Airworthiness Directives; British Aerospace Model ATP Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-98-AD; Amendment 39-8872; AD 94-08-01]

Airworthiness Directives; British Aerospace Model ATP Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to all British Aerospace Model ATP airplanes, that requires

revising the Airplane Flight Manual (AFM) to prohibit flight in certain

freezing precipitation conditions. This AD also provides an optional

terminating action for the AFM revision. This amendment is prompted by

reports of engine power rollback (loss of engine power) that occurred

in environmental conditions involving freezing precipitation. The

actions specified by this AD are intended to prevent loss of multiple

engine power during flight in freezing precipitation.

DATES: Effective June 15, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of June 15, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Jetstream Aircraft, Inc., P.O. Box

16029, Dulles International Airport, Washington, DC 20041-6029. This

information may be examined at the Federal Aviation Administration

(FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue,

SW., Renton, Washington; or at the Office of the Federal Register, 800

North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: William Schroeder, Aerospace Engineer,

Standardization Branch, ANM-113, FAA, Transport Airplane Directorate,

1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206)

227-2148; fax (206) 227-1320.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to all British Aerospace Model ATP airplanes was published

in the Federal Register on September 3, 1993 (58 FR 46916). That action

proposed to require revising the Airplane Flight Manual (AFM) to

prohibit flight in certain freezing precipitation conditions.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the proposed rule, but suggests that the

action should have been issued to require immediate compliance to

reduce the traveling public's exposure to the potential risk of loss of

multiple engine power during flight in freezing precipitation and

possible unplanned landings. The commenter also requests that, since

the AD was issued as a proposal, the time required for publication of

the final rule in the Federal Register be kept to a minimum so as not

to induce an additional administrative delay that would only delay

compliance.

The FAA does not concur with the commenter's suggestion that the

final rule be issued to require immediate compliance. At the time of

issuance of the proposal, the FAA could not justify that an immediate

safety of flight problem existed, especially in light of the fact that

the single operator of the entire U.S. fleet of Model ATP airplanes

already had added an operating restriction similar to that required by

this AD to its FAA-approved operation specifications and had agreed to

operate in accordance with that restriction until further corrective

action could be identified and incorporated. Moreover, the operating

limitation was proposed by the FAA since, at that time, the airplane

manufacturer, the Civil Aviation Authority (CAA), which is the

airworthiness authority for the United Kingdom, and the FAA were

uncertain as to the cause of the engine power rollback problem

described in the preamble to the proposal. However, considerable

information was available at that time to indicate that the problem was

due to ice ingestion into the engines during certain meteorological

conditions. That data, however, had not yet been confirmed through

testing conducted by the manufacturer and the CAA. Consequently, the

FAA determined that a requirement to prohibit flight in certain

freezing precipitation conditions would provide an acceptable level of

safety until terminating action could be identified and developed.

In developing this AD action, the FAA considered all of these

items, and determined that, since the continued operational safety of

the U.S. fleet could be assured during the interim, it was not

impracticable to provide notice and the opportunity for public comment

on the proposed rule.

Two commenters, the CAA and Jetstream, request that the proposed

rule be revised to require establishing a life limit on the engine

igniter plugs, installing a bypass duct outlet eductor, and

incorporating other changes to the airplane flight manual (AFM), in

lieu of the proposed AFM revision. The commenters contend that, if such

interim measures are taken, an acceptable level of safety would be

assured pending longer term corrective action. The commenters explain

that service information has been issued that describes procedures for

those actions, as follows:

1. Jetstream Service Bulletin ATP-80-06, Revision 1, dated October

22, 1993, which describes procedures for placing a life limit on the

engine igniter plugs and replacing those parts at staggered periods in

order to improve ignition reliability.

2. Jetstream Service Bulletin ATP-54-12-35274A, Revision 1, dated

December 15, 1993, which describes procedures for installation of an

eductor plate over the exhaust port of the engine air intake system.

Accomplishment of this installation will increase the air flow rate

down the exhaust port.

3. Temporary Revision No. T/33, Issue 1, dated November 1, 1993,

which revises AFM Document No. ATP 004. This temporary revision

describes revisions to the Limitations and Normal Procedures sections

of the FAA-approved AFM to introduce procedures for operation in icing

conditions. The changes include a ground inspection of the engine inlet

prior to flight, staggered selection of the left- and right-hand engine

de-ice systems to ensure that the likelihood of simultaneous engine

rundown on final approach is minimized, and a small increase in the

final approach speed to ensure safe landing.

Jetstream also suggests two other alternatives that would provide

an adequate level of safety, wherein the proposed AFM limitation could

be removed:

1. Modification of the engine inlets, in addition to accomplishment

of the interim measures discussed previously (a life limit on the

engine igniter plugs, installation of a bypass duct outlet eductor, and

certain changes to the AFM). Jetstream indicates that these modified

engine inlets demonstrate a significant improvement in de-icing

effectiveness in the range of temperatures and airplane speeds in which

power rollbacks have been experienced.

