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Do flies (or champagne bottles) explode at some altitude?

I once flew back to Oxford from southern France at fl115, and can confirm that none of the champagne bottles exploded, and the pesky fruit-flies that were onboard at the beginning were still there at the end of the flight. Those that hadn’t been squashed, that is.
The only thing that has given me a nasty surprise (in the dim and distant past, when I was young and stupid) was opening a flask of hot coffee at 8,000ft and having the cockpit windows instantly mist over due to a modest belch of steam. I really should have thought about that…

pmh wrote:

I had a bike with me on a Lufthansa flight. They insisted to deflate the tyres.

Yes, but not for fear they would burst with altitude but because in case of a cargo hold fire the compressed air inside the tyres will add further oxygen to the fire. Same reason for which scuba tanks and suchlikes need to be emptied on commercial flights. And they pose an additional risk when dropped to the floor during loading.

Last Edited by what_next at 06 Jul 13:16
EDDS - Stuttgart

I had a bike with me on a Lufthansa flight. They insisted to deflate the tyres.

pmh
ekbr ekbi, Denmark

Thanks. I’ll stop deflating them!

Spending too long online
EGTF Fairoaks, EGLL Heathrow, United Kingdom

chrisparker wrote:

At what altitude will they burst?

They bust at no altitude. They already have an internal pressure of 100psi at sea level against an ambient pressure of 15psi or 85psi differential pressure. Carrying them into an earth orbit with no residual pressure at all will take that pressure differential from 85 to 100psi. No big deal.

EDDS - Stuttgart

See this post above.

Administrator
Shoreham EGKA, United Kingdom

How about bicycle tyres? My Brompton’s tyres are pumped up to 100 psi at sea level. At what altitude will they burst? What lower pressure would be safe for flight up to FL250?

Spending too long online
EGTF Fairoaks, EGLL Heathrow, United Kingdom

Peter wrote:

AIUI, if you lose a window on a jet at say -56C then the air inside drops to -56C immediately.

Only in the ideal case of “adiabatic expansion” ( https://en.wikipedia.org/wiki/Adiabatic_process ). Which means that no energy in the form of heat must be exchanged with the environment. In real life, the heat stored in the container (which can be the thick glass of your Champagne bottle or the aluminium shell of your aeroplane or even the plastic of the suitcase around your baggage) is larger by several orders of magnitude that that within the little volume of gas which remains after expansion. So heat transfer from the environment – or container of the gas – has a far greater effect than the expansion of the gas itself.

So after your decopression at FL400, the cabin atmosphere will reach your -56 degrees C for a short moment and almost instantly get back to the 20 degrees or so which everythin else inside the cabin was kept at during the flight.

Last Edited by what_next at 06 Jul 10:59
EDDS - Stuttgart

Isn’t the OAT drop caused directly by the pressure drop?

If you take a non-sealed but insulated container at MSL, say +15C, and rapidly take it to FL300, say -56C, then the temperature of any gas inside it will drop to -56C just as rapidly. The only thing which will prevent non-gaseous objects falling to -56C will be their own thermal mass (specific heat capacity) and insulation.

AIUI, if you lose a window on a jet at say -56C then the air inside drops to -56C immediately.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

…due to the gas law whose name I can’t remember.

That’s one (small) factor, but the big one is ambient temperature. This can be a problem because on longer flights below -30 degrees Celsius things start to freeze. Like the sandwiches or fruit baskets for the return flight…
Our rear cargo hold, which is the big one anyway, is not so bad because some smart guy at Cessnas (yes, they do have some of those too) thought about routing the exhaust flow of the cabin through there. Temperatures can still drop slightly below freezing level, but not enough to ruin the food and beverage supplies.

EDDS - Stuttgart
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