While all aircraft have periodic inspections, large aircraft have to go through an extensive inspection process, also referred to as “checks.” There are several checks that need to be done according to calendar dates, flight hours, or flight cycles. A flight cycle is one flight, with a take-off and landing.
Aircraft owners are responsible for keeping their aircraft airworthy. Find ways to save some money by doing the routine preventive maintenance on your own aircraft. Access general aviation maintenance alerts here, or browse through a variety of AOPA articles on maintenance-related topics.
Pilot’s Guide to Preventive Maintenance
By performing routine maintenance on their own aircraft pilots not only become better educated about the equipment they fly, but might also save a substantial percentage of their annual maintenance costs.
Most general aviation aircraft control systems include flexible steel cables, otherwise known as wire rope. The cables can be manufactured from galvanized steel or stainless steel alloy, depending on the specs from the aircraft manufacturer. The most common aircraft cable diameters are 1/16 through 5/32 with 7x7 or 7x19 construction.
The most common control cable sizes (depending on strength required) are 7x7 and 7x19 cables. A 7x7 cable consists of six strands of seven wires each, laid around a center strand of seven wires. A 7x19 cable has an additional layer of 12 wires laid over the 7x7 in the opposite direction.
What does that mean in English? It means that your control cables are made from individual steel wires wound in bundles and grouped together to provide both strength and flexibility. It also means that there are many layers of wires within a control cable and you can’t tell the true condition of a cable from a cursory visual inspection while it is installed in the aircraft.
Aircraft cables live in fairly harsh environments with temperature changes and exposure to the elements. They are subject to wear and deterioration and remain in static positions around pulley bends for extended periods of time while the aircraft sits. Sadly, most control system cables in the GA fleet are original to the aircraft and have remained in service for far longer than their intended design life.
100 HOUR INSPECTION:
At every annual or 100-hour inspection, all control cables must be inspected for broken wire strands. The easiest way to check for exposed strands of broken wire on a cable is to have one person move the cable through its length of travel while another person holds a cotton cloth gently around the wire looking for places that the cable snags the wire. This must be done along the entire length of the accessible cable (although issues are most likely near pulleys and guides).
Any cable assembly that has even a single broken wire strand located in a critical fatigue area must be replaced. Per the FAA guidance, a critical fatigue area is defined as the working length of a cable where the cable runs over, under, or around a pulley, sleeve or through a fair-lead; or any section where the cable is flexed, rubbed, or worked in any manner; or any point within one foot of a swaged-on fitting.
This process is generally OK for identifying external cable damage. However, cables also fail from the inside out due to environmental deterioration, distortion, fatigue, and wear. The only way to accurately inspect cables for internal damage is to remove the cables from the aircraft and flex them manually while inspecting them under a magnifying glass for damage. Since the labor to remove, install, and rig aircraft cables is generally higher than the cost of the cable itself, it generally makes sense just to replace your control cables on a regular basis, such as every 15 years. For tailwheel aircraft, I would personally recommend replacing the rudder/tailwheel cables every 5 years due to the high stress and risks associated with control system failures.
During your inspection, it’s also important to inspect and rotate the pulleys. Rotating the pulleys allows you to check the wear and functioning of the bearings. The wear pattern on the pulley can tell you if the bearing is frozen or if the pulley is misaligned. You should also lubricate the pulleys and cables per the manufacturer’s specifications (if applicable).
The bottom line is that it’s simply not worth the risk to keep flying with 30-plus-year-old cables that have exceeded their design service life. Inspect them carefully at annual, along with the pulleys. Personally, I recommend implementing an incremental replacement process that will ensure that, in some reasonable amount of time, all control cables that may be original to the aircraft get replaced. Start with the most critical systems and replace one cable system at a time (such as the elevator cables) as your budget allows.
If you see any of these signs, then it is time to bring your aircraft into Greenville Air!
We are a certificated 145 repair station
and have passed everyone of our FAA Inspections. That means that we are following FAA Guidelines for safety, installation and paperwork follow-up.
Come see the Greenville Air difference when you come to get your Annual or
100 hour inspection done.
Call today to schedule an appointment
 641-7776 GMU Downtown Greenville SC airport.