Commercial aircraft separation on landing

Factual Questions
#1

On final approach to LAX yesterday, there was another jet (a 747) almost precisely parallel to us–perhaps a mile away. Eventually we lost track of it (it was going just a tiny bit faster), but given its position and distance, it must have been landing on one of the 24L/R runways while we were on 25L/R.

I’d never been that close to another large craft in the air (well, let’s say outside of ground effect), and didn’t know they landed aircraft that way (typically, horizontal separation is 3 nautical miles near airports). I figured that they would generally stagger landing approaches.

A friend tells me that this kind of separation is allowed only for craft with special instrumentation. Anyone know any more details? Is this a pretty common thing that I’ve just somehow missed until now, or is it fairly recent and/or rare?

#2

Don’t know about instrumentation (the technology is changing rapidly - state of the art ten years ago is today’s almost-obsolete, but a few are still around.

Now:
Ever fly into SFO?

28R/L are very close, and are routinely used for simultaneous landings - two pieces of heavy iron on short final is something to see.

Pilots hate SFO.

#3

I live near SFO and have flown into it more than a few times, but never seen another plane land simultaneously–those runways are only 750 feet apart!

I guess it actually makes good sense–when right next to each other, the planes won’t even cause mutual wake turbulence (not necessarily the case if one plane is behind and to the side, depending on the circumstances). Still, that’s gotta be pretty unnerving.

I Googled a bit and ran into the acronym SOIA, for Simultaneous Offset Instrument Approach, which seems to be a set of technologies that allow landing on parallel runways as close as 750 feet. I’ll have to read up more on this…

#4

LSL Guy should be along soon.

Happens all the time. Go watch DFW traffic.

May be some new rules but if the runways are XXXX feet apart, they can Land / Takeoff in parallel but as you saw, in close they often are staggered due to different speeds. Those speeds can be requested by approach control or the tower.

When I was mapping the the Trinity River through the metro-plex it took two trips just to set it all up, meetings, maps for them, I got my very own personal approach control operator when I was doing the flying. Lucky that I did it in one day as it was very difficult, scary, wild, fun & worked out great.

We had big airplanes ( we were in a little Cessna 310 ) going every which a way above us, below us, to the right of us, to the left of us as we flew into the corridor of death. I could hear controllers in the background calming big iron pilots that yes, they knew About the little plan they just missed bu a few yards ( really was not that close but they were very goosey about what they were seeing even with being told what they were in for by the center controls before they ever got near DFW. )

Several times it seemed like all I could see out the front was a whole lot of aluminium. Worked perfect, controller was most excellent, much fun and much sweat. Everyone danced well together.

Way back in the early 70’s I was using a Cessna 180 to work a strip camera doing pipeline recon for the DOT. That is one picture 70mm wide and up to 250 feet long. We only had one line that we got one take that long without having to break off for one thing or the other.

Had a line that I was running North bound on the West side of Love in field in Dallas one day. We flew these at 1950 ft with an RADAR altimeter in addition to other instruments and visual clues to hold the altitude as close as we could. That is not the deal, the deal was I had been working with one particular approach controller for over an hour & he knew what we were doing and what we needed. So as I was going up that side, I could see two airliners aide by side making their approach to the parallel N/W, S/E runways so I told him to tell me when he wanted me to break off & that I had them in sight. He told me to go to tower frequency as he had been briefed. (my altitude would also be their altitude on their approach crossing that N/S line I was flying. )

The tower said to just hold on, he though it was going to work out just fine. He got the two airliner pilots to get a visual on me, ( a 727 & maybe a 707 or DC-8 ) and to just make a normal approach. That it looked like I would cross in front of the 4 engine and behind the 727. As we all got closer together he said it looked like it was going to work well.

It did. I slid right across in front of the 4 engine and behind the 727 and it’s wake turbulence had sank just enough to not even ripple us.

When conditions are IFR, different separation rules / distances apply.

Many large airports have dual runways now, even more than twoand they are designed for the most part for simultaneous use.

