Petition for Exemption

Bombardier Inc.

Uncontrollable High Thrust Failure Conditions

Model BD-100-1A10

Relief from section 14 CFR Part 25.901(c)

SUMMARY

Sections of the Regulation Affected :

14CFR §25.901(c)

Description of Relief Sought :

Time Limited Exemption of Bombardier BD -100-1A10 Aircraft from the 14CFR § 25.901(c) requirement as it relates to certain extremely remote uncontrollable high thrust 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.June 20, 2014 AW-BD1/14/435

Bombardier Aerospace respectfully requests a time limited exemption to the Federal Aviation Regulation (FAR) Part 25.901(c) of Title 14, CFR, for certain extremely improbable powerplant failures that could affect, under determined simultaneously converging conditions, a very limited portion of the flight envelope of the impr oved Bombardier BD-100-1A10 equiped with the Honeywell AS907-2-1A engine, also known as Challenger 350.

The exemption is required for a period of 4 years after FAA validation. During this period, Bombardier and Honeywell will develop and make available an improved Uncontrollable High Thrust (UHT) logic which will mitigate the e ffects of an UHT event. The improvement will be certified prior to the expiration of the time frame specified above and will be implemented in all production aircraft incorporating the AS907-2-1A engine. The nature of this petition for exemption is similar to previously granted exemptions for the Airbus models A340-500, A340-600, the Embraer models EMB-135BJ, EMB145XR, the Boeing model 757-300 and 777’s and the Gulfstream Models G150, G-1159, G-IV, GV, GV-SP and G280.

Justification

Bombardier has shown in the position to the TCCA Issue Paper P-01 that the overall level of safety of the thrust control system of the Challenger 350 will not be less than that of the

current BD-100-1A10 fleet. This fleet has never had an UHT event since its entry into service back in 2003. However, full compliance with 14 CFR 25.901(c) would require introduction of complicated and novel design changes to the BD-100-1A10. It is recognized that experience over the past few years has demonstrated that so me solutions can safely and reliably eliminate the likelihood of a single failure or combination of failures leading to an UHT event that will jeopardize the safe operation of the airplane. At this time Bombardier is assessing which design solution to incorporate in the BD-100-1A10 aircraft to eliminate most, if not all, UHT failure effects to the aircraft safety.

Issue of Public Interest

A control system design change that will keep the aircraft controllable for all UHT failure modes of concern for the Bombardier BD-100-1A10 would require significant modifications to the current engine control system. Since this featur e is still in development, such redesign would prevent Bombardier from certifying the Challenger 350 design changes on a timely and competitive schedule, putting it in an unfair disadv antage to its competitors and directly affecting

its US customers. Additionally, requiring the BD-100-1A10 model to fu lly comply with this rule would adversely affect US companies involved in the design and production of the aircraft.

Effect of the Exemption on Safety

As stated above and demonstrated to the authorities by analysis, the risks due to uncontrollable high thrust failure conditions on the improv ed BD-100-1A10/AS907-2-1A will not exceed those for the current BD-100-1A10 (equipped with the AS907-1-1A engine) and for the currently known and accepted comparable existing transport category airplanes. This means that granting this exemption should not adversely affe ct safety within the current transport airplane

fleet. The conditions under which an uncontrollable high thrust failure may jeopardize the safe operation of the airplane are limited to specific conditions during takeoff and landing scenarios. This limited exposure, in conjunction with the low probability of occurrence, means that anJune 20, 2014 AW-BD1/14/435

Uncontrolled High Thrust event is a very low risk per flight hour. Also, given that one of these
scenarios occurs, there are still limited risks t hat any serious injury will develop. This assessment is supported by the fact that the 1997 Saudi Arabian Airlines Boeing 737-200 accident is the only one attributed to these types of failures and there were no serious injuries in

that accident.

Waiver of Notice and Public Procedure

Bombardier respectfully requests that action on this petition should not be delayed by publication and comment procedures. Bombardier believes that the existence of numerous previous granted similar exemptions justifies this request.

Conclusion

Bombardier believes that the above arguments favor a time limited exemption from 14 CFR 25.901(c) for the aft fuselage mounted installation of the Honeywell FADEC controlled engines onto the Challenger 350 aircraft. Additionally, Bombardier believes that any risks due to an Uncontrollable High Thrust failure condition on the Challenger 350 will not exceed those currently known and accepted for the current aircraft configuration and for those of comparable existing transport category airplanes and that an exemption is in the public interest. Bombardier requests that the privileges of this exemption would apply outside the United States due to the transoceanic capability of the BD-100-1A10 aircraft and the character of mission for many of our
operators.

John Kotnjek Manager, Airworthiness