Why do parallel runways land on the outside and not the inside?
Posted by ShutupBird69@reddit | aviation | View on Reddit | 25 comments
Why do airports land arrivals on the outermost runway and use the inner runway (closest to the terminal) for departures?
It seems backwards because it forces landed planes to stop and cross an active takeoff runway just to get to the gates.
From a pilot or ATC standpoint, what’s the main driver here?
Skreticus@reddit
PHL would like a word. Under typical conditions it takes arrivals on 27R (closer to terminals), while departing from 27L (farther away). I suspect - as someone else referenced - that this is for noise mitigation over residential areas, but cannot confirm.
swakid8@reddit
Most folks answered your question. But there are airports that have ran departures on the outer runway. Denver, PHL are two examples.
antonio16309@reddit
Landing on 35L when your gate is on the east side of the A or B concourse is awesome, almost like flying right up to the gate. Same for 16L and Concourse C but happens less often.
gregarious119@reddit
I was thinking of PHL on the 27s as well...land 27R, hang a right into the ramp.
mattincalif@reddit
I’ve been curious about this too- glad you brought it up!
BassetCock@reddit
PHL is one airport that I can think of that uses the inner for landing when they’re landing and departing to the west.
DarthSontin@reddit
Yeah, always right runway for landing and left for departure. The nice part is that the runways are staggered so you don't have to cross 9L/27R taxiing out to 27L.
archMildFoe@reddit
Not sure why you got downvoted, you are correct.
ManQu69@reddit
I think MAN does landing on the inside and takeoff on the outside
crazy-voyager@reddit
On 23, on 05 it flips.
RandalPMcMurphyIV@reddit
I have not flown into airports with parallel runways very much but I have always assumed that departures will use the longer of the two for balanced field length. For non aviators, balanced field length, is the length that it takes for the aircraft to reach take off speed and then make an emergency stop within the remaining runway. In almost all cases, the amount of runway needed for arrivals to land is less than the balanced field length required for departures.
athlalus@reddit
Denver is the opposite, the inboards are the arrival runways.
DBond2062@reddit
Outside runways also mean that those long conga lines of aircraft on parallel approaches are farther apart. Much less important for departing aircraft that are going to disperse rapidly towards their destinations.
Raccoon_Ratatouille@reddit
Because once the arrival is on the ground they really don’t matter. The crew won’t time out, the plane won’t runout of gas, so why should they get priority over the departures more likely to get stuck? Also, airlines love single engine taxiing to save fuel. That means they taxi slower. And with crossing clearances being hard to anticipate they’d either need to start their engine super early to get across the runway or be a touch late and be super slow taxiing across a runway, which now means that plane that’s already arriving without much fuel is going around and now you might have an emergency on your hands.
dumbassretail@reddit
Either departures have to cross the arrival runway, or arrivals have to cross the departure runway.
The second is easier, because you can more precisely control departures. They don’t roll until you say “cleared for takeoff”. A departure can line up, and then wait 20 seconds for an arrival to clear the runway, with minimal impact to anyone.
But if you have departures cross the arrival runway, and you need a 3 mile arrival gap to get a departure across the arrival runway but you only have 2.5 miles, there’s not much you can do. The entire gap is wasted, and the departure has to wait.
holl0918@reddit
It's easier to tell a plane on the ground to stand still and wait a moment than it is to tell one in the air to do the same.
_brake_flake@reddit
It’s easier to tell a plane on the ground to stop rather than a plane in the air
penguinise@reddit
Safety, convenience, efficiency, take your pick.
It's much safer to clear across a departing runway because you never clear traffic in front of an active takeoff clearance. In contrast, landing clearance is given significantly in advance of touchdown, and it is common to have multiple aircraft cleared to land on the same runway at the same time, while also clearing traffic to cross that runway. (Look no further than the recent LGA incident for an example of this being dangerous.)
The controllers have significantly more control over the timing of departing traffic than arriving traffic, for hopefully obvious reasons.
And finally, it's common to line up the arrivals on parallel taxiways and do a mass crossing during a gap in the departures.
TripleDallas123@reddit
It's much safer to cross a takeoff runway where they are stopped and can safely wait for crossing traffic instead of trying to cross in front of a plane traveling 150mph on final
sharkbite217@reddit
It’s easier to manage spacing for crossing with planes going 0 knots than it is to manage spacing on planes going 120-150knots
Straight_Weight_1073@reddit
More separation between aircraft arriving.
adjust_your_set@reddit
That and if an aircraft has to go around, then can escape away from regular departing traffic instead of crossing it.
Disastrous-Wall-6943@reddit
Some airports, LAX for sure, also use this as part of a noise mitigation plan because landing is usually quieter than takeoff.
ANITIX87@reddit
It's easier to expedite or hold a departure to get an arrival across then to tell someone to slow down or speed up on short final to get a departure across.
Hwang-Blake383@reddit
it is mostly about traffic flow and where the terminals are located. the terminals are usually in the middle, so departing from the inside means a way shorter taxi. if you land on the outside, you have plenty of time to roll out, slow down, and hold short before crossing the inside runway to get to the gate.