Postal Letter

Killer airplane trail?

yesterday, my i went with my aunt towards the L.A.X. airports local U.S. postal office, only open till 11,and she needed to send something urgent. bored , i walked outside, after waiting & watching a few planes go on by, i noticed they left the trail of condensation i guess , but after the plane had gone on about 200 meters, i looked up randomly and i saw the same exact trailings whizzing only a few hundred feet from the ground. i swear it was the trails only because it was traveling so fast and it suddenly dissappeared. it happened again only with another airplane that was leaving no trail, after going further ahead, the airplanes thunderous noise came back and sounded like it was going in a circle, and then suddenly stop. it wasn't scary or anything,or at least i didn't think i should have been scared . i was just wondering if anyone could explain it or maybe say if they have experienced similar.

Public Comments

1. What you most likely saw where wingtip vortices. They commonly streak from wingtips and props. http://www.airliners.net/open.file/1224429/L/ http://www.airliners.net/open.file/1224645/L/ http://www.airliners.net/open.file/1219874/L/ The vortice is a side effect of the generation of lift. Because there is high pressure below the wing and low above, the air wants to go to the low pressure section. If the aircraft is in a high angle of attack, these vortices become visible. During airshows at high G manouvers ( such as a loop) you can also see these.
2. You were hearing the wind vortex's coming off of the wing. Its a very cool phenomenon that occurs when the airplanes wing is generating lift. If there is moisture in the air, you can see them better ( Like high humidity, light rain/mist, etc.) Basically, they are horizontal tornado's that come off the wing tips of an airplane. These can be extremely dangerous if a small airplane flies into them (wake turbulence), but to people on the ground, they are usually harmless (Watch the movie "Pushing Tin")
3. the higher Gs the aircraft pulls and the higher the air humidity is, the more likely are the condensation vortexes to appear. I once saw the contrail behind th helicopter :) all condensed water vapours behind the main rotor.
4. 727s used to be the best for doing it. After it had landed and turned off the runway, you'd hear this sound like tinfoil being ripped right above your head. It is the wingtip vortices mixing with the undisturbed air.
5. Localized temperature and pressure differentials around the airframe cause the condensation. Air is accelerated at certain points around the airframe. Condensation can occur. Then the condensation (re)evaporates. Sounds like you heard the aircraft's thrust reversers after it landed, an unrelated source of noise.