If communications are lost while inside a Class B, C, or other towered airspace, try to assist the air traffic controller, by trying to do what you are expected to. If climbing or descending to an altitude, continue climbing or descending to that altitude. If transitioning through an airspace, continue on your route.
If you have not yet entered the airspace, simply remain clear. If possible, avoid the towered airport.
If a Class D airspace must be entered, watch and determine the direction and flow of traffic. Broadcast your aircraft type, position, altitude, and intentions to land, in case only the radio's receiver is malfunctioning.
Enter the traffic pattern and look for the control tower to signal you with a light gun. Tower controllers use light guns to communicate to aircraft should two way radio communications be lost.
Light Gun Meanings While Airborne
If you receive a light gun signal, acknowledge your receipt by rocking the airplane's wings and/or flashing the landing and navigation lights.
It is also possible that you maybe able to hear the tower, but the tower is unable to hear you. If you are issued radio instructions, acknowledge by rocking your wings and flashing your lights. Often times, aircraft radios will broadcast silence or static only. In this case, the controller will report, "Calling tower, carrier only, no voice".
After landing, the tower will use light gun signals to guide your movement on the airport surface. On the ground, the light gun signals are as follows:
Light Gun Meanings on the Ground
Troubleshooting
Many times problems with the radio can be a minor problem with the radio setup. The radio might be selected to transmit on the number two radio, while receiving on the number one radio. The radio might be silenced or the volume turned low. The headset or microphone may have become unplugged. Checking these few simple things often solves radio problems.
However, if the radio's circuit breaker is tripped, a possible electrical malfunction inside the radio, or possibly with a portion of the airplane's electrical system, is indicated.
As always, do not allow yourself to become distracted from flying or navigating the airplane by the problem you are troubleshooting.
VHF/DF
The airport/facilities directory contains a list of FAA facilities that provide VHF direction finding assistance to pilots. VHF/DF equipment consists of a directional antenna and a VHF radio receiver. When the aircraft being searched for transmits on the VHF communications radio, the FAA's VHF/DF system displays the direction from which the broadcast is originating. The facility then knows a line of bearing from the DF equipment where the lost airplane must be.
The meaning of the light gun signals is defined legally in ยง 91.125 ATC light signals.