Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
No Stopping On Bridges  
User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Posted (7 years 10 months 3 weeks 2 days 22 hours ago) and read 3434 times:

Lots of major airports out there have taxiway bridges over roads.... many of them, I've noticed, have "DO NOT STOP ON BRIDGE" signs (or something similiar). Why is this?

30 replies: All unread, showing first 25:
 
User currently offlineVTBDflyer From Thailand, joined Aug 2006, 378 posts, RR: 0
Reply 1, posted (7 years 10 months 3 weeks 2 days 21 hours ago) and read 3410 times:

Heavy loading on the bridge. I suspect that even though the bridge is very thick, the aircraft putting all that weight on anywhere from 3 points - 5/6 points of contact will put high stress on a relatively small area.

VTBDflyer



Fly Thai
User currently offlineLimaFoxTango From Antigua and Barbuda, joined Jun 2004, 784 posts, RR: 1
Reply 2, posted (7 years 10 months 3 weeks 2 days 21 hours ago) and read 3407 times:

I remember watching the United 777 DVD from justplanes.com and the captain said the reason they aren't allowed to stop on brigdes isnt due to weight, but if they had to do an emergency evacuation, the slides would deploy right over the sides of the bridge. Not a pretty sight to say the least.


You are said to be a good pilot when your take-off's equal your landings.
User currently offlineBobster2 From , joined Dec 1969, posts, RR:
Reply 3, posted (7 years 10 months 3 weeks 2 days 20 hours ago) and read 3394 times:

Taxiway bridges are supposed to be at least as wide as the taxiway. There should be enough room for slides.

I think loading could be an issue. Stopping and starting puts more stress on the roadway, it would shorten the lifetime.

Also, if emergency vehicles need to cross the bridge, a stopped plane might block them.


User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 4, posted (7 years 10 months 3 weeks 2 days 20 hours ago) and read 3386 times:
AIRLINERS.NET CREW
DATABASE EDITOR




Quoting Flyf15 (Thread starter):
many of them, I've noticed, have "DO NOT STOP ON BRIDGE" signs (or something similiar). Why is this?

It's a result of rubbernecking A.netters not paying attention to the road, and causing traffic accidents as a result.  Wink



2H4





Intentionally Left Blank
User currently offlineMir From United States of America, joined Jan 2004, 21564 posts, RR: 55
Reply 5, posted (7 years 10 months 3 weeks 2 days 19 hours ago) and read 3362 times:

Quoting LimaFoxTango (Reply 2):
I remember watching the United 777 DVD from justplanes.com and the captain said the reason they aren't allowed to stop on brigdes isnt due to weight, but if they had to do an emergency evacuation, the slides would deploy right over the sides of the bridge.

This is what I remember as well.

Quoting Bobster2 (Reply 3):
Taxiway bridges are supposed to be at least as wide as the taxiway. There should be enough room for slides.

IIRC, on the larger planes, the slides deploy far enough out that it would be a problem.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineEssentialpowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 6, posted (7 years 10 months 3 weeks 2 days 5 hours ago) and read 3167 times:

Quoting VTBDflyer (Reply 1):
Heavy loading on the bridge. I suspect that even though the bridge is very thick, the aircraft putting all that weight on anywhere from 3 points - 5/6 points of contact will put high stress on a relatively small area.

baloney.

The problem is lack of emergency vehicle access if an a/c stops, as well as congestion to the rest of the airport by blocking a throughfare.


User currently offlineLemurs From United States of America, joined Mar 2005, 1439 posts, RR: 4
Reply 7, posted (7 years 10 months 3 weeks 2 days 5 hours ago) and read 3162 times:

Quoting Bobster2 (Reply 3):
Taxiway bridges are supposed to be at least as wide as the taxiway. There should be enough room for slides.

Taxiways are designed for taxing though, not for evacuating people. When you want to evacuate, you expect people to run off into the grass as far away from the airplane as they can manage. You also want emergency vehicles to be able to get to the airplane from directions other than directly in front and behind. Bridges are just bottlenecks for emergencies at the end of the day...if weight were really an issue, the airplane shouldn't be allowed to roll over top of it to begin with!



There are 10 kinds of people in the world; those who understand binary, and those that don't.
User currently offlineVTBDflyer From Thailand, joined Aug 2006, 378 posts, RR: 0
Reply 8, posted (7 years 10 months 3 weeks 2 days 2 hours ago) and read 3066 times:

Quoting Essentialpowr (Reply 6):
baloney.

The problem is lack of emergency vehicle access if an a/c stops, as well as congestion to the rest of the airport by blocking a throughfare.

Just throwing my idea out there.

