
[Federal Register Volume 78, Number 122 (Tuesday, June 25, 2013)]
[Rules and Regulations]
[Pages 37958-37962]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-13841]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. FAA-2013-0493; Special Conditions No. 23-260-SC]


Special Conditions: Cessna Aircraft Company, Model J182T; 
Electronic Engine Control System Installation

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Cessna Aircraft 
Company (Cessna) Model J182T airplane. This airplane will have a novel 
or unusual design feature(s) associated with the installation of an 
electronic engine control. 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: The effective date of these special conditions is June 25, 2013.
    We must receive your comments by July 25, 2013.

ADDRESSES: Send comments identified by docket number [FAA-2013-0493] 
using any of the following methods:
    [ssquf] Federal eRegulations Portal: Go to http://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
    [ssquf] Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
    [ssquf] Hand Delivery of Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE., Washington, DC, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    [ssquf] Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: The FAA will post all comments it receives, without 
change, to http://www.regulations.gov, including any personal 
information the commenter provides. Using the search function of the 
docket Web site, anyone can find and read the electronic form of all 
comments received into any FAA docket, including the name of the 
individual sending the comment (or signing the comment for an 
association, business, labor union, etc.). DOT's complete Privacy Act 
Statement can be found in the Federal Register published on April 11, 
2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov.
    Docket: Background documents or comments received may be read at 
http://www.regulations.gov at any time. Follow the online instructions 
for accessing the docket or go to the Docket Operations in Room W12-140 
of the West Building Ground Floor at 1200 New Jersey Avenue SE., 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Mr. Peter Rouse, Federal Aviation 
Administration, Small Airplane Directorate, Aircraft Certification 
Service, 901 Locust, Room 301, Kansas City, MO 64106; telephone (816) 
329-4135; facsimile (816) 329-4090.

SUPPLEMENTARY INFORMATION: The FAA has determined that notice and 
opportunity for prior public comment hereon are impracticable because 
these procedures would significantly delay issuance of the design 
approval and thus delivery of the affected aircraft. In addition, the 
substance of these special conditions has been subject to the public 
comment process in several prior instances with no substantive comments 
received. The FAA therefore finds that good cause exists for making 
these special conditions effective upon issuance.

Comments Invited

    We invite interested people to take part in this rulemaking by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data. We ask 
that you send us two copies of written comments.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions based on the comments we receive.

Background

    On April 2, 2012, Cessna Aircraft Company applied for an amendment 
to Type Certificate No. 3A13 to include the new model J182T which will 
incorporate the installation of the Societe de Motorisation 
Aeronautiques (SMA) Engines, Inc. SR305-230E-C1 which is a four-stroke, 
air cooled, diesel cycle engine that uses turbine (jet) fuel. The J182T 
incorporates an engine controlled by an electronic engine

[[Page 37959]]

control (EEC), also known as a Full Authority Digital Engine Control 
(FADEC). The EEC system performs critical functions throughout the 
operational envelope such as the control of the fuel flow and ignition. 
These functions and their impact on the engine are required by 14 CFR 
parts 33 and 23. Additionally, the EEC systems have incorporated 
functions, that while not required in either parts 33 or 23, have 
potential failure(s) and malfunction(s) that may be catastrophic or 
unacceptably degrade the airplane level of safety. Examples of the 
additional functions include thrust management, engine parameter 
indication, engine speed synchronization, engine torque equalization, 
etc. Considerations for installation of EEC systems were not envisaged 
and are not adequately addressed in part 23. Therefore, special 
conditions are required to define the additional safety standards the 
Administrator considers necessary to establish a level of safety 
equivalent to the existing airworthiness standards. Cessna will use an 
EEC instead of a traditional mechanical control system on the J182T 
airplane. The J182T, which is a derivative of the T182T currently 
approved under Type Certificate No. 3A13, is an aluminum, four place, 
single engine airplane with a cantilever high wing, with the SMA SR305-
230E-C1 diesel cycle engine and equipped with an electronic engine 
control.
    The EEC is part 33 certified as part of the engine, and the 
certification requirements for engine control systems are driven by 
part 33 requirements. The guidance for the part 33 EEC certification 
requirement is contained in two advisory circulars: 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 part 23 installation requirements. However, the 
guidance does highlight some of the installation aspects 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 excluded powerplant systems as part of the certificated engine 
(reference Sec.  23.1309(f)(1), amendment No. 23-49). 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 be 
incomplete 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 
because behavior acceptable for part 33 certification may not be 
acceptable for part 23 certification.
    The Small Airplane Directorate has applied a Special Condition for 
over a decade that required all EEC installations to comply with the 
requirements of Sec. Sec.  23.1309(a) through (e), amendment No. 23-49. 
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 
electronic engine control 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 23.1309-1E showing the relationship among airplane 
classes, probabilities, severity of failure conditions, and software 
and complex hardware Development Assurance Level.

