Jack Screws

Damaged Jack Screws Can Be Detected In Aircraft

How to Detect Damaged Jack Screws In Aircraft

Letter From the Author – Jack Screws

Jack ScrewsOff the coast of California, in January 31, 2000, flight 261 experienced a catastrophic loss of pitch control which was caused by a damaged jack screws threads.  All 88 on board died instantly upon impact.  It was a very sad day.  The news left me in a stunned state. I thought of the last moments prior to impact. The children, the mothers, fathers, grandparents, pilots and crew. All clinging to a miracle. The scene goes beyond imagination. I cried.   God bless them all.

The procedure that follows, at the moment, is the best that I can do to prevent another jack screws failure by giving the pilots Advanced warning of a potential failure.  To the loved ones who suffered such a devastating loss, God bless you all.  All my love and Respect,

Bob Bartol, Jr.




jack screws




The embodiments herein relate generally to failure detection systems and more particularly to a system for detecting damaged jack screws in aircraft.  There are many sources of potential failure on aircraft any of which results in the aircraft failing during flight and crashing.  For example jack screws failure on aircraft may cause a complete loss of control of the aircraft during flight resulting in the death of all crew and passengers.  Physical examination of jack screw threads can only be accomplished after removing large sections of the access panels during ground operations.   At the present time there are no processes available to complete this inspection either on the ground or in flight without making a visual inspection.

The existing method of inspection requires removal of access panels while on the ground and looking for damage to the threads that are covered with grease.  As can be imagined visual inspections may fail because the grease covers threads which may be damaged.  Some inspections may also include feeling the threads with fingertips.  This is a very hit or miss procedure because the high number of threads on a screw make it easy to miss one damaged thread.

There is no method of detecting screw thread damage nor of monitoring the state of a screw on aircraft while in flight at the present time.  All jack screw threads are inspected monitored during preflight and post flight procedures by manual inspection.  As can be seen there is a long felt need for a solution to detect and monitor damage to screw threads on an aircraft without having to visually inspect the threads.

Jack Screws

Off the coast of California, in January 31, 2000, flight 261 experienced a catastrophic loss of pitch control which was caused by a damaged jack screws threads.


In one aspect of the present disclosure a system for detecting damage to screws on an aircraft comprises wiring connected between a drive motor driving a screw on the aircraft and an ammeter with an electronic display wherein the ammeter is configured to display in the current level associated with driving the drive motor of the screw wherein a rise in the current level indicates a drop in resistance and an alarm circuit coupled to the ammeter configured to trigger in response to the current level rising indicating damage to the screw.


The detailed description of some embodiments of the invention is made below with reference to the accompanying figures wherein like numerals represent corresponding parts of the figures. The Figure is a schematic view of a system for detecting damaged equipment on an aircraft according to an exemplary embodiment.


Embodiments disclosed herein generally provide a system for detecting damage to screw threads on aircraft without the need for visual inspection.  Referring now to the Figure a system is shown according to an exemplary embodiment.  A jack screw is shown connected to a drive motor.  It will be understood that for sake of illustration the aircraft is not shown however the jack screw may represent any one of various jack screws used to control movement of aircraft parts.  For example one critical aircraft part to which the jack screw may be coupled to is the horizontal stabilizer.  As may be appreciated should the horizontal stabilizer fail the aircraft cannot maintain longitudinal stability and is likely to crash.  Wiring may be connected to the drive motor which transmits an electric current signal back to an electronic display such as an ammeter with memory storage.  In some embodiments the display is one already on the aircraft and configured to provide current readings of the jack screw or screws as in some embodiments multiple screws may be monitored. In other embodiments the display may be dedicated to monitoring the health of the  crew.  By reading signal currents of a screw and detecting changes in the current level one may determine if a change on resistance has occurred.

In an exemplary embodiment when an undamaged screw is installed or determined to be without damage a current reading is taken and a baseline current level is established indicating the undamaged state of threads.  Damage to a screw may decrease the resistance in the circuit which causes an increase in the current level.  As shown current spikes may be displayed indicating the screw being monitored is damaged.  If a damaged thread occurs the motor current will spike up then return back tothe† baseline level.  If several threads are damaged a series of current spikes may be observed.  In some†embodiments a sub circuit maybe coupled to the system so that detected current spikes trigger an alarm such as an audible signal  beep horn etc. or a video signal flashing light text warning etc  nDuring flight these observations may be seen during actual flight conditions on the display providing the advantage of detecting a problem in flight.  The pilot and crew  may gain valuable time to prepare for andconduct an emergency landing prior to the loss of†the aircraft.  In flight readings may be stored and forwarded to the flight recorder for future analysis.

