FRANKFURT/Washington – Swiss International Air Lines decided to take return its entire fleet of 28 Airbus A220s to home base to make engine checks following another another engine-related diversion on Oct. 15.
Swiss said in a statement that all A220 engines have to undergo a “comprehensive inspection.” The aircraft will only be returned to service if no findings surface. Swiss said it will have to cancel many flights and is coordinating with airworthiness authorities, Airbus Canada and Pratt & Whitney.
French accident investigation authority BEA transferred leadership of the investigation to the U.S. NTSB.
Swiss stated that flight LX359 from London-Heathrow to Geneva had to divert to Paris-Charles de Gaulle on Oct. 15 “following a technical irregularity.” The airline declined to be more specific saying the incident is still under investigation. A picture released by BEA shows inspectors taking pictures of engine number one. Although an image obtained by Aviation Week appears to show damage typical of a low pressure (LP) turbine failure, it is possible that a failure of one of the PW1500G’s three LP compressor stages could have triggered downstream damage of a similar nature.
The youngest engines in the PW1500G and PW1900G fleets were hit with inspection mandates last month following two similar in-flight incident on Swiss A220s—one on July 25 and the second on Sept. 16. In both cases, number-one engine low-pressure compressor (LPC) stage 1 rotors fractured. The PW1500G and PW1900G are used on the A220 and the Embraer E2.
Following the second incident, Pratt recommended inspections of LPC stage 1 rotors and inlet guide vanes, and regulators quickly mandated the instructions. The checks applied only to engines with fewer than 300 cycles since new and must be done every 50 cycles until the engine reaches that threshold.
Both previous A220 failures occurred on Swiss’s Geneva-London Heathrow route as the flights were approaching cruise altitude—one at FL350 and one at FL320. In the July incident, the flight diverted to Paris. In last month’s incident, the crew returned to Geneva. The U.S. NTSB was designated as lead agency investigating both incidents, with the third one now added to investigation.
Damage from the second incident included a hole in the LPC case and a separated R1, the NTSB said. In the first incident, the LPC R1 was “missing,” the board said.
Pratt & Whitney said that it and the “airframe OEMs, working in coordination with the regulatory authorities, has recommended additional inspections of the low-pressure compressor for PW1500G and PW1900G engines to keep the fleet operational. This recommendation is related to the events involving recent PW1500G engines which are part of investigations being led by the U.S. National Transportation Safety Board (NTSB).” Pratt added that “the engines continue to meet all criteria for continued airworthiness. We are working closely with our customers to minimize disruption to their operations.”
Airbus stated that it is “aware of the incident.” The company added that it “sincerely regrets this impediment for our customers and passengers” and that it and Pratt support “our customer to minimize disruption to their operations.”
Airbus and Pratt & Whitney “are informing all A220 operators of additional recommendations as precautionary measures. These new measures include: a one-off visual borescope inspection and engine low pressure compressor speed limitation.These mitigation measures are put in place as a precautionary measure for the fleet until root cause is identified.”
Swiss operates 20 A220-300s and eight -100s. Airbus delivered a total of 56 -300s and 34 -100s to airlines (as of Sept. 30). Swiss is currently the largest operator followed by Delta Air Lines (25 aircraft) and Air Baltic (20). Delta says its operations continue as normal. Air Baltic is traditionally coordinating closely on A220 matters with Swiss, but it did continue A220 operations in spite of the latest incident.
Air Baltic stated that it “is closely following engine manufacturer Pratt & Whitney’s recommendations on additional inspections.” Engines “meet all criteria for continued airworthiness.” Air Baltic CEO Martin Gauss said that the airline uses the PW1500 in a lower thrust setting than Swiss.