Optical Character Recognition software has been around for a while now and is used in many applications from number plate recognition to document scan to text. The big opportunity comes when incorporated into Surveying and robotics. For this, many companies turn to big Cloud Computing Products such as Google Cloud or Azure but there is a cheaper way if you are prepared to do some computer legwork and are not after a one stop shop solution. If you want one stop then GCP or Azure is the place to go but you will pay for it.

Rescue deleted files or photos - O&O DiskRecovery

Alternatively you can combine smaller products as below to achieve similar great results for efficiency in mass processing. I have remained generic and not to mention brands as either the open source or proprietry products will return good results.

The big hold up has been getting GOOD free opensource/freeware OCR software. We now have it in the form of FreeOCR downloadable from paperfile http://www.paperfile.net.


This software allows you to scan all documents into word format extracting the text automatically and works with pictures too. It uses the tesseract OCR engine which is at the following GitHub page http://code.google.com/p/tesseract-ocr/ and can be compiled into your own software creation for the aspiring coders amongst us.

Lets say you want to scan CCTV footage for registrations of people coming and going through a gate, Simply turn the video into images (maybe using VLC) and load the saved images into FreeOCR. Hit the OCR button and it will convert any text in the images to a text file.

This might be a good idea for automated scanning of CCTV footage after a crime to find witnesses.

Another alternative use would be for BIM and scanning asset tags or data plates. Lets say you have some georeferenced images taken with something like a SPECTRA SP20 you would be able to cross refer the OCR recovered Model and Serial number with the GeoTag in the images Metadata in an automated way to geolocate the asset data in the database.

You would already have to have an asset database to query but  you could add assets like this too.

Maybe you could automate cheaply using a GoPro Hero5 (or later) set to Linear or Medium Field Of View, 50 Frames Per second and good forward lighting. You would also need a piece of software that uses tesseract and will record the frame or picture number against the OCR output and image metadata including GPS data.I mention this method with a GoPro example as you could use the same video footage as you take for photogrammetric modelling where the results would improve with the better camera and also records the Geolocation. If you need a GoPro, they now supply the Hero7 12MP on Amazon. Click the image below to see the listing and the Specs.

This Photogrammetric modelling would provide the basis for the 3D virtualised world engine for self operated robots later.

Now Moving on from data collection, imagine if robots could read languages and understand, orientate and operate themselves with OCR or feature extraction with 360 cameras, then we are talking that we are close to robots automated operations in changing environments.

Now lets combine other work with driverless cars and the virtualised world engine, we are talking about fully autonomous vehicles or self operated machines in a variable world.

The helps the Future to be Exciting as we change how we apply current technologies to deliver futuristic capabilities today.

