Document ID: FAA-2017-0537-0003
Agency: faa
Document Type: Rule
Title: Special Conditions: General Electric Company, GE9X Engine Models; Endurance Test Special Conditions
Posted Date: 2017-11-16T05:00Z

[Federal Register Volume 82, Number 220 (Thursday, November 16, 2017)]
[Rules and Regulations]
[Pages 53400-53403]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-24812]

=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. FAA-2017-0537; Notice No. 33-17-02-SC]

Special Conditions: General Electric Company, GE9X Engine Models; 
Endurance Test Special Conditions

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued for the General Electric 
Company turbofan engine models GE9X-105B1A, -105B1A1, -105B1A2, -
105B1A3, -102B1A, -102B1A1, -102B1A2, -102B1A3, and -93B1A. In these 
special conditions, the engine models will be referred to as ``GE9X.'' 
The engines will have novel or unusual design features associated with 
the engine design. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for these design 
features. These special conditions contain the additional safety 
standards that the Administrator considers necessary to establish a 
level of safety equivalent to that established by the existing 
airworthiness standards.

DATES: Effective December 18, 2017.

FOR FURTHER INFORMATION CONTACT: Diane Cook, AIR-6A1, Engine and 
Propeller Standards Branch, Aircraft Certification Service, 1200 
District Avenue, Burlington, Massachusetts 01803-5213; telephone (781) 
238-7111; facsimile (781) 238-7199; email [email protected].

SUPPLEMENTARY INFORMATION:

Background

    On January 29, 2016, General Electric Company (GE) applied for a 
type certificate for their new GE9X turbofan engine models. The GE9X 
engine models are high-bypass-ratio engines that incorporate novel or 
unusual design features. The GE9X engine models incorporate new 
technologies such that the company cannot run the endurance test 
conditions prescribed in Sec.  33.87 without significant modifications 
making the test vehicle non-representative of the type design.

Discussion

    An alternative endurance test cycle has been developed that 
provides a level of safety equivalent with that intended by Sec.  
33.87. The alternate endurance test provides the test conditions that 
allow the engine to be run in type design configuration and demonstrate 
engine operability and durability as well as systems functionality to a 
level intended by the current Sec.  33.87 rule.
    These special conditions provide the necessary conditions for 
verification of engine-level and component-level effects as intended by 
the current Sec.  33.87 Endurance test. The test is run in engine type 
design configuration, with only limited test enabling modifications as 
needed. The special conditions include a demonstration for the oil, 
fuel, air bleed, and accessory drive systems as required in the current 
Sec.  33.87 Endurance test.
    The equivalent level of severity intended by the Sec.  33.87 
Endurance test is provided by an engine test demonstration at the gas 
path limiting temperature and at shaft speed redlines and at the most 
extreme shaft speeds as determined through a critical point analysis 
(CPA). In addition, times on condition and cycle counts were developed 
to allow additional challenges to the novel or unusual

[[Page 53401]]

