The ridiculous myth about letting bike tyres down when flying.

[Globalti]

The post on BA and travelling with a bike prompts me to post this.

Let's get this straight: the fuselage of a passenger aircraft is a sealed aluminium cylinder, pointed at the front and with a big round plate at the back, concave like the bottom of an aerosol can to resist internal pressure. The whole fuselage is pressurised to the equivalent of around 10,000 feet by compressors powered by the engines. This ensures there is sufficient oxygen available for healthy humans in the cabin and animals in the hold to breathe, as long as they remain sedentary.

Would your tyres explode if you rode your bike over a 10,000 ft Alpine pass? No, they would not.

So why listen to the carp about deflating your tyres before a flight? Because passengers and jobsworth arse-covering handling staff don't understand this simple principle, that's why.

The problems begin if the integrity of the fuselage is destroyed and pressure is lost. If this happens at 32,000 feet I expect there will be minor mayhem in passengers' luggage as tubes of toothpaste and bottles of shampoo will empty explosively while the odd packet of crisps might pop and passengers themselves will be a little distressed. However the pilot will descend rapidly to an altitude where there is enough oxygen and while he is descending, oxygen masks will drop to give a few minutes of safety margin.

I don't know how to calculate the pressures but I expect that at 32,000 feet a bicycle tyre in poor condition might bulge off the rim or pop as the threads fail at the weak spot but I'd be willing to bet that most would not.

Got it?

 

[TheDoctor]

It's simple. Standard atmospheric pressure is about 15 psi.
Would your tyres pop off the rim if you put an extra 15 psi in them? No.
Would, therefore, your tyres pop off the rim in a vacuum? Still no.
Is the air thin enough to be a near vacuum at 30-odd thousand feet? No.
Therefore no problem.

 

[ColinJ]

You are absolutely correct, but the trouble with jobsworths is that they don't like smartarses like us!

On the subject of pressure changes in aircraft ...

I had terrible pressure problems with my ears and sinuses on my first few flights, but eventually discovered Earplanes which eliminated the problem for me. So, there I was on one flight to Spain with my Earplanes inserted, idly watching a young couple in the seats across the aisle playing tonsil tennis. I drank the last of the water from my 750 mL SIS bottle and closed the valve.

Eventually, the seat belt signs went on and we began our descent. I was blissfully unaware of the pressure changes involved until both young people started holding their ears and moaning. The young woman was in such pain that she started sobbing uncontrollably. I thought they were being a bit OTT until I glanced down at my water bottle and saw it being crushed almost flat by the ever-increasing air pressure!

I've done some rapid descents off the big hills around Hebden Bridge and had my ears 'pop'. It never happens on the way up because I'm moving slowly and the pressures have time to equalise.

 

[Brains]

The issue is that FFA rules say planes should not be taking pressurised containers, aerosols, skuba tanks, tyres, camping gaz cylinders etc are all pressurised containers.
None are likely to blow at 30,000 ft and even if they did are unlikely to do any damage to the plane.

However having someting go 'bang' in the hold is most likly to cause your plane to be diverted to the nearest airport to see what happened.

I once spent an afternoon on the runway at Hamburg due to an alarm clock going off in the hold, they simply will not fly with any issues or potential issues outstanding, so I don't have a problem in deflating my tyres. Just take a pump for the other end.

 

[Ticktockmy]

[QUOTE 1670351, member: 45"]Who pumps up the plane tyres then when it's on its descent?[/quote]


Aircraft that will fly at higher altitudes, in the main use nitrogen.

Nitrogen won't entrain moisture, so the vast majority of jets require either nitrogen for the tires. While some compressors and storage tanks may exceed the industry standard, for compressors, of 125 psi, and may get to the ranges required for jets, dryers for regular air and the expense of maintenance makes it far less expensive to have nitrogen delivered virtually on demand by the AirGas, coming in cylinders with 4700psi crammed into them and allowing a mechanic to quickly, efficiently and easily service the tires of a jet up to the 225 or better psi that's required as determined by the manufacturer of the aircraft and the tire.

You also have the added safety of nitrogen being, as I mentioned before, an inert gas. Air contains, as well as nitrogen, oxygen, which is not an inert gas. Not only is it corrosive, in the form of a pure gas, it will spontaneously combust in the presence of petrochemicals, which are typically found in airplanes, in the wings, to which the landing gear is attached, and which most aircraft leak.
to sum up:
1. its non corrosive
2. its non flammable
3. it less likely to change its volume due to temp
4. it is less likely to change its volume at altitude.

