Hacker News Reader

Hacker News

Comment by twtw | Hacker News Reader

Parent Full thread

twtw

It's interesting that you reach that conclusion.

I'll fly 737 max.

I won't fly Lion Air or Ethiopian Airlines.

Southwest: fleet size 754, founded 1967, total of seven accidents with 3 deaths.

Ethiopian Airlines: fleet size 107, 64 accidents with 459 deaths since 1965.

View on HN

I don't have data on flight miles or flight segments by type of aircraft, so let's do a quick and dirty estimate.

Let's say there are 40,000 commercial aircraft worldwide and 350 of these are the Boeing 737 Max [0].

If all aircraft are equally likely to crash, then the probability of a given crash being a 737 Max is 350/40000 = 0.00875.

The probability that two crashes are both 737 Max is 0.00875 * 0.00875 = 0.0000766

It's extremely unlikely that an aircraft representing less than 1% of the global fleet would crash twice in a short period of time unless there is a serious defect with that aircraft.

That's well past probable cause at this point. This aircraft should be grounded until they figure this out.

[0] https://en.wikipedia.org/wiki/List_of_Boeing_737_MAX_orders_...

Active fleet today: https://twitter.com/flightradar24/status/1104838043792490497

> The probability that two crashes are both 737 Max is 0.00875 * 0.00875 = 0.0000766

You need to multiply this by every combination of two crashes in the observed time period with starting and endpoints not cherry picked to include 737 max crashes though.

Be my guest. You'll find that the probability of a rare aircraft crashing twice in a short period of time is infinitesimal, unless that aircraft contributed to the catastrophe.

It's hardly infinitesmal, that's my point.

With an average of 175 737's operating since launch, 4K total widebody commercial aircraft and over a dozen widebody crashes in that period, you get over 10%. Some estimates there but you still have the endpoint issue as well.

There have been a total of 5 commercial air disasters in 2018 and 2019 with fatalities that didn't involve hijacking, landing short of the runway or overshooting the runway [0].

And that includes the crash of a cargo flight with no passengers where the crew was killed.

The 737 Max 8 was involved in 2 of those 5 disasters.

There are between 25,000 and 39,000 commercial aircraft in service depending on who you ask [1].

With 350 737 Maxes delivered so far, that's at most 1.4% of the total today, probably less than half that this time last year. Let's call it 1% on average for 2018 and 2019 combined.

There are 10 ways you can have 2 Max crashes out of 5 total crashes. So the probability is 10 * 0.01^2 * 0.99^2 = 0.00098

Even accounting for n choose k and longer endpoints, it's still an infinitesimal probability that we'd see two catastrophes with the same rare aircraft -- unless that aircraft contributed to the catastrophe.

It should be grounded.

[0] https://en.wikipedia.org/wiki/List_of_accidents_and_incident...

[1] https://www.telegraph.co.uk/travel/travel-truths/how-many-pl...

It is possible for both a carrier to be more at-risk for crashes as well as a plane to be more at-risk for crashes.

The FAA issued an emergency operation directive for the 737 Max due to inaccurate sensors which could lead to a crash. I'm not entirely sure why you're ignoring that fact and deflecting to something unrelated.

> deflecting to something unrelated

I don't think it is unrelated that the only accident thus far of a plane with a failure mode that is more difficult for pilots to respond to was on an airline with a notoriously bad safety record.

I fully recognize the fact that airlines and pilots were not informed well enough about MCAS, but I'm also not ignoring the other circumstances of lion air 610

Safety in depth - a single failure should not be a problem. 610 crashed as a result of MCAS, but also a number of other operational failures of Lion Air and the pilots.

Downvoted. Your data is terrible and should be cited. The 737Max has only been flying for 2-3 years. Southwest is irrelevant (I say as I sit on a SWA flight on the tarmac in SAN waiting for a replacement crew member). I made damn sure it wasn’t a Max (which I flew on Aeromexico twice back in September).

I have no idea where your Ethiopian stats come from because I’ve heard nothing but great things about them. Feel free to rebut.

“Or how about Ethiopian Airlines? Here is another impoverished country surrounded by rugged terrain. Yet the record of its national carrier — three fatal events, one of them a hijacking, in over seventy years of operation — is exceptional. Ethiopian is one of the proudest and arguably one of the safest airlines in the world.”

http://www.askthepilot.com/questionanswers/foreign-airline-s...

