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On February 28, 2009 at approximately 0840 EST, a Bombardier Aerospace CRJ-200, N830AS, experienced a fire on the ground shortly after external power was applied to the airplane in preparation for flight. The flight attendant and captain of the aircraft first became aware of the situation due to an unusual hissing sound which was quickly followed by smoke and signs of a fire. They immediately evacuated the airplane via the airstair without injuries. They were the only individuals on the airplane at the time. The fire department extinguished the fire, but not before it had burned a hole through the left upper cockpit crown skin. The airplane was registered to and operated by Atlantic Southeast Airlines as flight 5563 under the provisions of 14 Code of Federal Regulations Part 21. The flight was to be from Tallahassee Regional Airport (TLH), Tallahassee, Florida, to Hartsfield Jackson Atlanta International Airport (ATL), Atlanta, Georgia.
Neither the captain nor the flight attendant were injured.
DAMAGE TO AIRPLANE
Aircraft Exterior Fire Damage
The external fire damage was limited to an area of the forward left side of the aircraft between the flight deck and the L1 door. The damage consisted of an oblong area of fuselage burnthrough with a maximum height of 16 inches and a maximum width of 6 inches. The burnthrough area began 2 inches aft of the vertical portion of the windshield frame and 10 inches up from the horizontal portion of the windshield frame. Surrounding the area of burnthrough was an area of fuselage skin with the paint having been burnt off. Along the periphery of the bare aluminum area was a region of black, charred, and bubbling paint.
Flight Attendant Station Fire Damage
On the left side of the aircraft just behind the flight deck there was a flight attendant station and wardrobe unit. The front of the wardrobe unit had sustained fire damage along the top portion. The intercom and the observer's oxygen mask stowage box had become discolored and were deformed. The middle storage unit (on the top row) was charred along the upper portion of its door.
The back of the wardrobe unit had sustained heavy fire damage. The most severe damage was concentrated along the top and forward portions of the rear of the unit. On the forward portion of the back of the flight attendant's station the fire damage extended to 14 inches from the bottom. On the aft portion the fire damage extended to 27 inches from the bottom. In this area the slack in the flexible oxygen line servicing the observer's oxygen mask stowage box was hanging. In the middle of the back side of the wardrobe unit there was a removable panel. This panel had sustained significant fire damage and the honeycomb core of the panel was exposed and charred from its midpoint upwards.
The forward facing side of the wardrobe unit had sustained fire damage along its upper and outboard portions. The head rest of the stowed observer's seat was heavily charred. The aft facing side of the wardrobe unit did not exhibit fire damage.
Aft Face of Bulkhead 280 Fire Damage
After removal of the wardrobe unit from the aircraft, the aft face of bulkhead 280 (the bulkhead behind the captain's seat) was visible. The aft face of the bulkhead was made out of aluminum. This bulkhead was mostly undamaged by the fire with the exception of areas not protected by the presence of the wardrobe unit. There was an area of burnthrough on the aft face of this bulkhead beginning at a height of 55 inches above floor level. Moving upward and inboard from the burnthrough area there was blistered paint which then gradually transitioned to heavy sooting. Through the area of burnthrough, a portion of the back of the circuit breaker panel (behind the captain's seat) was visible. Examination of the circuit breaker panel revealed that the damage was limited to sooting along the top portion with increasing thermal damage becoming present towards the outboard top section.
Area Behind Wardrobe Unit Fire Damage
The area behind the wardrobe unit was where the most significant fire damage was found. There was an electrical junction box (JB-1) located in this area directly below the area of burnthrough. This box had three sections. The top section was heavily damaged and its top and inboard facing portions of the enclosure had burned away, allowing exposure of its internal components. The top section was associated with the APU and external ground power switching components. The two lower sections had soot on the outside and inside surfaces but were essentially intact. The top section of the junction box is where clean burn begins and extends upward past the area of skin burnthrough. The insulation had burned away in the frame section above the junction box extending up to where the wardrobe unit would have ended. Small charred remnants of glass batting type insulation were found in the frame section just behind the topmost section of the junction box. The components in the frame section aft of the section containing the junction box were significantly less damaged. The foam padding type insulation in this frame section was charred beginning just above the black electrical boxes.
The insulation on all of the wiring from a height of approximately 40 inches above floor level, in both of the frame sections, was burned away. The wiring below this level was still sheathed with insulation and, with the exception of soot, was not compromised by the fire. After the electrical components in both of the frame sections were removed the insulation material behind them was visible. In the aft frame section the insulation was relatively intact from floor level up to a height of approximately 40 inches. In the forward frame section the fire damaged insulation extended further down, including a small area at floor level. Adhering to the insulation in these lower areas of fire damage were re-solidified blobs of aluminum and plastic material. Extending from below deck up to the crown in the forward frame section were 4 coaxial antenna cables and a ventilation duct. The ventilation duct was wrapped with glass batting insulation. None of the wiring in the two frame sections that were behind the wardrobe unit exhibited evidence of arcing.
JB-1 Junction Box Internal Fire Damage
The JB-1 junction box was located directly below the fuselage burnthrough. The fire damage to the JB-1 unit was mostly concentrated inside the upper of three compartments, which contained AC external power and the APU power cable routing. This compartment was heavily fire damaged and large portions of the aluminum case and its entire front cover were burned away. The lower two compartments of the JB-1 unit sustained thermal damage and sooting from the outside inwards.
The portion of the junction box case surrounding the terminal connector studs for the external AC service was burned away. Some of the case material had melted and deflected out of position. Of the three terminal connector studs, the one belonging to terminal A was found with the outer nut loose. No evidence of overheating or arcing was observed and after disassembly of the connector the components had the same appearance as the components of the other two connector studs (B, C) that were not found loose.
