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Poor wire routing, lack of fuses cause Citabria mag leads to melt


The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts. Click here to view “Airworthiness Directives.”


A sudden and complete engine failure forced the pilot of an American Champion 7GCBC to make an off-airport landing.

Investigators determined the engine failure was caused by melted P-lead wires that were bundled with an overheated wire connecting the master switch and the overvoltage relay. The cause of the overheated wire could not be readily determined, but the affected wire was not protected by a fuse or circuit breaker.

The accident investigators and a team from American Champion found several service difficulties on older model aircraft that had resulted from lack of circuit protection devices. American Champion issued Service Letter 418 in January, titled Electrical System Update.

The SL contains inspection and conversion information to ensure circuit protection devices are installed on the battery bus, the alternator, the power to the alternator regulator, and the overvoltage circuitry.

Current American Champion aircraft models incorporate an inline fuse which protects the wire supplying power to the voltage regulator and the overvoltage circuitry.

American General AA5B Tiger
Alternator Failure

The alternator failed and the pilot landed safely. The alternator had recently been overhauled.The technician found evidence that the brushes were replaced during the previous overhaul, but one of the brushes was completely worn out and the other was worn approximately 50 percent. The wear rate seemed very excessive, especially in consideration of the uneven wear, which suggests a large variation in brush quality.Part total time – 672 hours.

Beech C24R Sierra
Landing Gear Failure

While making an approach for landing, the pilot could not lower the left main landing gear. All efforts to extend the left main gear failed, and the pilot made a gear-up landing.The technician found the left main gear up-lock would not release. He used a pry bar and considerable effort to release the up-lock and the gear fell to the down-and-locked position. He found the up-lock shaft and the cylinder head through which the shaft runs severely corroded. This caused the up-lock cylinder to seize.Part total time – 2,323 hours.

Bellanca 17-31A Super Viking
Induction Air Obstruction

The pilot reported the aircraft lost engine power while climbing after takeoff. He was able to maintain control of the aircraft and land safely.The technician found the engine alternate air door failed at the hinge. This failure allowed the alternate air door to separate, lodge in the induction system and partially obstruct airflow to the engine. Part total time – 600 hours.

Cessna 172R Skyhawk
Defective Nose Steering

After a flight, the pilot reported the nose steering system was very poor, causing the aircraft to depart the runway.The technician found the left and right steering bungees weak. He conducted a pull test on the steering bungees and found actuation began between 20 and 25 pounds. In accordance with the manufacturers technical data, new bungee units should begin actuation between 60 and 65 pounds.Part total time – 440 hours.

Cessna 172S Skyhawk
Firewall Crack

During a scheduled inspection, the technician found a -inch crack in the firewall at the lower cowling mount adjacent to the battery box. Cessna Service Bulletin (SB) 98-53-02 pertains to this subject but only applies to 172R models.The FAA Service Difficulty Reporting data base contains 11 additional similar reports for firewall cracks in the same location. These cracks developed between 199 and 489 hours of operation.Part total time – 559 hours.

Cessna A185F Skywagon
Tailwheel Bushings

During an inspection, the technician found the tailwheel bushings severely worn, extruded, and cracked.The bushings had been recently obtained new from Cessna and the technician speculated they were made of inferior material. This was the second set of defective bushings he had found within a weeks time.Part total time – 40 hours.

Cessna TU206A Stationair
Engine Oil in the Cockpit

During a flight, the pilot noticed the odor of engine oil in the cockpit and observed oil on the floor in the area of the rudder pedals. The engine oil pressure indication went to zero and the pilot made an immediate and safe landing.A technician found approximately 3 quarts of engine oil on the cockpit floor. The engine oil pressure indicator line, located behind the instrument panel, was ruptured because of severe corrosion.Part total time – 4,258 hours.