Insta360 Air (Micro USB) 360 Camera

Wiring protection techniques

There are many ways in protecting cables from damage which range from correct routing and bunching to adding extra protection to the cables insulation or outer sheath. We need to discuss a few as you will have to recognise what is to be used when and how. We shall begin with looming which is bundling of a group of wires to route them through the Aircraft or vehicle in an organised fashion. The looming of aircraft wires should always be done carefully and in accordance with the Aircraft Wiring Manual. Failure to comply with this fundamental rule can have fatal consequences. for instance, if a fuel tank sensor wire was loomed with the main generator output cables and after time the loom were to chafe and expose a couple of wires on the main generator output cable and maybe just one wire strand on the fuel tank sensor wire, then there is the possibility that a high electrical charge may be passed down the sensor wire, creating a big spark inside of the fuel tank with the possibility that it might ignite the fuel vapour inside the tank and thus i need not say how catastrophic this could be. ALWAYS PERFORM IN ACCORDANCE WITH THE MANUAL SO THAT THESE THINGS DON’T HAPPEN, IF THEY DO HAPPEN, THE AUTHORITIES WILL CHECK TO SEE IF YOU PERFORMED THE JOB CORRECTLY. REMEMBER YOU ARE AN ENGINEER SO BE PROFESSIONAL. Now if you still wish to pursue this career then we shall continue. Wire looms are generally large in size so they are generally tied with a bundle or loom tie and then broken down into groups which are tied with a group tie. These ties used to be tied with lacing cord which in the main is being phased out and replaced with plastic cable ties no different than what you may find inside your computer or behind your car dashboard except they are approved for aircraft work. When using lacing cord or cable ties, it is important that the tie is tight enough to prevent movement down the loom but not so tight that it bites into the insulation of the wire as this may aid fraying of the insulation. Lacing cord should be tied and secured with a double knot. Cable ties are self locking for a more professional and permanent fix. Cable looms may run for long distances through the aircraft and because of this, cable loom supports known as ‘P’ clips are used at distances stated in the aircraft maintenance manual. As a general rule, the loom should be supported so that no wire is stretched during the expansion and constriction due to the hoop stresses endured by a pressurised aircraft structure during normal flight operations. Having said this, it is not permitted that the loom may exceed more than 1/2 an inch deflection between its supports when the clamps are tightened and a moderate hand force is placed on the loom in the middle between the two clamps. When routing looms near plumbing lines, they should always be level or above the pipeline and it is no closer than half an inch although a six inch gap is preferred where possible. If the gap is less than two inches then a sheathing resilient to the fluid carried in the pipeline should be used especially if it is oxygen or hydraulic fluid. Obviously it is not preferred that looms are routed near moving components but sometimes it is inevitable. When this is the case then there must be mechanical guards fitted to protect the cable and a distance of at least three inches must be maintained from the components path of travel throughout its entire range of movement. When securing cables by cable clamps or p clips, the clamp must be secured directly to the structure if it is being used to support the loom, but if it is only to maintain the spacing of the loom between plumbing lines and the loom itself, then providing that the minimum distance spacing is achieved, then a P clip around the loom may be bolted to another P clip located around the plumbing line may suffice. The bend radius of a loom should be gradual and constant, preferably of approximately ten times the outside diameter of the loom in that area but if the bend must be Tighter then, providing it is adequately supported then a bend radius of approximately Three times the outside diameter of the loom in that area is possible but always check your aircraft standard practice manual. Shielded or screened cables are cables that are covered in a metal braid. This metal braid should be turned back on itself at the end and secured with tinned copper wire or should be cleanly cut off without damaging the insulation or the wire underneath the braiding. If the wire to be routed is a co-axial cable then it must be routed in the most direct manner as possible. Important note; It is not permitted that an unscreened radio aerial lead be passed any closer than 18 inches to any other unscreened aircraft cable. Heat shrink wrapping of wires is a simple process of slipping over an approved piece of heat shrink of the desired length and diameter just slightly larger than the wire or wire group and heating with a WARM air gun set to the appropriate temperature for that heat shrink. Remember if it is too hot you may damage the wire itself.

Connecting Electrical Wire/Cables and Connectors

Connection of wires is performed, in the majority, by two methods either by the use of plugs which insert in to a mating plug with a special external barrel with a screw thread which is turned to lock the connecting plugs together or by a form of terminal block. When using terminal blocks it is important to know the proper installation practice to prevent corrosion and damage to the block and terminals.

If you are connecting copper wire terminals to the block then you should

  • Connect the wire terminal directly onto the nut securing the terminal block stud.
  • Place a plain washer over the terminal.
  • Followed by a self locking nut or, if there is not a self locking nut available, you may use a spring steel locking washer followed by a standard nut.

If the terminal you are connecting is for an aluminium wire then you should

  • Place a plain brass washer over the terminal block stud securing nut
  • Then place the wire terminal onto the stud.
  • Followed by another plain brass washer
  • Then either a self locking nut or spring steel lock washer followed by a plain nut.

If you must connect an aluminium wire terminal and copper wire terminal to the same stud then the following order must be achieved:-

  • Place the plain brass washer onto the terminal stud followed by the aluminium wire terminal.
  • Place another brass washer over the aluminium wire terminal followed by the copper wire terminal
  • Then place a plain washer followed either by a self locking nut or a spring steel lockwasher and plain nut.

Please note that unless the wire terminals are of different materials i.e. copper wire terminals and aluminium wire terminals, then no washer should ever be placed between them.

Electrical Testing – Continuity, Insulation – Aircraft

Continuity testing

What is the purpose of continuity testing?

The purpose of this task is to test for a break in the circuit.

There are two methods of performing this task. Either by a continuity tester ( a 3 volt battery and test bulb or L.E.D.) or by performing the milli-volt drop test using a volt meter. The latter is the preferred method but you must know both and always use the method as defined in the maintenance manual.

Before testing any circuit, The following should be performed:

  • All power removed
  • All circuit breakers, fuses and switches are in there necessary positions with respect to the maintenance manual. Note, Circuit breakers must be closed to test that circuit but some circuit breakers may need to be tripped to isolate that circuit to prevent damage to other sensitive circuits that may be connected Directly or in-directly,


If performing the milli-volt drop test, you may now apply power as required to put that circuit into its usual working condition but

  • Always work progressively and systematically
  • Always try to start nearest the supply end of the circuit if the circuit must be tested in sections.