design features that would not have been as challenged by the current 
Sec.  33.87 test schedule.
    The level of durability is equivalent with that intended by the 
rule, which considers the damage accumulated during the test for the 
limiting damage mechanisms for components and engine systems, up to and 
including the applicable limitations declared in the Type Certificate 
Data Sheets (TCDS). The alternate test schedule provides conditions in 
the engine for a sufficient amount of time to demonstrate that no 
potential safety issue will develop from the limiting damage mechanisms 
while operating in service.
    The special conditions for Sec. Sec.  33.4 and 33.29 are added to 
support an equivalent compliance by means of mandatory inspections 
prescribed in paragraph (b)(3) of the Sec.  33.87 special conditions. 
These special condition requirements maintain a level of safety 
equivalent to the level intended by the applicable airworthiness 
standards in effect on the date of application.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17, GE must show that the GE9X engine models meet the 
applicable provisions of part 33, as amended by Amendments 33-1 through 
33-34. The FAA has determined that the applicable airworthiness 
regulations in part 33 do not contain adequate or appropriate safety 
standards for the GE9X engine models because of their novel or unusual 
engine design features. Therefore, these special conditions are 
prescribed under the provisions of 14 CFR 11.19 and 21.16, and will 
become part of the type certification basis for GE9X engine models in 
accordance with Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The GE9X engine models will incorporate the following novel or 
unusual design features: Technological advances that reduce noise and 
emissions while improving fuel efficiency and increasing thrust, when 
compared to previous similarly certificated GE engine models. The 
technological advances are incorporated into hardware design, 
materials, and engine operating characteristics. Introduction of 
complex cooling systems and film-cooled components cause metal 
temperatures to be significantly influenced by cooling air temperatures 
and air flows and are no longer in direct proportion to the gas path 
temperature which is a target of the current endurance test. 
Introduction of new materials, new design features, and operating 
conditions also introduced new failure modes that are not targeted by 
the current endurance test cycle. Some of the technological 
advancements were introduced in prior GE engine models and mitigated by 
modifications to the test engine.
    For past certifications, GE has shown that the engine design, as 
modified, still represented the durability and operating 
characteristics of the intended type design but the modifications 
needed to the GE9X engine model to run the Sec.  33.87 Endurance test 
cannot be reconciled and would affect the test outcome.

Discussion of Comments

    Notice of proposed special conditions No. 33-17-02-SC for the GE9X 
engine models was published in the Federal Register on 82 FR 28790. We 
received one comment from an anonymous commenter that acknowledged the 
need for special conditions as it concerns the GE9X engines models. We 
understand and acknowledge the comment we received, which is supportive 
of a special condition for the GE9X engine model. No further response 
is required.

Applicability

    As discussed above, the special conditions are applicable to the 
GE9X engine model(s). Should GE apply at a later date for a change to 
the type certificate to include another model on the same type 
certificate incorporating the same novel or unusual design feature, the 
special conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on the GE9X turbofan engine models. It is not a rule of general 
applicability and applies only to GE, who requested FAA approval of 
this engine feature.

List of Subjects in 14 CFR Part 33

    Aircraft, Engines, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

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

The Special Conditions

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for the GE9X engine models: GE9X-105B1A, -
105B1A1, -105B1A2, -105B1A3, -102B1A, -102B1A1, 102B1A2, -102B1A3, and 
-93B1A.

PART 33--REQUIREMENTS

Sec.  33.4  Instructions for Continued Airworthiness

    The Airworthiness Limitations section must prescribe the mandatory 
post-flight inspections and maintenance actions associated with any 
exceedance required by the endurance test, paragraph (b)(3), of these 
special conditions.

Sec.  33.29  Instrument Connection

    The engine must have means, or provisions for means, to 
automatically record and alert maintenance personnel of each occurrence 
of any exceedance required by the endurance test paragraph (b)(3), of 
these special conditions.

Sec.  33.87  Endurance Test

    (a) General: The applicant must show that the endurance test 
schedule in combination with any prescribed mandatory actions provide 
an equivalent level of severity and demonstration of durability and 
operability as that intended by Sec.  33.87(a) and (b). When showing 
that the level of durability is equivalent with that intended by the 
rule, the applicant must consider the damage accumulated during the 
test for the limiting damage mechanisms for components and engine 
systems, up to and including the applicable limitations declared in the 
type certificate data sheets (TCDS). The test cycle content must create 
conditions in the engine for a sufficient amount of time to demonstrate 
no potential safety issue will develop from the limiting damage 
mechanisms while operating in service. The following minimum 
requirements apply:
    (1) Conduct the tests in paragraphs (b), (c), and (d) of these 
special conditions, for total cumulative and dwell time duration 
between ground idle and the takeoff thrust prescribed in these special 
conditions. The test cycle durations must include all maximums allowed 
in the TCDS and expected service operation.
    (2) Requirements of Sec.  33.87(a)(1), (2), (4), and (6).
    (3) Requirements of Sec.  33.87(a)(3) applicable to the temperature 
of external surfaces of the engine.
    (4) Testing for maximum air bleed must be at least equal with the 
prescribed test required in Sec.  33.87(a)(5). However, for these 
cycles, the thrust or the rotor shaft rotational speed may be less than 
100 percent of the value associated with the particular operation being 
tested if the FAA finds that the validity of the endurance test is not 
compromised.

