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Unexpected cracking found on critical Boeing 737 Next Generation part

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Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#81

Post by axaxs »

Obi_Juan_Kenobi wrote: post #73
axaxs wrote: post #69

Earlier quoted context omitted.

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) beca…

Thank you!

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#82

Post by axaxs »

agurk wrote: post #75
axaxs wrote: post #69

Earlier quoted context omitted.

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?

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 so…

Very informative, thank you.

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#83

Post by lutorm »

elif wrote: post #51
sverhagen wrote: post #33

Earlier quoted context omitted.

>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…

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...

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#84

Post by phire »

acjohnson55 wrote: post #13
phire wrote: post #7

Earlier quoted context omitted.

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?

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.

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#85

Post by lutorm »

morsch wrote: post #76
Transfinity wrote: post #68

Earlier quoted context omitted.

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.

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#86

Post by kelnos »

samstave wrote: post #47
burnte wrote: post #41

Earlier quoted context omitted.

>That’s not subjective; you just made it up. That's the definition of subjective. You're thinking objective.

Thank you. This is going to come across a subjectively offensive to people on HN, aside from the old timers, as I am such, stop trying to prove how smart you are. Listen more. Engage rather than flex your ego. Discuss rather than downvote. I almost never vote on anything, @dang may likely be able to look at my click record. I don’t click on votes too often, I engage in discussion as often as possible. (Constantly hit…

Ok, I'll bite: your original comment wasn't useful at all, and didn't push the conversation forward. Making a baseless suggestion that the B-52 is the "safest machine in history" is not useful. You presented no evidence for this claim, and used "subjective" as a weasel word to avoid responsibility for what you were saying.

And then, incredibly, you make a -- reasonable -- assertion as to how you would determine a plane's safety and reliability, but then don't actually bother to try to apply that to the B-52. And then someone downthread uses something similar to your methodology (while presenting hard numbers and sources) to prove you wrong that the B-52 is the safest plane ever.

So my subjective opinion is that you've provided nothing of value to this conversation, and that is why you've been downvoted.

Oh, and calling people "cowards" when you don't like what they're saying or doing? If you want to invoke "old timers" on HN, you might as well at least pay attention to the site guidelines. As someone who has had an account here for 10 years (funny coincidence that you and I created our accounts within a week of each other), you should be well aware of them.

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#87

Post by flexer2 »

alan5 wrote: post #2

> 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.

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.

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#88

Post by BurningFrog »

hn_throwaway_99 wrote: post #57
burnte wrote: post #41

Earlier quoted context omitted.

>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 subjective…

> 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

3

- 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

4

- 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

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#89

Post by kzrdude »

peteretep wrote: post #77
alexis_fr wrote: post #49

Earlier quoted context omitted.

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 pr…

> 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 t…

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.

Re: Unexpected cracking found on critical Boeing 737 Next Generation part

#90

Post by kzrdude »

arkitaip wrote: post #45
tfha wrote: post #21

Earlier quoted context omitted.

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.

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