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Why The Reverse Take-offs At LAS?  
User currently offlineSevenheavy From United Kingdom, joined Mar 2004, 1156 posts, RR: 9
Posted (5 years 2 months 3 weeks 2 days ago) and read 5983 times:

I have been watching a few LAS departures from my hotel balcony over the last few days. Predominantly the runways in use have been the 25/19's.

Every so often, a random aircraft / airline will taxi to the opposite end, wait for a considerable period of time and take off from either one of the 07's or 1's. All the while the majority of movements are in the other direction

There is no particular airline or aircraft involved. I have seen G4 MD80's, DL(NW) A319's, VS B744, and a few others.

I can understand that some aircraft may find it beneficial to get a straight out departure in the direction they are heading, but without exception they have waited so long for a gap in the flow that it can't possibly be viable.

Any ideas?

Thanks


So long 701, it was nice knowing you.
18 replies: All unread, jump to last
 
User currently offlinePmk From United States of America, joined May 1999, 664 posts, RR: 2
Reply 1, posted (5 years 2 months 3 weeks 2 days ago) and read 5985 times:

The wind direction changed.

PMK


User currently offlineSANAV8R From United States of America, joined Mar 2009, 215 posts, RR: 0
Reply 2, posted (5 years 2 months 3 weeks 2 days ago) and read 5919 times:

I notice it too every once and a while here at UNLV. I recall last week one mid-morning and saw a few WN, DL, Janets, private planes.

User currently offlineKL911 From Czech Republic, joined Jul 2003, 5300 posts, RR: 15
Reply 3, posted (5 years 2 months 3 weeks 2 days ago) and read 5902 times:

With full loads, and changing winds, they want to make sure they can take off against the wind I guess.

User currently offlineSevenheavy From United Kingdom, joined Mar 2004, 1156 posts, RR: 9
Reply 4, posted (5 years 2 months 3 weeks 1 day 23 hours ago) and read 5818 times:



Quoting Pmk (Reply 1):
The wind direction changed.



Quoting KL911 (Reply 3):
With full loads, and changing winds, they want to make sure they can take off against the wind I guess.

Possibly, but these are random flights. Many others, before and after, depart in the "normal" direction. Why just the odd one, every hour or two?

With the possible exception of the VS B744, none would have been particularly heavy flights where changes in wind direction would have been that critical, particularly given the length of 25R/07L

In most situations, it would have been quicker for them to have cut their losses and gone back to re-join the 'normal" flow at the other end of the airfield.

Thanks



So long 701, it was nice knowing you.
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 5, posted (5 years 2 months 3 weeks 1 day 23 hours ago) and read 5761 times:

Quoting Sevenheavy (Thread starter):

Any ideas?

Sure. The occasional against-the-flow departure (usually off 07L) is needed due to the higher takeoff weight it provides compared with taking off 25R. Why? It's something called "runway slope" and the effects it can have on takeoff performance.

You'll probably be very surprised to know that the ends of 07L and 25R differ in elevation above sea level by 146 feet! (2,179-2,033). What that means in simple terms is that takeoffs on 25R are going uphill, and takeoffs on 07L are going downhill. The downhill slope of 07L offers better takeoff weights than does the uphill slope on 25R, and although most aircraft can live with the weights off 25R, some absolutely require the use of 07L, particularly long-haul flights, and/or ones that are carrying more fuel than usual due to enroute weather, or bad weather at the destination.

As long as the surface winds are not an issue, the main issue with 07L takeoffs is taking a 30-45 minute delay so that ATC can build a gap in the arrival stream in which to cut the departure loose.

The amount runway slope at LAS on 07L/25R is about 1% down/up, respectively, and it's the most of any *major* US airport. Most Boeings have a limitation of +/- 2.0%, so at 1%, LAS isn't all that big deal for most flights. Performance-wise, it's worse in the hot summer months...

In a more radical example of the concept, check out the 18% runway slope at this airport in France:


View Large View Medium
Click here for bigger photo!

Photo © Fabrice Sanchez - Brussels Aviation Photography



Obviously, at this one, one doesn't takeoff uphill, nor land downhill...  Wink

[Edited 2009-09-28 18:51:31]

User currently offlineDc10srule From Canada, joined Oct 2006, 172 posts, RR: 0
Reply 6, posted (5 years 2 months 3 weeks 1 day 22 hours ago) and read 5628 times:

Hello All,

At YYZ, we closed rwy 05/23 to grind down a large hump on the runway that caused a very similar affect to the one described at LAS by OPNLguy. When departing on Rwy 23, the hump would show up about 6000 feet down and caused some issues. Incidentally, on runway 15L/33R at YYZ, 2 B747s parked at opposite thresholds cannot see each other due to the "hill" between them.

