AIM 5-3-3

The following reports should be made to ATC or FSS facilities without a specific ATC request: At all times. When vacating any previously assigned altitude or flight level for a newly assigned altitude or flight level.

When an altitude change will be made if operating on a clearance specifying VFR-on-top.

When unable to climb/descend at a rate of a least 500 feet per minute.

When approach has been missed. (Request clearance for specific action; i.e., to alternative airport, another approach, etc.)

Change in the average true airspeed (at cruising altitude) when it varies by 5 percent or 10 knots (whichever is greater) from that filed in the flight plan.

The time and altitude or flight level upon reaching a holding fix or point to which cleared.

When leaving any assigned holding fix or point. NOTE-

The reports in subparagraphs (f) and (g) may be omitted by pilots of aircraft involved in instrument training at military terminal area facilities when radar service is being provided.

Any loss, in controlled airspace, of VOR, TACAN, ADF, low frequency navigation receiver capability, GPS anomalies while using installed IFR-certified GPS/GNSS receivers, complete or partial loss of ILS receiver capability or impairment of air/ground communications capability. Reports should include aircraft identification, equipment affected, degree to which the capability to operate under IFR in the ATC system is impaired, and the nature and extent of assistance desired from ATC. NOTE-

Other equipment installed in an aircraft may effectively impair safety and/or the ability to operate under IFR. If such equipment (e.g., airborne weather radar) malfunctions and in the pilot's judgment either safety or IFR capabilities are affected, reports should be made as above.

When reporting GPS anomalies, include the location and altitude of the anomaly. Be specific when describing the location and include duration of the anomaly if necessary.

Any information relating to the safety of flight.

When not in radar contact. When leaving final approach fix inbound on final approach (nonprecision approach) or when leaving the outer marker or fix used in lieu of the outer marker inbound on final approach (precision approach).

A corrected estimate at anytime it becomes apparent that an estimate as previously submitted is in error in excess of 2 minutes. For flights in the North Atlantic (NAT), a revised estimate is required if the error is 3 minutes or more.

Pilots encountering weather conditions which have not been forecast, or hazardous conditions which have been forecast, are expected to forward a report of such weather to ATC. REFERENCE-

AIM, Para 7-1-18 , Pilot Weather Reports (PIREPs).

14 CFR Section 91.183(B) and (C).