Ask The Pilot

[QF WP]

Now I can see why it would be an issue. Would be interesting to see it in a wind tunnel experiment to understand the forces at work. Swirling air certainly wouldn't make it easy

 

[jb747]

At altitude, you can often clearly see the rotation, as the vortexes grab the contrails. They persist for quite some time, not just seconds, but often minutes. They also drift downwind, and tend to descend.

When you encounter one laterally (i.e. you cross it), it will give the aircraft a very good 'thump'. But, when you hit one from an aircraft travelling more or less in the same direction (or 180 out), you will normally only hit one of the cores, and it will give a very strong rolling moment to the aircraft. A 737 sized aircraft can easily be rolled onto its back by such an encounter.

The 757 was renowned for producing wake turbulence out of all proportion to its size.

Whilst flying a bigger aircraft makes you less susceptible to the nasties, you are't immune. I recall chatting to one of our 747 pilots, who made the comment that he'd hit our wake, and that it wasn't nice, and I ran into a Singair 380s wake just after take off in Singapore, and even the big fella reacted to it. Having said that though, it's more an inconvenience for the big aircraft, but is very dangerous for the smaller aircraft.

 

[spudseamus]

A 737 sized aircraft can easily be rolled onto its back by such an encounter.:shock: wow!

 

[jb747]

FAA Wake turbulence test - YouTube

Some film from testing involving a 727 and a 737...which aren't all that different in size.

 

[MEL_Traveller]

At altitude, you can often clearly see the rotation, as the vortexes grab the contrails. They persist for quite some time, not just seconds, but often minutes. They also drift downwind, and tend to descend.

When you encounter one laterally (i.e. you cross it), it will give the aircraft a very good 'thump'. But, when you hit one from an aircraft travelling more or less in the same direction (or 180 out), you will normally only hit one of the cores, and it will give a very strong rolling moment to the aircraft. A 737 sized aircraft can easily be rolled onto its back by such an encounter.

The 757 was renowned for producing wake turbulence out of all proportion to its size.

Whilst flying a bigger aircraft makes you less susceptible to the nasties, you are't immune. I recall chatting to one of our 747 pilots, who made the comment that he'd hit our wake, and that it wasn't nice, and I ran into a Singair 380s wake just after take off in Singapore, and even the big fella reacted to it. Having said that though, it's more an inconvenience for the big aircraft, but is very dangerous for the smaller aircraft.

I was on a qf flight ex Singapore about 10 years ago when we hit wake turbulence. it was strong enough to give us a good thump as you describe, all the blankets, pjs and amenity kits were knocked off the ottomans and side panelling (between the seat and window). one pax had a bottle of water knocked to the ground.

what osmit with wake turbulence ex sin!!??

 

[jb747]

I was on a qf flight ex Singapore about 10 years ago when we hit wake turbulence. it was strong enough to give us a good thump as you describe, all the blankets, pjs and amenity kits were knocked off the ottomans and side panelling (between the seat and window). one pax had a bottle of water knocked to the ground.

Actually that sounds like he ran into a cloud, rather than wake....

 

[oz_mark]

Maybe it was a good thing I was in an A330 then!

I thought the approach into Perth later on was more bumpy. Darn summer easterly winds rolling over the scarp.....


Anyway, I had'nt thought much about it before, but sometimes when doing loops somewhere waiting to land in Sydney, there are these single hard jolts. Is that possibly crossing someones wake, or something else?

 

[jb747]

Maybe it was a good thing I was in an A330 then!

I thought the approach into Perth later on was more bumpy. Darn summer easterly winds rolling over the scarp.....

It's not just the wind. On those really hot days, the updrafts are very strong, and make for anything but smooth flying conditions.

Anyway, I had'nt thought much about it before, but sometimes when doing loops somewhere waiting to land in Sydney, there are these single hard jolts. Is that possibly crossing someones wake, or something else?

Perth is quite renowned as being a difficult place. Subject to quite nasty weather at times, and a lack of reasonable alternates....

A single jolt certainly sounds like wake. And whilst you may well be hitting that from other aircraft, it's not impossible to hit your own wake.....

 

[MEL_Traveller]

Actually that sounds like he ran into a cloud, rather than wake....

Except the captain came on and apologised - saying we ran into wake turbulence

 

[simonpenny408]

Patrick Smith wrote about it a couple of months back and also posted a recording of the SOUND it makes even on the ground Into the vortex - Ask the Pilot - Salon.com

 

[oz_mark]

Perth is quite renowned as being a difficult place. Subject to quite nasty weather at times, and a lack of reasonable alternates....

Something they really need to do something about. Sometimes there's really only the cross runway to use, and if someone blows a tyre or something, you're going to have a bunch of planes looking for somewhere else to go.

 

[jb747]

This is Australia. Nothing will be done about it until after the incidents. And then it will be someone else's fault.

 

[reductionist]

When you encounter one laterally (i.e. you cross it), it will give the aircraft a very good 'thump'.

Ahh, I was on a flight around a decade ago on which this happened. Scared the absolute cough out of me. The pilot was quick on the PA to explain what happened which was reassuring.

 

[reductionist]

it's not impossible to hit your own wake.....

Ooh. That sounds interesting. How could this happen?

 

[jb747]

Ooh. That sounds interesting. How could this happen?

Holding pattern. Just need the wind in the right direction, and a descent of the right amount, at the right time.

 

[reductionist]

Thanks JB.

 

[serfty]

Ahh, I was on a fleveryone ight around a decade ago on which this happened. Scared the absolute cough out of me. The pilot was quick on the PA to explain what happened which was reassuring.

Happened to us on a flight DFW-SEA (AA 737) - out of the blue came a solid twitch/shudder followed by significant bouncing for about 2 seconds. My drink actually began to topple (Was in bulkhead 3E/F) and as I grabbed it the Captain came on the PA and announced in an urgent tone along the lines of "seatbelts on NOW and brace for turbulence". Sure enough, a long seeming 5 seconds later there was another significant twitch/shudder etc.

Soon afterwards the pilot came on and stated that the aircraft had passed through the wakes of a 747. Vertical separation apparently was the issue.

 

[JohnM]

I once encountered what I think must have been wake turbulence on approach into LAX from SEA quite a few years ago. It was a UA flight in a B727 or maybe a B737 and I was listening to the pilot talk that UA used to (maybe still does?) put through the audio system.

Suddenly some cracking thumps that seemed to quite different from typical turbulence occurred and the pilot made some comment to his co-pilot about a 'heavy'. My recollection is that they seemed quite surprised by it and were looking about to try to identify the source. I think they fingered a DC10.

Is anyone aware of whether many airlines feed the pilots' talk through the IFE system these days?

I guess if they do it would get killed immediately any emergency situation arose?

jb: what constitutes an aviation-speak 'heavy'?

 

[markis10]

United still provide a pilot feed through its entertainment system on some services I believe, using the work entertainment loosely!

 

[jb747]

Is anyone aware of whether many airlines feed the pilots' talk through the IFE system these days?

I guess if they do it would get killed immediately any emergency situation arose?

Another switch to recall when busy. There are various pros and cons to this...but I'd have to admit that I belong to the anti camp. Many things are said which would worry people without the appropriate knowledge, or context.

jb

: what constitutes an aviation-speak 'heavy'?

There's a weight criteria, which I can't recall, but basically 767 and up, with the 757 also included, even though it is below the nominal weight. The 380 is 'super'...though I'd prefer 'fatso'.