Airworthiness directives: McDonnell Douglas,

 
CONTENT

[Federal Register: December 22, 1999 (Volume 64, Number 245)]

[Proposed Rules]

[Page 71689-71694]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr22de99-33]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-338-AD]

RIN 2120-AA64

Airworthiness Directives; McDonnell Douglas Model DC-8 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

SUMMARY: This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-8 series airplanes, that currently requires a revision to the Airplane Flight Manual Supplement to ensure that the main deck cargo door is closed, latched, and locked; repetitive inspections of the wire bundle and door latch rollers to detect damage; and repair or replacement of damaged components. This action would require, among other actions, modification of the indication and hydraulic systems of the main deck cargo door, and installation of a means to prevent pressurization to an unsafe level if the main deck cargo door is not closed, latched, and locked. This proposal is prompted by the FAA's determination that certain main deck cargo door systems do not provide an adequate level of safety; the latching and locking mechanisms are not of adequate design to prevent structural deformation in the event of component jamming; and that there is an absence of a means to prevent pressurization to an unsafe level if the main deck cargo door is not closed, latched, and locked. The actions specified by the proposed AD are intended to prevent opening of the cargo door while the airplane is in flight, and consequent rapid decompression of the airplane including possible loss of the door, flight control, or severe structural damage.

DATES: Comments must be received by February 7, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-338-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 National Aircraft Service, Inc. (NASI), 9133 Tecumseh- Clinton Road, Tecumseh, MI 49286. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California.

FOR FURTHER INFORMATION CONTACT: Michael E. O'Neil, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood,

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California 90712-4137; telephone (562) 627-5320; fax (562) 627-5210.

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 filedin 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 99-NM-338-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-114, Attention: Rules Docket No. 99-NM-338-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On October 8, 1993, the FAA issued AD 93-20-02, amendment 39-8709 (58 FR 53635, October 18, 1993), applicable to certain McDonnell Douglas Model DC-8 series airplanes equipped with a cargo conversion modification installed in accordance with Supplemental Type Certificate (STC) SA1802SO or SA421NW. That AD requires a revision to the FAA- approved Airplane Flight Manual Supplement (AFMS) to include detailed procedures for use of the cargo door warning light system; repetitive inspections of the cargo door warning system wiring and door latching roller mechanism to detect damage; and repair or replacement of damaged components. That action was prompted by the FAA's review of data indicating that disabling of certain circuit breakers may deprive the flight crew of necessary information. The requirements of that AD are intended to prevent loss of the cargo door, damage to flight control surfaces, and reduced controllability of the airplane.

Actions Since Issuance of Previous Rule

Since issuance of that AD, the FAA has conducted a design review of McDonnell Douglas Model DC-8 series airplanes modified in accordance with STC SA1802SO [originally issued to Rosembalm and currently held by National Aircraft Services, Inc. (NASI)] and has identified several potential unsafe conditions. [Results of this design review are contained in ``DC-8 Cargo Modification Review Team Review of Rosenbalm Supplemental Type Certificate SA1802SO-Installation of a Cargo Door and Interior, Final Report, Revision A, dated November 29, 1999,'' hereinafter referred to as ``the Design Review Report,'' which is included in the Rules Docket for this NPRM.] The modification defined by STC SA421NW (held by NASI) is nearly identical to that defined by SA1802SO; therefore, SA421NW has the same potential unsafe conditions. STC SA1802SO and SA421NW specify a design for installation of a main deck cargo door, associated door cutout in the fuselage, door system hydraulics, door indication system, and Class ``E'' cargo interior with a cargo barrier on McDonnell Douglas Model DC-8 series airplanes.

This NPRM proposes corrective action for those potential unsafe conditions that relate to the hydraulic and indication systems of the main deck cargo door and provides for a means to prevent pressurization to an unsafe level if the main deck cargo door is not closed, latched, and locked. These conditions, if not corrected, could result in opening of the cargo door while the airplane is in flight, and consequent rapid decompression of the airplane including possible loss of the door, flight control, or severe structural damage.

