Squawk Box 12/03: Beater Heaters

Mechanics and owners still appear to take shortcuts in inspecting Janitrol heaters


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


Once again the Janitrol heaters in Beech Twin Bonanzas, Barons and Travelairs have come under fire for their potential to cause trouble.This time the FAA says it has reports of thermal erosion on the combustion heads of Model S-50 combustion heaters that appear to be due to maintenance people not following recommended maintenance procedures. The lack of proper maintenance is compounded by the fact that some of the heaters are approaching 40 years time in service.The maintenance manual specifies a visual inspection of all fuel and air fittings and the verification of the security of ignition leads and the ignition unit every 100 hours of heater operation. One operator reported inspecting the heaters on three different airplanes and finding nearly identical thermal erosion – a defect that should have been obvious long before if the unit had been inspected properly. Maintenance instructions also call for overhauling the heater every 500 hours of operation or at each engine overhaul.

Defective Hoses
MIL-H-6000 low-pressure hose is used in a variety of general aviation aircraft, including engine oil and fuel hoses, in both pressure and venting configurations. Several recent incidents illustrate the need to periodically examine hoses for condition and integrity.One pilot reported a sudden reduction in power during flight. Subsequent inspection revealed the surface walls of the MIL-H-6000 fuel line between the gascolator and the carburetor had deteriorated to the point of restricting flow through the hose assembly. The exterior of the hose showed no signs of the internal deterioration of the hose.A similar incident occurred during flight that resulted in a forced landing that damaged both a wing and the propeller. Again, a defective hose was found restricting fuel flow to the carburetor.These hoses often have been installed on the aircraft for many years. The hose is exposed to fuel and oil along with vibration and heat that can over a period of time cause to the hose to deteriorate. Hoses that are five years or older may require closer inspection by examining the internal portion of the hose for condition. Replace hoses that show any form of deterioration, flaking or swelling of the rubber material.

Beech A23-24
Incorrect Engine Mounts

During an inspection, the technician noticed that the incorrect engine mounts were fitted.Further investigation revealed the manufacturers illustrated parts catalog included the incorrect part number. The correct information was found in the manufacturers maintenance manual.

Beech 55 Baron
Broken Main Gear Brace Assembly

During landing, the right main gear collapsed, damaging the right flap, wing tip, brake assembly and propeller. Investigation revealed a broken screw allowed the trunion pin to back out. The brace became loose, allowing the down-and-lock catch to unlatch.

Beech 58P Baron
Chafing Exhaust Crossover Tube

During a phase inspection, the technician discovered the left crossover tube was chafing on the engine mount truss. The chafing had progressed about halfway through the thickness of the crossover tube.

Beech A100 King Air
Blocked Fuel Line

During flight, the left engine shut down without the pilot commanding it.After extensive troubleshooting, technicians found that an internal patch on the fuel bladder had come off and blocked the line to the nacelle tank. All of the fuel tanks were inspected and two other tanks were found to have internal patches, which a fuel cell repairer calls common practice. The aircraft operator decided to conduct annual inspections on all internal bladder patches.

Cessna 172R
Door Hinge Pin Sheared

During flight, the passenger door opened when a door hinge pin sheared.Inspection revealed the upper hinge of the right cabin door had sheared completely and the lower hinge was bent. The right cabin door window separated in flight and damaged the fuselage. The lower hinge and adjacent structure was bent and broken. The upper hinge on the left door also showed some wear.

Cessna 172R
Cracked Right Wing Spar

During maintenance on the right fuel tank, the technician found a crack in the aft spar that extended about 1.375 inches along the upper bend radius.

Cessna 177RG Cardinal
Inoperative Stall Warning

During an annual inspection, the stall warning system tested functional, but the system would not operate when the pitot heat was switched on.The technicians determined that the stall systems ground connection was corroded such that the stall system would ground through the pitot heater via the stall warning heater. When the pitot heat was turned on, the stall warning would not ground.

