Casualties unknown

Loss of oil pressure forces emergency landing in Iowa crop field (N8527M)

Ottumwa, IA, US

On August 31, 1993, a Beech P35 (registration N8527M) operated by Allen, Darrell W. was involved in an aviation accident near Ottumwa, IA. Investigators recorded the probable cause as: A leak in the oil filter adapter gasket, which caused a loss of oil pressure and necessitated an off-airport landing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-10Data APIEditorial standards

A pilot experienced a loss of oil pressure during cruise flight and was unable to reach the nearest airport in Ottumwa, Iowa, resulting in an off-airport landing in a crop field.

What happened

The aircraft was operating in the cruise phase of flight when it experienced a sudden loss of oil pressure. The pilot initiated an emergency procedure and attempted to divert to an airport located in Ottumwa, Iowa. During the approach planning, the pilot determined that the airplane lacked sufficient altitude or glide performance to reach the airfield. Consequently, the pilot elected to perform an off-airport landing in a nearby crop field.

The investigation

Following the accident, investigators conducted a post-accident examination of the aircraft's engine components. The inspection focused on the lubrication system to determine the root cause of the pressure loss. Examination of the engine revealed that there was a leak in the oil filter adapter gasket. This mechanical failure compromised the integrity of the oil system, leading to the loss of pressure.

Findings

The investigation identified the leak in the oil filter adapter gasket as the primary mechanical failure. The pilot's decision to land in a crop field was a direct result of the inability to reach the intended airport due to the emergency. No further contributing factors were identified beyond the mechanical defect.

Probable cause

A leak in the oil filter adapter gasket, which caused a loss of oil pressure and necessitated an off-airport landing.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X13125. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.