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OT: This Is One of the Reasons Aircraft Wait On the Runway

RutgersRaRa

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The title of the vid intrigued me, so I thought I'd click on it, get my answer in a minute, then click off it. I watched all eight minutes. It was partly what I expected, but with more (and much-appreciated) detail. Gotta love a good nerdfest.

 
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My son is a pilot student at St. Louis Univ...I shared the link with him... interesting if that's your line of business, or your kid's line of business.
 
My son is a pilot student at St. Louis Univ...I shared the link with him... interesting if that's your line of business, or your kid's line of business.
Very cool about your son flying as a Billiken, and hope it helps him in some way. I'm pretty sure it's fairly basic stuff for a student of aviation, but nonetheless the physics is fascinating to me. It's not my line of work, just something we all experience when we fly and it's pretty cool to know what's going on. I knew about jet wash, but I didn't know it was more about the vortices coming off the wings and that they affect aircraft at lower altitudes. I also did not expect that they would affect military fighters, as I thought they'd just power through any turbulence created by another fighter. Apparently that's not so.
 

OT: This Is One of the Reasons Aircraft Wait On the Runway​

I always thought it was a woman flying away forever after her lover breaks up with her and realizes it was a mistake. So in a last chance effort to stop her, he prevents the take-off on the runway so he can tell her that he loves her. They embrace and the movie can now have a happy ending.

You're telling me, with this video, that's NOT the case?
 
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OT: This Is One of the Reasons Aircraft Wait On the Runway​

I always thought it was a woman flying away forever after her lover breaks up with her and realizes it was a mistake. So in a last chance effort to stop her, he prevents the take-off on the runway so he can tell her that he loves her. They embrace and the movie can now have a happy ending.

You're telling me, with this video, that's NOT the case?
That was also the last episode of F.R.I.E.N.D.S. 😂
 
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Yeah the wake can be dangerous. During the cold war we used to have bomber drills where we'd launch 20 B-52s in less than 10 minutes. Absolutely bonkers, those things kick up just about the most wake imaginable.
@Joey Bags How many engines did they have—6? Were they Pratt & Whitney, or did Rolls Royce recover from WW2 by then and make them? Or perhaps Boeing? (Does Boeing even make engines?) I don’t know much about the B-52 other than a few things I picked up over the years. I saw one at an air show years ago and it pulled into an ascending turn as soon as it was wheels up, and even though it was empty I couldn’t believe the thing had that kind of power to maintain lift.
 
@Joey Bags How many engines did they have—6? Were they Pratt & Whitney, or did Rolls Royce recover from WW2 by then and make them? Or perhaps Boeing? (Does Boeing even make engines?) I don’t know much about the B-52 other than a few things I picked up over the years. I saw one at an air show years ago and it pulled into an ascending turn as soon as it was wheels up, and even though it was empty I couldn’t believe the thing had that kind of power to maintain lift.
It actually has 8 P&W engines on 4 pylons if you can believe it. Though by modern standards the engine technology is pretty antiquated hence the two engines per pylon design.
 
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@Joey Bags How many engines did they have—6? Were they Pratt & Whitney, or did Rolls Royce recover from WW2 by then and make them? Or perhaps Boeing? (Does Boeing even make engines?) I don’t know much about the B-52 other than a few things I picked up over the years. I saw one at an air show years ago and it pulled into an ascending turn as soon as it was wheels up, and even though it was empty I couldn’t believe the thing had that kind of power to maintain lift.
Boeing doesn't make engines as far as I know. GE, P&W and RR make engines.
 
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A few of the clips are from Princess Juliana International on the island of Saint Martin. The runway is basically up against a small beach where you can stand directly behind the planes as they takeoff. Depending on the size of the aircraft it is a miserable experience that everybody should try at least once.
 
As someone who is a lifetime million + mile flyer, I can recall two such instances where I experienced the vortices, albeit minor instances, when flyer 50 seat Embraer's landing at Newark. The quick rotating action of the airplane was very different (and scary) than a wind gust which bounces you up and down or pushes you side to side. Confirmed both instances with the pilots upon exiting the aircraft.
 
