Boeing 737 e 737 MAX

[Damynavy]

https://www.seattletimes.com/business/boeing-aerospace/black-box-data-reveals-lion-air-pilots-struggle-against-boeings-737-max-flight-control-system/

...mysteriously they didn’t do what the pilots on the previous day’s flight had done: simply switched off that flight-control system.

Modificato 28 Novembre 2018 da Damynavy

[Felis]

4 ore fa, Damynavy scrive:

https://www.seattletimes.com/business/boeing-aerospace/black-box-data-reveals-lion-air-pilots-struggle-against-boeings-737-max-flight-control-system/

...mysteriously they didn’t do what the pilots on the previous day’s flight had done: simply switched off that flight-control system.

Allucinante. Soprattuto preoccupante per la lacunosa formazione dei piloti. Che tu sappia l'A320 che ha un sistema analogo di anti stallo è fatto meglio?

[Damynavy]

9 ore fa, Felis scrive:

Allucinante. Soprattuto preoccupante per la lacunosa formazione dei piloti. Che tu sappia l'A320 che ha un sistema analogo di anti stallo è fatto meglio?

Sono simili. Non saprei dire quale dei due sistemi sia meglio.

Nel Bus è più automatizzato (imposto l'autotrim, pesi, centraggio ecc. e fa tutto "lui", non lo tocco più), in Boeing danno una maggiore "libertà" (di gestione) ai piloti.

 

Le emergenze, sono il problema.

 

L'equipaggio deve conoscere il sistema e intervenire in determinate situazioni.

Evitando (possibilmente) di fare c@zzate.

 

 

 

Modificato 28 Novembre 2018 da Damynavy

[Damynavy]

17 ore fa, Damynavy scrive:

 

 

L'equipaggio deve conoscere il sistema e intervenire in determinate situazioni.

Evitando (possibilmente) di fare c@zzate.

 

 

 

https://www.corriere.it/cronache/18_novembre_28/aereo-caduto-indonesia-piloti-hanno-tentato-26-volte-salvarsi-1f16000c-f313-11e8-bf1c-39c2f2f9623f.shtml

 

Non sappiamo se questo è lo scenario...sono indiscrezioni.

Ma mi riferivo a questo (possibilmente non fare c@zzate).

Come mi diceva sempre, uno dei miei primi istruttori: "non devi inseguire la macchina, ci ammazziamo...".

 

Questi lo hanno fatto per 26 volte.

 

 

-Il dossier si spinge anche a raccomandare alla compagnia aerea low-cost, tra le più grandi del mondo, ad "aumentare la cultura della sicurezza e di mettere il pilota in grado di prendere misure appropriate sul prosieguo del volo"-.

 

 

-In ogni caso secondo diversi esperti comandante e primo ufficiale sono addestrati e dovrebbero conoscere questo tipo di intervento d’emergenza-

Modificato 29 Novembre 2018 da Damynavy

[Felis]

1 ora fa, Damynavy scrive:

https://www.corriere.it/cronache/18_novembre_28/aereo-caduto-indonesia-piloti-hanno-tentato-26-volte-salvarsi-1f16000c-f313-11e8-bf1c-39c2f2f9623f.shtml

 

Non sappiamo se questo è lo scenario...sono indiscrezioni.

Ma mi riferivo a questo (possibilmente non fare c@zzate).

Come mi diceva sempre, uno dei miei primi istruttori: "non devi inseguire la macchina, ci ammazziamo...".

 

Questi lo hanno fatto per 26 volte.

 

 

-Il dossier si spinge anche a raccomandare alla compagnia aerea low-cost, tra le più grandi del mondo, ad "aumentare la cultura della sicurezza e di mettere il pilota in grado di prendere misure appropriate sul prosieguo del volo"-.

 

 

-In ogni caso secondo diversi esperti comandante e primo ufficiale sono addestrati e dovrebbero conoscere questo tipo di intervento d’emergenza-

Sì. Il fatto che non abbiano disattivato il sistema dopo poco (il cui switch off mi pare sia in zona pedaliera, perchè proprio lì! ?‍♂️ ) è allucinante. Possibile che non sapessero dell'esistenza di quel comando?! Non devono conoscere il velivolo nella totalità dei comandi e procedure?

