AEROSPACE 

Bombardier Inc. 

400 chemin de la Côte-Vertu West 

Dorval, Québec, Canada H4S 1Y9 

www.bombardier.com 

TEL 514-855-5000 

FAX 514-855-8436 

2016-01-13 

AW-BD5/15/570 

Subject: Petition for Exemption from section 14 CFR Part 25.901(c) for the Thrust 

Quadrant Assembly of the Bombardier Aerospace BD-500-1A10 and BD-500-

1A11(C Series CS100 and C Series CS300 respectively) aircraft model 

FAA Project No.: TC4948NY-T 

Manager, C Series Airworthiness 

Bombardier Aerospace 

glenn.jr.baxter@aero.bombardier.com

Enclosure

Mr. Serge Napoleon 

Program Manager 

New York Aircraft Certification Office, ANE-171 

Federal Aviation Administration 

1600 Stewart Avenue, Suite 410 

Westburry, NY 11590, USA 

Glenn Baxter 

Dear Mr. Napoleon,

In accordance with 14 CFR Part 11, Bombardier Aerospace (BA) respectfully submits this

petition for an exemption of the C Series aeroplane model BD-500-1A10 (CS100) and BD-500-

1A11 (CS300) from full compliance with 14 CFR 25.901(c) at amendment 131, Powerplant,

installation, to account for a certain extremely improbable throttle quadrant assembly (TQA)

failure that could contribute, under specific simultaneously converging conditions, to a UHT

event under very limited and specific takeoff and landing scenarios. Please see the enclosed

issue description for additional details.

If you have any questions or require any additional information please contact Glenn Baxter via

the contact information listed below.

Best regards,
Bombardier Airworthiness Coordination Sheet 

Subject: BA letter AW-BD5/15/570, titled “Petition for Exemption from section 14 

CFR Part 25.901(c) for the Thrust Quadrant Assembly of the Bombardier 

Aerospace BD-500-1A10 and BD-500-1A11(C Series CS100 and C 

Series CS300 respectively) aircraft model”, dated 2016-01-13. 

Reference(s): 1. Airworthiness – C Series Certification eRoom Action Item #4221. 

DISCIPLINE NAME APPROVAL DATE 

Powerplant DAD M. Danielson 

Powerplant DAD G. Armstrong 

Airworthiness Focal C. Rivera 

Airworthiness Focal J. Torres-Moreno 

Airworthiness Manager G. Baxter 

Digitally signed by Carlos Antonio Rivera

DN: cn=Carlos Antonio Rivera,

ou=Standard Users,

email=Carlos.Rivera@aero.bombardier.com

Date: 2016.01.12 10:12:31 -05'00'

Carlos Antonio

Rivera Geoffrey Armstrong

Digitally signed by Geoffrey Armstrong 

DN: dc=net, dc=bombardier, dc=aero, dc=aero, ou=Bombardier 

Aerospace, ou=CA, ou=Montreal, ou=Users, ou=Standard Users, 

cn=Geoffrey Armstrong, 

email=geoffrey.armstrong@aero.bombardier.com 

Date: 2016.01.12 10:29:29 -05'00'

Juan Torres-Moreno Digitally signed by Juan Torres-Moreno 

DN: cn=Juan Torres-Moreno 

Date: 2016.01.12 11:22:29 -05'00'

Digitally signed by Michael

Danielson

DN: cn=Michael Danielson

Date: 2016.01.14 15:22:18 -05'00'

Michael

Danielson

Digitally signed by Glenn JR Baxter

DN: cn=Glenn JR Baxter Glenn JR Baxter

Date: 2016.01.14 15:34:14 -05'00'
EXEMPTION REQUEST FORM

Petition for Exemption 

Bombardier Inc. 

Uncontrollable High Thrust Failure Conditions 

Model BD-500-1A10/1A11 

Relief from section 14 CFR Part 25.901(c) 

SUMMARY 

Sections of the Regulation Affected: 

14CFR §25.901(c) 

Description of Relief Sought: 

Permanent Exemption of Bombardier Aerospace BD-500-1A10 and BD-500-1A11 Aircraft from 

the 14CFR § 25.901(c) requirement as it relates to the TQA (Throttle Quadrant Assembly) 

single failure that can lead to uncontrollable high thrust (UHT) failure conditions. 

Text of Requirement for which Exemption is Sought: 

14 CFR §25.901 "Installation" 

(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. 
EXEMPTION REQUEST FORM

Bombardier Aerospace (BA) respectfully requests a permanent exemption to Federal Aviation 

Regulation (FAR) Part 25.901(c) of CFR Title 14, for a certain extremely improbable throttle 

quadrant assembly (TQA) failure that could contribute, under specific simultaneously converging 

conditions, to a UHT event under very limited and specific takeoff and landing scenarios of the 

BD-500-1A10 and BD-500-1A11(C Series CS100 and C Series CS300, respectively). 

