Unexpected cracking found on critical Boeing 737 Next Generation part | Hacker News Reader

Unexpected cracking found on critical Boeing 737 Next Generation part

komonews.com

221 pointserentz120 comments

For context, the 737 NG is previous iteration of the 737 (before the MAX) and among the most popular aircraft ever built, with over 7000 in service. Grounding this would absolutely cripple the airline industry.

However, the NG also has an excellent safety record, and 35000 cycles is equivalent to 5 flights (takeoff & landing) every day for 10 years. So while this may lead to extra checks on older aircraft, it's highly unlikely to cause a MAX-style global grounding.

What is the actual safety record of the B-52, which i subjectively consider to be the safest machine in history.

How would the B-52 match up against modern commercial airliners? (Does anyone, other than boeing, even track this stat?)

The calc would be something along the lines of;

Date-of-design -> completion, testing, commissioning, hours in flight - accidents, crashes,pilot error, time in service, fuselage age, etc...

I am subjectively of the opinion that the B-52 is the greatest aircraft ever made.

Tell me more of this b-53 safety record

http://www.airsafe.com/events/models/rate_mod.htm indicates 79 fatal 737 incidents with about a quarter billion flights under their belt.

https://www.globalsecurity.org/wmd/systems/b-52-safety.htm indicates 76 B-52s destroyed in accidents across 7.5 million flight hours.

They're not perfectly comparable sets of numbers, but the B-52s look substantially riskier on a per-hour basis.

Thank you for this!

76 machines destroyed, carrying (obstensibly) nukes.. from 7.5mm flight miles == .00001% risk of failure.

Did I do the math correctly?

With ZERO nuke detonations...

And a flight carcass of nearly 70 years old now???

All aviation is pretty damned safe.

> With ZERO nuke detonations...

Chalk this up to the design of the weapons themselves, not the B-52s. It's actually quite difficult to have an accidental nuclear detonation.

> And a flight carcass of nearly 70 years old now???

Today's B-52s are largely Ships of Theseus. Not much in them is going to be original any more.

A handy website [1] notes at least a couple of B-52 nuclear incidents. In 1961, a B-52 carrying nuclear weapons broke up in mid-air over North Carolina; the bombs did not detonate [2]. In 1966, a B-52 crashed due to a mid-air collision with a refueling tanker over Spain. In this case, the non-nuclear explosives in two of the nuclear weapons detonated, scattering radioactive material [3].

So I would not say "zero nuke detonations". And your .00001% failure rate (I didn't check your math) is not meaningful unless compared to the failure rate of other aircraft. The B-52 is impressive, but not flawless.

[1] http://www.atomicarchive.com/Almanac/Brokenarrows_static.sht...

[2] https://en.wikipedia.org/wiki/1961_Goldsboro_B-52_crash

[3] https://en.wikipedia.org/wiki/1966_Palomares_B-52_crash

Most people would not refer to the incident at Palomares as a "nuke detonation," since there was no nuclear detonation. No fissile reaction etc, just conventional explosives that are part of the weapons trigger. To call it a "nuke detonation" is disingenuous.

B52s were used for conventional bombing plenty often during their service lifetime.

And they came damn close to accidentally detonating on American soil on occasion.

https://en.m.wikipedia.org/wiki/1961_Goldsboro_B-52_crash#La...

It is almost impossible to get a nuke to accidentally detonate. Has nothing to do with the B52. Let alone 1 in 76, we’re talking 1 in millions.

I'm not sure what point you're trying to make, but shifting the goalposts from airframe incidents to ordinance safety really doesn't suit this discussion.

The B-52 is an interesting case of a set of exceptionally long-service individual airframes, with current planned utilisation of aircraft built in the 1960s continuing through the 2050s. The original design being from the 1950s.

That said, B-52s likely have a lighter overall duty-cycle, are subject to risks not typical of most (though not all) airliners (hostile enemy fire), and yes, face consequences of incidents beyond the scope of commercial aviation, though my understanding is that live nuclear weapons haven't been carried as a routine practice since the 1968 Thule Air Base incident and the immediate discontinuation of Operation Chrome Dome:

https://military.wikia.org/wiki/1968_Thule_Air_Base_B-52_cra...

That’s not subjective; you just made it up.

