Separation Anxiety

Accident reveals broken control cables and corroded pulleys in Cessna 172


The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.


Witnesses in the airport traffic pattern heard the pilot of a Cessna 172M announce on the radio that he had lost all aileron control.

The airplane crashed, and while investigating the accident, an NTSB investigator discovered that two flight control cables were broken. He found that the left aileron control cable separated in the area of the top pulley located at the right doorpost. The cable was severely frayed for several inches on each side of the failure point and there was evidence of heavy corrosion on the cable and inside the pulley track.

When the pulley was removed, it exhibited binding in the bearing, which prevented free rotation of the pulley.

In addition, the right wing flap cable was separated approximately 27 inches from the bellcrank in the area of the right fuel tank. The wing flap cable exhibited the same corrosion and fraying as the aileron cable.

While the location made the failure point difficult to inspect, anyone flying the airplane should have noticed the controls binding during preflight checks.

American Champion 7ECA Citabria
Wing Spar Defects

While restoring the aircraft, the owner found several severe defects on the right wing spars.In accordance with AD 2000-25-02 R1 and American Champion Service Letter 406, Revision A, the owner removed, cleaned and inspected the right rear wing spars.The spars initially appeared to be in good condition, but a high-intensity light revealed four compression cracks on the upper edge of the rear spar and one crack associated with an aileron bellcrank attachment hole. A maintenance record entry, dated January 16, 1993, recorded a hard landing.The submitter stated he would not have found these defects using ordinary visual inspection techniques because the cracks were not visible until the varnish, excess adhesive and dirt were removed.

American Champion 8KCAB Decathlon
Defective Propeller Assembly

During a scheduled inspection, a technician discovered a crack in the propeller assembly.The propeller pitch cylinder was severely cracked on the forward end, with the crack traveling outboard from both sides of the low pitch stop-nut.AD 2001-23-08 deals with this subject, and this aircraft was in compliance with the AD. The aircraft is used in a training environment for aerobatic instruction, and hard use may have contributed to the defect.Part total time – 283 hours.

Beech 58 Baron
Oil Temperature Indication

The pilot reported that after takeoff, he noticed a steady increase in oil temperature on the left engine. The oil temperature gauge was at red line before the pilot could feather the propeller and begin a return to the departure airport.The oil quantity was within limits and there was no physical indication within the engine that the engine oil temperature had been excessively high. The oil temperature circuit was defective.

Beech 58 Baron
Landing Gear Failure

The landing gear would not retract, so the pilot returned the gear control back in the down position and landed.The weather was wet and cold, and the technician discovered the squat switches were frozen. After the technician thawed and dried the switches, the gear functioned properly.

Beech 65-B80 Queen Air
Poor Engine Performance

During an engine break-in operational test, a technician noticed very poor left engine performance when operating on the right magneto.The magneto primary coil retainers were loose inside the case. It was apparent the retainers became caught in the timing gear and caused severe damage to the gear teeth.Part total time – 9 hours.

Cessna 172N Skyhawk
Defective Alternator Installation

While conducting other maintenance, a technician noticed the alternator appeared to be loose at the support bracket attachment point.The technician discovered a spark plug gasket had been used in place of a washer on the alternator attachment bolt. The alternator housing was cracked, the bushing was loose, and the bushing hole was severely elongated.The damage could have been the result of using the spark plug gasket in place of the steel washer.

Cessna 172R Skyhawk
Wing Skin Cracks

While conducting a scheduled inspection, the technician discovered numerous cracks in the left wing skin.The cracks were located in the top trailing edge of the wing skin at the inboard end, adjacent to four rivets just above the wing flap that join the trailing edge stiffener to the upper and lower wing skins. The cracks ranged from 0.5 to 1 inch in length, and only one crack penetrated a rivet hole.It appeared the extreme aft wing root fairing screw contacted the upper skin and caused this crack. The screw shank was longer than necessary. After the technician removed the wing to repair the damage, he discovered a doubler and a flush patch, approximately 9 inches by 4 inches, had been installed.Aircraft total time – 590 hours.

Cessna 172S Skyhawk
Fuel Leak

While conducting an engine operational test, the technician smelled fuel in the cockpit.After shutting down the aircraft, the technician removed the floor panels and found a puddle of fuel. Investigating further, he noticed a fuel stain on the reservoir tank. He de-fueled the aircraft and removed the reservoir tank. After stripping the paint, he conducted a dye-penetrant inspection that revealed a crack adjacent to the lower aft welded seam.The mechanic suspected the crack was caused by improper installation of the reservoir tank.Part total time – 614 hours.

Cessna R182 Skylane
Defective Propeller Spinner

During a scheduled inspection, a technician noticed the propeller seemed loose.Both propeller spinner attachment plates were severely cracked. The cracks traveled through four of the six attachment fastener holes on each attachment plate. It appeared the cracks originated from the corner of each fastener head and went to the outer edge of the plates. There were three cracks on one of the attachment plates and one long crack on the other.The technician removed the bolts from the plates and noticed that no washers had been installed as required by the manufacturers technical data. Evidently, the washers were omitted when the propeller was installed. He inspected two other like aircraft and found the same 12 washers had been omitted. He discovered the washers were omitted from the propeller attachment bolts on all three aircraft.Part total time – 750 hours.

