FlightFinder
Check my flight
Casualties unknown

Engine Failure Due to Oil Depletion from Ruptured Oil Pressure Switch Diaphragm Leads to Forced Landing and Nose Gear Collapse (N84103)

Bridgeport, TX, US

On June 16, 1984, a Cessna 172K (registration N84103) was involved in an aviation accident near Bridgeport, TX. Investigators recorded the probable cause as: Failure of the No. 4 connecting rod due to lack of lubrication resulting from oil depletion caused by a ruptured diaphragm in an oil pressure switch, and non-compliance with Datcon Service Bulletin #1. 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 2026-07-04Data APIEditorial standards

During flight, a progressive loss of engine power occurred. Carburetor heat had no effect. A loud noise led to engine shutdown. Forced landing resulted in nose gear collapse and aircraft nosing over. Investigation found connecting rod failure due to lack of lubrication from oil depletion caused by a ruptured oil pressure switch diaphragm, and non-compliance with a service bulletin.

Event Description

During the flight, the pilot observed a gradual decrease in engine power. The application of carburetor heat did not restore power. Subsequently, a loud noise was heard, prompting the pilot to shut down the engine. During the ensuing forced landing, the nose gear collapsed and the aircraft nosed over.

Examination Findings

An examination of the engine revealed that the No. 4 connecting rod had failed. Internal damage was attributed to a lack of lubrication. Further inspection determined that the diaphragm of an oil pressure switch had ruptured, allowing the engine oil supply to deplete. The switch, Datcon part number 40558-1, had been installed directly into the engine block's tapped oil gallery hole on January 1, 1974, and was used in connection with the electrical operation of the aircraft's hourmeter. Additionally, it was found that Datcon Service Bulletin #1, titled "Hazardous Installation of Oil Pressure Switches" and dated January 2, 1975, had not been complied with.

Probable cause

Failure of the No. 4 connecting rod due to lack of lubrication resulting from oil depletion caused by a ruptured diaphragm in an oil pressure switch, and non-compliance with Datcon Service Bulletin #1.
Maintenance error

Frequently asked questions

What happened in the 16 Jun 1984 Cessna 172K accident near Bridgeport, TX?

During flight, a progressive loss of engine power occurred. Carburetor heat had no effect. A loud noise led to engine shutdown. Forced landing resulted in nose gear collapse and aircraft nosing over. Investigation found connecting rod failure due to lack of lubrication from oil depletion caused by a ruptured oil…

What aircraft was involved and where did it happen?

The accident on 16 Jun 1984 involved a Cessna 172K, registration N84103, at Bridgeport, TX.

What was the probable cause of the accident?

Failure of the No. 4 connecting rod due to lack of lubrication resulting from oil depletion caused by a ruptured diaphragm in an oil pressure switch, and non-compliance with Datcon Service Bulletin #1.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X39952. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.