[Federal Register Volume 62, Number 33 (Wednesday, February 19, 1997)]
[Rules and Regulations]
[Pages 7335-7338]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-4067]
========================================================================
Rules and Regulations
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains regulatory documents
having general applicability and legal effect, most of which are keyed
to and codified in the Code of Federal Regulations, which is published
under 50 titles pursuant to 44 U.S.C. 1510.
The Code of Federal Regulations is sold by the Superintendent of Documents.
Prices of new books are listed in the first FEDERAL REGISTER issue of each
week.
========================================================================
Federal Register / Vol. 62, No. 33 / Wednesday, February 19, 1997 /
Rules and Regulations
[[Page 7335]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 33
[Docket No. 93-ANE-14; No. 33-ANE-01]
Special Conditions; Soloy Corporation, Soloy Dual Pac Engine
(Formally Soloy Dual Pac, Inc.)
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final special conditions.
-----------------------------------------------------------------------
SUMMARY: These special conditions are issued for the Soloy Corporation,
Soloy Dual Pac engine (formally Soloy Dual Pac Inc.). This engine will
have a novel design feature associated with its configuration. The
Soloy Dual Pac engine is a propulsion system in which two Pratt &
Whitney Canada (PWC) Model PT6 turbine engines are combined through a
common gearbox to drive a single output propeller shaft. The Soloy Dual
Pac engine is intended to provide a degree of continuous operation
following the failure of one of the PWC Model PT6 engines. The
applicable regulations do not contain adequate or appropriate safety
standards for such a configuration. These special conditions contain
the additional safety standards which the Administrator considers
necessary to establish a level of safety equivalent to that established
by the airworthiness standards of part 33 of the Federal Aviation
Regulations (FAR).
EFFECTIVE DATES: March 21, 1997.
FOR FURTHER INFORMATION CONTACT:
Kathrine Rask, Seattle Aircraft Certification Office, Propulsion
Branch, ANM-140S, FAA, Northwest Mountain Region, 1601 Lind Avenue SW.,
Renton, Washington 98055-4056, Telephone (206) 227-1547; fax (206) 227-
1181.
SUPPLEMENTARY INFORMATION:
Background
General
On November 9, 1990, Soloy Corporation applied for a supplemental
type certificate for the Soloy Dual Pac engine. The Soloy Dual Pac
engine is a propulsion concept in which two PWC Model PT6 engines,
currently approved under Type Certificate No. E4EA, drive a single
propeller shaft through a combining gearbox. The Soloy Dual Pac engine
incorporates redundant freewheeling, drive, governing, and lubricating
systems. A system of one-way clutches both prevents the propeller shaft
from driving the engine input shafts and allows either engine to drive
the propeller should the other engine fail. The supplemental type
certificate for the Soloy Dual Pac engine is to be based on the type
certificate of the PWC Model PT6 engine. On February 4, 1994, the FAA
published a notice of proposed special conditions (59 FR 5356) for
``Soloy Dual Pac, Inc., Soloy Dual Pac Engine'', requesting public
comments. Since that publication, the name has changed from Soloy Dual
Pac, Inc., to Soloy Corporation.
Safety Analysis
The certification basis of the PWC Model PT6 engine was established
before the introduction of Sec. 33.75 of the Federal Aviation
Regulation (FAR) (Safety Analysis). Section 33.75 addresses four types
of engine failure conditions which are particularly hazardous to the
safety of the aircraft. The objective of Sec. 33.75 is to require an
analysis to be performed at the engine level which establishes that any
probable single or multiple failure, or any probable improper operation
will not cause the engine to catch fire, burst, generate loads greater
than the ultimate loads for the engine mount, or lose the capability to
shut down. Consequently, it is considered appropriate to add a safety
analysis requirement to the Soloy Dual Pac engine program.
Also, one objective of the Soloy Dual Pac engine is to provide
continued operation after the failure of one PWC Model PT6 engine.