--------------------------------------------------------------------------------------------------------------------------------------------------------
     Classification of failure           No safety effect             Minor                  Major                Hazardous             Catastrophic
             conditions             --------------------------------------------------------------------------------------------------------------------
------------------------------------      No probability
 Allowable qualitative probability         requirement               Probable                Remote            Extremely remote    Extremely  improbable
--------------------------------------------------------------------------------------------------------------------------------------------------------
Effect on Airplane.................  No effect on             Slight reduction in    Significant reduction  Large reduction in     Normally with hull
                                      operational              functional             in functional          functional             loss.
                                      capabilities or safety.  capabilities or        capabilities or        capabilities or
                                                               safety margins.        safety margins.        safety margins.
Effect on Occupants................  Inconvenience for        Physical discomfort    Physical distress to   Serious or fatal       Multiple fatalities.
                                      passengers.              for passengers.        passengers, possibly   injury to an
                                                                                      including injuries.    occupant.
Effect on Flight Crew..............  No effect on flight      Slight increase in     Physical discomfort    Physical distress or   Fatal Injury or
                                      crew.                    workload or use of     or a significant       excessive workload     incapacitation.
                                                               emergency procedures.  increase in workload.  impairs ability to
                                                                                                             perform tasks.
--------------------------------------------------------------------------------------------------------------------------------------------------------
        Classes of Airplanes         Allowable Quantitative Probabilities and Software (SW) and Complex Hardware (HW) Development Assurance Levels (Note
                                                                                              2)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Class I (Typically SRE 6,000 pounds  No Probability or SW     <10-\3\ Note 1 P=D...  <10-\4\ Notes 1 and 4  <10-\5\ Note 4 P=C,    <10-\6\ Note 3 P=C,
 or less).                            and HW Development                              P=C, S=D.              S=D.                   S=C.
                                      Assurance Levels
                                      Requirement.
Class II (Typically MRE, STE, or     No Probability or SW     <10-\3\ Note 1 P=D...  <10-\5\ Notes 1 and 4  <10-\6\ Note 4 P=C,    <10-\7\ Note 3 P=C,
 MTE 6,000 pounds or less).           and HW Development                              P=C, S=D.              S=C.                   S=C.
                                      Assurance Levels
                                      Requirement.

[[Page 37960]]

 
Class III (Typically SRE, STE, MRE,  No Probability or SW     <10-\3\ Note 1 P=D...  <10-\5\ Notes 1 and 4  <10-\7\ Note 4 P=C,    <10-\8\ Note 3 P=B,
 and MTE greater than 6,000 pounds).  and HW Development                              P=C, S=D.              S=C.                   S=C.
                                      Assurance Levels
                                      Requirement.
Class IV (Typically Commuter         No Probability or SW     <10-\3\ Note 1 P=D...  <10-\5\ Notes 1 and 4  <10-\7\ Note 4 P=B,    <10-\9\ Note 3 P=A,
 Category).                           and HW Development                              P=C, S=D.              S=C.                   S=B.
                                      Assurance Levels
                                      Requirement.
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Note 1: Numerical values indicate an order of probability range and are provided here as a reference.
Note 2: The letters of the alphabet denote the typical SW and HW Development Assurance Levels for Primary System (P) and Secondary System (S). For
  example, HW or SW Development Assurance Level A on Primary System is noted by P=A.
Note 3: At airplane function level, no single failure will result in a Catastrophic Failure Condition.
Note 4. Secondary System (S) may not be required to meet probability goals. If installed, S should meet stated criteria.

Difference Between Part 23 and Part 33 Guidance, Loss of Thrust or 
Power Control

    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 23.1309-1E guidance. The part 33 
requirements for engine control LOTC/LOPC probabilities are shown 
below:

--------------------------------------------------------------------------------------------------------------------------------------------------------
               Engine type                       Average LOTC/LOPC  events per million hours            Maximum LOTC/LOPC  events per million hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
Turbine Engine...........................  10 (1 x 10-05 per hour)...............................  100 (1 x 10-04 per hour).
Reciprocating Engine.....................  45 (4.5 x 10-05 per hour).............................  450 (4.5 x 10-04 per hour).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: See AC 33.28-1, AC 33.28-2 and ANE-1993-33.28TLD-Rl for further guidance.

