ASN Wikibase Occurrence # 370331
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| Date: | Thursday 28 April 2005 |
| Time: | 05:30 LT |
| Type: |  McDonnell Douglas MD-11 |
| Owner/operator: | World Airways |
| Registration: | N277WA |
| MSN: | 48743/590 |
| Engine model: | Pratt & Whitney PW4460 |
| Fatalities: | Fatalities: 0 / Occupants: 201 |
| Aircraft damage: | Minor |
| Category: | Serious incident |
| Location: | Anchorage, AK -
 United States of America
|
| Phase: | En route |
| Nature: | Passenger |
| Departure airport: | Osan Air Base |
| Seattle/Tacoma International Airport, WA (SEA/KSEA) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The flight crew was conducting an international passenger flight under Title 14, CFR Part 121, when they smelled and saw smoke in the cockpit. The pilot declared an emergency, and diverted to the nearest airport, where the airplane landed without incident. According to the flight crew, just prior to the smell and smoke, there was a crew change that required the cockpit security door to be opened and closed. An examination of the security door by maintenance personnel and the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) revealed an excess length of wiring, which provides power to the electrically locking security door, was laying atop the door's metal-encased, unshielded, locking solenoid inside the doorframe. Several of the wires were encased in a plastic anti-chafe mesh. A portion of the mesh was melted, and had the smell of burnt plastic. During a discussion with the IIC, a mechanic said he had seen similar doors overheat when the door and frame were misaligned, prohibiting full extension of the locking bolt. The cockpit door was modified in accordance with Supplemental Type Certificate (STC) ST01391LA, which meets the FAA's requirements for a reinforced cockpit door. The door uses a "demand access" electrically operated door latching solenoid. The door manufacturer issued an addendum to the airplane manufacturer's maintenance manual. The addendum includes removal, installation, and system tests of the striker/solenoid unit. The installation section does not specifically address the issue of securing excess wiring located above the striker/solenoid within the doorframe. The installation instructions do contain a "caution," referencing the need for the security bolt to engage fully. Failure of the bolt to fully engage will cause the solenoid to remain energized and overheat. Construction of the striker/solenoid assembly is such that the metal-encased electrical coil of the unshielded solenoid is the upper-most portion of the assembly within the doorframe. The installation includes a warning light that illuminates if the solenoid does not shut off. The crew did not report seeing the warning light in-flight, and the light and locking mechanism functioned properly during subsequent tests on the ground; it was not tested in-flight. The conversion of the door was completed on March 21, 2003. Prior to the incident, the new security door had been in service about 16,416 flight hours, and 1170 cycles. FAA Advisory Circular (AC) 65-15A, Chapter 11, covers practices and procedures for the installation and maintenance of aircraft electrical wiring. The AC notes that practices and procedures outlined in this section are general recommendations, and are not intended to replace the manufacturer's instructions. Chapter 11, page 441, Slack in Wiring Bundles, states: "Single wires or wire bundles should not be installed with excessive slack." Page 442, Routing and Installations, states: "All wires and wire groups should be routed and installed to protect them from: (2) high temperatures."
Probable Cause: The inadequate installation of the cockpit security door locking device, which resulted in smoke in the cockpit during normal cruise, and a precautionary landing. A factor associated with the incident was the manufacturer's insufficiently defined installation instructions.
Accident investigation:
 |
|
Sources:
NTSB ANC05IA064
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 25-Mar-2024 09:35 | ASN Update Bot | Added |
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