c..Mixed- A mixture of clear ice and rime ice.
Intensity of icing:
a.
Trace- Ice becomes perceptible. Rate of accumulation is slightly greater than the rate of sublimation. Deicing/anti‐icing equipment is not utilized unless encountered for an extended period of time (over 1 hour).

b..
Light- The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti‐icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti‐icing equipment is used.

c..
Moderate- The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti‐icing equipment or flight diversion is necessary.

d..
Severe- The rate of accumulation is such that deicing/anti‐icing equipment fails to reduce or control the hazard. Immediate flight diversion is necessary.

IDENT-A request for a pilot to activate the aircraft transponder identification feature. This will help the controller to confirm an aircraft identity or to identify an aircraft.
(Refer to AIM.)
IDENT FEATURE- The special feature in the Air Traffic Control Radar Beacon System (ATCRBS) equipment. It is used to immediately distinguish one displayed beacon target from other beacon targets.
(See IDENT.)
IF-
(See INTERMEDIATE FIX.)
IFIM-
(See INTERNATIONAL FLIGHT INFORMATION MANUAL.)
IF NO TRANSMISSION RECEIVED FOR (TIME)-Used by ATC in radar approaches to prefix procedures which should be followed by the pilot in event of lost communications.
(See LOST COMMUNICATIONS.)
IFR-
(See INSTRUMENT FLIGHT RULES.)
IFR AIRCRAFT- An aircraft conducting flight in accordance with instrument flight rules.
IFR CONDITIONS- Weather conditions below the minimum for flight under visual flight rules.
(See INSTRUMENT METEOROLOGICAL
CONDITIONS.)

IFR DEPARTURE PROCEDURE-
(See IFR TAKEOFF MINIMUMS AND
DEPARTURE PROCEDURES.)
(Refer to AIM.)

IFR FLIGHT-
(See IFR AIRCRAFT.)
IFR LANDING MINIMUMS-
(See LANDING MINIMUMS.)
IFR MILITARY TRAINING ROUTES (IR)- Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low‐altitude navigation and tactical training in both IFR and VFR weather conditions below 10,000 feet MSL at airspeeds in excess of 250 knots IAS.
IFR TAKEOFF MINIMUMS AND DEPARTURE PROCEDURES- Title 14 Code of Federal Regulations Part 91, prescribes standard takeoff rules for certain civil users. At some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums, departure proce-dures, or both to assist pilots in avoiding obstacles during climb to the minimum en route altitude. Those airports are listed in FAA/DOD Instrument Approach Procedures (IAPs) Charts under a section entitled “IFR Takeoff Minimums and Departure Procedures.” The FAA/DOD IAP chart legend illustrates the symbol used to alert the pilot to nonstandard takeoff minimums and departure procedures. When depart-ing IFR from such airports or from any airports where there are no departure procedures, DPs, or ATC facilities available, pilots should advise ATC of any departure limitations. Controllers may query a pilot to determine acceptable departure directions, turns, or headings after takeoff. Pilots should be familiar with the departure procedures and must assure that their aircraft can meet or exceed any specified climb gradients.