Unable to delete, as I was able to find stats last night that confirm Parent's Ethiopian Air stats, and I regret the tone.

Regardless, Ethiopian Air is considered a top tier safe carrier.

I think accidents per trip (flight leg) is a more useful metric than accidents per year. If you're interested in mechanical issues then you'd also need to remove terrorism related deaths.

Yes, it's a small sample size, but if you look at the fatal accident rate per flight leg of a 737 MAX 8, I'm sure it's much higher rate than any other modern aircraft.

According to https://www.tripsavvy.com/the-safest-aircraft-54428, the following modern aircraft have fatality-free records:

Boeing 717 (formerly the MD95)

Bombardier CRJ700/900/1000 regional jet family

Airbus A380

Boeing 787

Boeing 747-8

Airbus A350

Airbus A340

This list is meaningless without accounting for the number of aircraft & the number of miles they have flown. For example, the 737 is not only the world's most popular commercial airliner, it's simultaneously the "most dangerous plane" because it has had 145 accidents [1] and one of the safest planes because the 737 NG variant has only had one crash in 16,047,900 flight hours. [2]

[1] https://www.airfleets.net/crash/stat_plane.htm

[2] http://www.travelvivi.com/the-safest-aircrafts-in-the-world/

And indeed, the 787, 747-8, A350 and arguably the A380 are all new planes that have not accumulated the decades of flight history with huge fleets that the 737 has.

True, but the 737 MAX 8's first commercial flight was in 2017, much newer than any of the aircraft on the above list. The point is that such a new aircraft already has a far worse safety record than plenty of aircraft that have been around for years. I think it's irrelevant to compare 737 subtypes, since discussion focuses on the 737 MAX 8 variant specifically.

> And indeed, the 787, 747-8, A350 and arguably the A380 are all new planes that have not accumulated the decades of flight history with huge fleets that the 737 has.

The 787's first commercial flight was in 2011. The 747-8 in 2012. A350: 2015. A380: 2007. All predate the 737 MAX 8 by years, and have better safety records.

Sure, but for comparison, the original 737 was launched in 1967 (!) and even the 737 NG has been flying since 1997.

So while having two MAXes crash after takeoff mere months apart is indeed statistically unlikely, I wouldn't necessarily leap to the conclusion that the two accidents are related just yet.

You have to know that the problematic Anti-Stall feature was just recently added in the MAX rev 8. The older rev 1-7 don't have it. It might have other stall problems due to being backheavy, but the traditional stall warning should have been good enough. There was no accident in rev 1-7, none with the improved Southwest configuration (with two sensors) and already two complete losses with the updated MCAS rev 8. They already did two more updates on this (9 and 10), but still not safe enough for modern safety standards.

The Concorde used to be #1 on this list, while being the least safe commercial jetliner of all time.

Southwest also took steps to add additional AoA sensor information displays to their 737 Max aircraft in the wake of the Lion Air crash. The operator does make a difference.

https://theaircurrent.com/aviation-safety/southwest-airlines...

If Boeing is issuing software updates that disable manual override without telling pilots, Boeing is completely at fault here, and some of the engineers/executives should face criminal charges.

> criminal charges

Boeing informed the FAA of the changes, and the FAA decided that the pilots and airlines did not need to be informed. Criminal charges for Boeing would be extremely surprising.

Would the FAA decision have any bearing on what happens in Ethiopian airspace?

Good point. Boeing should be have told every customer that bought a plane.

Taking your question at face-value: FAA guidelines apply to all airlines that fly into the US - Ethiopian does.

I am confused. When I read the article about the Lion Air crash, I thought one cause of the crash was that the pilots hadn't been properly trained in the manual override procedure that can deal with the problem with malfunctioning sensors.

I don't understand how a software update can override a completely manual override.

The procedure that pilots are taught to override auto trim was unchanged, but I think that previous auto trim systems could also be "out muscled" just by pulling back on the yoke without actually switching on the manual override. It's that second part that people are pointing out (though I will in turn point out that the pilots on the flight prior to 610 faced similar issued and used the manual override to respond to them).

But Southwest did something nobody else did. They added a second AOA sensor. This should mandatory by every security standard and Southwest did good by mandating it, but Boeing still got away with all other companies.

Good luck flying Southwest in Africa.

You write as if you always have a choice which airline to use. Southwest is mainly USA domestic with a few vacation destinations nearby USA.

Reply on news.ycombinator.com