Continuity tester method

To perform a continuity test using this method you must simply connect the positive side of the battery to one end of the circuit, connect the bulb or L.E.D. to the negative side of the battery and then connect the end of the circuit, that is not connected to anything, to the bulb. If there is an unbroken circuit, the bulb will light up and vise versa. This must always be performed on a circuit isolated from other power sources.

Millivolt drop test

This test is more preferred because not only will it tell you if you have a circuit, but it will also signify the condition of the circuit. This test is accomplished by referring to the maintenance manuals for the allowable voltage drop and test connection points. Once you have consulted with the maintenance manual and put the aircraft circuit breakers, fuses and switches in the desired configuration, Then connect your voltmeter to the test connection points and take your volt reading. Now compare your results with the allowable limits in the aircraft manual.

Please remember the following:-

  • The milli-volt test requires the circuit to be powered up to its normal operational load so there is a hazard of Electric Shock so you must be aware of electrical safety and how to protect and insulate yourself.
  • If the circuit fails the test, check the circuit for corrosion, condition and that the terminals are clean and clamped correctly.

Insulation testing

Insulation testing is performed to check that the insulation of the wires within a circuit has not degraded or failed. This task is performed by following the directions in the maintenance manual of which normally follow the steps laid out below:-

  • Disconnect all power sources from the aircraft which includes the aircraft’s own batteries as well as external power.
  • Main power switches should be in the normal stand alone position. i.e. External power off, battery and generators switched on.
  • Circuit breakers should be in the position as required by the maintenance manual. Remember that although you must have the circuit to be tested with no circuit breakers pulled.
  • Some circuits which are voltage sensitive might not appreciate 300 volts being put up them and must be isolated as per the maintenance manual. This may be by means of physically unplugging them or just by pulling their circuit breakers.
  • All ancillary equipment that might be affected by the circuit(s), must be isolated or disconnected prior to the test.

The tests now differ for the two types of systems in use, The Double pole and the single pole, The latter being the system commonly in use today, but because there are still old aircraft flying and you must know everything, as well as have a maintenance manual, both methods are shown below:

Single pole system

Place one lead connector on to the earth ( normaly the casing or aircraft structure and then the other lead connector to the wires or leads of the circuit to be tested. If the resistance is less than allowed in reference to the aircraft manual, then the exact wire which has failed must be traced and the fault located and rectified.

Please note that although this method allows a bunch of wires to be tested together to save time, It is preferred that each wire be tested individually.

Double pole system

To test the insulation on a double pole system, you should follow the following process and order. First measure the resistance between the positive and negative battery leads ( leads must be disconnected from the battery),then the resistance between earth and the positive battery lead, and then do the same for the negative battery lead.

Post Testing

After the insulation tests have been performed, then it is necessary that the wiring is connected back up to its ancillary equipment and that the circuit breakers are reset to the required positions. Once the system has been restored, then a function test must be performed in accordance with the maintenance manual before release to service.


This article was written according to aircraft standards but the principles of Chains remain the same but if applying the knowledge to low power chains on Bicycles, Then you can make your own risk economic based reduced standards. If working on aircraft, always refer to the Maintenance manual.

The purpose of chains is to transfer power from one sprocket to another transfer kinetic(motion) energy. To accomplish this task you need at least an assembly of chain(s)(manufactured to SBAC standards like BS228:1994 or ISO606-1982), sprockets(toothed wheels) and possibly other accessories like interplaner blocks for changing the direction of the chains.

We will start with the main unit called the chain. This is an assembly of:-

  • outer plates
  • inner plates
  • Rollers
  • Bearing pins
  • Bushes

The pitch of the chain is taken from centre of one roller to the next one i.e. the distance between the bearing pins.


Chains riveted links are not allowed to be broken down and re-riveted and only accepted from an approved manufacturer, with the correct packaging and transportation precautions taken.

It is permitted that a bolted joint may be disassembled and re-assembled, but, it is worth while noting these next few points.

1) SBAC states that all nut and bolted chain assemblies must be peened with the exception of the 8mm variety which must be split pinned

2) All nuts used on the chains must be locknuts(this nut is normally part of the outer plate)

3) All attachments must be either riveted or bolted

4) SBAC have standardised four sizes of chains by pitch size


British Standards have laid down the proof load as one third of the minimum breaking load (mbl)

5) Continuous(endless) chains must consist of an even amount of gaps between rollers(pitches)

6) The following table is the four classifications of chains and their statistics.

PITCH — MBL(lbs) — PROOF LOAD(lbs) — BS
8mm ——— 800 ————- 267 ——————— 1
0.375″ ——- 1900 ———— 634 ——————— 2
0.5″ ———– 1800 ———— 600 ——————— 4
0.5″ ———– 3500 ———— 1166 ——————- 6

7) A non-reversible chain is a chain that may only fit a certain way round which can be achieved by correct unsymmetrical positioning by the outer plates fitted to the chain.

