Casualties unknown

Airplane Collides with Mountainous Terrain in Instrument Meteorological Conditions (N522T)

Diablo, CA, US

On June 6, 1993, a Piper PA-23-150 (registration N522T) operated by Norman E. Lamantia was involved in an aviation accident near Diablo, CA. Investigators recorded the probable cause as: THE PILOT IN COMMAND'S CONTINUED FLIGHT INTO INSTRUMENT METEOROLOGICAL CONDITIONS, AND THE IMPROPER IN FLIGHT PLANNING AND DECISION MAKING BY THE PILOT. 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

An airplane impacted mountainous terrain in a near wings-level attitude during IMC. Witnesses reported normal engine sounds. No record of pilot obtaining weather briefing; no mechanical failures found. Propellers exhibited chordwise scratches and 'S' bending.

Introduction

An airplane collided with mountainous terrain while flying in instrument meteorological conditions. The aircraft was in a near wings-level attitude at the time of impact.

Details

Witnesses near the accident location reported hearing normal engine sounds as the airplane flew overhead. Investigators found no record of the pilot obtaining a weather briefing prior to departure.

Investigation Findings

Examination of the aircraft wreckage revealed no mechanical failures or malfunctions. Both propellers showed chordwise scratches and 'S' bending, consistent with rotation at impact. The terrain was mountainous, and conditions were instrument meteorological.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X12636. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.