# AD 95-01-05: Icing Conditions

- Type: Airworthiness directive
- Status: Current
- Products: Boeing 757-200 Series, 757-200CB Series, 757-200PF Series and 757-300 Series
- Effective: January 20, 1995
- Published: January 5, 1995, 60 FR 1712–1716
- Issued as: Final rule; request for comments
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Amendment: 39-9116
- Docket: 94-NM-231-AD
- Registered aircraft: 270 may be affected, by airframe or engine model (OpenAirDocs)
- Official PDF: https://openairdocs.org/files/sha256/ad/ab/adab4d4739eb60329bde2a448c126d65b13f737e9c05697f1385f8b9ff4e18f1 (from https://www.govinfo.gov/content/pkg/FR-1995-01-05/pdf/95-176.pdf)
- Federal Register: https://www.federalregister.gov/documents/1995/01/05/95-176/airworthiness-directives-boeing-model-757-equipped-with-pratt-and-whitney-model-pw2000-series
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/ECCFB58A2283B1FC86256976007012F0.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/95-01-05

## 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.

## The 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.

  (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 thefirst 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.

## Rule preamble

### 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 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 beconsidered, 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 bedate 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 Policiesand 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. § 39.13 - (Amended)

2. Section 39.13 is amended by adding the following new airworthiness directive:

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A2NM](https://openairdocs.org/tcds/A2NM): The Boeing Company; names 4 of 4 models: 757-200CB Series, 757-200PF Series, 757-300 Series, 757-200 Series

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 270 (270 by airframe model, 0 by engine model)
- Makers: Boeing 270

Models with the most aircraft:

- [Boeing 757-232](https://openairdocs.org/model/boeing-757-232): 63 aircraft (airframe model)
- [Boeing 757-224](https://openairdocs.org/model/boeing-757-224): 40 aircraft (airframe model)
- [Boeing 757-222](https://openairdocs.org/model/boeing-757-222): 38 aircraft (airframe model)
- [Boeing 757-223](https://openairdocs.org/model/boeing-757-223): 23 aircraft (airframe model)
- [Boeing 757-236](https://openairdocs.org/model/boeing-757-236): 20 aircraft (airframe model)
- [Boeing 757-251](https://openairdocs.org/model/boeing-757-251): 18 aircraft (airframe model)
- [Boeing 757-351](https://openairdocs.org/model/boeing-757-351): 16 aircraft (airframe model)
- [Boeing 757-231](https://openairdocs.org/model/boeing-757-231): 13 aircraft (airframe model)
- [Boeing 757-324](https://openairdocs.org/model/boeing-757-324): 9 aircraft (airframe model)
- [Boeing 757-200 SERIES](https://openairdocs.org/model/boeing-757-200-series): 7 aircraft (airframe model)
- [Boeing 757-204](https://openairdocs.org/model/boeing-757-204): 6 aircraft (airframe model)
- [Boeing 757-225](https://openairdocs.org/model/boeing-757-225): 5 aircraft (airframe model)
- [Boeing 757-230](https://openairdocs.org/model/boeing-757-230): 4 aircraft (airframe model)
- [Boeing 757-258](https://openairdocs.org/model/boeing-757-258): 3 aircraft (airframe model)
- [Boeing 757-256](https://openairdocs.org/model/boeing-757-256): 3 aircraft (airframe model)
- [Boeing 757-260PF](https://openairdocs.org/model/boeing-757-260pf): 2 aircraft (airframe model)

All 16 models: https://openairdocs.org/ad/95-01-05/models.md
Every aircraft: https://openairdocs.org/ad/95-01-05/aircraft.md

No proposed rule in this release led to it. Its text cites no advisory circulars or STCs.

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