[Federal Register Volume 60, Number 201 (Wednesday, October 18, 1995)]
[Proposed Rules]
[Pages 53888-53890]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-25837]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-127-AD]


Airworthiness Directives; McDonnell Douglas Model DC-9-80 Series 
Airplanes and Model MD-88 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain McDonnell Douglas 
Model DC-9-80 series airplanes and Model MD-88 airplanes, that 
currently requires a revision to the FAA-approved Airplane Flight 
Manual (AFM) which specifies that autothrottles must be disconnected if 
engine surge (stall) is detected during takeoff. That AD was prompted 
by results of an accident investigation, which revealed that the 
digital flight guidance computer (DFGC) on these airplanes can 
incorrectly identify an engine surge or stall as being an engine 
failure. This can cause the autothrottles to unclamp and automatically 
advance the thrust levers during takeoff. The actions specified in that 
AD are intended to prevent automatic advance of the thrust lever on a 
surging engine during takeoff, which could cause engine failure. This 
action would require the installation of a modified DFGC's which, when 
accomplished, would terminate the requirement for the AFM revision.

DATES: Comments must be received by December 13, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-127-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 McDonnell Douglas Corporation, 3855 Lakewood Boulevard, 
Long Beach, California 90846, Attention: Technical Publications 
Business Administration, Department C1-L51 (2-60). 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: Robert Baitoo, Aerospace Engineer, 
Propulsion Branch, ANM-140L, FAA, Transport Airplane Directorate, Los 
Angeles Aircraft Certification Office, 3960 Paramount Boulevard, 
Lakewood, California; telephone (310) 627-5245; fax (310) 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 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 95-NM-127-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. 95-NM-127-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On April 23, 1992, the FAA issued AD 92-10-13, amendment 39-8247 
(57 FR 19249, May 5, 1992), applicable to all McDonnell Douglas Model 
DC-9-80 series airplanes and Model MD-88 airplanes. That AD requires a 
revision to the Limitations Section and the Procedures Section of the 
FAA-approved Airplane Flight Manual (AFM), which specifies that 
autothrottles must be disconnected if engine surge (stall) is detected 
during takeoff. That action was prompted by an

[[Page 53889]]

ongoing investigation following an accident involving a Model DC-9-80 
series airplane, which revealed that the digital flight guidance 
computer (DFGC) apparently can incorrectly identify an engine surge or 
stall as being an engine failure, and cause the autothrottles to 
unclamp and subsequently advance the thrust levers during takeoff. The 
requirements of that AD are intended to prevent automatic advance of 
the thrust lever on a surging engine during takeoff, which could cause 
engine failure.
    In the preamble of that AD, the FAA indicated that the requirements 
of that rule were considered interim action until final action is 
identified, at which time the FAA may consider further rulemaking. As a 
follow-on action from that determination, the FAA is now proposing to 
mandate a terminating action for the requirements of that rule.

Explanation of Service Information

    The FAA has reviewed and approved McDonnell Douglas Service 
Bulletin MD80-22-111, dated May 23, 1995, which describes procedures 
for modification of DFGC's having part number 4034241-971. The 
modification entails incorporation of several improvements to the 
flight software and corresponding hardware in the DFGC's. Once this 
modification is accomplished, the DFGC's are re-identified as ``part 
number 4034241-972.'' The subject DFGC's are located in the electrical/
electronics (E/E) compartment on the left and right radio racks. (The 
McDonnell Douglas service bulletin references Honeywell Service 
Bulletin 4034241-22-44, dated May 22, 1995, as an additional source of 
service information.)
    Additionally, for DFGC's having part numbers other than (lower 
than) part number 4034241-971, the McDonnell Douglas service bulletin 
references additional procedures that are necessary to be accomplished 
prior to installing the subject modification. These additional 
procedures are intended to bring those DFGC's to the level of 
configuration of DFGC's having part number 4034241-971. Once that level 
is reached, those DFGC's subsequently would be modified in accordance 
with the service bulletin and re-identified as part number 4034241-972.
    Modification of the DFGC's to the part number 4034241-972 
configuration will positively address the unsafe condition presented by 
a DFGC incorrectly identifying an engine surge or stall as being an 
engine failure. This condition could cause the autothrottles to unclamp 
and subsequently advance the thrust levers during takeoff, which could 
cause engine failure.