Other Related Rulemaking

The FAA is considering further rulemaking to address the remaining potential unsafe conditions relating to the unreinforced main deck floor, main deck cargo door hinge, and fuselage structure in the area modified by installation of a main deck cargo door, 9g crash barrier, and fire/smoke detection system.

Main Deck Cargo Door Systems

In early 1989, two transport airplane accidents were attributed to cargo doors coming open during flight. The first accident involved a Boeing Model 747 series airplane in which the cargo door separated from the airplane, and damaged the fuselage structure, engines, and passenger cabin. The second accident involved a McDonnell Douglas DC-9 series airplane in which the cargo door opened but did not separate from its hinge. The open door disturbed the airflow over the empennage, which resulted in loss of flight control and consequent loss of the airplane. Although cargo doors have opened occasionally without mishap shortly after the airplane was in flight, these two accidents served to highlight the extreme potential dangers associated with the opening of a cargo door while the airplane is in flight.

As a result of these cargo door opening accidents, the Air Transport Association (ATA) of America formed a task force, including representatives of the FAA, to review the design, manufacture, maintenance, and operation of airplanes fitted with outward opening cargo doors, and to make recommendations to prevent inadvertent cargo door openings while the airplane is in flight. A design working group was tasked with reviewing 14 CFR part 25.783 [and its accompanying Advisory Circular (AC) 25.783-1, dated December 10, 1986] with the intent of clarifying its contents and recommending revisions to enhance future cargo door designs. This design group also was tasked with providing specific recommendations regarding design criteria to be applied to existing outward opening cargo doors to ensure that inadvertent openings would not occur in the current transport category fleet of airplanes.

The ATA task force made its recommendations in the ``ATA Cargo Door Task Force Final Report,'' dated May 15, 1991 (hereinafter referred to as ``the ATA Final Report''). On March 20, 1992, the FAA issued a memorandum to the Director-Airworthiness and Technical Standards of ATA (hereinafter referred to as ``the FAA Memorandum''), acknowledging ATA's recommendations and providing additional guidance for purposes of assessing the continuing airworthiness of existing designs of outward opening doors. The FAA Memorandum was not intended to upgrade the certification basis of the various airplanes, but rather to identify criteria to evaluate potential unsafe conditions identified on in- service airplanes. Appendix 1 of this AD

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contains the specific paragraphs from the FAA Memorandum that set forth the criteria to which the outward opening doors should be shown to comply.

Using the applicable requirements of Civil Air Regulations (CAR) part 4b and the design criteria provided by the FAA Memorandum, the FAA has reviewed the original type design of major transport airplanes, including McDonnell Douglas Model DC-8 airplanes equipped with outward opening doors, for any design deficiency or service difficulty. Based on that review, the FAA identified unsafe conditions and issued, among others, the following AD's:

‹bullet› For certain McDonnell Douglas Model DC-9 series airplanes: AD 89-11-02 R1, amendment 39-6415 (54 FR 50489, December 7, 1989);

‹bullet› For all Boeing Model 747 series airplanes: AD 90-09-06, amendment 39-6581 (55 FR 15217, April 23, 1990);

‹bullet› For certain McDonnell Douglas Model DC-8 series airplanes: AD 89-17-01 R1, amendment 39-6521 (55 FR 8446, March 8, 1990);

‹bullet› For certain Boeing Model 747-100 and -200 series airplanes: AD 96-01-51, amendment 39-9492 (61 FR 1703, January 23, 1996); and

‹bullet› For certain Boeing Model 727-100 and -200 series airplanes: AD 96-16-08, amendment 39-9708 (61 FR 41733, August 12, 1996).

In late 1997, the FAA informed the STC holders and operators of Model DC-8 series airplanes that it was embarking on a review of Model DC-8 series airplanes that have been converted from a passenger to a cargo-carrying (``freighter'') configuration by STC. The FAA proposed, at an industry sponsored meeting in early 1998, that DC-8 operators and STC holders work together to identify and address potential safety concerns. This suggestion to the affected industry resulted in the creation of the DC-8 Cargo Conversion Joint Task Force (JTF) (hereinafter referred to as ``the JTF'').

