Ask the Captain: When turbulence comes in waves
— -- Question: While flying across the Pacific from Hong Kong to the U.S., the plane began to go up and down exactly like a boat heading into waves. The effect was such a roller-coaster sensation that several passengers let out short yelps as we went over each "wave." This was a new sensation - not at all like heavy turbulence. No one explained it - they just smiled professionally when I asked about it. I'd sure like to know what that was all about.
— submitted via e-mail
Answer: What you describe was probably the result of a nearby jetstream. Jetstreams are fast moving cores of air (sometimes over 200 miles per hour) that can cause turbulence. There can be waves created as air is compressed, expanded and moved by these jetstreams. As your flight progressed by the jetstream, it experienced some slow up and down motion in the air similar to a wave on an ocean. Usually there is no turbulence in such situations, however if the flight gets into the wrong part of a jetstream there can be severe unexpected turbulence. This is known as clear air turbulence and has been the cause of numerous passenger and flight attendant injuries. Keeping your seatbelt fastened when in your seat is the best way to avoid being injured if encountering such turbulence.
Q: I was recently on a 757-200 from Los Angeles to Newark and we were about a third of the way to the destination. We were flying normally, straight and level, when the sounds of the right engine started gradually increasing. It was not unlike the roar of a blowtorch, or one of those garage heaters called a salamander. The sound became substantially louder, and quite noticeable to me, but no one else seemed to pay any attention. Then, after about 10 to 12 minutes, the sound gradually subsided, and returned to normal. Obviously nothing was amiss, as we continued to Newark with no problems. What do you think was going on?
A: It is speculative since I was not there, but based on your description, the highest probability is that your flight climbed to a higher altitude. The additional sound was the engines powered up to produce the additional thrust for the climb.
Q: I was on a flight from China to SFO. About 5 hours out of Shanghai, we were flying in the middle of the vast Pacific Ocean when I felt our B747-400 making a very sharp (perhaps) 180 degree turn, and then another 180 degree turn. I felt a little scared and I got a little dizzy from the sharp and sudden turns. Since most of the passengers were asleep, the captain did not explain these unusual flight maneuvers. What do you think were the reasons for those turns?
— Submitted by reader zzyyzzyyxx
A: Making large turns while in cruise is unusual. Without more information, I can't give you an opinion. Sorry.
Readers, please leave your questions for John Cox here, and only leave comments about this week's column below.
John Cox is a retired airline captain with U.S. Airways and runs his own aviation safety consulting company, Safety Operating Systems.