United Flight 1722 came within 775 feet of plunging into Pacific Ocean | Hacker News Reader

United Flight 1722 came within 775 feet of plunging into Pacific Ocean

theaircurrent.com

77 pointsjaboutboul60 comments

Aviation is so safe and I'd hate to see us ruin that, but that's exactly what the airlines are trying to do. And they're doing so because of a pilot shortage they created when they forced so many pilots into retirement during Covid.

The airlines are trying to move us to a single pilot: https://fortune.com/2022/11/21/airlines-pushing-one-pilot-in...

The airlines are trying to lower flight time requirements for pilots: https://www.travelweekly.com/Travel-News/Airline-News/Region...

They created a problem and now want to solve it by messing with a system that has made air travel the safest way to travel for the last decade. I'm sure more of these near misses would have ended in tragedy with a single, less-experienced pilot.

I cannot believe single-pilot commercial flights are being pushed. Just recently there was an impressive analysis featured on HN about MH370 and how the most likely cause was a pilot on a suicide mission: https://news.ycombinator.com/item?id=34506004

The next depraved pilot going on a suicide mission is suddenly more real.

the flight time requirement is very recent and has not been associated with an improvement in air safety.

however, i would agree that single pilot operations are a pointless optimization (pilots don't cost that much compared to all the other operational costs) and will almost certainly result in more accidents.

If I were the airlines I wouldn't be pushing for a single pilot I'd be pushing for zero pilots.

I'd start it with AI/remote pilot assist. Then I'd push it on cargo flights. Then I'd do people. I'd get the manufacturers to build planes without a cockpit (more space for cargo/passengers!)

I'm honestly confused as to why the industry isn't moving in that direction.

I have wondered if Starlink and similar low-latency worldwide internet networks would lead to remote piloting. Personally, I would expect the first application to be the gradual replacement of maritime pilots.

This article attempts to combine isolated incidents into an overall problem with aviation safety. However, having flown into OGG multiple times, I think this is another example of the typical extreme wind shear/turbulence at this airport and not connected to wider issues. I was in a SW flight that bounced twice and aborted while attempting to land. The airport is located in a difficult location given the high winds that wrap around Haleakala. An older airport a few miles to the south and Maui's first civilian airport, Puunene, was abandoned due to these problems (after racking up an impressive number of killed naval aviators in its wartime role as an USN training field).

OGG has short runways which can make things more difficult, in particular given how much passenger traffic they have. The runway was first built during WWII and is long overdue for total reconstruction.

it's actually kind of incredible how well airplanes manage to take off and land in wind conditions that you realize are remarkably extreme once you've experienced them.

From the graphic, the part that impresses me the most is that it recovered to the original trajectory. That is, it climbed very steeply, instead of merely returning to a normal climb rate. If not for claims to the contrary, I'd have looked at that data and guessed there was a problem with the ADS-B.

"The airline declined to say if the flight data recorder or cockpit voice recorder were analyzed after the flight, though the CVR would've been overwritten by the two-hour recording duration"

How is the recording duration only 2 hours? Is there some non-technical limitation here?

Yes the pilot's union.

Found some details here https://aviation.stackexchange.com/questions/27636/why-are-c...

Maybe there was in 2003 when a quick search says they last amended the regulations, up from 30 minutes that were deemed insufficient? Changing that regulation probably has incredible cost as the certification process for stuff on airplanes is lengthy.

Multiple channel uncompressed audio, with separate tracks for each pilot, ambient sound, ATC, cabin and/or more.

Plus this is done with decades old tech because the blackbox has limited space due to the armored construction and the chips need to be hardened

Adding additional storage doesn't seem like it should be impossible - sure have your backup uncompressed data, but you can have hours and hours of compressed audio in negligible space as well.

The aviation industry is averse to change. Most planes are still being updated with floppy disk.

But I agree. High end commercial solid storage, such Optane, would likely exceeds the requirements needed by the aviation industry.

I understand the aversion to change (no change = wings stay on, change = wings come off?), but I feel adding an additional CVR storage should be low risk - not even necessarily the official armored/blackbox CVR, but say on the quick access recorder - on the basis that the black box CVR is likely more likely required in an instance where the aircraft did end up in a position where the CVR does represent the end of recording.

