[Federal Register Volume 61, Number 114 (Wednesday, June 12, 1996)]
[Proposed Rules]
[Pages 29697-29699]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-14866]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-ANE-09]
RIN 2120-AA64
Airworthiness Directives; Rolls-Royce plc RB211-535E4 and -535E4-
B Series Turbofan Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This document proposes the adoption of a new airworthiness
directive (AD) that is applicable to Rolls-Royce plc RB211-535E4 and -
535E4-B series turbofan engines. This proposal would require
installation of an improved fuel flow governor that incorporates
revised minimum compressor discharge P4 stop settings. This proposal is
prompted by reports of engine rundowns during low idle descent during
icing conditions. The actions specified by the proposed AD are intended
to prevent compressor stall and subsequent engine rundown on one or
both engines.
DATES: Comments must be received by August 12, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), New England Region, Office of the Assistant Chief
Counsel, Attention: Rules Docket No. 96-ANE-09, 12 New England
Executive Park, Burlington, MA 01803-5299. Comments may also be
submitted to the Rules Docket by using the following Internet address:
``[email protected]''. Comments may be inspected at this
location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except
Federal holidays.
The service information referenced in the proposed rule may be
obtained from Rolls-Royce plc, P.O. Box 31, Moor Lane, Derby, DE248BJ,
United Kingdom; telephone 1332-249428, fax 1332-249423. This
information may be examined at the FAA, New England Region, Office of
the Assistant Chief Counsel, 12 New England Executive Park, Burlington,
MA.
FOR FURTHER INFORMATION CONTACT: Daniel Kerman, Aerospace Engineer,
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (617)
238-7130, fax (617) 238-7199.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed rule 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 above. All
communications received on or before the closing date for comments,
specified above, will be considered before taking action on the
proposed rule. The proposals 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 rule. All
comments submitted will be available, both before and after the closing
date for comments, in the Rules Docket for examination by interested
persons. A report summarizing each FAA-public contact concerned with
the substance of this proposal will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 96-ANE-09.'' The postcard will be date stamped and
returned to the commenter.
Availability of NPRMs
Any person may obtain a copy of this NPRM by submitting a request
to the FAA, New England Region, Office of the Assistant Chief Counsel,
Attention: Rules Docket No. 96-ANE-09, 12 New England Executive Park,
Burlington, MA 01803-5299.
[[Page 29698]]
Discussion
The Civil Aviation Authority (CAA), which is the airworthiness
authority for the United Kingdom, recently notified the Federal
Aviation Administration (FAA) that an unsafe condition may exist on
Rolls-Royce plc (R-R) RB211-535 series turbofan engines. The CAA
advises that they have reports of seven engine rundown events on the R-
R RB211-535E4 and -535E4-B engines installed on Boeing 757-200 series
aircraft since January 1992. All of the events occurred within a narrow
band of altitude between 25,000 and 29,000 feet. In four of the seven
events, the second engine installed on the aircraft surged and
recovered. In six of the seven events, the engine rundowns occurred
approximately 3 to 5 seconds following selection of inlet cowl anti-ice
during the descent phase of flight. Selection of cowl inlet anti-ice
results in an engine acceleration from low idle to high idle thrust,
which can cause liberation of accreted ice within the engine core. In
one event, the rundown occurred following an auto-throttle initiated
acceleration.
Rolls-Royce plc has performed extensive analysis and testing and
has concluded that the engine rundown is due to the following: (1) Ice
accretion at the inlet to the Intermediate Pressure Compressor (IPC)
induces a rotating compressor stall during descent, which leads to a
High Pressure Compressor (HPC) surge on acceleration; and (2) Ice
accretion at the inlet to the IPC during descent is released into the
core engine, which in turn causes an HPC surge. This condition, if not
corrected, could result in compressor stall and subsequent engine
rundown on one or both engines.
The manufacturer has determined that the proposed solution for
preventing engine rundown is to raise the minimum compressor discharge
P4 stop setting in the fuel flow governor (FFG), which will increase
the low idle schedule above the engine idle conditions experienced
during all of the prior engine rundown events. This schedule increase
will result in a substantial increase in IPC stall margin, a moderate
increase in HPC stall margin, as well as provide the additional benefit
of increased ice accretion tolerance due to increased compressor
airflow.
Rolls-Royce plc has issued Mandatory (SB) No. RB.211-73-B869,
Revision 1, dated May 24, 1996, that specifies installation of an
improved FFG, which incorporates an increased minimum compressor
discharge pressure P4 stop setting, which will result in increased
engine idle speeds.
