[Federal Register Volume 71, Number 114 (Wednesday, June 14, 2006)]
[Proposed Rules]
[Pages 34292-34295]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-9227]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE245; Notice No. 23-06-03-SC]


Special Conditions: Aero Propulsion, Inc., Piper Model PA28-236; 
Diesel Cycle Engine Using Turbine (Jet) Fuel

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for the Piper Model 
PA28-236 airplanes with a Societe de Motorisation Aeronautiques (SMA) 
Model SR305-230 Aircraft Diesel Engine (ADE). This airplane 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. CE245, 901 Locust, Room 506, Kansas City, 
Missouri 64106, or delivered in duplicate to the Regional Counsel at 
the above address. Comments must be marked: CE245. 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 CE245.'' The postcard will be date 
stamped and returned to the commenter.

Background

    On August 20, 2003, Aero Propulsion, Inc., applied for a 
supplemental type certificate for Piper Model PA28-236 airplanes with 
the installation of an SMA Model SR305-230. The airplane is powered by 
a SMA Model SR305-230 ADE, type certificated in the United States, type 
certificate number E00067EN.
    Before the reintroduction of 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 
SMA installation, and applying the provisions of the diesel policy, the 
FAA proposes these fuel system and engine related special conditions. 
Other special conditions issued in a separate notice include special 
conditions for HIRF and application of Sec.  23.1309 provisions to

[[Page 34293]]

the Full Authority Digital Engine Control (FADEC).

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Aero Propulsion, Inc., must 
show that the Piper Model PA28-236 airplanes with the installation of 
an SMA Model SR305-230 ADE meet the applicable provisions of 14 CFR 
part 23 and Civil Air Regulations (CAR) 3 thereto. In addition, the 
certification basis includes special conditions and equivalent levels 
of safety for the following:
    Special Conditions:
     Engine torque (Provisions similar to Sec.  23.361, 
paragraphs (b)(1) and (c)(3)).
     Flutter (Compliance with Sec.  23.629, paragraphs (e)(1) 
and (2)).
     Powerplant--Installation (Provisions similar to Sec.  
23.901(d)(1) for turbine engines).
     Powerplant--Fuel System--Fuel system with water saturated 
fuel (Compliance with Sec.  23.951 requirements).
     Powerplant--Fuel System--Fuel system hot weather operation 
(Compliance with Sec.  23.961 requirements).
     Powerplant--Fuel system--Fuel tank filler connection 
(Compliance with Sec.  23.973(f) requirements).
     Powerplant--Fuel system--Fuel tank outlet (Compliance with 
Sec.  23.977 requirements).
     Equipment--General--Powerplant Instruments (Compliance 
with Sec.  23.1305 requirements).
     Operating Limitations and Information--Powerplant 
limitations--Fuel grade or designation (Compliance with Sec.  
23.1521(d) requirements).
     Markings and Placards--Miscellaneous markings and 
placards--Fuel, oil, and coolant filler openings (Compliance with Sec.  
23.1557(c)(1) requirements).
     Powerplant--Fuel system--Fuel-Freezing.
     Powerplant Installation--Vibration levels.
     Powerplant Installation--One cylinder inoperative.
     Powerplant Installation--High Energy Engine Fragments.
    Equivalent levels of safety for:
     Cockpit controls--23.777(d).
     Motion and effect of cockpit controls--23.779(b).
     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 Model PA28-236 airplanes with the 
installation of an SMA Model SR305-230 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 Model PA28-236 airplanes with the installation of 
an SMA Model SR305-230 ADE must comply with 14 CFR 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 Model PA28-236 airplanes with the installation of an SMA 
Model SR305-230 ADE will incorporate the following novel or unusual 
design features:
    The Piper Model PA28-236 airplanes with the installation of an SMA 
Model SR305-230 ADE will require the use of turbine (jet) fuel.

Applicability

    As discussed above, these special conditions are applicable to the 
Piper Model PA28-236 airplanes with the installation of an SMA Model 
SR305-230 ADE.

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 the development of FAA policy deal 
with several things. These include the installation of the diesel 
engine and its vibration levels under normal operating conditions and 
with one cylinder inoperative, the accommodation of 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 aircraft diesel 
engine installation 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 according to 
certain restrictions. These include arranging the installation so 
vibration characteristics do not exceed those established during the 
type certification of the engine. The engine installation will also be 
required to 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 was 
added to evaluate the engine design for the possibility of, or effect 
of, liberating high-energy engine fragments, in the event of a 
catastrophic engine failure.
    Fuel and Fuel System Related Requirements: Due to the use of 
turbine

