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january

SFO- Asiana 777 crash

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I'm not a Boeing fan-boy, but in this case they're trying to blame the automation for a pure pilot screw-up.

 

Bottom line: the crew didn't adequately understand the automation (poor training) leading to the accident.

 

The aircraft screams at you when you disconnect the auto-throttle - there is no "accidentally" to it.

 

Best regards,

Robin.

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As I understand the accident the PF (experienced 747 captain into SFO) tried to get rid of the A/T which was disturbing his attempts to get lower and slower.

On short final the speed dropped very fast, which is normal for an idling T7 with full flaps. But this behaviour of the T7 (large diameter fan twin engine) can be a big surprise for a pilot of a 747 or A340 (four engines with smaller fan diameters). The "low airspeed protection" automation normally protects the plane of its own evident latency risk. Unfortunately the pilot seems to have muted the software alarm in an unforeseen way, so that the automation actually failed. I do not know the details, but I think that the "A/T L/R" arm switches were still set to "armed" and not to "off". Under this circumstance (with A/T switch armed) even a B737 "wakes up the sleeping A/T" at specific phases of flight automatically...

This discussion - again - is IMO not talking about "dangerous" A/Cs. What disturbs me is that the "goofy pilots unable to operate perfect flying machines"-theory again is promoted. Sure, the crew of four pilots did not perform extremly well, but automation at least was "number 5" to fail...

BTW: exactly the same "dilemma" applies to AF447.

 

Greetings,

Claus

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A/T on or off, it doesn't matter. 

 

It's a critical phaze of flight, which means you should be monitoring your speed very closely. 

 

When I am on an autoland approach, do you think I would let the speed bleed of and hope the A/T will fix it? Absolutely not! PF has hand on the throttle and if the speed bleeds off its 2x click and move it forward without any delay.

 

Not letting your speed bleed off on final, and the dangers of letting that happen is something you learn starting the 1st day of your flight training. To me its quite simple, if you're not monitoring your speed, you are not taking flying serious, and you don't belong in a cockpit of ANY airplane. 

 

I personally do not blame the crew though. In my opinion things like this, as was the same with the AF accident, are mostly because of bad pilot training. 

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The NTSB is expected to issue a report on this incident this coming week, I do believe.

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Not letting your speed bleed off on final, and the dangers of letting that happen is something you learn starting the 1st day of your flight training. To me its quite simple, if you're not monitoring your speed, you are not taking flying serious, and you don't belong in a cockpit of ANY airplane.

 

Well said!

 

The NTSB is expected to issue a report on this incident this coming week, I do believe.

 

Unfortunately, I'm not sure the report can be trusted. They seem more interested in whether Boeing will be more or less liable, rather than enhancing aviation safety by correctly assing the failures and inadequacies leading up to the accident (primarily one of crew training).

 

Basic facts: you have two command-rated pilots on the flight deck, of whom one is a Training Captain. They both failed at basic airmanship during a critical phase of flight, at a time when the approach was being hand flown. Major question: why didn't they monitor the airspeed and assess whether the engines were adequately spooled up?

 

They also failed to question whether the AT system had malfunctioned (failure to add power approaching the selected speed), and furthermore, they had selected idle thrust at low altitude (a huuuuge no-no due to spool-up time!).

 

Best regards,

Robin.

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Pilots should use (an appropriate level of) automation; they are not supposed to rely on automation.

 

Robin has said it all.

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When I am on an autoland approach, do you think I would let the speed bleed of and hope the A/T will fix it?

 

I agree with your post to 100% so to say.

Just for clarification: the crew did for sure not wait for the "low airspeed protection" to come into play. AFAIK they had set an approach speed in the MCP and they relied "too much" on A/T while they actually disengaged it unintentionally/unknowingly minutes before while slowing down on idle thrust.

In the end "low airspeed protection" didn't safe the day...

 

 

They also failed to question whether the AT system had malfunctioned (failure to add power approaching the selected speed)

 

Also agree 100% to your post. The question is why the crew failed to react accordingly and which role plays cockpit design and A/P+A/T+FD logic in this context. A contributing factor (caused by ATC) could also be a rather "short final" (visual) for a quite large A/C which in the end led to the "established at 500ft with full flaps and idle thrust" configuration.

 

 

The NTSB is expected to issue a report on this incident this coming week, I do believe.

 

 

Really looking forward to the NTSB report, as this case is IMO a guidepost for future investigations concerning automation and crew training.

 

Greetings,

Claus

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Do you think it's simply a case of disabling the engaged authrottle mode and simply forgetting to renable them afterward?

 

I'm doubting the automation had anything to do with this accident - unless the 777s fbw is supposed to trigger TOGA power like in airbus fbw aircraft.

 

I forsee a recomendation for more emphasis on stall recognition in the works post NTSB report.

 

Xavier

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I'm confused on the fan diameter factor? are you talking about spool up time?

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Report finding issued:

 

 

The National Transportation Safety Board determines that the probable cause of this accident was the flight crew’s mismanagement of the airplane’s descent during the visual approach, the pilot flying’s unintended deactivation of automatic airspeed control, the flight crew’s inadequate monitoring of airspeed, and the flight crew’s delayed execution of a go-around after they became aware that the airplane was below acceptable glidepath and airspeed tolerances. Contributing to the accident were; (1) the complexities of the autothrottle and autopilot flight director systems that were inadequately described in Boeing’s documentation and Asiana’s pilot training, which increased the likelihood of mode error; (2) the flight crew’s nonstandard communication and coordination regarding the use of the autothrottle and autopilot flight director systems; (3) the pilot flying’s inadequate training on the planning and executing of visual approaches; (4) the pilot monitoring/instructor pilot’s inadequate supervision of the pilot flying; and (5) flight crew fatigue which likely degraded their performance.

 

You can read the entire report and recommendations here: http://www.ntsb.gov/news/events/2014/asiana214/abstract.html

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Very clear these guys didn't understand how the 777 AFDS (autopilot flight director system) works at all. They put the missed approach altitude into the MCP while in the V/S pitch mode when that feature (continuing a descent with the MCP higher than current altitude) only works with G/S or VNAV PTH (with an approach and runway loaded in the FMC) as the active pitch mode. They then engaged FLCH at 1500 feet with the MCP set to 3000 and somehow expected a descent from it. In actuality they commanded a climb - FLCH is a simple "dumb" mode and it does what is set in the MCP. They seemed to think it would somehow know they were on an approach and still descend or something like that. Just a total loss of awareness of what they were actually commanding the autopilot to do.

 

The PF then physically held the thrust levers back when the AT servos advanced them as it tried to climb - doing this for more than 3 seconds says to the system "I want manual control of the thrust levers" and it goes into HOLD mode, where the servos are disconnected. It's equivalent to moving the yoke and having the AP disconnect - you still have the FD commands but you are telling the system you want to handfly to achieve them rather than the AP being connected. Same logic, just applied to the autothrottle.

 

Boeing's explanation during the discussion for why the AT didn't wake up to protect speed as it decayed makes perfect sense. FLCH is a pitch for speed mode where the AP uses elevator at a fixed thrust setting to control airspeed. If AT wake-up happened in FLCH, they'd have two separate systems acting as the primary controller of airspeed - pitch *and* thrust. This would be against Boeing's AFDS design philosophy where airspeed should have only one logical controller.

Quite simply, the pilots didn't understand their airplane.

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