I've noticed at many airports (MIA, LAX to name two) that have parallel runways where one is used for landings and the other for takeoffs, that the plane that will be taking off "lines up and waits" until the plane landing on the runway next to it has almost touched down.

Is this because the thrust from the plane taking off would interfere with the plane landing?

Caveat: I'm not ATC.

It think it is in case the landing plane goes around and potentially impinges on the departure path. Of course, the landing plane could initiate a go-around even after touchdown, but I guess that is less likely.

It isn't because of thrust or wake turbulence.

I'm ATC but not at those airport so I can't say for certain this is the cause. I think the situation you're describing is Simultaneous Same Direction Operations (SSDO). Basically because the edges of the runways for LAX north complex are less than 600 feet apart, you may not have a simultaneous operation if one of the aircraft is a heavy jet. On the south complex, the runway edges are over 600 feet apart so you may SSDO with all aircraft. So basically the heavy jet may not overtake the other aircraft during landing or takeoff roll. Once the other aircraft has completed landing roll (taxi speed) or is airborne (takeoff roll), the heavy may then overtake. For example, if a heavy jet is 10 seconds from crossing the landing threshold, and you clear an A321 for takeoff on the parallel, if the heavy overtakes the A321 prior to it becoming airborne, you have an operational loss. JO7110.65 TBL 3-8-1 is the SSDO chart. Now MIA seems to be more than 600 feet apart. This could be something built into their facility specific SOP or just because the controller wants to be on the safe side in the event of a go around.

Thanks for the reply jetboy757. That does clear things up.

LAX uses LUAW for basically all departures. This is to increase runway usage with IFR spacing.

N1120A wrote:

LAX uses LUAW for basically all departures. This is to increase runway usage with IFR spacing.

Can you explain what all that means?

AAPilot48Heavy wrote:

N1120A wrote:

LAX uses LUAW for basically all departures. This is to increase runway usage with IFR spacing.

Can you explain what all that means?

Line up and wait. Planes taxi onto the runway and hold until the runway is clear, then they take off.

AirKevin wrote:

AAPilot48Heavy wrote:

N1120A wrote:

LAX uses LUAW for basically all departures. This is to increase runway usage with IFR spacing.

Can you explain what all that means?

Line up and wait. Planes taxi onto the runway and hold until the runway is clear, then they take off.

Not when the runway is clear...
They hold until issued a takeoff clearance by ATC. Then they take off. But as far as I am aware, the takeoff clearance is not associated with anything happening with landing aircraft on a parallel runway.

When landing on LAX 25L for example, Tower will advise that a heavy aircraft is departing the inboard runway (25R) but that is for awareness purposes.

Woodreau wrote:

AirKevin wrote:

AAPilot48Heavy wrote:

Can you explain what all that means?

Line up and wait. Planes taxi onto the runway and hold until the runway is clear, then they take off.

Not when the runway is clear...
They hold until issued a takeoff clearance by ATC. Then they take off. But as far as I am aware, the takeoff clearance is not associated with anything happening with landing aircraft on a parallel runway.

When landing on LAX 25L for example, Tower will advise that a heavy aircraft is departing the inboard runway (25R) but that is for awareness purposes.

I guess I put it in really simple terms because I assumed it was obvious that tower would have to issue the take-off clearance first, which they wouldn't do until the runway was clear.

AAPilot48Heavy wrote:

N1120A wrote:

LAX uses LUAW for basically all departures. This is to increase runway usage with IFR spacing.

Can you explain what all that means?

AAPilot48Heavy, I am not an air traffic controller, but here is my best explanation to you based on flight experience:

Air Traffic Controllers must maintain minimum aircraft separation when controlling aircraft operating on IFR flight plans. As a result, a local controller (Tower) cannot clear aircraft for takeoff immediately, one after another, because sufficient separation may not exist as the aircraft are handed off from Tower control to Departure control. I'm not positive on how much that separation is, but my recollection is that in a terminal area the separation is 3 nm horizontally and 1000 feet vertically; 5 nm horizontally in the enroute sectors. Perhaps some air traffic controllers on this forum can provide a more definitive answer on proper separation.

Nevertheless, to minimize delays and keep traffic moving, tower controllers will have succeeding aircraft line up and wait--LUAW--on the runway until such time as appropriate separation exists from the preceding departure (and the runway is clear). Aircraft landing on parallel runways are frequently cleared to cross the departure runway during this period. LAX, mentioned previously, is a good example.

