Jackscrew

However, most screw jacks have large amounts of friction which increase the input force necessary, so the actual mechanical advantage is often only 30% to 50% of this figure.

A fine pitch thread, which would increase the advantage of the screw, also reduces the speed of which the jack can operate.

This was encouraged in 1858 when jacks by the Tangye company to Bramah's hydraulic press concept were applied to the successful launching of Brunel's SS Great Eastern, after two failed attempts by other means.

The large area of sliding contact between the screw threads means jackscrews have high friction and low efficiency as power transmission linkages, around 30%–50%.

The failure of a jackscrew on a Yakovlev Yak-42 airliner due to design flaws resulted in the crash of Aeroflot Flight 8641 in 1982.

The failure of a jackscrew on a McDonnell Douglas MD-80 due to deficient maintenance brought down Alaska Airlines Flight 261 in 2000.

A MRAP armoured vehicle being transported aboard National Airlines Flight 102 in 2013, a Boeing 747-400BCF freighter, broke loose immediately after takeoff and smashed through the rear bulkhead.

Both flight recorders were knocked offline, hydraulic lines were severed and most critically, the horizontal stabilizer actuator’s jackscrew was destroyed, rendering the aircraft uncontrollable.

[3] The term jackscrew is also used for the captive screws that draw the two parts of some electrical connectors together and hold them mated.