6.10 Flashcards
Advantages of cables
Strong
Lightweight
Flexible - easy to route
High mechanical efficiency
Can be set up without backlash - resulting in precise control.
Disadvantages of cables
Tension must be adjusted regularly
Tension varies with temperature
Prone to wear at poins of contact
Strand vs wires vs cables
A number of wires are braided together to form a strand
A number of strands are braided to form a cable.
When twisted in opposite directions the cable is less likely to uncoil
Minimum tensile strength of control cables.
1200 N/mm^2
Non flexible cables
Straight runs only.
1x7 or 1x19
7x7 flexible cable
7 strands, 7 wires per strand.
Only for straight runs or where large pulleys are used
7x19 extra flexible cable
Primary flight control cable
7 strands, 19 wires per strand.
Lockclad cables.
Turns a cable into a type of push rod, used on straight runs and cannon go around pulleys.
Sag is eliminated.
Aluminium prevents corrosion.
Vibration is reduced.
Stretch is reduced.
Coefficient of expansion is near identical to aircraft frame.
Turnbuckles
Mechanical screw device for cables.
Used for making minor adjustments to cable length and tension.
The left hand threaded side can be identified by a groove or knurl around the barrel.
Safety clip locking or can be wire locked.
Both sides must be equally engaged.
Cable tension regulator
Uses extension or compression of sprigs to adjust positioning of the free pivoting cable quadrants.
Compensates for expansion and contraction.
Fair leads
Guides the cable and prevents contact with the structure.
Pressure seals (cables)
Through pressure bulkhead to prevent pressure leakage and air loss.
Control rods (push rods)
Used in flight control systems
Bell cranks and quadrants
Made of heat treated aluminium.
Changes direction of travel in push/pull tubing or to gain a mechanical advantage
Torque tubes
When an angular twisting motion is required in Control system
Bowden cable
Pull only system
Returned by a spring
Can suffer from water ingress which can freeze.
Stretch
Cables suffer from wear and kinking.
Teleflex control cables
Installed on modern aircraft.
Pull and push motion through a single cable.
Provides a more accurate control
3 types of teleflex cables.
DS 23/2
- left hand helix winding
DS380
- right hand helix winding
- greater breaking load
- greater diameter
DS169330
- left hand helix winding
- manufactured from CRES
- can be used in hot areas (up to 350C)
Single entry unit (teleflex end fitting)
Limited to 270 degrees of travel
Minimum f 40 degrees
Double entry unit (teleflex cable end fitting)
Greater travel can be obtained
Spent travel tubs
Straight lead unit (teleflex cable end fitting)
Not suitable for heavy loads
Junction box (teleflex cable end fittings)
Operate two components at the same time.
Anti torsion tube (teleflex cables)
Prevents twisting of cable during operation.
Quick break units (teleflex cables)
Facilitate the removal of components without disturbing the control.
