Casualties unknown

1985-07-24: Piper J3C-65 (N70336) — H. A. Martin — Oakland, MD

Oakland, MD, US

On July 24, 1985, a Piper J3C-65 (registration N70336) operated by H. A. Martin was involved in an aviation accident near Oakland, MD. Investigators recorded the probable cause as: Oil contamination and broken high-tension terminals in the left magneto, which likely contributed to an engine malfunction during low-power operation. 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

An aircraft flying low and slow at tree-top level impacted the ground in a near-vertical attitude. Investigation revealed oil contamination and broken terminals in the magneto.

What happened

The aircraft was observed on the day of the flight, as well as during the preceding couple of days, operating at an unusually low altitude. Witnesses on the ground reported that the plane was flying very slowly, maintaining an altitude consistent with tree-top level. Although ground witnesses heard the sounds associated with the crash, they were unable to visually observe the aircraft at the moment of impact.

The aircraft subsequently struck the ground in a near-vertical attitude. At the time of the accident, the engine was operating under low power settings. The magneto switch had been selected to the right magneto position.

The investigation

Examination of the engine components revealed significant mechanical anomalies. Both magnetos were found to contain oil, indicating a potential sealing failure or contamination issue. Additionally, two high-tension terminals within the left magneto were broken. These findings suggest that the electrical system may have been compromised despite the switch being set to the right magneto.

Findings

The combination of low-power operation and the presence of oil in both magnetos, along with the broken terminals in the left magneto, points to a failure in the ignition system. The aircraft's flight path at tree-top level left little margin for error or recovery.

Probable cause

Oil contamination and broken high-tension terminals in the left magneto, which likely contributed to an engine malfunction during low-power operation.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X36998. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.