Flight Procedures
Instrument Flight
Chord Method
(Normally used for arcs of
C.
greater than 12 DME) To
020
0295
maintain an arc using the
RANGE
COURSE
chord method, fly a series of
5
short, straight legs
connected by small turns
that take you slightly inside
5
and outside the actual arc
C.
CRS
HDG
(Figure 23). To use the
chord method; first, ensure
Correct 5-10 degrees for each
29 nm arc
that the station is tuned and
1/2 mile deviation from arc
identified. Then determine
B.
direction of turn and
020
0305
RANGE
COURSE
calculate lead point. Initiate
10
10
the turn at the lead point
(when DME equals radius of
arc, plus or minus the LPC)
using a 1/2 SRT. Roll out
B.
from your interception turn
CRS
HDG
Desired
when the bearing pointer is 5
30 nm arc
to 10 degrees ahead of the
A.
A.
wingtip position at the
0300
020
RANGE
COURSE
correct DME. Maintain your
Vary the amount of
correction according
heading until the bearing
to the rate of deviation
pointer has moved to 5 to
and adjust as
10 degrees behind the
necessary according
31 nm arc
wingtip and then turn until
to the rate of
correction
the bearing pointer is once
CRS
HDG
again positioned 5 to 10
degrees ahead of the
wingtip. Repeat this
procedure as long as you
Figure 23: MAINTAINING AN ARC (CHORD METHOD)
are flying on the arc. The
length of the legs will
decrease as you fly arcs closer to a station until you reach a point where this method loses its advantage
over the angle of bank method described below.
If a crosswind makes holding your DME difficult, you may need to increase or decrease the number of
degrees you place the bearing pointer ahead of the wingtip or the number of degrees that you allow it to
move behind the wingtip position to avoid having to make heading changes too frequently to maintain the
arc.
Angle of Bank Method
To maintain an arc using the angle of bank method, first ensure the station is tuned and identified. Next,
determine direction to turn and lead point. At the lead point, turn and position the bearing pointer on the
wingtip and keep it there by holding the aircraft in a shallow turn. The closer you are to a station, the
greater your bank angle will be. The angle of bank method is normally used inside of 12 DME. Outside of
12 DME, the bank angle required to maintain an arc will probably be too small to hold accurately.
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