What is the primary function of the ELT type C located under No1 jumpseat?

The primary function of the ELT (Emergency Locator Transmitter) type C located under No1 jumpseat is to emit distress signals in emergencies. This device is crucial in aviation safety, as it is designed to transmit a distress signal that can help search and rescue operations locate the aircraft promptly in the event of an emergency situation, such as a crash or forced landing. The ELT continuously transmits a signal on a specified frequency that can be detected by search-and-rescue satellites and other aircraft, aiding in the quick identification of the aircraft's location.

The other options don't align with the purpose of the ELT. A seatbelt extension's function is to provide additional length to seatbelts for passengers, while additional lighting refers to improving visibility within the cabin or emergency exit areas. Storing emergency medical supplies pertains to keeping first aid kits or medical equipment accessible, which is separate from the signaling function of an ELT. This distinction highlights the essential role the ELT plays in emergency preparedness and response in aviation.