Flight Instructors Training Procedures _revised AIC_x

1. AIM
LESSON 25
DME ARC APPROACHES
The aim of this exercise is to teach the student how to fly an approach that commences with a DME
ARC with sole reference.
DEFINITION
This exercise may be defined as the series of manoeuvres required to transition from the en-route
phase of flight to the applicable approach by following a given DME ARC.
2. WHY THIS LESSON IS BEING TAUGHT
This exercise is taught so that the student will be able to follow a DME ARC from a specified point until
established on the VOR or ILS approach with sole reference to the instruments. There are a large
number of approaches in the USA and Africa based on flying a DME ARC. This transition to final
approach is a lot quicker than following the full procedure from overhead a facility and is particularly
useful in a non-radar environment. There are some approaches based entirely on flying a DME ARC to
MDA, and in the case of a missed approach, a DME arc is followed.
3. WHAT THE INSTRUCTOR IS TO TEACH (Briefing of 1:00hr.)
i. The theory of flying the curved approach using the VOR and DME i.e. a series of tangents to the
depicted circle are flown. The error from a true circle will be less than 0.1nm if the heading is
changed every 10°.
ii. The significance of lead in radials.
iii. How to read and interpret the approach chart.
4. THE AIR EXERCISE
i.
ii.
POSITIONING FOR THE ARC
FOLLOWING THE ARC
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i. The instructor should have the student
proceed to the VOR on e.g. the 182° radial.
At a distance of say 15 DME have the
student turn through 90° to follow the DME
ARC. For this example assume the
procedure requires following the 15 DME
ARC clockwise to intercept the inbound radial
of 282° for a VOR approach.
ii. Allow a little distance to ensure that the
aircraft does not go through the ARC during
the turn e.g. at 100 kts G/S a ½ nm lead
should suffice. The aircraft must be turned
left through about 90° to the inbound track.
i. As the heading of 272° is approached, the
aircraft being still outside of the arc roll out of
the turn early to give an intercept angle of
about 20°. If the aircraft has flown through
the arc continue the turn until an intercept
angle is established. The OBS must now be
set. Determine the required radial for the
approach from the chart e.g. 282°. Use radial
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