[Federal Register Volume 61, Number 245 (Thursday, December 19, 1996)]
[Rules and Regulations]
[Pages 66898-66900]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-32050]



[[Page 66898]]

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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-121-AD; Amendment 39-9858 ; AD 96-25-15]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727-200 Series Airplanes; 
McDonnell Douglas MD-11 Airplanes; and British Aerospace Avro Model 
146-RJ Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain transport category airplanes equipped with 
certain Honeywell Standard Windshear Detection System (WSS). It 
requires a revision to the airplane flight manual to alert the 
flightcrew of the potential for significant delays in the WSS detecting 
windshear when the flaps of the airplane are in transition. This 
amendment also requires replacement of the currently-installed line 
replaceable unit (LRU) with a modified LRU having new software that 
eliminates delays in the WSS. This amendment is prompted by a report of 
an accident during which an airplane encountered severe windshear 
during a missed approach. The actions specified by this AD are intended 
to prevent significant delays in the WSS detecting hazardous windshear, 
which could lead to the loss of flight path control.

EFFECTIVE DATE: January 23, 1997.
ADDRESSES: Information pertaining to this rulemaking action may be 
examined at the Federal Aviation Administration (FAA), Transport 
Airplane Directorate, Rules Docket, 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: J. Kirk Baker, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130L, FAA, Los Angeles Aircraft 
Certification Office, 3960 Paramount Boulevard, Lakewood, California 
90712; telephone (310) 627-5345; fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain transport category 
airplanes equipped with certain Honeywell Standard Windshear Detection 
System (WSS) series airplanes was published in the Federal Register on 
September 13, 1996 (61 FR 48431). That action proposed to require a 
revision to the FAA-approved AFM to alert the flightcrew of the 
potential for significant delays in the WSS detecting windshear when 
the flaps of the airplane are in transition. That action also proposed 
to require replacement of the currently-installed LRU with a modified 
LRU having new software that eliminates delays in the WSS.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request To Eliminate Installation Requirement

    One commenter objects to paragraph (b) of the proposal, which would 
require operators to replace the currently installed LRU with a 
modified LRU having new software that eliminates delays in the WSS 
detecting windshear when the flaps of the airplane are in transition. 
This commenter considers that the proposed replacement would not 
enhance safety of the affected airplanes. This commenter also asserts 
that the proposed replacement requirement would result in changes in 
the aircraft configuration that would increase nuisance alerts, since 
the sensitivity reduction factor would be totally eliminated during 
flap transition.
    The FAA does not concur with the commenter's request to withdraw 
the proposal for the following reasons:
    First, the criteria for reactive windshear systems state that a 
warning must be issued once a windshear phenomenon is encountered. The 
criteria also state that the system must consider the airplane's 
available performance and the system's propensity for nuisance alerts 
due to turbulence. The FAA evaluates compliance with these criteria 
based upon the system's ability to issue timely warnings in all 
reasonably expected conditions. The FAA finds that encountering 
windshear during flap transition is a reasonably expected condition. 
This finding is based, in part, on the data obtained from the flight 
data recorder retrieved from the airplane involved in the accident in 
which windshear was encountered while the airplane was executing a 
missed approach.
    Second, the FAA has determined that conducting missed approaches, 
prior to encountering windshear, is a reasonably probable scenario. In 
such a scenario, the pilot would rely on prior knowledge attained in 
FAA-required training to recognize and recover from a windshear 
encounter, such as that provided in ``Windshear Training Aid,'' 
Revision 1, dated February 1990. Therefore, the pilot would likely 
determine that windshear has been encountered before the detection 
system actually detects the phenomenon, since the WSS is intended to be 
strictly an adjunct system, not a sole or primary system. The windshear 
training that pilots receive instructs them not to retract the 
airplane's flaps in this scenario. However, if the pilot does not 
believe that windshear has been encountered, the pilot may execute a 
normal go-around and retract the flaps, due to what the pilot perceives 
to be an unstable approach. Therefore, the FAA considers any delay in 
windshear detection to be unacceptable while the airplane's flaps are 
in transition. Consequently, the FAA finds that any improvement in 
warning time for the pilot will enhance safety for the affected 
airplanes.
    Third, the FAA does not concur with the commenter's assertion that 
installation of a modified LRU, and consequently, removal of the 
windshear warning delay during flap transition, would result in an 
increase in nuisance alerts. The FAA has reviewed all available data 
and cannot substantiate that elimination of the sensitivity reduction 
factor during flap transition would result in an increase in nuisance 
alerts. The FAA finds that the flaps are usually extended at altitudes 
higher than the altitude at which the system is armed. Furthermore, the 
FAA considers conducting a go-around with strong turbulence (excluding 
actual windshear conditions) to be a highly unlikely combination of 
events. In addition, the FAA will evaluate the modified Honeywell 
windshear computer, once it is developed, to determine compliance with 
the nuisance alert criteria, discussed above.

