We’ve all heard the horror stories of exploding or leaking fountain pens in flight due to pressure changes from higher pressures on the ground, and therefore in the pen itself, to the cruising altitude where cabin pressure is lower. Knowing that pressure travels from high to low, it’s easy to see why this can and does happen. Well I flew recently (not uncommon for me being a pilot but that’s besides the point) with a fountain pen and used it the entire flight, gate to gate, with no issues whatsoever.
Now for a (hopefully) simple, short, easy-to-understand explanation of why I think I had no issues using my pen the whole flight. The way a pressurization system on a plane works is (I’m going to really simplify it) is that bleed air (excess air) from the engines is pumped into the cabin to pressurize it, very similarly to blowing up a balloon. There is an outflow valve that regulates the pressure of the cabin by letting some of that air escape at a certain rate, similarly to letting some air out a ballon. This outflow valve is important because it allows some air to escape to prevent over pressurizing the cabin of the airplane. You may be thinking, “Why is this important?” or “Why should I care?” It’s important because it’s about regulating pressure, which is why I think I had no issues on my flight.
By using the pen the whole time, the pressure inside the pen never really had a chance to build up because by writing with it, you’re giving that pressure a chance to escape, keeping the pressure differential between the two (plane and pen) relative to what it was on the ground. It’s the same reason why if you open a bottle of water on the ground before taking off and don’t open it again until reaching cruising altitude the bottle has expanded some (higher pressure inside the bottle from being on the ground trapped inside trying to escape to the lower pressure in the cabin at cruising altitude). However, if you open that bottle at regular intervals during the climb, you are allowing the pressure inside to escape, therefore keeping the pressure differential the same relative to what it was on the ground, and at cruising altitude the bottle is the same size and shape it was on the ground. Same is true for the descent, where if the bottle is left untouched after being opened at cruise, the bottle will be crushed in on the ground (higher pressure from being on the ground trying to get to the lower pressure inside the bottle from it being at cruise altitude). If opened at regular intervals during the descent, the bottle will have the same shape on the ground as it did at cruise, again because opening the bottle allows the pressure differential between it and the plane to remain the same. Okay, maybe it wasn’t that short but hopefully it’s simple and easy enough to understand.
Short story, by constantly allowing the pressure inside the pen to stay relative to the cabin pressure, the pen should perform with no issues (in theory) as mine did on that flight.