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AIM

10/12/17

4

−1−11

Services Available to Pilots

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.

EXAMPLE

Low altitude alert Cessna Three Four Juliet, check your
altitude immediately. And if the aircraft is not yet on final
approach, the MVA (MEA/MIA/MOCA) in your area is six
thousand.

2.

Most En Route and Terminal radar 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 radar 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.

NOTE

Pilots operating VFR may request MSAW or LAAS
monitoring if their aircraft are equipped with Mode C
transponders.

EXAMPLE

Apache Three Three Papa request MSAW/LAAS.

4.

Due to the lack of terrain and obstacle

clearance data, accurate automation databases may
not be available for providing MSAW information to
aircraft overflying Mexico and Canada. Air traffic
facilities along the United States/Mexico/Canada
borders may have MSAW computer processing
inhibited where accurate terrain data is not available.

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
recommend to the pilot will be predicated only on
other traffic being worked by the controller.

EXAMPLE

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:

2/28/19

AIM