Thus no one has to inflate the plane tyres when it decending.

 

[Globalti]

If bike tyres really were a danger to aircraft they would have been banned years ago along with hazardous materials. My company now employs three graduates who do nothing more than ensure our products are safety compliant for airfreight and seafreight.

 

[TheDoctor]

Aircraft that will fly at higher altitudes, in the main use nitrogen.

Nitrogen won't entrain moisture, so the vast majority of jets require either nitrogen for the tires. While some compressors and storage tanks may exceed the industry standard, for compressors, of 125 psi, and may get to the ranges required for jets, dryers for regular air and the expense of maintenance makes it far less expensive to have nitrogen delivered virtually on demand by the AirGas, coming in cylinders with 4700psi crammed into them and allowing a mechanic to quickly, efficiently and easily service the tires of a jet up to the 225 or better psi that's required as determined by the manufacturer of the aircraft and the tire.

You also have the added safety of nitrogen being, as I mentioned before, an inert gas. Air contains, as well as nitrogen, oxygen, which is not an inert gas. Not only is it corrosive, in the form of a pure gas, it will spontaneously combust in the presence of petrochemicals, which are typically found in airplanes, in the wings, to which the landing gear is attached, and which most aircraft leak.
to sum up:
1. its non corrosive
2. its non flammable
3. it less likely to change its volume due to temp
4. it is less likely to change its volume at altitude.

Thus no one has to inflate the plane tyres when it decending.

Oxygen will spontaneously combust? Will it hell.
Petrochemicals will burn in air, if ignited, but an aircraft is sort of...surrounded by air anyhow.
Clue's in the name and all that.
Oxygen is a good oxidising agent, but air's pretty good at that too. If your wings are on fire, then the contents of the tyres are probably the least of your worries!!

DISCLAIMER - I am not an aircraft fitter or anything...

 

[dragon72]

The check-in people always ask me, "Have you deflated your tyres?"
I always lie, "Yes"
I never deflate them though. And nobody ever checks them physically.

 

[TheDoctor]

[QUOTE 1670880, member: 45"]No, but neither did you paste in some Google results.[/quote]
From here...

 

[Brains]

If bike tyres really were a danger to aircraft they would have been banned years ago along with hazardous materials. My company now employs three graduates who do nothing more than ensure our products are safety compliant for airfreight and seafreight.

It a pity a few more freighting companies don't do this.
We have just had to deal with a ship impounded in Finland, the reason was improper packing for the cargo which was bound for South Korea.
They had packed 120 Patriot missiles into cardboard boxes ! Loose, they had not even containerised them !

 

[doog]

I had what I consider to be a close call on a Ryan air flight in June. Just before my tour I had purchased some new Schwalbe marathon tyres. I had a blow out on the rear wheel in my garage when putting them on but really didnt think anything of it (although I thought they seemed a bit loose and easy to get on my rims) Inflated to 90psi went to the airport where some security guy asked if I had let them down (it was boxed and I lied)

At the other end I made the bike up at the front of the airport, cycled around the corner and the tube escaped from the rim and blew like a shotgun going off!

With the suggested increase in pressure of 15psi when flying it must have been a close call. I was to have further blow outs on the tour( transpires the tyres are too big for the rims (25mm marathons on open pro's)

 

[Peteaud]

Ah but what about crisps.

On a plane the bag swells up, obviously if they are Walkers then the amount of air in the bag is even greater, but wouldnt a bike tyre do the same.

 

[ColinJ]

It a pity a few more freighting companies don't do this.
We have just had to deal with a ship impounded in Finland, the reason was improper packing for the cargo which was bound for South Korea.
They had packed 120 Patriot missiles into cardboard boxes ! Loose, they had not even containerised them !

 

[TheDoctor]

Ah but what about crisps.

On a plane the bag swells up, obviously if they are Walkers then the amount of air in the bag is even greater, but wouldnt a bike tyre do the same.

Indeed it would.
Crisp bags aren't built to handle 100 psi, though, and bike tyres are.
That's the difference.

 

[slowmotion]

I do that with my regular luggage. I get a random stranger off the street to pack my bag and lie about it when asked.

Top tip. I'll use that one when I next saunter through the Green Channel with a whole load of white powder.