The FAA Transport Airplane Directorate issued AD 96-04- 11,
Amendment 39-9523, (61 FR 6935, February 23, 1996) applicable to Boeing
757-200 series airplanes equipped with R-R Model RB211-535E4 and -
535E4-B engines, that requires revision of the limitations section of
the FAA-approved Airplane Flight Manual (AFM) to require the flight
crew to activate engine inlet cowl thermal anti-ice systems on both
engines prior to descent. Installation of the improved FFG on both
engines for each aircraft would constitute terminating action to the
AFM revision requirements of AD 96- 04-11.
This engine model is manufactured in the United Kingdom and is type
certificated for operation in the United States under the provisions of
Section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and
the applicable bilateral airworthiness agreement. Pursuant to this
bilateral airworthiness agreement, the CAA has kept the FAA informed of
the situation described above. The FAA has examined the findings of the
CAA, reviewed all available information, and determined that AD action
is necessary for products of this type design that are certificated for
operation in the United States.
Since an unsafe condition has been identified that is likely to
exist or develop on other engines of the same type design registered in
the United States, the proposed AD would require installation of
improved FFGs that incorporate revised minimum compressor discharge P4
stop settings. This revised setting will raise the steady state low
idle schedule above the idle conditions experienced during any of the
prior engine rundown events. This schedule increase will result in a
substantial increase in IPC stall margin, a moderate increase in HPC
stall margin, as well as provide the additional benefit of increased
ice accretion tolerance due to increased compressor airflow. This
proposed action must be accomplished at the next shop visit, or within
9 calendar months after the effective date of this AD, whichever occurs
first. The FAA has determined the calendar end-date based on the time
interval required for fleet modification. The actions would be required
to be accomplished in accordance with SB described previously.
There are approximately 770 engines of the affected design in the
worldwide fleet. The FAA estimates that 381 engines installed on
aircraft of U.S. registry would be affected by this proposed AD, that
it would take approximately 3 work hours per engine to accomplish the
proposed actions, and that the average labor rate is $60 per work hour.
The affected FFGs would be modified to incorporate the changes required
by this proposed AD on a free-of-charge basis per engine. Based on
these figures, the total cost impact of the proposed AD on U.S.
operators is estimated to be $68,580.
The regulations proposed herein would not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);
and (3) if promulgated, will not have a significant economic impact,
positive or negative, on a substantial number of small entities under
the criteria of the Regulatory Flexibility Act. A copy of the draft
regulatory evaluation prepared for this action is contained in the
Rules Docket. A copy of it may be obtained by contacting the Rules
Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend
part 39 of the Federal Aviation Regulations (14 CFR part 39) as
follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Rolls-Royce plc: Docket No. 96-ANE-09.
Applicability: Rolls-Royce plc. (R-R) Models RB211- 535E4 and -
535E4-B turbofan engines installed on Boeing 757- 200 series
aircraft.
[[Page 29699]]
Note: This airworthiness directive (AD) applies to each engine
identified in the preceding applicability provision, regardless of
whether it has been modified, altered, or repaired in the area
subject to the requirements of this AD. For engines that have been
modified, altered, or repaired so that the performance of the
requirements of this AD is affected, the owner/operator must use the
authority provided in paragraph (d) to request approval from the
Federal Aviation Administration (FAA). This approval may address
either no action, if the current configuration eliminates the unsafe
condition, or different actions necessary to address the unsafe
condition described in this AD. Such a request should include an
assessment of the effect of the changed configuration on the unsafe
condition addressed by this AD. In no case does the presence of any
modification, alteration, or repair remove any engine from the
applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent compressor stall and subsequent engine rundown on one
or both engines, accomplish the following:
(a) At the next shop visit, but no later than 9 calendar months
after the effective date of this AD, install a fuel flow governor
(FFG) that incorporates a revised minimum compressor discharge P4
stop setting, in accordance with R-R Mandatory Service Bulletin (SB)
No. RB.211-73-B869, Revision 1, dated May 24, 1996.
(b) Installation of improved FFG's on both engines for each
Boeing 757 aircraft in accordance with paragraph (a) of this AD
constitutes terminating action to the requirements of AD 96-04-11.
(c) For the purpose of this AD, a shop visit is defined as
removal of the engine from the aircraft for maintenance.
(d) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Engine Certification Office. The
request should be forwarded through an appropriate FAA Principal
Maintenance Inspector, who may add comments and then send it to the
Manager, Engine Certification Office.
Note: Information concerning the existence of approved
alternative methods of compliance with this airworthiness directive,
if any, may be obtained from the Engine Certification Office.
Issued in Burlington, Massachusetts, on May 22, 1996.
Robert E. Guyotte,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 96-14866 Filed 6-11-96; 8:45 am]
BILLING CODE 4910-13-U