NTSB Cites 'A Chemically Milled Step' In Airplane Depressurization | Aero-News Network
Aero-News Network
RSS icon RSS feed
podcast icon MP3 podcast
Subscribe Aero-News e-mail Newsletter Subscribe

** Airborne/NBAA2014 10.22.14 ** HD iPad-Friendly -- Airborne/NBAA2014 10.22.14 **
** Airborne/NBAA2014 10.21.14 ** HD iPad-Friendly -- Airborne/NBAA2014 10.21.14 **
** Airborne/NBAA2014 10.20.14 ** HD iPad-Friendly -- Airborne/NBAA2014 10.20.14 **

Sat, Aug 21, 2010

NTSB Cites 'A Chemically Milled Step' In Airplane Depressurization

"Preexisting Fatigue" Named As Probable Cause For A Hole Opening In A Southwest Airlines 737

The NTSB says "fuselage skin failure due to preexisting fatigue at a chemically milled step" is the probable cause for a 18x12 inch hole opening up in the roof of a Southwest Airlines 737 last year, causing the airplane to depressurize. No one was injured due to the incident.

NTSB Identification: DCA09FA065
Scheduled 14 CFR Part 121: Air Carrier operation of SOUTHWEST AIRLINES CO
Accident occurred Monday, July 13, 2009 in Charleston, WV
Probable Cause Approval Date: 8/18/2010 1:52:06 PM
Aircraft: BOEING 737, registration: N387SW
Injuries: 131 Uninjured.

Flight data recorder data revealed that the airplane took off and climbed for about 25 minutes to an altitude of approximately 35,000 feet, at which point the cabin altitude warning activated, and the captain disengaged the autopilot. Postincident examination of the airplane revealed fatigue cracking of the fuselage skin near the leading edge of the vertical stabilizer adjacent to the rupture. The fatigue cracking penetrated the fuselage skin and created an approximate 18-inch by 12-inch flap in the skin that depressurized the airplane.


NTSB Photo Exterior Skin

The fuselage skin assembly near the leading edge of the vertical stabilizer was manufactured by bonding two full aluminum sheets together, then selectively chemically milling away pockets (bays) of the inner sheet. Continuous fatigue cracks initiated from multiple origins on the inner surface of the skin adjacent to the step formed at the edge of the chemically milled area and propagated outward.

Following the Southwest Airlines (SWA) flight 2294 event, on September 3, 2009, Boeing issued Service Bulletin (SB) 737-53A1301, calling for repetitive external inspections to detect cracks in the fuselage skin along the chemically milled step at stringers S-1 and S-2 right and between BS 827 and BS 847. (The hole from the SWA event was within those boundaries.) If cracks are detected, operators are to contact Boeing for repair instructions. On January 12, 2010, the Federal Aviation Administration issued Airworthiness Directive 2010-01-09, which mandated the inspection requirements in SB 737-53A1301.


NTSB Photo Interior Skin

The airplane, serial number 26602, was delivered to SWA in June 1994. At the time of the SWA event, the airplane had accumulated approximately 42,500 cycles and 50,500 hours.

FMI: www.ntsb.gov

Advertisement

More News

Game-Changing NBAA2014 Sponsor Mid-Continent Instruments and Avionics!

Innovation Brings Safe, Certified, Nanophosphate® Lithium Batteries To New Business Aircraft True Blue Power is the first company in the world to achieve FAA TSO and EASA ETSO >[...]

Embraer’s Legacy 500 Receives FAA Certification

EASA Certification Expected Later This Year The FAA handed over certification papers for Embraer's Legacy 500 executive jet during a ceremony at the National Business Aviation Asso>[...]

Airborne at NBAA--10.21.14: NBAA2014 Opens, Eclipse Update, FJ44 TBO Increase

Also: Shuster/Hart Address NBAA, Gogo Means Business, BBJ Maxes Out, Hartzell Pulls Its Weight The NBAA Opening General Session featured two well-known names from Washington. Repre>[...]

Airborne at NBAA-10.22.14: Legacy 500, Universal InSight, BendixKing AeroWave

Also: GE Honda, Sagem's Active SideStick, Syberjet Update, Techno Aerospace Knows How to Party The FAA handed over certification papers for Embraer's Legacy 500 executive jet durin>[...]

ANN's Daily Aero-Linx (10.23.14)

Experimental Balloon and Airship Association A loose congregation of aeronauts who have built, are flying or own any sort of Experimental, Ultralight or Homebuilt Lighter-Than-Air >[...]

blog comments powered by Disqus



Advertisement

Advertisement

Podcasts

Advertisement

© 2007 - 2014 Web Development & Design by Pauli Systems, LC