Data sheet modifier
These units are equipped with jet-powered devices or other technology, wings, or even powerful long legs that allow them to make long jumps across the battlefield. The resultant speed and mobility usually makes for good assault troops.
Data sheet effects of Jump Packs
Where a base unit already has the Jump Packs ability
Where your unit is a base unit that already has the Jump Packs ability:
Simply use the Speed value stated in the unit’s data sheet — we’ve already integrated the effect of Jump Packs. 
Where the Jump Packs ability is additional
Where your unit is not a base unit, and has the Jump Packs ability, apply these changes relative to its base unit:
The Eldar Swooping Hawks unit is an Aspect Warriors base unit with added Jump Packs ability.
The base unit has a Speed value of
15/30 cm, whilst the Swooping Hawks unit has
30/45 cminstead — that is,
(15 x 2)/(15 x 3) cm.
Game effects of Jump Packs
Where your unit has the Jump Packs ability:
When you move the unit, you may ignore terrain — though you must still take a Dangerous Terrain test for the unit whenever a move starts in dangerous terrain, and whenever a move ends in dangerous terrain. You still may not place the unit on impassable terrain. 
When you make a charge move with the unit, you can move it over enemy units that are already in base contact with your other units.