Document ID: FAA-2012-0745-0004
Agency: faa
Document Type: Rule
Title: Special Conditions: GE Aviation CT7-2E1 Turboshaft Engine Model
Posted Date: 2013-03-12T04:00Z

[Federal Register Volume 78, Number 48 (Tuesday, March 12, 2013)]
[Rules and Regulations]
[Pages 15597-15599]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-05676]

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  Federal Register / Vol. 78, No. 48 / Tuesday, March 12, 2013 / Rules 
and Regulations  

[[Page 15597]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. FAA-2012-0745; Special Condition No. 33-012-SC]

Special Conditions: GE Aviation CT7-2E1 Turboshaft Engine Model

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These final special conditions are issued for the General 
Electric Aviation (GE) CT7-2E1 engine model. This engine model will 
have a novel or unusual design feature, which is a combination of two 
existing ratings into a new rating called ``flat 30-second and 2-minute 
OEI'' rating. This rating is intended for the continuation of flight of 
a multi-engine rotorcraft after one engine becomes inoperative. The 
applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for this design feature. These final 
special conditions contain the additional safety standards 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 April 11, 
2013.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this rule, contact Dorina Mihail, ANE-111, Engine and Propeller 
Directorate, Aircraft Certification Service, 12 New England Executive 
Park, Burlington, Massachusetts 01803-5299; telephone (781) 238-7153; 
facsimile (781) 238-7199; email dorina.mihail@faa.gov. 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 
(781) 238-7044; facsimile (781) 238-7055; email 
vincent.bennett@faa.gov.

SUPPLEMENTARY INFORMATION: 

Background

    On September 10, 2009, GE applied for an amendment to type 
certificate E8NE to add the new CT7-2E1 turboshaft engine model. The 
CT7-2E1 engine model is a derivative of the CT7 engine family certified 
between 1977 and 2010. It is a free turbine turboshaft designed for a 
transport category twin-engine helicopter. The CT7-2E1 engine model 
will incorporate a novel and unusual feature, which is the ``flat 30-
second and 2-minute OEI'' rating. The applicant requested this rating 
to provide the increased power required for the rotorcraft performance. 
A special condition is necessary to apply additional requirements for 
the rating's definition, overspeed, controls system, and endurance 
test, because the applicable airworthiness standards do not contain 
adequate or appropriate airworthiness standards to address this design 
feature.
    The ``flat 30-second and 2-minute OEI'' rating is equivalent in 
some regards with the 2\1/2\-minute OEI rating, and in other regards 
with the 30-second OEI and the 2-minute OEI ratings. However, the new 
rating differs from the 2\1/2\-minute OEI rating because it limits the 
number of occurrences per flight and mandates post-flight inspection 
and maintenance actions. The new rating is similar with the combined or 
joined 30-second OEI and 2-minute OEI ratings when they are equal. 
However, the existing standards are not adequate for this combination.
    Similar to the ``flat 30-second and 2-minute OEI'' rating, the 30-
second and 2-minute OEI ratings were introduced to provide multi-engine 
rotorcraft with high power for short periods of time when an engine 
becomes inoperative during critical flight conditions. Existing 
airworthiness standards for the 30-second OEI and 2-minute OEI ratings 
were established based on the assumption the two ratings will be 
selected together as a package, and that the 30-second OEI rating is 
higher than the 2-minute OEI rating. Because the 30-second OEI rating 
was assumed higher, specific requirements were established for only 
this rating and for the 30 second time period. When the 30-second and 
2-minute OEI ratings are equal, these requirements must be extended to 
a total period of 2.5 minutes.
    These final special conditions for the ``flat 30-second and 2-
minute OEI'' rating are based on a combination of existing regulations 
for the 2\1/2\-minute OEI rating, and the 30-second and 2-minute OEI 
ratings. Under the provisions of Sec.  21.101(d), the special 
conditions must provide a level of safety equal to that established by 
the regulations in effect on the date of the application for the 
change.
    We determined that the type certification basis for the GE CT7-2E1 
engine model is up to and including Amendment 20 of part 33; refer to 
the section below titled ``Type Certification Basis.'' We also 
determined that the part 33 standards, up to and including Amendment 
25, contain part of the standards for the ``flat 30-second and 2-minute 
OEI.'' Therefore, we do not prescribe special conditions when the 
requirements exist in later amendments, instead we will apply these 
later amendments. These later requirements are:
    (1) Section A33.4, Airworthiness Limitations Section, paragraphs 
(b)(1) and (b)(2) of Amendments 1-25, and
    (2) Section 33.5, Instruction manual for installing and operating 
the engine, paragraph (b)(4) of Amendments 1-25.
    These final special conditions are in addition to the requirements 
of the 30-second and 2-minute OEI ratings that remain applicable to the 
``flat 30-second and 2-minute OEI'' rating, as follows:
    (1) These final special conditions extend the standards applicable 
to the 30-second or 2-minute OEI ratings for the 2.5 minute time 
duration of the ``flat 30-second and 2-minute OEI'' rating. We 
developed these special conditions by revising the time dependent 
requirements of Sec. Sec.  33.27, 33.87(a)(7), and 33.88(c). The 2.5 
minute time duration for the rating would affect the structural and 
operational characteristics of the engine that are time dependent, such 
as the values for transients, time duration for stabilization to steady 
state, and part growth due to deformation. In addition, these special 
conditions are applied by extending the 30-second OEI rating 
requirements of Sec.  33.67(d) for automatic availability and control 
of the engine power, from 30 seconds to 2.5 minutes.

