[Federal Register Volume 71, Number 114 (Wednesday, June 14, 2006)]
[Proposed Rules]
[Pages 34288-34292]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-9242]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE248; Notice No. 23-06-03-SC]


Special Conditions: Thielert Aircraft Engines GmbH, Piper PA 28-
161 Cadet, Warrior II and Warrior III Series Airplanes; Diesel Cycle 
Engine Using Turbine (Jet) Fuel

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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

SUMMARY: This notice proposes special conditions for the Piper PA 28-
161 Cadet, Warrior II and Warrior III series airplanes. These 
airplanes, as modified by Thielert Aircraft Engines GmbH, will have a 
novel or unusual design feature(s) associated with the installation of 
a diesel cycle engine utilizing turbine (jet) fuel. The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for installation of this new technology engine. These 
proposed 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: Comments must be received on or before July 14, 2006.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Regional Counsel, ACE-7, Attention: 
Rules Docket, Docket No. CE248, 901 Locust, Room 506, Kansas City, 
Missouri 64106, or delivered in duplicate to the Regional Counsel at 
the above address. Comments must be marked: CE248. Comments may be 
inspected in the Rules Docket weekdays, except Federal holidays, 
between 7:30 a.m. and 4 p.m.

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:

Comments Invited

    Interested persons are invited to participate in the making of 
these proposed special conditions by submitting such written data, 
views, or arguments, as they may desire. Communications should identify 
the regulatory docket or notice number and be submitted in duplicate to 
the address specified above. All communications received on or before 
the closing date for comments will be considered by the Administrator. 
The proposals described in this notice may be changed in light of the 
comments received. All comments received will be available in the Rules 
Docket for examination by interested persons, both before and after the 
closing date for comments. A report summarizing each substantive public 
contact with FAA personnel concerning this rulemaking will be filed in 
the docket. Persons wishing the FAA to acknowledge receipt of their 
comments submitted in response to this notice must include with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to CE248.'' The postcard will be date 
stamped and returned to the commenter.

Background

    On February 11, 2002, Thielert Aircraft Engines GmbH, of 
Lichtenstein, Germany applied for a supplemental type certificate to 
install a diesel cycle engine utilizing turbine (jet) fuel in Piper PA 
28-161 Cadet, Warrior II and Warrior III series airplanes. The Piper PA 
28-161 Cadet, Warrior II and Warrior III series airplanes, currently 
approved under Type Certificate No. 2A13, is a four-place, low wing, 
fixed tricycle landing gear, conventional planform airplane. The Piper 
PA 28-161 Cadet, Warrior II and Warrior III series airplanes to be 
modified have gross weights in the range of 2325 to 2440 pounds in the 
normal category. The affected series of airplanes have been equipped 
with various gasoline reciprocating engines of 160 horsepower.
    Expecting industry to reintroduce diesel engine technology into the 
small airplane fleet, the FAA issued Policy Statement PS-ACE100-2002-
004 on May 15, 2004, which identified areas of technological concern 
involving introduction of new technology diesel engines into small 
airplanes. For a more detailed summary of the FAA's development of 
diesel engine requirements, refer to this policy.
    The general areas of concern involved the power characteristics of 
the diesel engines, the use of turbine fuel in an airplane class that 
has typically been powered by gasoline fueled engines, the vibration 
characteristics and failure modes of diesel engines. These concerns 
were identified after review of the historical record of diesel engine 
use in aircraft and a review of the 14 CFR part 23 regulations, which 
identified specific regulatory areas that needed to be evaluated for 
applicability to diesel engine installations. These concerns are not 
considered universally applicable to all types of possible diesel 
engines and diesel engine installations. However, after review of the 
Thielert installation, the Thielert engine type, and the requirements 
applied by the Lufthart Bundesamt, and applying the provisions of the 
diesel policy, the FAA proposed these fuel system and engine related 
special conditions. Other special conditions issued in a separate 
notice included special conditions for HIRF and application of Sec.  
23.1309 provisions to the Full Authority Digital Engine Control 
(FADEC).

