Monday, August 3, 2015

Have Rapid-Blink LEDs Replaced Incandescent Bulbs as Aircraft Warning Navigation Lights Atop the Washington Monument?

UPDATED 10:24 p.m. May 16, 2020 with additional content: See below.

The top of the Washington Monument with two of its four pairs of red-flashing aircraft warning navigation lights during a total lunar eclipse on February 21, 2008.


This needs to be noted ...

It APPEARS that something I've been long anticipating -- the switch-over from the "regular" incandescent bulbs (lamps?) that comprise the four pairs of slower blinking navigation warning red lights atop the Washington Monument -- one pair on each of the cardinal directional-facing sides of this most world famous of obelisks -- to the rapid-blink LEDs has finally occurred.

The nearly full "Snow Moon" appears balanced atop the Washington Monument, 1:21AM February 1, 2015.


I noticed it late last night (12:36AM EDT to be exact on Aug. 2nd) on the north-facing pair, which is the pair that I typically see from where I live when on 15th or 16th Streets NW in the Dupont and Logan Circle neighborhoods. It continued tonight in the same way.

Aerial view of the Washington Monument, the White House, and downtown Washington, D.C. (date uncertain).


If in fact this is what has happened, then it marks the biggest change in the aircraft warning navigation lights atop the Monument -- always problematic given its location is totally restricted airspace and the fact the whole thing is brightly illuminated -- since February 1995. It was then -- as noted in this Washington City Paper article 9 months later in December 1995 -- that a synchronizing switch was installed that made all four pairs of lights blink in unison.

Prior to that, each had a partial wink that was out of phase with all the others (and was much more soothing).

No, I can't find a link to it, I just remember it because I had a hard copy for a long time. Found it (see above link).

I don't know when those lights were installed, but I have seen pictures of the Washington Monument from the 1940s when clearly they weren't there.

UPDATED 10:24 p.m. 5/16/2020:

So, it turns out that the four pairs of red warning navigation lights on the Monument's pyramidion head were installed in 1958. As context, in March 1931, there was an effort to put a navigation light in one of each of the four pairs of observation deck windows but that wasn't effective. Instead, a series of floodlight batteries were installed and illuminated on Armistice Day 1931. See the timeline in this 2004 report (pages B-52 and B-55).

End of Update.

The Hughes Memorial Tower -- which I've written about on this blog over the years, most recently here -- had its nighttime red-winking navigation lights switched from incandescent (and a wonderful "up the rocket" pattern on that star tower-shaped structure) to LEDs in or about January 2008.

The Hughes Memorial Tower (a.k.a., the "Eiffel Tower") and its much smaller companion tower as seen from the 5800 block of Colorado Avenue NW, Washington, D.C., 1:57PM July 5, 2015.


Like virtually all the tall transmission towers in the D.C. area (indeed, the Baltimore/Washington region), the Hughes Memorial Tower during the day has a strobe light mode.

Most of the other major transmission towers -- e.g., channels 4, 7, and 9 and the WWDC (DC 101) tower -- all appear to have the older incandescent-style aircraft warning navigation lights (and daytime strobe modes). In the case of the channel 20 / 26 tower at 5202 River Road in Bethesda, Md., it has only a strobe mode at all hours.

The transmission tower located at 5202 River Road in Bethesda, Md., 3:26PM July 3, 2014 as seen from the adjacent Capital Crescent Trail.


I had heard from someone that the FAA had not approved LEDs for nighttime aircraft warning navigation warning use, but that appears not to be the case. Indeed, the very first fast-blink LED lights I saw where atop the skyscrapers in Midtown Manhattan (New York City) about 12 years ago. I asked my friend Brian's partner Greg why the "frequency" of the flashing speed had been changed, and he explained to me that it wasn't that but rather the introduction of the LED technology.

LED "bulbs" do not have a filament that needs to heat up and cool down.

To be clear, it is possible that the Washington Monument navigation lights had already been switched to a CFL-type of lamp, but I don't think so because there have been instances when one of the pair of lights has clearly blown out (is out for a few days). (I suppose it's possible that the new lights are actually CFLs, but I suspect they are LEDs.)

I was thinking of writing to the Capital Weather Gang -- in particular, Jason Samenow -- to mention this topic (not that they would likely care, especially coming from me).

The Washington Monument as seen during the day from the corner of 15th Street and Independence Avenue SW, Washington, D.C., 2:29PM May 28, 2015.


OK, that's all for now.

I was going to post a day about my mostly crappy Sunday -- despite the long walk I took back from Bethesda via the Capital Crescent Trail to Georgetown and to Dupont -- that ended on a somewhat better note (as I watched Star Trek Into Darkness at the Floriana downstairs bar), but I'll save that for another entry, perhaps my next planned one (tomorrow night).

I'm going to sleep now. G'night.


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