[[Page 15598]]

    (2) These final special conditions are required to account for the 
proposed rating of a 2.5 minute time duration during the endurance 
test. For the 30-second and 2-minute OEI ratings, the test schedule of 
Sec.  33.87(f) is divided among the two ratings. We applied these 
special conditions by revising the requirements of Sec.  33.87(f) to 
ensure the test will run for a 2.5 minute duration with no 
interruption.

Type Certification Basis

    Under the provisions of 14 CFR 21.101(a), GE must show the CT7-2E1 
turboshaft engine model meets the provisions of the applicable 
regulations in effect on the date of application, except as detailed in 
Sec.  21.101(b) and (c). We have determined the following certification 
basis for the CT7-2E1 turboshaft engine model.
    (1) 14 CFR part 33, ``Airworthiness Standards: Aircraft Engines,'' 
dated February 1, 1965, with Amendments 1 through 20, except Sec. Sec.  
33.5(b)(4), A33.4(b)(1), and A33.4(b)(2), Amendments 1-25 applicable to 
the ``flat 30-second and 2-minute OEI'' rating. The applicant will 
voluntarily comply with Sec.  33.28, Amendments 1-28 for the EECU, FMU, 
and AISBV.
    (2) 14 CFR part 34, Amendments 1 through 4, Sec.  34.11 ``Standard 
for Fuel Venting Emissions.''
    Under the provisions of 14 CFR 21.101(d), if we find the 
regulations in effect, on the date of the application for the change, 
do not provide adequate standards with respect to the proposed change 
because of a novel or unusual design feature, the applicant must also 
comply with special conditions, and amendments to those special 
conditions prescribed under the provisions of Sec.  21.16 to provide a 
level of safety equal to that established by the regulations in effect 
on the date of the application for the change.
    We issue special conditions, as defined by 14 CFR 11.19, under 14 
CFR 11.38, which become part of the type certification basis as 
specified in Sec. Sec.  21.17(a)(2) or 21.101(d).
    Special conditions are initially applicable to the engine model for 
which they are issued. If the type certificate for that model is 
amended later, to include another related model that incorporates the 
same or similar novel or unusual design feature, or if any other model 
already included on the same type certificate is modified to 
incorporate the same or similar novel or unusual design feature, these 
special conditions may also apply to the other model.

Novel or Unusual Design Features

    The CT7-2E1 turboshaft engine model will incorporate a ``flat 30-
second and 2-minute OEI'' rating for use after the failure or shutdown 
of one engine and for up to three periods of 2.5 minutes each on any 
one flight. These final special conditions, discussed below, for the 
``flat 30-second and 2-minute OEI'' rating will address this novel and 
unusual design feature.