The current composition of the JTF includes holders of each of the five STC's that addresses the installation of a main deck cargo door in Model DC-8 series airplanes and operators and lessors of those modified airplanes. At the JTF's request, the FAA participates in its meetings to offer counsel and guidance with respect to the FAA's regulatory processes. The JTF is a clearinghouse for the gathering and sharing of information among the parties affected by the FAA review of STC cargo conversions of Model DC-8 series airplanes. The JTF also is a liaison between the FAA, operators, and STC holders.

The JTF has been working with the FAA to provide data relating to the number of STC modified Model DC-8 series airplanes and operators of those airplanes, and to identify which airplanes are modified by each STC. It also has been instrumental in polling the operators and providing maintenance schedules and locations to the FAA, which helped the FAA arrange visits to operators of airplanes modified by each of the STC's. These visits allowed the FAA to review both the available data supporting each STC and modified airplanes and to identify potential safety concerns with each of the STC modifications. Additionally, the JTF has been coordinating the funding of the industry review of the data supporting the STC's and ongoing efforts to resolve safety issues identified by the FAA.

Using the criteria specified in the ATA Final Report and the FAA Memorandum as evaluation guides, the FAA, in collaboration with the JTF, conducted an engineering design review and inspection of an airplane modified in accordance with STC SA1802SO. The FAA identified a number of design features of the main deck cargo door systems of this STC that are unsafe and do not meet the criteria specified in the ATA Final Report and the FAA Memorandum. These systems include the door indication and hydraulic systems, and the lack of a means to prevent pressurization of the airplane to an unsafe level if the door is not fully closed, latched, and locked. The FAA design review team also determined that the design data of this STC did not include an adequate safety analysis of the main deck cargo door systems.

The FAA has received reports of a recent event in which a main deck cargo door came open during take-off. This event was attributed, in part, to improper indication to the flight crew that the main deck cargo door was closed, latched, and locked. Service experience indicates that opening of a cargo door while the airplane is in flight can be extremely hazardous in a variety of ways, including possible loss of flight control, severe structural damage, or rapid decompression of the airplane.

For airplanes modified in accordance with STC's SA1802SO or SA421NW, the FAA considers the following five specific design features of the main deck cargo door systems to be unsafe:

  1. Indication System

    The main deck cargo door indication system for STC's SA1802SO and SA421NW uses a warning light at the flight engineer's panel. This light indicates the door open or closed status but does not provide the status of the cargo door latch and lock positions. All three conditions (i.e., door closed, latched, and locked) must be monitored directly so that the door indication system cannot display either ``latched'' before the door is closed or ``locked'' before the door is latched. If a sequencing error caused the door to latch and lock without being fully closed, the subject indication system, as designed, would not alert the door operator or the flight engineer of this condition. As a result, the airplane could be dispatched with the main deck cargo door unsecured, which could lead to the cargo door opening while the airplane is in flight.

    The light on the flight engineer's panel is labeled ``CARGO DOOR WARNING'' and is displayed in red since it indicates an event that requires immediate pilot action.

    However, if the flight engineer is temporarily away from his station, a door unsafe warning indication could be missed by the pilots. Therefore, an indicator light must be located in front of and in plain view of both pilots since one of the pilot's stations is always occupied during flight operations.

  2. Means To Visually Inspect the Locking Mechanism

    The single view port of the main deck cargo door, installed in accordance with STC's SA1802SO and SA421NW monitors only one of the 12 locks of the main deck cargo door. Therefore, the single view port does not provide confirmation that all of the locks of the main deck cargo door are engaged properly in the latches.

  3. Means To Prevent Pressurization to an Unsafe Level

    McDonnell Douglas DC-8 series airplanes modified in accordance with STC SA1820SO or SA421NW have no means of preventing pressurization to an unsafe level in the event that the main deck cargo door is not closed, latched, and locked, which could precipitate a cargo door opening while the airplane is in flight.

  4. Powered Lock Systems

    Evaluation of the powered lock systems of the main deck cargo door for STC's SA1802SO and SA421NW indicates the potential for latent and/ or single point failures that could restore or continue power to the door controls, which could result in inadvertent door openings while the airplane is in flight. STC's SA1802SO and SA421NW utilize a nose gear squat switch to remove door control power (i.e., electrical and hydraulic). Latent failure of the squat

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    switch together with other latent and/or single point failures could precipitate inadvertent door openings.

