Regarding Post # 8461 on Page 424, Leightman 957 says to 777fly - “the report also states that the event is far less likely in the air than on the ground. (in Sec 1.18.3).” The AAIB report in play is AAIB Report # 2/2009.
Link >
http://www.bea.aero/docspa/2010/hs-l...l100318.en.pdf.
And Leightman 957 adds in post # 8445 on page 423, “There were similar incidents prior to, and after, this one. The cause was molten metal at up to 1000 deg C being released from BTB and GB contactors. The reasons why this happens is still not fully understood. An airborne failure of this kind could have left the crew with an unmanageable situation due to multiple systems failure: VHF disabled, ACARS fail, dual FMS failure, flightdeck smoke, alternate nav diversion, loss of situational awareness, oxygen depletion, unconciousness, a/c nav to incorrect lat/long entry.... “
Leightman 957 is correct about the in-flight probability and the danger of a growing fire again at post 8470.
My concerns aren’t the matches (electrical malfunctions), but rather the fuel for a fire.
From page 9 of this same report (Sec 1.6.3, Insulation blanket specification and maintenance) it also said; “The insulation blankets fitted to the fuselage structure adjacent to the P200 power panel were determined to be the original equipment manufacturer (OEM) blankets, fitted in 1997. These blankets consisted of fibreglass batting ….. covered with a polyethylene terephthalate film.”
“In 2008 the US FAA issued an Airworthiness Directive (2008-23-09) requiring the replacement of certain insulation blankets manufactured with some types of polyethylene teraphthalate film. The insulation blankets installed in N786UA were not among those whose replacement was required.”
“Contamination on insulation blankets can affect the blanket’s fire retardant capabilities. The aircraft manufacturer published a Service Letter (777‑SL‑25‑018) on 23 March 1998 which informed operators of: ‘the potential fire hazard if combustible materials (contamination) such as overspray of corrosion inhibiting compound (CIC), hydraulic fluids, oil, pesticides with flammable ‘carrier’ fluids, grease or dust buildup are allowed to accumulate on the insulation blankets outboard of the passenger/cargo compartment linings. Some types of contaminates have been found to support propagation of flame.”
This incident is among 10 other E & E bay fires at my post # 8220 on Page 411 - “Past E & E Bay Fires, FACTUAL DATA.” – as “2/26/07. United 777” , the United incident on February 26, 2007. It was posted because any arc event anywhere in any of the Boeing models is a “identified safety risk” because the installed acoustic/thermal insulation (“polyethylene teraphthalate film” or PET is flammable as seen in AD 2008-23-09 calling for removal of PET (aka Mylar-AN-26) by December 2016 in all Boeing models --------- except the 777s.
The AAIB report said “The insulation blankets installed in N786UA were not among those whose replacement was required.” was because the 777s were excluded from the 737s, 747s, 757s and 767s in this AD. I do not know why T7s were excluded but “polyethylene terephthalate” known as PET was the installed insulation.
Two other 777 E & E bay fire incidents at Post 8220 mentioned the flammability of insulation blankets when exposed to electrical arcs. Both came from NTSB Safety Recommendation Letter A-07-113-116. NTSB Letter Link >
http://www.ntsb.gov/doclib/recletter...07_113_116.pdf There, electrical arcing set adjacent insulation blankets afire.
Regarding the first, British Airways 777 on 11/15/2004 the Letter said; (Ref page 1) “Following the incident, British Airways conducted a fleetwide visual inspection on its model 777 airplanes (43 total aircraft). Fifty-five percent of the receptacles that were inspected contained contact pins that exhibited signs of overheating; 12 percent contained contact pins that were loose and had evidence of melting at the base of the pins. A secondary external power receptacle that showed signs of electrical arcing and extensive thermal damage to its protective cover was sent to Boeing for analysis.” And that; (Ref page 3) “Alternately, molten splatter could result in ignition of nearby materials such as dust, lint, or insulation blankets. Such damage could potentially compromise critical aircraft functions.”
Regarding the second, a United 777 on 7/6/2004, the Letter said; (Ref page 2) “The second reported event occurred on July 6, 2004. According to the operator, a post incident inspection performed by a maintenance technician revealed evidence of overheating on the secondary external power receptacle and thermal damage to an adjacent insulation blanket.”
My 10 incidents of E & E bay fires came from across all models mentioned in the AD.
Another 9 insulation fires in cockpit or fuselage areas were not listed because they were outside of this most critical area. All are of great concern.
In the AD discussion - a chilling read - it is made clear that any fire in any hidden or unprotected area is a most serious concern. The 777s should have been included.
See this AD at Link >
http://www.airweb.faa.gov/Regulatory...2008-23-09.pdf
My thanks to Leightman 957 and others for recognizing this possibility.