For one thing, B-52s seem to have substantial safety externalities for nearby cities.

>That’s not subjective; you just made it up.

That's the definition of subjective. You're thinking objective.

That's not the definition of subjective. When GP says "That’s not subjective; you just made it up." it means that talking about airplane safety (which can obviously be objectively measured with things like crashes per landing/takeoff, crashes per mile, etc.) with the moniker "it's subjectively the safest" doesn't make any sense.

It would be like saying "That plane is subjectively the heaviest" or "Today is subjectively the hottest day on record" - no, it's not subjective, you just made it up.

I completely disagree with this. I subjectively make my statement based on that data I have available to ME*

Objective would be I have failure data in front of me.

Now, I personally have heard of far fewer B-52 accidents in my lifetime, and the plane is almost double mine, and as such, I deem it safe as heck.

Also, guess what - B-52s carry nukes not passengers.

How many nukes have gone off for a B-52 crash vs how many lives have been lost via commercial crashes?

Also, I come from a nuke family, and an air force family. My grandfather was one of the designers of Hanford and my brother was head of the tenth medical wing and flight surgeon to the joint chiefs, and my dad best friend was sec of energy... in charge of nukes...

So, I stand by my words.

> and the plane is almost double mine

I assume you're talking about lifespan? The B-52 may have been in the air for a long time (though only 15 years longer than the 737), but it has also been flying in much smaller quantities; there have only ever been ~750 B-52s built, while there have been over 10K 737s built. And in addition, a commercial airliner is usually in the air for a much higher percentage of its lifespan than any military airplane.

So for example, the 737-600/700/800/900 series has had 9 accidents (6 full-loss equivalents)... over 100 million flights.

http://www.airsafe.com/events/models/rate_mod.htm

Accident rate info for the B-52 is harder to come by, especially since a lot of the "accidents" are complications from battle damage in Vietnam, but I'm seeing 10 peacetime full-loss incidents just among those that have their own Wikipedia pages:

https://en.wikipedia.org/wiki/Category:Accidents_and_inciden...

> That's not the definition of subjective

Merriam Webster's definition(s):

Definition of subjective (Entry 1 of 2)

1: of, relating to, or constituting a subject: such as

- a - obsolete : of, relating to, or characteristic of one that is a subject especially in lack of freedom of action or in submissiveness

- b - : being or relating to a grammatical subject especially : NOMINATIVE

2: of or relating to the essential being of that which has substance, qualities, attributes, or relations

- a: characteristic of or belonging to reality as perceived rather than as independent of mind : PHENOMENAL — compare OBJECTIVE sense 2a

- b: relating to or being experience or knowledge as conditioned by personal mental characteristics or states

- a(1): peculiar to a particular individual : PERSONAL subjective judgments - (2): modified or affected by personal views, experience, or background a subjective account of the incident

- b: arising from conditions within the brain or sense organs and not directly caused by external stimuli subjective sensations

- c: arising out of or identified by means of one's perception of one's own states and processes a subjective symptom of disease — compare OBJECTIVE sense 2c

5: lacking in reality or substance : ILLUSORY

But you don't have to say: "I'm subjectively of the opinion..."

I also do find the original commenter's use of 'subjective' at the very least, odd, and the thrust of their remark is, subjectively, quite strange.

The part was found damaged at 35,000 cycles. That means it took less than or equal to 35,000 cycles. It's not clear whether it cracked earlier, how many such failures would be needed to down the plane, etc.

Assuming a proper maintenance schedule, we can reasonably reduce that time window.

How often are these particular frame components inspected for cracks or wear?

I don’t know for these. C-checks for 737NG are performed every 730 days and include corrosion/wear checks for the most stressed parts, but not all parts (which are checked at D checks): https://en.wikipedia.org/wiki/Aircraft_maintenance_checks

The article indicated the crack was found not during a regular inspection, but during modifications: "Boeing notified the agency of the matter after it discovered the cracks while conducting modifications on a heavily used aircraft."

And they only found the cracks in other aircraft after specifically looking for it after they noticed the crack in the first aircraft, so it doesn't sound like something checked as part of routine maintenance.