    AD 93-20-02 requires, prior to takeoff, pulling the circuit breakers of the main deck cargo door labeled ``pump'' and ``valve'' to ensure power is removed from the main deck cargo door. This requirement is considered to be interim action. To minimize the potential for latent failure of a circuit breaker in conjunction with the squat switch, the FAA finds that, for the purposes of this proposed AD, these circuit breakers must be replaced with new parts.

    The design data for STC's SA1802SO and SA421NW do not include a systems safety analysis to show that an inadvertent opening of a cargo door is extremely improbable. The need for a system safety analysis is identified in the ATA Final Report and the FAA Memorandum.

  5. Lock Strength

    Analysis of the existing latching and locking mechanism of the main deck cargo door indicates that, because of the existing latching and locking hydraulic cylinders, the translating beam, lever, swivel arm brackets, lock pins, and swivel arms have inadequate strength to prevent structural deformation of these parts in the event of components jamming. Structural deformation of the locking mechanism could result in the door latches not being locked and erroneous indication to the flightcrew that the latches are locked properly.

    Explanation of Relevant Service Information

    The FAA has reviewed and approved NASI Service Bulletin SB-99-01, Revision A, dated October 15, 1999. The service bulletin describes procedures for modification of the mechanical and hydraulic systems of the main deck cargo door installed in accordance with STC SA1802SO or SA421NW. The modification provides new parts of adequate strength to prevent structural deformation of the latching and locking mechanism by reducing the force of the latching and locking hydraulic cylinders and increasing the structural strength of the locking components. The modification involves installing a new translating beam, lever, swivel arm brackets, lock pins, swivel arms, hydraulic cylinders, and hydraulic lines.

    Accomplishment of the actions specified in the service bulletin and the actions described below is intended to adequately address the identified unsafe conditions.

    Explanation of Requirements of Proposed Rule

    Since unsafe conditions have been identified that are likely to exist or develop on other products of this same type design, the proposed AD would supersede AD 93-20-02 to continue to require a revision to the FAA-approved AFMS to include detailed procedures for use of the cargo door warning light system; repetitive inspections of the cargo door warning system wiring and door latching roller mechanism to detect damage; and repair or replacement of damaged components.

    The proposed AD also would require, within 30 days after the effective date of this AD, unless previously accomplished within the last 18 months prior to the effective date of this AD, replacement of the circuit breakers of the main deck cargo door labeled ``pump'' and ``valve'' with new circuit breakers.

    The proposed AD also would require, within 18 months after the effective date of this AD, accomplishment of the actions specified in the service bulletin described previously.

    In addition, the proposed AD would require, within 18 months after the effective date of this AD, modification of the indication system of the main deck cargo door to indicate to the pilots whether the main deck cargo door is closed, latched, and locked; installation of a means to visually inspect the locking mechanism of the main deck cargo door; installation of a means to remove power to the door while the airplane is in flight; and installation of a means to prevent pressurization to an unsafe level if the main deck cargo door is not closed, latched, and locked. These actions would be required to be accomplished in accordance with a method approved by the Manager, Los AngelesAircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Installation of STC ST01116CH (held by NASI) is an approved means of compliance with the modification requirements described previously. Accomplishment of these actions and the procedures described in NASI Service Bulletin SB-99-01 would constitute terminating action for the requirements of AD 93-20-02 [paragraphs (a) and (b) of this proposed AD].

    Differences Between the AD and Relevant Service Information

    The referenced service bulletin recommends accomplishing the modification of the hydraulic systems of the main deck cargo door within 180 days from July 1, 1999, not to exceed 270 calendar days from July 1, 1999. However, the FAA finds that accomplishing the following actions provides an acceptable level of safety until accomplishment of the modification:

    ‹bullet› Replacement of the circuit breakers of the main deck cargo door labeled``pump'' and ``valve'' with new circuit breakers;

    ‹bullet› An FAA-approved AFMS revision to include detailed procedures for use of the cargo door warning light system as specified in paragraph (b) of the proposed AD; and

    ‹bullet› Repetitive inspections of the cargo door warning system wiring and door latching roller mechanism to detect damage as specified in paragraph (a) of the proposed AD.

