Casualties unknown

Border Patrol Pilot Crashes During Ridge Crossing with High Density Altitude (N91187)

Van Horn, TX, US

On August 23, 2001, a Piper PA-18-150 (registration N91187) was involved in an aviation accident near Van Horn, TX. Investigators recorded the probable cause as: The pilot's failure to maintain adequate airspeed which resulted in an inadvertent stall. A factor contributing to the accident was the high density altitude. 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 border patrol pilot, on routine patrol over rolling terrain, lost altitude during a right turn over a ridge. Despite full power and wing leveling, the descent continued and the aircraft impacted the next ridge. No mechanical anomalies were found.

Overview

A border patrol pilot was conducting routine patrol duties over rolling terrain at an estimated altitude of about 500 feet above ground level. The flight was normal until the aircraft began a right turn to cross a ridge.

Sequence of Events

While making a right turn and crossing a ridge, the pilot reported that "the bottom fell out," indicating a sudden loss of altitude or lift. The pilot immediately applied full engine power and leveled the wings in an attempt to arrest the descent. However, these actions were insufficient to stop the rate of descent, and the airplane impacted the next ridge line.

Post-Accident Examination

After the accident, investigators examined both the airframe and the engine. The examination did not reveal any anomalies that could have prevented normal flight operations. This suggests that mechanical or structural failure was not a factor in the accident.

Density Altitude

The density altitude at the time of the accident was calculated to be approximately 7,428 feet. Density altitude is a measure of air density corrected for temperature and pressure; higher density altitudes reduce aircraft performance, including engine power and lift, which can affect climb capability and stall margins.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20010912X01917. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.