There is a 9 year old documentary on two Boing whistleblowers describing cracking probability on the 737ng. It's an hour long: https://www.youtube.com/watch?v=IaWdEtANi-0

Extremely interesting. Especially, around 19-21 minutes, we find the same problem as on 737 Max: Boeing has the delegated authority from the FAA to certify their own processes and parts.

I’m never flying Boeing again. They were hammering crucial parts to fit, provoking crackling; redrilling holes when the hole was 3 inches apart, endangering the whole structural integrity; painting it all green and sending that to production.

The documentary is about the circles of the airframe structure, not about the wing forks of today’s article, so that makes one new type of botched work from Boeing.

> I’m never flying Boeing again

I suspect you were intending this to be obvious hyperbole, but also this will be very difficult if you’re flying at all regularly. While you can have a look at the equipment the airline thinks it’ll be flying at booking time, there’s no guarantees about which plane will actually show up, and the airline isn’t going to refund your ticket because they decided to swap out their A350 for their 787 for operational reasons.

All this plane talk makes me curious, if there are any airlines that tell you ahead of time what planes they are using for a route? I guess they'd now be even less inclined to tell.

I'm usually flying Alaska or United or Southwest, but yes, they do tell you which plane.

The information is almost certainly available on the page where you see the search results and choose your flights. Probably right next to or near the flight numbers. It is on every major US carrier's search results. I don't know about any of the OTAs: Expedia, Kayak, etc.

It’s there but it isn’t guaranteed nor part of the sales contract.

According to the fine print (and carriers' past actions), nothing on an airline ticket is guaranteed as part of the sales contract; not the plane type, flight numbers, arrival/departure times, baggage handling, connections, and, thanks to overbooking, not even the fact that you have a seat on the plane.

If you have airplane preferences, it's best to fly on airlines that only use planes you like, or never use planes you dislike. That means avoiding the largest airlines, as they are most likely to mix and match.

Budget airlines sometimes use one type of plane, eg. Ryanair only flying Boeing 737-800 (so I guess the original poster would want to avoid them!)

Virtually every airline will tell you on their bookings pages. If you’re flying in the front of the plane, there can be major differences in the hard product between different planes of the same carrier. Qatar Airways kept some crummy slanted recliner chairs in business on their A340s for a long time after the A380 had a great fully-flat bed and a bar onboard, and would fly it on the same route. FinnAir have some great seats on their Asian fleet A350s, but you’ll have a nasty shock if you fly Tokyo-Helsinki-New York as they have some truly dated and shabby A330s flying the latter part.

But: it doesn’t form part of the contract, so no complaints if you get shafted with an old plane.

If a part's made of aluminum and undergoes cyclic stress, even staying within its instantaneous modulus of elasticity, it will eventually crack.

Note the aluminum curve in the graph here [0], it never levels off horizontally.

My understanding is this effectively means the modulus of elasticity for aluminum parts is forever diminishing. Aluminum is a metal that's "work hardened", it's basically becoming increasingly brittle the more cyclic stress it experiences.

I'd been told in the past that commercial planes are regularly X-rayed for cracks as part of their maintenance, because of their extensive use of aluminum.

None of this should be a surprise except that it's supposedly "unexpected" in the pickle fork. These vehicles have always been high maintenance machines, in order for them to be safe all the structural aluminum must be regularly inspected for cracks, the cracks should be expected and parts replaced as needed.

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

Edit:

Out of curiosity I did some digging for photos of this part and more information, this thread delivers some insightful links and citations:

https://www.pprune.org/rumours-news/625886-737ngs-have-crack...

AFAIU, ultrasound is far more typically used than x-rays, as the acoustic properties of fractured castings are more distinctive than their xradiographs.

Apparently induction testing is also used (likely on a similar basis to ultrasound: properties deviate sharply from norm/spec).

The modulus of elasticity of aluminum does not change with cycling (or basically with anything else but big temperature differences).

Fatigue is a damage accumulation process, that does not show in the most obvious properties, like modulus or strength.

The aviation regulations changed a long time ago from requiring to avoid cracks to requiring to have structures that can operate with cracks long enough to for them to be detected, as is exactly the case here. Of course nobody design planes to crack, but the regulations reflect the realization that completely avoiding cracks is impossible ...

