REGULATORY SUPPORT DIVISION
|SAIBs are posted on the internet at http://av-info.faa.gov|
|This is issued for informational purposes only and any recommendation for corrective action is not mandatory.|
The purpose of this Special Airworthiness Information Bulletin (SAIB) is to inform registered owners of Navion airplanes (all models) of reports of corroded flight control cables and methods for inspecting for this condition.
Aileron Control Cables
The FAA received a recent report of corroded and deteriorated aileron control cables. The area of damage was located in the first rib bay outboard of the wheel well. One aileron control cable had only two strands holding it together. The exposed ends of the cables, in the wheel well and at the aileron bell crank, appeared normal and serviceable.
The aileron control cables can be inspected by removing the flap control rod bolt, and allowing the flaps to hang down 900. The aileron control cables can then be inspected through the wing trailing edge lightening holes after removing the lightening hole covers or gap seals if installed.
Elevator control cables
Two reports were received concerning corroded elevator control cables in the cabin under the rear passenger seat. This area, also containing the rudder cables and the aileron interconnect cables is vulnerable to contamination with dirt, foreign object damage (FOD), and moisture accumulations, especially when an auxiliary fuel tank is installed under the rear seat. If the aircraft does not have an under seat fuel tank, these cables can be inspected by removing the panel under the front edge of the rear seat to access the cables. Also, this will provide inspection access for the pulleys and internal structure.
Aileron Control Cables
The FAA recommends that the aileron cables be visually and physically inspected during each annual inspection. The entire length of the control cables should be checked visually and physically (run a shop towel or rag over the cable to see if any loose strands catch on the rag) for evidence of corrosion or damage (broken strands, etc.). If the cable integrity is still in doubt, the cables should be disconnected from the bell crank and pulled into the wheel well for further inspection.
Aileron cable routing, over the two pulleys outboard of the wheel well, makes it easy to cross the cables during installation. Before disconnecting the cables, it would be wise to make a drawing of the cable routing to reduce the chance of miss-routing the cables during reinstallation.
Attaching a guide wire, cable, cord or other device to the cable end prior to removal should insure proper routing over the pulleys during reinstallation. Also, it would be wise to note which hole on the bell crank connects to the cable turnbuckle fork. Checking for correct flight control operation after installation should eliminate errors.
Check for jammed or frozen aileron cable pulleys, especially the ones just outboard of the wheel well. If the pulley does not turn, the action of the cable passing over it will likely damage the cable and/or pulley.
Elevator control cables
Two other reports were received concerning corroded elevator control cables in the cabin under the rear passenger seat. This area, also containing the rudder cables and the aileron interconnect cables is vulnerable to contamination with dirt, FOD, and moisture accumulations, especially when an auxiliary fuel tank is installed under the rear seat. If the aircraft does not have an under seat fuel tank, these cables can be inspected by removing the panel under the front edge of the rear seat to access the cables. Also, this will provide inspection access for the pulleys and internal structure.
For aircraft with a fuel tank installed under the rear seat, access to cables and pulleys may be obtained by inspecting from underneath the baggage compartment after removing either the inspection plates in the aft wing filet fairing or by removing the fairing itself. The cables and pulleys will be readily visible on aircraft with the after-market "McKenna" fairings when the lower half of the fairing is removed to inspect the flap linkage and actuating cylinder.
Elevator trim tab cables
The elevator trim tab cables (enclosed in a "Bowden Cable" type housing) should be inspected at the exposed ends with the trim adjusted both full up and full down. If there is any indication of damage, all four cables should be replaced.
Service Difficulty Reports (SDR)
The FAA requests that any findings of corroded or otherwise damaged flight control cables including airplane model, total hours, type of storage environment (hanger/dry/wet climate/etc.) and any other airframe corrosion damage, be reported to the FAA via the SDR system. SDRs may be reported on FAA Form 8010-4, Malfunction or Defect Report, or electronically by contacting Isaac Williams, Aviation Safety Inspector; Aviation Data Systems Branch, (AFS-620); telephone: (405) 954-6488; or email: firstname.lastname@example.org.
FOR FURTHER INFORMATION CONTACT:
FAA, Chicago Aircraft Certification Office; Nick Miller, Aerospace Engineer; 2300 East Devon Avenue, Des Plaines, IL 60018; telephone: (847) 294-7837, fax (847) 294-7834; email: email@example.com or FAA, Small Airplane Directorate; Karl Schletzbaum, Aerospace Engineer; 1201 Walnut, Suite 900, Kansas City, MO 64106; telephone: (816) 329-4146, fax: (816) 329-4090.