[srishiva]

https://www.nytimes.com/2019/03/21/b...gtype=Homepage

Some feature that could have helped was optional extra !

[Jeroen]

Originally Posted by srishiva

Some feature that could have helped was optional extra !

One of the optional extra, as I understand was an AoA reading. It is a hotly debated topic on several pilot forum whether you should or should not have one.

https://apstraining.com/the-angle-of-attack-debate/

Until recently it was rare to find the actual AoA reading. These days it is becoming more and more available on large and small planes.

It is not so much the cost, it is more about what an AoA reading would really add to the available information to the pilot. There is already a lot to absorb.

What seems to be forgotten is that many planes have a so called stick shaker. Pilots need to be aware when their plane is about to stall. That’s where the stick shaker kicks in, and it does so on the basis of (a.o. the AoA readings).

I am not sure what it would have added in the Lion case. The other feature appears to be a simple annunciation if the two AoA are showing different readings from one another. That could probably be helpful.

Jeroen

[longhorn]

If the pilot had to refer the manual, it's a clear indication that he did not know what to do - which probably points to a lack of sufficient training. Clearly he didn't know that hitting those two switches was the action to be performed.

[vharihar]

Originally Posted by longhorn

If the pilot had to refer the manual, it's a clear indication that he did not know what to do

I'm not sure if thats a fair conclusion.

I am no aviation expert, but from my readings and aviation related hollywood movies, I feel its not uncommon for flight crew to look up manual for some situations (and thats one reason why if given a choice, pilots prefer such emergencies to happen at higher altitudes than lower, so that they have time to think thru, refer to manuals, etc).

[libranof1987]

Originally Posted by longhorn

Clearly he didn't know that hitting those two switches was the action to be performed.

You say this now: in hindsight. Referring to the flight manual is the first action they're expected to do when encountered with a non-routine problem.

I do, however, feel that the off-duty pilot who diagnosed the behavior on the earlier flight could have done better in making a larger audience (Lion Air crew/maintenance, perhaps even Boeing) aware of what happened and what corrective action helped them. But that said, I'm just a keyboard expert, I don't know how these things work.

Another story that acting (turning on the APU within a few seconds of the bird strike) first before reading the manual was Sully's masterstroke.

[Jeroen]

Originally Posted by longhorn

If the pilot had to refer the manual, it's a clear indication that he did not know what to do - which probably points to a lack of sufficient training. Clearly he didn't know that hitting those two switches was the action to be performed.

Originally Posted by longhorn

If the pilot had to refer the manual, it's a clear indication that he did not know what to do - which probably points to a lack of sufficient training. Clearly he didn't know that hitting those two switches was the action to be performed.

There are only certain situation where pilots when faced with unusual behaviour will start acting immediately. There are several procedure that are so called memory items or memory list. Pilots need to be able to execute perfectly from memory. But most trouble shooting is done by first looking up the appropriate check list, often called non normal procedure or NNC non normal checklist.

Obviously, every pilot is taught that whatever happens always fly the plane first. But you rarely start throwing switches without figuring out what goes on and which Procedure or check list is the most appropriate one.

Jeroen

[Chetan_Rao]

Aviation experts, please opine on the claims published in this Seattle Times article.

Apparently, the MCAS was originally designed and documented to intervene to a max 0.6 degrees for stabilizer input, it was later updated to 2.5 degrees without properly updating the Safety Analysis documentation Boeing provided the FAA.

While the article clearly points out that it isn't uncommon to make such configuration changes during testing phase and documents are often updated over a period of time by agreement of involved parties, FAA safety engineers are calling out the lack of due diligence in documenting critical changes to a system designed to repeatedly override pilot inputs, and esp. the design decision of relying on a single sensor (with a failover backup) capable of causing a 'catastrophic failure' event (classified as loss of airplane with multiple fatalities), instead of having a multi-channel comparative sensor setup to drive the MCAS system.

[vharihar]

Originally Posted by libranof1987

Another story that acting (turning on the APU within a few seconds of the bird strike) first before reading the manual was Sully's masterstroke.

I've seen Sully a zillion times, one of my favorites! Liked it so much I bought the DVD.

But one thing that I didn't understand: Why is the APU action by Sully considered a masterstroke? What exactly does an APU do?

