UNITED STATES OF AMERICA 

DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

RENTON, WASHINGTON 98057-3356 

In the matter of the petition of 

Exemption No. 16779 

Bombardier Aerospace Regulatory Docket No. FAA-2016-4198 

for an exemption from§ 25.981(a)(3) of 

Title 14, Code of Federal Regulations 

GRANT OF TIME-LIMITED EXEMPTION 

By letters dated February 18,2016, and April4, 2016, Mr. Glenn Baxter, C Series Airworthiness 

Manager, Bombardier Aerospace (Bombardier), 400 Cote-Vertu Road West, Dorval, Quebec, 

H4S 1 Y9, Canada, petitioned the Federal Aviation Administration (FAA) for a time-limited 

exemption from the requirements of§ 25.981(a)(3) of Title 14, Code of Federal Regulations 

(14 CFR). This exemption, if granted, would allow Bombardier 3 years after type validation to 

incorporate necessary design changes to the fuel boost pump on Model BD-500-1A10 and Model 

BD-500-1A11 airplanes in order to fully comply with 14 CFR 25.981(a)(3). 

The petitioner requests relief from the following regulations: 

Section 25.981(a)(3)- No ignition source may be present at each point in the fuel tank or 

fuel tank system where catastrophic failure could occur due to ignition of fuel or vapors. 

This must be shown by demonstrating that an ignition source could not result from each 

single failure, from each single failure in combination with each latent failure condition 

not shown to be extremely remote, and from all combinations of failures not shown to be 

extremely improbable. The effects of manufacturing variability, aging, wear, corrosion, 

and likely damage must be considered. 
Section 25.901(c)*- For each powerplant and auxiliary power unit installation, it must be 

established that no single failure or malfunction or probable combination of failures will 

jeopardize the safe operation of the airplane except that the failure of structural elements 

need not be considered if the probability of such failure is extremely remote. 

Related section of 14 CFR: 

Section 25.1309 states, in pertinent part, that required equipment, systems, and 

installations must be designed to ensure that they perform their intended functions under 

any foreseeable operating condition and that the occurrence of any failure condition that 

would prevent the continued safe flight and landing of the airplane is extremely 

improbable. 

The petitioner supports its request with the following information: 

This section quotes the relevant information from the petitioner's request, with minor edits for 

clarity. The complete petition is available at the Department of Transportation's Federal Docket 

Management System, on the Internet at http://regulations.gov, in Docket No. FAA-2016-4198. 

Description of Relief Sought 

Bombardier respectfully requests a time-limited exemption to 14 CFR 25.981(a)(3) as it 

relates to the fuel alternating current (AC) boost pump design on the BD-500-1 A 10 and 

BD-500-1A11 (C Series CS100 and C Series CS300, respectively); in particular, where 

the regulation states to consider "aging, wear, corrosion, and likely damage." 

The exemption is requested for a 3-year period after FAA type validation. Due to the 

impracticality of quick redesign to include a ground fault interrupter (GFI) or a fast-acting 

arc fault protection, Bombardier believes temporary relief from§ 25.981(a)(3) relative to 

the fuel boost pump is appropriate. The design change will be introduced into 

production. Furthermore, Bombardier understands precedent exists with the FAA for this 

relief, most recently with FAA Exemption No. 11321. 

Justification 

Bombardier has described the details in FAA Issue Paper P-32 where the AC boost pump 

design is claimed to meet dual fault tolerant methodology. Full compliance with 

§ 25.981(a)(3) will require introduction of a GFI or a fast-acting arc fault circuit 

protection device. Bombardier strongly believes that the AC boost pump design as 

outlined in Issue Paper P-32 at Stage 3, fully demonstrates that the design is robust with 

• The petitioner did not request relief from § 25 .90 I (c) which is a general powerplant installation requirement. 

