U

This glossary of historic aviation terms is reproduced from 'The Spotters Glossary' which appeared in 'The Aeroplane Spotter' from January 1940 onwards. 'The Aeroplane Spotter' was the first journal devoted exclusively to the study and practice of aircraft recognition.

We are pleased to have been able to reproduce the entire glossary from A-Z, offering a unique insight into aviation terminology (and therefore aviation history and technology) prior to and during the 1940s.

NB: In the interests of clarity we have substituted current equivalents where words and phrases used in the original publication have fallen from general use (eg, 'aero motor' has been replaced by 'aero engine').

---

Undercarriage: The main alighting gear of an aeroplane or floatplane. Modern undercarriages are usually retractable to reduce drag.

Under Way: A nautical term adapted to aviation to indicate that an aircraft is gathering or losing momentum immediately before or after flight.

Unstick: The separation of a seaplane from the water at the end of its take-off run. Sometimes applied to the take-off of a landplane.

Useful Load: The total weight of the crew, fuel, oil and payload of an aeroplane. A preferable term is "disposable load".