Unsurprising given the 2010 Al Jazeera revelations of the Boeing-Ducommun conspiracy and cover-up: critical structural elements that were supposed to be CNC machined by Ducommun were crudely made by hand and Boeing managers ordered them installed into 737 NG (-600, -700, -800, -900) anyhow. And then when a blue-ribbon panel of Boeing employees went to find out what happened, their findings were buried and no corrective action was taken. 737 NG's are flying around with substandard critical structural components like spars and the areas around doors, leading to several fuselage breakups on hard landings and runway overruns, which has killed at least several passengers to date. In past similar incidents, aircraft fuselages survived intact. There's a very real possibility that one or more 737 NG's may breakup in heavy turbulence, hard landings and runway overruns at any time, and Boeing knows about it, but has done nothing to remedy it.

https://youtu.be/IaWdEtANi-0

> leading to several fuselage breakups

[citation needed]. It's what AJ is positing, but it's presented like a correlation, I don't think investigators called that out an a cause of the breakups, and it's been 10 years since that was made and this doesn't seem to be a major problem. One thing I read suggested that the fuselage is strongest at the wing, so the break happens away from that section. That, and hard landing is an understatement; One landed short of the runway, another overshot it, and one dropped onto it.

https://commons.wikimedia.org/w/index.php?title=File%3AAnima... (4:55)

I’m not flying anymore. Between the GHG annual personal emissions and the stunning staggering massively deadly failures of rushed Boeing product launches. Finally I will note the whole damn process is dehumanizing and terrible.

The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety.

If Boeing can't escape the perverse incentives that tempt every company, then what company can and why are we relying on this economic model to drive such a high stakes industry?

Relying on profit-motivated companies to consistently provide value at safety critical levels seems short sighted.

That's why we rely on regulation and oversight for safety, and profit motive and competition to provide value.

Sure, it definitely works great.

>The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety.

I don't see why that's "the worst part". Flying is the safest mode of travel, and among airliners the 737NG is one of the safest planes in aviation history. The fact that cracks have been discovered doesn't change that, and the routine inspections which have discovered these cracks and will lead to them being fixed is precisely the reason why these aircraft, and the aviation industry as a whole, are so incredibly safe.

In fact, finding and correcting faults in airplanes happens constantly. Up until the Boeing debacle this was just something that happend while nobody was looking. Now journalists are riding the scare wave generated by the relevations following the 737 max crashes and dragging all these fairly routine happenings out into the open with disproportionate coverage.

The primary reason why air travel is so safe is that each and every failure in production becomes a major news item for days.

So the system broke somehow, and the news will keep hammering it until someone somewhere learns their lesson. We hope.

Yes, they will go after a bunch of false positives too in the process, but the thing with weeding out the true negatives reliably is that you have to be paranoid about the false positives too.

Cutting the margins too fine and skipping the 'paranoid, inefficient' checks is how we got here.

Focusing a really big spotlight on the entire industry is part of the feedback loop.

The media is ignoring 80 to 90 percent of incidents that happen in aviation that lead to investigations. A fair bunch results in technical changes to aircraft, but it is mostly too boring for a layperson.

The Politics of Attention means we've always been reactive. Too much outrage. Too few eyeballs. Resulting in triage. Made worse as investigative journalism has been gutted these last few decades. Made worse as engagement driven business models (ad revenue) begat outrage culture.

>and the routine inspections which have discovered these cracks

Unfortunately this was not a routine check, it seems that routine checks did not found this issue and only after checks were done specifically to look for this issue more cracks were found.

> Flying is the safest mode of travel

By mile or by minute? It might seem pedantic, but it just means you're better off flying from New York to LA than driving. It doesn't mean you're better off than staying put.

They are the standard. Commercial airline safety issues are uncommon enough to be newsworthy.

Boeing's customers care a lot more than most automaker's customers. 1 in 4 cars on US roads have known unresolved safety recalls.

Cracks are not necessarily something critical. As long as they are identified early enough the affected parts are simply added to the relevant checks (C, D, whatever) and after a predefined number of cycles or hours. Also ad-hoc checks might be required.

Aviation is the standard exactly because defects are identified and handled the way they are, they also tend to be remedied quickly. If not all affected aircraft are grounded, like the 737MAX.

These 737NG cracks can by no means be compared to the 737MAX clusterfuck. The former is pretty normal while the latter is a safety and certification issue of enormous dimensions.

