The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.
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Control cables are a critical component of most aircraft flight control systems. The cables are usually manufactured from carbon steel or stainless steel and are lubricated during the manufacturing process.
Both types are susceptible to the effects of corrosion, especially if the lubrication is wiped away by fairleads, stuck pulleys, or is oxidized away over long time periods. Moisture accelerates the process.
The FAA has received reports of corrosion in Cessna 172 aileron control cables in the area at the top of the rear doorpost. Corrosion is most likely in older airframes that have been stored outside. This part of the control cable is difficult to inspect. The latest Cessna Maintenance Manual describes how to remove the cable and inspect it.
A partial inspection, while not as complete as removing the cable, will give some indication as to the condition of the cable.
Gain access to the area through the zipper in the headliner. Rotate the control wheel fully to present the maximum length of cable for inspection. Rotate the wheel to the right for the left side and left for the right side.
Corrosion will be indicated by broken wires or powdered, oxidized metal on the surface of the cable.
Examine the cable by rubbing it with a soft white cotton cloth. If the cloth snags, broken wires are present. The cloth will also wipe away some of the powdered, oxidized metal, producing a change in the surface color of the cable and of the cloth.
A fatal aircraft accident, involving a Cessna 172M and reported here in the July 2002 issue, was attributed to a corroded left aileron cable that failed at the point where it passed over the pulley at the top of the right doorpost. At this location, the cable makes a right angle change of direction from vertical upward inside the doorpost to horizontal across the top of the cabin.
Beech F33A Bonanza
Landing Gear Defect
After landing safely, the pilot stated the landing gear failed to extend during the approach. He used the emergency system to get the gear down and locked.A technician conducted a gear retraction test with the airplane on jacks and discovered the Eaton dynamic relay was stuck in the up position and prevented the gear from extending. After replacing the relay, the landing gear system operated properly.Part total time – 518 hours.
Beech F33A Bonanza
Poor Engine Operation
The pilot said the engine ran poorly at high altitude but performed acceptably at lower altitude.A technician determined the engine fuel flow divider delivered fluctuating fuel flow to the engine. Part total time – 318 hours.
Beech 58 Baron
Unsecured Cabin Entry Door
The pilot reported the cabin entry door popped open at the top edge during takeoff. He returned to the airport and landed safely.A technician discovered severe wear on the upper latch door handle assembly and the upper door latch channel assembly.
Beech 60, A60, B60; Duke
Split Electrical Wiring Insulation
During an accident investigation, an inspector discovered the 6-gauge wire used to attach the generator had numerous lateral splits in the wires insulation.The splits in the wiring insulation appear as small fine dark scratches on the wiring outer covering and run lengthways with the wire. The wire type involved in this accident was M22759/7, and it might be used on other aircraft makes and models.
Beech E90 King Air
Elevator Structural Defect
While conducting a scheduled inspection, a technician discovered several structural defects on the elevator assembly.The left elevator had cracks on the inboard rib, rib doubler and inboard main spar flange. The cracks were mainly located in the bend radii in the area where the inboard end of the elevator torque tube is attached. The cracks varied in length from 1.3 inches on the spar flange to 3.5 inches around the rib circumference, and they followed the shape of the torque tube attachment casting.Part total time – 6,851 hours.
Beech 200 King Air
Main Landing Gear Defect
During a landing gear retraction test, a technician discovered the jackscrew nut assembly for the left main gear retraction actuator was broken.The threaded screw was disconnected from the chrome tube and allowed the gear to fall down but not lock down.The submitter discovered the jackscrew nut weldment was defective. Beech issued Service Bulletin 32-3433, which describes this type of defect and gives guidance for correction. In this case, the technician replaced the retraction actuator.Part total cycles – 1,123.
Cessna 172S Skyhawk
Inoperative Avionics Cooling Fan
The owner reported the avionics cooling fan was inoperative. He stated there was an electrical burning odor and the cooling fan circuit breaker had opened on several occasions.The technician discovered the fan wire bundle had chafed against the back of the avionics buss and penetrated the power wire insulation. The circuit breaker contacts were melted and severely heat damaged. He also discovered the defective cooling fan circuit breaker was rated at 5 amps instead of the 1 amp circuit breaker recommended by the manufacturer.
