Prop Shop Chopped

Santa Monica Propeller overhauls may have had improper inspections


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


When auditing a propeller repair station recently, the FAA discovered that certain alignment and inspection procedures had not been accomplished in accordance with the manufacturers propeller overhaul manual procedures.

Although there have been no reports of failures of the propellers, overhauled by Santa Monica Propeller Service from January 1997 to March 1999, the FAA considers it a significant safety risk because a propeller failure can lead to catastrophic loss of aircraft control.

The propellers in question involve both Hartzell and McCauley props. The FAA has issued a Special Airworthiness Information Bulletin that lists the propellers overhauled by the company, but the FAA says the list may not be complete.

The overhauls are suspect because an FAA audit showed that certain required inspections were not being performed according to the overhaul manuals. They include blade face alignment, blade chord and blade thickness checks. The FAA is investigating how serious the problem is and will determine later if an AD is required to correct any deficiencies in the companys work.

The propeller manufacturer can provide the proper specs or the props can be returned to Santa Monica Propeller for inspection.

Beech B90 King Air
Air Conditioning System Inoperative

After returning from a flight, the pilot reported the air conditioner was inoperative.A technician discovered the air conditioner compressor motor ground wire had burned a -inch hole at the point where it attached to a structural beam. Since the upper support for the landing gear drag brace is attached to the beam, this failure could have caused a catastrophic accident. Apparently, the ground wire attachment bolt worked loose and the electrical arcing grounded through the beam.

Cessna 172H Skyhawk
Defective Aileron Control System

The pilot reported he had to hold the control yoke approximately 10 degrees to the left to maintain level flight.The technician was attempting to adjust the aileron cable tension but discovered a broken turnbuckle terminal end.The aileron cable connection was maintained by a single strand of .041-inch safety wire, and the cable tension was loose. It appeared that the terminal end had been broken for some time, and the safety wire had stretched.Aircraft total time – 3,489 hours.

Cessna 172R Skyhawk
Wing Flap

During a scheduled inspection, the technician found the left wing flap trailing edge lower skin cracked.The cracks appeared at each of eight rivets from the inboard end of the flap and extended two feet outboard. The technician speculated this defect was caused by improperly rigged wing flap control cables. The proper flap cable tension is 30 pounds, plus or minus 10. He discovered the cable tension ranged from 10 to 50 pounds.This is a fairly common defect that only occurs on the left flap.Part total time – 96 hours.

Cessna 172R Skyhawk
Wing Flap Well Skin

During a routine inspection, the technician discovered the right wing inboard upper flap well skin cracked. The crack traveled along the inboard trailing edge near the wing root area and extended through a line of rivets. The damage suggests that the sheet metal is not thick enough and the rivets are spaced too far apart to bear the stress imposed on the trailing edge.Part total time – 665 hours.

Cessnas with Lycoming Engines
Exhaust Gas Leakage

The FAA suggests that owners of single-engine Cessnas equipped with Lycoming engines examine the exhaust gaskets. The recommendation follows incidents in which Cessna 182S airplanes that had followed AD 98-01-14 (muffler replacements) suffered from exhaust gases leaking into the cabin. The leak was traced to the exhaust gaskets and a loose muffler shroud. Cessna and the FAA recommend an inspection of the complete exhaust system any time work is performed on the engine exhaust system and that suspect exhaust gaskets be replaced with the Lycoming blow proof gaskets.

Hawker Siddely HS-125-700A
Hydraulic System Leak

While parking the aircraft after a flight, the technician noticed hydraulic fluid running from the rear fuselage.The fluid came from the aft equipment bay. After removing components to gain access to the area, he discovered that two stainless steel hydraulic lines were chafing against each other. One of the high pressure lines (3,000 psi) had a pinhole through the wall thickness. Under pressure, the pinhole sprayed fluid into the aft equipment bay. After he removed the hydraulic lines, he discovered a fuel line had chafed through approximately half of the wall thickness.Aircraft total time – 3,097 hours.

Mooney M20J
Nose Landing Gear

During an inspection, the technician discovered the steering truss bolt hole was elongated.The elongation occurred where the overcenter link is bolted to the truss. The manufacturers specifications for allowable wear at this location are 0.375 to 0.379 inch. The wear measured 0.392 inch. The damage may have been caused by a lack of lubrication and an improperly torqued truss bolt. Part total time – 3,164 hours.

Mooney M20J
Aileron Control Link

During a preflight inspection, the pilot reported that the ailerons felt funny.Investigation revealed that the right aileron traveled past the stop. The technician removed the belly pan to gain access to the flight control system and discovered the right aileron control link tube had broken. The crack was located just outboard of the aileron bellcrank and adjacent to a weld. The defect is addressed by AD 98-24-11.Part total time – 2,687 hours.

Mooney M20R Ovation
Baffle Support Bracket

During an annual inspection, the technician found a broken baffle support bracket under the engines front center section.The technician replaced the baffle support bracket with a factory-supplied replacement part. After inspecting all like aircraft in the fleet, the technician discovered this bracket fails regularly.Part total time – 160 hours.

Piper PA-24-250 Comanche
Stabilator Corrosion

During an annual inspection, the technician had to remove the stabilator torque tube assembly.Both the left and right stabilators were very difficult to remove from the torque tube. The inboard fitting mount bolts were removed from the stabilators and left on the torque tube while the stabilators were removed. After disassembling the torque tube, the technician found severe corrosion. The location of the stabilator torque tube makes proper inspection very difficult which may account for the condition found in this case.Part total time – 3,607 hours.

Piper PA-32R-310T Turbo Saratoga
Landing Gear Hydraulic System Failure

The pilot reported that when the landing gear was selected to the up position, the hydraulic pump ran continuously until it failed. The landing gear fell free to the down-and-locked position, and the pilot made a safe landing.An investigation revealed that the nose landing gear actuator was leaking internally and the left main gear actuator was leaking externally. This combination allowed air to be drawn into the hydraulic system and caused the pump to run continuously. Part total time – 143 hours.

Piper PA-46-350P Malibu Mirage
Turbocharger Air Duct Defect

During a scheduled inspection, the technician removed the engine turbocharger air duct to check the compressor.The air duct internal supporting wire had come loose and protruded into the turbocharger air intake. The duct wire was resting a half-inch from the compressor wheel. The duct and wire are normally secured by a clamp on the outside of the air inlet. Apparently, during a previous installation, the wire dislodged from the duct and found its way inside the turbocharger air inlet. This situation could have resulted in a catastrophic event if the duct support wire had been ingested by the turbocharger compressor during a critical period of flight.Part total time – 1,472 hours.


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