> The worst part of these revelations is that the aviation industry is exalted as the standard other industries should look up to when it comes to safety.

If airplanes were like computers ...

It’s still a very safe method of transport, relatively speaking.

But your other points are 100% correct.

I don't think anyone needs to be concerned about the safety of flying, even with all the news flying is still statistically extremely safe.

I will agree though that the TSA has made things pretty dehumanizing.

It's crazy how much the flight experience varies between countries. I recently traveled between Sweden and Germany and the entire experience from online check-in to reaching my destination was painless and very convenient. There was very little queuing and the longest one was on the tax free when I bought water... Didn't even have to show my passport during the flights and I was never checked by security.

There must have been some security checkpoint when you entered the departure area of the airport. But the rest I agree with.

I'm used to the european airports - they are unfortunately like shopping malls, and totally in your face about it. Enter through security right into a big display of perfumes and other overpriced goods, that's the standard thing.

What surprised me when I was over in Newark airport (and in NY JFK too) was actually how underexploited it was commercially. That's great, just surprising.

I flew from finland to germany yesterday and had the same experience. Checked in online, didn't wait in any lines, and never had to show an ID in the process. I am american, and did not even have to enter my passport details into the online checkin.

That’s probably because both countries are in the Schengen area.

Yes but try flying from California to NY without having an uncomfortable TSA experience.

I did exactly that earlier this week, and it took me less than 10 minutes from arriving at the airport to sitting on my flight.

Yeah this is normal. What you cannot bypass is the security check where they look for weapons and such things.

Returning to America always makes me feel like I'm entering a place that's slightly more dystopic and police state than Norway. From the long queues at the border crossing, to the appearance of military worship advertisements, America feels a bit weird these days.

It's weird. I never used to be afraid of flying at all, but the 737 MAX crashes sort of "triggered" the fear for me. I still fly frequently but I find the experience terrifying now.

As a data scientist, I know the odds of something going wrong are extremely low, but unfortunately I'm not able to rationally control my emotions during flight; the fear is involuntary and difficult to suppress. It also doesn't help that I work at a large tech company and see how many bugs are in the codebase (even with some of the best software engineers in the world), and the fact that airplanes are increasingly run by software makes me feel kind of queasy.

Maybe if you watch more terrifying accidents involving other modes of travel? Car travel is statistically much more dangerous.

Seriously I see the 737 Max debacle as an exception that proves the rule.

But the dehumanizing part can be fixed. We may in the future look on the TSA security theatre as an era of incredible FUD.

I sure hope you are right about that.

I feel the TSA will just continue to grow. It is being fed threats and has nothing else to do but grow.

I want security, but damn.

As for direct GHG emissions, the most efficient mode of travel depends on many factors involving the models, occupancy, and route, but generally speaking, planes can become more efficient than trains for distances >= 700 miles.

Source: https://www.ucsusa.org/clean-vehicles/getting-there-greener

Turns out motor coaches (e.g. Greyhound busses) are the most efficient at pretty much any distance.

Their number for travel by rail: 0.37 - 0.43 pound of CO2 emissions per passenger-mile.

Germany's department of environment number for travel by rail: 38 gram/kilometer = 0.13 pound per passenger mile.

(Source (German): https://www.vcd.org/fileadmin/_processed_/8/9/csm_Emissionen...)

Yeah, electrified rail is by far the most energy-efficient way of transportation. How that translates to CO2 emission of course depends on how the electricity is made.

> Engineers design pickle forks to last the lifetime of the plane, more than 90,000 landings and takeoffs, a term known as "flight cycles" in the aviation industry, without developing cracks.

That number made me do a double take. Seems planes never stay on the ground for very long.

Time is money.

Hopefully autonomous vehicles used on demand see many more hours on the road than our personal vehicles.

They literally stay only the turn around time in commercial aviation in busy operations. At least that is the goal. And of course maintenence and repair.

And an airframe is used over decades. Add some serious safety factor and you are up there at 90000.

But since the 737 max grounding, NGs have seen more usage. So bad news for Boeing. And heaven forbid another grounding - there will literally be not enough physical planes to fly in the skies.

> there will literally be not enough physical planes to fly in the skies.

It'd be interesting - flight prices go up and people realise they didn't need to fly as much as they thought they did?

