2011-14113. Special Conditions: Pratt and Whitney Canada Model PW210S Turboshaft Engine

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions.

SUMMARY:

These special conditions are issued for Pratt and Whitney Canada (PWC) model PW210S engines. The engine model will have a novel or unusual design feature which is engine operation in auxiliary power unit (APU) mode. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These special conditions contain the added safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.

DATES:

The effective date of these special conditions is July 11, 2011.

FOR FURTHER INFORMATION CONTACT:

For technical questions concerning this rule contact Marc Bouthillier, ANE-111, Engine and Propeller Directorate, Aircraft Certification Service, 12 New England Executive Park, Burlington, Massachusetts 01803-5299; telephone [phone]; facsimile [phone]; e-mail [e-mail]. For legal questions concerning this rule contact Vincent Bennett, ANE-7 Engine and Propeller Directorate, Aircraft Certification Service, 12 New England Executive Park, Burlington, Massachusetts 01803-5299; telephone [phone]; facsimile [phone]; e-mail [e-mail].

SUPPLEMENTARY INFORMATION:

Background

On December 5, 2005, PWC applied for type certification for a new model PW210S turboshaft engine. This engine consists of a two stage compressor driven by a single stage uncooled turbine, and a two stage free power turbine driving a two stage reduction gearbox. The control system includes a dual channel full authority digital electronic control.

The engine will incorporate a novel or unusual design feature, which is engine operation in auxiliary power unit (APU) mode.

The applicable airworthiness standards do not contain adequate or appropriate airworthiness standards to address this design feature.

These special conditions contain the additional airworthiness standards necessary to establish a level of safety equivalent to the level that would result from compliance with the applicable standards of airworthiness in effect on the date of application.

Type Certification Basis

Under the provisions of 14 CFR 21.17(a) and 21.101(a), PWC must show that the model PW210S turboshaft engine meets the provisions of the applicable regulations in effect on the date of application, unless otherwise specified by the FAA. The application date is December 5, 2005, which corresponds to 14 CFR part 33 Amendment 20. However, PWC has elected to demonstrate compliance to later amendments of part 33 for this model. Therefore, the certification basis for the PW210S model turboshaft engine will be part 33, effective February 1, 1965, amended by Amendments 33-1 through 33-24.

The FAA has determined that the applicable airworthiness regulations in part 33, Amendments 1-24 inclusive, do not contain adequate or appropriate safety standards for the model PW210 turboshaft engine, because of a novel or unusual rating. Therefore, special conditions are prescribed under the provisions of 14 CFR 11.19 and 14 CFR 21.16.

The FAA issues special conditions, as defined by 14 CFR 11.19, in accordance with 14 CFR 11.38, which become part of the type certification basis in accordance with § 21.17(b)(2).

Special conditions are initially applicable to the model for which they are issued. Should the type certificate for that model be amended later to include another related model that incorporates the same or similar novel or unusual design feature, or should any other model already included on the same type certificate be modified to incorporate the same or similar novel or unusual design feature, the special conditions would also apply to the other model.

Novel or Unusual Design Features

The PWC PW210S turbo shaft engine will incorporate a novel or unusual design feature which is engine operation in auxiliary power unit (APU) mode. This design feature is considered to be novel and unusual relative to the part 33 airworthiness standards.

Discussion of Comments

Notice of proposed special conditions, Notice No. 33-10-01-SC for the PW210S engine model was published on February 14, 2011 (76 FR 8321). One comment letter was received.

The commenter stated that the part 1 definition included in the special condition may not be necessary, or may require clarification. The FAA does not agree. The definition is necessary to explain the engine function to which these special conditions apply, and the term is used within the rule itself. However, to improve clarity, each of the special condition subsections now includes a reference to APU mode operation.