Cessna 180
Rudder Cable Failure

The FAA says it has gotten several reports of rudder cables on the Cessna 182s being caught under the mounting bolt for the elevator control cable pulley at Station 156. Unsuccessful attempts were made to recreate the malfunction by control movement alone, however the FAA notes that the airplane battery and avionics package are both accessed through the same Station 156 panel. It may be possible to inadvertently push the rudder control cable down under the elevator pulley bolt during maintenance.Failure to recheck the rudder control cables rigging following maintenance on the nose wheel steering or rudder trim systems could increase the potential for this to occur. Maintenance Manual procedures call for the cable rigging to be checked following work on these systems.

Cessna 210C
Broken Yoke

As the pilot rotated for takeoff, the control yoke broke at the point where the push-to-talk button was mounted.The yoke was original equipment and 40 years old. The white plastic yoke, covered completely with black plastic, shattered when the yoke broke.

Cessna 310
Cracked Main Gear Torque Tube

During flight, the pilot noted the aircraft seemed slower and was yawing to the left. A fly-by inspection indicated the left main landing gear was down, while the right main and nose landing gears were retracted. The pilot selected the gear-down position, and all three gears indicated down-and-locked. He landed the aircraft without incident.An investigation revealed the left main gear torque tube had cracked at the fork-bolt boss and the crack had progressed around the torque tube in a spiral manner. A search of the FAA Service Difficulty Reporting Program database revealed 15 additional failures of the main landing torque tube on Cessna 300 and 400 series aircraft.

Cirrus SR20
Cracked Door Frame

During an inspection, the technician found the fuselage cracked on both sides at the door frame.The cracks appeared in the area above the side window on both sides, extending about 18 inches.

Cirrus SR22
Improper Firewall Attach Bolts

During an inspection, the technician found the lower engine mount to firewall bolts loose.Upon further investigation, the technician concluded the lower bolts were too long and the grip length was also too long. Both bolts were replaced with the proper size bolts.

Cirrus SR22
Misrouted Parachute Lanyard

During an annual inspection, the technician noted that the lanyard cables that connect the rocket pickup collar to the parachute were misrouted.The technician concluded that the misrouting would have rendered the parachute ineffective. The cables were rerouted according to the manufacturers specifications.

Piper PA-23-250 Aztec
Chafed Hydraulic System

After the aircraft was taxied to the hangar for maintenance, technicians noticed hydraulic fluid on the floor underneath the wing root. Further inspection revealed a lead located about 20 inches aft of the leading edge of the right wing. The location was where the landing gear hydraulic extension line is crossed by the aileron cable. There was insufficient clearance between the cable and the hydraulic line, allowing the cable to chafe through the line.

Piper PA-34-200T Seneca II
Loose Rudder Mast

During an annual inspection, the technician discovered the rudder torque tube attach bolts were loose. A teardown inspection revealed the bolt holes were oversized and elongated.The FAA Service Difficulty Reporting Program database shows seven additional reports of failure of the rudder torque tube on Piper PA-34-200T aircraft.

Socata TB10 Tobago
Corroded Wing Spar

During an inspection, the technician found the right wing spar corroded.The aft lower web of the spar showed exfoliation corrosion in the area adjacent to the main landing gear leg.

Inspection Call: T182 Seat Tracks
The FAA has released a Special Airworthiness Information Bulletin clarifying the applicability of AD 87-20-03 R2, which was written prior to Cessnas reintroduction of the Turbo 182. The AD requires the inspection of the seat locking mechanism of all Cessna T182s. However, the new production models, designated T182Ts, incorporate a different locking mechanism and the AD does not affect the new models.

Inspection Call: Cessna Yoke Corrosion
Cessna and Reims Aviation 172, 180 and 185-series airplanes may be subject to potential failure of the control yoke assembly. The FAA says it has reports of yoke failure due to moisture being trapped in the closed tube section below the pivot point. Internal corrosion can weaken the yoke until it fails under normal control pressures.Cessna has issued a service bulletin providing for the yoke to be removed, inspected and treated for corrosion. Part of the remedy involves drilling an access hole. Depending on the findings, an ultrasonic inspection may be required.After the initial inspection and treatment with a corrosion preventative, Cessna recommends an annual external visual inspection.


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