[Federal Register Volume 60, Number 3 (Thursday, January 5, 1995)]
[Rules and Regulations]
[Pages 1712-1716]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-176]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-231-AD; Amendment 39-9116; AD 95-01-05]
Airworthiness Directives; Boeing Model 757 Equipped With Pratt &
Whitney Model PW2000 Series Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
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SUMMARY: This amendment adopts a new airworthiness directive (AD) that
is applicable to certain Boeing Model 757 series airplanes. This action
requires a revision to the FAA-approved Airplane Flight Manual to
include procedures to perform periodic engine run-ups during ground
operation in icing conditions in order to shed ice before it
accumulates, sheds, and is ingested into the engine, which could cause
damage to the core of the engine. This action provides procedures for a
visual check to detect ice build-up on the first stage of the low
pressure compressor (LPC) stator and removal of any ice, as necessary.
This amendment is prompted by reports of damage to the high pressure
compressor of the engines due to ice ingestion. The actions specified
in this AD are intended to prevent damage to engines due to the
ingestion of ice into the compressor, which can result in the loss of
power from the affected engine.
DATES: Effective January 20, 1995.
Comments for inclusion in the Rules Docket must be received on or
before March 6, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-231-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056.
Information concerning this amendment may be obtained from or
examined at the FAA, Transport Airplane Directorate, Rules Docket, 1601
Lind Avenue, SW., Renton, Washington 98055-4056.
FOR FURTHER INFORMATION CONTACT: Tamra J. Elkins, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2669; fax (206) 227-1181; or
John Fisher, Aerospace Engineer, Engine Certification Branch, ANE-141,
FAA, Engine and Propeller Directorate, Engine Certification Office, 12
New England Executive Park, Burlington, Massachusetts 01803; telephone
(617) 238-7149; fax (617) 238-7199.
SUPPLEMENTARY INFORMATION: Recently, the FAA has received reports of
damage to the high pressure compressor (HPC) of the engines on several
Boeing Model 757 series airplanes equipped with Pratt & Whitney Model
PW2000 series engines. Investigation into the cause of this damage
revealed that, during prolonged ground operation in icing conditions,
ice can accumulate on the first stage of the low pressure compressor
(LPC) stator. Subsequent acceleration to high thrust levels releases
this ice, which travels through the LPC and into the HPC, where blade
damage may occur.
During ground operation in icing conditions, ice may build up on
the first stage of the LPC stator of the engines. The engine anti-ice
system will not remove or prevent the formation of ice on this
component; it only protects the inlet cowl. Ice accumulation on the
first stage of the LPC stator is an urgent safety concern since it may
be ingested into the core of the compressor, which can cause damage to
the engine. If the ice accumulation is sufficiently large and is
subsequently shed and ingested, the resulting damage to the engine may
lead to surges in or loss of power from the affected engine.
The FAA has determined that periodic engine run-ups will shed the
ice from the first stage of the LPC stator before it accumulates in
sufficiently large quantities that, when shed, may result in damage to
the engine. Ice shedding occurs when the air loads exceed the adhesion
force between the ice and the stator. However, the quantity of ice that
is shed is not proportional to rotor speed. The FAA finds that a
minimum of 50 percent rotation speed of the engine fan (N1) is
necessary to shed ice; power settings below 50 percent N1 are
ineffective for ice removal. In addition, the FAA has determined that
these engine run-ups should be based on temperature and visible
moisture, rather than on icing indications on the airframe of the
airplane.
Ice accumulation, if not detected and removed, can be ingested into
the compressor and cause damage to the engine, which could result in
the loss of power from the affected engine.
Since an unsafe condition has been identified that is likely to
exist or develop on other airplanes of the same type design, this AD is
being issued to prevent damage to these engines due to ice ingestion
into the compressor, which may result in the loss of power from the
affected engine. This AD requires revising the Limitations Section of
the FAA-approved Airplane Flight Manual (AFM) to include procedures
that will ensure that during inclement weather, periodic engine run-ups
will shed ice before it accumulates and causes damage to the engine.
This action also provides procedures for a visual check to detect
ice build-up on the first stage of the LPC stator and removal of any
ice, if necessary. The FAA has determined that these visual checks may
be properly performed by pilots because the checks do not require the
use of tools, precision measuring equipment, training, pilot logbook
endorsements, or the use of or reference [[Page 1713]] to technical
data that are not contained in the body of the AD.
Since a situation exists that requires the immediate adoption of
this regulation, it is found that notice and opportunity for prior
public comment hereon are impracticable, and that good cause exists for
making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
this rule. Interested persons are invited to comment on this rule by
submitting such written data, views, or arguments as they may desire.
Communications shall identify the Rules Docket number and be submitted
in triplicate to the address specified under the caption ADDRESSES. All
communications received on or before the closing date for comments will
be considered, and this rule may be amended in light of the comments
received. Factual information that supports the commenter's ideas and
suggestions is extremely helpful in evaluating the effectiveness of the
AD action and determining whether additional rulemaking action would be
needed.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the rule that might
suggest a need to modify the 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 that
summarizes each FAA-public contact concerned with the substance of this
AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this rule must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 94-NM-231-AD.'' The postcard will be date stamped and
returned to the commenter.
The regulations adopted herein will 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 final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency
regulation that must be issued immediately to correct an unsafe
condition in aircraft, and that it is not a ``significant regulatory
action'' under Executive Order 12866. It has been determined further
that this action involves an emergency regulation under DOT Regulatory
Policies and Procedures (44 FR 11034, February 26, 1979). If it is
determined that this emergency regulation otherwise would be
significant under DOT Regulatory Policies and Procedures, a final
regulatory evaluation will be prepared and placed in the Rules Docket.