    Therefore, the FAA finds an 18-month compliance time for initiating the required modification to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

    Cost Impact

    There are approximately 32 Model DC-8 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 29 airplanes of U.S. registry would be affected by this proposed AD.

    The actions that are currently required by AD 93-20-02, and retained in this proposed AD, take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $1,740, or $60 per airplane, per inspection cycle.

    It would take 1 work hour per airplane to accomplish the new replacement of circuit breakers, at an average labor rate of $60 per work hour. Required parts would cost approximately $265 per airplane. Based on these figures, the cost impact of this new replacement proposed by this AD on U.S. operators is estimated to be $9,425, or $325 per airplane.

    It would take 80 work hours per airplane to accomplish the new modification of the hydraulic systems, at an average labor rate of $60 per work hour. Required parts would cost approximately $20,000 per airplane. Based on these figures, the cost impact of this new modification proposed by this AD on U.S. operators is estimated to be $719,200, or $24,800 per airplane.

    The FAA estimates that it would take approximately 130 work hours per airplane to accomplish the modification required by paragraph (d) of the

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    proposed AD, at an average labor rate of $60 per work hour. The FAA also estimates that required parts would cost approximately $25,000 per airplane. Based on these figures, the cost impact of this modification proposed by this AD on U.S. operators is estimated to be $951,200, or $32,800 per airplane.

    The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed 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 proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

    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 (44 FR 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

  6. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.

    Sec. 39.13 [Amended]

  7. Section 39.13 is amended by removing amendment 39-8709 (58 FR 53635, October 18, 1993), and by adding a new airworthiness directive (AD), to read as follows:

    McDonnell Douglas: Docket 99-NM-338-AD. Supersedes AD 93-20-02, Amendment 39-8709.

    Applicability: Model DC-8 series airplanes that have been converted from a passenger to a cargo-carrying (``freighter'') configuration in accordance with Supplemental Type Certificate (STC) SA1802SO or SA421NW; certificated in any category.

    Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (g) 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 opening of the cargo door while the airplane is in flight, and consequent rapid decompression of the airplane including possible loss of the door, flight control, or severe structural damage, accomplish the following:

    Restatement of Requirements of AD 93-20-02

    Actions Addressing the Main Deck Cargo Door

    (a) Within 7 days after January 21, 1992 (the effective date of AD 92-02-05, amendment 39-8141), and thereafter at intervals not to exceed 100 hours time-in-service, perform the following inspections:

    (1) Inspect the cargo door wire bundle between the exit point of the cargo liner and the attachment point on the cargo door to detect crimped, frayed, or chafed wires; and inspect for damaged, loose, or missing hardware mounting components. Prior to further flight, repair any damaged wiring or hardware mounting components in accordance with FAA-approved maintenance procedures.

    (2) Inspect the cargo door latch rollers in the lower sill of the cargo door opening of the airplane to ensure that all twelve rollers can be freely rotated by hand. Prior to further flight, replace any discrepant roller components found, and repair any rollers that cannot be rotated freely by hand, in accordance with FAA-approved maintenance procedures.

    (b) Within 7 days after November 17, 1993 (the effective date of AD 93-20-02, amendment 39-8709), revise the Limitations Section of the appropriate FAA-approved Airplane Flight Manual Supplement (AFMS) by replacing item 5 in the AFMS for SA1802SO, and item 6 in the AFMS for SA421NW, with the following. (This may be accomplished by inserting a copy of this AD into the AFMS.)

    ``Prior to initiating the cargo door closing sequence, a flight crew member must verify that the cargo door warning light is illuminated. After the door closing sequence is complete, and visual verification has been made that the latches are closed and the lockpins are properly engaged, a flight crew member must verify that the cargo door warning light is extinguished, and then conduct a PRESS-TO-TEST of the warning light to ensure that the light is operational. Pull the cargo door circuit breakers labeled ``pump'' and ``valve'' prior to takeoff. Methods for documentation of compliance with the preceding procedures must be approved by the FAA Principal Maintenance Inspector (PMI).''

