Gravitic anomaliser

The Gravitic anomaliser was a component of The Doctor's TARDIS that generated a localised field of artificial gravity around the outside of the TARDIS.

The Fourth Doctor used the anomaliser to help a Skonnan ship escape the gravity field of a nascent black hole. (DW:The Horns of Nimon)

The gravitic anomaliser was more commonly used to allow the TARDIS to land on a planet with a low centre of gravity.

The Tenth Doctor mentioned the Gravitic anomaliser to Martha in DW: Smith and Jones.