8) Irreversibility can be achieved by

  • Non-reversible chains
  • Non-interchangeable end fittings
  • Correct positioning of sprockets
  • Guards and shrouds

9) When storing a chain it must be well soaked in the approved oil, laid flat on its side on top of greaseproof paper and coiled firmly (not tight but not too loose).


This unit is used as a high strength power transfer device. When inspecting the chain make sure to check the proceedure in the maintenance manual which should at minimum account for the Following

  • Wear on the sprocket ( See spec in aircraft manual)
  • Wear on the rollers ( See spec. in aircraft manual)
  • Twisting (This is cause for rejection)
  • Stiffness ( This can be determined by drawing the chain around the fingers on your hand or maybe a substitute of the same sort of shape and texture [ You do not want to damage the chain by scraping the links on an object used in inspection] and checking for smooth articulation of the links. If stiffness is detected, the chain may first be cleaned and re-checked but if this is not a solution, the rollers may be lightly TAPPED preferably with a small pin hammer. if this does not fix it the chain is the scrapped.
  • Deformities, Cracks or corrosion ( These is cause for rejection)
  • Overheating (Bluing)
  • Elongation (Maximum of 2%)( To check for this the chain must be cleaned and dried with compressed air. Lay the chain flat and straight and apply a tensile load/ force [see table below]. Now measure the distance between all the pin centres and apply the following formula:

Percentage of Elongation (Method 1)

Length Of Chain with Force applied x (No. Of Pitches x Pitch measurement)
No. Of Pitches x Pitch Measurement

Note: All measurements are in inches

Tensile load required on Chain (Size is British Standard)
Size – Load (lbs)
1 —- 12
2 —- 16
4 —- 28
6 —- 28

Percentage of Elongation (Method 2)

Measured Length
——————————— x100
Original Length

Control Cables – Teleflex Control Systems

This type of control system can be used in both push and pull directions and gives positive,accurate control to a remotely located device on the aircraft with only one cable. The advantage of accurate control at the receiving end by the use a sliding link or toothed wheel means that the system may be used in various positions for use with precise controls by a method of locking or restraining the lever or control device at the transmitting end by use of a system like a lever that has position locks in the form of detents (notches cut into the cotrol lever casing which the lever can lock into thus restraining it from moving until it is released from the detent/notch.

In some systems, a combination of Teleflex and conventional push/pull rods can be found to have its advantages.In this type of combination, there is Teleflex systems on either ends of the control run which are linked by push/pull rods.

There are two types of cables available.DS 23/2 OR DS 380. Both types of cable have a high tensile steel core. The DS 23/2 (also called a number two) cable has a right hand compression winding around the core which then has a left hand helix winding which is pitch spaced with a spacer winding.

The DS 380 cable has a larger diameter core wire than the DS 32/2 cable. This cable also has no compression winding. The helix winding is a right hand helix winding which is also pitch spaced by a spacer winding.

These two types of cable can be run in either a flexible conduit or a rigid conduit but Flexible conduit can have problems with excess backlash due to the clearance required between the bore of the conduit and the cable although Flexible conduit can be used in areas where the fixture may move.

Due to the backlash problem, it is necessary to keep the conduit and cable as short as possible. These cables are manufactured to be used in specific areas and the correct part number from the Illustrated Parts Catalogue must always be used.It is normal that this conduit/cable can vary in length by up to 10% and cannot be bent in a radius tighter than 9″.

Rigid conduit does not suffer from backlash to the same extent as flexible conduit and can be made from Aluminium, Light alloy, Tungum or Steel. Aluminium conduit is normally lined with PTFE (PolyTetraFluoroEthylene) to reduce friction between cable and conduit thus reducing wear and heat. Do not forget that cables expand as they heat up thus possibly moving controls. This is highly undesirable.

Teleflex control systems are normaly accompanied by various devices to aid their reliable operation including the following:- 

Anti-vibration devices (Damping devices)

This is normally accomplished by a sprung loaded friction plate sprung against the gear wheel which is adjustable so that the force applied can be adjusted to ensure that the control cannot be adjusted inadvertantly by the vibration in the system.This is normally located in the transmitting device


Quick Break Unit 

This is a unit that allows the rapid removal of an item in the system without altering any of the settings of the system. This saves time in fast component replacement which is very valuable in fast turn-around situations as found on the highly pressured ramp/line environments. There are many forms and designs of quick break units in use today but the basic components are:-

connecter box / casing

interlocking rods fitted to the ends of the cables


Swivel joints

This is a ball and socket joint used where angular movement is required. The control is permitted to move only 45 degrees either side of the central position (90 degrees total). The angular travel is 8 degrees either side of the central axis giving a total movement of 16 angular degrees.