Type Certification Basis

    Under the provisions of Sec.  21.101, Thielert Aircraft Engines 
GmbH must show that the Piper PA 28-161 Cadet, Warrior II and Warrior 
III series

[[Page 34289]]

airplanes, as changed, continues to meet the applicable provisions of 
the regulations incorporated by reference in Type Certificate No. 2A13 
or the applicable regulations in effect on the date of application for 
the change. The regulations incorporated by reference in the type 
certificate are commonly referred to as the ``original type 
certification basis.'' The regulations incorporated by reference in 
Type Certificate No. 2A13 are as follows:
    The certification basis of models Piper PA 28-161 Cadet, Warrior II 
and Warrior III series airplanes is:
    Civil Air Regulations (CAR) 3 effective May 15, 1956, including 
Amendments 3-1 and 3-2; paragraph 3.387(d) of Amendment 3-4; paragraphs 
3.304 and 3.705 of Amendment 3-7, effective May 3, 1962; FAR 23.955 and 
23.959 as amended by Amendment 23-7, effective September 14, 1969; FAR 
23.1557(c)(1) as amended by Amendment 23-18, effective May 2, 1977; FAR 
23.1327 and 23.1547 as amended by Amendment 23-20, effective September 
1, 1977; and FAR 36, effective December 1, 1969, through Amendment 36-
4.
    Equivalent Safety Items for:

Airspeed Indicator--CAR 3.757

    14 CFR part 23, at Amendment level 23-51, applicable to the areas 
of change:
    14 CFR part 23, Sec. Sec.  23.1; 23.3; 23.21; 23.23; 23.25; 23.29; 
23.33; 23.45; 23.49; 23.51; 23.53; 23.63; 23.65; 23.69; 23.71; 23.73; 
23.77; 23.141; 23.143; 23.145; 23.151; 23.153; 23.155; 23.171; 23.173; 
23.175; 23.177; 23.201; 23.221; 23.231; 23.251; 23.301; 23.303; 23.305; 
23.307; 23.321; 23.335; 23.337; 23.341; 23.343; 23.361; 23.361(b)(1); 
23.361(c)(3); 23.363; 23.371; 23.572; 23.573; 23.574; 23.601; 23.603; 
23.605; 23.607; 23.609; 23.611; 23.613; 23.619; 23.621; 23.623; 23.625; 
23.627; CAR 3.159; 23.773; 23.777; 23.777(d); 23.779; 23.779(b); 
23.781; 23.831; 23.863; 23.865; 23.867; 23.901; 23.901(d)(1); 23.903; 
23.905; 23.907; 23.909; 23.925; 23.929; 23.939; 23.943; 23.951; 
23.951(c); 23.954; 23.955; 23.959; 23.961; 23.963; 23.965; 23.967; 
23.969; 23.971; 23.973; 23.973(f); 23.975; 23.977; 23.977(a)(2) in 
place of 23.977(a)(1); 23.991; 23.993; 23.994; 23.995; 23.997; 23.999; 
23.1011; 23.1013; 23.1015; 23.1017; 23.1019; 23.1021; 23.1023; 23.1041; 
23.1043; 23.1047; 23.1061; 23.1063; 23.1091; 23.1093; 23.1103; 23.1107; 
23.1121; 23.1123; 23.1141; 23.1143; 23.1145; 23.1163; 23.1165; 23.1181; 
23.1182; 23.1183; 23.1191; 23.1193; 23.1301; 23.1305; 23.1305(c)(8); 
23.1309; 23.1311; 23.1321; 23.1322; 23.1327; 23.1331; 23.1337; 23.1351; 
23.1353; 23.1357; 23.1359; 23.1361; 23.1365; 23.1367; 23.1381; 23.1431; 
23.1461; 23.1501; 23.1519; 23.1521; 23.1521(d); 23.1527; 23.1529; 
23.1541; 23.1543; 23.1549; 23.1551; 23.1555; 23.1557; 
23.1557(c)(1)(ii), in place of Sec. Sec.  23.1557(c)(i); 23.1567; 
23.1581; 23.1583; 23.1585; 23.1587 and 23.1589.
    Equivalent levels of safety for:

Cockpit controls--23.777(d)
Motion and effect of cockpit controls--23.779(b)
Liquid Cooling--Installation--23.1061
Ignition switches--23.1145