Embodiments disclosed may also be used for pre flight and post flight procedures.   Aspects of the system improve the accuracy of inspections and make inspections far quicker and efficient since there is no need to remove panels in some instances.  In a pre flight procedure for detecting damaged threads or resistance to screw movement caused by for example greasing or temperature affecting the grease density the pilot or mechanic may operate the jackscrew up and down from stop to stop while observing the drive motor current on a horizontal display.  If resistance occurs current will increase.  The pilot already knows whichjack screw to manually inspect and likely replace as it has already been hooked up to the detection system.  In the alternative if the current remains normal the screw is known to be undamaged without needing to open up the panel.Persons of ordinary skill in the art may appreciate that numerous design configurations may be possible to enjoy the functional benefits of the inventive systems.  Thus given the wide variety of configurations and arrangements of embodiments of the present invention the scope of the invention is reflected by the breadth of the claims below rather than narrowed by the embodiments described above


system for detecting damage to screws on an aircraft comprising wiring connected between a drive motor driving a screw on the aircraft and an ammeter with an electronic display wherein the ammeter is configured to displaychanges in the current level associated with driving the drive motor of the screw wherein a rise in the current level indicates a drop in resistance andan alarm circuit coupled to the ammeter configured to trigger in response to the current level rising indicating damage to the screw.



A system is disclosed which automatically detects damage to jack screws on an aircraft without The system measures the current of an undamaged jack screw and monitors the current level pre flight in flight  and post flight for changes in resistance  When resistance lowers the current level rises indicating damage to the screw  Detecting and monitoring may occur without having to remove panels and manually inspect the jack screw  An electronic display may show readings and store the readings which may be forwarded to the flight recorder for record keeping and analysis  In some embodiments detected damage to the screw may trigger an alarm warning the pilot to land before the part fail.


The above procedure is being provided as a public service and not as engineering advice or guidance. The author does not warrant that the procedure is accurate, complete, or will resolve any particular mechanical or electrical condition with an aircraft or other machine.  The author does not warrant that the procedure, if utilized, does not infringe any patent rights of any third-party. The author expressly disclaims any warranties of fitness for a particular purpose or merchantability.  This procedure is being provided”As is” and any person using the procedure utilizes it at their own risk.  By using this procedure, the user and any legal entity employing the user agrees to indemnify and hold the author harmless against any loss or damage (including reasonable attorneys fees) out of any action or dispute arising out of the user or legal entities use of this procedure.  The general public is granted a license to duplicate this procedure and incorporate it into maintenance procedures and other manuals on the condition of agreement with the foregoing terms of use.  If you do not agree with these terms, do not use this procedure or create a derivative work involving this procedure.


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About the Author
Bob Bartol has spent his whole life working with electronics in almost every capacity and spent many hours in Physics classes. He currently holds 4 U.S. patents and has been making a living off one of the patents "The Bartol Mag-Probe" for over twenty years. Bartol Research's Mag-Probe now has a global reach and is dramatically reducing trouble shooting downtime anywhere a solenoid valve. relay, or contactor is used. F111 Air Force Projects - European Flight Competition January 1968 Bob attended electronics school in the Air Force. Upon graduation he was assigned to a fighter wing in Germany. During his assignment he prepared seven aircraft for European competition. The fighter wings aircraft won the competition. Bob then returned to the United States and taught advanced radar for two years. Two years later, he returned to Europe. During this assignment, Air Force headquarters Europe selected Bob to open a Precision Measuring Equipment Laboratory (P.M.E.L) in England. It was the first of its kind in the Air Force. Upon his return to the United States, Air Force headquarters assigned Bob to Air Force research command in Florida. This was strictly a scientific assignment for research and development. After three years he moved from Eglin AFB in Florida to Edwards Air Force Base in California where he had direct contact with the National Bureau of Standards and supported research and development aircraft. During this assignment, he designed a modification for the TF X fighter (F-111). This modification made possible an additional 9800 flying hours per year. The F111 was the first swing wing aircraft in history. General Dynamics completed the modification prior to acceptance by the U.S. Air Force. Modification of F111 Aircraft General Dynamics March 1968 As a result of increasing this flying time Bob Received an award from Edwards Air Force Base for Increasing flying time of the F111 by 9,800 hours per year. The Award was Presented by Colonel Grumbles to TSGT Bob Bartol on June 17, 1968

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