Document ID: FAA-2016-9226-0217
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: NavWorx, Inc. Automatic Dependent Surveillance Broadcast Universal Access Transceiver Units
Posted Date: 2017-06-06T04:00Z

[Federal Register Volume 82, Number 107 (Tuesday, June 6, 2017)]
[Rules and Regulations]
[Pages 25946-25954]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2017-11625]

-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-9226; Directorate Identifier 2016-SW-065-AD; 
Amendment 39-18910; AD 2017-11-11]
RIN 2120-AA64

Airworthiness Directives; NavWorx, Inc. Automatic Dependent 
Surveillance Broadcast Universal Access Transceiver Units

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: We are adopting a new airworthiness directive (AD) for 
NavWorx, Inc. (NavWorx), Automatic Dependent Surveillance Broadcast 
(ADS-B) Universal Access Transceiver Units (unit). This AD requires 
removing, disabling, or modifying the ADS-B unit. This AD was prompted 
by a design change that results in the unit communicating unreliable 
position information. The actions in this AD are intended to address an 
unsafe condition on these products.

DATES: This AD is effective July 11, 2017.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2016-
9226; or in person at the Docket Operations Office between 9 a.m. and 5 
p.m., Monday through Friday, except Federal holidays. The AD docket 
contains this AD, Supplemental Type Certificate (STC) No. SA11172SC, 
the economic evaluation, any comments received, and other information. 
The street address for the Docket Operations Office (phone: 800-647-
5527) is U.S. Department of Transportation, Docket Operations Office, 
M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue 
SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Kyle Cobble, Aviation Safety Engineer, 
Fort Worth Aircraft Certification Office (ACO), Rotorcraft Directorate, 
FAA, 10101 Hillwood Pkwy, Fort Worth, TX 76177, telephone (817) 222-
5172, email kyle.cobble@faa.gov; or Michael Heusser, Program Manager, 
Continued Operational Safety Branch, Fort Worth ACO, Rotorcraft 
Directorate, FAA, 10101 Hillwood Pkwy, Fort Worth, TX 76177, telephone 
(817) 222-5038, email michael.a.heusser@faa.gov.

SUPPLEMENTARY INFORMATION: 

Discussion

    On October 20, 2016, at 81 FR 72552, the Federal Register published 
our notice of proposed rulemaking (NPRM), which proposed to amend 14 
CFR part 39 by adding an AD that would apply to NavWorx ADS-B Model 
ADS600-B units, part number (P/N) 200-0012 and P/N 200-0013, and Model 
ADS600-EXP units, P/N 200-8013. The NPRM proposed to require removing 
the ADS-B unit before further flight and proposed to prohibit 
installing the affected ADS-B unit on any aircraft. The NPRM was 
prompted by a design change that resulted in the ADS-B units 
broadcasting a Source Integrity Level (SIL) of 3 instead of 0. A 
broadcast of SIL 0 is required because of the uncertified Global 
Positioning System (GPS) source included in the unit. The proposed 
actions were intended to prevent an ADS-B unit from communicating 
unreliable position information to Air Traffic Control (ATC) and nearby 
aircraft and a subsequent aircraft collision.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We received approximately 200 comments, mostly from 
individuals but also from NavWorx and organizations such as the 
Aircraft Owners and Pilots Association (AOPA), the Experimental 
Aircraft Association (EAA), and the Aircraft Electronics Association 
(AEA). The following presents the comments received on the NPRM and the 
FAA's response to each comment.

A. Support for the NPRM

    Five individual commenters supported the NPRM.

B. Comments Regarding the FAA's Justification of the Unsafe Condition

    Several commenters, including AOPA, requested that the FAA provide 
more information about the events that prompted this AD and the 
technical aspects surrounding the unsafe condition. We agree.
    Request: AOPA requested the FAA clarify whether the internal 
position source in the ADS-B units meets the performance requirements 
in Appendix B to Advisory Circular (AC) 20-165B. In support of this 
request, AOPA stated the FAA's contention that NavWorx did not present 
any data substantiating its SIL change is contrary to NavWorx's public 
statements that its testing verified the position source met the 
integrity levels required by the regulations. Similarly, NavWorx 
commented on the AD and maintained it has provided the FAA with data 
demonstrating the internal GPS met the requirements to transmit a SIL 
of 3.
    FAA Response: NavWorx has not demonstrated to the FAA that the 
internal position source meets the performance requirements in Appendix 
B to AC 20-165B \1\ for a SIL of 3. The design specifications for 
NavWorx's P/N 200-0012 and 200-0013 ADS-B units identify the internal 
GPS source for those units as an uncertified SiRF IV GPS. The SiRF IV 
is a commercial grade chipset not manufactured under an FAA Technical 
Standard Order (TSO). AC 20-165B requires the SIL be set at 0 when the 
ADS-B is integrated with an uncertified GPS source. When NavWorx 
submitted its software upgrade changing the SIL value from 0 to 3, no 
hardware design changes associated with the SIL value change were made 
to the ADS-B units and no testing data substantiating that SIL change 
was provided to the FAA. The only justification NavWorx cited for the 
software change was the FAA's termination of Traffic Information 
Service--Broadcast (TIS-B) services to aircraft broadcasting ADS-B with 
a SIL of 0. This data is available for review in Docket No. FAA-2016-
9226.
---------------------------------------------------------------------------