    The type certification basis includes exemptions, if any; 
equivalent level of safety findings, if any; and the special conditions 
adopted by this rulemaking action.
    In addition, if the regulations incorporated by reference do not 
provide adequate standards with respect to the change, the applicant 
must comply with certain regulations in effect on the date of 
application for the change. The type certification basis for the 
modified airplanes is as stated previously with the following 
modifications.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 23) do not contain adequate or appropriate 
safety standards for the Piper PA 28-161 Cadet, Warrior II and Warrior 
III series airplanes 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 Piper PA 28-161 Cadet, Warrior II and Warrior III 
series airplanes must comply with the 14 CFR part 21, Sec.  21.115 
noise certification requirements of 14 CFR part 36.
    Special conditions, as appropriate, as defined in Sec.  11.19, are 
issued in accordance with Sec.  11.38, and become part of the type 
certification basis in accordance with Sec.  21.101.
    Special conditions are initially applicable to the model for which 
they are issued. Should the applicant apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate 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.

Novel or Unusual Design Features

    The Piper PA 28-161 Cadet, Warrior II and Warrior III series 
airplanes will incorporate the following novel or unusual design 
features:
    The Piper PA 28-161 Cadet, Warrior II and Warrior III series 
airplanes, as modified by Thielert Aircraft Engines GmbH, will 
incorporate an aircraft diesel engine utilizing turbine (jet) fuel.

Applicability

    As discussed above, these special conditions are applicable to the 
Piper PA 28-161 Cadet, Warrior II and Warrior III series airplanes. 
Should Thielert Aircraft Engines GmbH apply at a later date for a 
supplemental type certificate to modify any other model included on 
Type Certificate No. 2A13 to incorporate the same novel or unusual 
design feature, the special conditions would apply to that model as 
well under the provisions of Sec.  21.101.

Conclusion

    This action affects only certain novel or unusual design features 
on one model series 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 
21.101; and 14 CFR 11.38 and 11.19.

Discussion

    The major concerns identified in developing FAA policy deal with 
installing the diesel engine and its vibration levels under normal 
operating conditions and with one cylinder inoperative, accommodating 
turbine fuels in airplane systems that have generally evolved based on 
gasoline requirements, the anticipated use of a FADEC to control the 
engine, and the appropriate limitations and indications for a diesel 
engine powered airplane. The general concerns associated with the 
Thielert modification are as follows:
     Installation and Vibration Requirements.
     Fuel and Fuel System Related Requirements.
     FADEC and Electrical System Requirements.
     Limitations and Indications.
    Installation and Vibration Requirements: These special conditions 
include requirements similar to the requirements of Sec.  23.901(d)(1) 
for turbine engines. In addition to the requirements of Sec.  23.901 
applied to reciprocating engines, the applicant will be required to 
construct and arrange each diesel engine installation to result in 
vibration characteristics that do not

[[Page 34290]]

