I'd like a number 11, please

November 27, 2009 10:57 AM

Why are the tops of buildings in downtown Los Angeles numbered?

In TV shows that show helicopter-type sweeping shots of downtown LA, you can see that the tops of many buildings have a number inside a red circle, as Google Maps shows here. What is the purpose of these numbers? They're not unique, for example there's several "12" buildings - I'm stumped as to what they might be. Any ideas?

posted by pdb to grab bag (9 comments total)

Rooftop helipads sometimes display a large two-digit number, representing the weight limit (in thousands of pounds) of the pad; in addition, a second number may be present, representing the maximum rotor diameter in feet. [wikipedia]
posted by desjardins at 10:59 AM on November 27, 2009 [2 favorites]

Maybe the number lets pilots what size/weight helicopter that landing pad will support?
posted by sebastienbailard at 10:59 AM on November 27, 2009

Interesting. It looks like tall buildings in LA are required to have helipads. This article has a little more information:

The written component provides basic background facts, informing visitors that L.A.’s downtown has far more helipads than any other city in the country, and that is because zoning laws require every building taller than 75 feet to have an Emergency Helicopter Landing Facility. (Fire truck ladders rarely reach higher than 80 feet.)
posted by av123 at 12:04 PM on November 27, 2009 [2 favorites]

Can you just drop your helicopter down on any building you want and drop people off?
posted by ctmf at 12:14 PM on November 27, 2009

zoning laws require every building taller than 75 feet to have an Emergency Helicopter Landing Facility

Seems like the building just Southeast of the one in the Maps link provides a counter-example of that.
posted by ctmf at 12:17 PM on November 27, 2009

Just found the reference to emergency helicopter landing facilities in the LA municipal code.

To answer the original question of what the number means, if you scroll down to Figure 118-A, it says that "The red numeral indicates the allowable weight, in thousands of pounds, that the facility is capable of supporting."
posted by av123 at 12:25 PM on November 27, 2009 [2 favorites]

Can you just drop your helicopter down on any building you want and drop people off?

Doesn't look like it. From the municipal code:

Emergency Helicopter Landing Facility – A heliport on high-rise buildings or elsewhere for Fire Department emergency use only.

Seems like the building just Southeast of the one in the Maps link provides a counter-example of that.

Which one? Could be that it is less than 75 feet tall, or maybe it was built before July 1, 1974 and is thus exempt from the requirement, if I'm reading the legalese correctly.
posted by av123 at 1:02 PM on November 27, 2009

Seems like the building just Southeast of the one in the Maps link provides a counter-example of that.

i think you may be mis-reading the fountain/stage at one california plaza as a building.

if you mean the buildings a couple of blocks over from where the google map was centered, those will pre-date the requirements.
posted by jimw at 1:35 PM on November 27, 2009

Previously: http://ask.metafilter.com/75827/What-do-the-numbers-on-helipads-mean
posted by FlamingBore at 9:14 PM on November 27, 2009