Incident: United B772 at Kahului on Dec 18th 2022, pilots filed safety report | Hacker News Reader

Incident: United B772 at Kahului on Dec 18th 2022, pilots filed safety report

avherald.com

75 pointshugh-avherald44 comments

That airplane snitched on that crew when this incident happened via FOQA datalinks. The 777 is equipped with a real time data modem via Inmarsat that sends back to the United operations home base data on each flight. The SFO United chief pilot was probably waiting for them at the gate when they landed. Airlines will use FOQA data to notify them when overspeed actions or other quality problems occur in flight and will ding the pilots. It's very common.

Also, spacial disorientation is a thing, and the body doesn't typically sense falling very well without visual cues. It is entirely possible that the drop coupled with turbulence on the climb out didn't register with passengers (nor the pilots!) as much as you think. If you've ever experienced unusual attitude recovery training as a pilot, you'll know that it's somewhat shocking what your body is telling vs what you see when you pull your head up and look outside. It is a jarring experience when you learn that your body is straight up lying to you.

Yeah, elevators are like that too! Get into an elevator in a skyscraper and drop 500 feet in a short time, your brain has almost no cue.

> the body doesn't typically sense falling very well without visual cues

the post talks about freefall (-1g) and +2.7g. These would be very noticeable.

Noticeable, but not translatable into any sort of spacial awareness. I'm a commercial pilot with an instrument rating, but as a passenger with the only information being a sequence of variable forces, I absolutely can't tell you what our orientation is at the end of that sequence.

~2.6G is a severe hard landing. A 60-degree bank in level flight produces 2G's. One is really jolting because it happens in an instant, the other is certainly noticeable but also a more docile because it happens over time. If the 2.7G force is over a few seconds, my guess is I'd associate it with moderate to severe turbulence and not give it another thought. Do we know the duration of these forces?

Edit: Also from Avherald, Simon writes From my editorial point of view it is clear however, that the occurrence did not happen along the lines of the report that surfaced on Sunday. And I tend to agree with that, the original reporting is confused how serious the event was. Something happened, pilots self-reported, and received training.

Wonder is this also on airbus and whether this is a new requirement after the loss of the Malaysian airplane?

The voluntary safety reporting system is well-designed IMO, with some details here: https://www.asias.faa.gov/apex/f?p=100:43:::NO::P43_REGION_V...

It’s administered by NASA (not the FAA or NTSB) and I trust them to do what the program claims. I’ve submitted a few reports over the years. One received follow up from a program administrator to ensure they understood the details*. None of the incidents were subject to any FAA follow up, so I never had to test the immunity parts.

* This was a case where the Automated Terminal Info recording was advising pilots to remain clear of a local MLB stadium by reference only to the name of the stadium and not any navigational data to help find it.

There were at least two separate incidents that day due to three frontal systems moving into the islands at that time. This led to turbulence thought to impact flights UA1722 and HA35, but there were actually three incidents if you expand and widen the timeframe to December 15.

On December 15, N13G7, a Hawaii Air ambulance, took off from OGG on route to the island of Hawaii when it descended from 8000 ft and spiraled into the Maui Channel where it impacted the water.

https://www.civilbeat.org/2023/01/air-ambulance-crash-expose...

https://www.documentcloud.org/documents/23565244-report_anc2...

A lot of the reporting that I read about this event showed an astonishing lack of critical thinking. As the linked article says, two things would have to have been true:

1: The aircraft entered into free-fall (i.e. falling at ~9.81m/s) at a low altitude and recovered within 1425ft. This would mean the wings were fully stalled and there was no drag or lift forces on the airframe while it was falling.

2: None of the many passengers on board felt the need to share it on social media.

Both of which are highly unlikely. I'd like to see the report of what actually happened, but I'm not sure if that will be forthcoming since it's a voluntary safety report. I'm not sure if they're treated similarly to NTSB investigations where the reports are made public.

CNN is reporting passenger accounts from the flight. I don't think the lack of social media reports is that telling.

https://lite.cnn.com/travel/article/united-777-plunge-takeof...

> I don't think the lack of social media reports is that telling.

Actually, I find it shocking that almost ten seconds of free fall plus many passengers being terrified to the point of screaming would go unmentioned on social media. That's not an experience you forget. :/

> Actually, I find it shocking that almost ten seconds of free fall plus many passengers being terrified to the point of screaming would go unmentioned on social media. That's not an experience you forget. :/

How do you know it hasn't been mentioned on social media? I have like 6 followers I could have posted my harrowing experience and nobody would see it

That’s a reasonable point. However, while things are more likely to go viral if the original poster has many followers, but it isn’t a hard requirement.

Any of those 6 followers could start things off by sending it to people that follow them at which point it can quickly go exponential.

Keep in mind that Maui in December is insanely expensive. The flight would be skewed older and richer, therefore less social media.

Unless there’s some conspiracy theory, I think it’s just a case of not everything everywhere is live-streamed by influencers (yet).

