The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts. Click here to view “Inspection Call.”
The FAA has issued a Special Airworthiness Information Bulletin to operators of Piper Malibu and Malibu Mirage models regarding the possibility of a deformation of a fuselage frame assembly.One Mirage was found with a deformed frame assembly at fuselage station 311.40, which is located in the aft fuselage tail cone. The deformation was on the left side, at the attach fitting for the front spar of the horizontal stabilizer.The damage may have been caused by a right side fitting being used on the left side, with the parts forced together by the attachment bolt. The FAA has not determined how the condition occurred. There have been no other reports of a similar problem on other airplanes.The fittings are part of the 100-hour inspection, according to Pipers maintenance manuals, and there is also a Piper service bulletin that specifies inspecting the fittings for corrosion or paint flaking on some airplanes. The FAA encourages operators to make visual inspection of the area, using a straight-edge and flashlight, to determine if the fitting is deformed. The ELT should be removed to permit proper inspection.
Beech F33A Bonanza
Inoperative Vacuum Pump Motor
The pilot reported the air pressure delivered by the standby vacuum pump was insufficient.The technician found the vacuum pump drive motor had failed. The failure underscores the need to check backup systems prior to flight for proper operation.
Beech 58P Baron
Damaged Engine Mount Truss
During a scheduled inspection, the technician noticed that the exhaust heat shield forward of the turbo compressor had chafed through the engine-mount truss.The chafed area was approximately 3/16 inches by 5/16 inches. The technician said the damage occurred when the heat shield mount broke and contacted the truss.A search of the FAA Service Difficulty Reporting Program database revealed three additional reports with like failures.
Corroded Oil Pressure Line
During a flight, the pilot noted a loss of oil pressure on the panel-mounted indicator. A technician found the line to the oil pressure indicator was worn completely through, probably due to corrosion.
The operator noted that oil consumption increased dramatically when the engine had 137 hours since overhaul.Technicians found the spark plugs in the No. 1 and No. 3 cylinders were oil-soaked. All four cylinders were removed. The rings in cylinders 1 and 3 were broken and the cylinder walls were badly worn in all four cylinders. The operator noted that it was the third such finding in its fleet of airplanes within a two-week period. All of the cylinders on all of the affected models were manufactured at about the same time, leading to the possibility that the problem stems from a bad batch of cylinders.
Improper Propeller Mounting Bolts
The technician reported the propeller mounting bolts on the new Cessna Model 172 seemed to be too short.The bolts did not extend through the crankshaft pressed threaded bushing. Usually the threads will extend two to three threads through the bushing. The FAA Service Difficulty Reporting Program database revealed four additional reports citing insufficient length of propeller mounting bolts on Cessna models 150 and 172.
Debonded Wire Harness Mounts
During a scheduled inspection, technicians noticed four wiring mounts had debonded from their mounting locations.In 172R and 172S models, wiring under the cabin floor is attached with tie wraps to adhesive/backed nylon mounts that are then bonded to the inside of the aircraft skin. When the mounts debonded, the rear-seat intercom wires began chafing on the trim cables. The technician replaced the mounts with adel clamps and secured them with screws and nuts.
GPS Screen Failure
The pilot reported that the screen of the Garmin GNS 530 went blank during an IFR flight. The unit continued to receive and transmit communications.Investigation revealed the high-voltage transformer had failed. The units require 28 volts DC to work, and a transformer is required on aircraft with 14-volt electrical systems.
Worn Trim Wheel Sprockets
The pilot reported the rudder trim system did not seem to be responding to the indicated trim input.Inspection of the system found that the trim wheel sprockets were not shimmed correctly to allow the gear teeth to engage correctly. Two sprockets engage 90 degrees from each other and were barely making contact. The sprockets would slip when trim load was increased, wearing the teeth and reducing the amount of trim load required to make them slip.The installation error may have been a manufacturing defect.
Turbocharger Tailpipe Clamp
The FAA reported a Cessna T210N Turbo Centurion made an emergency landing after descent from a cruise altitude of above 10,000 feet as a result of the pilot initially observing electric and hydraulic system malfunctions and then smelling smoke.Inspection of the airplane on the ground revealed that the engine exhaust tailpipe had separated from the turbocharger. The V-band clamp used to secure the turbocharger to the exhaust tailpipe was still attached to the turbocharger. The self-locking nut that is torqued to secure the V-Band clamp had loosened enough to allow the tailpipe to separate from the turbocharger. It was determined that the self-locking nut was not the correct type. This condition has been suspected when other Cessna turbocharger tailpipe separations have occurred. There are Airworthiness Directives on some Cessna airplane models to insure proper attachment of the turbocharger to the tailpipe but not on the Cessna T210 series.
During a scheduled inspection, the pressurized magneto was disassembled. All of the internal hardware was found corroded.The distributor gear, drive gear and distributor block were found covered in a film and were noticeably softer than new items, possibly as a result of moisture ionization. The aircrafts records confirmed that the magnetos moisture filters had been replaced as scheduled. AD 88-25-04 addresses the problem in an earlier series of magnetos but the AD does not apply to the series in question.
The pilot reported the engine would not run on the left magneto.Inspection revealed that the Woodruff drive key between the drive shaft and the drive coupling was missing.
Cracked Oil Cooler
During a preflight inspection, the pilot detected an oil leak.Technicians traced the leak to the oil cooler and conducted a pressure check. A crack was found in the seam on the top of the cooler. The fault could have been caused by engine vibration or also by a previous mechanic not using a backup wrench when installing oil cooler hoses.
Frayed Aileron Control
During normal maintenance, the technician noted the aileron cables had broken strands.The breaks occurred at the point where the cable met the inboard pulley at the wing root. The pulleys showed no signs of wear and turned freely. The technician surmised the problem was caused by bad cables.
Piper PA-31-350 Chieftain
Elevator Trim Failure
During departure, the elevator trim wheel jammed, and the pilot was unable to free the system. The elevator trim was stuck in a nose-down configuration. He was able to counteract the trim pressure and continue to the nearest airport.The technician discovered the elevator trim jackscrew was bound up at the trim cable drum. After he disconnected the jackscrew from the tab, it functioned correctly. Due to the accumulative wear in the system, the elevator trim tab jackscrew was in excess of the normal limit, which caused it to jam.
Inoperative Low Fuel Light
The operator reported that the low fuel warning system was inoperative. The warning light did not light when the fuel tank was empty.Technicians discovered an improper repair on the wire from the circuit breaker to the system, made by an unknown person at an unknown time. The connector had not been crimped correctly and the wire was severed inside the insulation. The helicopter did not have a press-to-test switch for the annunciator.