Piston assembly for aircraft door

A piston assembly for an aircraft, comprising:

• a piston housing;
• a piston housing fluid port formed in the piston housing for supplying fluid to and removing fluid from the piston housing;
• a piston shaft disposed within the piston housing, wherein the piston shaft is configured for translation in either forward or aft directions when fluid is respectively supplied to or removed from the piston housing;
• a screw shaft disposed within the piston housing, wherein the screw shaft includes a first gear that rotates without translation in either the forward or aft directions while the piston shaft translates in either the forward or aft directions;
• and
• a slider disposed within the piston housing, wherein the slider includes a second gear, and wherein the slider is configured for translation in either the forward or aft directions without rotation,
• wherein:
• the slider moves between a first position where the first gear and the second gear are separated from one another to allow the piston shaft to translate in the forward direction or the aft direction and a second position where the second gear surrounds the first gear so that the first and second gears are engaged with one another and the piston shaft is prevented from translating in the forward or aft directions.