and low-visibility approach and landing operations. Systems of concern include Terrain Awareness Warning Systems (TAWS), Enhanced Ground Proximity Warning Systems (EGPWS), and Traffic Collision Avoidance Systems (TCAS), to name a few. Pilots of radio altimeter equipped aircraft should become familiar with the radio altimeter"s interdependence with the other aircraft systems and expected failure modes and indications that may be associated with harmful interference. b. Actions. Recognizing interference/anomalies in the radio altimeter can be difficult, as it may present as inoperative or erroneous data. Pilots need to monitor their automation, as well as their radio altimeters for discrepancies, and be prepared to take action. Pilots encountering radio altimeter interference/anomalies should transition to procedures that do not require the radio altimeter, and inform Air Traffic Control (ATC). c. Inflight Reporting. Pilots should report any radio altimeter anomaly to ATC as soon as practical. d. Post Flight Reporting. 1. Pilots are encouraged to submit detailed reports of radio altimeter interference/anomalies post flight as soon as practical, by internet via the Radio Altimeter Anomaly Reporting Form at https://www.faa.gov/air_traffic/nas/RADALT_reports/. 2. The post flight pilot reports of radio altimeter anomalies should contain as much of the following information as applicable: (a) Date and time the anomaly was observed; (b) Location of the aircraft at the time the anomaly started and ended (e.g., latitude, longitude or bearing/distance from a reference point or navigational aid); (c) Magnetic heading; (d) Altitude (MSL/AGL); (e) Aircraft Type (make/model); (f) Flight Number or Aircraft Registration Number; (g) Meteorological conditions; (h) Type of radio altimeter in use (e.g., make/model/software series or version), if known; (i) Event overview; (j) Consequences/operational impact (e.g., impacted equipment, actions taken to mitigate the disruption and/or remedy provided by ATC, required post flight pilot and maintenance actions). 7-6-3. VFR in Congested Areas A high percentage of near midair collisions occur below 8,000 feet AGL and within 30 miles of an airport. When operating VFR in these highly congested areas, whether you intend to land at an airport within the area or are just flying through, it is recommended that extra vigilance be maintained and that you monitor an appropriate control frequency. Normally the appropriate frequency is an approach control frequency. By such monitoring action you can "get the picture" of the traffic in your area. When the approach controller has radar, radar traffic advisories may be given to VFR pilots upon request. REFERENCE- AIM, Para 4-1-15, Radar Traffic Information Service. 7-6-4. Obstructions To Flight a. General. Many structures exist that could significantly affect the safety of your flight when operating below 500 feet AGL, and particularly below 200 feet AGL. While 14 CFR Part 91.119 allows flight below 500 AGL when over sparsely populated areas or open water, such operations are very dangerous. At and below 7-6-2 Potential Flight Hazards