Reference

Nose Wheel Steering

• How do I know if my steering rods are working properly?

  The Cessna steering system is an engineering masterpiece that is simple in function while allowing good directional control throughout the transition from flight to ground or ground to flight, even in crosswind conditions. A key part of this system is the steering rods. The steering rods are a spring loaded device that applies spring pressure to pull on one side of the nose gear when it is activated and yet have a specified amount of free play in the opposite direction until a solid push is required for positive steering.

   

  The following are some common symptoms of worn out or failed steering rods:

  1. Weak steering (You can push on the rudder but not much happens and you have to use a lot of brake to steer. Often the weakness is one direction only.) The early Cessna steering rod springs were designed such that if the rudder pedal was pushed hard in one direction while the nose gear was pointed all the way the other direction and had some resistance to moving such as soft ground or snow, the spring could be compressed to an extent that it would be permanently shortened leaving it weak. McFarlane has redesigned the spring so this cannot happen.
  2. More or less than 1.2 inches of free play movement or inconsistent free play of the steering rod shaft is present. The spring is retained by a washer that was stop swaged into the steering rod housing. During an overload, such as extra hard pedal force applied with the nose wheel pointed all the way in the opposite direction and restricted or undetected damage from a previous hard landing, the spring retaining washer can be deformed and forced past the swaged stop. This will result in inconsistent free play and erratic function of the steering rod shaft as the washer passes past its designed swaged stop in both directions. The rudder rigging in flight might also be inconsistent. This is a dangerous situation that results in inconsistent steering and the steering rod must be replaced. McFarlane has redesigned the washer and shaft machining to prevent the washer stop failure.
  3. Rust and corrosion can make the steering rods unreliable. The steering rods get water and contaminates from the runway that the nose tire throws at them. The fit of the shaft into the bushing that is swaged into the housing is not a precision fit. This can allow internal contamination, moisture, and salt that will rust the springs and steel housing interior, leaving the components weak and subject to failure. Red rust streaking on the shaft exit area or bubbling of the exterior paint indicate corrosion failure. The McFarlane steering rods are made from 304 stainless steel and have a special corrosion preventative and lubricating coating on the springs to fight against corrosion and wear.
  4. Wear of the shaft and bushing is caused by steering movement and aerodynamic pulse vibrations created by the rotating propeller. This wear can be detected as looseness of the shaft in the end bushing. Some wear is acceptable.

• The free play movement of my new steering rod has a little drag when I push it in and out. My old steering rod does not have much shaft drag. Is there something wrong with my new steering rod?

  No. A little drag is expected and normal on a new McFarlane steering rod. The drag is caused by the thickness of the dry lubricant painted on the spring rubbing on the shaft. The drag is actually a good thing as it prevents vibration wear and will go away as the dry lubricant is worn in. The drag is acceptable when the weight of the spring and housing overcome the drag when the steering rod is held vertical by the threaded shaft.

• What else can cause poor steering response besides the steering rods?

  We have seen torn brackets on the rudder bar torque tube cause lose of rudder motion and steering movement. The earlier Cessna airplanes had less reinforcing of the rudder bar torque tubes where the steering rod attachment brackets are welded on than the later model airplanes. An overload of rudder pedal pressure or prior nose gear damage can cause failure of the bracket attachment. Inspect all of the rudder and steering system when poor steering authority is detected.

• Why are my wheel pant mounting plates cracked?

  Wheel pant mounting plates commonly crack around the axle. If any cracks are present, they should be replaced. The cracks are caused by wheel pant vibration. Assure that the wheel pant axle bolts are tight. Proper wheel balance will lessen wheel pant vibration. McFarlane's wheel balancers can help solve this problem.

• Why did my Cessna nose strut seal fail?

  Strut seal leaks and flat struts can be caused by roll or twist of the main O-ring seal. It is very frustrating to carefully check all the parts and surfaces and put a new seal kit in the strut only to find it flat again after a relatively short time. We have seen this happen when a film of MIL-5606 hydraulic fluid dries out on the exposed chrome strut shaft. MIL-5606 by nature has a tendency to get sticky as it is exposed to air and dirt and then dry.

   

  Very slight dried oil films are sometimes hard to detect and they can get past the plastic wiper seal. When this happens the sticky strut has a tendency to grab the O-ring and roll or twist it when the strut slides in or out causing the seal to distort. A very small O-ring twist or distortion will cause a leak. This phenomena is aggravated by the low pressure that the Cessna strut is designed for. Wipe the chrome strut down with Stoddard solvent (mineral spirits) periodically to soften and remove any dried oil film, dirt, dust and bugs.