Airworthiness Directives; British Aerospace Model BAe 146 and Model Avro 146-RJ Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-129-AD; Amendment 39-11260; AD 99-17-12]

RIN 2120-AA64

Airworthiness Directives; British Aerospace Model BAe 146 and

Model Avro 146-RJ Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

applicable to certain British Aerospace Model BAe 146 and Model Avro

146-RJ series airplanes, that requires a one-time measurement to

determine the thickness of the outer links of the side stays of the

main landing gear (MLG), and corrective actions, if necessary. This

amendment also provides for replacement of a thin outer link with a new

or serviceable part in lieu of certain follow-on inspections. This

amendment is prompted by issuance of mandatory continuing airworthiness

information by a foreign civil airworthiness authority. The actions

specified by this AD are intended to prevent cracking of the outer

links of the side stays of the MLG, which could result in failure of a

side stay, and consequent collapse of the landing gear.

DATES: Effective September 27, 1999.

The incorporation by reference of certain publications listed in

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

of September 27, 1999.

ADDRESSES: The service information referenced in this AD may be

obtained from AI(R) American Support, Inc., 13850 Mclearen Road,

Herndon, Virginia 20171. 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: Norman B. Martenson, Manager,

International Branch, ANM-116, FAA, Transport Airplane Directorate,

1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425)

227-2110; fax (425) 227-1149.

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

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to certain British Aerospace Model

BAe 146 and Model Avro 146-RG series airplanes was published in the

Federal Register on September 8, 1998 (63 FR 47445). That action

proposed to require a one-time measurement to determine the thickness

of the outer links of the side stays of the main landing gear (MLG),

and corrective actions, if necessary. That action also proposed to

provide for replacement of a thin outer link with a new or serviceable

part in lieu of certain follow-on inspections.

Interested persons have been afforded an opportunity to participate

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

the comments received.

Request to Allow Flight With Cracks

One commenter, the manufacturer, requests that the proposal be

revised to allow flight with certain specified cracking limits. The

commenter points out that, although the inspection for cracking is

easily accomplished, the replacement of a cracked part is difficult

(necessitates acquisition of the replacement part and takes about 12

hours of elapsed time for the installation). The commenter states that

a side stay with a 1 millimeter (mm) crack in the outer links of the

side stays of the MLG was returned to the commenter, and was then

subjected to fatigue testing by applying 20,000 cycles of the test

spectra, where 1 cycle of test spectra was equivalent to 1 flight. The

crack grew to 30 mm in length. The side stay was then tested to 130

percent and finally to 165 percent of limit load without failure (i.e.,

in excess of ultimate load). The commenter notes that, based on those

fatigue testing results, the United Kingdom Civil Aviation Authority

(CAA) granted approval for continued revenue service with cracking

detected up to 19.05 mm, and required inspections to detect cracking at

intervals of 70 landings, up to a maximum of 500 landings.

The FAA concurs with the commenter's request in this case. Since

the outer link of the main landing gear side stay is readily

inspectable for cracking during the normal operation of the airplane,

the FAA has determined that cracking could be discovered at a remote

site, but that acquiring parts and accomplishing the repair would be

difficult. In addition, the FAA has determined that the commenter has

provided a conservative demonstration that the airplane can retain FAA-

certificated strength requirements for a limited period of time until

the cracked part is replaced. Therefore, continued flight of the

airplane may be permitted when cracking exists that is within the

limits described in the service bulletin, provided that visual

inspections for cracking and eventual replacement of the cracked part

are performed at the times specified in the final rule. The FAA has

revised paragraph (a)(2)(ii)(B) of the final rule and added a new

paragraph (a)(2)(ii)(C) to the final rule that reflect these changes.

Request to Revise the Unsafe Condition

This same commenter notes that while the proposal states that

cracking of the outer links of the side stays of the MLG could ``result

in increased braking distance during landing and consequent runway

overrun,'' the actual unsafe condition is that the cracking could

result in failure of the side stay, which would result in collapse of

the main landing gear.

The FAA infers that the commenter is requesting that the unsafe

condition be revised. The FAA acknowledges that, although the proposal

describes one possible unsafe outcome of a main landing gear collapse,

other unsafe outcomes are possible. The FAA concurs that, in this case,

the commenter's suggested revision is preferable to the proposal's

description in that it is a more precise statement of the actual

consequence of cracking of the outer links of the side stays of the

[[Page 45871]]

MLG. The FAA has revised the final rule to reflect the commenter's

suggestion.

In addition, the FAA has added a new ``Note 4'' to the final rule

to add a definition of the term ``detailed visual inspection.''

Conclusion

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 described

previously. The FAA has determined that these changes will neither

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

the AD.

Cost Impact

The FAA estimates that 37 Model BAe 146 and Model Avro 146-RJ

series airplanes of U.S. registry will be affected by this AD. It will

take approximately 1 work hour per airplane to accomplish the required

measurement, at an average labor rate of $60 per work hour. Required

parts will be supplied by the manufacturer at no cost to operators.

