[Federal Register Volume 76, Number 225 (Tuesday, November 22, 2011)]
[Rules and Regulations]
[Pages 72087-72091]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-28616]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 23
[Docket No. CE313; Special Conditions No. 23-253-SC]
Special Conditions: Diamond Aircraft Industries, Model DA-40NG;
Electronic Engine Control (EEC) System
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Diamond Aircraft
Industries, Model DA-40NG airplane. This airplane will have a novel or
unusual design feature(s) associated with an electronic engine control
(EEC) also known as a Full authority Digital Engine Control (FADEC).
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: October 28, 2011.
FOR FURTHER INFORMATION CONTACT: Peter L. Rouse, Federal Aviation
Administration, Aircraft Certification Service, Small Airplane
Directorate, ACE-111, 901 Locust, Kansas City, Missouri, (816) 329-
4135, fax (816) 329-4090.
SUPPLEMENTARY INFORMATION:
Background
On May 11, 2010, Diamond Aircraft Industry GmbH applied for an
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amendment to Type Certificate No. A47CE to include the new model DA-
40NG with the Austro Engine GmbH model E4 Aircraft Diesel Engine (ADE).
The model DA-40NG, which is a derivative of the model DA-40 currently
approved under Type Certificate No. A47CE, is a fully composite, four
place, single-engine airplane with a cantilever low wing, T-tail
airplane with the Austro Engine GmbH model E4 diesel engine and an
increased maximum takeoff gross weight from 1150 kilograms (kg) to 1280
kg (2535 pounds (lbs) to 2816 lbs).
DAI will use an EEC instead of a traditional mechanical control
system on the model DA-40NG airplane. The EEC is certified as part of
the engine design certification, and the certification requirements for
engine control systems are driven by 14 CFR part 33 certification
requirements. The guidance for the part 33 EEC certification
requirement is contained in two advisory circulars: Advisory Circular
(AC) 33.28-1 and AC 33.28-2. The EEC certification, as part of the
engine, addresses those aspects of the engine specifically addressed by
part 33 and is not intended to address 14 CFR part 23 installation
requirements. However, the guidance does highlight some of the aspects
of installation that the engine applicant should consider during engine
certification. The installation of an engine with an EEC system
requires evaluation of environmental effects and possible effects on or
by other airplane systems, including the part 23 installation aspects
of the EEC functions. For example, the indirect effects of lightning,
radio interference with other airplane electronic systems, and shared
engine and airplane data and power sources.
The regulatory requirements in part 23 for evaluating the
installation of complex electronic systems are contained in Sec.
23.1309. However, when Sec. 23.1309 was developed, the requirements of
the rule were specifically excluded from applying to powerplant systems
provided as part of the engine (reference Sec. 23.1309(f)(1)).
Although the parts of the system that are not certificated with the
engine could be evaluated using the criteria of Sec. 23.1309, the
analysis would not be useful and not be complete because it would not
include the effects of the aircraft supplied power and data failures on
the engine control system, and the resulting effects on engine power/
thrust. The integral nature of EEC installations require review of EEC
functionality at the airplane level, as behavior acceptable for part 33
certification may not be acceptable for part 23 certification.
For over a decade, the Small Airplane Directorate has applied a
special condition that required all EEC installations to comply with
the requirements of Sec. 23.1309(a) through (e). The rationale for
applying Sec. 23.1309 was that it was an existing rule that contained
the best available requirements to apply to the installation of a
complex electronic system; in this case, an EEC with aircraft
interfaces. Additionally, special conditions for High Intensity
Radiated Fields (HIRF) were also applied prior to the codification of
Sec. 23.1308.
There are several difficulties for propulsion systems directly
complying with the requirements of Sec. 23.1309. There are conflicts
between the guidance material for Sec. 23.1309 and propulsion system
capabilities and failure susceptibilities. The following figure is an
excerpt from AC 23.1309-1D.
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[GRAPHIC] [TIFF OMITTED] TR22NO11.003
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There is a conflict between the EEC system loss-of-thrust-control
(LOTC), or loss-of-power-control (LOPC), probability per hour
requirements given in part 33 guidance material and the failure rate
requirements associated with the hazard created by a total loss of
power/thrust as given in part 23 AC 23.1309-1D guidance. The part 33
requirements for engine control LOTC/LOPC probabilities are shown
below:
------------------------------------------------------------------------
Average LOTC/LOPC Maximum LOTC/LOPC
Engine type Events per million Events per million
hours hours
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Turbine Engine.................. 10 (1 x 10-05 per 100 (1 x 10-04 per
hour). hour).
Reciprocating Engine............ 45 (4.5 x 10-05 450 (4.5 x 10-04
per hour). per hour).