While the safety analysis regulations of Sec. 33.75 are more extensive
than those of the PWC Model PT6 engine certification basis, they still
do not address this special ``continue to run'' objective.
Therefore, in light of the above, it was proposed that a safety
analysis requirement, modeled after Sec. 33.75 and expanded to address
continued operation after a single engine failure, be included in the
Soloy Dual Pac engine certification basis.
Uncontained Engine Failure
It is assumed that the Soloy Dual Pac engine is intended for use in
an aircraft and will be part of an aircraft certification program in
the future. Minimizing the hazards to the aircraft from uncontained
engine debris will be a very important requirement in any such
certification program. In addition, for a design such as the Dual Pac,
many design features intended to minimize such hazards would be
determined at the engine design stage. Therefore, this issue must be
addressed initially during the Soloy Dual Pac engine certification
program, and may also be addressed during the aircraft installation
certification program.
As stated above, one objective of a Soloy Dual Pac engine-equipped
aircraft could be continued safe flight and landing after the failure
of one PWC Model PT6 engine. In order for the Soloy Dual Pac engine to
achieve this objective, it must continue to produce adequate and
controllable torque after such a failure. Service experience, however,
shows that uncontained engine failures can result in high velocity
fragment penetration of, among other things, other engines. This could
render the other engine inoperative as well. In the case of the Soloy
Dual Pac engine, such an event could end all torque production.
Therefore, the Soloy Dual Pac engine must demonstrate that the two PWC
Model PT6 engines should be protected from each other in order to
minimize the hazards associated with this event.
Gearbox Design, Functioning, and Endurance Testing
Power transmission systems, such as gearboxes, have not been
specifically addressed by engine certification regulations. Previously,
engines incorporating gearboxes, such as fan reduction gearing or
accessory gearboxes, have been evaluated during the course of engine
block tests and other engine certification activities. Transmissions
such as those used in
[[Page 7336]]
rotorcraft, however, have been addressed in rotor drive criteria
contained in rotorcraft certification regulations. Since the Soloy Dual
Pac engine propulsion drive system is part of the engine, the changes
to part 23 of the FAR, which were published as a notice of proposed
rulemaking (NPRM), ``Small Airplane Airworthiness Review Program Notice
No. 3,'' in the Federal Register on October 3, 1990 (55 FR 40598); and
Sec. 33.87 of the FAR (amended through Amendment 33-5), will be used as
a basis for special conditions intended to establish standards to
address the design, function, and endurance testing of the gearbox.
Section 33.87 regulations have been included in order to establish a
comprehensive standards to address the turbine interface with the
gearbox.
Type Certification Basis
Under the provisions of Sec. 21.101 of the FAR, Soloy Corporation,
must show that the Soloy Dual Pac engine meets the applicable
provisions of the regulations incorporated by reference in Type
Certificate No. E4EA, or the requirements of the applicable regulations
in effect on the date of the application. 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. E4EA are as follows:
(a) FAR Sec. 21.29, Issue of Type Certificate: Import Products.
(b) Civil Air Regulations (CAR) part 10, Certification and Approval
of Import Aircraft and Related Products, dated March 28, 1955.
(c) FAR part 33, Airworthiness Standards: Aircraft Engines,
effective February 1, 1965, as amended by Amendments 33-1 through 33-5
inclusive.
If the regulations incorporated by reference do not provide
adequate standards with respect to the change, the applicant must
comply with the regulations in effect on the date of application for
the change that the FAA finds necessary to provide a level of safety
equal to that established by the regulations incorporated by reference.
Due to the potential applications of the Soloy Dual Pac engine, the FAA
has determined that it must also be shown to comply with part 33 of the
FAR, effective February 1, 1965, as amended by Amendment 33-1 through
33-5 inclusive, plus the following sections:
(a) Section 33.7, Amendment 33-12, Engine ratings and operating
limitations.
