[Federal Register Volume 60, Number 237 (Monday, December 11, 1995)]
[Proposed Rules]
[Pages 63465-63468]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-30074]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-226-AD]


Airworthiness Directives; Boeing Model 747 Series 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), applicable to certain Boeing Model 747 series 
airplanes, that would have required modification of the left and right 
inboard elevator servo assemblies and the hydraulic routing of the 
right inboard elevator power control package (PCP). That proposal was 
prompted by a report of an uncommanded right elevator deflection after 
takeoff and reports of elevator/control column bumps during landing 
gear retraction on these airplanes. This action revises the proposed 
rule by revising the applicability of the proposed AD to add additional 
airplanes and additional part numbers of the elevator PCP's, and by 
including additional service information. The actions specified by this 
proposed AD are intended to prevent uncommanded elevator deflection, 
which could result in structural damage and reduced controllability of 
the airplane.

DATES: Comments must be received by January 5, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-226-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 Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207; and Parker Hannifin Corporation, Customer 
Support Operations, 16666 Von Karman Avenue, Irvine, California 92714. 
This information may be examined at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Kathi N. Ishimaru, Aerospace Engineer, 


[[Page 63466]]
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (206) 227-2674; fax (206) 
227-1181.

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-226-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-226-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 Boeing Model 747 series airplanes, was published as a notice of 
proposed rulemaking (NPRM) in the Federal Register on March 3, 1995 (60 
FR 11942). That NPRM would have required modification of the left and 
right inboard elevator servo assemblies and re-routing the hydraulic 
tubing of the inboard elevator power control package (PCP). That NPRM 
was prompted by a report of an uncommanded right elevator deflection 
after takeoff and reports of elevator/control column bumps during 
landing gear retraction on these airplanes. That condition, if not 
corrected, could result in structural damage and reduced 
controllability of the airplane.
    Due consideration has been given to the comments received in 
response to the NPRM.
    One commenter requests that paragraph (a) of the proposal be 
revised to cite the latest revision of Boeing Alert Service Bulletin 
747-27A2348 when referring to the applicability of that paragraph. This 
commenter states that Revision 1 of the service bulletin includes 
additional airplanes that are also subject to the proposed AD. The FAA 
concurs. The FAA inadvertently cited the original version, dated 
November 17, 1994, of Boeing Alert Service Bulletin 747-27A2348 in 
paragraph (a) of the proposal when referring to the applicable 
airplanes for that paragraph. Since that revision level is incorrect, 
the FAA has removed it and referenced Revision 1, dated January 26, 
1995, in its place in paragraph (a) of the supplemental NPRM.
    One commenter states that Model 747SP series airplanes should be 
subject to paragraph (b) of the proposal. The FAA acknowledges that 
Model 747SP series airplanes were inadvertently omitted from the 
applicability of the proposal. The FAA's intent was that the proposed 
rule be applicable to all Model 747 series airplanes (i.e., Model 747-
100, -200B, -200F, -200C, 747SR, 747SP, 747-100B, -300, -100B SUD, -
400, -400D, and -400F series airplanes). Therefore, the FAA has revised 
the applicability statement of the supplemental NPRM accordingly.
    Since these changes expand 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.
    In addition, due consideration has been given to the following 
additional comments, which do not change the scope of the originally 
proposed rule, received in response to the NPRM.
    Three commenters request that the compliance time for paragraph (a) 
of the proposal be extended from the proposed 1 year. One of these 
commenters states that such an extension will allow operators to 
accomplish the modification during a regularly scheduled heavy 
maintenance visit. The FAA does not concur. In developing an 
appropriate compliance time for this action, the FAA considered not 
only the degree of urgency associated with addressing the subject 
unsafe condition, but the availability of required parts and the 
practical aspects of installing the required modification within an 
interval of time that parallels normal scheduled maintenance for the 
majority of affected operators. The manufacturer has advised that an 
ample number of required parts should be available for modification of 
the U.S. fleet within the proposed compliance period. Further, the FAA 
has determined that a heavy maintenance visit is not required to 
accomplish the modification.
    Several commenters state that paragraph (b) of the proposed rule is 
unjustified because there have been no reports of actuator jamming on 
the classic Model 747 (747-100, -100B SUD, -200, -300, SR, SP) series 
airplanes after accumulating 87 million flight hours. One of these 
commenters states that the safety concern surrounding the configuration 
of the servo valve assembly of the inboard elevator PCP is theoretical 
at best.
    The FAA does not concur with the commenters' suggestion that 
paragraph (b) of the proposed rule is unjustified. The FAA finds that 
the lack of reported jams and subsequent uncommanded elevator motion 
may be attributed, in part, to the small percentage of airplanes that 
recorded the elevator position while accumulating the 87 million flight 
hours. Paragraph (c)(10) of section 121.343, ``Flight recorders'', of 
the Federal Aviation Regulations (FAR) (14 CFR 121.343) requires that 
operators record either the control column or pitch control surface 
position (i.e., the position of the elevator and the stabilizer) of the 
airplane. Operators may comply with section 121.343 by electing to 
record the control column position, which is not a positive indicator 
of the elevator position. Consequently, incidents of uncommanded 
elevator motion due to actuator jamming may have occurred, but were not 
reported due to the flightcrew's inability to confirm the anomaly. 
Furthermore, the FAA finds that uncommanded elevator motion may occur 
on all Boeing Model 747 series airplanes if the servo valve secondary 
slide moves to the valve's internal stop. Therefore, the FAA finds that 
this AD action is warranted since an unsafe condition exists, which is 
identified as reduced controllability or structural damage to the 
airplane due to asymmetric elevator.
    One commenter states that only Model 747-400 series airplanes have 
experienced actuator jamming with uncommanded elevator deflection. The 
commenter also states that the uncommanded elevator deflection problem 
has been directly attributed to 

