[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
