Klaas Development LANCAIR IV P N541EM

Summary

On 3 September 2014 at about 19:22 local time, a Klaas Development LANCAIR IV P registered N541EM, operated by Empire Equipment LLC, was involved in an accident near Ooltewah, Tennessee, United States. One person was on board and one died. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

3 September 2014 at 19:22

Classification

Accident

Location

Ooltewah, Tennessee, United States

Nearest airport

Collegedale Muni (FGU)

Coordinates

35.0778, -85.0553

Aircraft

Klaas Development LANCAIR IV P

Registration

N541EM

Category

Airplane

Year built

2000

Engines

1

Operator

Empire Equipment LLC

Operating rule

Part 91: General Aviation

Purpose of flight

Business

Phase of flight

Not recorded

Route

Knoxville → Jackson

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA14FA421

1 person died.

The inadequate torque of the propeller mounting bolts and inspection of the propeller, which resulted in the fatigue fracture of the bolts and a subsequent in-flight separation of the propeller assembly.

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

Read the full NTSB narrative

Shortly after departing on a personal cross-country flight and leveling off at the filed cruise altitude, the commercial pilot reported trouble maintaining altitude and descended to a lower altitude. He then reported both engine and instrument problems and requested to divert to a nearby airport. Subsequently, the pilot reported that the engine had lost power, oil was all over the windshield, and that there was no visibility due to the oil. Shortly thereafter, he stated that a forced landing was imminent; the last radar return for the flight was about 2 miles from a nearby airport and in the vicinity of the accident location. On-scene examination of the wreckage revealed that the propeller hub and propeller blades were missing and that oil was noted covering the airplane and windshield fragments. The propeller blades and hub were later located about 8 miles from the accident location. Five of the six propeller mounting bolts were found inside their bores. The sixth bolt was not located. Metallurgical examination determined that the remaining five mounting bolts failed due to reverse bending fatigue. The witness marks on the aft face of the propeller hub were consistent with marks from bolts or bolt fragments while the propeller hub was still partially attached. This would likely occur when the bolt or dowel was still intact before total separation of the propeller assembly. The reverse bending failure of the hub mounting bolts were likely indicative of a loose connection between the hub and the crankshaft. Maintenance records revealed that the propeller was overhauled about 35 flight hours before the accident and was inspected about 15 flight hours before the accident; however, the records did not note, nor were they required to, the torque setting that was achieved. Considering the extensive damage to the propeller flange in conjunction with the limited number of flight hours, it is likely that at least one of the propeller mounting bolts was not torqued sufficiently at the time of installation and gradually loosened during the subsequent flights.

Quoted verbatim from the NTSB record.