Cessna 310Q
Tip Tank Leak

While conducting a scheduled inspection, the technician turned on the strobe lights and immediately heard a loud explosion on the left wing. He determined the explosion was caused by the strobe light igniting fuel in the tank. The light is attached to a bracket that is spot welded to the tip tank access panel. Fuel fumes were present, but there was no sign of a leak. The technician flexed the navigation/strobe light bracket and fuel began to weep from the bracket upper attachment leg spot weld. The same defect was found on the right tip tank. AD 76-08-02, Revision 2, and Cessna Service Letter ME75-6 pertain to this subject. However, these documents do not address the cracked or broken light bracket spot welds found in this case. Also, this particular navigation/strobe light installation is excepted from the requirements of AD 76-08-02 and SL ME75-6 by the Applicability statement.Aircraft total time – 10,544 hours.

Piper PA-24-250 Comanche
Defective Wing Attachments

During an annual inspection, the inspector found sheared rivets at both rear wing attachment fittings.The technician discovered all the rivets on the right side at fuselage station 136 were sheared. These rivets are used to attach the plate, fitting assembly, and doubler. There was evidence of extensive movement between the plate and fitting assembly, which caused an associated angle to break. The damage on the left side was much the same, although slightly less severe. Two of the rivets were still intact, and the angle was cracked but not broken.

Piper PA-28-181 Archer
Electrical System Failure

During a flight, the pilot noticed several high amperage spikes followed by loss of output from the alternator.A technician found the alternator, voltage regulator and the overvoltage relay were all damaged. While conducting a bench check on the alternator, he discovered the field terminal lug was arcing to the tip of the rear cooling fan. Abrasions found on all the cooling fan tips indicated a continuous arcing. He determined the arcing damaged the voltage regulator and the overvoltage relay.Part time since overhaul – 53 hours.

Piper PA-46-350P Malibu Mirage
Wing Flap Binding

During a scheduled inspection, the technician discovered both wing flaps binding. The binding occurred while extending from full up to approximately 5 degrees down.While investigating, the technician found the wrong length push rod was installed as the inboard flap actuation push rod but he could not determine the origin of the push rod or when it was installed.Part total time – 28 hours.

Teledyne Continental/Bendix Magnetos
Defective Contact Assemblies

During an engine run-up prior to takeoff, the pilot noticed an excessive RPM drop while checking the magnetos. The technician discovered the cam follower on the magneto contact assembly was misaligned. Also, one of the two rivets holding the cam follower to the contact assembly was missing, and the other rivet was loose. The contact assembly was an FAA/PMA approved part.Since the original report in September 2000, this repair station has found loose rivets on 12 additional contact assemblies. The suspect contact points are easily identified by the AB prefix preceding the part number. These failures occurred between 50 and 400 operating hours. The rivets of one contact assembly were found loose during a receiving inspection.

Textron Lycoming
Oil Pump AD

The FAA issued AD 96-09-10 in 1996 that superseded AD 81-18-04, Revision 2. Both documents concern replacement of the aluminum oil pump impeller and shaft assembly with a hardened steel impeller and shaft assembly.AD 96-09-10, paragraph (c), requires replacement of these parts at the next engine overhaul (not to exceed the Time Between Overhaul (TBO)) for each particular engine model listed in Service Instruction 1009AJ, at the next oil pump removal, or 5 years after the effective date of the AD whichever occurs first.

However, the requirements of AD 96-09-10 do not apply to some Textron Lycoming aluminum oil pump impellers. These earlier style oil pumps incorporate an aluminum impeller with a fixed shaft secured with a cotter pin and a two-piece oil pump housing. The nonapplicability of the impeller part number mentioned above is explained in Amendment 39-9586 of which AD 96-09-10 is a part. Any questions regarding this disparity should be addressed to the contact information listed in the last paragraph of AD 96-09-10.

The 5-year time limit expires July 15, 2001. Therefore, during engine inspections and maintenance, the technician should verify compliance with AD 96-09-10 has been accomplished prior to expiration of the time limit.


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