[[Page 63467]]
the fact that Model 747-400 series airplanes have the hydraulic system 
number 4 connected to the pressure sensitive side of the servo valve of 
the right inboard elevator PCP. The commenter contends that rerouting 
the hydraulic tubing, as required by paragraph (a) of the proposal 
(which references Boeing Alert Service Bulletin 747-27A2348, Revision 
1, dated January 26, 1995, as the appropriate source of service 
information) will alleviate this problem. The commenter notes that 
Model 747-100, -200, -300, and SP series airplanes, which do not have 
the hydraulic system number 4 connected to the pressure sensitive side 
of the servo valve of the right inboard elevator PCP, have not 
experienced the uncommanded elevator deflection problem.
    From this comment, the FAA infers that the commenter is requesting 
that paragraph (b) of the proposal be deleted. The FAA does not concur. 
The FAA has reviewed the pressure survey data for the number 3 and 
number 4 systems that was submitted by another commenter. The FAA finds 
that pressure fluctuations, which contribute to uncommanded elevator 
deflection, occur in hydraulic system number 3, as well as hydraulic 
system number 4. Therefore, the FAA finds that these data do not 
substantiate the commenter's suggestion that routing the hydraulic 
system number 3 to the sensitive side of the servo valve would preclude 
uncommanded elevator deflection.
    One commenter states that paragraph (b) of the proposal, which is 
applicable to certain Model 747-100, -200, -300, and -400 series 
airplanes, references Parker Service Bulletin 327400-27-171 as the 
appropriate source of service information. The commenter further states 
that this service bulletin is not applicable to certain Model 747-100, 
-100B SUD, -200, -300, SR, and SP series airplanes, since the elevator 
power control packages specified in Parker Service Bulletin 327400-27-
171 are not installed on these airplanes. The FAA's intent was to 
reference a service bulletin that addressed a modification for all 
affected airplane models. The FAA has reviewed and approved Parker 
Service Bulletin 93600-27-173, dated May 17, 1995. The modification 
procedures described in this service bulletin are identical to those 
described in Parker Service Bulletin 327400-27-171. The effectivity 
listing of Parker Service Bulletin 93600-27-173 contains elevator PCP's 
having part numbers
(P/N) 93600-5005 through -5051 inclusive, which are installed on 
certain Model 747-100, -100B SUD, -200, -300, SR, and SP series 
airplanes. The FAA has revised the applicability statement of the 
supplemental NPRM to include these additional P/N's. Additionally, the 
FAA has revised paragraph (b) of the supplemental NPRM to include this 
service bulletin as an additional source of service information.
    One commenter requests that applicability of paragraph (b) of the 
proposal be limited to Model 747-100, -100B SUD, -200, -300, SR, and SP 
series airplanes (``classic'') having cumulative line (C/L) 696 and 
subsequent and that the compliance time be extended from 3 years to 5 
years for those airplanes. The commenter contends that the aft fuselage 
limit load can be exceeded if the residual pressure at the actuator 
pistons exceeds 800 pounds per square inch (psi)/cylinder. The 
commenter further contends that the probability of exceeding this is 
less than 1  x  10e-5. This pressure assumes the valve jammed at the 
most adverse position achievable from pilot inputs. The commenter 
states that the aft fuselage limit load can be exceeded for classic 
airplanes having C/L 001 through 695 inclusive, if the residual 
pressure at the actuator pistons exceeds 1,700 psi/cylinder. The 
commenter also states that the probability of exceeding the structural 
limit is less than 1  x  10e-9.
    The FAA does not concur with the commenter's request to limit the 
applicability and extend the compliance time of paragraph (b) of the 
proposal. Following a review of the commenter's probability analysis, 
the FAA has determined that the commenter has based its analysis on a 
sampling that was much too small from which accurate statistical 
conclusions that would be representative of the fleet could be drawn. 
Further, the FAA finds that the flow rate and differential pressures 
used by this commenter were not substantiated to be the worst case 
scenario. Therefore, based on this flawed probability analysis, no 
change to the supplemental NPRM is warranted.
    One commenter requests that Boeing Model 747-400 series airplanes 
be removed from the applicability of paragraph (b) of the proposal. The 
commenter states that if the valve jams, the resultant asymmetric 
elevator will not result in structural damage on these airplanes. The 
FAA does not concur. The FAA has determined that, although the 
asymmetric elevator may not damage Model 747-400 series airplanes, an 
unsafe condition (i.e., reduced controllability) still exists.
    Two commenters request that the compliance time for paragraph (b) 
of the proposal be extended from the proposed 3 years to 5 years. One 
commenter states that it does not have enough seed units to accomplish 
the modification at their own facilities within the proposed compliance 
time. The FAA does not concur. As stated above, the FAA considered the 
availability of required parts and the practical aspects of installing 
the required modification. In addition, the FAA finds that other 
maintenance facilities are available to operators that are unable to 
accomplish the modification at their own facilities. However, under 
paragraph (c) of the proposed rule, the FAA may approve requests for 
adjustments to the compliance time if data are submitted to 
substantiate that such an adjustment would provide an acceptable level 
of safety.
    One commenter questions the FAA's estimate of the cost of required 
replacement parts for classic Model 747 series airplanes. The commenter 
states that the $3,720 per airplane figure, presented in the cost 
impact information in the preamble to the notice, is too low. This 
commenter suggests that parts costs will be approximately $7,440 per 
airplane (2 elevator power control packages at $3,720 each). After 
considering the data presented by the commenter, the FAA concurs that 
the cost of required parts per airplane is higher than previously 
estimated; the economic impact information, below, has been revised to 
indicate this higher amount.
    There are approximately 672 Model 747-100, -100B SUD, -200, -300, 
SR, and SP series airplanes, and 357 Model 747-400 series airplanes of 
the affected design in the worldwide fleet, a total of 1,029 airplanes.
    The FAA estimates that 114 Model 747-100, -100B SUD, -200, -300, 
SR, and SP series airplanes of U.S. registry would be affected by this 
proposed AD, that it would take approximately 73 work hours per 
airplane to accomplish the proposed actions, and that the average labor 
rate is $60 per work hour. Required parts would cost approximately 
$7,440 per airplane. Based on these figures, the cost impact of the 
proposed AD on U.S. operators is estimated to be $1,347,480, or $11,820 
per airplane.
    The FAA estimates that 65 Model 747-400 series airplanes of U.S. 
registry would be affected by this proposed AD, that it would take 
approximately 111 work hours per airplane to accomplish the proposed 
actions, and that the average labor rate is $60 per work hour. Required 
parts would cost approximately $12,269 per airplane. Based on these 
figures, the cost impact 