Take Care!



Giggity-Giggity..!
User currently offlineGlbltrvlr From United States of America, joined Oct 2007, 770 posts, RR: 0
Reply 7, posted (5 years 2 months 3 weeks 1 day 21 hours ago) and read 5536 times:



Quoting OPNLguy (Reply 5):
In a more radical example of the concept, check out the 18% runway slope at this airport in France

Or for a slightly less radical historical example: http://www.ascho.wpafb.af.mil/BUILDINGS/runway.HTM


User currently offlineSevenheavy From United Kingdom, joined Mar 2004, 1156 posts, RR: 9
Reply 8, posted (5 years 2 months 3 weeks 1 day 21 hours ago) and read 5393 times:



Quoting OPNLguy (Reply 5):
Sure. The occasional against-the-flow departure (usually off 07L) is needed due to the higher takeoff weight it provides compared with taking off 25R. Why? It's something called "runway slope" and the effects it can have on takeoff performance

Wow - I had no idea - thanks.

I'm amazed that the slope is that big a factor on such a long runway, but it has been unseasonably warm here in LAS the last couple of days - easily over 100. Its like July all over again!

Thanks again



So long 701, it was nice knowing you.
User currently offlineCrownvic From United States of America, joined Oct 2004, 1954 posts, RR: 5
Reply 9, posted (5 years 2 months 3 weeks 1 day 20 hours ago) and read 5332 times:

It should also be noted, the problem use to be far more prevalent in prior years when performance of a/c came more into play. When NW use to run their nonstops to NRT with 742 eqpt., it was quite common for them to do a downwind t/o on 7L. The same held for Monarch and Airtours DC-10's, American Int'l 741's and other charter a/c that were loaded down.

It should also be noted that not only does the runway slope come into play, but engine out "drift down" along with terrain are important factors too. The 7L departure has much less terrain issues than the 25 departures do where 12,000 foot mountains prevail.


User currently offlineBeakerLTN From United Kingdom, joined Jul 2009, 297 posts, RR: 0
Reply 10, posted (5 years 2 months 3 weeks 1 day 12 hours ago) and read 5026 times:

I thought these things were normally down to noise regulations? if one direction requires flying over houses etc, then you must be able to maintaint a certain rate of climb, and if you're a bit heavy you can't. So you have to wait your turn at the other end of the runway.

This happened to me a couple of weekends back in Naples (Italy) Pilot said we weer too heavy for a 26 departure and had to wait for a rwy 5*. Stood there for ever waiting for an entirely clear approach so we could go. Have to admit I was suprised we had to do this in an A319 - I thought those baby's were pretty powerful.

*those numbers are probably wrong



300/319/320/321/330/732/733/734/73G/738/744/772/77W/146/EMB135/EMB145
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 11, posted (5 years 2 months 3 weeks 1 day 11 hours ago) and read 4956 times:



Quoting BeakerLTN (Reply 10):
I thought these things were normally down to noise regulations? if one direction requires flying over houses etc, then you must be able to maintaint a certain rate of climb, and if you're a bit heavy you can't. So you have to wait your turn at the other end of the runway.

They sometimes can be (LAX after hours, as an example), but it's impossible to generalize or automatically attribute things to noise abatement at any/every airport. Quite simply, there are too many operational variables involved to so.

Quoting Crownvic (Reply 9):
It should also be noted that not only does the runway slope come into play, but engine out "drift down" along with terrain are important factors too. The 7L departure has much less terrain issues than the 25 departures do where 12,000 foot mountains prevail.

"Driftdown" is an enroute consideration, and I think what you're looking for here is terrain as an obstacle, and the performance considerations (with a potential engine out) for the various climbout segments after takeoff. A good example of this is at SXM, where taking off towards the ocean gives great weights, but going the other way (towards the rising terrain) gives much lower weights and requires turns to avoid that obstacle/terrain.

One of my favorite airports is TVL, where the approach to runway 18 takes you over Lake Tahoe, and you depart on 36 due to all the rising terrain south of the airport. IIRC, the missed approach point for 18 is something like 4-5 miles from the end of the runway, while one is still over the lake. There are other "one way in, one way out" airports, but Tahoe is my personal favorite.


User currently offlineMcCarranMGR From , joined Dec 1969, posts, RR:
Reply 12, posted (5 years 2 months 3 weeks 1 day 10 hours ago) and read 4828 times:



Quoting BeakerLTN (Reply 10):
I thought these things were normally down to noise regulations? if one direction requires flying over houses etc, then you must be able to maintaint a certain rate of climb, and if you're a bit heavy you can't. So you have to wait your turn at the other end of the runway.