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Note: See AC 33.28-1, AC 33.28-2 and ANE-1993-33.28TLD-R1 for further
guidance.
[[Page 72090]]
The classification of the failure condition for LOTC/LOPC event on
a single engine airplane ranges from Hazardous to Catastrophic. The
classification of the failure condition for a single engine LOTC/LOPC
event on a multi-engine airplane ranges from Major to Catastrophic. The
classification of the failure condition for a multi-engine LOTC/LOPC
event on a multi-engine airplane is Catastrophic. From the AC 23.1309-
1D failure probability values, it is obvious that a single engine
airplane EEC system will not be able to meet the failure probabilities
as shown in the guidance material for Sec. 23.1309. As a result,
applicants have elected to declare a reduced hazard severity for a
failure of the EEC system. This is not the intent of Sec. 23.1309. The
greater hazard severity should be associated with lower probabilities
of failure, and higher probabilities of failure should not establish
the lower hazard severities. There is also a conflict between the
classification of the failure condition for a failure of an EEC system
and the required test levels for the effects of lightning and high
intensity radiated frequency (HIRF). Testing to a level lower than
required for a catastrophic failure results in a lower level of safety
than the mechanical system it replaces. This is contrary to the intent
of certification requirements.
The advent of EEC also created/established the ability to dispatch
with certain allowable loss of functionality and/or redundancy. This is
known as Time-Limited Dispatch (TLD). The TLD allowable configurations
must meet the specific risk LOTC/LOPC failure probabilities. FAA policy
statement, ANE-1993-33.28TLD-R1, defines the full up and TLD allowable
failure probabilities for turbine engines. The ability to use TLD is a
risk management endeavor that uses a limited time period between
inspection/maintenance intervals to mitigate the hazard. As such, the
FAA has issued specific guidance for part 23 airplanes in addition to
policy statement, ANE-1993-33.28TLD-R1, in order to adequately capture
the necessary time limits between maintenance intervals. A means of
compliance issue paper giving specific guidance can be generated, if
desired, for the applicant.
The advent of EEC also led to incorporation of functions that,
while not required by the CFRs, also introduce potentially catastrophic
failure(s) and malfunction(s). Consequently, incorporation of these
additional functions must be shown to retain part 23 levels of safety.
These additional functions have included thrust management, portions of
engine indication otherwise provided as part of the engine
installation, engine speed synchronization, ignition control, auto-
feather, etc.
The certification of an airplane to the standards of 14 CFR part 25
does not require the application of Sec. 25.1309 via special condition
to the EEC installation. In part 25, Sec. 25.1309 is applicable to the
powerplant installations in general and as a whole. The part 25
consequences differ from part 23 due to the required multi-engine
configuration of part 25 airplanes. Additional applicable part 25,
Subpart E requirements are those contained within Sec. 25.901(b)(2)
and (c).
There is language similar to part 25, Sec. 25.901(c) contained in
part 23, Sec. 23.1141(e).The requirements contained within Sec.
23.1141(e) were originally intended for the mechanical control
interfaces on turbine engines. The rule was first promulgated at
Amendment 23-7, effective on September 14, 1969. The preamble
justifying the rule change states:
``This proposal would, in effect require that the need for
system redundancy, alternate devices, and duplication of functions
be determined in the design of turbine powerplant control systems.''
The overall intent of the above cited rules is to provide a robust
and fault tolerant engine control installation that ensures that no
single failure or malfunction or probable combination of failures will
jeopardize the safe operation of the airplane.
Given the unique requirements of an EEC installation, and the lack
of specific regulatory requirements, a special condition will be
applied to all EEC installations in part 23 airplanes. This special
condition is not applicable to the part 33 engine certification
requirements, and it specifically excludes any part 33 references.
Compliance with this special condition may necessitate changes to the
EEC, and may require additional part 33 compliance showings. In like
manner, changes to the EEC at the part 33 level may require additional
compliance showings to this special condition. The overall intent of
this special condition is to leverage off of the part 33 compliance as
much as possible and address the airplane level effects of an EEC
installation.
The EEC system includes all of the subsystems on the aircraft that
interface with the EEC and provide aircraft data and electrical power.
This special condition is applicable to and includes all functions of
the EEC system that have an effect at the airplane level. An example of
this is control of the turbine engine compressor variable geometry
(VG): the VG function in itself is not an airplane function, but
changes to the VG scheduling will require re-substantiating compliance
to part 23 requirements, such as Sec. 23.939.
