Electrical short circuit in altimeter causes smoke and system failures on Fokker F27

Casualties unknown • Incident involving aircraft SE-LIP at Stockholm/Arlanda airport, SE

A short circuit in a cockpit altimeter led to smoke, an electrical burning smell, and the loss of critical navigation data during a flight near Stockholm/Arlanda.

What happened

On 1 June 2006, a Fokker F27 MK050, registration SE-LIP, was climbing through 14,000 feet northeast of Stockholm/Arlanda airport when the crew encountered a sudden technical emergency. About 15 minutes after departing for Wasa, Finland, a red warning flag appeared on the commander's altimeter, and the Altitude Select instrument failed. Simultaneously, the crew observed faint smoke emerging from the central control console and detected the smell of electrical burning.

The commander declared an electrical fire and requested an emergency return to Arlanda. To manage the smoke, the crew donned oxygen masks, and the commander handed flight control to the co-pilot. To minimize time in the air during the suspected fire, the crew opted for a straight-in approach to runway 19R. This decision resulted in a landing with a tailwind component of 10–15 knots, which exceeded the operator's maximum permitted limit of 10 knots.

The investigation

The Swedish Accident Investigation Authority (SHK) examined the aircraft's instruments and the crew's actions. The technical investigation focused on the Thomson-CSF altimeter located in the left pilot's seat. Investigators also reviewed the communication gap that occurred during the emergency approach and the operational practices regarding oxygen mask usage.

Findings

  • The primary cause of the incident was a short circuit within the left-side altimeter.
  • This electrical fault caused smoke to enter the cockpit and triggered failures in the aircraft's flight data and navigation systems, including the transponder, TCAS, and TAWS.
  • The short circuit was traced to a capacitor within the instrument. Over time, vibrations had caused an electrical wire to become trapped against a metal base plate, eventually leading to mechanical damage and the short circuit.
  • During the emergency, radio communication with air traffic control was lost for approximately five minutes. This occurred because the commander had not connected the audio lead of his oxygen mask. This was due to a local pilot practice of disconnecting mask audio connections to avoid background noise interference.
  • The landing was performed with a tailwind exceeding company limits to ensure the fastest possible arrival at the airport.

Probable cause

An internal short circuit in the left-side altimeter caused smoke, an electrical burning smell, and the failure of several critical flight and navigation systems.

Frequently asked questions

What happened in the 2006-06-01 aircraft accident near Incident involving aircraft SE-LIP at Stockholm/Arlanda airport, SE?

A short circuit in a cockpit altimeter led to smoke, an electrical burning smell, and the loss of critical navigation data during a flight near Stockholm/Arlanda.

What aircraft was involved and where did it happen?

The accident on 2006-06-01 involved a aircraft, registration SE-LIP, at Incident involving aircraft SE-LIP at Stockholm/Arlanda airport, SE.

What was the probable cause of the accident?

An internal short circuit in the left-side altimeter caused smoke, an electrical burning smell, and the failure of several critical flight and navigation systems.

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