Currently the only Noise Abatement Procedures are for runways 19R/L, as these are not available for jet departures that weigh more than 75,000 pounds between the hours of 2000-0800. Also runway 1L shall only be used for departures if the weather/winds dictate a straight runway 1 departure during non-curfew hours 0800-2000. Also air carrier type aircraft are to depart runway 19L not 19R.


User currently offlineLASoctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1
Reply 13, posted (5 years 2 months 3 weeks 1 day ago) and read 3099 times:

I was just noting the downhill/uphill-ness just today. I went south on Eastern (for non-natives to Vegas, on the east side of the field) and looked west and noticed that the runway was surely going uphill. But, just slightly. Then I stopped by at the Viewing Park. Then I went north on LV Blvd. and looked to the east, it was running downhill. It was pretty interesting..

Quoting Sevenheavy (Reply 8):
but it has been unseasonably warm here in LAS the last couple of days - easily over 100. Its like July all over again!

There's a wind advisory in effect until 2100 tonight. After today, it will be relatively cooler outside. Cooler as in mid-low 80s..



[NOT IN SERVICE] {WEStJet}
User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 14, posted (5 years 2 months 3 weeks 22 hours ago) and read 2974 times:

It's likely due to second segment climb weight restrictions. The aircraft you mentioned using the other runways likely don't meet the second segment climb requirments at their weight and elect to use another runway with a lower second segment climb requirment. They may sit for a long period of time to burn off fuel to meet the maximum for the departure. They may also be sitting for a weather hold.

User currently offlineFlightopsguy From United States of America, joined Jan 2005, 348 posts, RR: 0
Reply 15, posted (5 years 2 months 3 weeks 22 hours ago) and read 2932 times:



Quoting JETPILOT (Reply 14):
It's likely due to second segment climb weight restrictions.

Max allowable takeoff gross weight takes in several factors, including runway length, slope, obstacles at the end of the runway, second segment engine out climb, tire speed, and procedure turns, just to name a few. Many airports have better weights even with a couple knots of tailwind in a particular direction, hence the opposite direction takeoff. The old DEN airport (Stapleton) was notorious for this, and often the old lead-sled -9's and 727's required a tailwind takeoff against the arrival flow. Runway 13-31 at LGA is known for this (good luck, OPNLguy!), with 31 having better weights. An opposite direction takeoff delay at LGA can easily run 30-45 mins. or more.



A300-330 BAC111/146/J31/41 B99/1900 CV580 B707-777 DC8/9/10 L188/1011 FH227/28/100 SB340 DO228 EMB2/170 CR2-900 SH330-60
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 16, posted (5 years 2 months 3 weeks 22 hours ago) and read 2891 times:



Quoting JETPILOT (Reply 14):
It's likely due to second segment climb weight restrictions.

Any way you want to slice it, for the purposes of the OP's original question, it was because 07L provided more weight than 25R did...

Quoting Flightopsguy (Reply 15):
Runway 13-31 at LGA is known for this (good luck, OPNLguy!)

Thanks, I need all I can get...  Wink


User currently offlineHAMAD From United Arab Emirates, joined Apr 2000, 1161 posts, RR: 7
Reply 17, posted (5 years 2 months 3 weeks 16 hours ago) and read 2729 times:

it happens... i recall in the year 2000 i was at gravely point. every single carrier was taking off from runway 01, until a northwest dc-9 took off from the opposite direction (is it runway 18 or 19)? following its departure, the other arrivals/departures kept on using runway 1


PHX - i miss spotting
User currently offline727forever From United States of America, joined Jan 2006, 794 posts, RR: 5
Reply 18, posted (5 years 2 months 3 weeks 6 hours ago) and read 2548 times:



Quoting HAMAD (Reply 17):
it happens... i recall in the year 2000 i was at gravely point. every single carrier was taking off from runway 01, until a northwest dc-9 took off from the opposite direction (is it runway 18 or 19)? following its departure, the other arrivals/departures kept on using runway 1

This is common at LGA as well. Most times NW DC-9s have to takeoff rwy 22 because of the climb gradient on 13 over the stadiums.

OPNLguy is dead right on LAS. Additionally, JETPILOT is correct with regard to climb gradient. Those hills off the end of the 25's are rather large and close in, however the SID has turns designed to avoid them so the most correct answer should be the slope. Having flown full 767-300s out of there in the summer, I can tell you it certainly was tight going off 25R. We usually had to go full power or close to it to lift the weight.

727forever



727forever
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