[[Page 53402]]

    (5) Testing for engine fuel, oil, and hydraulic fluid pressure and 
oil temperature must be at least equal with the prescribed test 
required in Sec.  33.87(a)(7).
    (6) If the number of occurrences of either transient rotor shaft 
overspeed or transient gas over temperature is not limited, at least 
155 accelerations must be made at the limiting overspeed or over 
temperature. If the number of occurrences is limited, that number of 
accelerations must be made at the limiting overspeed or over 
temperature.
    (7) One hundred starts must be made, of which:
    (i) Twenty-five starts must be preceded by at least a two-hour 
engine shutdown.
    (ii) Ten false engine starts must be accomplished, pausing for the 
applicant's specified minimum fuel drainage time, before attempting a 
normal start.
    (iii) Ten normal restarts must be accomplished with not longer than 
15 minutes since engine shutdown.
    The remaining starts may be made after completing the endurance 
testing prescribed by these special conditions.
    (8) Unless otherwise specified (i.e. (d)(2) of these special 
conditions), for accelerations from ground idle to takeoff, the 
throttle must be moved in not more than one second, except that, if 
different regimes of control operations are incorporated necessitating 
scheduling of the thrust-control lever motion in going from one extreme 
position to the other, a longer period of time is acceptable, but not 
more than two seconds.
    (i) When operating with max oil temperatures the throttle movement 
may be `stair-stepped' to allow for oil temperature stabilization for 
durations greater than two seconds.
    (9) The applicant must validate any analytical methods used for 
compliance with these special conditions. Validation includes the 
ability to accurately predict an outcome applicable to the engine being 
tested.
    (10) The applicant must perform the endurance test on an engine 
that substantially conforms to its type design. Modifications may be 
made as needed to achieve test conditions and/or engine operating 
conditions representative of the type design.
    (b) Conduct the endurance test at or above the declared shaft 
speeds and gas temperatures limits, and at or above conditions 
representative of critical points (speeds, temperatures, rated thrust) 
in the operating envelope.
    (1) Conduct the endurance test at or above the rated takeoff thrust 
and rated maximum continuous thrust and with the associated limits for 
rotor speeds and gas temperature (redlines), as follows:
    (i) Either rotor speed or gas temperature, or concurrent rotor 
speed and gas temperature, if analysis indicates a combination of 
redline operational conditions is possible to occur in service, must be 
at least 100 percent of the values associated with the engine rating 
being tested.
    (ii) The cumulative test time duration and number of cycles must be 
representative of the rotor speed and gas temperature excursions to 
redlines that can be expected to occur in between overhauls.
    (iii) The time durations for each takeoff or maximum continuous 
segment must include all maximums allowed in the TCDS and expected 
service operation and must include the following cycles:
    (A) At least one (1) takeoff cycle of 5-minutes time duration at 
the low pressure rotor speed limit and gas temperature limit 
(redlines).
    (B) At least one (1) takeoff cycle of 5-minutes time duration at 
the high pressure rotor speed limit and gas temperature limit 
(redlines).
    (C) In lieu of the separate cycles specified in paragraphs (A) and 
(B) of this section, the applicant may run the low pressure and high 
pressure rotor speeds and gas temperature limits (redlines) in the same 
cycle. However, in this case, the applicant must run at least 2 cycles 
of 5 minutes' time duration each.
    (2) Conduct the endurance test at or above the rated takeoff thrust 
and the rated maximum continuous thrust with rotor speeds at or above 
those determined by a critical point analysis (CPA) and with gas 
temperature redline conditions as follows:
    (i) The applicant must determine through a CPA the highest rotor 
shaft rotational speeds (CPA speeds) expected to occur for each rotor 
shaft system within the declared operating envelope. The CPA must be 
