DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0915; Project Identifier AD-2020-00661-Q;
Amendment 39-21501; AD 2021-08-07]
RIN 2120-AA64

Airworthiness Directives; Rockwell Collins, Inc., Global
Positioning Systems

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain Rockwell Collins, Inc. (Rockwell Collins), GPS-4000S Global
Positioning Systems (GPS) installed on airplanes. This AD was prompted
by an un-annunciated GPS position error, which could cause a misleading
localizer performance with vertical guidance (LPV) glidepath, resulting
in controlled flight into terrain (CFIT). This AD requires upgrading
the GPS-4000S. The FAA is issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective May 12, 2021.

ADDRESSES: For service information identified in this final rule,
contact Rockwell Collins, Inc., 400 Collins Road NE, Cedar Rapids, IA
52498; phone: (319) 295-5000; email:
customersupport@rockwellcollins.com; website: www.rockwellcollins.com.
You may view this service information at the FAA, Airworthiness
Products Section, Operational Safety Branch, 901 Locust, Kansas City,
MO 64106. For information on the availability of this material at the
FAA, call (816) 329-4148.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2020-0915; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains this final rule, any
comments received, and other information. The address for Docket
Operations is U.S. Department of Transportation, Docket Operations, M-
30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue
SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Paul Rau, Aviation Safety Engineer,
Wichita ACO Branch, FAA, 1801 Airport Road, Wichita, KS 67209; phone:
(316) 946-4149; fax: (316) 946-4107; email: paul.rau@faa.gov or Wichita-
COS@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to Rockwell Collins GPS-
4000S GPS installed on airplanes. The NPRM published in the Federal
Register on October 29, 2020 (85 FR 68501). The NPRM was prompted by
the FAA being notified of a software error in GPS P/N 822-2189-100 that
can result in an un-annunciated inaccurate GPS position in the region
within approximately 1,000 miles (+/-20 degrees) of 180 degrees west
longitude. The software improperly applies the wide area augmentation
system ionospheric delay corrections to the GPS signal from satellites
located across the 180th meridian. Due to this anomaly, the position
accuracy may be diminished such that the GPS-4000S P/N 822-2189-100
will not support LPV approaches in the affected region. In the NPRM,
the FAA proposed to require removing P/N 822-2189-100 GPS-4000S GPS
from the airplane and installing P/N 811-2189-101 GPS-4000S GPS. The
FAA is issuing this AD to prevent a misleading glidepath on an affected
LPV approach, resulting in CFIT.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from five commenters. The commenters were
the Air Line Pilots Association, International (ALPA), Bombardier
Aviation (Bombardier), Delta Air Lines, Inc. (Delta), Airbus Canada,
and Transport Canada Civil Aviation (Transport Canada). The following
presents the comments received on the NPRM and the FAA's response to
each comment.

Supportive Comment

ALPA supported the AD without change.

Request Regarding the Unsafe Condition

Bombardier requested the FAA clarify paragraph (e) because it does
not describe the unsafe condition accurately. Bombardier stated that
the reference to a GPS vertical error is misleading and recommended
rewording it to state that a GPS software anomaly causes an
undetectable and inaccurate horizontal position from the Global
Navigation Satellite System (GNSS).
The FAA disagrees. The software error in the GPS-4000 produces both
horizontal and vertical position inaccuracies in the affected region.
The FAA determined the vertical error results in an unsafe condition as
it could cause the airplane to follow a glidepath below the obstacle
clearance surface of the LPV approach.

Request Regarding Replacement of the GPS-4000S

Delta requested the FAA change the proposed requirement in
paragraph (g)(1) to replace GPS-4000S P/N 822-2189-100 so that the AD
does not prevent installation of a GPS P/N that is unaffected by the
unsafe condition. Delta stated GPS-4000S P/N 822-2189-011 is two-way
interchangeable with P/N 822-2189-100 as a set and is not affected by
the unsafe condition. Delta also stated that Rockwell Collins could
develop new GPS P/Ns that are not subject to the unsafe condition,
which operators could not install without obtaining approval for an
alternative method of compliance (AMOC), based on the proposed
paragraph (g)(1). Delta requested the FAA change paragraph (g)(1) to
require replacing GPS-4000S GPS P/N 822-2189-100 with ``an improved
part number.''
The FAA agrees. It is not necessary for the AD to require
installing P/N 822-2189-101 because requiring the removal of P/N 822-
2189-100 will resolve the unsafe condition. Operators may replace GPS
P/N 822-2189-100 with any other system approved for installation in
their aircraft, although the FAA expects installation of P/N 822-2189-
101 will be the most common method.
The FAA has revised the AD to only require removing GPS-4000S GPS
P/N 822-2189-100 from service without requiring replacement with a
specific P/N GPS.

