Piper PA-18 N1124

Summary

On 30 August 2019 at about 21:10 local time, a Piper PA-18 registered N1124 was involved in an accident near Fairbanks, Alaska, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

30 August 2019 at 21:10

Classification

Accident

Location

Fairbanks, Alaska, United States

Coordinates

64.8925, -148.3689

Aircraft

Piper PA-18

Registration

N1124

Category

Airplane

Year built

1955

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Fairbanks → Fairbanks

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC19LA048

Nobody was injured.

The inappropriate application of paint underneath the engine cylinder hold-down nuts, which resulted in inadequate torque and the subsequent in-flight separation of the No. 3 cylinder, and resulted in a total loss of engine power.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The commercial pilot reported that while in cruise flight in her float-equipped airplane, the engine began to sound "funny," so she elected to return to her destination airport rather than selecting a suitable nearby lake for landing. About 16 minutes later, the engine lost all power and she conducted an emergency landing to a heavily forested area. The airplane sustained substantial damage to the wings. Examination of the engine revealed that the No. 3 cylinder had separated from the engine's case, but the two No. 3 cylinder hold-down studs were intact and the studs’ threads were in relatively good condition; the other cylinder studs were fractured with fretting present on the engine's case. In addition, paint was chipped and broken around the cylinder hold-down nuts and paint was present inside the cylinder stud holes located on the cylinder's flange. The Lycoming overhaul manual states that "All machined bosses should be masked before painting. Do not paint areas under hold-down nuts where torque is required." Due to the presence of paint inside the cylinder stud holes and broken and chipped paint around the hold-down nuts, it is likely that paint was applied inappropriately under the cylinder hold-down nuts, which would have led to an inaccurate torque reading during assembly, which allowed them to back off over time, resulting in overload failure of the other nuts and separation of the No. 3 cylinder.

Quoted verbatim from the NTSB record.