Boeing 737 e 737 MAX

[Dodicicilindri]

8 ore fa, ISO-8707 scrive:

 

Da quello che si legge, il MAX abbassa autonomamente il muso (non so se tramite trim o equilibratore) se i sensori misurano un AOA eccessivo.

 

Questo spiegherebbe il motivo del disastro. Aspettiamo a trarre le conclusion, certo che l'automazione, quando va in crisi, genera disastri. Poi ripeto e' grave che si siano fatti 4 voli con i sensori di velocita' malfunzionanti.

[ISO-8707]

1 ora fa, Dodicicilindri scrive:

Questo spiegherebbe il motivo del disastro. Aspettiamo a trarre le conclusion, certo che l'automazione, quando va in crisi, genera disastri. Poi ripeto e' grave che si siano fatti 4 voli con i sensori di velocita' malfunzionanti.

 

 

In attesa di trovare una soluzione definitiva, Boeing ha aggiornato il manuale di volo con le procedure da attuare nel caso

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This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.

 

 

Cita

Runaway Stabilizer

Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.

In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.

An erroneous AOA input can cause some or all of the following indications and effects:
• Continuous or intermittent stick shaker on the affected side only.
• Minimum speed bar (red and black) on the affected side only.
• Increasing nose down control forces.
• IAS DISAGREE alert.
• ALT DISAGREE alert.
• AOA DISAGREE alert (if the option is installed).
• FEEL DIFF PRESS light.
• Autopilot may disengage.
• Inability to engage autopilot.

Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

https://ad.easa.europa.eu/blob/2018-23-51_Emergency.pdf/EAD_US-2018-23-51_1

 

[Damynavy]

Allievi/Studentelli della Baltic  (mi pare...)

Min 3 

 

Appena suona l'allarme e butta giù il muso, disattivano e passano a trimmare in manuale.

 

Procedura standard.

 

Non giudico mai un incidente. Troppe variabili.

Aspetto sempre la fine dell'inchiesta...

 

Questi, l'avevano mai preso in mano il manuale?

 

Secondo me è  una domanda legittima.

[itr83]

un aoe guasto aveva provocato un incidente ad un Airbus in un volo di prova:

https://en.wikipedia.org/wiki/XL_Airways_Germany_Flight_888T

 

in realtà il sensore era bloccato dal ghiaccio: l'aereo era stato lavato senza coprire il sensore che si era riempito d'acqua...

[Damynavy]

2 ore fa, itr83 scrive:

un aoe guasto aveva provocato un incidente ad un Airbus in un volo di prova:

https://en.wikipedia.org/wiki/XL_Airways_Germany_Flight_888T

 

in realtà il sensore era bloccato dal ghiaccio: l'aereo era stato lavato senza coprire il sensore che si era riempito d'acqua...

https://aviation-safety.net/database/record.php?id=20081127-0

 

C'è anche il rapporto finale

222 pag.

[ISO-8707]

 

A quanto pare in Boeing si erano dimenticati (o hanno deliberatamente omesso) di riportare sui manuali la presenza del sistema antistallo specifico del MAX

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Pilots Unaware Of 737 Max’s Automatic Stall-Prevention System

 

In a move likely linked to the ongoing investigation into the fatal crash in October of a Lion Air Boeing 737 MAX 8, the aircraft manufacturer has issued a bulletin to operators explaining a system unique to the MAX that automatically pushes the nose down to help prevent stalls in certain flight profiles.

 

Boeing on Nov. 10 issued a multi-operator message (MOM) explaining the MAX’s maneuvering characteristics augmentation system (MCAS) “commands nose-down stabilizer” in certain flight profiles using “input data and other airplane systems.” MCAS is operated by the flight control computer and “activated without pilot input and only operates in manual, flaps-up flight,” Boeing explained.

MCAS is not part of previous 737 designs, Boeing’s MOM confirms.

 

The system also was not covered in MAX flight crew operations manual (FCOM) or difference training for 737NG pilots.

 

“This is the first description you, as 737 pilots, have seen,” the Allied Pilots Association (APA) told American Airlines (AA) pilots in a message on its website. “It is not in the AA 737 Flight Manual Part 2, nor is there a description in the Boeing FCOM. It will be soon.”

 

Aviation Week has reviewed the 737 MAX-family flight crew operations manual for another large MAX-family operator. It does not reference MCAS. A multi-page document issued by the airline’s flight operations department that highlights the differences between the MAX and 737 NG does not mention MCAS or any other changes to the auto-trim system.

 

While the Nov. 10 Boeing message does not reference any in-service incidents or accidents, its timing, combined with an earlier MOM and related regulatory mandate, suggests that MCAS could be suspected of contributing to the Oct. 29 loss of Indonesian LCC Lion Air flight JT610.

 

Investigators are looking at several anomalies, including faulty AOA readings, as part of the probe.  JT610, a MAX 8, crashed into the Java Sea about 13 minutes after departure from Jakarta in good weather, killing all 189 onboard. Preliminary analysis of the flight-recorder data suggests the crew struggled to control the aircraft. Investigators also confirmed that the airframe involved, PK-LQP, experienced faulty airspeed and AOA readings on previous flights.

 

A Nov. 6 MOM from Boeing cautioned that “an erroneous AOA” can trigger automatic nose-down pitch-trim. Boeing referenced a documented procedure for runaway pitch trim that includes switching the system off, as a remedy. FAA in a Nov. 7 emergency directive—which other regulators adopted—sheds more light on the issue. “The [directive] was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer,” FAA said. The directive requires operators to update their flight manuals with Boeing’s information.

 

The 737 has two independent AOA sensors. FAA’s explanation suggests that if one sensor tells the aircraft that the AOA is too high, the auto-trim system could be triggered.

 

Neither the Nov. 6 MOM nor FAA’s directive mentions MCAS. Boeing’s Nov. 6 MOM does not reference any new analysis, nor does it specify that a single piece of bad data could trigger the system.

American has “found no instances of AOA anomalies with our 737 MAX 8 aircraft,” the APA message said. “That is positive news, but it is no assurance that the system will not fail. It is mechanical and software-driven. That is why pilots are at the controls.”

 

Boeing declined to comment.

 

http://aviationweek.com/commercial-aviation/pilots-unaware-737-max-s-automatic-stall-prevention-system

Modificato 13 Novembre 2018 da ISO-8707

[Damynavy]

Domanda:

Ma in conclusione, sono arrivati a un stabilizer runaway?

[Damynavy]

 

https://www.nbcnews.com/news/world/lion-air-crash-scenario-wasn-t-covered-boeing-737-max-n935521

 

Il Comandante  Jon Weaks, presidente della Southwest Airlines Pilots Union, ha dichiarato alla NBC News: "C'è una soluzione: semplicemente girando un interruttore spegni il sistema automatico"...

Modificato 14 Novembre 2018 da Damynavy

[Damynavy]

https://www.seattletimes.com/business/boeing-aerospace/dispute-arises-among-u-s-pilots-on-boeing-737-max-system-linked-to-lion-air-crash/

[Damynavy]