(b) Section 33.67, Amendment 33-10, Fuel system.
(c) Section 33.68, Amendment 33-10, Induction system icing.
(d) Section 33.96, Amendment 33-11, Engine test in auxiliary power
unit mode.
(e) Section 21.115(a), Applicable requirements.
In addition, compliance must be shown with part 34 of the FAR (Fuel
Venting and Exhaust Emission Requirements for Turbine Engine Powered
Airplanes); these special conditions contained herein on safety
analysis, gearbox design, functioning, and endurance testing, and
uncontained engine failure; as well as any applicable equivalent safety
findings and any applicable exemptions.
The Administrator finds that the applicable airworthiness
regulations in part 33, as amended, do not contain adequate or
appropriate safety standards for the Soloy Dual Pac engine because of
its novel or unusual design feature. Therefore, the Administrator
prescribes special conditions under the provision of Sec. 21.16 to
establish a level of safety equivalent to that established in the
regulations.
Special conditions, as appropriate, are issued in accordance with
Sec. 11.49 of the FAR after public notice and opportunity for comment,
as required by Secs. 11.28 and 11.29(b), and become part of the type
certification basis in accordance with Sec. 21.101(b)(2).
Discussion of Comments
Interested persons have been afforded the opportunity to
participate in the making of these special conditions. One comment were
received supporting the additional safety standards for the Soloy Dual
Pac engine in the notice of proposed special conditions as published.
The FAA has gained a better technical understanding of the Soloy
Dual Pac engine design since the notice of proposed special conditions
were published in the Federal Register.
One of the critical systems of the Soloy Dual Pac engine is the
single propeller. Paragraph(c)(1)(iv) was developed to ensure that a
loss of oil pressure to the propeller governing system or the propeller
shaft lubrication would not result in imminent loss of propeller speed
or control. The zero oil pressure test as published in the notice of
proposed special conditions does not adequately address these concerns.
The blade pitch control system of the Soloy Dual Pac engine propeller
installation is expected to contain a fail safe setting that is not
equivalent to the 100 percent output speed required in the notice of
proposed special conditions. When the propeller governor looses oil
pressure, it will automatically revert to a predetermined mechanical
limit, a so called ``get home'' pitch and speed. In addition, the 15
minute requirement (the notice of proposed special conditions stated
``15 seconds,'' however this was a typographical error) is not adequate
for the type of aircraft installations where the Soloy Dual Pac is
expected to be used. These airplanes, operating under part 121 of the
FAR, will be allowed to operate over routes that contain a point up to
one hour flying time from an adequate airport. The test of less than
one hour of continued safe operation would not fulfill the intent of
the paragraph (c)(1)(iv). The FAA has determined that paragraph
(c)(1)(iv) as proposed, which set forth requirements for a zero oil
pressure test of the gearbox, does not address the intent of this
paragraph and therefore it is modified in these final special
conditions. The revised test requirements in the final special
conditions address more accurately the airplane failure scenario
intended to be evaluated. However, the demonstrated torque and
rotational speed must be included in the instruction manual for
installing and operating the engine required in Sec. 33.5 of the FAR.
Conclusion
This action affects only certain novel or unusual design features
on one model engine configuration. It is not a rule of general
applicability, and affects only the manufacturer who applied to the FAA
for approval of these features on the engine.
List of Subjects in 14 CFR Part 33
Air transportation, Aircraft, Aviation safety, Safety.
The authority citation for part 33 continues to read as follows:
Authority: 49 U.S.C. 106(g); 40113, 44701, 44702, 44704
The Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for the Soloy Corporation, Soloy Dual Pac
engine:
(a) Safety Analysis.
