2011-17298. 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 a 30- minute all engine operating (AEO) power rating. This rating is generally intended to be used for hovering at increased power for search and rescue missions. 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 August 10, 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, ANF-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 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 a 30-minute AEO power rating. This rating was requested by the applicant to support rotorcraft search and rescue missions that require extensive operations at high power.

The applicable airworthiness standards do not contain adequate or appropriate airworthiness standards to address this design feature. Therefore a special condition is necessary to apply additional requirements for rating definition, instructions for continued airworthiness (ICA) and endurance testing. The 30-minute time limit applies to each instance the rating is used; however there is no limit to the number of times the rating can be used during any one flight, and there is no cumulative time limitation. The ICA requirement is intended to address the unknown nature of actual rating usage and associated engine deterioration. The applicant is expected to make an assessment of the expected usage and publish ICA's and airworthiness limitations section (ALS) limits in accordance with those assumptions, such that engine deterioration is not excessive. The endurance test requirement of 25 hours operation at 30-minute AEO rating is similar to several special conditions issued over the past 20 years addressing the same subject. Because the PWC model PW210S turboshaft engine has a continuous OEI rating and limits equal to or higher then the 30-minute AEO rating, the test time performed at the continuous OEI rating may be credited toward the 25-hour requirement. However, test time spent at other rating elements of the test, such as takeoff or other OEI ratings (that may be equal to or higher values), may not be counted toward the 25 hours of required running.

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 (14 CFR 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 turboshaft engine will incorporate a novel or unusual design feature which is a 30-minute AEO power rating, for use up to 30-minutes at any time between the takeoff and landing phases of a flight. 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. 33-10-02-SC for the PW210S engine model was published on March 1, 2011 (76 FR 11172). One comment letter was received. The commenter stated disagreement with the special condition requirement of incorporating 25 hours of operation at the 30-minutes AEO rating into the § 33.87 test profile. The commenter proposing taking credit for the 30-minute periods run at takeoff rating that is part of the normal test profile required by § 33.87(b), thereby reducing the amount of test time at the new 30-minute AEO rating. The FAA does not concur. The takeoff rating and other normal use ratings are defined within 14 CFR part 1 and the associated requirements can be found in 14 CFR part 33 Takeoff rating is limited in use to a continuous period of not more then 5 minutes during takeoff operations, which occurs each flight. The existing § 33.87 requirements are designed to demonstrate engine durability for the takeoff rating which is considered a normal every flight operation, and is independent of any other ratings The proposed 30-minute rating is not defined within 14 CFR, but has been specifically requested by PWC. This new rating can be used for periods of up to 30-minutes at any time during a flight for a variety of normal mission purposes. Also, the number of usages during a single flight is not limited; and its use does not require special maintenance actions. So this rating is intended for normal mission use, similar to takeoff and other normal use ratings, and is different than limited turboshaft one-engine-inoperative (OEI) ratings. The OEI ratings for turboshafts, with the exception of continuous OEI, are for limited use during a flight and in some cases limited cumulative use. Therefore engine durability using the 30-minute AEO rating must be demonstrated over and above the takeoff rating and other normal use ratings included in the rating structure. So the baseline for endurance testing will be § 33.87(b) (no OEI rating). The FAA also finds that the test time associated with the continuous OEI rating is an appropriate baseline to define additional requirements for this new normal use 30- minute AEO rating. Therefore, engine durability using this rating must be demonstrated over and above the takeoff rating and other normal use ratings included in the rating structure. No changes to the special conditions have been made in this regard.

The commenter also states that the 25 hour requirement is inconsistent with § 33.87 philosophies, stating that time at any rating validates any lower rating. This statement is incorrect. The test requirements are established to demonstrate engine durability at all normal and emergency ratings and associated limits. The test profiles incorporate specific elements to this end. The normal ratings all have individual elements that must be performed. The 30-minutes AEO rating is a normal use rating that is expected to be used with a frequency of occurrence similar to the takeoff or maximum continuous ratings, and must have a specific and independent element as part of the overall test. Also, the expectation is that 30-minute AEO will be used far more frequently than any emergency 0E1 rating. These emergency ratings must also be demonstrated (when applicable) however due to their limited use, these elements of the test may overlap certain normal rating elements found in the various test profiles. The practice mentioned by the commenter is applied to OEI ratings only, because they are rarely used and only in emergency situations. Therefore, the frequency of occurrence for normal use ratings dictate that specific test time be allocated to each rating, and that time can't be combined because a rating is higher than another. No changes to the special conditions have been made in this regard.

The commenter also states that the basis for 25 hours of required run time was not described in the special condition. The 25 hours was selected to be between the basic cumulative run time for takeoff rating (18.75 hours) and maximum continuous rating (45 hours). This requirement is weighted more heavily toward the takeoff time due to the severe nature of the rating and intended operation. Therefore, no changes to the special conditions have been made in this regard.

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 Proposed 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: “Rated 30 Minute AEO Power”, means the approved shaft horsepower developed under static conditions at the specified altitude and temperature, and within the operating limitations established under part 33, and limited in use to periods not exceeding 30- minutes each.

2. PART 33 REQUIREMENTS.

(a) Sections 33.1 Applicability and 33.3 General: As applicable, all documentation, testing and analysis required to comply with the part 33 certification basis, must account for the 30-minute AEO rating, limits and usage.

(b) Section 33.4, instructions for continued airworthiness (ICA). In addition to the requirements of § 33.4, the ICA must:

(1) Include instructions to ensure that in-service engine deterioration due to rated 30-minute AEO power usage will not be excessive, meaning that all other approved ratings are available within associated limits and assumed usage, for successive flights; and that deterioration will not exceed that assumed for declaring a time between overhaul (TBO) period.

(i) The applicant must validate the adequacy of the maintenance actions required under paragraph (b)(1) above.

(2) Include in the airworthiness limitations section (ALS), any mandatory inspections and serviceability limits related to the use of the 30-minute AEO rating.

(c) Section 33.87, Endurance Test. In addition to the requirements of §§ 33.87(a) and 33.87(d), the overall test run must include a minimum of 25 hours of operation at 30-minute AEO power and limits, divided into periods of 30-minutes AEO power with alternate periods at maximum continuous power or less.

(1) Modification of the § 33.87 test requirements to include the 25 hours of operation at 30- minute AEO power rating must be proposed by the Applicant and accepted by the FAA.

(2) Each § 33.87(d) continuous one-engine-inoperative (0EI) rating test period of 30-minutes or longer, run at power and limits equal to or higher then the 30-minutes AEO raring, may be credited toward this requirement. Note that the test time required for the takeoff or other OEI ratings may not be counted toward the 25 hours of operation required at the 30-minute AEO rating.

Issued in Burlington, Massachusetts, on June 29, 2011.

Robert J. Ganley,

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