# Glossary

The words flight operations run on, each defined in two sentences, with how RALPH handles it and the terms related to it.

## Aircraft and flying time

- [Hobbs meter](/resources/glossary/hobbs-meter): the clock hours an aircraft runs.
- [Tacho](/resources/glossary/tacho): engine hours, counted in proportion to RPM.
- [Tech log](/resources/glossary/tech-log): the aircraft's own record of every flight.

## People and training

- [Pilot authorisation](/resources/glossary/pilot-authorisation): who may fly which aircraft.
- [DTO](/resources/glossary/dto): a Declared Training Organisation.
- [ATO](/resources/glossary/ato): an Approved Training Organisation.