The existence of extended CVR length would also make the access to poppable breakers for the CVR less important and less error prone.

Pilots understandably don’t like it (invasion of privacy, exposes them to liability, etc) and they have labor power

My guess is that someone changed the indicated airspeed (IAS) instead of the heading (HDG) or altitude (ALT). That explains why nothing was recorded, no one wanted to confess.

The pilots reported it upon arrival via the airline's internal safety reporting process.

but they flew on from Maui instead of turning around. if they’d turned around then the cockpit voice recorders would capture the incident. instead they had 5 hours to get their story straight and no actual recording of the incident.

The autopilot parameters and control inputs would still be captured by the flight data recorder.

Aviation as an industry is built on blameless, honest post-mortems. There's a strong safety culture, and pilots are encouraged to share their mistakes so that other pilots can learn from them.

In most cases, filing a safety report will protect the pilot against any retribution from either the airline or the federal government. At worst, they'd be asked to undergo additional training. There's no reason for the pilots to engage in deception here.

Which does draw attention to the still anemic CVR storage size. I recall incidents where the length of the flight was longer than the CVR storage, or the pilots forgetting/failing to pop the CVR breaker, leading to events being overwritten.

In this day and age it does not seem reasonable to have less than 24 hours of CVR storage - it gives time for any flight, and also space for people forgetting to pop breakers.

One time I was flying into Atlanta during a thunderstorm with reported tornado warnings nearby, and I vividly remember the turbulence being so bad that at times it felt like the plane just dropped several hundred feet in mid-air on approach.

Now I don't know if that was actually the case or not, but I can't imagine that happening and being ~775 feet off the ground/water.

Crazy.

Here is Blancolirio's report on Flight 1722 [1] He covers most flight incidents. His theory is switching to auto-pilot with it dialed into a low altitude and the pilot correcting.

[1] - https://www.youtube.com/watch?v=1B9mQQnZg_8 [video][11 mins]

I like blancolirio's channel but his theory about what happened is probably incorrect even though I think he chose the right analogy.

His information about the previous 777 incident from 2021 is incorrect. The crew in that case did set the correct altitude in the MCP, but the system was stuck in ALT HOLD mode. The crew was hand flying following the flight director, which was telling the crew basically not to climb, so they had a very slow rate of climb. Unlike in this case, they didn't have a descent.

Boeing issued a special airworthiness information directive about this - https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID15068...

What happened in this case is somewhat different. They had a sudden descent. Perhaps in this case it was enabling the autopilot (= automatically following the flight director, stuck in ALT HOLD mode at airport altitude despite setting the MCP) that caused the descent.

Did the tune here change? United originally stated they didn't think the event warranted FAA involvement. Which of course sounds crazy, far more benign events get reported to the FAA.

The pilots voluntarily filed an internal safety report upon arrival - which automatically gets forwarded to the FAA and acted on by the airline's safety department.

The aricle shows a rendering of data of the event from flightradar24. Is there something set up by flightaware or the community that looks for sudden changes in altitude?

Edit: messed up original source

For reference purposes, 775 feet is 236 meters, or three Boeing 777's, two football fields held vertically, 1240 bananas, or two thirds of the Empire State Building.

How many Olympic swimming pools?

4.5

The bananas is what illustrated it for me, thanks.

But how many Libraries of Congress is it?

They claimed to have 650 miles of shelf space as of 2009, so 1/443 of that.

They have 140,000 comic books on file. Assuming they average 1/8" thick, the stack of them would be twice the height of that plane.

How many HN threads responding to someone locked out of their Google account is that?

The blancolirio youtube channel covered this today[0]. His theory is that the autopilot was set incorrectly. When enabled shortly after takeoff it triggered the dive.

[0]: https://www.youtube.com/watch?v=1B9mQQnZg_8

Just looking at the rendering of the flight data -- did nobody post footage on social media from inside the plane during that dive, or the subsequent climb? That looks like a roller coaster of a flight, if I have the scale correct.

The flight was likely in IMC. There wouldn't be much to record.

