If the pilot believes that his radio has failed, what is the proper procedure he will use to inform the controller of the situation?

Code （ ） is the equivalent of a Mayday call on the radio.

The controller can control the aircraft in one-way or two-way radio failure by using light signals. If this is the case, the pilot will look for （ ） for the clearance to land.

If the aircraft in radio failure receives light signals provided by the controller during daytime, he should acknowledge tower transmission or light signals by （ ）.

At night the aircraft in radio failure can acknowledge tower transmission or light signals by （ ） to indicate that the pilot understand the light signals and will comply accordingly.

The （ ） situation is a condition of being threatened by serious and/or immenent danger and of requiring immediate assistance.

The （ ） situation is a condition of being concerned about safety and of requiring timely, but not immediate, assistance.

In a distress situation, use of （ ） commands radio silence on the frequency in use.

One of the ways the pilot can be identified easily on radar when in distress is （ ）.

The ELT, an electronic, battery-operated transmitter, sends forth a distinctive （ ） on 121.5 MHz.

The word "Mayday" spoken at the start of a transmission identifies （ ）.

The word "Panpan" spoken at the start of a transmission identifies （ ）.

The words "Mayday" or "Panpan" should be spoken （ ） at the start of the initial distress or urgency call.

Urgency messages have （ ） over all transmissions except distress messages.

If the ground station called by the aircraft in distress or urgency does not reply, then （ ） shall reply and give whatever assistance possible.