The exemption is requested for a permanent period after FAA type validation. Due to the small 

(single) number of failures within the TQA, the limited window of exposure, and the practicality 

of redesigning the TQA (which currently meets the industry norms), BA believes permanent 

relief from 14CFR 25.901 (c) relative to the TQA is appropriate. Furthermore, BA understands 

precedent exists with the FAA for this relief, most recently with FAA Exemption number 10614. 

Justification 

BA has shown in the position to FAA Issue Paper P-25 that the overall level of safety of the 

thrust control system of the C Series CS100 and CS300 will not be less than that of the current 

BA transport category aircraft fleet. The BA fleet of FADEC-equipped aircraft have more than 16 

million aircraft flight hours. This fleet has never had a TQA failure leading to an UHT event. Full 

compliance with 14 CFR 25.901(c), as per the FAA interpretation, would require the introduction 

of novel design features to the BD-500-1A10 and BD-500-1A11. 

It is recognized that experience over the past few years has demonstrated that some design 

solutions can safely and reliably eliminate the possibility of a single failure or combination of 

failures leading to a UHT event. BA has introduced a thrust control malfunction accommodation 

feature into the engine electronic control to address engine failures that may lead to a UHT 

event that will eliminate all noncompliant, uncontrollable, high-thrust failures, except for a very 

specific case related to the drive train failure of the TQA under a high speed Rejected Take-off 

(RTO) operation. 

 

Introducing a more complex design into the TQA assembly, with the intent of eliminating the 

single failure, will introduce more components to the assembly, increasing the probability of 

failure and being counterproductive to both BA and FAA’s goal of continuous improvement in 

overall aircraft reliability and safety. Such design changes may minimize drive train failures, but 

would not eliminate the more likely events of a jammed control(s) due to foreign objects, both 

within the control and externally from items on the flight deck. 

Issue of Public Interest 

A thrust control system design change that would keep the aircraft controllable for all UHT 

single system failures would require modifications to the current TQA. Implementing this 

redesign would prevent BA from certifying the C Series CS100 and CS300 design in a timely 

and competitive schedule, putting it in an unfair disadvantage to its competitors and directly 

affecting its US customers. 

Additionally, requiring the BD-500-1A10 and BD-500-1A11 models to fully comply with this rule, 

as per the FAA interpretation, would adversely affect US companies involved in the design and 

production of the aircraft. 

 
EXEMPTION REQUEST FORM

Effect of the Exemption on Safety 

As stated above, and as previously demonstrated to the FAA by analysis, the risks due to UHT 

failure conditions on the BD-500-1A10 & BD-500-1A11 aircraft will not exceed those of the 

current BA transport category aircraft fleet, nor the currently known and comparable existing 

transport category airplanes. 

The conditions under which a UHT failure may jeopardize the safe operation of the airplane are 

limited to specific conditions during takeoff and landing scenarios. The majority of these 

scenarios are addressed by the engine thrust control malfunction accommodation feature. A 

UHT event, due to a single failure in the TQA, has a very low risk per flight hour, many orders of 

magnitude less than that accepted as extremely improbable. The BA TQA’s have never had a 

disconnect of the drive train between the control lever and the throttle position resolvers. Such a 

failure will be less than extremely remote. 

The BA assessment is that the TQA failure would only become a hazard when associated with 

a high speed RTO. The BA assessment shows that an RTO is an independent event from the 

TQA failure. A high speed RTO not associated with another aircraft failure is remote (i.e. due to 

birds or aircraft failure to clear an active runway < 1E-05). Additionally, in the event of an 

occurrence, there is limited risk that any serious injury will result. 

Waiver of Notice and Public Procedure 

BA respectfully requests that action on this petition should not be delayed by publication and 

comment procedures. BA believes that the proposed extended analysis of the current design, 

required for the suppression of the TQA single failure, justifies this request. 

Conclusion 

Bombardier Aerospace believes that the above arguments favor a permanent exemption from 

14 CFR 25.901(c) for the TQA for the C Series 100 and C Series 300 aircraft. Additionally, BA 

believes that any risks due to a UHT failure condition generated by the TQA single failure case 

on the C Series 100 and C Series 300 will not exceed that of comparable existing transport 

category airplanes and that an exemption is in the public interest. BA requests that the 

privileges of this exemption would apply outside the United States due to the transoceanic 

capability of the C Series 100 and C Series 300 aircraft and the character of mission for many of 

our operators.