Library Ticket

A cautionary tale. Halfway through a flight to UK recently, I altered the time on my analogue watch, pulling out the winder slightly and moving the hands. Some moments later, the glass dome popped off, and it and a gasket landed on my lap.
Not knowing why it happed, I took it to a jeweller for repair. He said that by pulling out the winder, you allowed the air pressure to equalise with the aircraft. As the air pressure in the aircraft decreased during the flight the pressure beneath the dome was higher and popped off the glass.
So, only alter the time on your analogue watch when the aircraft is on the ground.

Rosemary

Good information.

Great to see you back amongst us too.

Rosemary

bobd22

One of the watches I have is a Rotary anologue watch. I rarely use it these days but exactly what you describe used to happen every time I flew wearing that watch. It's the only watch I have had that this happened with.

BristolUK

I've only ever had this type of watch and I must have done it numerous times on the announcement approaching the destination without incident.

It must pay to buy cheap watches

bobd22

All my other watches are this type and only one I have had this problem with is the Rotary, it wasn't a cheap watch either it was 25th anniversary gift from the wife. Not sure if it only happened when I adjusted it or not but definitely glass popped every time I wore it flying. My other watches are Pulsar (brilliant watches) and an Omega which is over 50 years old.

BristolUK

Ha. I actually meant mine were cheap watches

bobd22

No I got what you meant and you are certainly correct versus the Rotary watch. My old omega is automatic I can leave it for years and give it a shake and away it goes keeping perfect time. I have 2 pulsar watches one kinetic never missed a beat in 15 years the other is solar. When I want to wear it couple of minutes in the sun away it goes keeping perfect time.

astera

Does this apply to all analogue watches?

I recall hearing many announcements from the cockpit back in the day informing passengers of the local time at destination "for those of you would like to set your watches."

Listen Very Carefully

So for all you flying /physics experts-does cabin pressure vary in flight ie from take off through the flight to landing and should analogue watches have a pressure relief mechanism....

Notdunroamin

What's a watch

Finknottle

Cabin pressure should remain reasonably constant, at the chosen, set altitude.

Upon climbing out the pressure inside the sealed watch will still be as at ground level while the cabin pressure will be less.

I don't think a relief mechanism is practical.

Mark604

Or alter your watch before take off or on landing. I don't have an analogue watch but I do alter it to the destination time as soon as I get on the plane.
I suppose if you did alter it whilst up high then pull the winder back out as you descend and leave it until you get down.

Barriej

This should only happen on watches with any water resistance or one where you screw down the crown (adjuster)
It's because these watches will have seals.
Your common or garden watch will allow air movement even when the crown is pushed in...

I had a rotary that would steam up every time I flew, due to a small amount of moisture that was inside it....
So anyone lucky enough to own a high end watch may have experienced this.
The simple solution is to pull the crown out to the first stop (if a date watch) or unlock it before the plane takes off.

missile

Only issue I had was when the crown fell off the face of my fake Rolex.

Pulaski

Airliners generally use atmospheric pressure until they reach (during ascent phase) about 10,000ft (3,000m), then the plane maintains the pressure at around that of 10,000ft at higher altitudes.

If there is some emergency that causes the plane to depressurize while at cruising altitude (usually around 33,000-35,000ft these days), such as a window breaking, then the plane will descend to 10,000ft, as the oxygen masks are no longer required at that altitude.

Re watches, I suspect that a very specific set of circumstances needs to occur for the air pressue to pop the face off - the case needs to be airtight, but whatever is holding the face on needs to be weak enough to allow it to pop off. I would assume that non-diving-rate watches are not airtight and therefore that airpressure inside and outside the watch casing will equalize almost instantly on an ongoing basis. Whereas I think that most watches rated for water submersion/ shallow diving (down to 10m/30ft/2 Atmospheres) have a face that is secured tightly enough to not pop off due to an air pressure diffence of a few PSI.

Atmospheric pressure is around 10.2psi at 10,000ft, and at 40,000 ft it's about 2.7psi, so the difference between the inside of the watch and the cabin would only be 7.5psi at the most, and that would only if the plane depressurized at 40,000ft.

Alternatively, if the watch was sealed at sea level, at around 14.7psi, and then the watch was taken on a plane which climbed to 10,000ft, where the airpressure is 10.2psi, the difference in pressure inside and outside would only be 4.5psi, which I am doubtful would be sufficient to pop the face of a diving watch ..... but then opening the case by pulling out the winder, would equalize the pressure, not cause a pressure diffence that would pop the face off. So I don't know why the face popped off, but I am sceptical that a pressure difference released by pulling out the winding knob, was the cause of it.