I see jets land daily by my work, but what is that sound 20 secs after a jet passes by?

Question

The planes are like 400ft in the air when they pass by. The sound isn't that loud and not a sonic boom, but sounds more like air filling a pocket...almost like the sound of paper getting ripped in half./ thanks!

**not smokin' when I see/hear these planes, Bitburge ;) They are commercial planes like Southwest or United. But yes, it's like 15-20 secs after the planes passes by. I'm going with the vortex answer.

It doesn't sound like the noise is coming from the airplane itself. The plane has landed a mile away so I don't think it's noise from the engine. It really sounds like air is rushing to fill a vacuum.

Answer 1

I know exactly what you're talking about!! I love to sit at the end of runways and watch the planes come in. My favorite place is by a park in Dallas just at the approach ends of 13R and 13L and I hear it every time a Southwest jet rolls in. I'm also a pilot and that exact sound is what we're trained to watch out for and avoid because it will flip smaller planes in a second. Here's a little teaser from wiki all about wake turbulence, and there is a link to where i got it with even more info, hopefully it will help you out!!

Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wingtip vortices and jetwash. Jetwash refers simply to the rapidly moving air expelled from a jet engine; it is extremely turbulent, but of short duration. Wingtip vortices, on the other hand, are much more stable and can remain in the air for up to two minutes after the passage of an aircraft. Wingtip vortices make up the primary and most dangerous component of wake turbulence.

Wake turbulence is especially hazardous during the landing and take off phases of flight, for two reasons. The first is that during take-off and landing, aircraft operate at low speeds and high angle of attack. This flight attitude maximizes the formation of dangerous wingtip vortices. Secondly, takeoff and landing are the times when a plane is operating closest to its stall speed and to the ground - meaning there is little margin for recovery in the event of encountering a different aircraft's wake turbulence.

Answer 2

Those would be the TR's.

The thrust reversers work in several different ways depending on the engine and airframe, but the key is that they re-direct thrust from the engines, (in varying amounts from by-pass air from the fan, to all of the thrust, depending on design,) to help the aircraft slow down.

They typically don't need to use the TR's for a very long period of time. Using the TR's makes the noise MUCH louder and changes the audible tone and pitch of the engines.

When you're on the airport and they're landing it's really noisy if someone comes in hot and is counting on the TR's to keep him from going off the end of the runway.

Next time you're on a flight, on a plane with underwing engines, try to get a seat just aft of the wing. The aft end of the engine will do one of two things; it will either slide backwards indicitave of a cascade type reverser, or it will close up, out and back to close like a clamshell behind the engine. In either case, the engine noise will become notably louder in the cabin for a few seconds until the pilot has slowed the aircraft to the point that he can control the aircraft with brakes and nose gear steering.

Answer 3

No it's definitely not vortex. you can't hear the vortex because the engines are much louder and also if it was vortex you would hear it at the time they pass. But if your closer than 2 miles to the airport and you see the planes on approach for landing phase then the sound is the reverse thrust from the engine which means they have touched down and it's pretty loud too, again it depends on which phase of flight the planes are when they pass by.

Answer 4

What you're hearing are vortices (aka wake turbulence) - violent little whirlwinds that are created at the wingtips of a plane as air is forced around the wing. They decend slowly, so that's why it takes 20 seconds to show up.

These things are dangerous to small airplanes flying underneath big airplanes.

Answer 5

It could be wingtip vortices, but 20 secs. sounds too long after the aircraft passes if it is only at 400'. It's more likely that you are hearing the thrust reversers operating as the jet touches down...

Answer 6

It does count upon the plane, yet maximum do have twin controls. And command ejection merely on the off risk each and every thing is going horribly incorrect. the united kingdom version of the F4 had the ability for rear controls notwithstanding the stick became usually bumped off. On OCUs the tutorial pilot became in the rear and the recent boy became in the front. The decrease back seat had very poor visibility, the merely ahead view became down a tunnel on both facet of the WSOs device panel. The rear seat throttles did no longer have administration of the reheat, so that you've been constrained to protection rigidity/dry capacity. i don't comprehend if different twin seat plane are further constrained.

Answer 7

That is definately the wingtip vortices that you are hearing. The parking lot at the airport I am based at is right under the final for one of the runways and I love that sound.

Answer 8

its the VORTEX in the air that trails the jet liner. it is also the reason that small air craft cant follow to closley. some have crashed doing so. a jet liner displaces air around it and the sound you here is the air returning.

Answer 9

Step away form the bong, Ben.

What kind of airplanes? Fighters? Commercial? Are you near an air base?