Aeronautical Information Manual (AIM), page 183

Index   182 -- Page 183 -- 184


reasonable, though intermittent basis. Once the alert
is issued, it is solely the pilot's prerogative to
determine what course of action, if any, to take. This
procedure is intended for use in time critical
situations where aircraft safety is in question.
Noncritical situations should be handled via the
normal traffic alert procedures.

a. Terrain or Obstruction Alert

1. Controllers will immediately issue an alert to
the pilot of an aircraft under their control when they
recognize that the aircraft is at an altitude which, in
their judgment, may be in an unsafe proximity to
terrain/obstructions. The primary method of detect-
ing unsafe proximity is through Mode C automatic
altitude reports.
Low altitude alert Cessna Three Four Juliet, check your
altitude immediately. And if the aircraft is not yet on
approach, the MVA (MEA/MIA/MOCA) in your area is six
2. Terminal Automated Radar Terminal System

(ARTS) IIIA, Common ARTS (to include ARTS IIIE

and ARTS IIE) (CARTS), Micro En Route
Automated Radar Tracking System (MEARTS), and
Standard Terminal Automation Replacement System
(STARS) facilities have an automated function
which, if operating, alerts controllers when a tracked
Mode C equipped aircraft under their control is below
or is predicted to be below a predetermined minimum
safe altitude. This function, called Minimum Safe
Altitude Warning (MSAW), is designed solely as a
controller aid in detecting potentially unsafe aircraft
proximity to terrain/obstructions. The ARTS IIIA,
CARTS, MEARTS, and STARS facility will, when

MSAW is operating, provide MSAW monitoring for
all aircraft with an operating Mode C altitude
encoding transponder that are tracked by the system

and are:

(a) Operating on an IFR flight plan; or

(b) Operating VFR and have requested
MSAW monitoring.

3. Terminal AN/TPX-42A (number beacon

decoder system) facilities have an automated
function called Low Altitude Alert System (LAAS).
Although not as sophisticated as MSAW, LAAS
alerts the controller when a Mode C transponder

equipped aircraft operating on an IFR flight plan is
below a predetermined minimum safe altitude.
Pilots operating VFR may request MSAW or LAAS
monitoring if their aircraft are equipped with Mode C
Apache Three Three Papa request MSAW/LAAS.

b. Aircraft Conflict Alert.
1. Controllers will immediately issue an alert to
the pilot of an aircraft under their control if they are
aware of another aircraft which is not under their
control, at an altitude which, in the controller's
judgment, places both aircraft in unsafe proximity to
each other. With the alert, when feasible, the
controller will offer the pilot the position of the traffic
if time permits and an alternate course(s) of action.
Any alternate course(s) of action the controller may
final recommend to the pilot will be predicated only on
other traffic being worked by the controller.
American Three, traffic alert, (position of traffic, if time
permits), advise you turn right/left heading (degrees)

and/or climb/descend to (altitude) immediately.

4-1-17. Radar Assistance to VFR Aircraft
a. Radar equipped FAA ATC facilities provide
radar assistance and navigation service (vectors) to
VFR aircraft provided the aircraft can communicate
with the facility, are within radar coverage, and can be
radar identified.

b. Pilots should clearly understand that authoriza-
tion to proceed in accordance with such radar
navigational assistance does not constitute authoriza-
tion for the pilot to violate CFRs. In effect, assistance

provided is on the basis that navigational guidance
information issued is advisory in nature and the job of
flying the aircraft safely, remains with the pilot.

c. In many cases, controllers will be unable to
determine if flight into instrument conditions will
result from their instructions. To avoid possible
hazards resulting from being vectored into IFR
conditions, pilots should keep controllers advised of
the weather conditions in which they are operating

and along the course ahead.

d. Radar navigation assistance (vectors) may be
initiated by the controller when one of the following
conditions exist:

Services Available to Pilots 4-1-11

Page 183 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   182 -- Page 183 -- 184