5 ms·

"A lower flight level to decrease the cabin pressure altitude was also requested to assist with the captain’s recovery." Doesn't flying lower make the cabin pr

"A lower flight level to decrease the cabin pressure altitude was also requested to assist with the captain’s recovery." Doesn't flying lower make the cabin pressure increase?

AWildC182 8y ago
Pressure altitude, they describe cabin pressure in terms of apparent altitude, usually 8000ft+/- and by lowering the outside altitude they can increase the internal pressure/decrease apparent altitude.
- sagebird 8y ago
  I see what you are saying and the article's sentence is technically not wrong. But it is a useless phrasing none the less. By decreasing altitude they decrease apparent altitude... so what? How is that different than saying by filling a glass with water I increase apparent fill level... This is a medical situation so what is relevant is how the change effects the body. So I think the most clear thing to say is that... they flew lower to increase the cabin pressure. Maybe it is some thoughtless force of habit that they chose to describe it that way.
  - AWildC182 8y ago
    Yea, the article was a little strange. They were trying to use the technical aviation terminology as much as possible but ended up mixing and matching a bit after apparently realizing explaining all of it would make the article really long.
  - mbrameld 8y ago
    Pressure altitude isn't the same as flight altitude. You can decrease flight altitude dramatically without changing cabin pressure altitude. You can also vary cabin pressure altitude without changing flight altitude. So saying they descended to lower the cabin pressure altitude is not useless. It describes the outcome (lower cabin pressure altitude) and how they achieved it (by descending). There are other ways of changing cabin pressure altitude, and there are reasons to descend other than for the purpose of lowering cabin pressure altitude. Edit: I see the "I don't understand this so it must be bad" reaction in a lot of junior devs. It's interesting to see it show up in other areas!
    - sagebird 7y ago
      There is value in adding a concise, incorrect comment on hacker news if it is presented in a clear and falsifiable way. I am sorry I did not google "pressure altitude" before commenting and did not present my findings so others could learn from it, but I am happy that AWildC182 cleared it up for me. I still think that the sentence in the article could be written in a clearer, and more direct and correct manner -- that is I think it is bad for reasons other than me not understanding the definition. I understand that pressure altitude is a way to express pressure using a theoretical equivalent altitude, and that it is widely used in aviation because it is convenient and tangible way to express pressure! Though, I still think the goal was to increase pressure (measured in Atmospheres) on the person undergoing a medical emergency. There would be almost no point for a space pilot to descend from 70 to 65 miles altitude in contrast to a terrestrial pilot descending from 8 miles to 3 miles. Even though the difference is pressure altitudes is the same (5 miles delta), the difference in Atmospheres is hugely different. (In the space case there is almost no difference because there is almost no pressure!) That indicates that the patient requires an increase is pressure (Atmospheres) So why not write "They descended to increase cabin pressure". It's simpler, more direct, and shorter. It's offensive to couch a personal insult as an "interesting observation" about junior devs' failings showing up in other areas. Your whole comment seems to be made in bad faith and attempts frame me as a fool to be laughed at. This is one of the reasons I sometimes hate participating in hacker news. Even if I'm an idiot I don't think the snark is justified.
      - scarejunba 7y ago
        You got two pieces of advice for the price of one. In your place, I'd be thankful. No one will remember your username on the internet. I haven't even seen it. Unlike real life, any feeling of humiliation can easily be ignored.
      - mbrameld 7y ago
        You initially expressed confusion about the difference between altitude and pressure altitude with your question "Doesn't flying lower make the cabin pressure increase?" When AWildC182 pointed out your mistake you insisted that the sentence was useless because it was confusing to you. The sentence seems useless to you because you don't have the depth of knowledge to understand it, and instead of putting forth the effort to understand you throw up your hands and declare it a bad sentence. That pattern happens all the time in software with junior developers. They come in so sure of their abilities that anything they don't understand must be wrong or bad or useless. Your exchange here was the first time I had seen it happen outside of software development and I thought it was interesting, so I commented on it. If you find it insulting to have that behavior pointed out to you I would suggest avoiding the behavior.
ghshephard 8y ago
I had to read that sentence a dozen times to figure out what they were saying. It's probably the first time I've ever seen the phrase "Cabin Pressure Altitude" - Might make sense in a technical aviation document, but I'm guessing 99% of readers would have had an easier time with "A lower flight level to increase cabin pressure."
- bdamm 8y ago
  The terminology works very well for pilots, because pilots have got it locked into their brain that higher altitude == lower pressure. Pilots also have fairly extensive rules for how and when they can fly at a given "altitude", defined in terms of the atmosphere the pilot is breathing, so it makes sense to think of the cabin's pressure as "altitude". "Pressure" is not something you can really feel beyond the extremes, but altitude is something you really understand every second of every flight. If you're a pilot.
  - jdietrich 8y ago
    Even as a non-pilot, 8,000ft is more intuitively meaningful than 10.88psi or 0.74atm.
    - derefr 7y ago
      As a structural engineer, I feel like it'd be "obvious" to default to megapascals (MPa) here. Maybe it's less relevant for planes, but if you're in, say, a submarine, then there's a direct relevance of the pressure of the air inside the sub, the pressure of the water outside the sub, and the tensile strength of the hull of the sub—and they're all measured in MPa (or sometimes GPa.)
      - bdamm 7y ago
        For airliners altitude pressure isn't structural (any more) beyond tracking pressurization cycles. It's much more about the human factors; passenger comfort (and sometimes injuries such as burst ear drums), and the aeromedical factors of oxygen saturation within the pilots' bloodstreams.

