Wasted Gates

Inspecting turbo ops requires only a simple flight test


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


A certificated air carrier recently reported a reduction in engine power that was later traced to a stuck turbocharger wastegate. When the incident was reported, the FAA issued Safety Recommendation 99.397, which prompted the manufacturer to issue a service bulletin describing how carriers should inspect the wastegates.

While Part 91 operators are not required to meet the requirements of the SB, the FAA encourages all operators of turbocharged aircraft to conduct at least annually a simple test. While operating the aircraft at approximately 17,000 feet, the operator should verify that the manifold pressure can be increased as engine RPM is increased. This test is referred to and is equivalent to a turbocharger bootstrap check in accordance with the procedures outlined in applicable aircraft maintenance manuals.

Many aircraft were modified to accept turbocharged engines prior to when instructions for continued airworthiness were required. Early turbocharged aircraft should be capable of being evaluated for proper turbocharger operation by using this simple test. Automatic or manual wastegate operation should be verifiable at altitudes below 17,000 feet.

Beech C-24R Sierra
Horizontal Stabilizer Damage

During a scheduled inspection, the technician found cracks in the horizontal stabilizer front spar.After removing the spar the technician found numerous cracks at the upper radius of the hinge cutout slot. When the technician received a new spar, he discovered a crack approximately 0.375 inch long at the same location of the hinge cutout slot. This manufacturing defect may have been introduced when the hinge cutout slot was created.The FAA Service Difficult Reporting Program data base contains four additional entries concerning cracks in the horizontal stabilizer hinge area of the spar.Part total time – 0 hours.

Beech N35 Bonanza
Engine Compartment Fire

During takeoff, the pilot smelled a suspicious odor he thought was from new paint. The smell dissipated when he cycled the landing gear. The pilot noticed the CHTs were higher than normal. During a precautionary landing, he saw flames coming from the engine cowling.Maintenance personnel determined the fire resulted from a split in the fuel hose from the fuel control unit to the firewall. This hose supplies pressure to the fuel pressure indicator. Fuel sprayed onto the muffler and splashed into the nosewheel well keel area. When the cowl flaps opened, the intensity of the flame melted the nose steering rod in half.

Beech Travel Air
Uncommanded Propeller Feather

The pilot experienced an uncom-manded right propeller feathering during flight. Low oil pressure allowed the propeller to go toward low pitch and eventually into feather. The pilot made a safe single-engine landing.A technician investigated and found a broken spring in the oil pressure relief valve. The technician installed a new spring, and an operational test proved the problem was solved.Part time since overhaul – 1,475 hours.

Beech 200 King Air
Empennage Structural Defect

After removing the vertical stabilizer leading edge to accommodate an inspection, the technician discovered the left horizontal stabilizer attachment fitting was cracked. The fitting is used to attach the horizontal stabilizer to the top of the vertical stabilizer front spar. It appeared the crack originated from the bottom huck bolt hole, migrated upward and spread out in four directions.Part total time – 7,972 hours.

Cessna 182R Skylane
Defective Wing Flap Actuator

A maintenance technician installed a new wing flap actuator. During an operational test, the flap actuator ran in reverse of the input command.The technician checked the installation and determined the new actuator motor wire codes were the same as the old actuator and were connected properly. He concluded the new flap actuator was not wired correctly when it was assembled. As a test, the technician reversed the electrical connector pins, and the actuator operated properly.Part total time – 0 hours.

Cessna 300 and 400 Series
Fuel Selector Valve Operation

The FAA has received several reports concerning the wing-mounted, cable-controlled fuel selector valves on Cessna 300/400 series aircraft that indicate the fuel selector valves are very difficult to operate and do not properly stop the flow of fuel to the engines when positioned to off. The FAA has advised Cessna that additional service information should be developed to assist field maintenance personnel with overhaul and troubleshooting these rather complicated devices.Field personnel are encouraged to contact the Cessna Service Department when experiencing service problems and to occasionally cycle the valves to remove any contamination may cause the valves to leak or become stiff.

Cessna 414A Chancellor
Landing Gear Malfunction

The pilot reported the right main landing gear light did not illuminate immediately when the gear was selected to the down position after cruising in subzero conditions. He heard a banging noise before the light illuminated. After landing, the aircraft was parked for several hours with the temperature still below freezing. During a preflight inspection, the right gear light again would not illuminate, and the gear warning light was on.Maintenance personnel moved the aircraft into a warmer hangar and the gear operated normally. A technician discovered the right gear actuator contained approximately 1/3 cup of water in the hydraulic fluid. He determined the hydraulic system reservoir service port outside the baggage compartment was missing an O-ring seal, which allowed water to enter the system and freeze.Part total time – 6,219 hours.

Cessna 421C Golden Eagle
Engine Mount Beam Cracks

During an annual inspection, the technician discovered a severe crack in the left engine mount beam and the same discrepancy in the right engine mount beam.The Service Difficulty Reporting System database contains seven additional entries involving structural defects associated with the engine mount beam assembly.Part total time – 3,980 hours.

Piper PA-18 Super Cub
Structural Damage

An FAA-certified repair facility re-covered six aircraft. Of the six aircraft, five displayed severe corrosion damage on the top fuselage longeron. In each case, the corrosion damage was located under the sliding window channel on the left side. Due to this corrosion, the longeron was replaced on each aircraft. The mechanic speculated that the accumulation and retention of moisture under the window channel caused the corrosion damage. He suggested technicians remove the felt window channel material and give this suspect area a close examination during inspections.

Piper PA-28-180 Cherokee
Rudder Control System Free Play

During an annual inspection, the technician discovered excessive free play associated with the rudder pedals.After investigating further, the technician found the rudder center crossbar support assembly was cracked. The rudder crossbar support cracks were located in the bend radii along the lower edge. Excessive rudder pedal input, metal fatigue, and mild corrosion may have caused this damage.Part total time – 3,497 hours.

Piper PA-34-200T Seneca
Nose Gear Failure

The nose landing gear failed to extend during a landing approach and the pilot landed with the nose gear retracted. A maintenance technician discovered the nose gear centering assembly attachment clevis bolt had contacted the aft tube assembly of the nose gear door actuation mechanism. This defect prevented the nose gear from extending and was evidenced by marks on the tube assembly. The marks indicated this condition had existed for some time prior to this occurrence.AD 92-13-05 and Piper SB 893 pertain to this subject. This aircraft was in compliance with the AD and the SB.Part total time – 456 hours.


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