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Comment by alan5 | Hacker News Reader

> 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.

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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.

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.

Time is money.

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

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