Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NM-18-32 R1
March 22, 2021
This is information only. Recommendations
aren’t mandatory.
Introduction
This revised Special Airworthiness Information Bulletin advises
registered owners and operators of Bombardier, Inc., Model BD-100-1A10
(Challenger 300 and Challenger 350) airplanes of the potential for
malfunctions of the Direct Current Power Center (DCPC) unit.
The FAA anticipates additional rulemaking under Title 14 of the Code of
Federal Regulations (14 CFR) part 39 to address the potential for
malfunctions of the DCPC unit. The documents referenced in this SAIB
are recommendations from the design approval holder and are not FAA
mandatory requirements.
Background
This revision is being issued to notify flight crews of the
instructions in Bombardier Inc. Airplane Flight Manual (AFM) Revision
58 (Challenger 300) and AFM Revision 24 (Challenger 350), and the Quick
Reference Handbook (QRH), Volume 2, Revision 58 (Challenger 300) and
Revision 24 (Challenger 350) to prevent the reset of active DC
source(s) during an electrical system misleading indication(s) event as
the reset of DC source(s) in such condition might worsen the situation
due to potential malfunctions of the Direct Current Power Center (DCPC)
unit.
Operators of Bombardier, Inc., Model BD-100-1A10 (Challenger 300)
airplanes reported erratic electrical status indications on the
push-button annunciators and the engine instrument and crew alerting
system; in some cases, the malfunction of the DCPC, which provides
electrical power to the avionics equipment on the airplane, caused
momentary loss of electrical power and loss of flight displays. These
malfunctions were attributed to the printed circuit board (PCB)
inserted in the DCPC. The PCBs are susceptible to movement within the
DCPC as a result of the installation design, and this movement resulted
in the loss of communication between the PCB and the DCPC motherboard.
Zodiac Aerospace, which manufactured the applicable DCPCs, issued
Service Bulletins 320GC03Y-24-012, 970GC02Y-24-013, and
975GC02Y-24-013, Revision 03, all dated December 15, 2012, to provide
procedures for modifying DCPC units manufactured by Zodiac Aerospace.
Bombardier issued Service Bulletin 100-24-23, dated November 26, 2012,
and Revision 01, dated March 2, 2015, to provide procedures for
reworking the DCPC system; the Bombardier service information also
refers to the Zodiac Aerospace Service Bulletins as a secondary source
of service information.
On February 26, 2014, the FAA issued Airworthiness Directive
2014-05-23, Amendment 39-13528, which requires modification of the
DCPCs to address loss of electrical power, which could result in the
loss of flight displays and reduced controllability of the airplane.
Although the actions in the referenced service information and the AD
have been done, none of these corrective actions have resolved the DCPC
PCB issues. Inspections of the modified DCPC units revealed that the
modification is ineffective.
The FAA requested the assistance of Transport Canada Civil Aviation
Authority (TCCA) for resolution of the issues identified. A vendor
investigation in early 2019 to address these new cases has recently
been completed, with the following root cause identified: The presence
of silicon, iron, organic fiber, aluminum, calcium, sodium and titanium
residues were found in several left-hand (LH) DCPCs removed for
misleading indications. Further testing confirmed that the accumulation
of these residues on the LH DCPC parallel data bus circuitry corrupts
its data. On-aircraft testing performed at TCCA’s Montreal facilities
in January 2020 validated this finding and duplicated the same
electrical system misleading indications when corrupting the LH DCPC
parallel data bus. The removal of these residues from inside the LH
DCPC would resolve this condition. Due to the DCPC’s complexity, and to
ensure the effectiveness of the cleaning, the deep cleaning can only be
performed at vendor facilities. Bombardier is currently validating the
cleaning procedure with the vendor and reviewing the logistical aspect
of an upcoming dedicated campaign, which will include planning for
replacement units.
Recommendations
The FAA recommends that all owners and operators of the affected
airplanes review the information and incorporate the actions outlined
in Bombardier Advisory Wire (AW), AW300-24-0141, Revision 04, dated
November 26, 2020.
The FAA requests that any case of misleading indication(s) of the DCPC
be reported to Bombardier (as identified below). Under the provisions
of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.), the Office of
Management and Budget (OMB) has approved the information collection
contained in this SAIB, and assigned OMB Control Number 2120-0731.
For Further Information Contact
Steven Dzierzynski, Aerospace Engineer, Avionics & Electrical
Systems Section, AIR-7H2, FAA, New York ACO Branch, 1600 Stewart
Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7367; fax:
(516) 794-5531; email: steven.dzierzynski@faa.gov.
For Related Service Information Contact