"A lower flight level to decrease the cabin pressure altitude was also requested to assist with the captain’s recovery." Doesn't flying lower make the cabin pressure increase?

AWildC182 8y ago

Pressure altitude, they describe cabin pressure in terms of apparent altitude, usually 8000ft+/- and by lowering the outside altitude they can increase the internal pressure/decrease apparent altitude.

sagebird 8y ago
I see what you are saying and the article's sentence is technically not wrong. But it is a useless phrasing none the less. By decreasing altitude they decrease apparent altitude... so what? How is that different than saying by filling a glass with water I increase apparent fill level... This is a medical situation so what is relevant is how the change effects the body. So I think the most clear thing to say is that... they flew lower to increase the cabin pressure. Maybe it is some thoughtless force of habit that they chose to describe it that way.
- AWildC182 8y ago
  Yea, the article was a little strange. They were trying to use the technical aviation terminology as much as possible but ended up mixing and matching a bit after apparently realizing explaining all of it would make the article really long.
- mbrameld 8y ago
  Pressure altitude isn't the same as flight altitude. You can decrease flight altitude dramatically without changing cabin pressure altitude. You can also vary cabin pressure altitude without changing flight altitude. So saying they descended to lower the cabin pressure altitude is not useless. It describes the outcome (lower cabin pressure altitude) and how they achieved it (by descending). There are other ways of changing cabin pressure altitude, and there are reasons to descend other than for the purpose of lowering cabin pressure altitude. Edit: I see the "I don't understand this so it must be bad" reaction in a lot of junior devs. It's interesting to see it show up in other areas!
  - sagebird 7y ago
    There is value in adding a concise, incorrect comment on hacker news if it is presented in a clear and falsifiable way. I am sorry I did not google "pressure altitude" before commenting and did not present my findings so others could learn from it, but I am happy that AWildC182 cleared it up for me. I still think that the sentence in the article could be written in a clearer, and more direct and correct manner -- that is I think it is bad for reasons other than me not understanding the definition. I understand that pressure altitude is a way to express pressure using a theoretical equivalent altitude, and that it is widely used in aviation because it is convenient and tangible way to express pressure! Though, I still think the goal was to increase pressure (measured in Atmospheres) on the person undergoing a medical emergency. There would be almost no point for a space pilot to descend from 70 to 65 miles altitude in contrast to a terrestrial pilot descending from 8 miles to 3 miles. Even though the difference is pressure altitudes is the same (5 miles delta), the difference in Atmospheres is hugely different. (In the space case there is almost no difference because there is almost no pressure!) That indicates that the patient requires an increase is pressure (Atmospheres) So why not write "They descended to increase cabin pressure". It's simpler, more direct, and shorter. It's offensive to couch a personal insult as an "interesting observation" about junior devs' failings showing up in other areas. Your whole comment seems to be made in bad faith and attempts frame me as a fool to be laughed at. This is one of the reasons I sometimes hate participating in hacker news. Even if I'm an idiot I don't think the snark is justified.
    - scarejunba 7y ago
      You got two pieces of advice for the price of one. In your place, I'd be thankful. No one will remember your username on the internet. I haven't even seen it. Unlike real life, any feeling of humiliation can easily be ignored.
    - mbrameld 7y ago
      You initially expressed confusion about the difference between altitude and pressure altitude with your question "Doesn't flying lower make the cabin pressure increase?" When AWildC182 pointed out your mistake you insisted that the sentence was useless because it was confusing to you. The sentence seems useless to you because you don't have the depth of knowledge to understand it, and instead of putting forth the effort to understand you throw up your hands and declare it a bad sentence. That pattern happens all the time in software with junior developers. They come in so sure of their abilities that anything they don't understand must be wrong or bad or useless. Your exchange here was the first time I had seen it happen outside of software development and I thought it was interesting, so I commented on it. If you find it insulting to have that behavior pointed out to you I would suggest avoiding the behavior.

ghshephard 8y ago

I had to read that sentence a dozen times to figure out what they were saying. It's probably the first time I've ever seen the phrase "Cabin Pressure Altitude" - Might make sense in a technical aviation document, but I'm guessing 99% of readers would have had an easier time with "A lower flight level to increase cabin pressure."

bdamm 8y ago
The terminology works very well for pilots, because pilots have got it locked into their brain that higher altitude == lower pressure. Pilots also have fairly extensive rules for how and when they can fly at a given "altitude", defined in terms of the atmosphere the pilot is breathing, so it makes sense to think of the cabin's pressure as "altitude". "Pressure" is not something you can really feel beyond the extremes, but altitude is something you really understand every second of every flight. If you're a pilot.
- jdietrich 8y ago
  Even as a non-pilot, 8,000ft is more intuitively meaningful than 10.88psi or 0.74atm.
  - derefr 7y ago
    As a structural engineer, I feel like it'd be "obvious" to default to megapascals (MPa) here. Maybe it's less relevant for planes, but if you're in, say, a submarine, then there's a direct relevance of the pressure of the air inside the sub, the pressure of the water outside the sub, and the tensile strength of the hull of the sub—and they're all measured in MPa (or sometimes GPa.)
    - bdamm 7y ago
      For airliners altitude pressure isn't structural (any more) beyond tracking pressurization cycles. It's much more about the human factors; passenger comfort (and sometimes injuries such as burst ear drums), and the aeromedical factors of oxygen saturation within the pilots' bloodstreams.