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 Bombard ier 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

### 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 Aeros pace 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 reques ts 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 cont ribute, 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 m eets 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, uncontroll able, 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-500-1A 11 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 extrem ely 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 abov e 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.