[Federal Register Volume 61, Number 17 (Thursday, January 25, 1996)]
[Rules and Regulations]
[Pages 2095-2099]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-1102]
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Rules and Regulations
Federal Register
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This section of the FEDERAL REGISTER contains regulatory documents
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Federal Register / Vol. 61, No. 17 / Thursday, January 25, 1996 /
Rules and Regulations
[[Page 2095]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 95-NM-55-AD; Amendment 39-9494; AD 96-02-06]
Airworthiness Directives; Boeing Models 727, 737, and 747 Series
Airplanes; McDonnell Douglas Model DC-8 and DC-9 Series Airplanes,
Model MD-88 Airplanes, and Models MD-11 and MD-90-30 Series Airplanes;
Lockheed Models L-1011-385 Series Airplanes; Fokker Models F28 Mark
1000, 2000, 3000, 4000, and 0100 Series Airplanes; and British
Aerospace Model Avro 146-RJ Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment supersedes two existing airworthiness
directives (AD), applicable to certain transport category airplanes
equipped with certain Honeywell Standard Windshear Detection Systems
(WSS). Those AD's currently require a revision to the FAA-approved
Airplane Flight Manual (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. Those AD's were prompted by a report of
an accident during which an airplane encountered severe windshear
during a missed approach. This amendment requires that the currently-
installed line replaceable unit (LRU) be replaced with a modified LRU
having new software that eliminates delays in the WSS detecting
windshear when the flaps of the airplane are in transition. 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: February 26, 1996.
ADDRESSES: Information concerning this AD may be obtained from or
examined at the Federal Aviation Administration (FAA), Transport
Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton,
Washington; or at the FAA, Los Angeles Aircraft Certification Office,
Transport Airplane Directorate, 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) by superseding AD 95-04-01,
amendment 39-9153 (60 FR 9619, February 21, 1995), and AD 95-09-05,
amendment 39-9208 (60 FR 20887, April 28, 1995) that was corrected on
May 12, 1995 (60 FR 26824, May 19, 1995); was published in the Federal
Register on June 13, 1995 (60 FR 31122). The proposed action is
applicable to certain transport category airplanes equipped with
certain Honeywell Standard Windshear Detection Systems (WSS). The
action proposed to require replacement of 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.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received. -
One commenter supports the proposed rule.
One commenter requests that the proposal be withdrawn since
unmodified WSS's provide the necessary level of safety required for
windshear detection. Furthermore, the commenter states that existing
AD's 95-04-01 and 95-09-05, which require that specific operational
procedures be followed, ensure that the flightcrews are properly
trained on the peculiarities of the Honeywell WSS. -
The FAA does not concur. The FAA finds that the unsafe condition
will be positively addressed by installing new software in the LRU that
will eliminate delays in the WSS detecting windshear when the flaps of
the airplane are in transition. Additionally, the FAA has determined
that long term continued operational safety will be better assured by
design changes to remove the source of the problem, rather than by
performing special operating procedures. Performing long-term special
operating procedures may not be providing the degree of safety
assurance necessary for affected airplanes in the fleet. This, coupled
with a better understanding of the human factors associated with
numerous continual special procedures, has led the FAA to consider
placing less emphasis on special procedures and more emphasis on design
improvements. This requirement for modification of the software is in
consonance with these considerations.
One commenter requests a revision to part 121 or part 135 of the
Federal Aviation Regulations (FAR) (14 CFR 121 or 135), since the
proposal does not address the root problem. The commenter states that
the proposal addresses ``reactive'' WSS's but, since ``predictive''
systems are now available, they should be required equipment on all
aircraft. The commenter contends that the ultimate solution to the
problem would be to require airborne predictive windshear detection
equipment, in conjunction with ground-based detection equipment, on all
airplanes operating in accordance with FAR part 121 or 135.
The FAA does not concur. According to section 39.1 (``Airworthiness
directives'') of the FAR (14 CFR 39.1), the issuance of an AD is based
on the finding that an unsafe condition exists or is likely to develop
in a product of a particular type design. This AD is based on such a
finding; it is the result of an investigation into the cause of an
accident involving a transport category airplane equipped with
Honeywell Standard Windshear Detection System. That investigation
revealed that a design feature in the windshear computer delayed
detection of windshear when the airplane's flaps were in transition.
