Casualties unknown

1990-09-29: Mooney M-20-M (N9161D) — R. T. Dilley — Flagstaff, AZ

Flagstaff, AZ, US

On September 29, 1990, a Mooney M-20-M (registration N9161D) operated by R. T. Dilley was involved in an aviation accident near Flagstaff, AZ. Investigators recorded the probable cause as: Engine failure due to a ruptured fuel pump diaphragm. 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 1781061362Data APIEditorial standards

A Mooney M-20-M experienced engine failure on approach after the pilot switched tanks and activated the boost pump. Investigation of the nearly new aircraft found a ruptured fuel pump diaphragm.

Incident Overview

While maneuvering for landing at an airport, the pilot of a Mooney M-20-M encountered a complete loss of engine power. The pilot reported that he had just selected the fullest fuel tank and turned on the electric boost pump when the engine stopped. The aircraft had accumulated only 18 hours of total time since its manufacture.

Examination Findings

Post-incident inspection of the fuel system revealed a ruptured diaphragm inside the fuel pump. The fuel pump diaphragm is a critical component responsible for maintaining proper fuel pressure and flow to the engine. The aircraft's fuel system was new, having been installed at the time of manufacture.

Regulatory Guidance

Airworthiness Directive (AD) 91-08-07, issued by the relevant aviation authority, specifically addresses the potential for fuel pump diaphragm failures. Additionally, several service bulletins from Textron/Lycoming, the engine manufacturer, provide instructions for inspection and replacement of the fuel pump diaphragm to prevent such events. These documents are intended to mitigate the risk of engine failure due to diaphragm rupture.

The source did not provide information on injuries, fatalities, or other damage.

Probable cause

Engine failure due to a ruptured fuel pump diaphragm.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001212X24318. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.