Incident Overview
On Saturday, March 8, 2003, at approximately 10:30 local time, a Socata TB-10 Tobago with registration EC-FTG suffered an engine stoppage while flying at 6,500 feet. The aircraft was operating in the general aviation sector for instructional purposes, specifically as a solo navigation flight by a student pilot. The incident occurred in the foothills of the Sierra de Peña de Francia in Salamanca, Spain.
Flight Details and Response
The pilot, a 21-year-old student with 85 total flight hours, was undergoing training for a Commercial Pilot License (CPL(A)). Upon experiencing the engine failure, the pilot contacted the Salamanca Airport control tower to declare an emergency. Attempts to restart the engine were unsuccessful. The pilot selected suitable terrain and executed a landing without injury. The aircraft sustained minor damage to the landing gear fairing due to the unprepared surface. The pilot was located 45 minutes after the landing.
Technical Investigation
Investigations focused on the Lycoming O-360-A1AD engine and its ignition system. Initial inspections at the crash site and later at a maintenance center confirmed that the propeller turned freely but the engine failed to start due to insufficient battery voltage during cranking attempts. A detailed examination of the Teledyne Continental D4LN3000 magneto revealed that the contacts in both breaker points remained closed despite the rotation of the cam. This prevented spark generation at the spark plugs.
Root Cause Analysis
The investigation determined that the engine stoppage was caused by a failure in the magneto to generate a spark. The wear on the followers of the two breaker points prevented the separation of the contacts, thereby interrupting the ignition circuit. While the exact reason for this accelerated wear could not be definitively established, probable causes included contamination of the lubricating oil or excessive greasing of the cam and felt assembly. Replacing the breaker points restored normal engine operation.
Safety Recommendations
A safety recommendation (REC 07/2003) was issued to the Spanish Directorate General of Civil Aviation. It advised determining the implementation status of Teledyne Continental Service Bulletin No. 651 among operators of Socata Tobago TB-10 aircraft in Spain. The bulletin addressed potential electrical discontinuities between the magneto and capacitors, which could lead to arcing and subsequent ignition failure. Although the affected aircraft had this bulletin applied, the recommendation sought to ensure broader compliance to mitigate similar risks.