conducted for the takeoff and maximum continuous rated thrust and must 
consider the declared operating envelope, engine deterioration, engine-
to-engine variability, and any other applicable variables that can 
cause the engine to operate at the extremes of its performance ratings.
    (ii) Except as provided in paragraph (b)(3)(ii) of these special 
conditions, conduct a cyclic test between ground idle and combined 
takeoff and maximum continuous thrust ratings, as follows:
    (A) Eighteen hours and forty-five minutes (18.75 hours) cumulated 
time duration at or above the rated takeoff thrust, the gas temperature 
limit for takeoff (redline), and the CPA rotor speeds for takeoff 
determined per paragraph (b)(2)(i) of these special conditions.
    (B) Forty-five (45) hours cumulated time duration at or above the 
rated maximum continuous thrust, the gas temperature limit for maximum 
continuous (redline), and the CPA rotor speeds for maximum continuous 
determined per paragraph (b)(2)(i) of these special conditions.
    (C) The time durations for each takeoff or maximum continuous 
segments must include all maximums allowed in the TCDS and expected 
service operation, and must include at least one maximum continuous 
cycle of 30 minutes run continuously.
    (3) If the cyclic shaft speed excursions specified in paragraphs 
(b)(1) or (b)(2) of these special conditions cannot be demonstrated in 
the test, then an alternative equivalent with the rule intent must be 
provided. Alternatives may include alternate means of test 
demonstration, mandatory actions, or other means found acceptable to 
the FAA. The applicant must prescribe a mandatory action plan for 
engine operation between the shaft speeds demonstrated for a minimum of 
cumulated 18.75 hours at or above rated takeoff and 45 hours at or 
above rated maximum continuous, respectively, and the declared speed 
limits (redlines), as follows:
    (i) Prescribe post-event actions or operating limitations 
acceptable to the FAA for operation below the declared speed limits 
(redlines) and above the CPA speeds.
    (ii) If the test required by (b)(2)(ii) of these special conditions 
can only be accomplished at a rotor shaft speed lower than the CPA 
speed, prescribe post-event actions or operating limitations acceptable 
to the FAA for operation below that CPA speed and above the value 
demonstrated during the test.
    (c) Conduct the endurance test at the incremental cruise thrust 
that must be at least equal with the prescribed test required in Sec.  
33.87(b)(4). The 25 incremental test cycles must be uniformly 
distributed throughout the entire endurance test.
    (d) Conduct at least 300 cycles between ground idle and combined 
rated takeoff and rated maximum continuous thrust, as follows:
    (1) Each cycle to include acceleration to or above rated takeoff 
thrust, deceleration from takeoff to ground idle, followed by 5 to 15 
seconds at ground idle, acceleration to or above rated

[[Page 53403]]

maximum continuous thrust, and deceleration to ground idle.
    (2) The throttle movement from ground idle to rated takeoff or 
maximum continuous thrust and from rated takeoff thrust to ground idle 
should be not more than one (1) second, except that, if different 
regimes of control operations are incorporated necessitating scheduling 
of the thrust-control lever motion in going from one extreme position 
to the other, a longer period of time is acceptable, but not more than 
two (2) seconds. The throttle movement from rated maximum continuous 
thrust to ground idle should not be more than five (5) seconds.
    (3) The time durations for each cycle associated with either 
takeoff or maximum continuous thrust segments must include all maximums 
allowed in the TCDS and expected service operation, and must include 
the following cycles:
    (i) Three (3) cycles of 5 minutes each and one (1) cycle of 10 
minutes at the takeoff thrust.
    (ii) Three (3) cycles of 30 minutes each at the maximum continuous 
thrust.

    Issued in Burlington, Massachusetts, on November 8, 2017.
Robert J. Ganley,
Manager, Engine and Propeller Standards Branch, Aircraft Certification 
Service.
[FR Doc. 2017-24812 Filed 11-15-17; 8:45 am]
 BILLING CODE 4910-13-P