Buzz From United States of America, joined Nov 1999, 697 posts, RR: 29 Reply 2, posted (5 years 10 months 2 days 13 hours ago) and read 2914 times:
Hi KETA, Buzz here. Those are "rain gutters" to channel rivulets of rain away from the cabin doors as the rain rolls down from the top of the fuselage.
It seemed that the DC-10's "rain gutters" didn't work as well as the Boeing 727 / 737... at least in "sunny" Portland Oregon (it tends to rain here). I'd joke that the DC-10 was designed in southern California... sunny warm weather.
g'nite
Zkpilot From New Zealand, joined Mar 2006, 4521 posts, RR: 12 Reply 3, posted (5 years 10 months 2 days 13 hours ago) and read 2908 times:
They are there to stop rain dripping onto passengers or onto the floor of the aircraft when the door is open for boarding/deboarding.
They are aligned so as to be as little drag penalty as possible... since most aircraft fly with a slight nose up attitude, the rails are angled downwards at the front so inflight they are almost level.
GrandTheftAero From United States of America, joined Nov 2003, 254 posts, RR: 6 Reply 5, posted (5 years 10 months 2 days 1 hour ago) and read 2723 times:
Quoting Zkpilot (Reply 3): since most aircraft fly with a slight nose up attitude, the rails are angled downwards at the front so inflight they are almost level.
I believe they are angled to be tangent with the circulation about the wing since the gutters aft of the wing are angled in the opposite direction.