[Damynavy]

9 ore fa, Felis scrive:

Sì. Il fatto che non abbiano disattivato il sistema dopo poco (il cui switch off mi pare sia in zona pedaliera, perchè proprio lì! ?‍♂️ ) è allucinante. Possibile che non sapessero dell'esistenza di quel comando?! Non devono conoscere il velivolo nella totalità dei comandi e procedure?

Sul MAX dovrebbe essere sempre lì...

 

Modificato 29 Novembre 2018 da Damynavy

[Felis]

Però dice: "MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input."

 

[Damynavy]

https://www.nytimes.com/interactive/2018/11/16/world/asia/lion-air-crash-cockpit.html

 

 

https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/

Modificato 29 Novembre 2018 da Damynavy

[Felis]

9 ore fa, Damynavy scrive:

https://www.nytimes.com/interactive/2018/11/16/world/asia/lion-air-crash-cockpit.html

 

 

https://theaircurrent.com/aviation-safety/what-is-the-boeing-737-max-maneuvering-characteristics-augmentation-system-mcas-jt610/

Ok. Quindi non sarebbe bastato correggere con la levetta a sinistra del manettino, bisognava comunque disattivare il sistema e "trimmare" a manovella. Chiaro. Grazie.

[ISO-8707]

Cita

Lion Air Interim Report Highlights Confusion And Dysfunction

A preliminary report on the Lion Air Flight 610 (JT610) accident investigation sheds little new light on why the pilots did not keep the hard-to-control aircraft from entering its final, fatal dive. But it confirms that familiar procedures being reemphasized to pilots for managing uncommanded nose-down events caused by the aircraft’s new automatic pitch trim protection system—including flipping two switches—had worked for a different crew on the aircraft’s previous flight. Investigators also underscore that the aircraft was not airworthy for at least its last two flights, which points to possible gaps in the airline’s maintenance practices and safety culture.

 

Determining whether the JT610 crew recognized the specific problems their Boeing 737-8 was experiencing and what procedures they followed during their 11-min. flight Oct. 29 will be difficult without recovering the aircraft’s cockpit voice recorder (CVR). The revelation that the automatic stabilizer trim cutout switches worked on the previous flight suggests one explanation—faulty switches—for the inability to stop the automatic nose-down commands is unlikely.

 

Information in Indonesia’s National Transportation Safety Committee (NTSC) report lends further credence to the theory that the JT610 crew became confused and perhaps overwhelmed as they struggled to keep their aircraft’s nose up. 

 

The crew faced immediate problems during their scheduled flight from the Indonesian capital of Jakarta to Pangkal Pinang, including disagreeing angle-of-attack (AOA) indicator vanes. The left AOA vane’s value was 20 deg. higher than the right’s from the start of the flight, so the left vane told the aircraft’s related systems that the nose was too high. This caused a left-side control column stick-shaker stall warning as the aircraft rotated. The aircraft’s airspeed indicators also disagreed.

 

As soon as the flaps retracted, the aircraft’s automatic trim system—apparently the Maneuvering Characteristics Augmentation System (MCAS) flight-control law added to the MAX family to help it handle like 737NGs, but the report does not reference MCAS specifically—applied nose-down trim for 10 sec. The pilots countered by pulling back on the yoke to counteract the unneeded nose-down movement. At least 25 of these exchanges took place during the rest of the flight. The last automatic nose-down input precipitated a dive from about 5,000 ft. that ended with the aircraft hitting the Java Sea. All 181 passengers and eight crewmembers died.

 

“We won’t really know more until we have the CVR recording, but it seems they either didn’t realize the aircraft was trimming against them, or they didn’t realize they could stop it with the cutout switches,” says one 737 pilot with experience on the MAX family, adding the combination of failures may have confounded the crew.

 

“A stick-shaker is a big deal and attention-getting, confounded by the erroneous airspeed indications,” the pilot explains. “The most insidious problem is the trimming, however, which could go unnoticed with the stick-shaker activating. The extended forward trim makes the aircraft much more difficult to control. If you realize what is going on and take steps to address it, this shouldn’t be that hard to handle, but it could be a very confusing and challenging situation close to the ground.”