Requests Regarding Installation Prohibition

Airbus Canada and Transport Canada commented on the FAA's proposal
to prohibit the installation of the GPS-4000S GPS P/N 822-2189-100 as
of the effective date of the AD instead of once P/N 822-2189-101 has
been installed. The commenters stated that this may create dispatch
issues for operators depending on the number of available parts.
The FAA agrees and has changed the prohibition of installation to
take effect 24 months after the effective date of the AD. Operators may
install a GPS-4000S GPS P/N 822-2189-100 to address maintenance/repair
issues prior to complying with the AD. Once an operator has removed
GPS-4000S GPS P/N 822-2189-100 to comply with the AD, the operator must
maintain that configuration and may not change it to install a GPS-
4000S GPS P/N 822-2189-100 without an approved AMOC.

Request Regarding Applicability

Delta requested the FAA change the applicability to specify only
those aircraft types with the affected software installed. Delta stated
that as proposed, the AD would require all operators to review records
to verify whether the affected GPS P/N is installed on all of their
airplane fleets, regardless of whether it is type certificated or
supplemental type certificated.
The FAA disagrees. The FAA issues an AD against an appliance when,
as in this case, the unsafe condition exists in the appliance. If
known, the FAA will list the aircraft models that the appliance might
be installed on. However, this would not be an all-inclusive list and
would still require all operators to check their airplanes for the
affected appliance, regardless of whether the model of their airplane
is listed.
The FAA did not change this AD based on this comment.

Requests Regarding Reinstatement of LPV Approaches

Airbus Canada stated that the NPRM does not mention that Rockwell
Collins removed the LPV approaches from the impacted airports. Airbus
Canada requested that the AD provide credit for this. Transport Canada
asked whether Rockwell Collins and the FAA will return the affected
Alaska LPV procedures to the Navigation database for customers who have
updated their entire fleet with the P/N 822-2189-101 version of the
GPS-4000S.
The FAA disagrees with this comment. The FAA infers that the
commenters are referencing Rockwell Collins' removal of the affected
LPV approaches from the Rockwell Collins Navigation database beginning
in February 2020. This LPV approach removal was initiated by Rockwell
Collins as a temporary mitigation, but it affects all versions of the
GPS-4000S that use the database, including those (such as the -101
version) that do not have the unsafe condition. Accordingly, the FAA
did not base its determination and the corrective actions of this AD on
the removal of affected LPV approaches.
The FAA did not change this AD based on this comment.

Conclusion

The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for the changes described
previously, this AD is adopted as proposed in the NPRM. None of the
changes will increase the economic burden on any operator.

Related Service Information

The FAA reviewed Rockwell Collins Service Information Letter GPS-
4X00( )-19-3, Revision No. 2, dated March 25, 2020. The service letter
describes the unsafe condition and provides operating limitations for
approaches to airports in the affected region until the software is
upgraded.
The FAA also reviewed Rockwell Collins Service Bulletin GPS-4X00(
)-34-510, Revision No. 1, dated March 6, 2020. The service bulletin
specifies procedures for upgrading the GPS-4000S software, which
removes P/N 822-2189-100 and installs P/N 822-2189-101.

Costs of Compliance

The FAA estimates that this AD affects 3,500 airplanes of U.S.
registry. The FAA estimates that 2,000 airplanes have two GPS-4000S
units installed and 1,500 airplanes have one GPS-4000S unit installed.
The FAA estimates the following costs to comply with this AD:

Estimated Costs

The FAA has included all known costs in this cost estimate.
According to the manufacturer, however, some of the costs of this AD
may be covered under warranty, thereby reducing the cost impact on
affected operators.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.

Regulatory Findings

This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect 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.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, 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.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive: