, Boeing said it was advising of a “known condition related to a loose/detached rocker switch cap” located on the seat back of the captain’s and first officer’s seats but did not say whether the switch covers had played a role in the incident on the Latam plane.
“Closing the spring-loaded seat back switch guard onto a loose/detached rocker switch cap can potentially jam the rocker switch, resulting in unintended seat movement,” Boeing said.

The memo, a copy of which was reviewed by The New York Times, pointed to the 2017 letter, which noted the installation of adhesive to the rocker switch caps “to prevent the caps on the rocker switches from detaching and/or becoming loose.”
Boeing recommended all operators of 787 planes to inspect the four rocker switches and rocker switch caps on the seats.
The Wall Street Journal first reported that Boeing had sent the memo to airlines.
In a note to its 787 flight crews, American Airlines said it had “identified a potential hazard” with the horizontal power control switches on the top back of pilot seats.
The note, which was reviewed by The Times, said that the airline’s technology operations team “will be ensuring that these switches are properly secured” and asked 787 captains “to brief all pilots, flight attendants and flightdeck jumpseat riders on your flight of the importance of not using the switch on the top back of the pilot seat when the seat is occupied.”

Why do I think that a condition in which the pilot seat could unexpectedly and rapidly advance into the control column might be a prime candidate for a mandatory compliance airworthiness directive?

I realize that hindsight is 20/20, but why does foresight have to be -8 with astigmatism?

[3WE]

It’s a completely different kind of pitch trim switch.

Electric motor works a mechanical linkage to a control surface…arguably conventional setup…(yes, the font might be a tad blue.)

[Evan]

It's a completely different kind of MCAS

It’s a completely different kind of pitch trim switch.

[Evan]

The 787 has an additional seat track switch hidden under a plastic flap on the top of
the seat back. If that flap is missing or is stuck in the open position, I can easily see how a FA can inadvertently hit it while bracing a hand against the seat back. If this happened, I would expect an emergency AD requiring inspection of this flap guard.

In the longer-term, I would require a modification that disables this switch when the pilot is seated.

[Gabriel]

It's a completely different kind of MCAS, altogether.

It's a completely different kind of MCAS

[Evan]

SUPPOSEDLY:

Hostie brings pilots “the fish.”

They bump a guarded switch on the back of the pilot seat.

The pilot seat begins moving forward.

Shoves the pilot into the control column.

Dive ensues.

Commentary:

It’s a completely different kind of MCAS, altogether.

IF TRUE:

I take back my expectation about a deep dive into 787 systems. This is pathethic.

[3WE]

SUPPOSEDLY:

Hostie brings pilots “the fish.”

They bump a guarded switch on the back of the pilot seat.

The pilot seat begins moving forward.

Shoves the pilot into the control column.

Dive ensues.

Commentary:

It’s a completely different kind of MCAS, altogether.

[Evan]

I'm guessing those questions are rhetorical, but for the avoidance of doubt: Yes and yes. The info is in the text of the updated AD I provided a link to earlier. I know it's not an easy read, but pulling out the relevant parts:

A. The unsafe condition is described thus:

The FAA is issuing this AD to address deficiencies in the FCM software that could prevent continued safe flight and landing; to prevent unrealistic, sudden drops in displayed airspeed at high actual airspeed, which could lead to pilot control inputs that could exceed the structural capability of the airplane; to prevent simultaneous resets of all three FCMs, which could result in flight control surfaces not moving in response to flight crew inputs for a short time and consequent temporary loss of controllability; and to address potential unannunciated dual symmetric inboard slat skew, which can result in adverse handling characteristics of the aircraft.

B. There are three approved fixes:

(1) Use the onboard data load function (ODLF) to install FCM Block Point 3 software.
(2) Use the ODLF to install FCM Block Point 4 software.
(3) Install any later FAA-approved FCM software version using an approved method

C. The compliance date for applying one of those three fixes is:

Within 6 months after August 20, 2015

So this doesn't add up. Unless LATAM hasn't done a ODLF update in almost nine years! That's unpossible...

