By Rob Finfrock
The German Federal Bureau of Aircraft Accident Investigation determined that cracking in the diffuser assembly of one of the aircraft’s Williams FJ44-3A-24 turbofans led to an uncontained engine failure and emergency landing for a Citation CJ2+ (type shown below) operated by Eisele Flugdienst GmbH (EFD) at Stuttgart Airport (EDDS) on March 1, 2010.
“Simultaneously with the retraction of the flap from 15° to 0° the pilot noticed unusual vibrations and a strong left yawing moment,” the report stated. “Immediately afterwards he heard the acoustic warning Left Engine Fire … [and] the inter-turbine temperature (ITT) was far in the red area.”
The pilot shut power down in the affected engine and pushed the engine fire switch, which turned off the fire warning. The aircraft returned to Stuttgart and made an uneventful landing.
A post-incident inspection revealed apparent engine damage, and the aft outer cowling of the plane’s left engine had been “destroyed.”
Investigators later learned that passengers had reported a noticeable smoke smell in the cabin on two previous flights, “eliminated by selecting the Air Source switch to the right engine.” Crews also reported indicated turbine temperatures in the left engine that were 20°-30°C higher than the right over the past six months.
At the time of the incident, Williams noted 17 cases of diffuser cracks with the FJ44-3A series, although no reported cases in the -24 variant. In April 2010, the manufacturer issued an advisory for operators to be aware of the signs of potential damage in the diffuser assembly; as of January 2015, Williams noted that “almost all” FJ44-3A-24 engines in service have been refitted with a reinforced diffuser developed for the FJ44-4 series.
Curiously, the incident was also the subject of an Internet hoax shortly following the April 2010 eruptions of the volcano Eyjafjallajökull in Iceland, which disrupted air travel across Europe and the North Atlantic. Photos of the engine (above) were posted online that falsely attributed the damage to ingestion of volcanic ash.