[Scan-DC] Incident or Exercise???

[Albert LaFrance]

In the last approximately 15 minutes (it's 13:30 now) a helo has made four
passes (north-south-north-south), very low, beginning just west of my
location near the Annandale Rd./Arlington Blvd. intersection, with each pass
being further east.  The first pass might have been over the Beltway, while
the last was directly over my house.

I think the tail number is N4120E.  The upper part of the fuselage is white,
with a blue "racing stripe" along the lower portion of the sides and running
vertically up the back.  There are two tanks or pods on the landing skids.

Possibly an aerial land-surveying/mapping operation?  Seemed like it was too
low for that, but I don't have any expertise from which to judge.

Albert