[[Page 63468]]
of the proposed AD on U.S. operators is estimated to be $1,230,385, or 
$18,929 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this AD were not adopted.
    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 (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 adding the following new 
airworthiness directive:

Boeing: Docket 94-NM-226-AD.

    Applicability: Model 747 series airplanes, equipped with Parker 
inboard elevator power control packages (PCP) having part numbers 
(P/N) 93600-5005 through -5051 inclusive, or P/N's 327400-1001, -
1003, -1005, and -1007; 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 (c) 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 uncommanded elevator deflection, which could result 
in structural damage and reduced controllability of the airplane, 
accomplish the following:
    (a) For Model 747-400 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-27A2348, Revision 1, dated January 26, 
1995: Within 1 year after the effective date of this AD, modify the 
hydraulic tubing of the right inboard elevator PCP, in accordance 
with Boeing Alert Service Bulletin 747-27A2348, Revision 1, dated 
January 26, 1995.
    (b) For all airplanes: Within 3 years after the effective date 
of this AD, modify the left and right servo assemblies of the 
inboard elevator PCP, in accordance with Parker Service Bulletin 
327400-27-171, Revision 1, dated April 14, 1995, or Parker Service 
Bulletin 93600-27-173, dated May 17, 1995, as applicable.
    (c) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle 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, Seattle ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on December 5, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-30074 Filed 12-8-95; 8:45 am]
BILLING CODE 4910-13-U