Searching Twitter for tweets with both airport codes SFO and OGG (the Maui airport code) on those dates: nothing

https://twitter.com/search?q=%22ogg%22%20%22sfo%22%20since%3...

For all messages @united with 1722 on those dates: nothing mentioning this incident

https://twitter.com/search?q=%40united%201722%20since%3A2022...

For all messages @united with SFO on those dates: nothing mentioning this incident

https://twitter.com/search?q=%40united%20sfo%20since%3A2022-...

For all messages @united with OGG on those dates: nothing mentioning this incident

https://twitter.com/search?q=%40united%20ogg%20since%3A2022-...

For all messages with the words maui flight on or around those dates: lots of messages about bad weather, turbulence injuries on a Honolulu-bound flight, delays and cancellations, a lot of complaints about sitting on the tarmac for 30-90 minutes waiting for a gate on Alaska Air flights to Maui, and the Hawaii Life Flight helicopter disappearance, but not this incident

https://twitter.com/search?q=maui%20flight%20since%3A2022-12...

Even if they did go on social media. It's like a sand in the ocean, not everything on social media get's amplified. Chances are folks were told to put away their electronic device since it was during the takeoff, so no one has a recording. That means a tweet or facebook post with no image or picture? Might get 1 or 2 thumbs up.

People pay for that kind of experience: https://www.gozerog.com/

The news cycle was pretty heavy with the other incident involving unexpected turbulence that resulted in hurt passengers.

https://www.hawaiinewsnow.com/2022/12/18/multiple-injuries-r...

Those passenger accounts sound like a word-for-word rewriting of the maybe-faulty radar reports.

Not to besmirch the fine folks at CNN, but I don't believe this article at all. Will wait for more from the pilots, who sound like they've been very open, forthcoming, and responsible here.

I'm not sure a stalled 777 at that altitude with that rate of decent would be able to recover in time.

Since they were flying in cloud, wouldn't spatial disorientation resulting in an accidental nose-down attitude be more likely than a stall?

A dive that gradually became steeper could cause that kind of descent without feeling like freefall to the passengers. They'd sure notice have noticed the 2.7g recovery at the end, though.

Generally spatial disorientation would be pretty unlikely this close to departure, since the departure path tends to be “straight forward with a climb gradient of X” - a pretty unusual situation for pilots of that level of experience.

A possible scenario that has been discussed before is the engagement of autopilot (which often happens at this phase of flight post-departure) with an incorrect altitude entered - my guess is something like 310 rather than 31000, particularly because the language used for altitudes above 17k is in flight levels - “cleared Flight Level 310”, autopilot engages, “whoops…” disengage, recover, climb and continue with corrected autopilot setting.

Again, still odd, but very experienced humans make mistakes like this pretty regularly.

> A possible scenario that has been discussed before is the engagement of autopilot (which often happens at this phase of flight post-departure) with an incorrect altitude entered - my guess is something like 310 rather than 31000

This sounds the most plausible to me of what I’ve heard. Would also explain why “further training” was ordered.

Not an expert here, but isn't this far beyond the descent rate that autopilot would employ in normal operations?

Ceilings were 800 feet, so they were in the clouds almost immediately after departure. The weather in the area that day was terrible and extremely turbulent. I think you drastically underestimate how powerful spacial disorientation is. Given the passengers lost all visual cues just after taking off, and there was likely at least moderate turbulence on climb out, the passengers probably just felt like it was a bumpy climb out. The human body doesn't register progressive falling very well without visual cues.

That amount of freefall would absolutely register. Falling is one thing - being weightless for a few seconds is absolutely noticeable.

I am also confused about the "spatial disorientation" argument, I'm not a pilot but I know there's a good reason there's a primary flight display with an abundance of information(including vertical speed, indicated airspeed and pitch) on the 777 which should've given pilots enough indication about what's going on.

> 1: The aircraft entered into free-fall (i.e. falling at ~9.81m/s) at a low altitude and recovered within 1425ft. This would mean the wings were fully stalled and there was no drag or lift forces on the airframe while it was falling.

It's not true that falling at 9.81m/s means no drag or lift forces were on the place, it could also mean the plane was pointing down and it was engine thrust was accelerating it downwards (not just gravity)

They presumably meant accelerating down at g (9.81 m/s/s) rather than steady velocity of 9.81 m/s.

Whether engine or gravity, that would cause an uncomfortable feeling of weightlessness in the cabin and vertical velocity would build quickly.

It's unlikely to enter an actual free-fall by stalling the plane, but it's entirely possible to produce an acceleration of -1 G by diving - the astronaut training airplanes are doing it all the time. The question is just, why would a normal passenger aircraft do it (except maybe in an extreme emergency)?

A speed of 9.81m/s is not free fall. Acceleration of 9.81m/s² is. If you're actually in free fall, you will quickly accelerate past 9.81m/s to whatever your terminal velocity is.

A typical passenger jet flies at a speed of somewhere between 100m/s and 300m/s. Just a small downward angle can add a vertical component to that vector well above 9.81m/s. That's what I think we're seeing here, not a plane dropping out of the sky.