If so, it's also entirely possible passengers didn't realize what was going on. The human vestibular system is notoriously bad at interpreting motion without outside visual references.

they wouldn't have realized what specifically was going on, but it would have felt very unusual at two different points (initial descent and initial recovery).

Previous discussion of the same December 18th event: https://news.ycombinator.com/item?id=34766467

Sounds like maybe a microburst?

I hope it's something like that and not an unexplained mechanical or software issue. I'd have expected after an incident like that so close to the departure airport, you'd turn around and get everybody on a different flight.

In the event of weather like that you want to get as far away as you can as fast as you can. Don’t want to hit another on approach.

In the event of a temporary/localized weather condition or a flight crew error, understood, corrected, and with no expectation of recurrence, I'd generally expect a continuation to the destination. This occurrence slightly exceeded the transport category load factor limit of 2.5g, but I doubt the flight crew was aware of the slight exceedance at the time of the flight.

What is a microbust?

Its a burst of strong updrafts or downdrafts, it’s very dangerous in aircraft.

Video of some small airplanes attempting to fly in microburst conditions: https://m.youtube.com/watch?v=b_WmjWAGkLI

Powerful downburt. The air can be descending at thousands of feet per minute.

A fairly recent incident that did result in a crash: https://en.m.wikipedia.org/wiki/Aeroméxico_Connect_Flight_24...

A microburst is an intense column of descending air that sometimes occurs within thunderstorms. They are incredibly hazardous, and often produce downdrafts that exceed 6,000 feet per minute - well beyond even an airliner's climb performance.

See:

- https://en.wikipedia.org/wiki/Downburst

- https://www.boldmethod.com/learn-to-fly/weather/microbursts-...

There's an entire list of disasters where an airliner inadvertently flew into a microburst and couldn't escape in time. Pilots are trained to avoid the conditions that create them, and some airports have LLWS warning equipment to help identify when they're occuring (such as the TDWR system, which shares the DFS spectrum used by 5 GHz WiFi).

A lot of air moving down as one large mass. One happened a few km from here two years ago, just over a canal that carries a lot of shipping from Utrecht to Amsterdam. Along the side of that canal there are long rows of pretty sturdy trees. Over about two hundred meters they had all snapped like matchsticks, a few meters above the ground. The theory on why this happened is that the air has to go somewhere when it reaches the bottom, converting a large mass of air moving downwards into a large mass of air moving sideways and that happened to coincide with the treeline base.

Here are some pictures of that event:

https://www.parool.nl/nieuws/bomen-als-luciferhoutjes-omgekn...

The way those trunks are splintered is interesting, normally a tree under wind pressure will topple as a whole, so this must have happened extremely quickly for the tree base not to have moved but the top to be snapped off.

Why speculate when the article itself is quite clear on the cause?

„(…) a formal internal safety report was filed by the pilots and the aircraft was inspected before its next flight. “ United then closely coordinated with the FAA and ALPA on an investigation that ultimately resulted in the pilots receiving additional training.”

That’s not clear at all to me. Can you clarify?

I think you're reading too far into that: that could mean anything from "the pilots needed more training to handle a microburst" to "we don't know what happened, so we're going to blame it on a lack of training."

Training might be on Reporting the live observed incident in real time, for the benefit of others who might be in that same area soon.

Probably not quite real time. Aviate, navigate, communicate. In that order.

In the sense of after they'd recovered or were well in control again rather than waiting until after the entire flight.

Even if the training is due an error that caused the incident, it doesn't say what the error was. I'm sure they didn't confuse their plane for a submarine.

At first read this sounded like maybe a wind shear, but very curious that nothing was picked up by ATC about this, nor did the pilots say anything. Quite odd.

My first thought. Where was the PIREP if it was windshear? Obviously not mandatory but feel like that’s something you’d share earliest.

According to FR24 [0], the decrease in altitude corresponds to an increase in groundspeed. If you're flying through descending air, the groundspeed generally wouldn't change, just the rate of climb decreases. Even if you increase thrust, you'll use this to arrest the sink rate, rather than increase groundspeed. Instead, it looks like they first traded altitude for airspeed, then airspeed for altitude, and ended up close to the original climb track. Sounds more like a straightforward dive to me.

[0] https://www.flightradar24.com/blog/united-airlines-777-dives...

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