[Federal Register Volume 71, Number 150 (Friday, August 4, 2006)]
[Rules and Regulations]
[Pages 44182-44185]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-12663]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. CE245; Special Condition No. 23-185-SC]


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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued to Aero Propulsion, Inc., 
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 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: July 27, 2006.

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 August 20, 2003, Aero Propulsion, Inc., applied for a 
supplemental type certificate for the installation of an SMA Model 
SR305-230 ADE (type certificated in the United States, type certificate 
number E00067EN) in Piper Model PA28-236 airplanes. Piper Model PA28-
236 airplanes, approved under Type Certificate No. 2A13, are four 
place, single engine airplanes.
    In anticipation of 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, and the 
vibration characteristics and failure modes of diesel engines. These 
concerns were identified after review of the historical record of 
diesel engine used 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 Aero Propulsion installation, and after 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 include special conditions for HIRF and application of 
Sec.  23.1309 provisions to

[[Page 44183]]

the Full Authority Digital Engine Control (FADEC).

Type Certification Basis

    Under the provisions of Sec.  21.101, Aero Propulsion, Inc., must 
show that the Piper Model PA28-236 airplanes, with the installation of 
an SMA Model SR305-230 ADE, continue to meet the applicable provisions 
of 14 CFR part 23 and 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.
    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 ADE 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 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, will incorporate an aircraft 
diesel engine utilizing turbine (jet) fuel.

Discussion of Comments

    A notice of proposed special conditions No. 23-06-03-SC for Aero 
Propulsion, Inc., for the Piper Model PA28-236 airplanes, with the 
installation of an SMA Model SR305-230 ADE, was published on June 14, 
2006 (71FR 34292). No comments were received, and the special 
conditions are adopted as proposed.

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. Should Aero Propulsion, Inc., 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 the Piper Model PA28-236 airplanes, with the installation of an SMA 
Model SR305-230 ADE. 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

0
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

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued to Aero 
Propulsion, Inc., as part of the type certification basis for the Piper 
Model PA28-236 airplanes, with the installation of an SMA Model SR305-
230 ADE.
    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

[[Page 44184]]

    (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:
    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 indicator.
    (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

[[Page 44185]]

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 July 27, 2006.
James E. Jackson,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E6-12663 Filed 8-3-06; 8:45 am]
BILLING CODE 4910-13-P