A safety question mark has been put against the world’s most commonly flown jet, the Boeing 737, by the US equivalent of CASA, the Federal Aviation Administration.

It has issued a proposed airworthiness directive which would compel airlines to perform a wide range of inspections and possible repairs or overhauls to the small stubby wings beside the tails of the jets to prevent a potential loss of control.

And it’s all about balls, well, ball bearings.

Close to 100 of the various models of the 130-180 passenger single aisle 737 family are in daily service in Australia with Virgin Blue and Qantas, plus the VIP versions used by the PM and his media entourage that are known affectionately as Reptile One and Reptile Two.

The FAA’s proposed directive which would be automatically adopted world wide for insurance reasons if no other, will come into force subject to feedback from the airlines by mid June.

The overnight alert was issued because of concerns raised during a design and safety review that Boeing conducted earlier this year into the trim units on all of its airliners.

The specific concern is the risk of failure in the horizontal stabilizer trim actuator similar to one that broke off an aged OzJet 737 over the Christmas holiday period and saw its pilots struggling to maintain control before making an emergency landing in Port Moresby.

A Qantas engineer says Boeing is paranoid about the tiny part because it is the component most likely cause a crash if not meticulously maintained in a 737 no matter how new or old.

But until the Boeing review took place no-one had suspected there could be extensive corrosion in critically important ball bearings inside these trim mechanisms. When such corrosion was found inside a 757 trim unit similar to those on its 737s the alarm bells went off because a new way for the control device to fail had been identified.

Without trim control it is extremely difficult if not impossible to maintain level flight, as infamously happened to an Alaska Airlines MD-83 on 31 January 2000, which flipped upside down and crashed into the sea near Los Angeles killing all 88 people on board.

What’s the bet the PM’s 737 gets its ball bearings checked faster than any others, and that serious examinations of the other Australian jets in question happen well before they become compulsory?

Peter Fray

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