 

The NTSC report also reveals Lion Air was immediately concerned about the possibility of uncommanded stabilizer inputs playing a role in the accident. Within hours after JT610 disappeared, the airline’s “Safety and Security Directorate issued [a] safety reminder to all Boeing 737 pilots to review several procedures including memory items of Airspeed Unreliable and Runaway Stabilizer,” the NTSC report says. Using the cutout switches is one of the steps on the Runaway Stabilizer checklist, and following is one of several emergency procedures considered “memory items,” meaning pilots should know them, step-by-step, without having to look them up.

 

The JT610 first officer (FO) told air traffic controllers the crew was battling “flight-control problems,” and asked the controllers to verify altitude and airspeed readings because the aircraft’s instruments were not reliable. While these early clues likely played a role in Lion Air’s unusually specific reminder to pilots so soon after an unexplained accident, issues with several previous flights also hinted at what the JT610 crew may have faced.

Pilots reported a series of technical faults with the three-month-old aircraft, PK-LQP, during four flights over three days before the JT610 accident. Among them: AOA, altitude and airspeed sensor disagreements between the pilot’s and the FO’s instruments. Maintenance was performed each night, and ground tests determined the aircraft was airworthy.

 

During PK-LQP’s prior flight on Oct. 28 from Denpasar to Jakarta, “the stick-shaker activated during the rotation and remained active throughout the flight,” the report says. The pilot noticed an “IAS [indicated airspeed] disagree” warning, and that the aircraft was automatically trimming nose down. This was most likely caused by the MCAS.

 

During the next 8 min., the pilots analyzed the problem. They determined that any effort to manually readjust trim and pull the nose up resulted in automatic nose-down commands. The crew followed three nonnormal checklists (NNC): Airspeed Unreliable, Alt Disagree, and—critically—Runaway Stabilizer.

 

At one point, the pilot moved the stabilizer trim switches to “cut out”—one of the Runaway Stabilizer checklist’s last-resort items—and the trimming stopped. He then flipped them back, “but almost immediately the problem reappeared,” says the report on the prior flight. The pilot moved the switches back to “cut out,” and the crew conducted the rest of the flight with manual-trim inputs.

 

When the problems started, the crew appeared to consider diverting. The pilot declared a “PAN PAN”—or urgent situation but not yet an emergency. A controller asked if the flight needed to return to Denpasar, and the pilot responded, “Stand by.” But once the automatic trimming stopped and the aircraft was controllable, the crew decided to continue the flight, because none of the checklists the pilot referenced “contained the instruction, ‘Plan to land at the nearest suitable airport,’” the report says.

 

Following that flight’s arrival in Jakarta, the pilot filed an electronic report summarizing the issues, listing “Airspeed Unreliable” and altitude (ALT) disagreement. He also wrote that the aircraft’s speed-trim system (STS) was “running in the wrong direction.” The report does not say the pilot told mechanics he went through the Runaway Stabilizer checklist.

 

Maintenance conducted following the flight included flushing the left-side pitot and static air data sensors to address the airspeed and altitude disagreements, the report says. A ground test showed the equipment was serviceable. The report does not reference any work or tests on the AOA sensor.

 

A Nov. 10 message from Boeing shed more light on the MCAS, which many pilots did not know existed. It provides automatic nose-down input in certain manual flight profiles to help prevent stalls. The MCAS’ primary input is data from one of two AOA sensors. The system runs through the flight control computer (FCC) and alternates between using data from the aircraft’s left and right AOA sensors with each flight, but a full power-down/power-up of the aircraft will reset the system to take data from the left-side AOA. It does not operate when flaps are deployed.

 

While the MCAS is new, its role as an aid to help trim the aircraft as well as its failure mode—uncommanded nose-down trim caused by incorrect data or an FCC anomaly—are well understood by pilots. Two other stall-protection systems on the MAX, STS and elevator feel shift, are identical to those on the NG.

 

Because of this, Boeing’s focus since the accident has been reiterating that the procedures for stopping uncommanded trim remain unchanged from those for the NG. Many airlines have been updating their pilots with MCAS-related bulletins, while some have gone further. Germany’s TUI fly revamped its preflight briefing procedures to incorporate a review of the MAX family’s Runaway Stabilizer and Airspeed Unreliable checklists “on the first flight of the day and following a change of either pilot.”