Jetstream service bulletins that relate to the engine inlet

modification are described as follows: Jetstream Service Bulletin ATP-

54-13-35274B, dated October 9, 1993, describes procedures for

installing engine air inlet ducts that incorporate electrical de-ice

heaters with increased power and area. The service bulletin also

describes procedures for performing associated electrical system

changes. The installation involves installing engine air inlet ducts

that incorporate an enlarged heater mat with revised electrical power

densities adjacent to the engine intake flange. Jetstream Service

Bulletin ATP-54-14, dated October 14, 1993, describes procedures for

repetitive visual inspections of the heater mats for damage, and

replacement of the engine air intake, if necessary.

2. Accomplishment of special operating procedures, not specifically

defined by the commenter. Jetstream considers that requiring such

operating procedures is a proven and acceptable means of providing an

adequate level of safety, as generally demonstrated by the operation of

aircraft throughout their flight spectra, in accordance with AFM's.

Jetstream submits one final suggestion in the event the FAA

proceeds with requiring the proposed operating limitation. In this

case, the commenter suggests that the actions described in Jetstream

Service Bulletins ATP-54-13-35274B and ATP-54-14, in addition to the

interim measures discussed previously (a life limit on the engine

igniter plugs, installation of a bypass duct outlet eductor, and

certain changes to the AFM), be accomplished as an alternative method

of compliance for the proposed operating limitation.

The FAA concurs partially. The interim measures proposed by the CAA

and Jetstream were based, to a large extent, on the flight crew

performing special operating procedures to ensure a safe landing after

one or both engines had run down due to ice ingestion. However, the FAA

considers that requiring the flight crew to perform such special

operating procedures over a long term period may not provide the degree

of safety assurance necessary for these airplanes. The FAA has

determined that requiring the proposed operating limitation to prohibit

flight into certain meteorological conditions known to cause engine

rundown will provide an acceptable level of safety until additional

hardware modifications can be identified and installed on these

airplanes.

However, the FAA concurs with Jetstream's suggestion that the

accomplishment of the interim measures and modification of the engine

inlets may be accomplished as optional terminating action for the

operating limitation. Since the issuance of the proposed rule,

Jetstream has issued Temporary Revision No. T/38, Issue 1, dated

February 16, 1994, which revises certain pages of Temporary Revision

No. T/33 (discussed previously). Temporary Revision No. T/38 amends the

Normal Procedures section of the AFM as related to operation of engine

continuous ignition during flight in icing conditions. The FAA finds

that this new information must be included in the AFM for Model ATP

airplanes in order to assure continued reliability and to prevent

unnecessary wear on engine ignition systems.

Accordingly, the final rule has been revised to include a new

paragraph (b), which includes the following optional terminating

action:

1. Revising the Limitations section and the Normal and Abnormal

Procedures sections of the FAA-approved AFM, to include the information

specified in Temporary Revision No. T/33, Issue 1, dated November 1,

1993, and Temporary Revision No. T/38, Issue 1, dated February 16,

1994, to introduce procedures for operation in icing conditions.

2. Revising the FAA-approved maintenance program to place a life

limit on the engine igniter plugs and to replace those parts at

specified intervals in accordance with Jetstream Service Bulletin ATP-

80-06, Revision 1, dated October 22, 1993.

3. Installing an eductor plate over the exhaust port of the engine

air intake system in accordance with Jetstream Service Bulletin ATP-54-

12-35274A, Revision 1, dated December 15, 1993.

4. Installing engine air inlet ducts that incorporate electrical

de-ice heaters with increased power and area, and performing associated

electrical system changes, in accordance with Jetstream Service

Bulletin ATP-54-13-35274B, dated October 9, 1993.

5. Revising the FAA-approved maintenance program to include

repetitive visual inspections of the heater mats for damage; and, if

any damage is found, replacement of the engine air intake; in

accordance with Jetstream Service Bulletin ATP-54-14, dated October 14,

1993. -

This is considered to be interim action until final action is

identified, at which time the FAA may consider further rulemaking.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

The FAA estimates that 9 airplanes of U.S. registry will be

affected by this AD, that it will take approximately 1 work hour per

airplane to accomplish the required AFM revision, and that the average

labor rate is $55 per work hour. The cost for required parts is

expected to be negligible. Based on these figures, the total cost

impact of the AD on U.S. operators is estimated to be $495, or $55 per

airplane. This total cost figure assumes that no operator has yet

accomplished the requirements of this AD.

Should an operator elect to accomplish the optional terminating

action that is provided by this AD action, the number of work hours

required to accomplish it is approximately 159 per airplane, at an

average labor rate of $55 per work hour. Required modification parts

would be supplied by Jetstream at no cost to operators. Based on these

figures, the total cost impact of the AD for accomplishment of the

optional terminating action is $8,745 per airplane.

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.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it 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, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 14 CFR part

39 of the Federal Aviation Regulations 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:

94-08-01 British Aerospace (Commercial Aircraft), Limited:

Amendment 39-8872. Docket 93-NM-98-AD.