Cessna 208B Caravan
Cargo Door Security
After a very short flight, the pilot stated the cargo door came open just as the aircraft left the runway during takeoff.A technician discovered the cargo door would pop open because the door spring tension on the upper door handle was insufficient to produce positive locking when the latch was engaged.
Cessna 208B Caravan
Defective Wing Flap Cable
During a scheduled inspection, a technician discovered a wing flap cable was defective.The technician found several strands broken on the right flap outboard cable at the swaged terminal that connects the cable to the outboard end of the flap. The defect could have occurred where the cable adjacent to the cable terminal flexes. Over a long period of time, the flexing may have caused the metal to work harden and the cable strands to separate.Part total time – 2,998 hours.
Cessna T210N Centurion
Engine Control Failure
During takeoff, the pilot noticed the engine operation was rough. He returned for landing immediately at the departure airport. The technician discovered the engine mixture control cable had failed at the crimp swivel joint on the engine fuel control, leaving only the rod-end and a small portion of the mixture cable attached to the fuel control. Part total time – 1,000 hours.
Cessna T210N Centurion
Horizontal Stabilizer Loose
During an annual inspection, a technician noticed the horizontal stabilizer was loose.The aft mounting reinforcement bracket was broken on both sides and the forward attachment fitting was loose. Part total time – 4,202 hours.
Piper PA-28R-201 Arrow
Defective Engine-Induction System
While conducting a scheduled inspection, a technician discovered the airbox door and the hinge assembly on the engine air-induction system were bent. The deformity allowed unfiltered air into the engine. The FAA Service Difficulty Reporting (SDR) Program data base contains two additional reports of airbox hinge failure.Part total time – 513 hours.
Piper PA-28RT-201 Arrow
Defective Engine Muffler
During an annual inspection, the technician discovered the aft engine muffler was defective.The muffler assembly appeared to be distorted and was cracked adjacent to one of the steel exhaust tubes. The muffler internal flame tubes were loose, broken and could be removed by hand.Part total time – 1,409 hours.
Piper PA-31-350 Chieftain
Engine Exhaust System Defect
During a scheduled inspection, a technician noticed an engine exhaust stain on the right engine turbocharger mount.The exhaust stain appeared to come from the junction of the turbocharger and the turbocharger transition assembly. The divide was cracked, causing the transition assembly to warp, leak exhaust gases and leave deposits on the mount.Part total time – 1,693 hours.
Piper PA-31-350 Chieftain
Engine Failure
The pilot reported aborting a takeoff because the right engine failed during the takeoff run. The technician learned the pilot made a rolling takeoff immediately after turning onto the runway.The technician could find no discrepancies and concluded the rolling takeoff caused the wing fuel supply to concentrate at the outboard end of the tank. This left the engine fuel supply port uncovered and led to engine failure due to fuel starvation.
Piper PA-32-300 Cherokee Six
Premature Engine Failure
While conducting a scheduled inspection and engine oil change, a technician found ferrous metal slivers in the oil filter. He removed the number 1 and number 3 cylinders and discovered metal imbedded in the piston skirts and the cam lobe shared by the number 3 and the number 4 cylinder exhaust push rods. In addition, the number 3 and number 4 exhaust cam lobe and cam followers were severely pitted.The engine manufacturer was contacted and the case was still open.Part total time – 496 hours.
Piper PA-34-200T Seneca
Loose Fasteners
While conducting a scheduled inspection, a technician discovered the rivets attaching the left and right stabilizer trim surface brackets were loose and smoking. The brackets are used to attach the stabilizer trim push rods.Part total time – 2,780 hours.
Piper PA-44-180 Seminole
Magneto Drive Defect
Shortly after the installation of two factory remanufactured engines, a technician discovered a problem with the left engine magneto drive gear.The left engine magneto drive gear was seized to the crankshaft bushing. The bushing was spinning in the crankshaft bore. The same condition was found in the right engine. Part time since overhaul – 219 hours.
Piper PA-46-310P Malibu
Engine Exhaust System Defect
The pilot reported the manifold pressure slowly decreased from 25 inches to 22 inches with full throttle.While inspecting the aircraft, a technician noticed exhaust gas stains in the right cylinder bank area and discovered the engine exhaust system was broken adjacent to the turbocharger flange. This failure caused inefficient turbocharger operation and the low MAP indication reported by the pilot.