Discussion of Comments

    A notice of proposed special conditions, No. 33-12-01-SC, for the 
CT7-2E1 turboshaft engine model was published on July 20, 2012 (77 FR 
42677). We received six comments from European Aviation Safety Agency 
(EASA) and two from Honeywell. One comment from EASA resulted in 
changes to the special conditions; the remaining comments resulted in 
clarifications.
    The EASA commented that the special conditions for the overspeed 
test of Sec.  33.27 should not be the same as the requirements 
applicable to the 2\1/2\-minute OEI rating. EASA considers that 
applying the overspeed test requirements associated with the 30-second 
and 2-minute OEI ratings would be more appropriate.
    We partially agree. We agree the requirements for the 30-second and 
2-minute OEI ratings are more appropriate, except for the test time 
duration requirement. For the CT7 engine model, the overspeed 
requirements for the 30-second and 2-minute OEI ratings reside in the 
special conditions 33-002-SC, published on May 28, 1999 (64 FR 28900). 
We are therefore adopting these requirements, except that the time 
duration of paragraph (a) of 33-002-SC is increased from 2.5 minutes to 
5 minutes in these final special conditions. The rationale is that the 
test time duration should be representative of the rating duration, 
which is 2.5 minutes at the flat 30-second and 2-minute OEI rating 
versus 30 seconds at the 30-second OEI. Also, the 5 minutes test time 
is the same as that applied to the 2\1/2\-minute OEI rating, which is a 
rating of the same time duration.
    The EASA commented that amendments to Sec. Sec.  33.67(d) and 
33.28(k) are discussed, despite not being addressed under the part 33 
requirements section of the proposed special conditions. The EASA found 
this section unclear and suggested that additional clarification be 
provided.
    We agree. We eliminated the references to Sec.  33.28(k) and 
assigned the special conditions to Sec.  33.67(d), instead of Sec.  
33.28(k). This resulted in no change to the proposed special conditions 
themselves because Sec.  33.28(k), Amendment 26 and Sec.  33.67(d) 
Amendment 18, contain the same requirements.
    Honeywell and EASA provided comments related to the ``Note'' in the 
proposed special conditions paragraph (e)(1). The note addressed the 
intent for temperature stabilization. Honeywell recommended revising 
the note for clarity. The EASA stated that the note is confusing.
    We agree. We determined the note is not necessary and removed the 
note in the final special conditions.
    The EASA commented that for the overtemperature tests of Sec.  
33.88, the existing requirements are for a 4 minute demonstration at 35 
degrees F, hotter than the maximum temperature limit for the 30 second 
OEI rating. The proposed special conditions, however, amend this 
requirement by increasing this demonstration to 5 minutes duration. The 
EASA does not see the technical grounds for this increase in severity.
    We do not agree. The 4 minute test duration applies to ratings of 2 
minutes and shorter. The 5 minute test duration applies to ratings 
longer than 2 minutes. Since the flat 30-second and 2-minute OEI is a 
rating of 2.5 minutes length, the test time requirements should be a 5 
minute duration; the same as that for the 2\1/2\-minute OEI.
    The EASA commented on the applicability of Appendix A to part 33, 
A33.4 (b)(1) to the flat 30-second and 2-minute OEI rating. 
Specifically, that the flat 30-second and 2-minute OEI rating is a 
single rating, while the requirement of A33.4 (b)(1) applies to either 
30-second OEI or 2-minute OEI ratings. EASA stated that the existing 
requirements are written for the existing ratings and not for the `new' 
rating introduced by these special conditions, therefore, is not clear 
whether these requirements are relevant to the `new' rating.
    We do not agree. The airworthiness standards of Appendix A to part 
33, A33.4(b)(1) for the 30-second OEI and 2-minute OEI ratings were 
established based on the assumption that the two ratings will be 
selected together as a package. Paragraph A33.4(b)(1) does not 
prescribe specific requirements for the 30-second OEI versus 2-minute 
OEI ratings and provides requirements for the use of both ratings. 
Therefore, A33.4(b)(1) requirements for maintenance actions associated 
with the use of the 30-second and 2-minute OEI ratings apply to the new 
rating.
    Honeywell provided a comment related to the naming of the rating,

[[Page 15599]]

which, although recognizable, appears cumbersome. Honeywell suggested 
that, ``Rated limited use 2\1/2\-minute OEI'' could be a better 
definition that would still distinguish it from the existing unlimited 
use of the 30-second, 2-minute, and 2\1/2\-minute OEI ratings.
    We do not agree. The applicant requested the new rating be named in 
closer relation with the 30-second and 2-minute OEI ratings for 
consistency across existing engine models and to align the new rating 
with the 30-second and 2-minute-OEI ratings at the rotorcraft level. We 
agree with the applicant's proposed name. We also do not agree with the 
commenter that the 30-second and 2-minute OEI ratings are ``unlimited 
use.'' These ratings are limited to a maximum use of 3 times per flight 
and require post-flight inspection, per 14 CFR 1.1, Definitions.

Applicability

    These special conditions are applicable to the GE CT7-2E1 
turboshaft engine model. If GE 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 would 
apply to that model, as well. This is true, provided the certification 
basis is the same or contains later amendments that satisfy the 
certification basis discussed in the section titled, ``Type 
Certification Basis.''

