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Malcolm

787 Software Mods

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Malcolm    646

Underscores the importance of human pilots when automation goes wrong.

Jetstar Speed Incident Spurs 787 Software Modifications

Jun 26, 2017John Croft | Aviation Daily

 

WASHINGTON—Boeing has made two changes to the 787’s flight control software, after a Jetstar Airways 787-8 experienced an erratic-airspeed incident in December 2015.

 

The changes are detailed in a recent report by the Australian Transport Safety Bureau (ATSB). 

The incident occurred when the aircraft, en route from Melbourne, Australia, to Singapore, was cruising at 40,000 ft. approximately 4 hr. into the 8-hr. flight. It flew through an area of “high ice-water content” that caused temporary blockage to all three of its pitot tubes. Boeing determined an invalid airspeed existed by comparing the results among the pitot tubes, with an independently calculated airspeed approximation based on angle-of-attack and inertial data.

Although a previous airworthiness directive (AD) required crews to avoid ice-crystal icing to prevent engine issues, the crew told investigators that the aircraft was too close to the precipitation to maneuver around it once the area appeared on the airborne radar.

Due to the ice, the measured airspeed dropped from approximately 250 kt. to less than 50 kt. in less than 5 sec. This generated several error messages in the cockpit, and caused the flight-control mode to revert to secondary mode. The erroneous airspeed stopped after approximately 17 sec., but pilots were forced to continue flying in the secondary mode, which does not allow for use of the autopilot and multiple other features including envelope-protection and gust-suppression. The reversion in this case could only be reset on the ground.

Faced with not flying on autopilot for another 4 hr., the crew decided to dump fuel and land in Darwin, Australia.

As a result of the incident, the ATSB said Boeing made two changes to the flight-control software. One involves increasing the time required for a “No Computed Data” state, which occurred when all three pitot tubes provided faulty information. This causes the transition into secondary mode. The other limits the rate at which “elevator feel” reduces as airspeed drops, a change meant to help pilots avoid large control wheel inputs in response to perceived changes in airspeed.

In the U.S., the FAA issued an AD advising crews not to make “large-magnitude abrupt control inputs as a response to sudden unrealistic drops in displayed airspeed at high actual airspeed,” according to the ATSB.

The ATSB praised the crew’s response to the problem, noting that the pilots “did not make any large changes to the control inputs” and handled the aircraft according to the “airspeed unreliable” checklist by setting a pitch angle and thrust level that would produce a desired airspeed regardless of the pitot readings.

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DEFCON    684

"Faced with not flying on autopilot for another 4 hr., the crew decided to dump fuel and land in Darwin, Australia."

Is there an AFM restriction that led to the unscheduled landing, or was 4 hours stick time really too much for the pilots to handle?

 

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boestar    600

I suspect the latter

 

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mo32a    284

Yeah, that's what I took out of it as well. Four hours of handflying, we couldn't possibly do that.

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Moon The Loon    296

" Although a previous airworthiness directive (AD) required crews to avoid ice-crystal icing to prevent engine issues, the crew told investigators that the aircraft was too close to the precipitation to maneuver around it once the area appeared on the airborne radar "

REALLY? Either not paying attention and flying into an anvil or inexperience in (I'm assuming) interpreting radar imagery during night ops.

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Malcolm    646
2 hours ago, Moon The Loon said:

" Although a previous airworthiness directive (AD) required crews to avoid ice-crystal icing to prevent engine issues, the crew told investigators that the aircraft was too close to the precipitation to maneuver around it once the area appeared on the airborne radar "

REALLY? Either not paying attention and flying into an anvil or inexperience in (I'm assuming) interpreting radar imagery during night ops.

Remember, this was a crew that was not comfortable flying for 4 more hours without the AutoPilot. Are we seeing the results of under training on "hands on"?

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Boney    50

However, ATC may allow flight in RVSM airspace. Depends on location and traffic at the time. Maybe an ATC person can elaborate as to separation challenges in a non radar environment. If not, then a descent to FL280 or below will be required. If unable to complete mission, fuel remaining, then a diversion will be necessary.

Between the two pilots sharing duties, hand flying, although a challenge at higher levels, is doable. Keeping the seat belt sign on and limit movement about the cabin will help in reducing pitch movement. Explaining this to the pax will help them understand the reason.

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Vsplat    286

There's another aspect to the remaining time in flight.   The crew in the moment would not necessarily have known the origin of the warnings and odd behaviour that resulted in their downgrade. 

I don't know whether this was a day or night event.  They may or may not have seen or painted the weather into which they encountered the icing.  If memory serves, that part of the world is a bit like the Caribbean and central America 'dry' cells. 

Given the degree of computerisation, information filtering and sensor reliance, even in a degraded mode, perhaps the crew was concerned that there were unknown aspects to their situation, so elected to wrap things up as soon as possible.  

FWIW

Vs

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Boney    50

Good point Vsplat. If one isn't sure of what's going on, better to land and talk to maintenance.

Cheers.

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Rich Pulman    494

I don't get some of the comments in this thread. If they had carried on and something further happened, we'd all be very critical of their decision to proceed. They decided to stop and fix the jet. Good decision. :tu::tu: Would anyone here enter the NATS with a similar failure? RVSM issues aside, the South China Sea airspace is very congested and this time of year the weather is very challenging. Not something I'd want to tackle at 28,000' with OR without an autopilot. And I have thousands of hours flying jets single-handed without an autopilot.

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DEFCON    684

When you see the shake going on it's not difficult to appreciate the Captain's decision to land. The media 'report' is misleading to say the least. 

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No matter what plan the crew developed, comments will always appear regarding "why did they that; why didn't they do this; etc...etc...etc..."

None of us were there.  The crew made their decision based on what they had presented to them and carried it through.

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