From this investigation, the FAA determined that an unsafe condition
exists with regard to the flightcrew
[[Page 2096]]
being unaware of the potential for significant delays in the WSS
detecting windshear when the flaps of the airplane are in transition.
The issuance of this AD is to correct that unsafe condition. While the
commenter's request to require installation of specific equipment for
operation of air carriers or air taxis in accordance with part 121 or
part 135 has merit, it is clearly beyond the scope of this AD action.
One commenter requests a change in the applicability from the
proposed manufacturers of the airplanes to Honeywell, the manufacturer
of the faulty WSS's. The FAA does not concur in this case. While it is
assumed that an operator will know the models of airplanes it operates,
there is a potential that the operator will not know or be immediately
aware of specific items that are installed on its airplanes. The FAA
reasons that, by calling out all of the manufacturers of the airplane
models on which the subject item is likely to be installed, it will
prevent ``unknowing non-compliance'' with the AD on the part of the
operator.-
One commenter requests a revision to the proposal to include a
requirement to install placards in all airplanes to warn flightcrews of
the potential for significant delays in the WSS detecting windshear.
This commenter states that, since the WSS's on all airplanes within an
operator's fleet will not be modified simultaneously, the flightcrew
may not know whether the airplane has a modified or unmodified WSS.
This commenter contends that these proposed placards would minimize the
possibility for confusion as to the operating characteristics of the
specific WSS on the airplane. -
The FAA does not concur. The FAA finds that safety of the fleet of
affected airplanes will be ensured by the requirements of AD 95-04-01
and AD 95-09-04 [and retained in paragraph (a) of the final rule],
which require a limitation to the FAA-approved Airplane Flight Manual
(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. Typically, placards that are used in the cockpit are brief
and provide pilots with information that highlights significant changes
(i.e., labeling specific equipment inoperative). Longer, more detailed
changes to systems, such as that required by paragraph (a) of the final
rule, are normally detailed in the AFM. Therefore, the FAA finds that
the requiring the installation of a placard in the cockpit to warn
pilots of the potential for significant delays in the WSS detecting
windshear would not significantly enhance safety. Conversely, the FAA
has received comments to other rulemaking actions from operators
indicating that an overabundance of placards in the cockpit tends to
clutter the cockpit, which would make it easy for the flightcrew to
overlook important operational changes that require the pilot to take
necessary action. -
One commenter requests a revision to paragraph (a) of the proposal,
which restates the requirements of AD 95-04-01 and AD 95-09-05.
Proposed paragraph (a) requires 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.
The commenter requests the inclusion of references to the roll rate
desensitizing feature, which the commenter states would increase
flightcrew confidence in the system to detect windshear in all
configurations. -
The FAA does not concur. During certification testing, the FAA
evaluated the effects of bank angles and roll rates, and determined
that roll rates high enough to cause desensitization will produce the
15-degree bank angle that is noted in the AFM limitation required by
paragraph (a) of the final rule. The FAA has reviewed all currently
available data and finds that changes to paragraph (a) of the final
rule to incorporate roll rate compensations are not warranted. However,
paragraph (b) of the final rule has been changed to recommend revising
the AFM limitation [required by paragraph (a) of the final rule]
following installation of a modified LRU. The newly revised AFM
limitation alerts pilots that sustained banks greater than 15 degrees
will desensitize the WSS and that the potential exists for delays in
the WSS detecting windshear. -
Several commenters object to the proposed requirement of paragraph
(b) 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. Several commenters state
that the proposed replacement is unnecessary since such replacement
would not enhance safety of the affected airplanes. One of these
commenters notes that the proposed replacement requirement would result
in changes in aircraft configuration that may increase nuisance alerts,
since the sensitivity reduction factor would be totally eliminated
during flap transition. -
The FAA does not concur. The criteria for reactive windshear
systems state that a warning shall be issued once the windshear is
encountered. The criteria also 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, vis-a-vis the
accident during which an airplane encountered severe windshear during a
missed approach. -
Further, 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 phenomena since the WSS is intended to be
strictly an adjunct system, not a sole or primary system. The windshear
training that pilots receive instructs the pilot 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. -
Further, the FAA does not concur 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 the
commenter's assertion 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. Additionally, the FAA will evaluate the modified Honeywell
windshear computer to determine compliance with the nuisance alert
criteria, discussed above. -
Several commenters request an extension to the proposed compliance
[[Page 2097]]
time of 24 months for the replacement of the LRU. These commenters
suggest that a compliance time of 36 months would be more appropriate
to accommodate the time necessary to amend the supplemental type
certificate (STC) and revise the parts manufacture approval. One of
these commenters states that, since airplanes are prohibited from
flying with a mixture of modified and unmodified units, this extension
is necessary to ensure that Honeywell will be able to provide an
adequate number of modified units to the affected fleet.
