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Safety Recommendation Details

Safety Recommendation A-16-003
Details
Synopsis: On March 11, 2016, the National Transportation Safety Board (NTSB) adopted our safety recommendation report concerning a June 5, 2015, incident in which United Express flight 4776, a Bombardier DHC-8-202 airplane, experienced an in-flight fire at the right windshield terminal block while on approach to Bradley International Airport, Windsor Locks, Connecticut.
Recommendation: TO BOMBARDIER, INC.: Redesign the windshield heat power connection for all Bombardier DHC-8 airplanes to provide a mechanically secure, low-resistance electrical connection.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Unacceptable Action
Mode: Aviation
Location: Windsor Locks, CT, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: ENG15IA024
Accident Reports: Safety Recommendation Report: Preventing Windshield Arcing, Smoke, and Fire on Bombardier DHC-8 Airplanes
Report #: ASR-16-001
Accident Date: 6/5/2015
Issue Date: 4/12/2016
Date Closed: 7/17/2018
Addressee(s) and Addressee Status: Bombardier, Inc. (Closed - Unacceptable Action)
Keyword(s):

Safety Recommendation History
From: NTSB
To: Bombardier, Inc.
Date: 7/17/2018
Response: We note that you do not plan to redesign the method of terminating the connections on the windshield terminal block in your DHC-8 airplanes. Instead, you have revised your task cards to emphasize inspecting connections to identify those that could result in electrical arcing at the windshield terminal block and to ensure a conformal/potting compound is applied to prevent the connections from becoming loose. We disagree that this action satisfies Safety Recommendation A-16-3, and we continue to believe that arcing and fire incidents at the windshield heat terminal on DHC 8 airplanes could be reduced if a different type of windshield/heat power connection was used that precluded loose connections. However, because you do not plan to take the action we requested in Safety Recommendation A-16-3, it is classified CLOSED--UNACCEPTABLE ACTION.

From: Bombardier, Inc.
To: NTSB
Date: 6/12/2018
Response: -From David Fisher, Director, Bombardier Commercial Aircraft, ASIO (Air Safety Investigation Office): A-16-3 “Redesign the windshield heat power connection for all Bombardier DHC-8 airplanes to provide a mechanically secure, low-resistance electrical connection. We note that you have issued Service Bulletin (SB) 8-30-41, which provides instructions to retorque the electrical connections on the windshield terminal block and apply a potting compound to prevent connections from becoming loose. However, it appears that the specified material is a conformal coating and not a potting compound, and the conformal coating will not address our concern. We are also concerned that the SB does not specify repetitively torqueing the screws. In addition, we are not aware of any testing that demonstrates that the potting compound will prevent the screws from loosening over time”. Bombardier Response: As previously corresponded, Humiseal was recommended by the Windshield manufacturer as a means to help the integrity of the connections on the windshield terminal block. We have used this product on other Bombardier aircraft and have had no incidents on the other aircraft to ones seen on the Q series aircraft, therefore Bombardier views the application of the Humiseal as a definite improvement to the integrity of the terminal block connections. You are correct in pointing out that the Task cards do not address specifically re-torquing the terminals of the terminal block. Bombardier is proposing to the operators and TCCA to revise the Task cards to ensure that the retorquing and application of the Humiseal is repeated. “In our letter issuing this recommendation, we discussed two events that occurred in January 2004 involving a similar issue of arcing and fire at the windshield heat terminal on Boeing 757 airplanes. During our investigation of those events, Boeing indicated that the terminal block on Boeing 747, 757, 767, and 777 airplanes had been redesigned to incorporate a pin/socket connector, instead of a screw, to connect the airplane electrical system to the windshield heat system. Boeing incorporated the connector into new production airplanes in mid-2004 and issued SBs to retrofit existing airplanes. Incidents of fire near the windshield heat terminal on these airplanes subsequently stopped. We continue to believe that incidents of arcing and fire at the windshield heat terminal on DHC-8 airplanes could be reduced if a different type of windshield/heat power connection was used that precluded the incidence of loose connections. Therefore, we encourage you to develop an improved design that ensures a mechanically secure, low-resistance electrical connection. In the meantime, pending our receipt of a plan that responds to this concern, Safety Recommendation A-16-3 is classified “Open—Unacceptable Response.” Bombardier Response: At this time Bombardier has no plans to redesign the method of terminating the connections on the windshield terminal Block. Our proposed new tasks to inspect the connections were instituted to address possible poor connection that could result in electrical arcing at the windshield terminal block

From: NTSB
To: Bombardier, Inc.
Date: 4/20/2018
Response: We note that you have issued Service Bulletin (SB) 8-30-41, which provides instructions to retorque the electrical connections on the windshield terminal block and apply a potting compound to prevent connections from becoming loose. However, it appears that the specified material is a conformal coating and not a potting compound, and the conformal coating will not address our concern. We are also concerned that the SB does not specify repetitively torqueing the screws. In addition, we are not aware of any testing that demonstrates that the potting compound will prevent the screws from loosening over time. In our letter issuing this recommendation, we discussed two events that occurred in January 2004 involving a similar issue of arcing and fire at the windshield heat terminal on Boeing 757 airplanes. During our investigation of those events, Boeing indicated that the terminal block on Boeing 747, 757, 767, and 777 airplanes had been redesigned to incorporate a pin/socket connector, instead of a screw, to connect the airplane electrical system to the windshield heat system. Boeing incorporated the connector into new production airplanes in mid-2004 and issued SBs to retrofit existing airplanes. Incidents of fire near the windshield heat terminal on these airplanes subsequently stopped. We continue to believe that incidents of arcing and fire at the windshield heat terminal on DHC-8 airplanes could be reduced if a different type of windshield/heat power connection was used that precluded the incidence of loose connections. Therefore, we encourage you to develop an improved design that ensures a mechanically secure, low-resistance electrical connection. In the meantime, pending our receipt of a plan that responds to this concern, Safety Recommendation A-16-3 is classified OPEN--UNACCEPTABLE RESPONSE.

From: Bombardier, Inc.
To: NTSB
Date: 12/14/2017
Response: -From David Fisher, Manager, Air Safety Investigations Office (ASIO): Bombardier has issued Service Bulletin 8-30-41 to address this issue. The SB provides instructions to re-torque the electrical connections on the windshield terminal block and apply a potting compound (sealant) to prevent connections from becoming loose. Incorporation of the SB is mandated by Transport Canada, Airworthiness Directive, CF-2017-25, (AD attached)

From: NTSB
To: Bombardier, Inc.
Date: 10/4/2017
Response: We are interested in knowing whether and how our recommendations are implemented, both to ensure that the traveling public is provided the highest level of safety and to identify creative solutions that might be shared with others. We normally expect actions to address our recommendations to be completed within 3 to 5 years, and we have yet to hear from you regarding your progress toward addressing these recommendations. We would appreciate receiving a response within 90 days indicating any actions you have taken or plan to take to implement these recommendations; until then, they will retain their current classification of OPEN—AWAIT RESPONSE. For additional background information about these safety recommendations, please refer to Safety Recommendation Report 16-01, Preventing Windshield Arcing, Smoke, and Fire on Bombardier DHC-8 Airplanes. Please update us at correspondence@ntsb.gov regarding your actions to address Safety Recommendations A-16-3 through -8, and do not submit both an electronic and a hard copy of the same response.