exceed those established during the type certification of the engine; 
and do not exceed vibration characteristics that a previously 
certificated airframe structure has been approved for, unless such 
vibration characteristics are shown to have no effect on safety or 
continued airworthiness. The engine limit torque design requirements as 
specified in Sec.  23.361 are also modified.
    An additional requirement to consider vibration levels and/or 
effects of an inoperative cylinder was imposed. Also, a requirement to 
evaluate the engine design for the possibility of, or effect of, 
liberating high-energy engine fragments, if a catastrophic engine 
failure occurs, was added.
    Fuel and Fuel System Related Requirements: Due to the use of 
turbine fuel, this airplane must comply with the requirements in Sec.  
23.951(c).
    Section 23.961 will be complied with using the turbine fuel 
requirements. These requirements will substantiated by flight-testing 
as described in Advisory Circular AC 23-8B, Flight Test Guide for 
Certification of Part 23 Airplanes.
    This special condition specifically requires testing to show 
compliance to Sec.  23.961 and adds the possibility of testing non-
aviation diesel fuels.
    To ensure fuel system compatibility and reduce the possibility of 
misfueling, and discounting the first clause of Sec.  23.973(f) 
referring to turbine engines, the applicant will comply with Sec.  
23.973(f).
    Due to the use of turbine fuel, the applicant will comply with 
Sec.  23.977(a)(2), and Sec.  23.977(a)(1) will not apply. ``Turbine 
engines'' will be interpreted to mean ``aircraft diesel engine'' for 
this requirement. An additional requirement imposed is to consider the 
possibility of fuel freezing.
    Due to the use of turbine fuel, the applicant will comply with 
Sec.  23.1305(c)(8).
    Due to the use of turbine fuel, the applicant must comply with 
Sec.  23.1557(c)(1)(ii). Section 23.1557(c)(1)(ii) will not apply. 
``Turbine engine'' is interpreted to mean ``aircraft diesel engine'' 
for this requirement.
    FADEC and Electrical System Requirements: The electrical system 
must comply with the following:
     In case of failure of one power supply of the electrical 
system, there will be no significant engine power change. The 
electrical power supply to the FADEC must remain stable in such a 
failure.
     The transition from the actual engine electrical network 
(FADEC network) to the remaining electrical system with the consumer's, 
avionics, communication, etcetera, should be made by a single point 
only. If several transitions (e.g., for redundancy reasons) are needed, 
then the number of the transitions must be kept as small as possible.
     There must be the ability to separate the FADEC power 
supply (alternator) from the battery and from the remaining electrical 
system.
     In case of loss of alternator power, the installation must 
guarantee that the battery will provide the power for an appropriate 
time after appropriate warning to the pilot.
     FADEC, alternator, and battery must be interconnected in 
an appropriate way, so that in case of loss of battery power, the 
supply to the FADEC is guaranteed by the alternator.
    Limitations and Indications: Section 23.1305, paragraphs (a) and 
(b)(2), will apply, except that propeller revolutions per minute (RPM) 
will be displayed. Sections 23.1305, paragraphs (b)(4) and (b)(5), are 
deleted.
    Additional critical engine parameters for this installation that 
will be displayed include the following:
    (1) Power setting, in percentage, and
    (2) Fuel temperature.
    Due to the use of turbine fuel, the requirements for Sec.  
23.1521(d), as applicable to fuel designation for turbine engines, will 
apply.

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Piper PA 28-161 Cadet, Warrior II and Warrior III series airplanes 
modified by Thielert Aircraft Engines GmbH.
    1. Engine torque (Provisions similar to Sec.  23.361, paragraphs 
(b)(1) and (c)(3)):
    (a) For diesel engine installations, the engine mounts and 
supporting structure must be designed to withstand the following:
    (1) A limit engine torque load imposed by sudden engine stoppage 
due to malfunction or structural failure.
    The effects of sudden engine stoppage may alternately be mitigated 
to an acceptable level by utilization of isolators, dampers clutches 
and similar provisions, so that unacceptable load levels are not 
imposed on the previously certificated structure.
    (b) The limit engine torque to be considered under paragraph 14 CFR 
part 23, Sec.  23.361(a) must be obtained by multiplying the mean 
torque by a factor of four for diesel cycle engines.
    (1) If a factor of less than four is utilized, it must be shown 
that the limit torque imposed on the engine mount is consistent with 
the provisions of Sec.  23.361(c), that is, it must be shown that the 
utilization of the factors listed in Sec.  23.361(c)(3) will result in 
limit torques being imposed on the mount that are equivalent or less 
than those imposed by a conventional gasoline reciprocating engine.
    2. Powerplant--Installation (Provisions similar to Sec.  
23.901(d)(1) for turbine engines):
    Considering the vibration characteristics of diesel engines, the 
applicant must comply with the following:
    (a) Each diesel engine installation must be constructed and 
arranged to result in vibration characteristics that--
    (1) Do not exceed those established during the type certification 
of the engine; and
    (2) Do not exceed vibration characteristics that a previously 
certificated airframe structure has been approved for--
    (i) Unless such vibration characteristics are shown to have no 
effect on safety or continued airworthiness, or
    (ii) Unless mitigated to an acceptable level by utilization of 
isolators, dampers clutches and similar provisions, so that 
unacceptable vibration levels are not imposed on the previously 
certificated structure.
    3. Powerplant--Fuel System--Fuel system with water saturated fuel 
(Compliance with Sec.  23.951 requirements):
    Considering the fuel types used by diesel engines, the applicant 
must comply with the following:
    Each fuel system for a diesel engine must be capable of sustained 
operation throughout its flow and pressure range with fuel initially 
saturated with water at 80 [deg]F and having 0.75cc of free water per 
gallon added and cooled to the most critical condition for icing likely 
to be encountered in operation.
    Methods of compliance that are acceptable for turbine engine fuel 
systems requirements of Sec.  23.951(c) are also considered acceptable 
for this requirement.
    4. Powerplant--Fuel System--Fuel system hot weather operation 
(Compliance with Sec.  23.961 requirements):
    In place of compliance with Sec.  23.961, the applicant must comply 
with the following:
    Each fuel system must be free from vapor lock when using fuel at 
its critical temperature, with respect to vapor formation, when 
operating the airplane in all critical operating and environmental 
conditions for which approval is requested. For turbine fuel,

