Weather Criteria -Cont.

CHAPTER FOUR

INSTRUMENT FLIGHT RULES WORKBOOK

If VFR flight conditions cannot be met, an IFR flight plan must be filed. This is not the only

time an IFR flight plan may be filed. In fact, to decrease the probability of midair collisions,

OPNAVINST 3710.7 states that instrument flight rules shall be used to the maximum extent

practicable. As with VFR, the filing of an IFR flight plan will be based on the actual weather at

the point of departure (at the time of clearance), the forecast weather enroute and the forecast

weather at both the destination and alternate (if required) during the period one hour before until

one hour after the estimated time of arrival.

Takeoff minimums for an IFR flight depend on the type of instrument rating held by the pilot-in-

command.

Takeoff minimums

Special instrument rating. No takeoff ceiling or visibility minimums apply. Takeoff

shall depend on the judgment of the pilot and urgency of the flight.

Standard instrument rating. Published minimums for the available nonprecision

approach, but not less than 300 foot ceiling and 1-statute-mile visibility. When a

precision approach compatible with installed and operable aircraft equipment is

available, with published minimums less than 300-1, takeoff is authorized provided

the weather is at least equal to the precision approach minimums for the landing

runway in use, but in no case when the weather is less than 200 foot ceiling and one-

half statute mile visibility/2400 foot runway visual range (RVR).

Alternate airfield and weather requirements are based on three conditions: (1) the destination

weather forecast, (2) whether you are flying a single-piloted or a multi-piloted aircraft, and (3)

the communications equipment on board the aircraft (i.e., one or two transceivers). Destination

and alternate weather requirements are tied to the weather minimums of the available

approaches. All instrument approach procedures and their weather minimums are listed in the

LOW ALTITUDE INSTRUMENT APPROACH PROCEDURES, Volumes 1 through 15.

Radar (PAR and ASR) approaches are listed in the front of each volume for the area covered (see

examples below Figures 4-2 and 4-3). The minimums for an approach are expressed in a ceiling

and visibility and are found in parentheses (5001 is read as 500 feet ceiling and 1 statute mile

visibility).

4-4 INSTRUMENT FLIGHT RULES