Cessna 208B Caravan
Engine Failure

After an off-airport landing incident, the pilot stated the engine failed and could not be restarted.During an investigation, a technician discovered the engine-driven fuel pump, located on the engine accessory gearbox, had a sheared drive shaft.Part total time since overhaul – 3,972 hours.

Cessna 210D Centurion
Defective Antenna Installation

While completing a scheduled inspection, the technician discovered the emergency locator transmitter antenna was loose.The technician removed the ELT antenna assembly and found the shield-locking nut, used to secure the metal antenna rod to the base assembly, was the source of the looseness. He removed the antenna rod and discovered the female barrel connector solder joint was broken. The antenna rod is secured by means of an insulated plastic housing, located at the base of the antenna, inserted into a compression nut.Part total time – 157 hours.

Cessna 402C Businessliner
Nose Landing Gear Defect

While conducting a scheduled inspection, a technician discovered the nose gear drag brace was severely cracked. The crack was located adjacent to the lug for attachment of the actuator and was in danger of complete failure. Failure of the actuator attachment lug would prevent proper operation of the nose gear.Part total time – 2,244 hours.

Diamond DA 20-A1
Structural Damage

During a scheduled inspection, a technician discovered the vertical stabilizer spar had unbonded from the empennage attachment area and the tail skid area was cracked. The damage may have been the result of the tail striking the runway during flight training operations. Part total time – 1,822 hours.

Maule M6-235 Super Rocket
Defective Aileron Control System

During other maintenance, a technician discovered the left aileron sprocket stop pin was broken, allowing the aileron surfaces to overtravel in both directions, and the balance weights to hit the upper wing skin. The damage may have occurred when the aircraft was parked outside during gusty wind conditions without having the flight control gust locks installed.Part total time – 873 hours.

Piper PA-24-250 Comanche
Landing Gear Failure

The pilot smelled an electrical burning odor and noticed the amp gauge indicated a discharge when he tried to retract the landing gear. He used the emergency extension system and made a safe landing.The landing gear motor had shorted internally. There was evidence the motor assembly had produced excessive heat prior to the failure. Part total time – 1,163 hours.

Piper PA-24-250 Comanche
Landing Gear Failure

During a landing approach, the landing gear extended only partially when the pilot selected the down position. All subsequent attempts to fully extend the landing gear failed. He landed the aircraft with the gear in an intermediate position.The technician discovered that the 5-amp circuit breaker that supplies electrical power to the gear solenoid had failed internally without giving an indication of the failure. Evidently, the circuit breaker failed while the landing gear was in transit.Part total time – 2,652 hours.

Piper PA-28-151 Warrior
Poor Engine Performance

During an annual inspection, a technician found the engine performance was poor.The technician discovered all the carburetor bowl attachment bolts were loose, allowing excessive air to be drawn into the carburetor. The carburetor bowl bolt-locking tabs were in place and properly bent up. It is possible that the bolts were loose due to shrinkage of the carburetor bowl gasket.

Piper PA-28-181 Archer
Flight Control Cable Damage

While conducting a scheduled inspection, the technician discovered the forward right and left stabilator and aileron balance cables were severely worn and frayed. The damaged sections of the cables were located adjacent to pulleys, fairleads and other places where the cables contacted the aircraft structure.The technician found similar damage on another like aircraft and speculated it may have been caused by the use of substandard cable stock and improper cable routing and alignment during manufacture.Part total time – 2,536 hours.

Piper PA-31-350 Chieftain
Engine Fuel Pressure Anomaly

The flight crew reported an intermittent drop in fuel pressure on the right engine.The Janitrol cabin heater, which uses the right engine fuel supply, was operating when the fuel pressure fluctuations occurred. The technician found fuel leaking profusely from the heater fuel pressure regulator and shutoff valve, which had been installed to replace another valve in accordance with AD 2001-17-13. The FAA Service Difficulty Program database contains 33 additional entries concerning this subject.Part total time – 4 hours.

Piper PA-601 Aerostar
Landing Gear Defects

After jacking the aircraft to install a new set of tires, the technician noticed excessive movement associated with the nose gear. He discovered the actuator support structure was severely cracked at numerous locations. Several original members of the actuator support structure were cracked completely through, including a previously installed repair.Part total time – 14,000+ hours.

Teledyne Continental LTSIO 360EB
Push Rod Damage

These engines were installed on a Piper PA-34-200T Seneca. During an annual inspection, a technician discovered three push rods on the left engine were cracked along their entire length. The technician could not determine the cause of this damage, but changed all 12 push rods on each engine. The high number of operating hours may have been a contributing factor in this failure.Part total time – 3,198 hours.


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