Compliance with § 25.981 (a)(3) requires an analysis of the fuel tank system using the same analytical methods and 

documentation required by§ 25.90 l(c). Prior to the promulgation of§ 25.981 , industry had not been consistently 

evaluating single failures in combination with latent failures. In order to eliminate ambiguity, § 25.981 (a)(3) 

explicitly requires that latent failures be assumed unless they are extremely remote. For that reason, this exemption 

provides time-limited relief from § 25.90 I (c) in addition to time-limited relief from § 25.981 (a)(3). 

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many redundant ignition protection features to prohibit any single failure, from each 

single failure in combination with each latent failure condition, and from all combinations 

of failures to not be a threat to fuel tank ignition. At this time, Bombardier is assessing 

and evaluating potential design solutions to incorporate a GFI or a fast-acting arc fault 

circuit protection device into the AC boost pump external electrical wiring of the 

BD-500-1A10 and BD-500-1A11 in order to fully comply to§ 25.981(a)(3). 

Issue of Public Interest 

Since the incorporation ofthis additional feature is in development, this prevents 

Bombardier from certifying the Model BD-500-1A1 0 and BD-500-1A11 designs within a 

timely and competitive schedule, putting the product at an unfair disadvantage. This will, 

in due course, directly impact potential customers in the United States (US) as well as 

Bombardier US suppliers which are heavily involved in the development of these 

airplanes. 

Bombardier's current design has been certified by Transport Canada during the baseline 

certification program for the C Series CS 100 aircraft. The identified FAA concerns 

require significant aircraft utilization and/or aging to potentially develop into a noncompliant condition. The AC boost pump is not used continuously and therefore, the 

timeframe proposed for this exemption is not sufficient for the affected airplanes to 

accumulate the flight hours or cycles required for the components to exhibit these aging 

effects. 

Effect of the Exemption on Safety 

While issuing an exemption implies a lower standard of safety, Bombardier believes that 

the pump as designed is more robust and better suited to preventing ignition sources than 

those currently installed on thousands of aircraft that were not required to meet the 

requirements of§ 25.981(a)(3) at Amendment 25-125. Therefore, Bombardier believes 

there will not be a negative impact on the current level of safety. Furthermore, the robust 

design ofthe BD-500-1A10 and BD-500-1A11 fuel boost pumps, in comparison to that 

of in-service aircraft not meeting the standards of§ 25.981(a)(3) at Amendment 25-125, 

will result in an increase in safety. In addition, the time-limited nature of this exemption 

will ensure that the number of airplanes delivered is negligible to the overall fleet risk. 

Conclusion & Request to Extend Privilege of Exemption Outside the United States 

Bombardier believes that the above arguments favor a time-limited exemption from 

§ 25.981(3)(3) regarding fuel tank ignition for the BD-500-1A1 0 and BD-500-1A11 

airplanes. Additionally, Bombardier believes that any risk due to a fuel tank ignition is 

mitigated by the multiple safety features that Bombardier has incorporated (as defined in 

Issue Paper P-32). The AC boost pump failure condition on the subject airplanes will not 

exceed that of comparable existing transport category airplanes and an exemption is in the 

public interest. Bombardier requests that the privileges of this exemption apply outside 

the United States due to the transoceanic capability ofthe BD-500-1A10 and 

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BD-500-1A11 airplanes and the character of mission for many of our operators. 

Federal Register publication 

Although the petitioner requested that action on its petition not be delayed for publication in the 

Federal Register, the FAA found that the petition, if granted, would set a precedent. Therefore, 

to allow an opportunity for the public to comment on the petition, a summary of it was published 

in the Federal Register on April27, 2016 (81 FR 24932). No comments were received. 