A copy of it, if filed, may be obtained from 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.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends 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. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
95-01-05 Boeing: Amendment 39-9116. Docket 94-NM-231-AD.
Applicability: Model 757 series airplanes equipped with Pratt &
Whitney Model PW2000 series engines, certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent damage to these engines due to ice ingestion into the
compressor, which may result in the loss of power from the affected
engine, accomplish the following:
(a) Within 14 days after the effective date of this AD, revise
the Limitations Section, Section 1, page 11, of the FAA-approved
Airplane Flight Manual (AFM) to include the following statement.
This may be accomplished by inserting a copy of this AD in the AFM.
Ground Operations During Icing Conditions
Periodic engine run-ups must be performed during prolonged
ground operation in icing conditions (including time to taxi-in and
taxi-out, and ground hold time), when engine anti-ice is required
and the outside air temperature (OAT) is +3 degrees Centigrade (37
degrees Fahrenheit) or less.
These momentary run-ups must be performed to a minimum of 50
percent N1 in order to shed ice from the first stage of the low
pressure compressor (LPC) stator. The run-up interval is established
according to either paragraph a. or paragraph b., below:
a. If a visual check of the leading edge of the first stage of
the LPC stator has NOT been accomplished prior to engine start, run-
ups must be performed at intervals not to exceed 15 minutes
(including time to taxi-in and taxi-out, and ground hold time); or
b. If a visual check of the leading edge of the first stage of
the LPC stator has been accomplished prior to engine start and it is
determined to be free of ice, run-ups must be performed at intervals
not to exceed 30 minutes (including time to taxi-in and taxi-out,
and ground hold time). Any ice accumulation on the first stage of
the LPC must be removed prior to dispatch.
In no case can the engines be operated for more than 30 minutes
without either a visual check or an engine run-up.
If either of the time limits in paragraph a. or paragraph b.,
above, is exceeded without performing a run-up, the aircraft must be
taxied to an area where the engines can be shut down, a visual check
for ice accumulation must be accomplished, and any ice must be
removed prior to the next run-up or takeoff. During taxi to the area
for the visual inspection, engine speeds greater than 40 percent
N1 should be avoided to minimize the potential for ice shedding
into the engine compressor. If these requirements cannot be met,
takeoff is not authorized.
The procedures for accomplishing the visual check of and ice
removal from the first stage of the LPC stator are contained in
paragraphs (b) and (c) of AD 95-01-05.
(b) Perform visual checks of the engine to detect ice build-up
on the first stage of the LPC stator in accordance with the
procedures specified in paragraphs (b)(1) and (b)(2) of this AD, at
the times specified in the revision to the AFM required by paragraph
(a) of this AD. These visual checks may be performed either by the
cockpit flight crew or by certificated maintenance personnel.
(1) Use adequate lighting to illuminate the first stage of the
LPC stator. This stator can be viewed by standing at ground level,
off to the side of the centerline of the engine, and viewing through
the opening between the fan blades. (See Appendix 1, Figure 1 of
this AD.) If ice is present, it will be seen to build up on the
leading edge of the first stage of the LPC stator or the lip of the
splitter. (See Appendix 1, Figure 2.)
(2) This visual check is to be performed after engine shutdown.
The visual check can be performed on a windmilling engine without
bringing the fan rotor to a stop. It will actually become easier to
see the first stage of the LPC stator if the rotor is turning. The
ice will be visible, if present.
(c) If any ice is detected on the first stage of the LPC stator
(see Appendix 1, Figure 2) during the visual check required by
paragraph (b) of this AD, it must be removed prior to dispatch of
the aircraft, in accordance with the procedures specified in
paragraph (c)(1) or (c)(2) of this AD, as applicable. [[Page 1714]]
(1) If the total ground operating time since the last run-up to
50 percent N1 is less than 30 minutes, the engine may be run-up
to 50 percent N1 to remove the ice, or it may be removed in
accordance with the ``Ice Removal'' procedures described in
paragraph (c)(2) of this AD.
(2) If the total ground operating time since the last run-up to
50 percent N1 is greater than 30 minutes, and the engine has
been visually checked and it has been determined that ice has
accumulated on the leading edge of the first stage of the LPC
stator, the following ``Ice Removal'' (hot air de-icing) method must
be used. Do not use hot water or aircraft de-icing fluids.
Ice Removal
De-ice the leading edge of the first stage of the LPC stator
with the use of a suitable hot air source (e.g., heating cart). At
no time should the temperature of the air supplied exceed 175
degrees Fahrenheit. Direct the air past the fan blades toward the
first stage of the LPC stator. Continue hot air de-icing this LPC
stator until all of the ice has been melted. Melted ice and ice
chunks, which have been dislodged, should not be allowed to
accumulate at the bottom of the fan duct where they could refreeze
and become ingested into the engine during the next engine run-up.
Note 1: The only acceptable means to remove ice from the first
stage of the LPC stator are listed in paragraphs (c)(1) and (c)(2)
of this AD.
(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, Seattle Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. Operators shall
submit their requests through an appropriate FAA Principal
Operations Inspector, who may add comments and then send it to the
Manager, Seattle ACO.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(e) This amendment becomes effective on January 20, 1995.
BILLING CODE 4910-13-U [[Page 1715]]
Appendix 1
[GRAPHIC][TIFF OMITTED]TR05JA95.001
BILLING CODE 4910-13-C [[Page 1716]]
Issued in Renton, Washington, on December 27, 1994.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-176 Filed 1-4-95; 8:45 am]
BILLING CODE 4910-13-U
