[Federal Register Volume 65, Number 249 (Wednesday, December 27, 2000)]
[Rules and Regulations]
[Pages 81729-81731]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-32883]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. NE-123; Special Conditions No. 33-004-SC]


Special Conditions: Pratt & Whitney Canada, Inc. (Formerly United 
Aircraft of Canada, Limited), Model PT6T-9 Turboshaft Engine

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions, request for comments.

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SUMMARY: Pratt & Whitney Canada, Inc. (PWC) has applied for an 
amendment to type certificate (TC) #E22EA, to add a new model PT6T-9 
turboshaft engine. The FAA has determined that this new model engine 
should be viewed as a derivative to the PT6T-3 engine. On June 8, 1970, 
the FAA issued Special Conditions (SC) No. 33-23-EA-6 for the PT6T-3 
turboshaft engine model, and later amended those SC in 1970 to clarify 
a potential ambiguity in the vibration test requirements. In addition 
to the requirements contained in SC No. 33-23-EA-6, as amended, these 
new special conditions provide for 30-second one-engine-inoperative 
(OEI), 2-minute OEI, and continuous OEI ratings to be included in the 
PT6T-9 turboshaft engine model power ratings. The special conditions 
will define the changes to the engine certification basis that are 
required to establish a level of safety equivalent to the current 
requirements of 14 CFR part 33, for the new PWC PT6T-9 turboshaft 
engine model.

DATES: The effective date of these special conditions is December 27, 
2000. Comments must be received on or before January 26, 2001.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration (FAA), Office of the 
Regional Counsel, Attention: Docket No. NE-123; 12 New England 
Executive Park, Burlington, MA 01803-5299, or delivered in duplicate to 
the Office of Regional Counsel at the above address. Comments must be 
marked: Docket No. NE-123. Comments may be inspected at this location 
on weekdays, except Federal holidays, between 8 a.m. and 4:30 p.m.

FOR FURTHER INFORMATION CONTACT: Mr. Chung Hsieh, Aerospace Engineer, 
Engine and Propeller Standards Staff, ANE-110, Engine and Propeller 
Directorate, Aircraft Certification Service, FAA, 12 New England 
Region, 12 New England Executive Park, Burlington, Massachusetts 01803-
5299; telephone 781-238-7115, Fax 781-238-7199. If you have access to 
the Internet, you may also obtain further information by writing to the 
following Internet address: ``[email protected]''.

SUPPLEMENTARY INFORMATION:   

Comments Invited

    The FAA has determined that good cause exists for making these 
special conditions effective upon issuance; however, interested persons 
are invited to submit such written data, views, or arguments, as they 
may desire. Communications should identify the docket number and 
special conditions number, and be submitted in duplicate to the address 
specified above, or, if you have access to the internet, you may make a 
submission to the following Internet address: ``[email protected]''. 
All communications received on or before the closing date for comments 
will be considered by the Administrator. These special conditions may 
be changed depending on the comments received. All comments received 
will be available in the 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 request must include a self-addressed, stamped postcard on 
which the following statement is made: ``Comments to Docket No. NE-
123.'' The postcard will be date stamped and returned to the commenter.

Background

    On March 28, 2000, Pratt & Whitney Canada, Inc. applied for an 
amendment to type certificate (TC) E22EA for a new derivative engine, 
the PT6T-9 turboshaft engine model. The PT6T-9 turboshaft engine 
configuration is similar to the PT6T-3 series turboshaft engine models. 
These engines have two identical free-turbine power-sections coupled to 
a common mixing gearbox module with a single output shaft. The common 
mixing gearbox module reduces the turbine speed of the power-sections 
to a single output speed through a pair of overrunning clutches and 
reduction gearing. In addition, the common mixing gearbox contains a 
torquemeter for each power-section and a unique and unusual oil system 
configuration. The oil for engine components requiring continuous 
lubrication is provided by two independent lubrication systems, one for 
each of the power-sections, to ensure operation with any one power-
section inoperative. The FAA issued Special Conditions (SC) for the 
PT6T-3 turboshaft engine, SC No. 33-23-EA-6 issued on June 8, 1970, and 
amended those SC on July 16, 1970 to clarify the vibration test 
requirements of engine furnished components for the aircraft rotor 
drive system. The PT6T-9 turboshaft engine model will have 30-second, 
2-minute, and continuous one-engine inoperative (OEI) ratings. These 
OEI ratings will apply to a one power-section inoperative condition. 
The Special Conditions issued for the PT6T-3 turboshaft engine 
addressed, among other items, the 30-minute OEI power rating, but not 
the 30-second, 2-minute, and continuous OEI ratings. The 30-second, and 
2-minute OEI power ratings were added to the airworthiness 
certification standards for aircraft engines, 14 CFR part 33, in 1996. 
Those new ratings were added to part 33 to enhance rotorcraft safety 
after an engine failure or precautionary engine shutdown by providing 
the availability of higher OEI power. The continuous OEI rating has 
been part of part 33 since 1988 and for the PT6T-9 engine will allow 
for the continuous operation of the remaining operative power-section 
at a higher power setting in the event one power-section fails.