This is one of the questions I want to see answered in stimulation not in real life. There is a lot of discretionary flying, but there are place whose connection to the world is plane.

You will also have route cancelations. And there will be social costs along the economical as well. All in all unpleasant situation.

It will be good to have someone that understands airplanes to comment on how severe the issue is and possible remedies.

The media have incentive to drum up the issues with boeing and be a tad sensationalist.

From what I understood it will require disassembly of quite a big chunk of the airplane. So it will be expensive and worse slow.

>There is a lot of discretionary flying, but there are place whose connection to the world is plane.

Are you talking about far away towns in, say, Alaska? Those may not be the kind of planes for which we're discussion scarcity, but alas.

Me and my colleagues were flown for training from Oregon to one of our offices in California, this week. So was the trainer. There's still a lot of room to optimize the need for air travel.

The Galapagos comes to mind. The entire economy is premised upon commercial jets landing there hourly. Puerto Rico, Bahamas, etc. Even Continental but remote tourism-driven places like Costa Rica.

I think the price response to a shortage of planes would be super-linear, given that those who fly regularly are not representative of the average economic means. Prices would more than double.

Hawaii...

To a degree but Hawaii has shipping ports and a more diverse economy.

One flight a day for 90,000 flights is 246 years. You are right.

Sometimes they fly routes that are only 30min long. With a 30min turnaround, that could mean a flight every hour.

If they kept one plane flying round trips all day, they might fit 16 flights into a day and theoretically burn through the 90,000 cycles in under 16 years.

Are there examples of routes like this you know of where a 737 is used?

There are routes like this, but none with anywhere near the ridiculous schedules (16 flights per day) suggested.

The Madrid-Barcelona "air shuttle" by Iberia has up to 26 flights a day in each direction https://www.iberia.com/es/news-updates/relaunched-the-air-sh... but they use more than one plane. Still, a lot of cycles! In the peak hours there can be a plane leaving each 15 min. You don't need to book a specific one, just a ticket for the shuttle service and then you just turn up at any time.

LAX-LAS, LAX-SJC, LAX-OAK for example.

Not quite 30minute flights but approaching there at ~40min and ~50min.

Southwest airlines for example exclusively flies a fleet of 737-type variants. Cadence for some of these flights can be over 10x daily, in each direction. The total fleet can see 4k+ flights per day.

https://www.distance.to/ says all around one hour. Why don't you build railroads in America? Such short flights should not exist.

One hour flights are fairly typical in most of the world. Yes, also in progressive Europe.

Yes, they exist in Europe, they ban be dirt cheap, executed by companies run by penny pinchers and mostly superfluous. Going by train is in many cases faster because it gets you from city center toncity center without any airport overhead. But it also costs a multiple of a plane ticket, which should not be the case.

Yes but the cases when taking such short flights instead of trains make sense is when you commute form a small city airport to an international hub for a layover to an international flight and that saves you lots of time as you've already been through security once and you're already inside the airport fairly close to your departure gate so you can arrive pretty close time wise to your next flight as opposed to having to commute from the train station to the airport and be there ~2 hours before the flight to clear security and all.

Nobody takes the plane for 30 min to get from city center to city center, we do it because we have to catch another flight from that city's airport and it's quicker by plane.

To note - very small city airports don't have security to pass through. Of course, at those population densities, trains don't make sense anyway.

We have railroads. The three trips listed by the previous poster all include LAX. LA is surrounded by mountains. The train from LA to SF takes ten hours. The flight is one. California has been trying to build a high speed rail to connect LA to the Bay Area for a long time now, but it's projected to cost 30 billion dollars and the timeline is ridiculous. Last I understood, the project has been shelved indefinitely.

HSR construction is definitely still ongoing: https://buildhsr.com

That being said, I don't believe the full SF->LA project is funded, and absent a more cooperative Federal government, it might never be.

Because the U.S. is a) much less densely populated, b) is very spread out, c) leading to very long distances between cities (which makes rail expensive), but d) very homogeneous in culture and language, so e) families and companies spread out a lot, f) which means train travel is not really practical, but also g) many of these short-haul flights are connections to/from long-haul flights and there's no way we'd take a several hour train ride to then go to an airport, to then take a long-haul flight to then do the whole thing again.