The FAA's Analysis 

Introduction 

Bombardier has requested relief from the requirements of§ 25.981(a)(3) as it pertains to the AC 

fuel boost pump installation of the Model BD-500-1 A 10 and Model BD-500-1 A 11 airplanes for 

a period of 3 years. Bombardier states that they need 3 years to design and certify a fuel boost 

pump installation that includes GFI in order to fully comply with the requirements of 

§ 25.981(a)(3). Bombardier also states that they will provide service information to 

accommodate a retrofit of the US fleet of airplanes within the 3-year timeframe. Bombardier 

contends that the fuel boost pump design is robust and complies with§ 25.981(a)(3) because of 

many redundant ignition protection features to prohibit single failures, single failures in 

combination with each latent failure condition, and all combinations of failures from becoming a 

threat to fuel tank ignition. They state that the robust design of the fuel boost pump in 

comparison to those in service that were not required to comply with§ 25.981(a)(3) will result in 

an increase in safety and that the time-limited exemption will ensure that the number of airplanes 

delivered with the non-compliant design is negligible to the overall fleet risk. 

Bombardier mentions that a precedent exists in Exemption 11321, issued to Airbus, for granting 

temporary relief from§ 25.981(a)(3). The FAA does not agree that Exemption 11321 sets a 

precedent for the Bombardier fuel boost pump redesign because Exemption 11321 grants relief to 

a fuel boost pump design that already includes a GFI and only an estimated 5 airplanes would be 

delivered in a non-compliant configuration. That number of airplanes is considerably less than 

the number of airplanes Bombardier estimates they will deliver during the 3-year exemption 

period. 

However, the FAA has granted time-limited exemptions specifically for certain AC fuel boost 

pump installations to allow applicants time to design and install GFI. Time-limited Exemption 

8761C, issued to Hawker Beechcraft Corporation on September 30, 2009, grants an extension to 

an existing exemption to allow the applicant to design and certify a GFI and develop service 

information for retrofit of the existing fleet of affected airplanes. 

Public Interest & Effect on Safety 

The petitioner must show that the granting of this request for exemption is in the public interest 

per § 11.81 (d). The FAA agrees with Bombardier that there would be adverse impacts on US 

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interests, including airplane operators and component manufacturers, as a result of delaying 

approval of a type certificate for the BD-500-1 A 10 and BD-500-1A 11 airplanes for 3 years while 

Bombardier redesigns the fuel boost pump. 

In their petition dated February 18,2016, Bombardier proposed to design a GFI or fast-acting arc 

fault circuit protection. However, Bombardier later provided additional information on April 4, 

2016, indicating that they will design and install a GFI to disconnect power to the fuel boost 

pump in the event of a ground fault present in the fuel boost pump or the pump power wire. 

Bombardier stated that the GFI will not contain any software or complex hardware and that 

inadvertent operation of the GFI would be an active failure, preventing fuel boost pump 

operation. 

Bombardier also proposes to include an inspection of the GFI at an agreed upon interval to 

reduce the exposure to a latently failed GFI. Bombardier explains that inadvertent activation of 

the GFI would be an active failure because the pump operates every flight. However, inadvertent 

activation of the GFI that prevents fuel boost pump operation does not directly affect compliance 

with§ 25.981(a)(3). The FAA is concerned that a latent failure ofthe GFI may result in a failure 

to remove power from the fuel boost pump in the event of a ground fault which may result in fuel 

tank ignition. 

Compliance with§ 25.981(a)(3) requires applicants to perform a safety analysis and account for 

the effects of manufacturing variability, aging, wear, corrosion, and likely damage of each 

component of the fuel tank or fuel tank system. That analysis often results in the need for 

reliable fast-acting circuit protection to prevent an undetected ground fault and resultant fuel tank 

ignition. Service history of fuel pumps has shown that safety features (e.g., explosion-proof 

cavities, robust connectors, insulated wires) are particularly susceptible to the effects of aging, 

wear, corrosion, and damage which has typically resulted in requiring applicants to show that the 

failure of the GFI is extremely remote or by limiting the latency period of a failed GFI by 

performing a daily check. 