Conclusion

    We reviewed the available data and determined that air safety and 
the public interest require adopting these special conditions. This 
action affects certain novel or unusual design features on the CT7-2E1 
turboshaft engine model. It is not a rule of general applicability and 
applies only to GE, whom requested FAA approval for this engine 
feature.

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 FAA issues the following special conditions as 
part of the type certification basis for the GE CT7-2E1 turboshaft 
engine model.

1. Part 1 Definitions

    Unless otherwise approved by the Administrator and documented in 
the appropriate manuals and certification documents, the following 
definition applies: ``Rated Flat 30-second and 2-minute One Engine 
Inoperative (OEI) Power,'' with respect to rotorcraft turbine engines, 
means: (1) A rating for which the shaft horsepower and associated 
operating limitations of the 30-second OEI and 2-minute OEI ratings are 
equal, and (2) the shaft horsepower is that developed under static 
conditions at the altitude and temperature for the hot day, and within 
the operating limitations established under part 33. The rating is for 
continuation of one flight operation after the failure or shutdown of 
one engine in multiengine rotorcraft. The rating is for up to three 
periods of use no longer than 2.5 minutes each in any one flight, and 
followed by mandatory inspection and prescribed maintenance action.

2. Part 33 Requirements

    (a) In addition to the airworthiness standards in the type 
certification basis applicable to the engine and the 30-second and 2-
minute OEI ratings, the special conditions in this section apply.
    (b) Section 33.7 Engine ratings and operating limitations. Flat 30-
second and 2-minute OEI rating and operating limitations are 
established by power, torque, rotational speed, gas temperature, and 
time duration.
    (c) Section 33.27 Turbine, compressor, fan, and turbosupercharger 
rotor overspeed. In addition to the requirements of Sec.  33.27(b):
    (1) The turbine and compressor rotors must have sufficient strength 
to withstand the test conditions specified in paragraph (2) below.
    (2) The applicant must determine, by analysis or other acceptable 
means, the most critically stressed rotor component of each turbine and 
compressor, including integral drum rotors and centrifugal compressors. 
These components must be tested for the conditions in paragraphs (i) or 
(ii) below. The test selection from the following paragraphs (i) or 
(ii) below is determined by the speed defined in paragraph (i)(B) or 
(ii)(B), whichever is higher.
    (i) Test for a period of 5 minutes:
    (A) At its maximum operating temperature, except as provided in 
Sec.  33.27(c)(2)(iv); and
    (B) At the highest speed determined, in accordance with Sec.  
33.27(c)(2)(i) through (iv).
    (C) This test may be performed using a separate test vehicle as 
desired.
    (ii) Test for a period of 5 minutes:
    (A) At its maximum operating temperature, except as provided in 
paragraph (ii)(C) below; and
    (B) At 100 percent of the highest speed that would result from 
failure of the most critical component of each turbine and compressor, 
or system, in a representative installation of the engine when 
operating at the flat 30-second and 2-minute OEI rating conditions; and
    (C) The test speed must take into account minimum material 
properties, maximum operating temperature, if not tested at that 
temperature, and the most adverse dimensional tolerances.
    (D) This test may be performed using a separate test vehicle as 
desired. Following the test, rotor growth and distress beyond 
dimensional limits for an overspeed condition are permitted provided 
the structural integrity of the rotor is maintained, as shown by a 
procedure acceptable to the FAA.
    (d) Section 33.67(d) Fuel system. Engines must incorporate a means, 
or a provision for a means, for automatic availability and automatic 
control of the flat 30-second and 2-minute OEI power for the duration 
of 2.5 minutes and within the declared operating limitations.
    (e) Section 33.87 Endurance test. The requirements applicable to 
30-second and 2-minute OEI ratings, except for:
    (1) The test of Sec.  33.87(a)(7) as applicable to the 2\1/2\-
minute OEI rating.
    (2) The tests in Sec.  33.87(f)(2) and (3) must be run continuously 
for the duration of 2.5 minutes, and
    (3) The tests in Sec.  33.87(f)(6) and (7) must be run continuously 
for the duration of 2.5 minutes.
    (f) Section 33.88 Engine overtemperature test. The requirements of 
Sec.  33.88(c), except that the test time is 5 minutes instead of 4 
minutes.

    Issued in Burlington, Massachusetts on March 4, 2013.
Robert J. Ganley,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2013-05676 Filed 3-11-13; 8:45 am]
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