Aircraft

Nationwide 737 engine-loss inquiry finds fatigue crack in mount

By David Kaminski-Morrow

Preliminary investigations have discovered a fatigue crack in the aft engine mount of the Nationwide Airlines Boeing 737-200 which shed its right-hand powerplant on take-off last month.

The finding follows the South African civil aviation authority’s 29 November decision to ground the carrier pending airworthiness and maintenance checks. The airline has had to cancel more than 90 flights across its network.

Nationwide says that a preliminary examination from the metallurgical department of the University of Pretoria has found a “recent fatigue crack” which led to the failure of the aft primary engine mount on a 737 departing Cape Town on 7 November. The aircraft lost its right-hand engine but returned safely to the airport.

Fatigue failure of aft cone bolts has been attributed to a number of engine-separation incidents involving 737-200s – among them a US Air aircraft at Deptford in December 1987, a United Airlines jet at Chicago in January 1989, and a Delta Air Lines aircraft at Dallas in January 1992. All three lost their right-hand engines on take-off.

The fatigue finding casts doubt on earlier suggestions that ingestion of a foreign object led to the Nationwide incident.

Nationwide chief executive Vernon Bricknell has defended the airline’s maintenance and safety record, and adds: “We are in possession of all relevant non-destructive testing records which substantiate the correct testing of all our bolts at the time of engine installation.”

Grounding of the fleet, says Bricknell, was a “total surprise” particularly because the CAA had only renewed the maintenance division’s licence on 23 November. He says the grounding apparently arose from concerns over maintenance performed after the issuing of an airworthiness directive on 9 November, two days after the 737 engine incident.

Bricknell says that, after the CAA performed an audit in September, the carrier implemented a series of improvements – including checks on life-limited components, better monitoring processes, and the appointment of a new accountable manager for maintenance – and has just submitted an action plan to the authority.

He points out that the airline passed IATA’s operational safety audit last year and that the CAA’s concerns centre on administrative systems within the carrier’s maintenance organisation, rather than the fleet.

“The CAA has not raised any concerns that relate directly to any of our aircraft,” he says, stressing that the carrier only uses legitimate components from authorised suppliers, supported by appropriate documentation.