Based on this figure, the cost impact of the measurement required by

this AD on U.S. operators is estimated to be $2,220, or $60 per

airplane.

The cost impact figure discussed above is based on assumptions that

no operator has yet accomplished any of the requirements of this AD

action, and that no operator would accomplish those actions in the

future if this AD were not adopted.

Regulatory Impact

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 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:

99-17-12 British Aerospace Regional Aircraft (Formerly British

Aerospace Regional Aircraft Limited, Avro International Aerospace

Division; British Aerospace, PLC; British Aerospace Commercial

Aircraft Limited): Amendment 39-11260. Docket 97-NM-129-AD.

Applicability: Model BAe 146 and Model Avro 146-RJ series

airplanes, equipped with side stays of the main landing gear (MLG)

having part numbers (P/N) listed in Messier-Dowty Service Bulletin

146-32-128, dated December 6, 1996; certificated in any category.

Note 1: This AD applies to each airplane 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 airplanes that have been modified,

altered, or repaired so that the performance of the requirements of

this AD is affected, the owner/operator must request approval for an

alternative method of compliance in accordance with paragraph (c) of

this AD. The request should include an assessment of the effect of

the modification, alteration, or repair on the unsafe condition

addressed by this AD; and, if the unsafe condition has not been

eliminated, the request should include specific proposed actions to

address it.

Compliance: Required as indicated, unless accomplished

previously.

To prevent cracking of the outer links of the side stays of the

main landing gear (MLG), which could result in failure of a side

stay, and consequent collapse of the landing gear; accomplish the

following:

(a) Within 500 landings or 60 days after the effective date of

this AD, whichever occurs later, perform a one-time measurement to

determine the thickness of the outer links of the side stays of the

MLG, in accordance with British Aerospace Service Bulletin SB.32-

144, dated December 11, 1996.

Note 2: The British Aerospace service bulletin references

Messier-Dowty Service Bulletin 146-32-128, dated December 6, 1996,

as an additional source of service information for accomplishment of

the measurement.

(1) If the profile gauge does not slip over the top edge of the

outer link profile, no further action is required by this AD.

(2) If the profile gauge slips over the top edge of the outer

link profile, prior to further flight, accomplish either paragraph

(a)(2)(i) or (a)(2)(ii) of this AD.

(i) Replace the outer link with a new or serviceable part in

accordance with the service bulletin. After replacement of the outer

link, no further action is required by this AD.

Note 3: For purposes of this AD, a ``serviceable'' outer link is

defined as an outer link that is not cracked and on which a profile

gauge does not slip over the top edge of the profile, as described

in the service bulletin.

(ii) Perform a detailed visual inspection to detect cracking of

the outer links of the side stays of the MLG, in accordance with the

service bulletin.

Note 4: For the purposes of this AD, a detailed visual

inspection is defined as: ``As intensive visual examination of a

specific structural area, system, installation, or assembly to

detect damage, failure, or irregularity. Available lighting is

normally supplemented with a direct source of good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc., may be used. Surface cleaning

and elaborate access procedures may be required.''

(A) If no cracking is detected, repeat the detailed visual

inspection thereafter at intervals not to exceed 4,000 landings.

(B) If any cracking of only one flange of an outer link is

detected, and the cracking is within the limits specified by the

service bulletin: Repeat the detailed visual inspection at intervals

not to exceed 70 landings, and replace the cracked outer link with a

new or serviceable part in accordance with the service bulletin

within 500 landings after the cracking is detected. After

replacement of the outer link, no further action is required by this

AD.

(C) If any cracking of more than one flange of an outer link is

detected, or if any cracking is detected that is outside the limits

specified by the service bulletin: Prior to further flight, replace

the cracked outer link with a new or serviceable part in accordance

with the service bulletin. After replacement of the outer link, no

further action is required by this AD.

(b) As of the effective date of this AD, no person shall install

on any airplane a side stay of the MLG having a part number listed

in paragraph 1.A. of Messier-Dowty Service Bulletin 146-32-128,

dated December 6, 1996; unless the profile gauge does not slip over

the profile of the outer links of the side stay, as described in

British Aerospace Service Bulletin SB.32-144, dated December 11,

1996.

[[Page 45872]]

Alternative Methods of Compliance

(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, International Branch, ANM-116, 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, International

Branch, ANM-116.

Note 5: Information concerning the existence of approved

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

obtained from the International Branch, ANM-116.

Special Flight Permits

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

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

CFR 21.197 and 21.199) to operate the airplane to a location where

the requirements of this AD can be accomplished.

Incorporation by Reference

(e) The actions shall be done in accordance with British

Aerospace Service Bulletin SB.32-144, dated December 11, 1996. 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 AI(R) American Support , Inc., 13850

Mclearen Road, Herndon, Virginia 20171. 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.

Note 6: The subject of this AD is addressed in British

airworthiness directive 005-12-96.

(f) This amendment becomes effective on September 27, 1999.

Issued in Renton, Washington, on August 10, 1999.

D.L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-21364 Filed 8-20-99; 8:45 am]

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