The minimum separation I mentioned above can be adjusted under certain circumstances; i.e., type of operation (IFR/VFR) and if the departure procedure assigned to be flown by the succeeding aircraft will diverge from the preceding aircraft. At some airports--in VMC conditions--I have been cleared for takeoff immediately behind another aircraft after tower asked if I had the previous aircraft in sight and I reported "affirmative." So under certain conditions, there are exceptions to the separation criteria to which air traffic controllers must adhere. In addition, some airports have letters of agreement between local control and TRACON defining the parameters between aircraft separation and handoff procedures.

e38

e38 wrote:

AAPilot48Heavy wrote:

N1120A wrote:

LAX uses LUAW for basically all departures. This is to increase runway usage with IFR spacing.

Can you explain what all that means?

AAPilot48Heavy, I am not an air traffic controller, but here is my best explanation to you based on flight experience:

Air Traffic Controllers must maintain minimum aircraft separation when controlling aircraft operating on IFR flight plans. As a result, a local controller (Tower) cannot clear aircraft for takeoff immediately, one after another, because sufficient separation may not exist as the aircraft are handed off from Tower control to Departure control. I'm not positive on how much that separation is, but my recollection is that in a terminal area the separation is 3 nm horizontally and 1000 feet vertically; 5 nm horizontally in the enroute sectors. Perhaps some air traffic controllers on this forum can provide a more definitive answer on proper separation.

Nevertheless, to minimize delays and keep traffic moving, tower controllers will have succeeding aircraft line up and wait--LUAW--on the runway until such time as appropriate separation exists from the preceding departure (and the runway is clear). Aircraft landing on parallel runways are frequently cleared to cross the departure runway during this period. LAX, mentioned previously, is a good example.

The minimum separation I mentioned above can be adjusted under certain circumstances; i.e., type of operation (IFR/VFR) and if the departure procedure assigned to be flown by the succeeding aircraft will diverge from the preceding aircraft. At some airports--in VMC conditions--I have been cleared for takeoff immediately behind another aircraft after tower asked if I had the previous aircraft in sight and I reported "affirmative." So under certain conditions, there are exceptions to the separation criteria to which air traffic controllers must adhere. In addition, some airports have letters of agreement between local control and TRACON defining the parameters between aircraft separation and handoff procedures.

e38

Thank you, sir.

e38 wrote:

AAPilot48Heavy, I am not an air traffic controller, but here is my best explanation to you based on flight experience:

Air Traffic Controllers must maintain minimum aircraft separation when controlling aircraft operating on IFR flight plans. As a result, a local controller (Tower) cannot clear aircraft for takeoff immediately, one after another, because sufficient separation may not exist as the aircraft are handed off from Tower control to Departure control. I'm not positive on how much that separation is, but my recollection is that in a terminal area the separation is 3 nm horizontally and 1000 feet vertically; 5 nm horizontally in the enroute sectors. Perhaps some air traffic controllers on this forum can provide a more definitive answer on proper separation.

Nevertheless, to minimize delays and keep traffic moving, tower controllers will have succeeding aircraft line up and wait--LUAW--on the runway until such time as appropriate separation exists from the preceding departure (and the runway is clear). Aircraft landing on parallel runways are frequently cleared to cross the departure runway during this period. LAX, mentioned previously, is a good example.

The minimum separation I mentioned above can be adjusted under certain circumstances; i.e., type of operation (IFR/VFR) and if the departure procedure assigned to be flown by the succeeding aircraft will diverge from the preceding aircraft. At some airports--in VMC conditions--I have been cleared for takeoff immediately behind another aircraft after tower asked if I had the previous aircraft in sight and I reported "affirmative." So under certain conditions, there are exceptions to the separation criteria to which air traffic controllers must adhere. In addition, some airports have letters of agreement between local control and TRACON defining the parameters between aircraft separation and handoff procedures.

e38

An wonderful explanation.

Minimum IFR separation is 3 NM either side by side or in-trail of one another, UNLESS wake turbulence separation is required behind the preceding departure. The exact separation is determined by the aircraft in front as well as aircraft following all based upon type involved.

