[Federal Register Volume 59, Number 4 (Thursday, January 6, 1994)]
[Proposed Rules]
[Pages 706-707]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-249]
[[Page Unknown]]
[Federal Register: January 6, 1994]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 33
[Docket No. 93-ANE-67; Notice No. 33-ANE-06]
Special Conditions; Rolls-Royce Model(s) RB211-Trent-875-17/-877-
17/-884-17 Turbofan Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This notice proposes special conditions for the Rolls-Royce
Aircraft Engines Model(s) RB211-Trent-875-17/-877-17/-884-17 Turbofan
Engines. The applicable regulations do not contain adequate or
appropriate safety standards for the protection of these systems from
water and hail ingestion. This notice proposes 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).
DATES: Comments must be submitted on or before February 22, 1994.
ADDRESSES: Comments on this proposal may be submitted in triplicate to:
Federal Aviation Administration (FAA), New England Region, Office of
the Assistant Chief Counsel, Attn: Rules Docket No. 93-ANE-67, 12 New
England Executive Park, Burlington, Massachusetts 01803-5299. Comments
must be marked: Docket No. 93-ANE-67. Comments may be inspected at this
location between 8 a.m. and 4:30 p.m., Monday through Friday, except
Federal holidays.
FOR FURTHER INFORMATION CONTACT:
Thomas Boudreau, Engine and Propeller Standards Staff, ANE-110, Engine
and Propeller Directorate, Aircraft Certification Service, FAA, New
England Region, 12 New England Executive Park, Burlington,
Massachusetts 01803-5229; telephone (617) 238-7117; fax (617) 238-7199.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed special conditions by submitting such written data, views, or
arguments as they may desire. Communications should identify the Rules
Docket number and be submitted in triplicate to the address specified
under ADDRESSES. All communications received on or before the closing
date for comments, specified under DATES, will be considered by the
Administrator before taking action on the proposal. The proposal
contained in this notice may be changed in light of the comments
received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed special
conditions. All comments submitted will be available in the Rules
Docket for examination by interested persons, both before and after the
closing date for comments. A report summarizing each substantive public
contact with FAA personnel concerning this proposal will be filed in
the docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit with those comments a
self-addressed, stamped postcard on which the following statement is
made: ``Comments to Docket No. 93-ANE-67.'' The postcard will be date
stamped and returned to the commenter.
Background
On August 4, 1992, Rolls-Royce applied for type certification of
Model(s) RB211-Trent-870-17/-877-17/-884-17 turbofan engines. The
application for type certification of the Model RB211-Trent-870-17
turbofan engine was withdrawn and a new application for type
certification of the Model RB211-Trent-875-17 was made on April 6,
1993. The FAA has determined that the current water and hail ingestion
requirements of Sec. 33.77(c) of the FAR do not represent the inclement
weather threat encountered in service.
A study of in-service inclement weather events has indicated a need
to modify the water and hail ingestion requirements of this section to
ensure design integrity and demonstrate an adequate level of safety.
This study indicated that a potential flight safety threat existed for
engines when operating in severe weather environments. Although current
requirements provide adequate validation of the engine's resistance to
mechanical damage due to hail impact and case contractions from water
ingestion, the study showed that the current standards did not
adequately address engine power loss anomalies, such as rollback and
flameout at lower than take off rated power settings.
The FAA has concluded that additional safety standards must be
applied to Rolls-Royce Model(s) RB211-Trent-875-17/-877-17/-884-17
turbofan engines to demonstrate that they are capable of acceptable
operation in severe weather environments.
Type Certification Basis
Under the provisions of Sec. 21.101 of the FAR, Rolls-Royce must
show that Model(s) RB211-Trent-875-17/-877-17/-884-17 turbofan engines
meet the requirements of the applicable regulations in effect on the
date of the application. Those Federal Aviation Regulations are
Sec. 21.21 and Part 33, effective February 1, 1965, as amended through
August 10, 1990, Amendment 33-14.
The Administrator finds that the applicable airworthiness
regulations in part 33, as amended, do not contain adequate or
appropriate safety standards for Rolls-Royce Model(s) RB211-Trent-875-
17/-877-17/-884-17 turbofan engines because of unique design criteria.