Yeah - I think if it was an autopilot engagement, the velocity may have been gradual enough that it just felt a little weird. Add in clouds - it’s not a crazy amount of altitude to lose in a jet like this, and you prepare for some weird feelings getting on a jet in the first place.

Did the pilots just not look at the altimeter? I’m not a pilot but it seems to me once the autopilot is set you’d naturally look at the altimeter and maybe airspeed indicator to confirm it was working.

Altimeter is a secondary instrument for a climb. The primary instrument for pitch would be the airspeed indicator (for a typical constant speed climb). The fact that they noticed the descent (on the VSI and altimeter) and corrected indicates they were scanning, but doesn't tell much about what was happening that caused them to transition from a climb to descent.

Yeah, agreed here - workload on a departure (depending on the type of departure) can be pretty heavy compared to cruise phase. Arrivals and approaches are more commonly known to have heavy workloads, but there’s a lot to do just after departure, so this doesn’t feel wildly out of bounds for a scan recovery after an autopilot mistake.

> A typical passenger jet flies at a speed of somewhere between 100m/s and 300m/s. Just a small downward angle can add a vertical component to that vector well above 9.81m/s. That's what I think we're seeing here, not a plane dropping out of the sky.

Don't pick on the commenter's unit mistake. The source material says "the aircraft would have dropped 1425 feet in 12 seconds maximum which requires about free fall acceleration" -- this is a 36 m/s descent; it started from a climb, and then ended in returning to 0 m/s at the minimum altitude. It's 2/3rds of a g acceleration downwards, minimum, if the data is valid.

https://www.dailymail.co.uk/news/article-11746913/Passenger-...

Lots of speculation as to why people didn’t talk about the experience.

A few points should be made: - We don’t feel velocity, we feel acceleration/deceleration. While a sudden drop would feel crazy, if the jet rolled out and into the dive it may be subtle enough initially that the free fall was hard to feel. The pull-up out of the dive probably would have been felt, but! If the pilot came on the intercom and talked about weather, or if the attending crew didn’t act odd after the event, people are less likely to assume something weird happened.

Add to this the likelihood of IMC, as well as the likelihood that the crew warned of potential light turbulence - you’ll have a plane full of well-primed people who accepted the experience as “mostly normal.”

Add to that that there wasn’t likely wifi for another 10min or so, people may forget pretty quickly…

The graph looks wild, but people don’t feel that raw data. Perception is everything, and it is not that surprising that accounts of this event aren’t popping up like crazy.

This makes sense, but during takeoff in a plane of 100+ people, none of them happened to be looking out a window and notice that they were falling below the cloud cover and getting a lot closer to the ocean? Or were they still in the clouds?

EDIT: Someone in another comment mentioned that ceilings were 800 feet, so passengers likely would not have noticed they were getting closer to the ocean at all.

This CNN article suggests people definitely did feel it.

> “It felt like you were climbing to the top of a roller coaster. It was at that point,” Williams said. “There were a number of screams on the plane. Everybody knew that something was out of the ordinary, or at least that this was not normal.”

> The experience was harrowing for passengers.

> “When the plane started to nosedive, multiple screams are being let out, at that point,” Williams said. “You’re trying your best to maintain your composure – there’s obviously kids on the flight – nobody really knows what’s going on, but at the same time, you’re concerned. You don’t know if this is an issue, but it was certainly out of the ordinary.”

> “Someone from the cockpit got on the intercom and said, ‘Alright, folks, you probably felt a couple G’s on that one, but everything’s gonna be OK. We’re gonna be alright,’ ” Williams said.

https://www.cnn.com/travel/article/united-777-plunge-takeoff...

The lack of communication with ATC about the incident is odd. Surely an altitude loss of that magnitude should have caught the controller’s attention.

I don’t know the meteorological details but heavy rain was reported; so low-level wind shear during climb-out is a possibility. But why would the crew not make a PIREP once they were stabilized? It’s something other aircrews would like to know. And were that the case, why would the airline need to subject them to additional training, unless their LLWS escape procedures were improper?

> In addition, if indeed 2.7G were encountered, passengers would certainly have reacted and this occurrence would have been all over the media the next day at the very latest.

While it must have been a scary ten seconds, you can't show g-forces very well on video, especially when it lasts a few seconds. If anyone from this flight had shown up on social media recounting the tale, they would be met with a chorus of voices telling them it's just normal turbulence.

It is curious to me as to why there are zero details as to what actually happened or what additional training was assigned.

Because the details are bad?

What is a bit concerning is the speculation that the flight continued to the intended destination in an effort to avoid having the incident captured by cockpit voice recorder (which apparently only have a recording window of 2 hours???!?).

If the problem was understood and corrected, I don't see any operational reason to not continue to the destination. (Same story on the AA runway incursion in NY. They knew what happened; it was corrected; they called company and continued the trip.) The CVR over-write is a side-effect of those correct decisions.

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