More Lycoming Woes

Crankshaft problems may plague some new and recently overhauled engines


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


Textron Lycoming engines have come under scrutiny again, this time for crankshaft counterweight pilot holes that were out of round, resulting in the possible failure of the crankshaft counterweight bushings or counterweight ears.

The FAA has issued a Special Airworthiness Information Bulletin to help operators identify abnormal crankshafts and prevent premature engine failure.

Lycoming manufactured an unknown number of nonconforming crankshafts, and five have failed in the last three years. Those failures occurred between 88 and 517 hours time in service and manifested themselves as engine failure, power fluctuation, metal in the oil filter and loss of oil pressure. Although the exact cause of failure has not been determined, it is suspected that out-of-round (elongated) counterweight bushing pilot holes in combination with below minimum crankshaft counterweight ear edge distance may contribute to the failure. An elongated hole allows the bushing to work loose or wear to the point of breakage, and may eventually start a fatigue crack in the surrounding metal.

Lycoming estimates that about 2,700 engines were manufactured, overhauled or remanufactured during the period in which the problem was present. The company has corrected its manufacturing process, and the FAA is monitoring crankshaft failures to determine if an AD is required.

To detect problems, the FAA recommends regular oil filter inspection and oil analysis to find pilot hole and bushing wear on engines. For further information, see Lycomings SB 408C and service instructions 1142B and 1152A.

Beech C55 Baron
Landing Gear Anomaly

During a landing approach, the pilot selected the landing gear switch to the down-and-locked position. The landing gear failed to extend normally. The pilot extended the landing gear manually and made a safe landing.A technician found the landing gear selector switch would not complete the electrical circuit for landing gear extension. He removed the switch and found it extremely dirty and corroded. He cleaned and reinstalled the switch and the gear worked normally. The technician then replaced the switch.

Beech B100 King Air
Wing Attachment Defect

While complying with the manu-facturers requirement for a 5-year wing bolt inspection, the technician discovered collateral damage on the wing attachment hardware. Two wing attachment fittings were damaged.The damage was caused by improper installation of the lower forward wing attachment hardware. The washers were installed backward, which deformed the wing fittings and compromised the aircrafts structural integrity.

Beech 300 Super King Air
Windshield Failure

During flight, the inner pane of the pilots windshield shattered.The failure occurred when the aircraft was at flight level 330, the outside air temperature was -41C, the cabin differential pressure was approximately 6.5 pounds per square inch, and the windshield heat had been on for approximately 90 minutes.The windshield was approximately 3 years old.Part total time – 564 hours.

Bellanca 17-30A Super Viking
Runway Departure Accidents

An Aviation Safety Inspector in Houston has concluded that there may be a ground directional controllability problem with this aircraft, and that other airplanes might be similarly affected. In several incidents and accidents, the nose landing gear apparently was not centered on landing, causing the nose gear to fail and leading to the loss of control.Although AD 96-18-07 and the manufacturers Service Letter B-107 address nose landing gear failure and loss of ground directional control, operators should be aware of other operating characteristics of the airplane. If the pilot does not apply positive pressure to both rudder pedals during landing, the nosewheel may remain at the angle of the last rudder input. This point can be demonstrated by placing the aircraft on jacks, then without positive pressure on the rudder pedals, the nosewheel can be turned freely by hand to any position within the travel limits without movement of the rudder pedals. With positive equal pressure on both rudder pedals, the nosewheel should be centered.

Cessna TU206G Turbo Stationair
Heat Exchanger Crack

During an inspection, a heat exchanger installed in accordance with STC SA5010 and SE5009NM was discovered to have broken studs. The heat exchanger body, to which the studs were welded, cracked at the base of the studs and eventually broke. These cracks allowed engine exhaust gases to enter the cabin.Part total time – 296 hours.

Diamond DA20-C1
Engine Starter Drive Failure

The pilot reported noticing a significant drop in engine oil pressure during flight. This aircraft was equipped with a Continental IO240-B engine.The oil filter contained several large pieces of steel and aluminum, which were traced to the starter drive gear and the accessory drive gears. All of these gears were missing teeth and severely damaged. Since the operating time was relatively short, the likely conclusion is that at least one of the drive gears was defective prior to installation. Metal contamination in the oil system destroyed the engine.Part total time – 16 hours.

Piper PA-23-250 Aztec
Blown Actuator Seal

When the pilot tried to lower the landing gear, he did not get a green down-and-locked indication. The pilot recycled the gear several times but could not get a safe indication. He tried to lower the gear manually but was not successful. Then he tried to pump the gear down while holding negative gs and the green light illuminated.After a safe landing, a technician inspected the aircraft and discovered the left main landing gears retraction cylinder had blown a seal and allowed the systems fluid to leak out under pressure.

Piper PA-28-161 Warrior
Propeller Spinner Crack

During a scheduled inspection, the technician found a crack on the propeller spinner bulkhead.The crack radiated from a spinner mount screw nut plate rivet, traveled outboard to the edge of the spinner bulkhead and inboard toward the propeller mount bolt holes. One spinner screw washer exhibited severe deterioration and may have caused the crack. Due to the severity of the crack, the technician replaced the bulkhead. Part total time – 9,277 hours.

Piper PA-32R-300 Lance
Nose Gear Failure

The nose landing gear extended in flight without being commanded.The technician discovered the rod-end bearing installed on the nose gear actuator cylinder had broken and allowed the nose gear to free fall to the down-and-locked position. The broken rod-end displayed evidence of a pre-existing crack. Detecting a crack at this location would require disassembling the rod-end from the nose gear downlock mechanism.

Piper PA-44-180 Seminole
Jammed Flight Control

While conducting a preflight inspection, the pilot noticed the elevator was jammed in the nose-down position.A technician discovered a large screwdriver wedged in the flight controls under the cockpit floorboard. Considerable disassembly was required to remove the screwdriver.The screwdriver apparently had been left in the aircraft during a recent inspection and had migrated to the spot where it was found wedged.Part total time – 2,909 hours.


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