The FAA concurs. The FAA has verified with the manufacturer that
the lead time for developing the required LRU will exceed the proposed
compliance time of 24 months. Further, the FAA has determined that
extending the compliance time to the suggested 36 months will
accommodate the time necessary for the manufacturer to develop, test,
and certify these units. The FAA finds that this 12-month extension
will not adversely affect safety significantly. Therefore, paragraph
(b) of the final rule has been revised accordingly.
One commenter requests that the proposed 24-month compliance time
for replacement of the LRU be shortened to 12 months. This commenter
suggests that the proposed compliance time may be too long, in light of
the catastrophic consequences of the identified unsafe condition.
The FAA does not concur that a shorter compliance time is
appropriate. The proposed 24-month compliance time was based on the
time originally estimated as necessary for operators to obtain modified
LRU's, plus the time necessary for operators to install that modified
LRU on the affected fleet. However, in light of the information
received concerning availability of these required parts, as discussed
above, the FAA has determined that a more appropriate time for
accomplishing the replacement of the LRU is 36 months. The FAA
considers that the AFM limitation currently required by AD 95-04-01 and
AD 95-09-05 [and retained in paragraph (a) of the final rule] will
ensure safety in the interim until the LRU's can be replaced.
One commenter requests a revision to paragraph (b) of the proposal
to specify that the modified LRU have software that would eliminate the
horizontal portion of the flap rate compensation feature only. The
commenter contends that removal of the vertical portion of the flap
rate compensation feature will increase nuisance alerts and will
minimally improve the time it takes for the WSS to detect hazardous
windshear when the flaps of the airplane are in transition.
The FAA does not concur. Since paragraph (b) of the final rule
requires that the FAA approve all replacement LRU's, the FAA approval
will include, among other factors, a review of the system's
susceptibility to nuisance warnings caused by both horizontal and
vertical compensations.
Two commenters request an extension to the proposed compliance time
of 12 months required by paragraph (c), which prohibits installation of
unmodified LRU's. One of these commenters states that a 12-month
extension would allow Honeywell, the manufacturer of these WSS's,
sufficient time to develop and manufacture an adequate number of
modified units. The other commenter suggests that an extension of 6
months would allow operators ample time to remove and return the units
to Honeywell to be reprogrammed.
The FAA concurs that a 6-month extension to the compliance time is
appropriate. The FAA has confirmed that the manufacturer will require
18 months to manufacture an adequate number of units. The FAA has
determined that such an extension to the compliance time will not
compromise the safety of the affected airplanes, and that the currently
required operating limitations will provide an acceptable level of
safety in the interim. Therefore, paragraph (c) of the final rule has
been revised to prohibit, installation of unmodified LRU's as of 18
months after the effective date of the AD.
One commenter supports the proposed rule, but recommends that the
proposed 12-month compliance time of paragraph (c), which prohibits
installation of unmodified LRU's, be shortened to 6 months. This
commenter states that, in light of the accident that prompted this AD
action, 12 months may be too long to permit unmodified LRU's to be
installed on the affected airplanes.
The FAA does not concur. Based upon the information received
concerning the new schedule for the availability of required parts,
discussed above, the FAA finds it necessary to extend this compliance
time to 18 months.
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 with the changes previously
described. The FAA has determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
the AD.
There are approximately 2,320 airplanes of the affected design in
the worldwide fleet. The FAA estimates that 1,618 airplanes of U.S.
registry will be affected by this AD.