With South West I took a 737 (definitely not the MAX, probably the NG) a few times from ISP (Long Island, NY) to BWI (Baltimore / Washington). It's not 30 minutes but close enough at 40-45 minutes. These flights were within the last 2 years.

Atlanta to Nashville on Southwest. That route usually has a flight time of around 35 minutes.

Not positive of aircraft used, but flights may be as short as 2 minutes:

https://www.tripsavvy.com/the-worlds-shortest-scheduled-flig...

Air NZ used to fly 737s between CHC and WLG. Runway to Runway flight time can be as little as 30min if the wind is blowing in the right direction. Feels weird because there is only about 5min of cruising between accent and decent.

However, demand wasn't high enough to justify non-stop round trips, they replaced the 737s with two A320 flights a day, with a bunch of ATR-72 and Dash 8 flights throughout the day.

The classic example is of course Hawaii Air Flight 243. Before the incident, that airframe accumulated 89,680 cycles in 19 years (over 35,496 flight hours) doing short hops between Hawaiian islands.

Here was one that reached almost 90k cycles in 20 years due to a lot of short flights [1]. Total flight hours were 35k, so an average flight was under 25 minutes.

[1] https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243

Not an aerospace engineer, but this seems like a weird way to measure airplane life. A transpacific plane could have 1/10 the cycles but equal airtime, and one would think that the stresses of flight are worth considering. Wonder why it's not measured in hours, like say, tractors, or miles flown. Do we measure any other engined vehicle this way?

A cycle involves pressurizing the cabin relative to the atmosphere approaching flight altitude, and then depressurizing during the descent.

The pressure differential may not seem like much, 6-10 psi in most cases, but the cabins are quite large, so these forces become substantial. Advanced airframes like the composite 787 use that extra strength, in large part, to lower cabin altitude (i.e. keep higher pressure) because it has such a substantial effect on passenger comfort.

Cycles is absolutely the best way to consider airliner lifespan because that is the most significant stress on the airframe.

Thank you!

There are a variety of ways that age of something can be measured with two common examples in everyday life being people and cars commonly measured in years and kms/miles respectively. The metric chosen is one that adds value for understanding the impact.

Aeroplanes and their components do have a lot of different ways of having their ages measured, depending upon what one cares about. Engines are a good example of something where the hours spent running is usually the most salient.

For fusalages, as we're talking about here, pressurisation cycles is actually very important in pressurised airframes. This is because it is the main source of material fatigue which is a major cause of issues - usually in the form of cracks. This was discovered the hard way with the de Havilland Comet[0].

Smaller non-pressurised planes are normally measured in total flight hours, but the effect of repeatedly pressuring and depressuring is so great that it's the biggest factor that will affect the life of the bigger airframes.

[0] https://en.wikipedia.org/wiki/De_Havilland_Comet#Accidents_a...

Very informative, thank you.

Planes are extremely expensive pieces of machinery and you don't make money if you're not flying passengers with them. I'd be more surprised if they weren't in the air as many hours as possible.

For those curious about how this part looks, Boeing Pickle Fork graphic illustration:

https://www.pprune.org/rumours-news/625886-737ngs-have-crack...

A lot of text providing very little information.

See link for pictures of design

http://newsinflight.com/2019/09/28/boeing-workers-found-new-...

>> We're told this is very much an ongoing investigation, and that it's unclear whether or not this is a widespread issue.

TL;DR: a crack in a critical part was found in one plane during a routine inspection. But you wouldn't know that unless you read all the way to the middle of the article. This is a non-story engineered to create outrage and clicks.

> Another source tells us Boeing quickly reported the issue with the single plane to the FAA last week, and now more planes with similar cracking have been found.

How many? Could be as few as 2. Out of thousands.

Really, the only thing we know is that it's not a single plane.... which is the cause for concern.

2/7000 is not a very low incidence rate as far as safety concerns go. Many cars are recalled for far less severe issues with orders of magnitude lower incidence rates.

It is clearly not all planes were disassembled and checked, from what I read it is not a routine check so it will take a while until all planes are checked. So yeah they may have found only 2 more planes with cracks because they only checked 2 more planes that were already disassembled.

>> Another source tells us Boeing quickly reported the issue with the single plane to the FAA last week, and now more planes with similar cracking have been found.

Looks to be more than just one plane.

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