The commenter stated that the 400 cycle dynamic braking test is inappropriate for this engine certification program, that engine dynamics will be difficult to simulate in a test stand, and that an engine test of this type would be better addressed as part of part 29 rotorcraft certification testing. The FAA does not agree. This test is the same as conducted for turbopropeller engines under § 33.96 and is applicable to turboshaft engines as well. We do not believe it is impractical to reasonably simulate the braking action input into the engine type design, and that the effects of dynamic braking need to be demonstrated on the complete engine prior to issuing a type certificate. Lastly, a need for installation limitations or special instructions for continued airworthiness requirements could be identified based on the results from this test, making it impractical to wait for part 29 certification testing.

The commenter stated that the locked rotor portion of the special condition tests needs to be conducted on a single engine, but the dynamic requirements can be addressed separately. The FAA concurs in part. We have concluded that an engine test is required to demonstrate the complete engine response to dynamic braking, however we do agree that the two elements of required testing (locked rotor and dynamic) can be conducted on separate test engines. The FAA has therefore revised paragraph (d) to eliminate the reference to paragraph (b) (400 cycle dynamic braking test), and therefore allows separate engine tests at the applicant's discretion. The FAA has also deleted proposed paragraph (0, which is a safety analysis requirement specific to dynamic responses. In this regard, existing § 33.75 Safety Analysis is considered adequate when an engine test for dynamic braking is conducted per this special condition.

Applicability

These special conditions are applicable to the PWC PW210S turbo shaft engine. If PWC applies later for a change to the type certificate to include another closely related model incorporating the same novel or unusual design feature, these special conditions may also apply to that model as well, and would be made part of the certification basis for that model.

Conclusion

We reviewed the available data, including the comment received, and have determined that air safety and the public interest require adopting this special condition with the changes described above. This action affects only certain novel or unusual design features on one model of engine. It is not a rule of general applicability, and it affects only the applicant who applied to the FAA for approval of this feature on the engine product.

List of Subjects in 14 CFR Part 33

• Air transportation
• Aircraft
• Aviation safety
• Safety

The authority citation for these special conditions is as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.

The Special Conditions

Accordingly, the Federal Aviation Administration (FAA) issues the following special conditions as part of the type certification basis for the PWC PW210S turbo shaft engine.

1. PART 1 DEFINITION. Unless otherwise approved by the Administrator and documented in the appropriate manuals and certification documents, the following definition applies to this special condition: “Auxiliary Power Unit Mode”—Engine operation with the main output shaft and power turbine locked and stationary, while the gas generator portion of the engine continues to operate, for the purpose of supplying the rotorcraft with electric/hydraulic/pneumatic power (as applicable) while on the ground.

2. PART 33 ENGINE TEST REQUIREMENTS:

(a) Ground locking: A total of 45 hours with the engine output shaft locked to simulate rotor brake engagement, in a manner which clearly demonstrates the complete engine's ability to function without adverse affect while operating in the APU mode under the maximum conditions of engine rotor speed, torque, temperature, air bleed and power extraction as specified by the applicant.

(b) Dynamic braking: A total of 400 application-release cycles of simulated brake engagements must be made in a manner which clearly demonstrates the complete engine's ability to function without adverse affect while operating in the APU mode under the maximum conditions of engine acceleration and deceleration rate, rotor speed, torque and temperature as specified by the applicant. The engine output shaft must be stopped prior to brake-release.

(c) One hundred engine starts and stops with the output shaft locked in a manner simulating rotor brake engagement during APU mode operation.

(d) The tests required by paragraphs (a) and (c) of this section must be performed on the same engine.

(e) The tests required by paragraphs (a), (b) and (c) above must be followed by engine disassembly to the extent necessary to show that each engine part conforms to the type design and is eligible for incorporation into an engine for continued operation in accordance with information submitted in compliance with § 33.4 Instructions for Continued Airworthiness.

Issued in Burlington, Massachusetts, on May 25, 2011.

Colleen M. D'Alessandro,

Acting Assistant Manager, Engine and Propeller Directorate, Aircraft Certification Service.