Tue, Jul 11, 2006
You May Be Asking... "What's A DF?"
Ever heard of DF -- or
direction finder -- steer? Like the non-directional beacon, it's a
technology that goes largely unused by today's pilots... but it was
once a valuable asset, that flight service stations could use to
get wayward pilots back on course.
Compared to modern RNAV and GPS equipment, a DF steer is very
low-tech -- all a pilot needs is a communications radio. An FSS
asks the pilot to key the mike for 10 to 15 seconds, then announce
the N number. The DF equipment homes in on the transmission, and
provides a bearing to the aircraft's radio.
One station can pinpoint the pilot's position by having the
aircraft make turns and assessing the bearing change. If two DF
stations are in range, the bearings can be plotted on a chart.
Today, only 54 direction finders remain in service in the lower
48-states... and the FAA says those DF's have been used sparingly
over the last nine years. The agency claims the equipment is beyond
its useful lifecycle... and that improved radar coverage, pilot
education, and technologies such as area navigation (RNAV) and
global positioning satellite (GPS) have reduced the utilization of
DF steers -- essentially making DFs obsolete.
But are the Dfs as obsolete as the FAA claims? The Aircraft
Owners and Pilots Association asked the FAA to allow members to
comment before decommissioning the service... and the FAA agreed,
setting a July 28 deadline for comments.
Addresses for your comments -- including ways to submit your
comments via email -- are provided at the FMI link below.
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