Bombardier states that they will deliver a limited number of airplanes within the 3-year time 

period ofthe exemption and have estimated that number to be approximately 145 to 155 

airplanes; 30 of those airplanes will be operating in the US. A provision of this exemption 

requires Bombardier to provide service information, including all associated instructions for 

continued airworthiness required by§ 25.981(d) to ensure operators incorporate the new fuel 

boost pump design into their existing fleet. The retrofit requirement affects an estimated 30 

airplanes that will be delivered to US operators prior to the incorporation of the compliant fuel 

boost pump with GFI design into production. 

The airplanes delivered in the non-compliant condition will be operated for a limited time and 

are not anticipated to develop the failure conditions that may result in fuel tank ignition during 

that limited time period. These airplanes are expected to provide a level of safety equal to or 

better than much of the existing transport category fleet. 

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Based on the service history of existing fleets and the limited time in which the new airplanes 

will be allowed to operate under this exemption, the risk to safety within the US fleet is very low. 

Therefore, we have concluded that this time-limited exemption will not adversely affect safety. 

The FAA has reviewed the information provided by Bombardier and acknowledges that 

incorporating a GFI into the AC fuel boost pumps installed on the BD-500-1 A 10 and 

BD-500-1A11 airplanes should support compliance by preventing single failures, single failures 

plus latent failure conditions not shown to be extremely remote, and all failures not shown to be 

extremely improbable that may result in fuel tank ignition. 

The FAA's decision 

In consideration of the foregoing, I find that a grant of time-limited exemption is in the public 

interest. Therefore, pursuant to the authority contained in 49 U.S.C. 40113 and 44701 delegated 

to me by the Administrator, I grant Bombardier Aerospace an exemption from 14 CFR 25.901(c) 

and 25.981(a)(3) as it pertains to fuel tank ignition prevention associated with the fuel boost 

pump on the Model BD-500-1A10 and BD-500-1A11 airplanes until July 31,2019. I grant the 

exemption to the extent necessary to allow Bombardier Aerospace time to incorporate into 

production a GFI in the fuel system design so that it is fully and directly compliant with 

§§ 25.901(c) and 25.981(a)(3). 

This exemption is subject to the following conditions: 

1. Bombardier Aerospace will develop a comprehensive plan and schedule for compliance 

and present them to the FAA within 90 days after issuance of the BD-500-1A10 and 

BD-500-1A11 US type certificate. 

2. Bombardier Aerospace will complete the fuel boost pump safety analysis, including a 

structured failure modes and effects analysis, and provide documentation to show 

compliance with§ 25.901(c) at Amendment 25-126 and§ 25.981(a)(3) at Amendment 

25-125, and submit to the FAA for approval on or before July 31, 2017. 

3. Airplanes for which the original airworthiness certificate is issued after July 31,2019, 

must incorporate a GFI in the AC fuel boost pump power supply. The GFI must include a 

daily test to insure the GFI is functioning properly; or alternatively, Bombardier may 

show that failure of the GFI to remove power from the fuel boost pump in the event of a 

ground fault is extremely remote. 

4. On or before July 31,2019, Bombardier must develop and submit for FAA approval, 

service information for incorporating all design changes and airworthiness limitations to 

meet the provisions of§ 25.901(c) at Amendment 25-126 and§ 25.981(a)(3) at 

Amendment 25-125, as required by§ 25.981(d). 

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5. The airworthiness limitations section of the instructions for continued airworthiness must 

state that airplanes that received their original airworthiness certificate on or before 

July 31,2019, cannot be operated after July 31,2021, unless all design changes and 

limitations developed in accordance with condition 4 above are incorporated by the 

owner or operator. 

6. The FAA will not issue original airworthiness certificates for Bombardier Model 

BD-500-1A10 and BD-500-1A11 airplanes after July 31,2019, unless the newly 

produced airplanes conform to the modified type design, incorporating GFI, which 

directly complies with§§ 25.901(c) and 25.981(a)(3). 

Issued in Renton, Washington, on June 9, 2016. 

Michael Kaszycki 

Assistant Manager, Transport Airplane Directorate 

Aircraft Certification Service 

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