In your example of using visual separation normally it won't be used for aircraft departing on the same SID, but is often used for departing on the same initial heading or track and then the routes will diverge down the road prior to getting into center airspace. Initial diverging headings or routes we can clear the following departures once the preceding departure is up, though in hard IFR it is a good practice to wait until the first has show up on RADAR in the tower just to verify where they are as the controller won't be able to see them visually. Having a good ground control sequence with diverging routes really helps the local controller move the departures quickly.

Source: I am a controller at LAX.

We don’t have to apply SSDO, the runway centerlines are all far enough apart to not need it.

To the OP’s question, we are not waiting for the arrival to land or be short final before we depart an aircraft off the parallel. We are waiting for appropriate IFR separation for for the departing aircraft, as well as runway separation for both the departing and arriving aircraft. To give some insight into a small small slice of the reason you seem to see the planes “racing” with one touching down as the other is passing 80kts on departure roll, I’ll give you the following common scenario.

Plane D1 departs, 24L, on a northbound SID, plane A1 arrives as D1 is already at the beach, and plane D2 is “lining up and wait”. Plane D2 is on a southbound SID, and has to fit into the flow of traffic off of 25R. The controller working the 25’s tells the controller working the 24’s which plane D2 is going to follow. Meanwhile plane A2, say an A321, is on a one mile final to 24R and plane A1 is exiting AA. To avoid being “late” with their southbound D2 aircraft, the controller working the 24s instructs A1 to hold short of 24L. A2 is approaching the threshold, and being a 321 is 97% going to roll to AA. Meanwhile another arrival, say A3, is now 4 miles out for 24R.

A1 and A2 can both be at AA, however A3 cannot land 24R until A1 crosses 24L. So, timing wise, the departure D2 is cleared for takeoff on 24L when A2 is approaching the threshold for 24R. The reason you see it done like this is because as long as D2 rolls in a timely manner, they will be passing AA around the same time as A2 is approaching AA, and the controller working can cross A1 and A2, so that the runway is clear for A3.

I hope that gives some basic explanation as to why you see this a lot of the time at LAX, there are a multitude of other reasons for why our timing results in a “race” as it were between aircraft on the parallels.

Also writing that out made me realize just how much information my brain is processing when I’m working position.

atcdan wrote:

Source: I am a controller at LAX.

We don’t have to apply SSDO, the runway centerlines are all far enough apart to not need it.

To the OP’s question, we are not waiting for the arrival to land or be short final before we depart an aircraft off the parallel. We are waiting for appropriate IFR separation for for the departing aircraft, as well as runway separation for both the departing and arriving aircraft. To give some insight into a small small slice of the reason you seem to see the planes “racing” with one touching down as the other is passing 80kts on departure roll, I’ll give you the following common scenario.

Plane D1 departs, 24L, on a northbound SID, plane A1 arrives as D1 is already at the beach, and plane D2 is “lining up and wait”. Plane D2 is on a southbound SID, and has to fit into the flow of traffic off of 25R. The controller working the 25’s tells the controller working the 24’s which plane D2 is going to follow. Meanwhile plane A2, say an A321, is on a one mile final to 24R and plane A1 is exiting AA. To avoid being “late” with their southbound D2 aircraft, the controller working the 24s instructs A1 to hold short of 24L. A2 is approaching the threshold, and being a 321 is 97% going to roll to AA. Meanwhile another arrival, say A3, is now 4 miles out for 24R.

A1 and A2 can both be at AA, however A3 cannot land 24R until A1 crosses 24L. So, timing wise, the departure D2 is cleared for takeoff on 24L when A2 is approaching the threshold for 24R. The reason you see it done like this is because as long as D2 rolls in a timely manner, they will be passing AA around the same time as A2 is approaching AA, and the controller working can cross A1 and A2, so that the runway is clear for A3.

I hope that gives some basic explanation as to why you see this a lot of the time at LAX, there are a multitude of other reasons for why our timing results in a “race” as it were between aircraft on the parallels.

Also writing that out made me realize just how much information my brain is processing when I’m working position.

Great explanation! Thank you!

Your comment about what your brain is doing is on point. I once tried to explain descent profile management at busy airports to a non-pilot and it became very complicated very fast.

atcdan wrote:

Also writing that out made me realize just how much information my brain is processing when I’m working position.

Yes, excellent and the "multitude of other reasons" is oh so very correct. I also have written out some lengthy ATC things over the years and had the exact same thought about how much we process when on position. Well done.

Thank you VERY MUCH atcdan. It really makes me appreciate the job you guys do even more.