It must be shown by analysis that any probable malfunction, or any
probable single or multiple failure, or any probable improper operation
of the Soloy Dual Pac engine will not cause the Soloy Dual Pac engine
to--
(1) Catch fire;
(2) Burst (release hazardous fragments through the engine case);
[[Page 7337]]
(3) Generate loads greater than those ultimate loads specified in
Sec. 33.23(a);
(4) Lose the capability of being shut down; or
(5) Lose the capability of providing controllable 50 percent of
rated power.
(b) Uncontained Engine Failure.
Design precautions must be taken to minimize the damage to one PWC
PT6 engine, in the event of uncontained engine failure of the other PWC
Model PT6 engine, in order for the unfailed engine to be capable of
continued torque production after such a failure.
(c) Gearbox Design, Functioning, and Endurance Testing.
(1) Propulsion Drive System Design. Propulsion drive systems, as
defined in paragraph (c)(1)(i), must meet the requirements as set forth
in paragraphs (c) (1) through (6).
(i) The propulsion drive system includes all parts necessary to
transmit power from the engines to the propeller shaft. This includes
couplings, universal joints, drive shafts, supporting bearings for
shafts, brake assemblies, clutches, gearboxes, transmissions, any
attached accessory pads or drives, and any cooling fans that are
attached to, or mounted on, the propulsion drive system.
(ii) Each propulsion drive system, powered by more than one engine,
must be arranged so that the propeller shaft and its control will
continue to be powered by the remaining engine(s) if any engine fails.
(iii) Each multiengined propulsion drive system must incorporate a
device to automatically disengage any engine from the propeller shaft,
if that engine fails.
(iv) The oil for components of the propulsion drive system that
require continuous lubrication must be sufficiently independent of the
lubrication systems of the engine(s) to ensure operation with any
engine inoperative. The propulsion drive system must be able to
continue safe operation, although not necessarily without damage, at a
torque and rotational speed prescribed by the applicant which is
determined to be the most critical of the anticipated flight
conditions. The drive system shall operate at this condition for at
least one hour after perception by the flight crew of the lubrication
system failure or loss of lubricant. The demonstrated torque and
rotational speed must be included in the instructional manual for
installing and operating the engine required in Sec. 33.5 of the
Federal Aviation Regulations (FAR).
(v) Torque limiting means must be provided on all accessory drives
that are located on the propulsion drive system, in order to prevent
the torque limits established for those drives from being exceeded.
(vi) There must be means to provide continued propulsion system
control and operation, following the failure of an engine to
transmission drive shaft.
(vii) In addition to the propulsion drive system complying with the
requirements of paragraph (c)(1)(iii), the propulsion drive system,
powered by more than one engine, must be designed so that torque to the
propeller shaft is not interrupted after failure of any engine or
element in the propeller shaft drive system; and examined in detail to
determine all components and their failure modes that would be vital to
continued control and operation of the propulsion drive system.
(viii) For each component and its failure modes identified by this
examination, it must be shown by appropriate test that such a failure
is not likely to occur in the system component's service life
established by these tests; or that the system is designed so continued
control and operation can be accomplished after occurrence of the
failure.
(2) Propulsion Drive System Limitations. The propulsion drive
system limitations must be established so that they do not exceed the
corresponding limits approved for the engine, propeller shaft, and
drive system components.
(i) For the Soloy Dual Pac engine, takeoff power must be limited
by--
(A) The powerplant maximum rotational speed for takeoff power, and
the maximum rotational propeller shaft speed may not be greater than
the values determined by the propulsion drive system type design, or
the maximum value shown during type tests.
(B) The time limit for the use of power, gas temperature, and speed
corresponding to the limitations established in paragraph (i) of this
section.
(C) The powerplant maximum allowable gas temperature at maximum
allowable power or torque for each engine, considering the power input
limitations of the transmission with all engines operating; and
(D) The powerplant maximum allowable gas temperature at maximum
allowable or torque of each engine, considering the power input
limitations of the transmission with one engine inoperative.
(ii) For the Soloy Dual Pac engine, continuous power must be
limited by--
(A) The powerplant maximum rotational speed for continuous power.
