Tuesday, January 28, 2014

FAA orders changes to Boeing 767 elevators

by GLENN FARLEY / KING 5 News Aviation Specialist
Bio | Email | Follow: @GlennFarley

Posted on January 27, 2014 at 5:57 PM
Updated yesterday at 5:58 PM
SEATTLE -- The Federal Aviation Administration on Monday published details of an Airworthiness Directive ordering airlines to change out a certain kind of rivet used to attach a type of linkage controlling the elevators on Boeing 767 jetliners.

The elevator is a moveable part of the plane's horizontal stabilizer in the tail that allows the plane to climb or decent.

The order affects 415 jets owned by U.S. based carriers and will likely extend through foreign regulatory agencies to more than 900 767s. That includes nearly every airplane from the first 767-200 models to the 767-400ER.

But the order is not considered an emergency. In fact, the FAA is giving airlines six years to comply with a permanent or "terminal repair" designed to fix a long standing problem involving repeated inspections that's gone on for well over a decade.

The concern is over a type or rivet designed as a safety device, something called a shear rivet that is designed to break under certain circumstances to prevent the elevator from jamming.

"It's designed so that if one of the bell crank assemblies jams up, it will simply shear the rivets out and the others will be able to operate normally,"  said John Nance, a pilot and air safety analyst.

The 767 elevators involve six bell cranks that transmit motion from actuators to the rudder itself.  It's all part of a redundant system where one or more bell crank failures will not cause problems.

The FAA became concerned "by reports of failed shear rivets in the bellcrank assemblies of the elevator power control actuator" according to the Airworthiness Directive.  In other words, some rivets failed when they weren't supposed to.

Previous AD's issued on the rivets called for inspections. But now the FAA is confident enough with Boeing's design that it's ordering solid rivets be installed instead.

"This actually isn't a big deal, actually what it does is showing that the system is working very well,"  said Nance, referring to the interaction between airlines, Boeing and the FAA.

There have been no accidents involving 767s as a result of the rivet problem.

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