Request To Reconsider Compliance Time for Replacement

    This same commenter requests that the FAA reconsider the proposed 
compliance time of 30 months for replacement of the LRU with a modified 
unit. The commenter points out that Honeywell has neither developed an 
appropriate modification nor released service bulletins to provide the 
procedural methods for complying with the requirements of the proposed 
AD. The commenter notes that the same is true for compliance with AD 
96-02-06, amendment 39-9494 (61 FR 2095, January 25, 1996), which 
requires identical actions as those proposed, but applicable to certain 
other transport category airplanes.
    This commenter also points out that AD 96-02-06 provides for a 
compliance time of 36 months for the replacement;

[[Page 66899]]

the AD also states that, as of 18 months after February 26, 1996 (the 
effective date of that AD), no unmodified LRU can be installed on any 
airplane. The proposed AD's compliance times are 30 months for 
replacement, and 12 months before installation of unmodified units is 
prohibited.
    Although this commenter did not request any specific changes to the 
proposed rule, the FAA infers from these comments that the commenter is 
concerned that there will be a problem with parts availability within 
the compliance time. At the time that AD 96-02-06 was issued in January 
1996, the FAA had verified with the manufacturer that the lead time for 
developing the required LRU and making it available to operators was 
expected to be longer than 24 months, but not longer than 36 months. 
Since then, the manufacturer has given the FAA no new information that 
would change this schedule for availability of the required units; 
therefore, the FAA finds that the compliance times, as proposed, are 
appropriate.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule as proposed.

Cost Impact

    There are approximately 200 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 100 airplanes of U.S. registry 
will be affected by this AD.
    It will take approximately 1 work hour per airplane to accomplish 
the required AFM revision, at an average labor rate of $60 per work 
hour. Based on these figures, the cost impact of the AFM revision 
required by this AD on U.S. operators is estimated to be $6,000, or $60 
per airplane.
    It will take approximately 10 work hours per airplane to accomplish 
the required replacement, at an average labor rate of $60 per work 
hour. Required parts will be supplied by Honeywell at no cost to the 
operators. Based on these figures, the cost impact of the AD on U.S. 
operators is estimated to be $60,000, or $600 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the 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 adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from 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.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

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


Sec. 39.13   [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:
96-25-15  Boeing; McDonnell Douglas; and British Aerospace Regional 
Aircraft Limited, AVRO International Aerospace Division (Formerly 
British Aerospace, plc; British Aerospace Commercial Aircraft 
Limited): Amendment 39-9858. Docket 96-NM-121-AD.

    Applicability: The following models and series of airplanes, 
certificated in any category, equipped with Honeywell Standard 
Windshear Detection Systems (WSS) having the part numbers indicated 
below:

------------------------------------------------------------------------
    Manufacturer and model of                                           
            airplane               Type of computer        Part No.     
------------------------------------------------------------------------
Boeing 727-200 series...........  Expandable          4053818-904, -905,
                                   Windshear           or -906.         
                                   (Honeywell STC).                     
McDonnell Douglas MD-11 series..  Flight Control      4059001-906.      
                                   Computer (OEM TC).                   
British Aerospace Avro 146-       Flight Control      4068300-903.      
 RJ70A, -RJ85A, and -RJ100A        Computer (OEM TC).                   
 series.                                                                
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    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 (d) 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 significant delays in the Honeywell Standard 
Windshear Detection Systems (WSS) detecting hazardous windshear, 
which could lead to the loss of flight path control, accomplish the 
following:
    (a) Within 14 days after the effective date of this AD, 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.
    ``During sustained banks of greater than 15 degrees or during 
flap configuration changes, the Honeywell Windshear Detection and 
Recovery Guidance System (WSS) is desensitized and alerts resulting 
from encountering windshear conditions will be delayed.''
    (b) Within 30 months after the effective date of this AD, 
replace the currently- installed line replaceable unit (LRU) with a 
modified LRU having new software that eliminates delays in the WSS 
detecting windshear when the flaps of the airplane are in 
transition, in accordance with a method approved by the Manager, Los 
Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate. Accomplishment of this replacement constitutes 
terminating action for the requirements of paragraph (a) of this AD. 
After the replacement has been accomplished, the AFM limitation 
required by paragraph (a) of this AD may be revised to read as 
follows:

[[Page 66900]]

    ``During sustained banks of greater than 15 degrees, the 
Honeywell Windshear Detection and Recovery Guidance System (WSS) is 
desensitized and alerts resulting from encountering windshear 
conditions will be delayed.''
    (c) As of 12 months after the effective date of this AD, no 
person shall install on any airplane an LRU that has not been 
modified in accordance with paragraph (b) of this AD. However, an 
unmodified LRU may be installed on the airplane for up to 12 months 
after the effective date of this AD, provided that, during that 
time, the AFM limitation required by paragraph (a) of this AD 
remains in effect.
    (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 ACO. 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 2: 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.
    (f) This amendment becomes effective on January 27, 1997.

    Issued in Renton, Washington, on December 11, 1996.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-32050 Filed 12-18-96; 8:45 am]
BILLING CODE 4910-13-U