The maximum rotational propeller shaft speed may not be greater than
the values determined by the propulsion drive system type design
maximum value shown during type tests.
(B) The powerplant maximum allowable gas temperature of continuous
power and the maximum allowable power or torque for each engine,
considering the power input limitations of the transmission with both
engines operating; and
(C) Powerplant maximum allowable gas temperature at maximum
allowable power or torque of each engine, considering the power input
limitations of the transmission with one engine inoperative.
(3) Propulsion Drive System Instruments. Connections for the
following instruments must be provided for any gearbox or transmission:
(i) An oil pressure warning device for each pressure-lubricated
gearbox to indicate when the oil pressure falls below a safe value;
(ii) A low oil quantity warning indicator for each gear box, if
lubricant is self-contained;
(iii) An oil temperature warning device to indicate unsafe oil
temperatures in each gearbox;
(iv) A tachometer for each propeller shaft;
(v) A torquemeter for each transmission driving a propeller shaft;
and
(vi) A chip detecting and indicating system for each gearbox.
(4) Propulsion Drive System Endurance Tests. Each part tested, as
prescribed in this section, must be in a serviceable condition at the
end of the tests. No intervening disassembly that might affect these
results may be conducted.
(i) Endurance tests; general. The propulsion system, as defined in
paragraph (c)(1) must be tested as prescribed in paragraphs (c)(4)(ii)
through (c)(4)(ix), for at least 200 hours plus the time required to
meet paragraph (c)(4)(ix). For the 200-hour portion, these tests must
be conducted as follows:
(A) Twenty each, ten-hour test cycles consisting of the test times
and procedures in paragraphs (c)(4)(ii) through (c)(4)(viii); and
(B) The test torque must be determined by actual powerplant
limitations.
(ii) Endurance tests; takeoff torque run. The takeoff torque run
endurance test must be conducted as follows:
(A) The takeoff torque run must consist of a one-hour run on the
engine(s) at the torque corresponding to takeoff power, but with the
engine power setting alternately cycled every
[[Page 7338]]
five minutes to as low an engine idle speed as practicable.
(B) Deceleration and acceleration of the engines and/or of
individual engines and drive system must be performed at the maximum
rate. (This corresponds to a one-second power setting change from idle
to takeoff setting, and one second from takeoff setting to idle.)
(C) The time duration of all engines at takeoff power setting must
total one hour and does not include the time required to go from
takeoff to idle and back to take off speed.
(iii) Endurance tests; maximum continuous run. Three hours of
continuous operation, at the torque corresponding to maximum continuous
power and speed, must be conducted.
(iv) Endurance tests; 90 percent of maximum continuous run. One
hour of continuous operation, at the torque corresponding to 90 percent
of maximum continuous power, must be conducted at maximum continuous
rotational propeller shaft speed.
(v) Endurance tests; 80 percent of maximum continuous run. One hour
of continuous operation, at the torque corresponding to 80 percent of
maximum power, must be conducted at the minimum rotational propeller
shaft speed intended for this power.
(vi) Endurance tests; 60 percent of maximum continuous run. Two
hours of continuous operation, at the torque corresponding to 60
percent of maximum continuous power, must be conducted at the minimum
rotational propeller shaft speed intended for this power.
(vii) Endurance tests; engine malfunctioning run. It must be
determined whether malfunctioning of components, such as the engine
fuel or ignition systems, or unequal engine power can cause dynamic
conditions detrimental to the drive system. If so, a suitable number of
hours of operation must be accomplished under those conditions, one
hour of which must be included in each cycle, and the remaining hours
of which must be accomplished at the end of 20 cycles. This testing is
to be equally divided between the following four conditions: (1) engine
#1 ``ON''/engine #2 ``IDLE''; (2) engine #1``ON''/engine #2 ``OFF'';
(3) engine #1 ``IDLE''/engine #2 ``ON''; (4) engine #1 ``OFF''/engine
#2 ``ON''. If no detrimental conditions results, an additional hour of
operation in compliance with paragraph (ii) of this section must be
conducted.
