Landing-gear actuators focus of Q400 probe

 - September 27, 2007, 6:43 AM

Technical difficulties continued to dog regional airplanes built by a financially resurgent Bombardier last month, as no fewer than 85 Q400 turboprops sat idle while operators performed emergency inspections on their main landing gear.

Two incidents of collapsed landing gear over the span of three days involving Scandinavian Airlines (SAS) Bombardier Q400s prompted Bombardier on September 12 to call for the grounding of any Q400 that had accumulated more than 10,000 landing gear cycles. Later that day a Transport Canada AD called for an immediate detailed visual inspection of main landing gear retraction actuators on the 85 or so Q400s that had accumulated 8,000 or more landings or that had flown in service for more than four years. The AD also required a general visual inspection of the left and right main landing gear system and main landing gear retraction actuator jam nuts on all Q400s.

The latest incident happened September 12 in Vilnius, Lithuania, three days after the right landing gear of an SAS Q400 collapsed upon touchdown in Aalborg, Denmark, resulting in five injuries. No injuries resulted from the Vilnius incident, which also involved the airplane’s right landing gear. The 74-seat turboprop was on its way to the western Lithuanian city of Palanga but landed at Vilnius after the crew discovered the problem while airborne.

Apart from the two damaged airplanes, SAS grounded all 21 of the remaining Q400s it flies under its brand, and the company’s Norwegian subsidiary, Wideroe’s Flyveselskap, grounded the four that it flies. Meanwhile, Austrian Airlines grounded eight airplanes; Germany’s Augsburg Airways, six; Japan Air Commuter and All Nippon Airways grounded two and one, respectively; and the UK’s Flybe, six.

In the U.S., Seattle-based Horizon Air grounded 19 of its 33 Q400s, forcing it to cancel 154 flights on September 13 and 121 flights on September 14. A spokeswoman for Horizon said that parent company Alaska Airlines would send 13 Boeing 737s to help compensate for the lost capacity. Horizon expected to run a modified schedule using the 737s until September 24, by which time it had hoped to finish all its inspections.

Preliminary findings by Danish civil aviation agency investigators indicated that corrosion inside the actuator piston of the airplane caused the piston to separate from its rod end, a condition that led to the gear collapse. If final reports confirm the early findings, whether or not Bombardier’s maintenance schedule specifically calls for inspection of the pistons could determine its liability for lost revenue resulting from all the canceled flights.