The components that should be considered part of the EEC system are
defined in Society of Automotive Engineers (SAE) document, Aerospace
Recommended Practice (ARP) 5107B, Guidelines for Time-Limited-Dispatch
(TLD) Analysis for Electronic Engine Control Systems, section 6.4. This
guidance is intended for turbine engine installations; however, the
intent is applicable to piston engine installations. A means of
compliance issue paper giving specific guidance can be generated, if
desired, for the applicant.
Part 33 certification data, if applicable, may be used to show
compliance with the requirements of part 23 installation requirements;
however, compliance with the part 33 requirements does not constitute
compliance with the requirements of part 23, nor automatically imply
that the engine is installable on a part 23 airplane. The part 23
applicant is required to show compliance in accordance with part 21. If
part 33 data is to be used, then the part 23 applicant must be able to
provide this data for their showing of compliance to the part 23
requirements.
Type Certification Basis
Under the provisions of Sec. 21.101, DAI must show that the model
DA-40NG meets the applicable provisions of the regulations incorporated
by reference in Type Certificate No. A47CE or the applicable
regulations in effect on the date of application for the change to the
model DA-40. The regulations incorporated by reference in the type
certificate are commonly referred to as the ``original type
certification basis.''
If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 23) do not contain adequate or
appropriate safety standards for the model DA-40NG because of a novel
or unusual design feature, special conditions are prescribed under the
provisions of Sec. 21.16.
In addition to the applicable airworthiness regulations and special
conditions, the model DA-40NG 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.
The FAA issues special conditions, as appropriate, as defined in
Sec. 11.19, under Sec. 11.38, and they become part of the type
certification basis under Sec. 21.101(b)(2).
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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, or should any other model already included on
the same type certificate be modified to incorporate the same novel or
unusual design feature, the special conditions would also apply to the
other model under the provisions of Sec. 21.101(a)(1).
Novel or Unusual Design Features
The model DA-40NG will incorporate the following novel or unusual
design features: Electronic engine control system.
Discussion
As discussed above, these special conditions are applicable to the
model DA-40NG. Should DAI 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.
Discussion of Comments
Notice of proposed special conditions No. 23-10-03-SC for the
Diamond Aircraft Industries, model DA-40NG, airplane was published on
September 7, 2011 (76FR 55293). No comments were received, and the
special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions are applicable to the
model DA-40NG. Should DAI 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.
Under standard practice, the effective date of final special
conditions would be 30 days after the date of publication in the
Federal Register; however, as the certification date for the Diamond
Aircraft Industries (DAI), model DA-40NG airplane is imminent, the FAA
finds that good cause exists to make these special conditions effective
upon issuance.
Conclusion
This action affects only certain novel or unusual design features
on one model of airplane. It is not a rule of general applicability,
and it affects only the applicant who applied to the FAA for approval
of these features on the airplane.
List of Subjects in 14 CFR Part 23
Aircraft, Aviation safety, Signs and symbols.
Citation
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR 21.16 and
21.17; and 14 CFR 11.38 and 11.19.
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 Diamond Aircraft Industry GmbH
model DA-40NG with the installation of the Austro Engine GmbH model E4
aircraft diesel engine.
1. Electronic Engine Control
a. For electronic engine control system installations, it must be
established that no single failure or malfunction or probable
combinations of failures of Electronic Engine Control (EEC) system
components will have an effect on the system, as installed in the
airplane, that causes the loss-of-thrust-control (LOTC), or loss-of-
power-control (LOPC) probability of the system to exceed those allowed
in part 33 certification.
b. Electronic engine control system installations must be evaluated
for environmental and atmospheric conditions, including lightning. The
EEC system lightning and High-Intensity Radiated Fields (HIRF) effects
that result in LOTC/LOPC should be considered catastrophic.
c. The components of the installation must be constructed,
arranged, and installed so as to ensure their continued safe operation
between normal inspections or overhauls.
d. Functions incorporated into any electronic engine control that
make it part of any equipment, systems or installation whose functions
are beyond that of basic engine control, and which may also introduce
system failures and malfunctions, are not exempt from Sec. 23.1309 and
must be shown to meet part 23 levels of safety as derived from Sec.
23.1309. Part 33 certification data, if applicable, may be used to show
compliance with any part 23 requirements. If part 33 data is to be used
to substantiate compliance with part 23 requirements, then the part 23
applicant must be able to provide this data for their showing of
compliance.
Note: The term ``probable'' in the context of ``probable
combination of failures'' does not have the same meaning as in AC
23.1309-1D. The term ``probable'' in ``probable combination of
failures'' means ``foreseeable,'' or (in AC 23.1309-1D terms), ``not
extremely improbable.''
Issued in Kansas City, Missouri on October 28, 2011.
John Colomy,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2011-28616 Filed 11-21-11; 8:45 am]
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