VTBDflyer



Fly Thai
User currently offlineKaddyuk From Wallis and Futuna, joined Nov 2001, 4126 posts, RR: 26
Reply 9, posted (7 years 10 months 3 weeks 1 day 23 hours ago) and read 3016 times:

Quoting VTBDflyer (Reply 1):
Heavy loading on the bridge. I suspect that even though the bridge is very thick, the aircraft putting all that weight on anywhere from 3 points - 5/6 points of contact will put high stress on a relatively small area.

On that basis, the bridge wouldnt be able to take the loading of an aircraft at all...

Quoting Essentialpowr (Reply 6):
The problem is lack of emergency vehicle access if an a/c stops, as well as congestion to the rest of the airport by blocking a throughfare

This was my understanding of the situation...



Whoever said "laughter is the best medicine" never had Gonorrhea
User currently offlineRichardPrice From , joined Dec 1969, posts, RR:
Reply 10, posted (7 years 10 months 3 weeks 1 day 15 hours ago) and read 2937 times:

Quoting Kaddyuk (Reply 9):
On that basis, the bridge wouldnt be able to take the loading of an aircraft at all...

While its unlikely a bridge that is likely to see large amounts of traffic would be built in such a way, its possible for a structure to take less static weight than dynamic weight and thus would be fine for an aircraft crossing but not to hold its weight for an extended period.

But it is unlikely that such a design would have been approved...


User currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 11, posted (7 years 10 months 3 weeks 1 day 10 hours ago) and read 2879 times:

Stress loads on the Bridge for a longer duration.
regds
MEL



Think of the brighter side!
User currently offlineBobster2 From , joined Dec 1969, posts, RR:
Reply 12, posted (7 years 10 months 3 weeks 1 day 7 hours ago) and read 2840 times:

Quoting HAWK21M (Reply 11):
Stress loads on the Bridge for a longer duration.

I assume this is a maintenance cost issue. The bridge needs periodic repairs, and perhaps the interval can be extended by avoiding unnecessary stress. It's not a safety issue because the bridge is rated to carry the weight, but near the load limits there will be an increasing in cracking and other problems.


User currently offlineUS AIRWAYS From United States of America, joined May 1999, 432 posts, RR: 4
Reply 13, posted (7 years 10 months 3 weeks 1 day 5 hours ago) and read 2795 times:

I'm pretty sure in PHX I've actually stopped on the taxiway bridges the are over the departures road near Terminal 4. The bridge is rather wide though so that may be why.


Go Eagles!
User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 14, posted (7 years 10 months 3 weeks 1 day 1 hour ago) and read 2731 times:

Theres been some fantastic amounts of BS spoken on this topic !!! quite entertaining !

User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 15, posted (7 years 10 months 3 weeks 1 day 1 hour ago) and read 2714 times:

There is some nonsense written in this thead. It's got nothing to do with static vs. dynamic loads.

User currently offlineRichardPrice From , joined Dec 1969, posts, RR:
Reply 16, posted (7 years 10 months 3 weeks 1 day ago) and read 2684 times:

Quoting 777236ER (Reply 15):
There is some nonsense written in this thead. It's got nothing to do with static vs. dynamic loads.

I agree, which is why I said its unlikely such a specific design would have been approved with such a limitation, but static verses dynamic loads is far from nonesense in any materials discussion and is likely to play a part in any bridge design.


User currently offlineLredlefsen From United States of America, joined Apr 2006, 151 posts, RR: 0
Reply 17, posted (7 years 10 months 3 weeks 19 hours ago) and read 2613 times:

Quoting RichardPrice (Reply 10):
its possible for a structure to take less static weight than dynamic weight

Funny, I've always thought gravity pulls *down*, no matter how fast you're going (ignoring aerodynamic effects, which shouldn't matter on a taxiway -- if they do, you've got other problems).

If the pilot nailed the brakes while they're directly on the bridge, I guess the load would have a horizontal component to it...


User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 18, posted (7 years 10 months 3 weeks 18 hours ago) and read 2604 times:

Quoting 777236ER (Reply 15):
There is some nonsense written in this thead. It's got nothing to do with static vs. dynamic loads.

I tried "baloney" long ago like a smart button, but we still have people wanting to design airport bridges with unsafe working loads. Good thing they're just on a forum...


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 19, posted (7 years 10 months 3 weeks 18 hours ago) and read 2595 times:

Quoting US AIRWAYS (Reply 13):
I'm pretty sure in PHX I've actually stopped on the taxiway bridges the are over the departures road near Terminal 4. The bridge is rather wide though so that may be why.

