Beechcraft S35 N8820M

Summary

On 30 April 2007 at about 21:43 local time, a Beechcraft S35 registered N8820M was involved in an accident near Brookfield, Missouri, 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 April 2007 at 21:43

Classification

Accident

Location

Brookfield, Missouri, United States

Coordinates

Not recorded

Aircraft

Beechcraft S35

Registration

N8820M

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Raymond → Fort Dodge

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CHI07LA127

Nobody was injured.

Improper maintenance by maintenance personnel by not properly torquing cylinder thru-bolts. The loose stud nuts which resulted in the separation of the cylinder and the crop and ditch were factors.

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

Read the full NTSB narrative

he pilot reported that the engine was "operating normally" as he was flying at 6,500 feet mean sea level when the "engine blew up." He elected to execute a gear up forced landing to a corn field about two miles from the airport, but the airplane impacted a ditch during the emergency landing. The engine teardown inspection revealed a hole in the crankcase approximately 3 inches by 3 inches above the number 4 cylinder, which included the 11 and 1 o'clock deck studs. The number 4 cylinder had separated from the crankcase and the number 4 connecting rod was not attached to the number 4 crankshaft pin. The number 4 connecting rod and rod cap exhibited signatures that were consistent with an overload event that deformed and/or sheared the threads on the nuts and bolts. Cylinder number 4 deck stud nuts 6, 7, and 8 were reported missing from the engine at the accident scene, and subsequently found inside the engine cowling of the aircraft. Cylinder number 4 deck studs 6, 7, and 8 were securely attached to the engine crankcase and the threads were clean and undamaged. The 2 o'clock cylinder deck stud was fractured and missing. The remaining deck studs and thru-bolts all exhibited ductile fractures indicative of tensile overload. The other five cylinders' thru-bolt and deck stud break-away torque measurements were recorded for each thru-bolt and deck stud. The inspection revealed that numerous thru-bolts and studs had break-away torque values that did not comply with the manufacturer's limitations. The aircraft engine's logbook indicated that the engine received an annual maintenance inspection on February 16, 2005. The engine logbook entry stated, "Removed and overhauled all 6 cylinders. Installed new rings, ground valves, cleaned and gapped spark plugs." The tach time indicated 5380.5 hours at the time of the annual inspection. At the time of the accident, the tach time was 5,662.24 hours, 281.74 hours since the cylinders had been replaced.

Quoted verbatim from the NTSB record.