Conduit/Cable connectors

When lengths of cables are needing to be connected to complete a control system cable run, connectors are required.They sometimes are equiped with nipples for lubrication and can be fixed to the structure. It is worth noting that the type of connector used with the PTFE type of conduit has a larger internal bore than a standard connector.With all this in mind the necessity to check the IPC for the part number is obvious.


Sliding end Fittings

These units are used where it is not necessary to convert lateral motion into any other form of motion. This is operated by the pushing and pulling of the cable by a handle located on the transmittting end of the conduit and secured by a split collet or lock spring and plug assembly. Like many other cable connections a witness hole is provided to ensure safe engagement.



Control Cables – Bowden Control Systems

This type of control cable is used to operate remote control systems on the aircraft. A remote control system is a system where the controls are located in another area of the aircraft in relation to the item to be controlled. For example Landing gear emergency extension.

Bowden control cables are constructed from stainless steel cable, Then coiled wire is placed around the cable which is covered by a cotton braiding which in turn is housed in a conduit to keep out moisture and contaminants. Then a cap is placed on the end of the conduit (not cable) to stop the coiled wire from unravelling and help to seal the end of the conduit.On the end of the the cable a nipple is either soldered or swaged on (see maintenance manual and airworthiness notices to see which one to use). to transmit the control load. Depending on the type of fitting and control there are three types of nipples available, Plain, spherical or Trunnion (Refer to the maintenance manual for the correct one to use). It must be noted that this system is designed to operate lightly loaded components/systems.

This type of control will only operate in one direction like a normal cable and therefore some means of moving the control back must be provided, This is achieved by the two methods, either by two cables, This gives control in both directions , or a cable and return spring.

This type of control , like any cable can become slack over its service life. This problem is overcome by the addition of one of two little devices. These two devices are adjustable stop or double ended stop. The adjustable stop is the standard stop consisting of a tee-barrel, locknut and hollow threaded portion fixed on the conduit at the receiving end of the cable which is fitted through the tee-barrel which is mounted to the structure of the aircraft. A lock nut is fitted to stop the adjuster moving.

The second type of adjuster is the double ended stop. This type is used when the system does not permit appropriate access to the ends of the cable to permit the use of the standard adjustable stop. This is located at an accessible portion of the cable and is easily adjusted in the same manner as the adjustable stop with the exception that the tee-barrel is replaced by an internal female threaded hollow tube which is fitted with a witness hole to inspect for serviceability.

Sometimes it is necessary to connect Bowden control cables to other types of control cables and this is achieved by a cable connector. When only a one to one joining is needed, you can use a cable connecting barrel. When it is necessary to connect one cable to more than one cable, a junction box may be used.

Operating hand levers are located at the transmitting end of the cable and connect to a cable nipple to transmit the control load onto the cable. The most common types are Thumb, Ratchet and plain type. The ratchet type and plain type both have a three and a half inch throw in radial motion. The ratchet type operates on a ratchet mechanism so that more than one pull of cable is possible to allow more cable movement whereas the plain type can only use one pull on the cable thus limiting the movement on the other end of the cable.

The thumb type of hand lever works on the same mechanism as the plain type of hand lever but has a shorter lever thus giving a shorter throw of only one and a half inches.

Axial alignment of cable assemblies must be such that the centre line of the cable within the conduit is in a straight line through the mid position of the rise and fall of the arc of travel of the lever. This can be more simply explained by moving the control lever to three quarters of total travel one way, check that the cable is in a straight line with the conduit. Now move the control lever to three quarters of total travel in the opposite sense (the mirror position of earlier) and check that the centre line is straight with the rest of the conduit as before. The reason why this is so important is that when a cable is moved through the angles of the control it can rub and chafe against the the casing of the control lever thus giving accelerated wear and possibly impairing flight safety in the future.

The inspection of a Bowden control system is called upon at regular intervals along with the maintenance and lubrication. As with a normal cable system you would follow the service manual for the correct methods and lubricants but in general you would inspect for:

  •             Corrosion
  •             Deformation, bends, kinks
  •             Chafing
  •             Tension
  •             Cleanliness
  •             Broken strands or wires
  •             Other forms of damage or cause for concern.


Remember you are going to be a professional, DO NOT EVER TURN A BLIND EYE, If you are unsure always fail until you can prove otherwise by further research not the other way round. Remember at 36000ft there are no second chances.