    The part 23 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-lE failure probability values, it is obvious that a 
single engine airplane electronic engine control 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 
inappropriately declared a reduced hazard severity for a failure of the 
electronic engine control 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 artificially establish lower hazard severities. There is also a 
conflict between the classification of the failure condition of an 
electronic engine control 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.

Time Limited Dispatch

    The advent of electronic engine controls also created 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-Rl, 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 between inspection/maintenance intervals to mitigate the 
hazard. As such, the FAA has issued specific guidance for part 23 
aircraft in addition to Policy Statement, ANE-1993-33.28TLD-Rl, in 
order to capture the necessary time limits between maintenance 
intervals.

Additional Functions

    The advent of electronic engine controls also led to incorporating 
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 safety levels. 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.
    Part 25, unlike part 23, does not apply Sec.  25.1309 via special 
condition to the electronic engine control installation. Section 
25.1309 is applicable to the powerplant installations in general and as 
a whole. The part 25 hazard classifications for LOTC/LOPC differ from 
part 23 due to the required multi-engine configuration of part 25 
aircraft. Additional applicable part 25 subpart E requirements are 
those contained within Sec.  25.901(b)(2) and (c):

Sec. 25.901--Installation.

    a. Rule Text.
    (b) For each powerplant--
    (2) The components of the installation must be constructed, 
arranged, and installed so as to ensure their continued safe 
operation between normal inspections or overhauls;
    (c) For each powerplant and auxiliary power unit installation, 
it must be established that no single failure or malfunction or 
probable combination of failures will jeopardize the safe operation 
of the airplane except that the failure of structural elements need 
not be considered if the probability of such failure is extremely 
remote.


[[Page 37961]]


    The following are excerpts from guidance provided in FAA Policy 
Statement, PS-ANM100-2002-00073:

Section 25.901--Installation.

    b. Intent of Rule:
     Sec.  25.901(b)(2) is intended to require such 
preventative maintenance as is necessary to ensure that components 
of the powerplant installation do not cease safe functioning.
     Sec.  25.901(c) is intended to define, in general 
terms, the foreseeable failures that each powerplant and auxiliary 
power unit installation must be shown to safely accommodate.

(7) Sec.  25.901(c): Section 25.901(c) is intended to provide an 
overall safety assessment of the powerplant installation. It is 
intended to augment rather than replace other, more specific 
applicable Part 25 design and performance standards for transport 
category airplanes. When assessing the potential hazards to the 
aircraft caused by the powerplant installation, the effects of an 
engine case rupture, uncontained engine rotor failure, engine case 
burnthrough, and propeller debris release are excluded from Sec.  
25.901(c). The effects and rates of these failures are minimized by 
compliance with Part 33 (``Airworthiness Standards: Aircraft 
Engines''; Part 35 (``Airworthiness Standards: Propellers''; Sec.  
25.903(d)(l) (``Engines''; Sec.  25.905(d) (``Propellers''; and 
Sec.  25.1193 (``Cowling and nacelle skin''. Furthermore, the 
effects of encountering environmental threats or other operating 
conditions more severe than those for which the aircraft is 
certified (such as volcanic ash or operation above placard speeds) 
need not be considered in the Sec.  25.901(c) compliance process. 
However, if a failure or malfunction can affect the subsequent 
environmental qualification or other operational capability of the 
installation, this effect should be accounted/or in the Sec.  
25.901(c) assessment.
(a) Compliance with Sec.  25.901(c) may be shown by a System Safety 
Assessment (SSA) substantiated by appropriate testing and/or 
comparable service experience. Such an assessment may range from a 
simple report that offers descriptive details associated with a 
failure condition, interprets test results, compares two similar 
systems, or offers other qualitative information; to a detailed 
failure analysis that may include estimated numerical probabilities. 
The depth and scope of an acceptable SSA depends on:
     the complexity and criticality of the functions 
performed by the system(s) under consideration,
     the severity of related failure conditions,
     the uniqueness of the design and extent of relevant 
service experience,
     the number and complexity of the identified causal 
failure scenarios, and
     the detectability of contributing failures.

