The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.
An FAA certified repair station received a Janitrol cabin heater combustion head in exchange for a new part purchased by a customer. The trade-in combustion head had a hole approximately 0.4375 inches in diameter burned through it and the entire part was severely corroded.
Clearly cabin heaters are operated with minimal maintenance until they fail. A pressure decay test of this unit would have made its deficiencies obvious.
Cabin heaters are neglected during the summer, then expected to perform perfectly during the first cold snap. However, cabin heaters that fail can cause fire, inject smoke into the cockpit, produce carbon monoxide, and induce electrical system failures and fuel leaks.
The FAA Service Difficulty Reporting System database contains 241 reports related to heater system failures. Most of the reported failures occurred during the past six years. These failures involved all combustion makes and models of heaters approved for use in general aviation aircraft, and the reported defects covered the entire range of possibilities.
Periodic inspection of the units is essential for safe operation. And the best time to make sure cabin heaters work is before you need them in flight.
Beech A-36 Bonanza
Wing Flap System Failure
During a landing approach, the pilot set the wing flaps to the 14-degree position, and the flaps ran to the full down position and could not be retracted. The technician discovered the 14-degree limit switch was defective, which allowed the flap motor to drive the flaps all the way down. The motor continued to run the flaps past the down stop. The motor, wiring, and relay were overheated and failed without opening the circuit breaker.Time since part overhaul – 847 hours.
Cessna 172S Skyhawk
Poor Engine Performance
The owner complained that engine performance was deteriorating.The technician cleaned the fuel servo and the injectors and conducted another engine run. Performance was slightly improved, but the engine still backfired between 1,300 and 1,500 RPM. He discovered a small piece of lint blocking part of the fuel distribution valve. After removing the lint, engine performance returned to normal.The contamination may have originated at the time of manufacture.Part total time – 666 hours.
Cessna 172S Skyhawk
Defective Seat Position Mechanism
After a flight, the pilot reported he was not able to reposition his seat.The technician discovered the lock control was broken, which prevented the seat locking pins from retracting. This was the second failure of the seat locking mechanism since the aircraft was new. Also, the copilots seat locking mechanism on this aircraft had broken twice in the past.Part total time – 431 hours.
Cessna 172S Skyhawk
Electrical Component Anomalies
The pilot reported the No. 1 nav/comm was intermittent and the transponder was inoperative.A technician bench-checked, repaired and reinstalled the components. After the next flight, the pilot reported the No. 2 nav/comm lost electrical power intermittently and the intercom did not work.The technician eventually found the audio panel communications selector was inoperative. He discovered four loose screws on the avionics bus bar caused these electrical system anomalies. There was evidence of severe electrical arcing adjacent to each of the four screws. The loose screws were used to attach the autopilot, GPS and nav/comm 1 and 2 circuit breakers to the bus bar. There had been no electrical system installations or maintenance performed on the avionics since the aircraft was new. Aircraft total time – 967 hours.
Flight Control Binding
While preparing for takeoff, the pilot checked the flight controls for proper deflection and found the elevator could not be selected nose-down using normal control pressure. A technician found the elevator control was binding in the pitch trim cartridge assembly due to a foreign object intruding into the pitch trim cartridge. He discovered a single cotter pin tailing entered through the cutout opening for the pitch trim cartridge.Part total time – 1,196 hours.
Piper PA-23-250 Aztec
Defective Wheel Assembly
As the pilot was taxiing for takeoff, he noticed the right brake was grabbing. He stopped the aircraft and found a bulge on the inside of the right wheel half. While taxiing to maintenance, the wheel assembly failed.A technician discovered an 8-inch piece of the wheel assembly bead was broken. The pilot said a rather hard landing had been made during the previous flight. The technician recommended that pilots avoid hard landings whenever possible. Part total time – 3,180 hours.
Piper PA-28 Arrow and Archer
A technician reported an ongoing problem with Arrows and Archers equipped with air-conditioning. The installation has a repetitive security problem.The forward left starter attachment bolt, which also secures the alternator attachment bracket, is commonly found with the case threads stripped. Technicians frequently use helicoils to correct this problem, but they dont last much longer than the original threads. The submitter suggested the manufacturer incorporate a milled seat in the case to accommodate a bolt head and allow the use of a nut and lock washer.
Piper PA-32R-300 Lance
During an engine runup at 2,000 RPM, the pilot noticed a 250 RPM drop on each magneto. The engine operation was very rough when operating on each magneto individually.A technician found a broken shaft on both the left and right Slick magnetos. Both rotor shafts were broken at the base of the shaft slot. Part total time – 292 and 458 hours.
Piper PA-44-180 Seminole
Landing Gear Defect
The pilot reported the landing gear would not extend normally.A technician found the emergency gear extension valve was leaking severely, and the hydraulic system fluid quantity was depleted. The hydraulic system powerpack, which was not being supplied with hydraulic fluid, failed.The emergency gear extension valve, located in the nose compartment just below the heater, sprayed hydraulic fluid all around the compartment, creating a fire hazard.An O-ring seal in the extension valve apparently failed. The short time in service indicates the seal was defective or damaged during installation.Part total time – 100 hours.
Piper PA-46-350P Malibu Mirage
Landing Gear Defect
The pilot lowered the landing gear but the right main gear did not indicate it was locked down. After performing aerial maneuvers designed to lock the gear down and cycling the landing gear several times, he received a down-and-locked indication.The technician found one of the four pawls that lock the right main actuator collar internally was sticking. The technician reported this is a common problem throughout the fleet. Part total time – 1,273 hours.
Teledyne Continental IO-520-C
This engine was installed on the right side of a Beech 58 Baron.The technician discovered the No. 2 cylinder connecting rod was broken loose from the crankshaft and the engine case was broken adjacent to the cylinder attachment. The cylinder separated from the case and was contained by the cowling. The connecting rod penetrated the upper cowling.Apparently one of the connecting rod cap bolts did not have the cotter pin installed. The nut backed off, inducing hammering and transferring the entire load to the remaining bolt. The bolt head was broken and the bolt threads were relatively undamaged compared to the other bolt threads.Part total time – 2,206 hours.
Textron Lycoming O-320-E2A
Idler System Impending Failure
This engine is installed in a Piper, Model PA-28-140 aircraft.While complying with AD 96-09-10, the technician discovered a bolt was broken and the head was missing. The idler system bolt was found between the camshaft and the crankshaft.The bolt failure might have been caused by excessive torque during installation. The manufacturer issued Service Instruction 1310A, which allows upgrading the bolts to 0.3125-inch diameter and safety wire.Part total time – 5,214 hours.
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