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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 be substantiated by flight-tests 
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 of the possibility of fuel 
freezing was imposed.
    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)(i) will not apply. 
``Turbine engine'' is interpreted to mean ``aircraft diesel engine'' 
for this requirement.
    Limitations and Indications: Critical engine parameters for this 
installation that will be displayed include the following:
    (1) 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 Model PA28-236 airplanes with an SMA SR305-230 ADE installed.
    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 obtained in CAR 3.195(a)(1) and (a)(2) 
or 14 CFR 23.361(a)(1) and (a)(2) must be obtained by multiplying the 
mean torque by a factor of four in lieu of the factor of two required 
by CAR 3.195(b) and 14 CFR 23.361(c)(3).
    2. Flutter--(Compliance with the requirements of Sec.  23.629 
(e)(1) and (e)(2) requirements):
    The flutter evaluation of the airplane done in accordance with 14 
CFR 23.629 must include--
    (a) Whirl mode degree of freedom which takes into account the 
stability of the plane of rotation of the propeller and significant 
elastic, inertial, and aerodynamic forces, and
    (b) Propeller, engine, engine mount and airplane structure 
stiffness and damping variations appropriate to the particular 
configuration, and
    (c) The flutter investigation will include showing the airplane is 
free from flutter with one cylinder inoperative.
    3. 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.
    4. 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.
    5. Powerplant--Fuel System--Fuel flow (Compliance with Sec.  
23.955(c) requirements):
    In lieu of 14 CFR 23.955(c), engine fuel system must provide at 
least 100 percent of the fuel flow required by the engine, or the fuel 
flow required to prevent engine damage, if that flow is greater than 
100 percent. The fuel flow rate must be available to the engine under 
each intended operating condition and maneuver. The conditions may be 
simulated in a suitable mockup. This flow must be shown in the most 
adverse fuel feed condition with respect to altitudes, attitudes, and 
any other condition that is expected in operation.
    6. 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, 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.
    7. 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.
    8. Powerplant--Fuel system--Fuel tank outlet (Compliance with Sec.  
23.977 requirements):
    In place of compliance with Sec.  23.977(a)(1) and (a)(2), the 
applicant will comply with the following:

[[Page 34295]]

    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.
    9. Equipment--General--Powerplant Instruments (Compliance with 
Sec.  23.1305):
    In addition to compliance with Sec.  23.1305, the applicant will 
comply with the following:
    The following are required in addition to the powerplant 
instruments required in Sec.  23.1305:
    (a) A fuel temperature indictor.
    (b) An outside air temperature (OAT) indicator.
    (c) 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 certain requirements are 
met. First, the engine can operate normally for a specified period with 
the fuel strainer exposed to the maximum fuel contamination as 
specified in MIL-5007D. Second, provisions for replacing the fuel 
filter at this specified period (or a shorter period) are included in 
the maintenance schedule for the engine installation.
    10. Operating Limitations and Information--Powerplant limitations--
Fuel grade or designation (Compliance with Sec.  23.1521 requirements):
    All engine parameters that have limits specified by the engine 
manufacturer for takeoff or continuous operation must be investigated 
to ensure they remain within those limits throughout the expected 
flight and ground envelopes (e.g. maximum and minimum fuel 
temperatures, ambient temperatures, as applicable, etc.). This is in 
addition to the existing requirements specified by 14 CFR 23.1521 (b) 
and (c). If any of those limits can be exceeded, there must be 
continuous indication to the flight crew of the status of that 
parameter with appropriate limitation markings.
    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.
    11. 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), 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.
    12. 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.
    A minimum takeoff temperature limitation will be determined by 
testing to establish the minimum cold-soaked temperature at which the 
airplane can operate. The minimum operating temperature will be 
determined by testing to establish the minimum operating temperature 
acceptable after takeoff from the minimum takeoff temperature. If low 
temperature limits are not established by testing, then a minimum 
takeoff and operating fuel temperature limit of 5 [deg]F above the 
gelling temperature of Jet A will be imposed along with a display in 
the cockpit of the fuel temperature. Fuel temperature sensors will be 
located in the coldest part of the tank if applicable.
    13. 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; 23.629 (or CAR 
3.159, as applicable to various models); 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.
    14. Powerplant Installation--One cylinder inoperative:
    It must be shown by test or analysis, or by a combination of 
methods, that the 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.
    No unsafe condition will exist in the case of an inoperative 
cylinder before the engine can be shut down. The resistance of the 
airframe structure, propeller, and engine mount to shaking moment and 
vibration damage must be investigated. It must be shown by test or 
analysis, or by a combination of methods, that shaking and vibration 
damage from the engine with an inoperative cylinder will not cause a 
catastrophic airframe, propeller, or engine mount failure.
    15. 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 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
    (2) It must be shown that all possible liberated engine parts or 
components do not have adequate energy to penetrate engine cowlings; or
    (3) 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. E6-9227 Filed 6-13-06; 8:45 am]
BILLING CODE 4910-13-P