    \1\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/.
---------------------------------------------------------------------------

    Request: AOPA requested the FAA clarify its meaning of 
``uncertified GPS source'' since NavWorx has design approval through 
STC No. SA11172SC to install the ADS-B unit with the internal GPS on 
type-certificated aircraft, and since a compliant position source does 
not need to meet a specific TSO to meet the requirements set forth in 
Appendix B of AC 20-165B.
    Some commenters requested the FAA explain why it approved NavWorx's 
ADS-B units at all if the internal, uncertified GPS source is 
objectionable. Many commenters stated the NavWorx ADS-B units meet the 
performance and accuracy/integrity standards of TSO C-154c; others 
noted that NavWorx has stated its testing showed the units meet the 
requirements to broadcast a SIL of

[[Page 25947]]

3. Several commenters disagreed with the AD because the GPS source is 
not required to be certified separately from the ADS-B unit.
    FAA Response: The commenters, including NavWorx, are correct that 
the position source only needs to meet certain performance requirements 
and does not need to be certified under a TSO. However, despite 
NavWorx's statements and comments to the contrary, NavWorx has 
presented no data to the FAA--test plans and test results--that 
demonstrate the affected units with the internal SiRF IV GPS meet the 
performance standards to transmit a SIL of 3. Similarly, NavWorx has 
never demonstrated to the FAA that the affected units meet the 14 CFR 
Sec.  91.227 requirements to broadcast a SIL of 3 when using the 
internal SiRF IV GPS.
    NavWorx's TSO-C154c authorization and STC were approved based on 
the P/N 200-0012 and 200-0013 units broadcasting a SIL of 0 when using 
the internal uncertified GPS position source. NavWorx documented this 
as a limitation in the Aircraft Flight Manual Supplement (AFMS) for 
NavWorx's STC for ADS600-B installations. Section 2.6 of the AFMS, 
titled ``Uncertified GPS Receiver (P/N 200-0012 and 200-0013),'' 
states:

    The ADS600-B has an internal uncertified GPS WAAS receiver which 
does not meet the 14 CFR 91 FAA-2007-29305 rule for certified GPS 
position source. If the ADS600-B is configured to use the internal 
uncertified GPS as the position source the ADS-B messages 
transmitted by the unit reports: A Source Integrity Limit (SIL) of 0 
indicating that the GPS position source does not meet the 14 CFR 91 
FAA-2007-29305 rule.

    While 14 CFR Sec.  91.227 requires a SIL of 3, TSO-C154c (the TSO 
under which the affected units are produced) does not. Thus, when the 
affected units broadcast a SIL of 0, they are TSO-compliant. Until the 
performance requirements of 14 CFR Sec.  91.227 become effective on 
January 1, 2020, the FAA does not find the internal uncertified GPS 
source objectionable, as long as the ADS-B unit is correctly 
broadcasting a SIL of 0. It is NavWorx's change of the SIL setting in 
these units to 3, without any qualification of the internal uncertified 
GPS position source to support broadcast of SIL 3, that the FAA finds 
unacceptable. In this condition, the units are transmitting to ATC and 
to nearby aircraft that they have 14 CFR Sec.  91.227-compliant 
position source integrity, when their position source integrity is 
actually not compliant with that rule, or is unknown. We discuss the 
safety effects of this condition in greater detail below.
    Request: AOPA requested the FAA further explain its finding that 
the affected units create an unsafe condition. Many commenters 
questioned the FAA's determination that the units present an unsafe 
condition, and asked whether any units have actually caused a collision 
or safety incident. Many other commenters stated they have been 
operating with the NavWorx unit and find it accurate and reliable. 
Several commenters stated the NavWorx units increase safety and noted 
that the National Transportation Safety Board has recommended ADS-B 
units to the flying public.
    FAA Response: The FAA's safety concern is primarily that of 
integrity, and not necessarily accuracy, with respect to the NavWorx 
ADS-B unit's performance requirements. Accuracy refers to the 
probability of the unit's true position in relation to its reported 
position.\2\ Integrity refers to the trust that can be placed in the 
correctness of the information provided by the unit and is specified by 
a SIL value. The SIL value is set based on design data from the GPS 
position source manufacturer and reflects the probability that the 
position source will provide incorrect data without providing an alert. 
This depends on whether the GPS has fault detection and exclusion, 
where the equipment will detect a faulty satellite and exclude it from 
the navigational calculations. If the GPS does not have fault detection 
and exclusion, the probability that the position source will provide 
incorrect data increases. Commercial position sources, such as the SiRF 
IV GPS used in the NavWorx P/N 200-0012, 200-0013, and 200-8013 units, 
do not have fault detection and exclusion capabilities. This is 
significant in the event a GPS satellite signal fails or a GPS 
``signal-in-space error'' occurs.
---------------------------------------------------------------------------