Applicability: All Model ATP airplanes, certificated in any

category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent loss of multiple engine power during flight in

freezing precipitation, accomplish the following:

(a) Within 30 days after the effective date of this AD, revise

the Limitations Section 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.

``Flight is prohibited into forecast or reported freezing

precipitation conditions where the outside air temperature is

between +5 deg.C and -5 deg.C.''

(b) Accomplishment of the actions specified in paragraphs

(b)(1), (b)(2), (b)(3), (b)(4), and (b)(5) constitutes terminating

action for the AFM revision required by paragraph (a) of this AD.

(1) Revise the Limitations section and the Normal Procedures

section of the FAA-approved AFM, to include the information

specified in Temporary Revision No. T/33, Issue 1, dated November 1,

1993, and Temporary Revision No. T/38, Issue 1, dated February 16,

1994, which introduce procedures for operation in icing conditions,

as specified in the temporary revision; and operate the airplane in

accordance with those limitations and procedures.

Note 1: This may be accomplished by inserting copies of

Temporary Revision No. T/33 and No. T/38 in the AFM. When these

temporary revisions have been incorporated into general revisions of

the AFM, the general revisions may be inserted in the AFM, provided

the information contained in the general revisions is identical to

that specified in Temporary Revision No. T/33 and No. T/38.

(2) Incorporate a revision into the FAA-approved maintenance

program that provides for replacement of engine igniter plugs at the

intervals specified in Jetstream Service Bulletin ATP-80-06,

Revision 1, dated October 22, 1993. Initial replacement of an engine

igniter plug with a new plug shall be accomplished prior to the

accumulation of 200 total hours time-in-service on the engine

igniter plug, or within 50 hours time-in-service after incorporating

the maintenance program revision, whichever occurs later. -

(3) Install an eductor plate over the exhaust port of the engine

air intake system in accordance with Jetstream Service Bulletin ATP-

54-12-35274A, dated September 28, 1993, or Revision 1, dated

December 15, 1993. Any eductor plate installed in accordance with

the original issue of the service bulletin must be inspected for any

aperture profile mismatch, in accordance with paragraph 2., Part B.,

of the Accomplishment Instructions of Revision 1 of the service

bulletin. If any mismatch is found that exceeds the limit specified

in that service bulletin, prior to further flight, the discrepancy

must be corrected in accordance with paragraph 2., Part C, of

Revision 1 of the service bulletin.

(4) Install engine air inlet ducts that incorporate electrical

de-ice heaters with increased power and area, and perform associated

electrical system changes, in accordance with Jetstream Service

Bulletin ATP-54-13-35274B, dated October 9, 1993.

(5) Revise the FAA-approved maintenance program to include

repetitive visual inspections of the heater mats for damage at

intervals not to exceed 50 hours time-in-service, in accordance with

Jetstream Service Bulletin ATP-54-14, dated October 14, 1993; and,

if any damage is found, prior to further flight, replace the engine

air intake, in accordance with the service bulletin.

(c) 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, Standardization Branch, ANM-113,

FAA, Transport Airplane Directorate. Operators shall submit their

requests through an appropriate FAA Principal Maintenance Inspector,

who may add comments and then send it to the Manager,

Standardization Branch, ANM-113.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Standardization Branch, ANM-113.

(d) Special flight permits may be issued in accordance with

Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the

airplane to a location where the requirements of this AD can be

accomplished.

(e) The actions shall be done in accordance with the following

documents, as applicable, which contain the specified effective

pages:

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Service bulletin

referenced and Page No. Revision level shown Date shown on page

date----- on page-

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Temporary Revision 1-5 1.................... November 1, 1993.

No. T/33; Issue

1, November 1,

1993.

Temporary Revision 1-2, 7-8 1.................... February 16, 1994.

No. T/38; Issue 3-4 (These pages are

1, February 16, 5-6 removed). March 5, 1993.

1994. Original

ATP 80-06; 1-3 1.................... October 22, 1993.

Revision 1,

October 22, 1993.

ATP-54-13-35274B, 1-44- Original............. October 9, 1993.

October 9, 1993.

ATP-54-14, October 1-5 Original............. October 14, 1993.

14, 1993.

ATP-54-12-35274A, 1-3, 5, 7 Original............. September 28,

September 28, 4, 6 (These pages are not 1993.

1993. used)

ATP-54-12-35274A; 1-5, 7, 9 1.................... December 15, 1993.

Revision 1, 6, 8 (These pages are not

December 15, 1993. used)

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This incorporation by reference was approved by the Director of

the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR

part 51. Copies may be obtained from Jetstream Aircraft, Inc., P.O.

Box 16029, Dulles International Airport, Washington, DC 20041-6029.

Copies may be inspected at the FAA, Transport Airplane Directorate,

1601 Lind Avenue, SW., Renton, Washington; or at the Office of the

Federal Register, 800 North Capitol Street, NW., suite 700,

Washington, DC.

(f) This amendment becomes effective on June 15, 1994.

Issued in Renton, Washington, on March 31, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-8177 Filed 5-13-94; 8:45 am]

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