[[Page 34291]]

or for aircraft equipped with diesel cycle engines that use turbine or 
diesel type fuels, the initial temperature must be 110 [deg]F, -0[deg], 
+5[deg] or the maximum outside air temperature for which approval is 
requested, whichever is more critical.
    The fuel system must be in an operational configuration that will 
yield the most adverse, that is, conservative results.
    To comply with this requirement, the applicant must use the turbine 
fuel requirements and must substantiate these by flight-testing, as 
described in Advisory Circular AC 23-8B, Flight Test Guide for 
Certification of Part 23 Airplanes.
    5. Powerplant--Fuel system--Fuel tank filler connection (Compliance 
with Sec.  23.973(f) requirements):
    In place of compliance with Sec.  23.973(e) and (f), the applicant 
must comply with the following:
    For airplanes that operate on turbine or diesel type fuels, the 
inside diameter of the fuel filler opening must be no smaller than 2.95 
inches.
    6. Powerplant--Fuel system--Fuel tank outlet (Compliance with Sec.  
23.977 requirements):
    In place of compliance with Sec.  23.977(a)(1) the applicant will 
comply with Sec.  23.977(a)(2), except ``diesel'' replaces ``turbine.''
    There must be a fuel strainer for the fuel tank outlet or for the 
booster pump. This strainer must, for diesel engine powered airplanes, 
prevent the passage of any object that could restrict fuel flow or 
damage any fuel system component.
    7. Powerplant--Powerplant Controls and Accessories--Engine ignition 
systems (Compliance with Sec.  23.1165 requirements):
    Considering that the FADEC provides the same function as an 
ignition system for this diesel engine, in place of compliance to Sec.  
23.1165, the applicant will comply with the following:
    The electrical system must comply with the following requirements:
    (a) In case of failure of one power supply of the electrical 
system, there will be no significant engine power change. The 
electrical power supply to the FADEC must remain stable in such a 
failure.
    (b) The transition from the actual engine electrical network (FADEC 
network) to the remaining electrical system should be made at a single 
point only. If several transitions (for example, redundancy reasons) 
are needed, then the number of the transitions must be kept as small as 
possible.
    (c) There must be the ability to separate the FADEC power supply 
(alternator) from the battery and from the remaining electrical system.
    (d) In case of loss of alternator power, the installation must 
guarantee that the battery will provide the power for an appropriate 
time after appropriate warning to the pilot. This period must be at 
least 120 minutes.
    (e) FADEC, alternator and battery must be interconnected in an 
appropriate way, so that in case of loss of battery power, the supply 
to the FADEC is guaranteed by the alternator.
    8. Equipment--General--Powerplant Instruments (Compliance with 
Sec.  23.1305 requirements):
    In place of compliance with Sec.  23.1305, the applicant will 
comply with the following:
    The following are required powerplant instruments:
    (a) A fuel quantity indicator for each fuel tank, installed in 
accordance with Sec.  23.1337(b).
    (b) An oil pressure indicator.
    (c) An oil temperature indicator.
    (d) A tachometer indicating propeller speed.
    (e) A coolant temperature indicator.
    (f) An indicating means for the fuel strainer or filter required by 
Sec.  23.997 to indicate the occurrence of contamination of the 
strainer or filter before it reaches the capacity established in 
accordance with Sec.  23.997(d).
    Alternately, no indicator is required if the engine can operate 
normally for a specified period with the fuel strainer exposed to the 
maximum fuel contamination as specified in MIL-5007D and provisions for 
replacing the fuel filter at this specified period (or a shorter 
period) are included in the maintenance schedule for the engine 
installation.
    (g) Power setting, in percentage.
    (h) Fuel temperature.
    (i) Fuel flow (engine fuel consumption).
    9. Operating Limitations and Information--Powerplant limitations--
Fuel grade or designation (Compliance with Sec.  23.1521(d) 
requirements):
    Instead of compliance with Sec.  23.1521(d), the applicant must 
comply with the following:
    The minimum fuel designation (for diesel engines) must be 
established so that it is not less than that required for the operation 
of the engines within the limitations in paragraphs (b) and (c) of 
Sec.  23.1521.
    10. Markings And Placards--Miscellaneous markings and placards--
Fuel, oil, and coolant filler openings (Compliance with Sec.  
23.1557(c)(1) requirements):
    Instead of compliance with Sec.  23.1557(c)(1)(i), the applicant 
must comply with the following:
    Fuel filler openings must be marked at or near the filler cover 
with--
    For diesel engine-powered airplanes--
    (a) The words ``Jet Fuel''; and
    (b) The permissible fuel designations, or references to the 
Airplane Flight Manual (AFM) for permissible fuel designations.
    (c) A warning placard or note that states the following or similar:
    ``Warning--this airplane equipped with an aircraft diesel engine, 
service with approved fuels only.''
    The colors of this warning placard should be black and white.
    11. Powerplant--Fuel system--Fuel-Freezing:
    If the fuel in the tanks cannot be shown to flow suitably under all 
possible temperature conditions, then fuel temperature limitations are 
required. These will be considered as part of the essential operating 
parameters for the aircraft and must be limitations.
    (1) The takeoff temperature limitation must be determined by 
testing or analysis to define the minimum cold-soaked temperature of 
the fuel that the airplane can operate on.
    (2) The minimum operating temperature limitation must be determined 
by testing to define the minimum operating temperature acceptable after 
takeoff (with minimum takeoff temperature established in (1) above).
    12. Powerplant Installation--Vibration levels:
    Vibration levels throughout the engine operating range must be 
evaluated and:
    (1) Vibration levels imposed on the airframe must be less than or 
equivalent to those of the gasoline engine; or
    (2) Any vibration level that is higher than that imposed on the 
airframe by the replaced gasoline engine must be considered in the 
modification and the effects on the technical areas covered by the 
following paragraphs must be investigated: 14 CFR part 23, Sec. Sec.  
23.251; 23.613; 23.627; CAR 3.159; 23.572; 23.573; 23.574 and 23.901.
    Vibration levels imposed on the airframe can be mitigated to an 
acceptable level by utilization of isolators, dampers clutches and 
similar provisions, so that unacceptable vibration levels are not 
imposed on the previously certificated structure.
    13. Powerplant Installation--One cylinder inoperative:
    It must be shown by test or analysis, or by a combination of 
methods, that the

