4 ms·

It is true that you would max-rate descend to get to breathable altitudes, but FYI that will not be flying at a 45 degree angle lol. If you did try to fly an a

by K0balt 6y ago

It is true that you would max-rate descend to get to breathable altitudes, but FYI that will not be flying at a 45 degree angle lol. If you did try to fly an airliner down at a 45 degree angle, you would either have to do it with a falling-leaf stall after slowing to about 150kts (I doubt this is possible in an airliner?) or you would quickly break the speed of sound and the aircraft would disintegrate as the wings and stabilizers were ripped off. A max rate descent feels steep, but it's not that steep lol.

AWildC182 6y ago
They have spoilers which do allow a fairly steep angle, combined with other techniques can get you down very quickly, though not quite 45 dergees IIRC. Some transport aircraft like the C-17 can deploy thrust reverses in flight to achieve those attitudes. I'm told the people riding in back don't enjoy it though.
- Traubenfuchs 6y ago
  Watching two people fight over specialized facts is fascinating. We readers have no clue what‘s true.
  - AWildC182 6y ago
    Fight might be a strong word... I should at least provide a little source material though: https://www.youtube.com/watch?v=lUUU-C-7o98 https://www.youtube.com/watch?v=lUUU-C-7o98 https://www.youtube.com/watch?v=Gdn0465zE4o https://www.youtube.com/watch?v=Gdn0465zE4o
  - jcrawfordor 6y ago
    I think the biggest issue is that the relationship between pitch attitude (angle) and rate of ascent/descent in aircraft is tenuous at best. During landing, for example, it is typical to have a healthy descent rate with the nose slightly up from level. I don't think I've ever seen any procedure with a fixed pitch angle, it pretty much always depends on the gross weight anyway. Emergency descent maneuvers in the C-172 and I believe many other small aircraft actually involve a 45 degree roll angle, and whatever pitch angle achieves a desired speed (e.g. 120 kias in the C-172). This produces a tight downward spiral, the spiral helps because it moves lift off the vertical axis which lets you descend more quickly at a fixed speed - otherwise you'll speed up until the wings fall off. I suspect the 45 degrees above may have come from confusion over which axis it was around. I'm not sure what the exact justification is for the choice of 45 degrees but 60 degrees roll angle is usually considered sort of the upper limit (beyond that is technically aerobatics) so 45 is pretty commonly considered the "steep" extreme. It looks like the procedure is different for the big boys. A quick google shows that the emergency descent procedure for the 747 is thrust closed, speedbrakes at flight position, gear down, make 320 kias. Pitch angle that produces would depend on weight but it's not going to be 45. No spiraling involved, but then 747 seems to (unsurprisingly) have a lower max bank angle (really max load factor) than smaller planes. The point is you wouldn't even really pay attention to the pitch attitude, you'd pay attention to airspeed. The answer to "what should the pitch be" is pretty much always "whatever results in the airspeed you want."
    - iggldiggl 6y ago
      > During landing, for example, it is typical to have a healthy descent rate with the nose slightly up from level. And of course the landing itself (for airliners at least, that is) will be with the main gear first and only then does the nose wheel come down as well. Once you've internalised that, you can't help but notice that one style of pictograms typically used to designate the "Arrivals" section of an airport (e.g. https://www.alamy.com/airport-signs-departure-and-arrivals-at-the-parking-image179396323.html https://www.alamy.com/airport-signs-departure-and-arrivals-a...) alarmingly looks rather like a crash landing than a regular landing :-)

by K0balt 6y ago

AWildC182 6y ago

They have spoilers which do allow a fairly steep angle, combined with other techniques can get you down very quickly, though not quite 45 dergees IIRC. Some transport aircraft like the C-17 can deploy thrust reverses in flight to achieve those attitudes. I'm told the people riding in back don't enjoy it though.

Traubenfuchs 6y ago
Watching two people fight over specialized facts is fascinating. We readers have no clue what‘s true.
- AWildC182 6y ago
  Fight might be a strong word... I should at least provide a little source material though: https://www.youtube.com/watch?v=lUUU-C-7o98 https://www.youtube.com/watch?v=lUUU-C-7o98 https://www.youtube.com/watch?v=Gdn0465zE4o https://www.youtube.com/watch?v=Gdn0465zE4o
- jcrawfordor 6y ago
  I think the biggest issue is that the relationship between pitch attitude (angle) and rate of ascent/descent in aircraft is tenuous at best. During landing, for example, it is typical to have a healthy descent rate with the nose slightly up from level. I don't think I've ever seen any procedure with a fixed pitch angle, it pretty much always depends on the gross weight anyway. Emergency descent maneuvers in the C-172 and I believe many other small aircraft actually involve a 45 degree roll angle, and whatever pitch angle achieves a desired speed (e.g. 120 kias in the C-172). This produces a tight downward spiral, the spiral helps because it moves lift off the vertical axis which lets you descend more quickly at a fixed speed - otherwise you'll speed up until the wings fall off. I suspect the 45 degrees above may have come from confusion over which axis it was around. I'm not sure what the exact justification is for the choice of 45 degrees but 60 degrees roll angle is usually considered sort of the upper limit (beyond that is technically aerobatics) so 45 is pretty commonly considered the "steep" extreme. It looks like the procedure is different for the big boys. A quick google shows that the emergency descent procedure for the 747 is thrust closed, speedbrakes at flight position, gear down, make 320 kias. Pitch angle that produces would depend on weight but it's not going to be 45. No spiraling involved, but then 747 seems to (unsurprisingly) have a lower max bank angle (really max load factor) than smaller planes. The point is you wouldn't even really pay attention to the pitch attitude, you'd pay attention to airspeed. The answer to "what should the pitch be" is pretty much always "whatever results in the airspeed you want."
  - iggldiggl 6y ago
    > During landing, for example, it is typical to have a healthy descent rate with the nose slightly up from level. And of course the landing itself (for airliners at least, that is) will be with the main gear first and only then does the nose wheel come down as well. Once you've internalised that, you can't help but notice that one style of pictograms typically used to designate the "Arrivals" section of an airport (e.g. https://www.alamy.com/airport-signs-departure-and-arrivals-at-the-parking-image179396323.html https://www.alamy.com/airport-signs-departure-and-arrivals-a...) alarmingly looks rather like a crash landing than a regular landing :-)