Incident Details
On April 27, 2023, at approximately 1400 central daylight time, a Piper J3C-65 airplane, registration N6384H, sustained minor damage during an incident near Romeoville, Illinois. The pilot, who was the sole occupant, reported no injuries. The flight was conducted as a Title 14 CFR Part 91 personal operation.
According to the pilot, the preflight inspection revealed no anomalies. The aircraft departed from runway 09 at Lewis University Airport (LOT). At an altitude of about 650 feet above ground level, the airplane began to shake violently. The pilot reduced the throttle, broadcast an emergency transmission to the LOT air traffic control tower, and executed a 180-degree left turn to return to the departure runway. Approximately halfway through the turn, the pilot shut down the engine, confident that the airplane could safely land. The subsequent landing was uneventful.
Aircraft and Propeller
After exiting the aircraft, the pilot discovered that about 5 inches of the outboard portion of one aluminum propeller blade had separated. The missing blade segment was not recovered. The propeller, a McCauley 1B90/CM7144 fixed-pitch unit, sustained only minor damage, and no other damage was noted to the propeller, engine, or airframe.
Maintenance History
The aircraft had undergone an annual inspection on October 25, 2022, and had accumulated only 0.7 flight hours since that inspection. The propeller was overhauled on January 28, 2015, and installed on the aircraft on August 18, 2015. The total time since new was listed as unknown, and the propeller had accumulated approximately 223 total hours since installation. Maintenance records did not indicate any additional overhaul work since installation. According to McCauley, the propeller required overhaul at 2,000 hours or 72 calendar months, whichever occurred first; however, the FAA does not mandate propeller overhauls for Part 91 operations.
Findings
Postincident examination of the propeller revealed features consistent with fatigue cracking that originated at the midpoint of the cambered face of the blade. The initiation sites displayed corrosion pits similar to those observed elsewhere on the cambered face, which had been present beneath the paint and primer.