[[Page 81730]]

    The FAA has determined to issue these SC without prior notice and 
opportunity for comment. The ratings added to the PWC PT6T-9 engine 
model are substantially similar to ratings added to the PT6T-3 through 
SC 33-23-EA-6, as amended, and ratings added to part 33 since the 
original certification of the PT6T-3. An opportunity to comment on 
these ratings was previously available as part of those previous 
actions. These SC are required now because as a derivative to the PT6T-
3 engine model the PT6T-9 engine will carry a certification basis that 
pre-dates the amendments to the aircraft engine certification standards 
that added these new ratings to part 33. Accordingly, these SC are 
issued to include the new ratings for the PWC PT6T-9 turboshaft engine 
model.
    As part of these SC, the FAA will require PWC to perform two 
endurance tests on the PT6T-9 turboshaft engine model which are thermal 
endurance and mechanical endurance. The engine power-section thermal 
endurance test will be conducted to the power, speed, and temperature 
limitations as required by Sec. 33.87(a), (d) and (f), as amended 
through Amendment 18 of part 33. The mechanical endurance test defined 
in the special conditions will be conducted to substantiate the PT6T-9 
turboshaft engine model power train to the requested output speed and 
torque limitations. Lastly, teardown inspection requirements are added 
to all tests wherever applicable.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, PWC must show either that 
the PT6T-9 turboshaft engine model meets the requirements of the 
applicable regulations in effect on the date of the application, or 
meets the applicable provisions of the regulations incorporated by 
reference in Type Certificate No. E22EA. The regulations incorporated 
by reference in the type certificate are commonly referred to as the 
``original type certificate basis.'' The regulations incorporated by 
reference in Type Certificate No. E22EA are part 33, dated February 1, 
1965, including Amendments 33-1 through 33-4.
    The Administrator finds that the applicable airworthiness 
regulations in part 33, as amended, and the original type certification 
basis, do not contain adequate or appropriate safety standards for the 
PT6T-9 turboshaft engine model. Special conditions, as appropriate, are 
issued in accordance with Sec. 11.38 after public notice, unless the 
FAA determines that notice would delay the delivery of the affected 
product or that notice has previously been afforded on a substantially 
identical proposal. Special conditions become part of the type 
certification basis of a product in accordance with 14 CFR 
21.101(b)(2).

Novel or Unusual Design Features

    The Pratt & Whitney engine model PT6T-9 turboshaft engine model 
incorporates two power-sections coupled to a common gearbox, and will 
have engine ratings for 30-second OEI, 2-minute OEI, and continuous OEI 
operations when one power-section is inoperative. The requirements of 
the original type certification basis do not provide adequate or 
appropriate safety standards for these novel and unusual design 
features. Therefore, these special conditions are intended to establish 
a level of safety equivalent to the existing airworthiness standards. 
These special conditions provide additional safety standards for the 
PWC PT6T-9 turboshaft engine model in the following areas:
    a. Endurance test.
    b. Clutch engagement.
    c. Overspeed test.
    d. Maximum torque test.
    e. Oil Flow interruption.
    f. Power section isolation.
    g. Critical component reliability.