I always thought APU is "Auxiliary Power Unit", so some kind of power generator I am guessing (similar to EOG rake in trains). Is that such a big deal in helping glide back down to the Hudson bay safely? How exactly did the APU help?

Can the aviation gurus clarify?

[tj123]

Originally Posted by vharihar

I always thought APU is "Auxiliary Power Unit", so some kind of power generator I am guessing (similar to EOG rake in trains). Is that such a big deal in helping glide back down to the Hudson bay safely? How exactly did the APU help?

APU (Auxillary Power Unit) provides power to critical systems like navigation, communication and hydraulic units to control the plane. These crucial systems can help a pilot safely land an aircraft safely in case of dual engine failure. If APU is not switched on-time then pilot will lose hydraulic controls and it will be a challenge to control the flight.

[itwasntme]

Just out! Preliminary report, very very disturbing.

[vharihar]

Originally Posted by tj123

APU (Auxillary Power Unit) provides power to critical systems like navigation, communication and hydraulic units to control the plane. These crucial systems can help a pilot safely land an aircraft safely in case of dual engine failure. If APU is not switched on-time then pilot will lose hydraulic controls and it will be a challenge to control the flight.

Well, then that seems to be a fairly obvious thing to do, as in: By total engine loss, you have no source of power even to power the avionics, hydraulics, ventilation systems for crew and passengers, etc; so I need to switch on *some* power source. Ergo, the APU.

I'd have thought its part of flight-sim training. Why is it considered such a *masterstroke*? (as if thats the biggest thing to have struck Sully)

I mean, even if he didn't realize it immediately, he'd have seen lights conking out and would have realized sooner or later: "Lets turn on the APU", right?

In the movie, why was such a big deal made of the fact that it struck Sully *immediately* upon the crisis to turn on the APU?

What am I missing?

[Chetan_Rao]

Originally Posted by vharihar

...
I mean, even if he didn't realize it immediately, he'd have seen lights conking out and would have realized sooner or later: "Lets turn on the APU", right?

Layman's explanation, make of it what you will.

If you have no engine power, you're reliant solely on the plane's aerodyamic control surfaces to help it glide as far as possible, and having control quickly is key at low elevation (this incident happened at just under 3000 feet). The APU is also used to start engines, in simple terms, so it would probably be one of the first items on a restart checklist.

'Sooner or later' in this context could've meant the difference between maintaining elevation via gliding to buy yourself some time to make a decision, or plummet like a deadweight and crash.

Investigation documentation points out the engine restart checklist for dual-engine failure doesn't work well for low-altitude situations with insufficient elevation and time to react.

The NTSB used flight simulators to test the possibility that the flight could have returned safely to LaGuardia or diverted to Teterboro; only seven of the thirteen simulated returns to La Guardia succeeded, and only one of the two to Teterboro. Furthermore, the NTSB report called these simulations unrealistic: "The immediate turn made by the pilots during the simulations did not reflect or account for real-world considerations." A further simulation, conducted with the pilot delayed by 35 seconds, crashed. In testimony before the NTSB, Sullenberger maintained that there had been no time to bring the plane to any airport, and that attempting to do so would likely have killed those onboard and more on the ground.

[libranof1987]

Originally Posted by vharihar

In the movie, why was such a big deal made of the fact that it struck Sully *immediately* upon the crisis to turn on the APU?

Because it is the 15th item on the checklist. Had Sully gone through the manual first, vital time would have elapsed before the APU was switched on.

The APU was also required in attempting to re-start the engines, in the odd chance they were still serviceable.

Guess we've digressed enough?

[Sutripta]

Don't aircraft have a wind powered turbine for some emergency power in case of total power loss. (Not that it would have been of much use in a low altitude/ low speed scenario)

Regards
Sutripta

[govigov]

Yes, a RAT (Ram Air Turbine) can be deployed.

Here is a theory in which the force of the air pressure can cause a blowback which can exacerbate the problem

Blowback means the elevator is gradually blown back to lower and lower elevation angles by the pressure of the air as the speed increases. The hydraulic actuators can’t overcome the force of the air and gradually back down if the force of the air grows too strong.

If a blowback phenomenon is confirmed for the 737 at the speeds and altitudes flown, this is what happened at the end of the JT610 flight and probably ET302.

https://leehamnews.com/2019/03/22/bj...-crash-part-2/