The Federal Aviation Administration (FAA) has issued a new airworthiness directive (AD) for all Boeing 737-600, -700, -700C, -800, -900, and -900ER series airplanes; following the cracks found on several 737 NGs, where the wing is attached to the fuselage, in a part commonly referred to as the pickle fork.
What Is a Pickle Fork?
The pickle fork is attached to the aircraft’s wing spar. It is a primary load-carrying component that helps attach the wings to the fuselage.
What is the Problem With 737?
In September 2019, the FAA received reports of cracking discovered in the left and right-hand side outboard chords of the station (STA) 663.75 frame fittings and failsafe straps adjacent to the stringer S-18A straps on multiple Boeing Model 737-800 airplanes during a passenger-to-freighter conversion.
The affected airplanes had accumulated between 35,578 and 37,329 total flight cycles.
This AD requires repetitive inspections for cracking of the left and right-hand side outboard chords of the STA 663.75 frame fittings and failsafe straps adjacent to the stringer S-18A straps.
If any crack is found, it must be repaired before further flights using a method approved by the FAA or The Boeing Company Organisation Designation Authorisation (ODA). After this, airlines have to send a report with all the results of the initial inspection to Boeing.
Airlines that have found cracks must repeat the inspection thereafter at intervals not to exceed 3,500 flight cycles.
The cracking, if not addressed, could result in the failure of a Principal Structural Element (PSE) to sustain the limit load and consequentially could adversely affect the structural integrity of the airplane and result in loss of control.
Costs
Since 1996, Boeing has delivered almost 7000 737 NG aircraft across the world, out of this total the FAA estimates that 1,911 airplanes have U.S. registry.
For the inspection required the FAA estimates that the airlines will require 1 work-hour, at a cost of $85 per hour, for all the 7000 airplanes this could mean a total cost of $595,000.
This AD is effective on October 3rd 2019.
Cover Image by Mike Siegel / The Seattle Times