Applicability

    These special conditions are applicable to the PWC PT6T-9 series 
turboshaft engine. Should PWC apply at a later date for an amended type 
certificate to add additional engine models to TC E22EA that are 
substantially similar to the PT6T-9 series engine and that have the 
same novel and unusual design features, these special conditions would 
apply to those models as well under the provisions of 14 CFR 
21.101(a)(1), and be included in the type certification basis for those 
additional models.

Conclusion

    This action affects only certain novel and unusual design features 
on one model of engines. 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 engine.

List of Subjects in 14 CFR Part 33

    Air Transportation, Aircraft, Aviation Safety, Safety.
    The authority citations for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.

The Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for the PWC PT6T-9 turboshaft engine model.
    (a) Definitions: Unless otherwise approved by the Administrator and 
documented in the appropriate manuals and certification documents, for 
the purpose of these special conditions the following definitions apply 
to the PT6T-9 turboshaft engine model.
    (1) One power-section (OPS): One of two free turbine turbomachines 
mounted to a combining gearbox of a turboshaft engine. The PWC PT6T-9 
turboshaft engine model consists of two free turbine turbomachines 
coupled to a combining gearbox.
    (2) OPS One Engine Inoperative (OEI) power: The rated engine power 
for operation with one power-section inoperative.
    (b) Mechanical test: In addition to the requirements of Sec. 33.87, 
the following mechanical test must be conducted: This test will 
substantiate the speed and torque limitations for the PT6T-9 turboshaft 
engine model drive train, from the power turbine rotor through the 
gearbox, to the engine output shaft. In place of the operating time 
cycles specified in Sec. 33.87(a)(d) and (f), the engine must be 
subject to a mechanical endurance test as prescribed in paragraphs 
(b)(1) through (b)(8) of this section. This must include at least 232 
hours and 20 minutes of operation, consisting of 20 cycles of 11 hours 
and 37 minutes each as follows:
    (1) Takeoff and ideling: One hour of alternate 5 minute periods of 
takeoff torque, and 5 minutes at the lowest and most practicable engine 
idle speed. Output shaft speed must be maintained at rated rpm 
throughout. In complying with this paragraph, the power level must be 
moved from one extreme position to the other in no more than one 
second. Immediately following every 5-minute power-on-run, simulate a 
failure for each power section by applying the maximum torque and the 
maximum speed for use with 30-second OPS OEI power to the remaining 
reduction gearbox (RGB) power input for no less than 30 seconds. Each 
application of 30-second OPS OEI power must be followed by two 
applications of the maximum torque and the maximum speed for use with 
the 2-minute OPS OEI power for no less than 2 minutes each. The second 
application must follow a period at stabilized continuous OPS OEI 
power. At least one run sequence must be conducted from a simulated 
``flight idle'' condition.
    (2) Rated maximum continuous: three hours at rated maximum 
continuous

[[Page 81731]]

