Squawk Box 02/04: Exhausting Work

Exhaust system faults can lead to lots of trouble, from poisoning to engine failure


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


The FAA has issued a reminder of the need to inspect and maintain exhaust system components.The FAA says its review of accident and incident reports show a number of cases in which aircraft have been damaged or occupants have been killed or injured due to failure of some component of the exhaust system. The failures can cause carbon monoxide poisoning, loss of engine power and fire.The most common failure scenarios involve deterioration of the muffler or the heat exchanger that provides cabin heat. A failure of the exhaust components that provide cabin heat can let raw exhaust into the cabin ventilation system. The failure of internal components can block the outflow of exhaust gas, which can lead to partial or complete loss of engine power. If the components are loose, the problem may be intermittent.Examine your exhaust system routinely. Be familiar with the configuration of your system and the pieces that may fail. Inspect with a flashlight, mirror, and an object for probing the internal security of the baffles.Leakage will show as a flat gray or gray-white powdering or a sooty appearance. The deterioration will show as warping, corrosion, pitting or cracking of the components. Check external joints and clamps for misalignment, wear and security. When examining internal components, look for deposits from coking and carbonization. They can create hot spots that can deform a piece or lead to failure. Look for erosion or abnormal wear any place where bends induce the exhaust gas flow to change directions.Satisfy yourself that all bracing, supports and support structures are secure and have the appropriate hardware, including safety wire or self-locking design.

Beech 33 Bonanza
Leaking Fuel Manifold Valve

During a routine inspection, the manifold valve was found to be leaking fuel through the air vent.The problem apparently was traced to the internal failure of the diaphragm.

Cessna 177RG Cardinal
Rod Failure

The No. 2 cylinder connecting rod failed at the crankshaft due to oil starvation of the rod bearing.The problem may have been due to the oil quick drain valve opening during flight.

Cessna 310
Rudder Attach Rivets

The rivets that attach the rudder torque tube to the bellcrank adapter plate were found to be loose.The defect allowed the rudder to deflect as much as five degrees from its proper position.

Cessna 337 Skymaster
Broken Turbocharger Clamp

The turbo exhaust stack retainer clamp on the front engine fractured and the exhaust stack fell off the aircraft on takeoff.Inspection revealed the clamp may have been cracked for some time but the crack was not detected during routine inspections.

Cirrus SR22
False ELT Activation

When transmitting from the No. 2 Garmin GNS 430 nav/comm., the ELT became activated.Inspection revealed the No. 2 comm antenna is mounted directly beneath the ELT location.

Piper PA-28-140 Cherokee
Cracked Seat Frames

The seats were being prepared for reupholstering when the frames of both seats were found to be severely cracked.Cracks approximately 270 to 320 degrees around were found on welds at the support brackets connecting the upper tubulars of the seat frame. The front brackets on the right seat were in imminent danger of breakage.

Piper PA-28-161 Warrior
Landing Gear Cracks

While investigating an oleo fluid leak, the technician found three 0.25-inch cracks running horizontally across the outboard facing area of the left main gear strut tube. The cracks were located 7 to 9 inches up from the base and were visible only when the aircraft was on jacks. The strut tube contained fluid, suggesting the cracks had been present for some time.

Piper PA-32R-301T Saratoga
Leaking Turbo Scavenge Drive

Oil was found seeping from the turbo scavenge drive assembly.The leak appeared to be at the seam where the two halves of the drive assembly meet. This pump was replaced 22.1 hours prior to this incident for the same failure. The drive was replaced again by another of the same type.

Inspection Alert: Tiger Elevators
The FAA has issued a Special Airworthiness Information Bulletin affecting Tiger Aircraft and American General AA-5A, AA-5B and AG-5B airplanes that may have a problem with the horizontal stabilizer forward spar carry-though support structure.During an inspection, a technician found the structure cracked and deformed in all four corners and at a point adjacent to the right side attachment hole. The FAA has received similar reports following hard landings, tail strikes and impact with stationary objects, as well as during accident investigations.


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