Airworthiness Directives; Boeing Model 757 Equipped With Pratt & Whitney Model PW2000 Series Engines

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.

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Appendix 1

[GRAPHIC][TIFF OMITTED]TR05JA95.001

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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]

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