torque must be conducted at maximum continuous speed.
    (3) 90 percent rate maximum continuous: One hour at 90 percent rate 
maximum continuous torque must be conducted at maximum speed for use 
without maximum continuous torque.
    (4) 80 percent rated maximum continuous: One hour at 80 percent 
rated maximum continuous torque must be conducted at minimum speed for 
use with maximum continuous torque.
    (5) 60 percent rated maximum continuous: One hour at 60 percent 
rated maximum continuous torque must be conducted at minimum speed for 
use with maximum continuous torque.
    (6) Engine malfunctioning run: It must be determined if a 
malfunction of engine components, such as the engine fuel or torque 
limiters, or if unequal power section power can cause dynamic 
conditions detrimental to the common gearbox parts and clutches. If a 
detrimental condition(s) exists, a suitable number of hours of 
operation must be accomplished under those conditions, 1 hour of which 
must be included in each cycle, and the remaining time must be 
accomplished at the end of the 20 cycles. If no detrimental condition 
results, an additional hour of operation must be conducted in 
compliance with paragraph (b)(1) excluding the OPS OEI power portions.
    (7) Overspeed run: One hour of continuous operation at 110 percent 
of rated maximum continuous output speed must be conducted at maximum 
continuous torque. If the power sections are limited to an overspeed of 
less than 110 percent of maximum continuous speed, the speed used must 
be the highest speed allowable for those power sections.
    (8) Continuous OPS OEI power runs: In sequence, and for each power 
section of the engine, a power section must be inoperative while the 
remaining power section is run for 1 hour and 14 minutes. The power 
section that is running must use continuous OPS OEI torque at maximum 
speed. The teardown inspection after completing the mechanical 
endurance test must comply with the requirements of Sec. 33.93(a).
    (c) Clutch engagements. In addition to the requirements of 
Sec. 33.91, a minimum of 400 clutch engagements, including the 
engagements of paragraph (b)(1) of these special conditions must be 
made during the takeoff power runs. If it is necessary, engagements 
should be made at each change of power and speed throughout the test. 
In each engagement, the shaft on the driven side of the clutch must be 
accelerated from rest or an unloaded condition that is representative 
of engine operation. This test may be conducted concurrently with the 
mechanical endurance test. The teardown inspection after completing the 
clutch engagement test must comply with the requirements of 
Sec. 33.93(a).
    (d) Overspeed test. The endurance test of paragraph (b) of these 
special conditions must be completed before performing this test under 
the requirements of Sec. 33.89, and without intervening major 
disassembly. The output gearbox must be subjected to 50 overspeed runs, 
each 30  3 seconds in duration at 120 percent of rated 
maximum continuous speed. These runs must be conducted as follows:
    (1) Overspeed runs must be alternated with stabilizing runs of 60 
to 80 percent of maximum continuous speed.
    (2) Acceleration and deceleration must be accomplished in a period 
not longer than 10 seconds, and the time for changing speeds may not be 
deducted from the specified time for the overspeed runs. If the power 
section are limited by the applicant to an overspeed of less than 120 
percent of maximum continuous speed for the periods required, the 
highest allowable speed must be used for the power sections involved. 
The teardown inspection after completing the overspeed test mut comply 
with the requirements of Sec. 33.93(a).
    (e) Maximum torque test. When performing the requirements of 
Sec. 33.89 for maximum torque operation, the maximum power section 
output of the engine must be substantiated as follows:
    (1) Under conditions associated with all power sections operating, 
perform 200 applications, for 10 seconds each, of torque that is, at a 
minimum, equal to the lesser of (i) and (ii):
    (i) The maximum torque used in meeting the endurance test plus 10 
percent or;
    (ii) The maximum torque attainable under probable operating 
conditions, assuming that torque limiting devices, if any, function 
properly.
    (2) With the critical power sections inoperative, apply the maximum 
torque attainable under probable operating conditions, assuming that 
torque limiting devices, if any, function properly. Each gearbox input 
must be tested at this maximum torque for at least 15 minutes. The 
teardown inspection after completing the maximum torque test must 
comply with the requirements of Sec. 33.93.
    (f) Oil flow interruption. In addition to the requirements of 
Sec. 33.71, the mixing gearbox must be operated at zero oil pressure 
and 100 percent output speed for at least 5 minutes without seizure.
    (g) Power section isolation. The power sections and their systems, 
including fuel, oil and control systems, must be arranged and isolated 
from each other to allow operation, in at least one configuration. 
Consequently, the failure or malfunction of any power section, or the 
failure of any system that can affect any power section, will not 
prevent the continued safe operation of the remaining power section. 
For the purpose of these special conditions, a power section failure is 
interpreted to not include an uncontained failure, such as an 
uncontained power section rotor burst.
    (h) Critical component reliability. In addition to the vibration 
tests specified in Sec. 33.83, the vibration load/stress limits of 
engine-furnished critical components of the rotor drive system must be 
investigated. This investigation must include the following: (1) The 
gearbox case and each component in the mixing gearbox whose failure 
would cause an uncontrolled landing.
    (2) Each component common to the two power sections.
    (3) Components provided as a part of the engine necessary to 
transmit power from the power section shaft to and through the engine 
output shaft. This includes components such as gearboxes, shafting, 
couplings, rotor brake assemblies, clutches, supporting bearings for 
shafting, and any attendant accessory pads or drives.

    Issued in Burlington, Massachusetts on December 8, 2000.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 00-32883 Filed 12-26-00; 8:45 am]
BILLING CODE 4910-13-M