Explanation of the Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 92-10-13, but would continue to require 
a revision to the Limitations Section and Procedures Section of the 
FAA-approved AFM, which specifies that autothrottles must be 
disconnected if engine surge (stall) is detected during takeoff.
    The proposed AD also would require installation of modified DFGC's 
having part number 403241-972. Accomplishment of this installation 
would constitute terminating action for the currently required AFM 
revision. The installation would be required to be accomplished in 
accordance with the McDonnell Douglas service bulletin described 
previously.

Cost Impact

    There are approximately 1,117 Model DC-9-80 series airplanes and 
Model MD-88 airplanes of the affected design in the worldwide fleet. 
The FAA estimates that 643 airplanes of U.S. registry would be affected 
by this proposed AD.
    The AFM revision that is currently required by AD 92-10-13 takes 
approximately 1 work hour per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the total cost 
impact on U.S. operators of this current requirement is estimated to be 
$38,580, or $60 per airplane.
    The FAA estimates that the removal of DFGC's having part number 
4034241-971 and installation of DFGC's having part number 4034241-972 
would take approximately 1 work hour per airplane to accomplish, at an 
average labor rate of $60 per work hour. The required parts would cost 
approximately $2,000 (that is, $1,000 per DFGC, and 2 DFGC's per 
airplane). Based on these figures, the cost impact on U.S. operators of 
this proposed installation is estimated to be $1,324,580, or $2,060 per 
airplane.
    The total 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.
    Should an operator have an airplane equipped with DFGC's having 
part numbers other than (lower than) 4034241-971, additional actions 
may be required prior to accomplishing the installation proposed in 
this action. Those additional actions involve modification(s) of the 
DFGC's to bring them to the level of configuration of DFGC's having 
part number 4034241-971. Depending on the current configuration of the 
DFGC's installed on the airplane, the highest costs associated with 
modifying a DFGC to a part number 4034241-971 configuration (excluding 
subsequent modification to the part number 4034241-972 configuration) 
could be as much as $92,000 per airplane (that is $46,000 per DFGC, and 
2 DFGC's per airplane).
    The FAA recognizes that the obligation to maintain aircraft in an 
airworthy condition is vital, but sometimes expensive. Because AD's 
require specific actions to address specific unsafe conditions, they 
appear to impose costs that would not otherwise be borne by operators. 
However, because of the general obligation of operators to maintain 
aircraft in an airworthy condition, this appearance is deceptive. 
Attributing those costs solely to the issuance of this AD is 
unrealistic because, in the interest of maintaining safe aircraft, 
prudent operators would accomplish the required actions even if they 
were not required to do so by the AD.
    A full cost-benefit analysis has not been accomplished for this 
proposed AD. As a matter of law, in order to be airworthy, an aircraft 
must conform to its type design and be in a condition for safe 
operation. The type design is approved only after the FAA makes a 
determination that it complies with all applicable airworthiness 
requirements. In adopting and maintaining those requirements, the FAA 
has already made the determination that they establish a level of 
safety that is cost-beneficial. When the FAA, as in this proposed AD, 
makes a finding of an unsafe condition, this means that the original 
cost-beneficial level of safety is no longer being achieved and that 
the proposed actions are necessary to restore that level of safety. 
Because this level of safety has already been determined to be cost-
beneficial, a full cost-benefit analysis for this proposed AD would be 
redundant and unnecessary.