But while we're here:

The FAA is issuing this AD to address deficiencies in the FCM software that could prevent continued safe flight and landing; to prevent unrealistic, sudden drops in displayed airspeed at high actual airspeed, which could lead to pilot control inputs that could exceed the structural capability of the airplane;

Sudden, unrealistic drops in airspeed are considered unreliable by competent pilots. The first order of business is to cross-check and if all three are in agreement, declare unreliable airspeed (most likely pitot icing), maintain current pitch and power settings, and work the QRH. A competent pilot will not respond to this by making 'pilot control inputs that could exceed the structural capability of the airplane' (or stall it). After AF447, hopefully this routine is well-rehearsed.

I would be more concerned about sudden unrealistic (yet still ruled valid) drops in airspeed effecting the avionics and the autoflight and/or gust suppression.

[flashcrash]

But wasn’t that ‘bug’ also discovered many years ago? Hasn’t Boeing done anything to remove it?

I'm guessing those questions are rhetorical, but for the avoidance of doubt: Yes and yes. The info is in the text of the updated AD I provided a link to earlier. I know it's not an easy read, but pulling out the relevant parts:

A. The unsafe condition is described thus:

The FAA is issuing this AD to address deficiencies in the FCM software that could prevent continued safe flight and landing; to prevent unrealistic, sudden drops in displayed airspeed at high actual airspeed, which could lead to pilot control inputs that could exceed the structural capability of the airplane; to prevent simultaneous resets of all three FCMs, which could result in flight control surfaces not moving in response to flight crew inputs for a short time and consequent temporary loss of controllability; and to address potential unannunciated dual symmetric inboard slat skew, which can result in adverse handling characteristics of the aircraft.

B. There are three approved fixes:

(1) Use the onboard data load function (ODLF) to install FCM Block Point 3 software.
(2) Use the ODLF to install FCM Block Point 4 software.
(3) Install any later FAA-approved FCM software version using an approved method

C. The compliance date for applying one of those three fixes is:

Within 6 months after August 20, 2015

[Evan]

I tend to believe him. Maybe not that he lost control, what I heard him say was the the pilot told him that he lost all instruments for a few seconds and then all came back. I can see how critical sensor information going "blank" for a few seconds can disable the instruments and the flight controls at the same time (in a fully FBW plane), since these sensor info are critical inputs for both the digital instruments and the flight control computers / FBW laws.

Not much evidence, but:
- The pax said he was surprised himself that the pilot told him that.
- Rumors that all 3 flight control computers self-rebooted at the same time.
- Rumors regarding existing procedures and AD's related to this, that include actions to reboot different systems every X hours, days or cycles, to prevent overflow errors.

Crazy stuff.

But wasn’t that ‘bug’ also discovered many years ago? Hasn’t Boeing done anything to remove it? I mean, a vulnerability like that is not tolerable in anything you might want to call ‘airworthy’.

In the hands of a lesser crew… remember, a sudden loss of FCC’s caused (led to) the upset, stall and crash of an AirAsia A320.

[BoeingBobby]

RUMOR is, A pilot never ever ever ever ever ever talks to ANYBODY. Until you have spoken to your Union representative and of course you are going to be talking to the chief pilot.

[Gabriel]

Let's see, I'm pretty damn sure that there is an announcement about keeping your belt fastened while seated. That the pilot "supposedly" told one of the passengers that he "lost control of the aircraft for a moment" is dubious at best.

I tend to believe him. Maybe not that he lost control, what I heard him say was the the pilot told him that he lost all instruments for a few seconds and then all came back. I can see how critical sensor information going "blank" for a few seconds can disable the instruments and the flight controls at the same time (in a fully FBW plane), since these sensor info are critical inputs for both the digital instruments and the flight control computers / FBW laws.

Not much evidence, but:
- The pax said he was surprised himself that the pilot told him that.
- Rumors that all 3 flight control computers self-rebooted at the same time.
- Rumors regarding existing procedures and AD's related to this, that include actions to reboot different systems every X hours, days or cycles, to prevent overflow errors.

Crazy stuff.

[BoeingBobby]

Well, he also told him it was his first day and promised that he would get the hang of it.