 

The NTSC report, which provided facts but no analysis or conclusions, includes several recommendations. One focuses on safety culture—specifically calling on Lion Air to ensure pilots follow the airline’s operations-manual requirement to discontinue a flight if unairworthy conditions occur. The stick-shaker condition during the Oct. 28 flight “is considered [an] unairworthy condition and the flight [should not have] continued,” the report says.

 

Another recommendation calls for better flight documentation, since there was one more flight attendant on board than listed on the weight-and-balance sheet. It also acknowledges actions taken by Boeing, Lion Air and regulators based on what has been learned.

 

Boeing responded to the report’s release with a statement saying it is “taking every measure to fully understand all aspects of this accident, working closely with” investigators and regulators.

 

The manufacturer called attention to ineffective troubleshooting in the days before the accident, noting maintenance logs “recorded problems related to airspeed and altitude on each of the four flights that occurred over the three days prior to Flight 610.” The logs “indicate that various maintenance procedures were performed, but issues related to airspeed and altitude continued on each successive flight,” Boeing points out.

 

The airframer also highlighted the pilots’ actions during the Oct. 28 flight, noting they seemingly faced the same problems as the JT610 crew, and “turned off the stabilizer trim switches within minutes of experiencing the automatic nose-down trim.” The Oct. 28 crew followed checklists as “the appropriate procedure to address unintended horizontal stabilizer movement, regardless of source,” Boeing adds. The Runaway Stabilizer checklist does not discuss why the condition may happen. It only provides increasingly aggressive troubleshooting steps to stop it.

 

The JT610 crew “experienced issues with altitude and airspeed data that the pilots had previously experienced on the earlier flights, due to erroneous AOA data,” Boeing continues. However, “unlike as is stated with respect to the prior flight, the report does not state whether the pilots performed the Runaway Stabilizer procedure or cut out the stabilizer trim switches.” 

 

How Pitch Played Out on JT610 and the Aircraft’s Previous Flight

 

Investigators released depictions of key digital flight-data recorder (DFDR) parameters from Lion Air Flight 610’s (JT610) accident on Oct. 29 and the aircraft’s previous flight the day before. On both flights, the aircraft’s two angle-of-attack (AOA) sensors disagreed, and faulty data from the left-side sensor showed the aircraft was approaching a stall. The aircraft’s flight-control computer (FCC) responded by commanding nose-down inputs, depicted by the orange lines on the charts below. On each flight, pilots responded by pulling back on control columns to counteract the nose-down inputs manually, as depicted in light blue on these charts. But the system continued to detect inaccurate data from the AOA sensor, reactivating the FCC’s automatic nose-down commands. 

 

 

During the Oct. 28 flight (see chart above), the pilots executed several checklists, including Runaway Stabilizer. That checklist includes a item that calls for toggling two “cutout” switches that stop the automatic trim. The pilot toggled the switches, and the trim stopped. He then flipped the switches back on, causing one more cycle of automatic nose-down input and manual response. He quickly toggled the switches off, and left them off for the remainder of the flight.

 

 

Investigators have not said what, if any, troubleshooting procedures the JT610 crew followed, in part because the aircraft’s cockpit voice recorder—which would help illustrate what the pilots were experiencing and how they reacted—has not been recovered. The DFDR depicts (see chart above) a near-continuous cycle of automatic nose-down inputs (orange line), followed by manual nose-up responses (light blue) throughout the 11-min. period from just after rotation to impact. On each flight, the automatic inputs appeared to start with the flaps retracted just after liftoff. During the accident flight, the only period of sustained interruption was when the crew extended the flaps.

 

The automatic inputs were apparently commanded by the Maneuvering Characteristics Augmentation System (MCAS) flight-control law added to the 737 MAX family to help it handle like 737NGs, but the report does not reference the MCAS specifically. The MCAS’ triggers include data from either the left or right AOA input, with the source alternating after each flight. Following a power down/power up of the aircraft, the system starts with left-side AOA input.

 

Boeing says that while the MCAS is a new augmentation to the flight control system, its presence does not change troubleshooting procedures for a Runaway Stabilizer scenario. In a statement on the preliminary accident report, Boeing pointed to the Oct. 28 crew’s successful troubleshooting process when faced with uncommanded nose-down inputs.

http://aviationweek.com/commercial-aviation/lion-air-interim-report-highlights-confusion-and-dysfunction