Regulatory Impact

    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 

[[Page 53890]]
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 (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

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

    Authority: 49 USC 106(g), 40101, 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-8247 (57 FR 
19249, May 5, 1992), and by adding a new airworthiness directive (AD), 
to read as follows:

McDonnell Douglas: Docket 95-NM-127-AD. Supersedes AD 92-10-13, 
Amendment 39-8247.

    Applicability: Model DC-9-80 series airplanes and Model MD-88 
airplanes equipped with digital flight guidance computers (DFGC) 
having part numbers other than 4034241-972; 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 use the authority 
provided in paragraph (d) of this AD 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 automatic thrust lever advance on a surging engine 
during takeoff, which could cause engine failure, accomplish the 
following:
    (a) Within 30 days after May 20, 1992 (the effective date of AD 
92-10-13, amendment 39-8247), 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.

``Limitations Section

    Autothrottles must be disconnected if engine surge (stall) is 
detected during takeoff.''
    (b) Within 30 days after May 20, 1992 (the effective date of AD 
92-10-13, amendment 39-8247), revise the Procedures Section of the 
FAA-approved AFM to include the following statement. This may be 
accomplished by inserting a copy of this AD in the AFM.

``Procedures Section

CAUTION

    During takeoff, the Digital Flight Guidance Computer (DFGC) 
engine failure logic is armed if (1) the flight director pitch axis 
is in takeoff mode, (2) the aircraft is above 400 feet radio 
altitude, and (3) both engine pressure ratios (EPR's) are below the 
go-around EPR limit. If the DFGC detects an EPR drop greater than or 
equal to 0.25 EPR and 7% N1 from the same engine, as compared to the 
other engine, the engine failure logic is satisfied and the DFGC 
will change the Thrust Rating Panel (or indicator) thrust limit to 
Go-Around (GA). This will cause the autothrottle system to unclamp 
and enter normal EPR limit (EPR LIM) mode where the throttles will 
maintain the higher engine EPR at the selected go-around thrust 
rating EPR LIM. Such an EPR and N1 drop may also result from an 
engine surge (stall). Advancing thrust levers on a surging engine 
will hinder surge recovery and may result in eventual engine 
failure.
    If an engine surge (stall) is detected during takeoff:
    (1) Disconnect autothrottles.
    (2) Reduce thrust on affected engine (idle if necessary).
    (3) Shut down the affected engine if surging and popping 
continues.
    (4) If affected engine surging or popping stops, accomplish the 
following:
    A. Place ignition switch to GRD START & CONTIN.
    B. Place ENG anti-ice switches to ON.
    C. Place PNEU X-FEED VALVE lever OPEN on affected side.
    D. Place AIR FOIL anti-ice switches ON.
    E. Advance affected throttle slowly.
    (5) If engine surging or popping returns, turn the ENG anti-ice 
switch OFF.
    (6) After normal operation has been established, the 
autothrottles may be re-engaged.

    Note: A NO MODE light may be annunciated due to abnormal bleed 
configuration.''

    (c) Within 60 months after the effective date of this AD, remove 
any DFGC having a part number other than 4034241-972, and replace it 
with a DFGC having part number 4034241-972, in accordance with 
McDonnell Douglas Service Bulletin MD80-22-111, dated May 23, 1995. 
Once these actions are accomplished, the AFM revisions required by 
paragraphs (a) and (b) of this AD may be removed.

    Note 2: McDonnell Douglas Service Bulletin MD80-22-111, dated 
May 23, 1995, references Honeywell Service Bulletin 4034241-22-44, 
dated May 22, 1995, as an additional source of service information.

    Note 3: Paragraph 1.B of McDonnell Douglas Service Bulletin 
MD80-22-111, dated May 23, 1995, specifies certain concurrent 
actions that affect airplanes equipped with DFGC's having part 
numbers other than 4034241-971.

    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Los Angeles Aircraft Certification 
Office (ACO), 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, Los Angeles ACO.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles ACO.

    (e) 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 October 12, 1995.

S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-25837 Filed 10-17-95; 8:45 am]
BILLING CODE 4910-13-U