[Federal Register Volume 60, Number 89 (Tuesday, May 9, 1995)]
[Proposed Rules]
[Pages 24589-24592]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-11356]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-NM-107-AD]


Airworthiness Directives; British Aerospace Model ATP Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), which would have superseded an existing AD that is 
applicable to all British Aerospace Model ATP airplanes. The existing 
AD currently requires inspections to detect cracking of the aft end of 
the wing rib boom angles on the left and right engine, and repair or 
replacement of the wing rib boom angle assemblies, if necessary. The 
existing AD was prompted by the detection of cracks in the engine 
outboard rib boom angles at the main landing gear (MLG) actuator 
attachment point. Its required actions are intended to prevent 
structural failure of the actuator attachment point, which could lead 
to collapse of the MLG. The previously proposed action would have 
limited the applicability of the rule to certain airplanes; revised the 
initial inspection threshold for certain modified airplanes; and would 
have required that modified boom angles be installed whenever 
replacement is necessary. This action revises the proposed rule by 
correcting the actions necessary to be accomplished for one specific 
type of cracking condition.

DATES: Comments must be received by June 1, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-107-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule 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 FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington.

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.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 94-NM-107-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 94-NM-107-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
certain British Aerospace Model ATP airplanes, was published as a 
notice of proposed rulemaking (NPRM) in the Federal Register on January 
18, 1995 (60 FR 3581). That NPRM would have superseded an existing 
airworthiness directive (AD) that is applicable to all British 
Aerospace Model ATP series airplanes. The existing AD currently 
requires inspections to detect cracking of the aft end of the wing rib 
boom angles on the left and right engine, and repair or replacement of 
the wing rib boom angle assemblies, if necessary. The existing AD was 
prompted by the detection of cracks in the engine outboard rib boom 
angles at the main landing gear (MLG) actuator attachment point.
    The NPRM proposed to limit the applicability of the existing rule 
to only a certain number of airplanes; revise the initial inspection 
threshold, depending on whether or not certain modifications have been 
accomplished on the boom angles; and require that modified boom angles 
be installed whenever replacement is necessary.
    Since the issuance of that NPRM, the FAA has recognized that one of 
the corrective actions proposed for certain cracking indications was 
incorrectly stated.
    Specifically, proposed paragraph (f) describes the actions that are 
to be taken if visual inspections reveal that one rib boom angle is 
cracked, and the crack extends beyond bolt hole Y or into bolt hole A. 
For conditions of this type of cracking, the NPRM proposed to require 
that operators repeat the inspections of the rib boom angle for 
additional crack propagation at intervals of 50 hours time-in-service. 
If no additional cracking was detected during any of the repetitive 
inspections, operators would be required to repair the rib boom angle 
or replace the rib boom angle assembly within one month. However, if 
additional cracking was detected, operators would be required to repair 
or replace prior to further flight.
    Those proposed corrective actions were inadvertently iterated in 
the NPRM. They are incorrect and, as stated, are unacceptable as 
corrective action to address the described cracking conditions. 
Additionally, they are at variance with the corrective action 
recommended by the manufacturer and described in the service bulletin 
referenced in the NPRM as the appropriate source of service information 
(i.e., British Aerospace Service Bulletin ATP-57-13, Revision 5, dated 
June 3, 1994). Instead, the action that must be taken to address 
initial findings of the described cracking is either the repair of the 
wing boom angle or replacement of the wing boom angle assembly, prior 
to further flight. The FAA has determined that the proposed rule must 
be revised to require this specific corrective action.
    Since this change expands the scope of the originally proposed 
rule, the FAA has determined that it is necessary to reopen the comment 
period to provide additional opportunity for public comment.
    The FAA estimates that 10 airplanes of U.S. registry would be 
affected by this proposed AD. The inspections that are currently 
required by AD 93-14-08 take approximately 2 work hours per airplane to 
accomplish. The average labor rate is $60 per work hour. Based on these 
figures, the total cost impact of the current inspection requirements 
AD on U.S. operators is estimated to be $1,200, or $120 per airplane, 
per inspection cycle.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of 
[[Page 24591]] the proposed requirements of this AD action, and that no 
operator would accomplish those actions in the future if this AD were 
not adopted. However, since AD 93-14-08 became effective on September 
3, 1993, the FAA assumes that at least the initial inspection already 
has been performed on several of the affected airplanes. Thus, the 
total cost impact of this proposed AD may be reduced by the amount of 
the costs associated with those inspections that have already been 
accomplished.
    Additionally, since this proposed AD would extend the compliance 
time for the initial inspection of some airplanes, it has the effect of 
reducing the economic burden for operators of those airplanes, since it 
would preclude scheduling an airplane for inspections at a time earlier 
than is necessary.
    Should replacement of the boom angles with modified boom angles be 
necessary, it would require approximately 150 work hours to accomplish, 
at an average labor charge of $60 per work hour. Required parts would 
cost approximately $3,800 per airplane.
    The regulations proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44FR 11034, February 26, 1979); and 
(3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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 removing amendment 39-8632 (58 FR 
42194, August 9, 1993), and by adding a new airworthiness directive 
(AD), to read as follows:

British Aerospace: Docket 94-NM-107-AD. Supersedes AD 93-14-08, 
Amendment 39-8632.