(b) Historically, the use of a ``bottom-up single failure 
analysis,'' such as a Failure Modes and Effects Analysis (FMEA), has 
been a popular safety assessment method with many applicants. 
Wherever the effects of a failure are found to be operationally 
``latent,'' then the effects of the ``next worst'' failure are 
assessed. In this approach, the ``probable combinations of 
failures'' are assumed only to be a single latent failure plus ``the 
next worst'' failure. When assessing the failure effects of a simple 
mechanical, hydro-mechanical, or electrical system, where 
independence from the effects of failures elsewhere in the aircraft 
can be assumed, this can be an effective and relatively simple means 
of assuring that the design is adequately ``fail-safe.'' However, as 
the integration and diversity of functions and technologies in the 
subject design increase, particularly when digital avionics are 
involved, the resulting increases in complexity, interdependence, 
and parts count make this ``latents-plus-one'' assumption about the 
``probable combinations of failure'' questionable. Consequently, to 
ensure that the design is ``fail-safe'' for a sufficient number of 
co-existing failures, probability methods are typically necessary.

(d) In carrying out the SSA for the powerplant installation for 
Sec.  25.90I(c), the results of the engine (and propeller) failure 
analyses (reference Sec.  33.28 and Sec.  33.75) should be used as 
inputs for those powerplant failure effects that can have an impact 
on the aircraft. However, the SSA undertaken in response to Part 33 
and Part 35 may not address all the potential effects that an engine 
and propeller as installed may have on the aircraft. For those 
failure conditions covered by analysis under Part 33 and/or Part 35, 
and for which the installation has no effect on the conclusions 
derived from these analyses, no additional analyses will be required 
to demonstrate compliance to Sec.  25.901(c).

    There is language similar to Sec.  25.901(c) contained in Sec.  
23.1141(e):

Sec.  23.1141--Powerplant controls: General.

    (e) For turbine engine powered airplanes, no single failure or 
malfunction, or probable combination thereof, in any powerplant 
control system may cause the failure of any powerplant function 
necessary for safety.

    The requirements contained within Sec.  23.114l(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.

Type Certification Basis

    Under the provisions of Sec.  21.101, Cessna must show that the 
model J182T meets the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. 3A13 or the 
applicable regulations in effect on the date of application for the 
change to the model T182T. The regulations incorporated by reference in 
the type certificate are commonly referred to as the ``original type 
certification basis.'' In addition, the J182T certification basis 
includes special conditions and equivalent levels of safety.
    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 J182T 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 J182T 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 defined in Sec.  11.19, under 
Sec.  11.38 and they become part of the type certification basis under 
Sec.  21.101.
    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.

Novel or Unusual Design Features

    The J182T will incorporate the following novel or unusual design 
features: Electronic engine control system.

Discussion

    These special conditions address the certification requirements for 
the installation of Electronic Engine Control (EEC) systems on part 23 
airplanes. As described in the background section, the advisory 
circular and policy guidance between part 33 and part 23 contains 
differences that can lead to conflicting certification requirements. As 
such, these special conditions are necessary in order to provide a 
reasonable means of compliance that removes the conflicts between part 
33 and part 23. The intent of these special conditions is to provide a 
robust and fault tolerant electronic engine control installation that 
ensures no single failure or malfunction or probable combination of 
failures will jeopardize the safe operation of the airplane.

[[Page 37962]]

Applicability

    As discussed above, these special conditions are applicable to the 
model J182T. Should Cessna 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 and 
affects only the applicant who applied to the FAA for approval of these 
features on the airplane.
    The substance of these special conditions has been subjected to the 
notice and comment period in several prior instances and has been 
derived without substantive change from those previously issued. It is 
unlikely that prior public comment would result in a significant change 
from the substance contained herein. Therefore, because a delay would 
significantly affect the certification of the airplane, which is 
imminent, the FAA has determined that prior public notice and comment 
are unnecessary and impracticable, and good cause exists for adopting 
these special conditions upon issuance. The FAA is requesting comments 
to allow interested persons to submit views that may not have been 
submitted in response to the prior opportunities for comment described 
above.

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 
21.101; 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 Cessna Model J182T airplanes.
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 must be shown to comply with the HIRF and 
lightning requirements appropriate for catastrophic failure conditions.
    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 
23.1309-1E. The term ``probable'' in ``probable combination of 
failures'' means ``foreseeable,'' or (in AC 23.1309-1E terms), ``not 
extremely improbable.''

    Issued in Kansas City, Missouri on May 29, 2013.
Earl Lawrence,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 2013-13841 Filed 6-24-13; 8:45 am]
BILLING CODE 4910-13-P


