
[Federal Register Volume 78, Number 133 (Thursday, July 11, 2013)]
[Rules and Regulations]
[Pages 41684-41685]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-16596]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2012-0260; Special Conditions No. 25-494-SC]


Special Conditions: Embraer S.A. Model EMB-550 Airplanes, Sudden 
Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Embraer Model EMB-
550 airplane. This airplane has novel or unusual design features as 
compared to the state of technology envisioned in the airworthiness 
standards for transport-category airplanes. These design features 
include engine size and the potential torque loads imposed by sudden 
engine stoppage. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature. 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 Date: August 12, 2013.

FOR FURTHER INFORMATION CONTACT: Cindy Ashforth, FAA, International 
Branch, ANM-116, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone 
(425) 227-2768; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION:

Background

    On May 14, 2009, Embraer applied for a type certificate for their 
new Model EMB-550 airplane. The Model EMB-550 airplane is the first of 
a new family of jets designed as a corporate jet, and for fractional, 
charter, and private-owner operations. The airplane is a conventional 
configuration with a low wing and T-tail empennage. The primary 
structure is metal with composite empennage and control surfaces. The 
Model EMB-550 airplane is designed for eight passengers, with a maximum 
of 12 passengers (including toilet seat). It is equipped with two 
Honeywell HTF7500-E medium-bypass-ratio turbofan jet engines mounted on 
aft-fuselage pylons. Each engine produces approximately 6,540 lb of 
thrust for normal takeoff. The primary flight-control systems are 
electronically controlled using fly-by-wire (FBW) technology.
    The Model EMB-550 airplane incorporates novel or unusual design 
features involving engine size and torque load that affect the airframe 
as it relates to sudden engine-stoppage conditions.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17, Embraer must show that the Model EMB-550 airplane meets the 
applicable provisions of part 25, as amended by Amendments 25-1 through 
1-127.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Model EMB-550 airplane because of 
a novel or unusual design feature, special conditions are prescribed 
under the provisions of Sec.  21.16.
    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 any other model that incorporates the same novel or 
unusual design feature, the special conditions would also apply to the 
other model.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model EMB-550 airplane must comply with the fuel-vent 
and exhaust-emission requirements of 14 CFR part 34 and the noise-
certification requirements of 14 CFR part 36; and the FAA must issue a 
finding of regulatory adequacy under Sec.  611 of Public Law 92-574, 
the ``Noise Control Act of 1972.''
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type-
certification basis under Sec.  21.17(a)(2).

Novel or Unusual Design Features

    The Model EMB-550 airplane incorporates a novel or unusual design:
    The Embraer Model EMB-550 airplane will incorporate a medium-
bypass-ratio turbofan jet engine that will neither seize nor produce 
transient torque loads in the same manner that is envisioned by current 
Sec.  25.361(b)(1) regarding ``load that affect sudden engine 
stoppage'' conditions.

Discussion of Comments

    Notice of Proposed Special Conditions No. 25-12-05-SC, for the 
Embraer Model EMB-550 airplane, was published in the Federal Register 
on September 25, 2012 (77 FR 58970). No comments were received, and the 
special conditions are adopted as proposed.

Discussion

    The size, configuration, and failure modes of jet engines have 
changed considerably from those envisioned by 14 CFR 25.361(b), when 
the engine-seizure requirement was first adopted. Engines have become 
larger and are now designed with large bypass fans capable of producing 
much larger and more complex dynamic loads. Relative to the engine 
configurations that existed when the rule was developed in 1957, the 
present generation of engines is sufficiently different and novel to 
justify issuance of a special condition to establish appropriate design 
standards for the Embraer Model EMB-550 airplane type design.
    Consideration of the limit engine torque load imposed by sudden 
engine stoppage due to malfunction or structural failure (such as 
compressor jamming) has been a specific requirement for transport-
category airplanes since 1957. In the past, the design torque loads 
associated with typical failure scenarios have been estimated by the 
engine manufacturer and were provided to the airframe manufacturer as 
limit loads. These limit loads were considered simple and pure torque 
static loads.
    It is evident from service history that the engine-failure events 
that tend to cause the most severe loads are fan-blade failures, which 
occur much less frequently than the typical ``limit'' load condition.
    The regulatory authorities and industry have developed a 
standardized requirement in the Aviation Rulemaking Advisory Committee 
(ARAC) forum. The technical aspects of this requirement have been 
agreed upon and have been accepted by the ARAC Loads and Dynamics 
Harmonization Working Group, and incorporated in EASA CS-25. The 
proposed special conditions outlined below reflect the ARAC 
recommendation and CS-25. In addition, the ARAC recommendation includes 
corresponding advisory material that is considered an acceptable means 
of compliance to the proposed special conditions outlined below.
    To maintain the level of safety envisioned in Sec.  25.361(b), more

[[Page 41685]]

comprehensive criteria are needed for the new generation of high-bypass 
engines. The special conditions would distinguish between the more 
common engine-failure events and those rare events resulting from 
structural failures. The more-common events would continue to be 
treated as static torque limit load conditions. The more-severe events 
resulting from extreme engine-failure conditions (such as loss of a 
full fan blade at redline speed), would be treated as full dynamic-load 
conditions. These would be considered ultimate loads, and include all 
transient loads associated with the event. An additional safety factor 
would be applied to the more-critical airframe supporting structure.

Applicability

    As discussed above, these special conditions are applicable to the 
Model EMB-550 airplane. Should Embraer apply at a later date for a 
change to the type certificate to include another model 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 one model of airplane. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, 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

    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 Embraer Model EMB-550 airplane.
    In lieu of 14 CFR 25.361(b), the following special conditions 
apply:
    1. For turbine-engine installations, the engine mounts, pylons, and 
adjacent supporting airframe structure must be designed to withstand 1g 
level flight loads acting simultaneously with the maximum limit torque 
loads imposed by each of the following:
    (a) Sudden engine deceleration due to a malfunction, which could 
result in a temporary loss of power or thrust, and
    (b) The maximum acceleration of the engine.
    2. For auxiliary power unit (APU) installations, the APU mounts and 
adjacent supporting airframe structure must be designed to withstand 1g 
level flight loads acting simultaneously with the maximum limit torque 
loads imposed by each of the following:
    (a) Sudden APU deceleration due to malfunction or structural 
failure; and
    (b) The maximum acceleration of the APU.
    3. For engine-supporting structure, an ultimate loading condition 
must be considered that combines 1g flight loads with the transient 
dynamic loads resulting from:
    (a) The loss of any fan, compressor, or turbine blade; and 
separately
    (b) Where applicable to a specific engine design, any other engine 
structural failure that results in higher loads.
    4. The ultimate loads developed from the conditions specified in 
paragraphs 3(a) and 3(b) of these special conditions are to be 
multiplied by a factor of 1.0 when applied to engine mounts and pylons, 
and multiplied by a factor of 1.25 when applied to adjacent supporting 
airframe structure.
    5. Any permanent deformation that results from the conditions 
specified in paragraph 3 of these special conditions must not prevent 
continued safe flight and landing.

    Issued in Renton, Washington, on June 21, 2013.
Jeffrey E. Duven,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2013-16596 Filed 7-10-13; 8:45 am]
BILLING CODE 4910-13-P


