31 and 51 are filled with a suitable hydraulic fluid as power is applied by the catapult and aircraft engines tensile force is applied along the longitudinal axis of the device by bar 71 which transmits this force to housing 7 plunger shaft 33 is held stationary by the attachment to the deck at 34 fluid in chamber 21 is thus pressurized as tensile force on bar 71 increases fluid in chamber 21 compresses permitting plunger 17 to approach displacement chamber 31 as this movement takes place fluid is displaced from chamber 31 and flows through bores 35 and 37 to force headed piston 43 against operating plunger 65 when fluid in chamber 21 reaches its preselected compression state about 5 by volume operating plunger 65 is forced sufficiently toward bar 71 by displaced fluid that head 67 releases nubs 63b and the aircraft begins its takeoff plunger 17 travel is approximately one centimeter 0 4 in in one actual test of this invention calibrated for a 70 000 lb thrust at release the face 19a of plunger 17 was about 45 square centimeters 7 square inches and chamber 21 was about 25 4 centimeters 10 inches in length at release pressure in chamber 21 was about 69 pascals 10 000 lbs sq in at the moment of release a shock recoil reaction occurs which can be destructive if not countered.