Water Leaking Into Avionics Bay May Cause Electrical Short, Fire

A series of fires aboard Bombardier CRJ-200 aircraft has prompted the National Transportation Safety Board to issue seven recommendations to the Federal Aviation Administration.  Four of the recommendations are classified "Urgent" by the Safety Board.

The recommendations follow seven fires aboard CRJ-200 aircraft, six of them within the last six months. Although none of them has resulted in loss of life, "the potential exists for an uncontained fire to compromise the oxygen line, which could develop into an even more critical situation," the Board stated in its letter to the FAA.

All the fires have involved the Ultem 2200 surface material of the 1K4XD contactors aboard the planes (The contactor is a switching device for three-phase AC electrical power generated by each of the two engine-mounted 30KVA electrical generators.). Four of the fires resulted in at least temporary loss of all Electronic Flight Information System (EFIS) displays, preventing the pilots from using their primary flight instruments and increasing their workload during an emergency situation.

"The problems identified in the Board's letter must be corrected as soon as possible," NTSB Acting Chairman Mark V. Rosenker said. "The potential consequences of these fires can be catastrophic."

The NTSB wants the FAA to require CRJ-200 operators to provide separation of electrical power sources to prevent the simultaneous loss of all EFIS displays, require Bombardier to develop a means of protecting electrical terminals on these contactors from moisture-induced short circuits, require operators to install that protection once developed, and require Bombardier immediately to evaluate existing abnormal and emergency procedures for the CRJ-200 airplane to determine whether they adequately address these fire hazards. All four of these recommendations were classified by the Board as urgent.

Safety Board investigators found the cause of these contactor failures and fires. Various forms of precipitation were present before the departure of each incident flight and when the main cabin door is open on the CRJ-200, the forward cabin floor is exposed to the weather. Water on the floor can then seep into the avionics compartment below, where the contactor is located. Pulling the main entry door into the closed position may also result in water draining into the cabin area and subsequently into the avionics compartment. The Board found that there are two versions of the 1K4XD contactor approved for the CRJ-200 airplanes; only the newer version, which uses Ultem 2200 material, has exhibited this fire problem and is the subject of these recommendations.

Aside from the four urgent recommendations, the other recommendations contained in the same letter deal with replacement of these contactors and other components manufactured with Ultem 2200 (polyetherimide) or similar material, and with ensuring the safety from fire risk for any other electrical components on Bombardier aircraft.

The texts of the recommendations to the FAA are:

• Immediately require operators to provide separation of electrical power sources in CRJ-200 airplanes to prevent the potential loss of electronic flight instrument system displays that may result from contractor failures. (A-06-29) Urgent
• Require Bombardier to develop a means of protecting electrical terminals on Tyco Hartman 1K4XD contractors fitted with Ultem 2200 (polyetherimide) terminal bases from moisture-induced short circuits. (A-06-30) Urgent
• Once Bombardier has developed a means to protect electrical terminas on Tyco Hartman 1K4XD contractors fitted with Ultem 2200 (polyetherimide) terminal bases a recommended in Safety Recommendation (2), require operators to install the protection as soon as possible. (A-06-31) Urgent
• Require Bombardier to expedite the replacement of 1K4XD contactors on CRJ-200s with contactors that are not susceptible to short circuit. (A-06-32)
• Require Bombardier to demonstrate the capability of electrical components to safely tolerate exposure to moisture or conductive fluids under full electrical load when such components may be inadvertently exposed to such conditions. (A-06-33)
• Require all airplane manufactures to determine whether any electrical components on their aircraft are manufactured with Ultem 2200 (polyetherimide) or similar material with arc-tracking characteristics and require removal or protection of these components to prevent potential fires. (A-06-34)
• Require Bombardier to immediately evaluate existing abnormal and emergency procedures for the CRJ-200 airplane to determine whether they adequately address the fire hazard presented by the failure of the 1K4XD contractor and provide flight crew with additional guidance as needed. (A-06-35) Urgent

FMI: Read The Full Text Of The NTSB Letter (pdf)