I haven't thought that air travel can be made significantly better but I think 5 years ago or so I flew the dream liner for the first time and it was so much quieter and so much better because of it.
Anyone knows how long a airplane has to fly to be written of?
Roughly 25 years. The other thing that you probably didn't notice directly but made you feel better is the better pressurization. Newer planes tend to keep higher pressures (since carbon fiber is ridiculously strong), which helps prevent some of the general discomfort of flying.
NB, for any budding bathynauts: carbon fibre is strong under tension, which is precisely the use-case for higher-than-ambient-pressure vessels such as air- and space-craft.
It's far less comparatively strong under compression, which seems to have been the principle failure mode of the now-permanently-submerged Titan.
The failure modes of explosive vs. implosive failure are also relevant. High-pressure implosions tend to collapse the entire hull, whilst so far as I understand, explosive failure, particularly at the relatively low pressure differentials of air and space flight, tend to be localised, and the fibre-reinforced nature of composite materials should reduce damage to the neighbourhood of the initial failure point in many cases. Implosive failure needn't actually penetrate the hull so much as crease it, a mode which CF handles poorly respective to the application.
I think a lot of people have a misconception that keeping pressure in is just as hard as keeping pressure out, while in some ways, it's probably easier to make a space station (keep 1 ATM in) than to make a submarine (keep 500 ATM out.)
Hence sci-fi horrors is like getting sucked out into space through a pinhole.
If a micrometeorite (or other space detritus) puts a pinhole in a wall in the space station, can you plug it by covering it with your finger, without necessarily losing the finger ?
yeah, this is really one of my pet peeves. Lots of people like to pretend that holding a vacuum is really hard, but if all you need is a gross vacuum, it's only about as hard as going down 40 ft into the water.
Carbon fibre, like most composites, is also very hard to predict. It's much more complex to model, especially in terms of how it ages, and there's a lot of opportunity for part-to-patt variability, so even extensive testing doesn't necessarily give you an all-clear. It took a lot fo time and money to get carbon fibre to the same level of understanding as metals for use in airlines.
NGL my mind went straight to the Titan after I read "carbon fiber" and "ridiculously strong" in one sentence. Thank you for the clear explanation and for alleviating my anxiety of flying transcontinental again.
I never got the chance to fly in a Dreamliner, but I have been told that its air is also more humid than standard jets (because of the carbon-fiber construction, I think, so metal oxidation isn’t an issue).
no. It's not rust, but that higher pressure air can hold more water at the same relative humidity. The higher pressure air is achievable because carbon fiber has higher tensile strength per weight.
Really, it's that low on a regular plane? I thought it was more like 6000ft equivalent or so. 10k is high, it's like a third of the altitude they actually fly at.
10k is the altitude above which oxygen masks are required, and any decompression above this altitude triggers the oxygen masks to drop and pilots to make an emergency decent back down to 10k ft.
Given how huge the A380 is, it is more likely to fly less than completely full, which increases the odds that you'll have vacant seat(s) next to you in economy class.
Also, if you want to go for a walk, the distance you are allowed to walk is a lot further.
One thing I dislike about flying a full-ish A380 is the length of time for meal service. It can be over 1 hour that you have to sit with your tray table occupied and seat upright, before your tray gets picked up. If you want to use a laptop or sleep, it feels like forever.
I assume you mean written off, and the answer is it's generally not about how long, it's about how many "cycles". Plane maintenance is usually required on a schedule based on how many flight hours or cycles, and it's usually the cycles they hit first. A cycle is a pressurization and de-pressurization of the cabin. This is what eventually kills a jetliner, the hull will fracture from the stress. The engines are designed to rebuilt/replaced periodically. The hull cannot be reasonably repaired once damaged.
