Kitfox SERIES V N53562

Summary

On 23 July 2024 at about 15:45 local time, a Kitfox SERIES V registered N53562 was involved in an accident near La Grande, Oregon, 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

23 July 2024 at 15:45

Classification

Accident

Location

La Grande, Oregon, United States

Nearest airport

La Grande/Union County Airport (KLGD)

Coordinates

45.3094, -118.0198

Aircraft

Kitfox SERIES V

Registration

N53562

Category

Airplane

Year built

2000

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

La Grande → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR24LA260

Nobody was injured.

Separation of the propeller blades from progressive damage at the blade roots due to overtightening of the hub bolts.

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

Read the full NTSB narrative

The pilot reported that shortly after takeoff he heard a loud, violent bang that shook the airplane. He could see that the propeller was not moving and subsequently made a forced landing to a nearby beet field. After the airplane came to rest, the pilot observed that two of the three propeller blades had separated from the propeller hub. He later found one of the missing propeller blades about 3,000 ft from the main wreckage; the remaining propeller blade was not located. Examination of the propeller hub, the two recovered blades, and the blade roots revealed that all three blades had fractured at the retention grooves near the blade roots. Examination of the fracture surfaces revealed thumbnail cracks extending from the blades’ surfaces inward, consistent with fatigue failure. The examination evaluated whether the blades were installed in accordance with the propeller manufacturer’s instructions. The instructions called for the hub bolts to be torqued to between 75 and 100 in-lbs. The airplane’s logbook did not have records of the tightening torque used on the hub assembly. Although the hub bolt torque value was measured at 32 in-lbs., the measured torque was likely affected by the absence of two of the three propeller blade root cores. The gap between the two halves of the hub was measured between 0.016 and 0.022 inches, which is less than the manufacturer’s design specification of 0.030 inches, and consistent with excessive clamping force applied by overtightening of the hub bolts. All three blade retention bores in the hub showed a black residue, especially at the outboard end of each bore near the hub split line. This appeared to be material transfer from the blades’ polymer caps to the hub. The measured widths of the impressions on the caps left by the hub split line were also less than 0.030 inches, again consistent with overtightening of the hub bolts. The overtightened bolts would have applied excess compressive stress to the blade roots, resulting in damage that progressed to fatigue failure. Review of available maintenance records showed no evidence of propeller overhaul consistent with the manufacturer’s recommended time between overhauls for their propellers.

Quoted verbatim from the NTSB record.