The actions that are currently required by AD's 95-04-01 and 95-09-
05 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 on U.S. operators of the actions currently required is
estimated to be $97,080, or $60 per airplane.
The new actions that are required by this new AD will take
approximately 10 work hours per airplane to accomplish, at an average
labor rate of $60 per work hour. Required parts will be provided by
Honeywell at not cost to operators. Based on these figures, the cost
impact on U.S. operators of the new requirements of this AD is
estimated to be $970,800, 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.
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.
[[Page 2098]]
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 USC 106(g),40113, 44701.
Sec. 39.13 [Amended]
-2. Section 39.13 is amended by removing amendments 39-9153 (60 FR
9619, February 21, 1995) and 39-9208 (60 FR 20887, April 28, 1995), and
by adding a new airworthiness directive (AD), amendment 39-9494, to
read as follows:
96-02-06 Boeing; McDonnell Douglas; Lockheed; Fokker; and British
Aerospace Regional Aircraft Limited, AVRO International Aerospace
Division (Formerly British Aerospace, plc; British Aerospace
Commercial Aircraft, Limited): Amendment 39-9494. Docket 95-NM-55-
AD. Supersedes AD 95-04-01, Amendment 39-9153; and AD 95-09-05,
Amendment 39-9208.
Applicability: The following models and series of airplanes,
certificated in any category, equipped with Honeywell Standard
Windshear Detection Systems (WSS):
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Manufacturer and model of airplane Type of computer Part Nos.
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Boeing 727-100 and -200................ Standard Windshear 4061048-902, -903, and -904, 4068054-901,
(Honeywell STC). 4068060-901.
Boeing 737-100 and -200................ Standard Windshear 4061048-903, -904, and -905, 4068058-903.
(Honeywell STC).
Boeing 737-200......................... Performance Management 4050730-904 through -911, 4051819-906.
(Honeywell STC).
Boeing 737-300......................... Standard Windshear 4068060-901.
(Honeywell STC).
Boeing 747-100 and -200................ Standard Windshear 4061048-904.
(Honeywell STC).
McDonnell Douglas DC-8-50, -60, and -70 Standard Windshear 4068046-903.
(Honeywell STC).
McDonnell Douglas DC-9-10, -21, -31, - Standard Windshear 4068046-901, -902, 4068048-901, -902.
41, and -51. (Honeywell STC)-.
McDonnell Douglas DC-9-80 and MD-88.... Windshear (OEM TC)........ 4059845-902.
McDonnell Douglas MD-90-30............. Windshear (OEM TC)........ 4059845-910.
McDonnell Douglas MD-11................ Flight Control (OEM TC)... 4059001-901 through -905 (with windshear
option selected).
Lockheed L-1011-385-1, -385-1-14, -385- Standard Windshear (OEM 4068044-901.
1-15, and -385-3. TC).
Fokker F28 Mark 1000, 2000, 3000, and Standard Windshear 4068052-901.
4000. (Honeywell STC).
Fokker F28 Mark 0100................... Flight Management (OEM TC) 4052502-951 (with windshear option
selected).
British Aerospace Avro 146-RJ70A, - Flight Control (OEM TC)... 4068300-902.
RJ85A, and -RJ100A.
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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 (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 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) Revise the Limitations Section of the FAA-approved Airplane
Flight Manual (AFM) to include the following statement, at the time
specified in either paragraph (a)(1) or (a)(2) of this AD, as
applicable. 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.''
(1) For all Boeing, McDonnell Douglas, Lockheed, and Fokker
airplanes specified in the applicability statement of this AD:
Within 14 days after March 8, 1995 (the effective date of AD 95-04-
01, amendment 39-9153).
(2) For British Aerospace Model Avro airplanes specified in the
applicability statement of this AD: Within 14 days after May 15,
1995 (the effective date of AD 95-09-05, amendment 39-9208).
(b) Within 36 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:
``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 18 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. An unmodified
LRU may be installed up to 18 months after the effective date of
this AD, provided that, during that time, the AFM
[[Page 2099]]
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 February 26, 1996.
Issued in Renton, Washington, on January 18, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-1102 Filed 1-24-96; 8:45 am]
BILLING CODE 4910-13-U