Airliners are required to do different checks at different stages, and the big one costs millions of dollars and requires them to basically disassemble and rebuild the plane. They even may have to remove the paint to check the hull for issues. Industrialized nations generally will only do this a couple times before the cost is more than the jet is worth (I think this is generally around 20,000 cycles, depending on the plane) then they sell them to a third world airline who doesn't have as strict a regulatory scheme. Even then, they generally live on for quite awhile, our regulatory scheme is designed to get as close to zero risk as possible, not to be economical, and it's hard to argue with the results. This is one of many reasons why there are an order of magnitude more crashes in the developing world, though even still safety is high relative to almost anything other than first world commercial airlines.
"The recently imposed smoking ban on many commercial flights has had one distinctly unhealthy side effect -- it snuffed out the most popular method mechanics used to spot cracks in aircraft fuselages.
... mechanics could count on tell-tale build-up of nicotine around cracks as air escaped from the passenger cabin when the plane pressurized after lift-off."
> haven't thought that air travel can be made significantly better
I wonder if it could be made significantly worse. Leg room has been reduced overtime as far as I can tell. I’m 198cm, and it’s actually hell. I probably need to just pay more and go nearer the front, however this would only solve the legroom problem. The seats are too low and aren’t even close to supporting someone tall. I’m in NZ so everything is far away, and 18+ hour flights are actually awful.
I recently flew on an A320neo and then an A320ceo a few days later, both in similar cabin positions and the difference was incredible. On the neo I could easily talk to the cabin crew without raising my voice, the ceo felt like I was having to shout.
I’m flying on an A380 in a few days, that will be interesting experience after only flying long haul on 777s in the past few years
When it comes cases of travel feeling worse, I find it's always worth making sure you adjust the cost for inflation.
Sure, we'd expect certain engineering things to get cheaper over time, but you can also see why some luxury touches got phased--or rather priced--out. :p
I suspect that pressure hull and wing spars experience the greatest loading and fatigue, and may be differentially influenced by overall flight time and takeoff/landing cycles.
Hours. I remember the incident with an Aloha Airlines 737 where fatigue damage caused the failure of part of the structure. Those airplanes were only used for very short hops, hence a high ratio of cycles/hours. While they were within the 62,000 hour limit, the cycles were very high and were not anticipated in the fatigue calculations.
The criteria might have changed since that incident.
Maintenance schedules are based on hours. Pilot experience is also logged as hours.
It's actually both, specifically because of that incident. (Pretty much any time a commercial jetliner crashes, a rule changes, and it's been that way for decades.) There's an hour number and a cycle number for many maintenances, and whichever comes first triggers the maintenance. Hulls, however are rated for a max number of cycles due to fatigue caused by the pressurization/depressurization and that's the part of the plane that cannot be replaced. So the plane usually gets junked or shipped to a developing world airline due to cycles.
NB: Aloha 243 was what I'd had in mind as well, and was when I'd learnt of the distinction between hours and cycles.
For those unfamiliar, a 1988 airline incident in which a Hawaiian airliner experience explosive decompression, though 94 of 95 occupants survived. The lone fatality was a flight attendant who was sucked out through the hole, and if my memory of the post-incident report stands, actually contributed to much of the fuselage damage by enlarging the initial failure region.
Another of my references are the US B-52 Stratofortress fleet, the youngest of which were built 61 years ago in 1963, for which active status is anticipated to extend into the 2050s. My understanding is that wing loadings/unloadings are the limiting factor, with virtually all other parts of the plane being capable of replacement.
The overall airframe is rated for 32,500 to 37,500 hours, with aircraft experiencing about 380 flight hours/year. The wing upper service being the lowest limit of body parts indicated here:
This is my only claim to fame, the pilot is my mom’s cousin. Super nice guy.
Hearing him tell the story first hand was pretty incredible. He saw sky, so knew he had a hole… but had no idea it was so extensive until they landed and he walked back there.
Can you imagine the phone footage we would have had from that it if it happened today?!
You basically subject yourself to altitude sickness every time you fly. It's actually kind of ridiculous how "unpleasant" flights are, but since they're rare enough we just accept it.
Anyone knows how long a airplane has to fly to be written of?