Below the external AC connector studs, were the three APU input connector studs. These three studs were connected to copper buss bars inside the junction box that lead to the contactors in the top compartment. The buss bar connected to terminal stud T1 appeared to have localized melting along one side of the periphery of its connection to the terminal stud. Disassembly of the terminal stud revealed that the stud, washers, lock washers, and nuts had not melted but were oxidized. Close examination of the melted portion of the buss bar revealed small circular craters consistent with out-gassing of the copper while at its incipient melting temperature. No evidence of material transfer such as small beads of metal was observed in the area of melting such as would be expected if the damage had occurred due to electrical arcing. The other terminal studs and bus bars connected to the T2 and T3 terminals did not exhibit the same melting. No other areas of similar damage were observed on any other bus bars within the rest of the JB-1 unit.
Inside the top compartment of the junction box were two contactors, K1XB and K3XB. Both had sustained extensive thermal damage. The contactors were disassembled to examine the interior components. Although the internal components exhibited severe thermal damage, the contacts did not appear to be stuck or have signs of melting or excessive pitting. A portion of the case enclosing the internal components of the K1XB contactor appeared to have sustained more thermal damage on the inside surface than on the outside. This damage consisted of a portion of the case having melted and was surrounded by an area that appeared to have reached its incipient melting temperature. The internal surface of the case had a larger area of incipient melting than the external surface.
The three AC service bus connectors on the exterior of the JB-1 junction box were connected to heavy gauge cables. The three cables were insulated with color coded (white, orange, blue) insulation to differentiate them. The stack up of the hardware on the stud connectors was the following: Nut, lock-washer, flat-washer, lug, nut, lock-washer, flat-washer. Below the last washer there would have been a phenolic material that was consumed by the fire. No evidence of melting or arcing was observed on any of the cables, the stud connectors, or their hardware stackups.
Crew Oxygen System Fire Damage
The crew oxygen system consisted of three fixed installation oxygen masks; one for the captain, one for the first officer and one for a third crew person. The third crew person oxygen mask was installed in the top forward portion of the wardrobe unit. The oxygen mask units consisted of a stowage box within which the full face type oxygen mask was housed. The three masks were supplied oxygen by a high pressure cylinder located below deck in the E&E bay. The high pressure cylinder had a volume of 650 cubic inches and could hold 50 cubic feet of oxygen at a pressure of 1800 psi. The pressure indicator on the cylinder indicated 0 psi. The minimum dispatch pressure for the oxygen system would have been no less than 1400 psi. The cylinder pressure would be regulated down to 81 psi with a maximum flow of 132 lb/min, and the oxygen would be routed to the flight deck by rigid aluminum tubing. The connection between the aluminum tubing and the oxygen mask stowage boxes consisted of flexible oxygen hoses. The back of the third crew person oxygen mask stowage box was visible from the burnthrough in the fuselage. Upon removal of the third crew person oxygen mask stowage box, it was found that the flexible oxygen hose had been severed from the upstream end and only a charred portion of the flexible hose was still attached to the oxygen mask stowage box. The upstream fitting of the flexible hose was still attached at the threaded nipple on the end of the aluminum supply piping where the flexible hose would have been connected. A small piece of wire was attached to this fitting. The small piece of wire would have been part of the stainless steel coil internal to the flexible hose used to keep the hose from being crimped and restricting oxygen flow to the mask. The end of this small portion of wire had evidence of melting exhibited by a globule of resolidified metal.
Oxygen Mask Box Light Strip Fire Damage
The purpose of the light strip surrounding the third crew person oxygen mask box was to illuminate the location of the observer's supplemental oxygen mask stowage box. The light strip was found to have a kink along a portion of its perimeter. The area in which the kink was observed had also sustained thermal damage resulting in charring of the light strip. The char layer was removed and no evidence of melting or electrical arcing was found. The wiring did not exhibit any evidence of arcing.
Beginning on December 19, 2008, numerous electrical anomalies involving
the external AC power supply began to occur. These anomalies included the activation of an AC essential bus caution message, the activation of the AC service bus feed circuit breaker, and the cycling on and off of AC power while on external power. To attempt to remedy the anomalies, several relays, electrical contactors, the AC power switch, the external ground power receptacle, and other electrical components were removed and replaced with new components. Several of these components were located in the upper section of the JB-1 junction box. The last of these actions prior to the accident occurred on January 21, 2009.
And last, a review of the maintenance logbook pages from December 2008 to February 2009 revealed no systemic issues with the oxygen system of the airplane and no evidence of frequent oxygen bottle replenishment.
Following the accident, on March 12, 2009, Bombardier Aerospace issued All Operators Message (AOM) 1170 to its operators which described the basic facts regarding the accident.
On June 30, 2009, Bombardier issued Service Letter (SL)CRJ100/200/440-SL-35-005, which recommended that customers perform an inspection of the third crew member oxygen hose for general condition and security of attachment. This inspection was to be accomplished at the next convenient maintenance opportunity.
On July 7, 2009, Transport Canada issued Service Difficulty Alert (SDA) AL-2009-05, which echoed the recommendation in the earlier Bombardier Service Letter.
On October 20, 2009, the Federal Aviation Administration issued Special Airworthiness Information Bulletin (SAIB)NM-10-06. This SAIB also echoed the recommendation in the earlier Bombardier Service Letter.
On June 9, 2011, Bombardier issued Service Bulletin (SB) 601R-35-017A, which recommended that its customers replace and change the routing of the third crew member oxygen hose and to modify the associated entrance compartment panel assembly. This was to be accomplished no more than 4000 flight hours from the release date of the SB.
And on July 14, 2009, Transport Canada issued Airworthiness Directive (AD) CF-2011-23 to Canadian operators, which mandated the accomplishment of SB 601R-35-017A.