[[Page 34292]]

airframe can withstand the shaking or vibratory forces imposed by the 
engine if a cylinder becomes inoperative. Diesel engines of 
conventional design typically have extremely high levels of vibration 
when a cylinder becomes inoperative. Data must be provided to the 
airframe installer/modifier so either appropriate design considerations 
or operating procedures, or both, can be developed to prevent airframe 
and propeller damage.
    14. Powerplant Installation--High Energy Engine Fragments:
    It may be possible for diesel engine cylinders (or portions 
thereof) to fail and physically separate from the engine at high 
velocity (due to the high internal pressures). This failure mode will 
be considered possible in engine designs with removable cylinders or 
other non-integral block designs. The following is required:
    (1) It must be shown that the engine construction type (massive or 
integral block with non-removable cylinders) is inherently resistant to 
liberating high energy fragments in the event of a catastrophic engine 
failure; or,
    (2) It must be shown by the design of the engine, that engine 
cylinders, other engine components or portions thereof (fragments) 
cannot be shed or blown off of the engine in the event of a 
catastrophic engine failure; or
    (3) It must be shown that all possible liberated engine parts or 
components do not have adequate energy to penetrate engine cowlings; or
    (4) Assuming infinite fragment energy, and analyzing the trajectory 
of the probable fragments and components, any hazard due to liberated 
engine parts or components will be minimized and the possibility of 
crew injury is eliminated. Minimization must be considered during 
initial design and not presented as an analysis after design 
completion.

    Issued in Kansas City, Missouri on June 7, 2006.
David R. Showers,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E6-9242 Filed 6-13-06; 8:45 am]
BILLING CODE 4910-13-P