AM From Mexico, joined Oct 1999, 594 posts, RR: 2 Posted (12 years 11 months 5 days 6 hours ago) and read 4547 times:
I have noticed by listening to my scanner that in busy airports with multiple departure runways the runway assignment doesn't come until at a relatively late departure stage concerning takeoff planning.
The best example I can think of is Chicago O'Hare, this would be one real scenario: ATIS reports "departing runways 04L, 09L, 14L, 32L, 32L at T10". That's 5 different takeoff options. When listening to clearance delivery, a departure procedure is assigned, followed by a flight route and/or "as filed", the initial altitude, flight level to expect, and squawk, but NO runway assignment yet. Then it's ramp control for pushback clearance. No runway assignment. Ground metering to report "ready to taxi". No word on what runway yet. It's not until ground control when a runway is assigned, many times resulting in "Request 32L (longer runway), we're pretty heavy today"...
Why are departure runways not assigned earlier, for example with clearance delivery? Doesn't this require a little bit of unnecessary guessing by the crew? How about performance issues? If you're assuming ATC will assign a certain runway and in the end it turns out it's something else, is it fast and easy to reload FMS takeoff runway data and performance or do these new calculations take an extra while?
Airline pilots replies are really appreciated, but of course all replies are more than welcome.
"... for there you have been and there you will long to return."
Modesto2 From United States of America, joined Jul 2000, 2866 posts, RR: 5
Reply 1, posted (12 years 11 months 5 days 5 hours ago) and read 4523 times:
While these late runway assignments may apply to ORD, they do not apply to all major airports. I am most familiar with SFO and LAX...so I will speak about those. LAX mainly uses 24L and 25R for departures. Northbound flights generally use 24L while many eastbound flights use 25R. At SFO, southbound flights generally use 1L while eastbound aircraft use 1R. Heavier aircraft use 28L/R for departures, regardless of destination. These are just examples of when runway assignments can be fairly accurately guessed. I think part of the issue with late assignments is traffic flow. Traffic jams come and go and an aircraft may taxi 20-30 minutes after receiving a clearance. A lot can happen during this time period. Late assignments give the controllers more freedom to conveniently assign departure runways.
Bjones From United States of America, joined Feb 2002, 123 posts, RR: 0
Reply 5, posted (12 years 11 months 5 days 2 hours ago) and read 4490 times:
Although the runway isn't given until taxi clearance is requested pilots usuallly have a pretty good idea which runway they will get based on where they are parked and where they are going after departure. In most cases it doesn't take more than a few keystrokes to input the takeoff runway/departure routing into the FMS. As far as performance data it doesn't take long to calculate because there usually is either quick reference charts or the FMS in some aircraft will calculate it.
America West From , joined Dec 1969, posts, RR:
Reply 6, posted (12 years 10 months 4 weeks 6 hours ago) and read 4327 times:
The runways at CMH are usually assigned based on where the airline's gates are located.
Continental Express (A)
Air Canada (A)
America West (South B)
America West Express (South B)
Northwest (South B)
Northwest Airlink (South B)
US Airways (A)
US Airways Express (A)
American (East B)
American Eagle (East B)
America West Express (North B)
United (North B)
United Express (North B)
Delta Express (C)
Delta Connection-Comair (C)
Delta Connection-ACA (C)
American (East B)
American Eagle (East B)
LAXspotter From India, joined Jan 2007, 3650 posts, RR: 4
Reply 7, posted (7 years 10 months 1 week 5 days 2 hours ago) and read 4059 times:
Quoting Modesto2 (Reply 1): , they do not apply to all major airports. I am most familiar with SFO and LAX...so I will speak about those. LAX mainly uses 24L and 25R for departures
Although this is true, one will realize that it has to do with relieving airport congestion. Many runway assignments are to ease the clogging of aircraft at one side of the airport. Many times, at LAX during specially during Rush hour, aircraft will come from Terminal Four, Five and Six and taxi to 24L, the reason is that the South Field of LAX usually has more aircraft, and the north field has lesser number of aircraft. So, you will see many American and Delta aircraft including American Eagle taxi to 24L. LAX, is definetely one of the best free-flowing airports in the world, we're blessed with good weather four parallel runways mean, they can launch departure after departure. I have never witnessed a lineup at LAX, with more than six aircraft, and this at the 4th busiest airport in the world by movements.
Quoting America West (Reply 6): The runways at CMH are usually assigned based on where the airline's gates are located.
usually how it works at most airports, but at larger airports aircraft will taxi to runways farther away than the closest one to prevent long queues for takeoff.
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