[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]
BILLING CODE 4910-13-M