I was spotting there this past weekend, and at the 3pm departure push, they had up to 2 A320s sitting on the bridge for a pretty decent time, all of them headed for runway 25R and originating from gates from the north side of the terminals. But, as you can see from my shameless plug, the bridges themselves aren't that very long:


View Large View Medium
Click here for bigger photo!

Photo © Arturo Clamont



User currently offlineRichardPrice From , joined Dec 1969, posts, RR:
Reply 20, posted (7 years 10 months 3 weeks 16 hours ago) and read 2577 times:

Quoting Lredlefsen (Reply 17):
Funny, I've always thought gravity pulls *down*, no matter how fast you're going (ignoring aerodynamic effects, which shouldn't matter on a taxiway -- if they do, you've got other problems).

Theres an element of how much compression a material can take before fracturing, and the less time the weight is on the structure, the less compression takes place.

Its not all instantaneous.


User currently offlineCM767 From Panama, joined Dec 2004, 654 posts, RR: 1
Reply 21, posted (7 years 10 months 3 weeks 8 hours ago) and read 2532 times:

Quoting LimaFoxTango (Reply 2):
if they had to do an emergency evacuation, the slides would deploy right over the sides of the bridge.

This is the real reason.



But The Best Thing God Has Created Is A New Day
User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 22, posted (7 years 10 months 3 weeks 1 hour ago) and read 2447 times:

People:

Bridges constrain emergency operations from an a/c, and impede traffic flow.


User currently offlineDeltamike172 From United States of America, joined Mar 2001, 67 posts, RR: 0
Reply 23, posted (7 years 10 months 2 weeks 6 days 21 hours ago) and read 2414 times:

While I can see how stopping on a bridge would effect an emergency, I can't see why the airport authority would put up a sign telling planes not to stop on thier bridge for this reason. I always figured those signs where in place to decrease the time spent on the bridge, so less stress was put on the bridge, and the airport could go a longer time without replacing the bridge.

While this might not seem valid, consider all the airports that have concrete (can take heavier weight for a longer period of time before it fails verses asphalt) strategically placed in places where aircraft tend to remain motionless for long periods of time (departure ends of taxiways and runways, hold pads, and the gate areas). Very often, the concrete will only be installed at the gate itself, not the taxiway that runs along side. Heck, even the drive through at Wendy's has concrete in the drive through line where cars sit and wait.

DM


User currently offlineBobbidooley From United States of America, joined Jul 2006, 64 posts, RR: 0
Reply 24, posted (7 years 10 months 2 weeks 6 days 21 hours ago) and read 2408 times:

Im MEM there is a bridge that is a part of runway 18/C. I have seen heavy AC land on the bridge. Look at google earth, you will see that the bridge over Winchester Rd, is about 50f from the prime landing zone.

Bobbi



Planes make me happy.
25 EssentialPowr : Negative...Why or who would design a bridge, or approve such a design, that had a working load that wasn't several times greater than the typical loa
26 Post contains images HAWK21M : Under construction time. regds MEL
27 Aer Lingus : just to clear things up a little. metals under a compressive stress will always fail through eventual TENSILE stresses. a steel cloumn in a structure
28 JayinKitsap : Reality check time. I've designed bridge, gantry, and portal crane runways, straddle lift bridges, rail bridges, and highway bridges. All structures r
29 Mohavewolfpup : this is the case with most threads on a.net I find. wait for the next plane crash to come around and the junior a.net armchair investigators go into
30 Post contains images Vio : ... Yeah, I have that video too. That's exactly what he said.
Top Of Page
Forum Index

Reply To This Topic No Stopping On Bridges
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Why No Papi On W/B Rwys At LAX? posted Wed Oct 18 2006 06:58:06 by Adipasqu
Medical Emergency Diversions/ No Doctor On Board posted Sun Oct 30 2005 00:04:24 by Julesmusician
Why No Landings On posted Mon Sep 12 2005 11:29:01 by TheSonntag
Why No V2500 On The A318 posted Sat May 28 2005 13:52:30 by HAWK21M
Why No Winglets On The 777? posted Sun Sep 12 2004 12:19:58 by Regis
Why No HUDs On Large Aircraft? posted Tue Aug 31 2004 05:52:04 by AndrewAir
Why No Paint On Wings? posted Wed May 5 2004 12:55:05 by A380900
Why No FE On 737? posted Sun Apr 25 2004 16:36:12 by Checkerboard
Why No Window On Freighters posted Wed Feb 18 2004 20:00:52 by Thvgjp
Why No Winglets On The 737-600 posted Sun Sep 28 2003 00:41:25 by Cancidas

Sponsor Message:
Printer friendly format