#5

My flying days are 15 years rusty, but … IIRC, even in instrument flight conditions (IFC), a one mile separation is authorized for precision approaches with radar coverage. Those runways are one mile apart. In good weather, it may be even closer as long as aircraft have confirmed visual contact with the other.

#6

The FAA allows unrestricted parallel-runway operations if the distance between them, measured at their centerlines, is 4300 feet or more. It’s an issue at older, space-constrained airports like SFO.

#7

This is pretty well answered already, at least conceptually. To put all the pieces in a single place …

If the runways are close enough together they are treated as effectively 1 runway and you need fore/aft spacing between aircraft on the adjacent runway.

For intermediate spacing between runways you need less fore/aft spacing but you still need some.

And for runways far enough apart, they’re operated independently and aircraft can be side by side down final.

And for some airports with enough traffic to warrant it, intermediate spacing runways can be used for side by side approaches with extra monitor controllers, fancy radar, and special pilot procedures. And there are two flavors of this depending on runway spacing & sophistication of equipment.

As well there are standards for maintaining different altitudes on the base leg leading to final. That way if somebody muffs the turn-in the aircraft pass over & under, rather than meeting in the middle.

The details also differ between clear days vs. cloudy weather and are also impacted by the relative sizes of the airplanes.

All in all a lot of thought goes into deciding how to blend two flows of jets into two parallel runways. Mostly this is ATC’s problem to solve, not a pilot’s. But we’re still watching everything closely & will protest when a poor spcing situation appears to be developing. Or *in extremis *take our jet out of harm’s way.

Life gets easy for both pilots and controllers at new airports built from scratch to be spread-out enough to support independent parallel ops. The older more space constrained airports are a PITA for everybody every day.

And back to the OP: LAX’s runways are just barely far enough apart to use the side-by-side-approach-spacing-with-extra-radar procedures.

Speed control is used up to about 5 miles from the runway in an attempt to keep each runway’s flow as compact as possible. IOW, go fast to catch up just close enough to the guy ahead, then slow to a common speed to hold that spacing. For the last 5-ish miles, each aircraft flies the speed it needs to based on aircraft type and weight.

Assuming everybody slows at 5 miles more or less as expected, lands normally, brakes normally & pulls off on a convenient taxiway promptly, the next jet gets to the runway only a few seconds after the previous one has gotten off. This max-performs the airport’s capacity to move traffic.

It’s quite a ballet.

#8

I believe one of the design features of Denver’s airport was to have 3 runways available for use at the same time - that’s why it is so big.

#9

Meh. Oshkosh turns a taxiway into a runway once a year and the separation is 550 feet between center lines. They land aircraft continuously with multiple planes on the same parallel runways at the same time.

#10

I’m pretty sure they aren’t landing 747’s, though! I have a long-disused private license and am used to getting pretty close to other small craft. Not to mention having to do go-arounds if the guy in front of me was a slowpoke and wasn’t getting to a taxiway fast enough. It’s quite another thing with a pair of big birds, even at much longer distances.

Thanks all for the responses, particularly GusNSpot and LSLGuy. Great information there.

#11

Can anyone provide details? Thx.

#12

Captain Sum Ting Wong and First Officer Wi Tu Lo think so.

Magiver, you’re omitting the small detail about the sizes and speeds of the aircraft in the very-special Oshkosh pattern.

#13

The runway realignment currently underway at O’Hare is also (I believe) designed to allow for three E-W runways to be used simultaneously. This comes at the expense of having only one runway available when there’s a strong wind from the north or south.

#14

This PDF seems to suggest degrees of independence for parallel runways based on centerline separation distance (see pages 4-5):
[ul]
[li]Less than 2500 feet: They must effectively operate as a single runway[/li][li]2500-4300 feet: 1.5 nautical mile diagonal distance between two planes that are either both landing or both taking off.[/li][li]Greater than 4300 feet: They can operate independently; side-by-side approaches or departures are OK.[/li][/ul]That assumes that they’re aligned lengthwise. As the document says,