aviation cable factory

Aviation Cable in Aircraft Braking Systems: Keeping You Stopped Safely

In the complex world of aircraft, reliable braking is non-negotiable. While hydraulic and electronic systems grab attention, ​aviation cable (also known as Bowden cable or mechanical control cable) remains a vital, often unseen, component in many aircraft braking systems. Understanding its role and maintenance is key to ensuring your aircraft stops predictably every time.

The Critical Link: How Cables Trigger Braking

In many general aviation aircraft, particularly smaller piston-powered models, the pilot’s brake pedals aren’t directly connected to hydraulic fluid. Instead, they link to the master brake cylinders via ​aircraft control cable. Here’s how it typically functions:

1. ​Pilot Input: Pressing the brake pedal applies force.
2. ​Cable Transmission: This force pulls on the aviation cable core running inside a protective housing (conduit).
3. ​Actuation: The cable core travels to the master cylinder’s input lever. Pulling this lever pressurizes the brake fluid in the hydraulic system.
4. ​Hydraulic Action: Fluid pressure travels through lines to the brake calipers or drums located at the wheels.
5. ​Braking Force: Pressure actuates pistons in the calipers, squeezing brake pads against discs (or shoes against drums), creating friction to slow the aircraft.

Essentially, the aviation cable translates the pilot’s leg force into the initial hydraulic pressure needed for braking.

Why Aviation Cable? Importance in Braking Systems

• ​Mechanical Simplicity & Reliability: Proven technology that is less complex than full fly-by-wire systems.
• ​Direct Feel: Provides pilots with tactile feedback regarding braking input.
• ​Durability: High-quality cables are designed to withstand significant operational loads and environmental stresses.
• ​Weight & Space Efficient: Often a lighter and more compact solution for mechanical force transfer over distances compared to alternatives.

Common Cable Problems Impacting Brakes:

• ​Corrosion: Moisture ingress, especially in salty or humid environments, can corrode the inner cable core, increasing friction or causing stiffness.
• ​Internal Friction: Buildup of dirt, debris, lack of lubrication, or corrosion inside the conduit causes the cable to move stiffly or bind.
• ​Wear & Fatigue: Constant movement and tension can lead to strands fraying or breaking inside the housing, often detectable at cable ends.
• ​Contamination: Grease, dirt, or corrosion products inside the housing increase friction and impede movement.
• ​Misalignment: Improper routing or kinks in the conduit increase friction and stress on the cable.

Essential Brake Cable Care: Prevention & Solutions

Ensuring reliable brake operation requires proactive cable maintenance:

1. ​Regular Visual Inspections: During scheduled maintenance and pre-flights (where visible), check cable ends:
   • ​Fraying & Broken Strands: Look for ANY broken wires at terminals or swages. ​Replace immediately if found.
   • ​Corrosion: Check for rust or corrosion on terminal ends and exposed core.
   • ​Security: Ensure all terminal end nuts, turnbuckles (if used), and clamps are tight and safetied.
   • ​Conduit Condition: Look for kinks, dents, or excessive wear on conduit surfaces.
2. ​Smooth Operation Check:
   • Operate brakes (ensure chocks are in place/wheels clear).
   • Movement should be smooth and consistent. Stiffness, binding, or a “jerky” feel indicate internal friction.
   • Pedals should return positively to the neutral position when released; sluggish return points to cable friction issues.
3. ​Contamination & Lubrication Control:
   • ​NEVER spray lubricant directly into conduit ends unless explicitly approved by the aircraft manufacturer/Service Manual. Improper lubrication attracts dirt, creating sludge.
   • Only use lubricants specified in the Aircraft Maintenance Manual (AMM).
   • Apply approved lubricant VERY sparingly ONLY to exposed cable core at terminal ends where it enters/exits the conduit, according to the manual procedure. Wipe excess.
   • Check conduit end seals/boots for integrity to prevent moisture ingress.
4. ​Replacement: ​Follow AMM intervals & criteria strictly. Replace cables if:
   • ANY broken wires are detected.
   • Corrosion has penetrated beyond surface discoloration.
   • The core is seized or excessively stiff even after checks/lubrication per AMM.
   • It has reached its calendar life limit or operating cycle limit specified by the manufacturer.
   • ​Always use certified replacement parts!
5. ​Routing Security: Ensure conduit is correctly routed per diagrams, secured with proper clamps at specified intervals, and protected from chafing against airframe components.

Conclusion

Aviation cable is a critical link in the safety chain of many aircraft braking systems. Its seemingly simple function masks its importance: the difference between a safe stop and a potentially dangerous situation often hinges on the integrity of these cables. Rigorous adherence to inspection routines, strict compliance with lubrication and replacement procedures from your aircraft’s Maintenance Manual, and a zero-tolerance policy for visible defects like broken strands are paramount. Never compromise on the condition of your brake cables – your safe return to the ramp depends on them.