    Applicability: Model ATP airplanes; serial numbers 2002 through 
2063, inclusive; 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 use the authority 
provided in paragraph (j) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition; or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent structural failure of the actuator attachment point, 
which could lead to collapse of the main landing gear (MLG), 
accomplish the following:
    (a) Conduct a detailed visual inspection to detect cracking of 
the aft end of the engine outboard rib boom angles under the wing 
rib outboard of the left and right engine, in accordance with 
British Aerospace Service Bulletin ATP-57-13, Revision1, dated 
January 15, 1993; or Revision 5, dated June 3, 1994; at the 
applicable time indicated below.
    (1) For airplanes on which Modification 10313A (reference 
British Aerospace Service Bulletin ATP-56-16-1013A, Revision 1, 
dated July 2, 1994) has not been accomplished: Conduct the initial 
inspection within 400 hours time-in-service after September 8, 1993 
(the effective date of AD 93-14-08, amendment 39-8632), or within 12 
months since airplane manufacture, whichever occurs later.
    (2) For airplanes on which Modification 10313A has been 
accomplished (modified inboard and outboard boom angles on both the 
left wing and right wing): Conduct the initial inspection prior to 
the accumulation of 30,000 landings on the boom angle assembly or 
within 12 months after the effective date of this AD, whichever 
occurs later.
    (b) For the purposes of compliance with this AD, the following 
apply:
    (1) Repair of cracked rib boom angles shall be accomplished in 
accordance with a method approved by the Manager, Standardization 
Branch, ANM-113, FAA, Transport Airplane Directorate.
    (2) Replacement of cracked rib boom angle assemblies with 
modified assemblies shall be accomplished in accordance with British 
Aerospace Service Bulletin ATP-57-16-10313A, Revision 1, dated July 
2, 1994 (as corrected by Erratum 2, dated August 30, 1994). Prior to 
the accumulation of 30,000 landings on the replaced (modified) boom 
angle assembly, repeat the inspection in accordance with paragraph 
(a) of this AD.
    (c) If no crack is detected: Repeat the detailed visual 
inspection at intervals not to exceed 3,000 landings or 12 months, 
whichever occurs first.
    (d) If any crack is detected on only one rib boom angle, and 
that crack does not extend beyond bolt hole X: Repeat the detailed 
visual inspection of the rib boom angle for additional crack 
propagation at intervals not to exceed 300 hours time-in-service.
    (1) If no additional crack propagation is detected during any of 
the repetitive inspections: Within 6 months after discovery of the 
crack, either repair the rib boom angle or replace the rib boom 
angle assembly in accordance with paragraph (b) of this AD.
    (2) If any of the repetitive inspections reveal that crack 
propagation has reached or extends beyond bolt hole Y or into bolt 
hole A: Prior to further flight, either repair the rib boom angle or 
replace the rib boom assembly in accordance with paragraph (b) of 
this AD.
    (e) If any crack is detected on only one rib boom angle, and 
that crack extends beyond bolt hole X, but not beyond bolt hole Y or 
down towards bolt hole A: Repeat the detailed visual inspection of 
the rib boom angle for additional crack propagation at intervals not 
to exceed 100 hours time-in-service.
    (1) If no additional crack propagation is detected during any of 
the repetitive inspections: Within 3 months after discovery of the 
crack, either repair the rib boom angle or replace the rib boom 
angle assembly in accordance paragraph (b) of this AD.
    (2) If any of the repetitive inspections reveal that crack 
propagation has reached or extends beyond bolt hole Y or into bolt 
hole A: Prior to further flight, either repair the rib boom angle or 
replace the rib boom angle assembly in accordance with paragraph (b) 
of this AD.
    (f) If any crack is detected on only one rib boom angle, and 
that crack extends beyond bolt hole Y or into bolt hole A: Prior to 
further flight, either repair the rib boom angle or replace the rib 
boom angle assembly in accordance with paragraph (b) of this AD.
    (g) If any crack is detected on both rib boom angles, and cracks 
do not extend beyond bolt hole X: Repeat the detailed visual 
inspection of the rib boom angles for additional crack propagation 
at intervals not to exceed 100 hours time-in-service. 
[[Page 24592]] 
    (1) If no additional crack propagation is detected during any of 
the repetitive inspections: Within 3 months after discovery of the 
cracks, either repair the rib boom angles or replace the rib boom 
angle assembly in accordance with paragraph (b) of this AD.
    (2) If any of the repetitive inspections reveal that crack 
propagation has reached or extends beyond bolt hole Y or into bolt 
hole A: Prior to further flight, either repair the rib boom angles 
or replace the rib boom angle assembly in accordance with paragraph 
(b) of this AD.
    (h) If any crack is detected on both rib boom angles, and cracks 
extend beyond bolt hole X, but not beyond bolt hole Y or down 
towards bolt hole A: Repeat the detailed visual inspection of the 
rib boom angles for additional crack propagation at intervals not to 
exceed 50 hours time-in-service.
    (1) If no additional crack propagation is detected during any of 
the repetitive inspections: Within 1 month after discovery of the 
cracks, either repair the rib boom angles or replace the rib boom 
angle assembly in accordance with paragraph (b) of this AD.
    (2) If any of the repetitive inspections reveal that crack 
propagation has reached or extends beyond bolt hole Y or into bolt 
hole A: Prior to further flight, either repair the rib boom angles 
or replace the rib boom angle assembly in accordance with paragraph 
(b) of this AD.
    (i) If any crack is detected on both rib boom angles, and cracks 
extend beyond bolt hole Y or into bolt hole A: Prior to further 
flight, either repair the rib boom angles or replace the rib boom 
angle assembly in accordance with paragraph (b) of this AD
    (j) 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.
    Note 3: Alternative methods of compliance previously granted for 
amendment 39-8632, AD 93-14-08, continue to be considered as 
acceptable alternative methods of compliance with this amendment.

    (k) 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.

    Issued in Renton, Washington, on May 3, 1995.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-11356 Filed 5-8-95; 8:45 am]
BILLING CODE 4910-13-U