Quote:
Originally Posted by Ataman
I was flying once from New York to Germany. Real bad turbulence. Anyhow, at times it felt like the plane was falling, like in a free fall, the same sensation as on certain roller coasters. What is that? Like, do planes actually drop a few feet in crappy weather?
Thanks and good luck in retirement.
The atmosphere is a fluid and a plane flying through it is subject to any disturbances in that fluid, much like a boat on water. And to continue that analogy, the size and speed of the vessel relates to the effect of the turbulence.
I once had a scary boat ride across the Potomac River in a 19’ Sea Ray in 2 foot swells. An aircraft carrier wouldn’t even notice that. I also remember taking one of my younger brothers for his first airplane ride shortly after I got my license. We went up in a Cessna 152 on a hot summer day. That heat creates thermal disturbances in the air, especially below the cumulus clouds. A Cessna 152 (two seat trainer) has a pretty light wing loading and you feel every little bump in it. My brother was not happy and I made a mental note then to never take someone up for their first plane ride on anything but a perfectly smooth day.
So to answer your specific question, yes the plane actually experiences minor abrupt altitude changes in turbulence. This can be a dramatic change when flying through areas of convective activity, associated with the creation of thunderstorm cells in the summer. The inside of a building cell contains strong up and downdrafts in close proximity, creating vertical windshears that can cause abrupt altitude changes of a few hundred feet. That’s why we will go way out of our way to circumnavigate these cells. Turbulence is categorized as light, moderate, severe, and extreme. I’ve been in extreme turbulence once in my life (November 11, 1994, IAD-ALB) and I spent the rest of my career making sure it never happened again.
You can also have these windshears in clear air, but it is rare for that to be as bad as in a developing cell. Clear air turbulence is usually associated with the jet stream, which is a core of high velocity air in the upper atmosphere. This core of air has a diameter usually less than 2000’, so a change in altitude can often result in a smoother flight. If an altitude change isn’t available (other traffic nearby), a change in course, or just flying a 5 mile offset from the course, might also do the trick.
If we’re stuck in turbulence, we slow to a “rough air penetration speed” which reduces the effect of the bumps, similar to slowing a small boat when in choppy water.