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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