    New Requirements of This AD

    Actions Addressing the Main Deck Cargo Door Powered Lock Systems

    (c) Except as provided by paragraph (f) of this AD, within 30 days after the effective date of this AD, unless previously accomplished within the last 18 months prior to the effective date of this AD, replace the circuit breakers of the main deck cargo door labeled ``pump'' and ``valve'' with new circuit breakers.

    Actions Addressing the Main Deck Cargo Door Hydraulic Systems

    (d) Within 18 months after the effective date of this AD, modify the mechanical and hydraulic systems of the main deck cargo door, in accordance with National Aircraft Services, Inc. (NASI) Service Bulletin SB-99-01, Revision A, dated October 15, 1999.

    Actions Addressing the Main Deck Cargo Door Indication System

    (e) Within 18 months after the effective date of this AD, modify the indication system of the main deck cargo door to indicate to the pilots whether the main deck cargo door is closed, latched, and locked; install a means to visually inspect the locking mechanism of the main deck cargo door; install a means to remove power to the door while the airplane is in flight; and install a means to prevent pressurization to an unsafe level if the main deck cargo door is not closed, latched, and locked; in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

    Note 2: Installation of NASI Vent Door System STC ST01116CH, is an approved means of compliance with the requirements of paragraph (e) of this AD.

    (f) Compliance with both paragraphs (d) and (e) of this AD constitutes terminating action for the requirements of both paragraphs (a) and (b) of this AD, and the AFMS revision required by paragraph (b) of this AD may be removed. Compliance with paragraph (e) of this AD within 30 days after the effective date of this AD eliminates the requirement to comply with paragraph (c) of this AD.

    Alternative Methods of Compliance

    (g) 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, Los

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    Angeles ACO. Operators shall submit their requests through an appropriate FAA PMI, who may add comments and then send it to the Manager, Los Angeles ACO.

    Note 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO.

    Special Flight Permits

    (h) 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.

    Appendix 1

    Excerpt from an FAA Memorandum to Director-Airworthiness and Technical Standards of ATA, dated March 20, 1992

    ``(1) Indication System:

    (a) The indication system must monitor the closed, latched, and locked positions, directly.

    (b) The indicator should be amber unless it concerns an outward opening door whose opening during takeoff could present an immediate hazard to the airplane. In that case the indicator must be red and located in plain view in front of the pilots. An aural warning is also advisable. A display on the master caution/warning system is also acceptable as an indicator. For the purpose of complying with this paragraph, an immediate hazard is defined as significant reduction in controllability, structural damage, or impact with other structures, engines, or controls.

    (c) Loss of indication or a false indication of a closed, latched, and locked condition must be improbable.

    (d) A warning indication must be provided at the door operators station that monitors the door latched and locked conditions directly, unless the operator has a visual indication that the door is fully closed and locked. For example, a vent door that monitors the door locks and can be seen from the operators station would meet this requirement.

    (2) Means to Visually Inspect the Locking Mechanism: There must be a visual means of directly inspecting the locks. Where all locks are tied to a common lock shaft, a means of inspecting the locks at each end may be sufficient to meet this requirement provided no failure condition in the lock shaft would go undetected when viewing the end locks. Viewing latches may be used as an alternate to viewing locks on some installations where there are other compensating features.

    (3) Means to Prevent Pressurization:

    All doors must have provisions to prevent initiation of pressurization of the airplane to an unsafe level, if the door is not fully closed, latched and locked.

    (4) Lock Strength:

    Locks must be designed to withstand the maximum output power of the actuators and maximum expected manual operating forces treated as a limit load. Under these conditions, the door must remain closed, latched and locked.

    (5) Power Availability:

    All power to the door must be removed in flight and it must not be possible for the flight crew to restore power to the door while in flight.

    (6) Powered Lock Systems:

    For doors that have powered lock systems, it must be shown by safety analysis that inadvertent opening of the door after it is fully closed, latched and locked, is extremely improbable.''

    Issued in Renton, Washington, on December 16, 1999. D.L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

    [FR Doc. 99-33171Filed12-21-99; 8:45 am]

    BILLING CODE 4910-13-U