APU Exhaust Liner Failure Causes Smoke and Heat Damage to Dash 8

Casualties unknown • Belfast City Airport, GB

A partial disintegration of an APU exhaust duct liner led to smoke and heat damage on a Dash 8 at Belfast City Airport, following an uninvestigated debris event two days prior.

What happened

On 30 October 2016, a DHC-8-402 Dash 8, registration G-ECOF, was preparing for departure at Belfast City Airport when ground handlers reported smoke emanating from the rear of the aircraft near the Auxiliary Power Unit (APU). While the flight crew initially observed no internal smoke or fire warnings, a burning odour soon became apparent. The commander initiated a precautionary disembarkation of the 77 passengers and 4 crew members.

During the event, the APU automatically shut down, and the aircraft' and tail cone exhibited visible heat damage, including discoloured external surfaces and blistering paint. Thermal imaging by the airfield fire service revealed temperatures of approximately 158°C in the APU area. There were no injuries and no fatalities during the incident.

The investigation

The investigation established that the APU exhaust duct liner had partially disintegrated. This failure allowed hot exhaust gases to escape the liner and enter the tail cone volume. The investigation also uncovered that two days earlier, while the aircraft was at Birmingham, a piece of debris had been found on the ground near the aircraft. The crew at the time had assumed the object originated from a ground vehicle and did not link it to the aircraft's APU system.

Examination of the aircraft revealed that the front half of the liner had broken away. The heat from the escaping gases had caused significant damage to electrical cables in the tail cone, which likely triggered the APU's automatic shutdown due to an open circuit condition.

Findings

  • The primary cause of the smoke was the disintegration of the APU exhaust duct liner, which directed hot gases into the tail cone.
  • A piece of the liner had actually been ejected from the aircraft two days prior at Birmingham, but the event was misidentified as debris from a ground vehicle.
  • The aircraft manufacturer had previously recorded 17 similar incidents involving duct liner cracks or failures on this aircraft type.
  • The location of the liner makes effective inspection difficult unless the APU is removed from the aircraft.

Probable cause

The partial disintegration of the APU exhaust duct liner allowed hot exhaust gases to escape into the tail cone, causing smoke and heat damage. The failure was not prevented because the preceding ejection of a liner fragment two days earlier was incorrectly attributed to airport ground equipment.

Frequently asked questions

What happened in the 2016-10-30 DHC-8-402 Dash 8 accident near Belfast City Airport, GB?

A partial disintegration of an APU exhaust duct liner led to smoke and heat damage on a Dash 8 at Belfast City Airport, following an uninvestigated debris event two days prior.

What aircraft was involved and where did it happen?

The accident on 2016-10-30 involved a DHC-8-402 Dash 8, registration G-ECOF, at Belfast City Airport, GB.

What was the probable cause of the accident?

The partial disintegration of the APU exhaust duct liner allowed hot exhaust gases to escape into the tail cone, causing smoke and heat damage. The failure was not prevented because the preceding ejection of a liner fragment two days earlier was incorrectly attributed to airport ground equipment.

Loading the flight search…