As someone who is a lifetime million + mile flyer, I can recall two such instances where I experienced the vortices, albeit minor instances, when flyer 50 seat Embraer's landing at Newark. The quick rotating action of the airplane was very different (and scary) than a wind gust which bounces you up and down or pushes you side to side. Confirmed both instances with the pilots upon exiting the aircraft.
@MCY What was that like--did you start to roll a little bit? Once in ground effect I think the dynamics make it harder to tip a wing, but for an Embraer that's probably within 30 feet of touchdown so my guess is you hit the vortex before that. And when those weird motions occur they can be seriously unsettling. Aircraft are incredibly stable, but your stomach doesn't know that when the craft suddenly goes in some weird direction.
 
Huh. And I always thought it was so the pilots can do one last line each before takeoff.

You learn something new every day.
 
@MCY What was that like--did you start to roll a little bit? Once in ground effect I think the dynamics make it harder to tip a wing, but for an Embraer that's probably within 30 feet of touchdown so my guess is you hit the vortex before that. And when those weird motions occur they can be seriously unsettling. Aircraft are incredibly stable, but your stomach doesn't know that when the craft suddenly goes in some weird direction.

It was a quick jerking motion (I think to the left) and then right back to level. I'm sure we did not roll more than 10 to 15 degrees, but it was very quick and then back just as quick so it was very noticeable.
 
There's been a real impact to airport throughput due to the increase in heavy jets in major carriers' fleets. The more heavy jets, the longer the wait time for lighter aircraft behind them.

Overscheduling doesn't help. At peak hours, EWR has an average throughput of 63 operations per hour. There are usually about 75 scheduled during those same peak hours. Ain't everybody leaving on time.
 
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There's been a real impact to airport throughput due to the increase in heavy jets in major carriers' fleets. The more heavy jets, the longer the wait time for lighter aircraft behind them.

Overscheduling doesn't help. At peak hours, EWR has an average throughput of 63 operations per hour. There are usually about 75 scheduled during those same peak hours. Ain't everybody leaving on time.
Does throughput entail both arriving and departing flights?
 
Does throughput entail both arriving and departing flights?

Absolutely. As you heard in the video, the minimum separation on arrival behind heavy jets is 8nm, but only 4 behind anything smaller. That's a 4nm difference, which at approach speeds equates to about a minute and a half.

It's worth noting that a lot of medium to long-range aircraft popular in the fleet today are replacing lighter aircraft. The 737 is a great example - developed originally to be a medium-weight, medium-range aircraft, every current iteration of the 737 is now a heavy aircraft.
 
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Absolutely. As you heard in the video, the minimum separation on arrival behind heavy jets is 8nm, but only 4 behind anything smaller. That's a 4nm difference, which at approach speeds equates to about a minute and a half.

It's worth noting that a lot of medium to long-range aircraft popular in the fleet today are replacing lighter aircraft. The 737 is a great example - developed originally to be a medium-weight, medium-range aircraft, every current iteration of the 737 is now a heavy aircraft.
Sounds like airports with dual runways such as O'Hare might themselves run into scheduling difficulties in spite of their additional capacity, simply because the same dynamic applies once they're at full throughput. But it gives them more scheduling options vis-a-vis aircraft size, unless the location of terminals dictates where the aircraft can be set down.
 
Sounds like airports with dual runways such as O'Hare might themselves run into scheduling difficulties in spite of their additional capacity, simply because the same dynamic applies once they're at full throughput. But it gives them more scheduling options vis-a-vis aircraft size, unless the location of terminals dictates where the aircraft can be set down.

The big airports with parallel operations are, of course, O'Hare and Hartsfield-Atlanta. The limiting factor at both airports is gate space. It often is in Newark, as well - not in spite of, but because of the throughput limitation.
 
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Yeah the wake can be dangerous. During the cold war we used to have bomber drills where we'd launch 20 B-52s in less than 10 minutes. Absolutely bonkers, those things kick up just about the most wake imaginable.


9 B-52s and 5 KC-135s in under 5 minutes and enough exhaust to lower global temperatures by 2 degrees C
 
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@RUTGERS95 Jet wash, vortices, descending vortices, sequential engine-size variables on takeoff, and so on. Completely digestible info.
exactly.. sudden loss of lift which is generated by speed and the wing shape and oncoming winds... jetwash can change that formula rather dramatically.

I would hate to know how they figured that out way back when. I would love to find out that it happened because of some maths/physics gurus and not found by "accident"... again and again.
 
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