Therefore, the Administrator proposes these special conditions under
the provisions 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 Sec. Sec. 11.28 and 11.29(b), and become part of the
type certification basis in accordance with Sec. 21.101(b)(2).
Conclusion
This action affects only Rolls-Royce Model(s) RB211-Trent-875-17/-
877-17/-884-17 turbofan engines. It is not a rule of general
applicability and affects only the manufacturer who applied to the FAA
for approval of these new design criteria on the engine.
List of Subjects in 14 CFR Part 33
Air transportation, Aircraft, Aviation safety, Safety.
The authority citation for these special conditions continues to
read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421, 1423; and 49 U.S.C.
106(g).
The Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for the Rolls-Royce Model(s) RB211-Trent-875-17/-877-17/-884-17
turbofan engines.
In addition to the requirements of FAR Sec. 33.77, the following
tests and analyses must be conducted, unless compliance can be shown by
alternate methods acceptable to the Administrator.
(a) The most critical operating point(s) for water and hail
ingestion must be determined by test, analysis, or other acceptable
methods, and must be based on the threat levels defined in Table 1 and
Table 2 of this proposal. The critical point(s) determination must
address the entire operating envelope of the engine. The critical
operating point(s) is defined as those operating conditions within the
engine flight envelope at which an engine operability margin is reduced
to a minimum level.
Table 1.--Rain Threat
------------------------------------------------------------------------
Liqud
water
content
(LWC)
Altitude (feet) (grams
water per
cubic
water
air)
------------------------------------------------------------------------
0............................................................ 20.0
20,000....................................................... 20.0
26,300....................................................... 15.2
32,700....................................................... 10.8
39,300....................................................... 7.7
46,000....................................................... 5.2
------------------------------------------------------------------------
Note: LWC and HWC values at other altitudes may be determined by linear
interpolation.
Table 2.--Hail Threat
------------------------------------------------------------------------
Hail
Water
Content
(HWC)
Altitude (feet) (grams
water per
cubic
meter
air)
------------------------------------------------------------------------
0............................................................ 8.9
7,300........................................................ 8.9
8,500........................................................ 9.4
10,000....................................................... 9.8
11,000....................................................... 9.9
12,000....................................................... 10.0
15,000....................................................... 10.0
16,000....................................................... 8.9
17,700....................................................... 7.8
19,300....................................................... 6.6
21,500....................................................... 5.6
24,300....................................................... 4.4
29,000....................................................... 3.3
46,000....................................................... 3.3
------------------------------------------------------------------------
Note: LWC and HWC values at other altitudes may be determined by linear
interpolation.
(b) The engine will be shown to operate at an acceptable level for
a minimum of three minutes when subjected to the critical point
conditions for water ingestion. The percentage of water to airflow by
weight, at the critical point, is to be reproduced during the engine
test. The test method should adequately model the inflight water
concentration effect at the primary flow (core) inlet. Water droplet
size and velocity distributions must be representative of the critical
water ingestion point. All variable systems, whose position could
effect engine operation during water ingestion, must be scheduled for
the most critical positions.
(c) The engine will be shown to operate at an acceptable level for
a minimum of 30 seconds when subjected to the critical point conditions
for hail ingestion. The percentage of hail to airflow by weight, at the
critical point, is to be reproduced during the engine test. The test
should adequately model the inflight hail concentration effect at the
primary flow (core) inlet. Hailstone size and velocity distributions
must be representative of the critical hail ingestion point. All
variable systems whose position could effect engine operation during
hail ingestion, must be scheduled for the most critical positions.
(d) Acceptable engine operation, as noted in paragraphs (b) and (c)
of this special condition, must preclude rundown, flameout, surge, loss
of acceleration capability, limit exceedance, or any other engine
anomaly which would negatively affect the operability of the engine.
(e) The engine, as operated under the conditions defined in
paragraphs (b) and (c) of this special condition, must show that it
will operate acceptably if exposed to other probable factors associated
with normal operations. These other probable factors include, but are
not limited to, performance losses, installation effects, inlet
distortion, and throttle transients.
Issued in Burlington, Massachusetts, on December 29, 1993.
Jay J. Pardee,
Acting Manager, Engine and propeller Directorate, Aircraft
Certification Service.
[FR Doc. 94-249 Filed 1-5-94; 8:45 am]
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