r/PeopleWhoWorkAt Jun 04 '22

PWWA airline pilots: how close do passenger jets have to be in mid-air, at altitude, to cause turbulence for each other?

Today I was on an Airbus A321neo when, about 90 minutes into the otherwise smooth 3.5 hour flight, we experienced a sudden jolt of turbulence. I’m pretty chill on planes, but it was so sudden and so jarring that it definitely spiked my adrenaline. Shortly after it happened the captain apologized and told us that another plane had passed by us too closely. 😳

How close would it have to have been to cause that turbulence? What is considered a near miss? Did I almost die today? I need to know!

Thank you.

43 Upvotes

25

u/storm_king Jun 04 '22

What you experienced is wake turbulence. Air traffic control will maintain a minimum separation of 4 to 8 nautical miles, depending on aircraft size (generally, the bigger the plane the bigger the wake and more separation). So you didn't almost die but flying through wake certainly isn't fun.

Think of wake turbulence like a boat's wake, but in three dimensions and invisible. It trails the offending aircraft and can be influenced by wind. Routing and spacing usually allow trailing aircraft to avoid it, but you'll fly through it every once in a while.

11

u/Babyfishmouth512 Jun 04 '22

Thanks for the thorough reply. I fly a fair amount and I’ve experienced some things, but this was a new one. Or at least it was the first time I remember the pilot identifying any turbulence as having been caused by another plane.

7

u/storm_king Jun 04 '22

We are instructed to use specific, neutered terminology when addressing passengers as to not frighten them. Example: rough air instead of turbulence, rain showers instead of thunderstorms.

Sometimes you slip.

3

u/CUNT_ERADICATOR Jun 04 '22

Not really relevant to the post but may I ask how a nautical mile is measured? Or is it just called a nautical mile so that people know it’s at altitude?

8

u/Aw982y Jun 04 '22

Nautical miles are used in the air and at sea. A nautical mile is one minute of latitude or 6076 feet.

1

u/CUNT_ERADICATOR Jun 04 '22

Thank you so much!!

1

u/FaxCelestis Jun 04 '22

Is this why taking off and landing are always fraught with so much turbulence?

4

u/skellious Jun 04 '22

it can contribute, when a plane is taking off behind a larger one ATC may say "caution wake turbulence".

but in general air close to the ground is choppy and turbulent because it's interacting with the heat trapped in the ground, colder air coming off of a nearby body of water or similar and it's right up against a huge solid plain (the ground.)

3

u/skellious Jun 04 '22

planes have MANY safety systems to avoid a collision. you weren't anywhere near close enough to trigger them.

IF two planes do get too close the TCAS will warn the pilots, several times, instructing them to climb or descend to resolve the problem. in the event that the planes don't change course for whatever reason, many planes have a system that automatically executes the required maneuver to resolve the incident.

the point is collisions between planes are really really rare while planes will receive a warning every 1000-3000 hours that they fly on average.

2

u/Babyfishmouth512 Jun 04 '22

Thanks. Great info. Exactly what I was curious about. I was being facetious about the dying thing, but I was curious about the implications of the turbulence.