(viii) Endurance tests; overspeed run. One hour of continuous
operation must be conducted at the torque corresponding to maximum
continuous power, and at 110 percent of rated maximum continuous
rotational propeller shaft speed. if the overspeed is limited to less
than 110 percent of maximum continuous speed by the speed and torque
limiting devices, the speed used must be the highest speed allowable,
assuming that speed and torque limiting devices, if any, function
properly.
(ix) Endurance tests; one-engine-out application. A total of 160
full differential power applications must be made at takeoff torque and
RPM. If, during these tests, it is found that a critical dynamic
condition exists, an investigative assessment to determine the cause
shall be performed throughout the torque/speed range. In each of the
160 engine power setting cycles (160 per engine drive branch) a full
differential power application must be performed. In each cycle, the
transition from clutch engagement to disengagement must occur at the
critical condition for clutch and shaft wear.
(5) Additional Propulsion Drive System Tests. Additional dynamic,
endurance, and operational test and vibratory investigations must be
performed to determine that the drive mechanism is safe. The following
additional tests and conditions apply:
(i) If the torque output of all engines to the transmission can
exceed the highest engine or transmission torque limit, the following
tests must be conducted. Under conditions associated with all engines
operating, apply 200 cycles to the drive system for 10 seconds each of
a torque that is at least equal to the lesser of--
(A) The maximum torque used in complying with paragraph (4)(ii)
plus 10 percent; or
(B) The maximum torque attainable under normal operating
conditions, assuming that any torque limiting devices function
properly.
(ii) With each engine alternately inoperative, apply to the
remaining transmission inputs the maximum transient torque attainable
under normal operating condition, assuming that any torque limiting
devices function properly. Each transmission input must be tested at
this maximum torque for at least 15 minutes.
(iii) After completion of the 200 hour endurance test and without
intervening major disassembly, the drive system must be subjected to 50
overspeed runs, each 303 seconds in duration, at a speed of
at least 120 percent of maximum continuous speed, or other maximum
overspeed that is likely to occur, plus a margin of speed approved by
the Administrator for that overspeed condition. These runs must be
conducted as follows:
(A) Overspeed runs must be alternated with stabilizing runs from 1
to 5 minutes duration, each 60 to 80 percent of maximum continuous
speed.
(B) Acceleration and deceleration must be accomplished in a period
no longer than 10 seconds, and the time for changing speeds may not be
deducted from the specified time for the overspeed runs.
(iv) Each part tested, as prescribed in this section, must be in
serviceable condition at the end of the tests. No intervening
disassembly that might affect test results may be conducted.
(v) If drive shaft couplings are used and shaft misalignment or
deflections are probable, loads must be determined in establishing the
installation limits affecting misalignment. These loads must be
combined to show adequate fatigue life.
(vi) The vibration test specified in Sec. 33.83 must be applied to
engine-furnished components of the propulsion drive system. The test
must include the gear case and each component in the combining gear box
whose failure due to vibration could cause unsafe operation of the
engine.
(6) Propulsion Drive System Shafting Critical Speed. The critical
speeds of any shafting must be determined by test, except that
analytical methods may be used if reliable methods of analysis are
available for the particular design.
(i) If any critical speed lies within, or close to, the operating
ranges for idling and power on conditions, the stresses occurring at
that speed must be within design limits. This must be shown by tests.
(ii) If analytical methods are used and show that no critical speed
lies within the permissible operating ranges, the margins between the
calculated critical speeds and the limits of the allowable operating
ranges must be adequate to allow for possible variations between the
computed and actual values.
Issued in Burlington, Massachusetts, on February 7, 1997.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 97-4067 Filed 2-18-97; 8:45 am]
BILLING CODE 4910-13-M