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.

Rules and Regulations Federal Register

7335

Vol. 62, No. 33

Wednesday, February 19, 1997

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 oneway 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 § 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 § 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 § 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 § 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
7336 Federal Register / Vol. 62, No. 33 / Wednesday, February 19, 1997 / Rules and Regulations

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 § 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 § 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 § 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 § 21.16 to establish a level of safety

equivalent to that established in the

regulations.

Special conditions, as appropriate, are

issued in accordance with § 11.49 of the

FAR after public notice and opportunity

for comment, as required by §§ 11.28

and 11.29(b), and become part of the

type certification basis in accordance

with § 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 § 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);
Federal Register / Vol. 62, No. 33 / Wednesday, February 19, 1997 / Rules and Regulations 7337

(3) Generate loads greater than those

ultimate loads specified in § 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 § 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
7338 Federal Register / Vol. 62, No. 33 / Wednesday, February 19, 1997 / Rules and Regulations

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 30±3 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

§ 33.83 must be applied to enginefurnished 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