    \2\ Accuracy of an aircraft's reported position is specified as 
Navigation Accuracy Category for Position, or NACP. A 
unit that complies with 14 CFR 91.227 has a NACP 
corresponding to an accuracy of better than 0.05 nautical miles. The 
NavWorx units' compliance with the 14 CFR 91.227 NACP (accuracy) 
performance requirements is not the concern that prompted this AD.
---------------------------------------------------------------------------

    The unsafe condition relates to the potential for the NavWorx unit 
to incorrectly report its own position to other aircraft and to ATC, by 
0.2 nautical miles (NM) or more, without providing an alert.\3\ It may 
also result in ATC providing incorrect and inappropriate separation 
instructions or traffic advisories to other aircraft for avoidance of 
the ADS600-B-equipped aircraft, based on the erroneous position being 
reported by the ADS600-B. In this situation, the pilot of the ADS600-B-
equipped aircraft would be unaware that his or her aircraft's ADS-B Out 
unit is broadcasting an erroneous position (possibly in excess of 0.2 
NM), since the ADS600-B would not be providing an alert for this 
condition. Depending on operating conditions, these effects may occur 
in instrument meteorological conditions where see-and-avoid is not 
possible. In view of these factors, this condition poses an 
unacceptable hazard to other users of the National Airspace System 
(NAS).
---------------------------------------------------------------------------

    \3\ 0.2 NM is the minimum integrity containment radius around 
the aircraft's reported position required by 14 CFR Sec.  91.227 
(c)(1)(iii).
---------------------------------------------------------------------------

    Although there have been no reported cases of a collision or safety 
incident resulting from an incorrect transmission by a NavWorx ADS-B 
unit to date, the potential for the unsafe condition exists as long as 
the units mislead ATC and nearby aircraft by broadcasting a SIL of 3 
that they have not been shown to meet. This AD action addresses that 
potential unsafe condition.
    The fact that commenters have made flight tests with satisfactory 
ADS-B performance monitor reports from the FAA, or that commenters' 
individual units have been operating successfully, does not negate the 
existence of an unsafe condition. Flight tests with the ADS-B 
performance monitor are designed primarily to show that the ADS-B 
equipment in an individual aircraft performs correctly as installed. 
These tests are of relatively short duration and occur in fault-free 
conditions. They are not engineering tests designed to evaluate the 
unit's ability to handle GPS signal-in-space errors and cannot be used 
to draw inferences about the unit's position source integrity.
    Although the FAA recognizes the benefits of ADS-B equipage and 
understands that the NavWorx units may work a large percentage of the 
time for an individual user, the FAA must consider the effect on the 
entire NAS. Since failure is based on a statistical probability, the 
odds that a unit will have a failure increase as more units are 
introduced into the NAS and operate for a longer period of time. The 
probability of a failure also increases when there is a GPS satellite 
malfunction, which could affect many aircraft since the information is 
used by ATC and ADS-B In equipped aircraft for separation. Therefore, 
despite any benefit to individual owners when the unit works without 
failure, the FAA has determined that an unsafe condition with the 
NavWorx units exists and requires corrective action because of the 
hazard they pose to other users of the NAS.

[[Page 25948]]

    Request: AOPA requested the FAA produce for public inspection the 
Small Airplane Risk Analysis (SARA) documentation.
    FAA Response: As part of our risk assessment, we initially 
performed a SARA. However, the SARA assumes failure on one airplane. 
The issue with the NavWorx ADS-B units poses risk to the NAS. 
Specifically, a malfunction at the satellite level could result in 
transmission of hazardously misleading position information from the 
ADS600-B-equipped aircraft to ATC and to other aircraft. It could also 
cause such malfunctions in all aircraft with the affected ADS-B units 
installed that are using the signal from the malfunctioning satellite 
to determine their position. Thus, we determined the SARA results 
provided questionable value, and that it was more appropriate to use 
the safety risk methodology from the ADS-B program, as documented in 
Safety Risk Management Document (SRMD) Critical Services: Standard 
Terminal Automation Replacement System (STARS) with Automatic Dependent 
Surveillance Broadcast (ADS-B) Only Addendum, SBS-036C, Revision 1, 
dated August 26, 2014 (SBS-036C).
    In SBS-036C, we analyze safety risk as a composite of two factors: 
The potential ``severity'' or worst possible consequence or outcome of 
an adverse effect that is assumed to occur, and the ``likelihood'' of 
occurrence for that specific adverse event. We assess both factors 
independently and then enter each as separate inputs into a risk 
matrix, which yields an overall level of risk for the event as Low 
(acceptable), Medium (acceptable with mitigation), or High 
(unacceptable). The corrective action, if any, is driven by the 
assessed overall risk. Figure ES-1 of SBS-036C contains the risk matrix 
the FAA used for this AD.
    The FAA considered an undetected position error event of 0.2 NM or 
more for a single aircraft as a ``Position error outside containment 
bound for single aircraft undetected by airborne equipment/ground 
automation'' hazard, which has a classified severity of ``hazardous'' 
per Table ES-1 and Appendix B of SBS-036C. Hazardous is defined in AC 
23.1309-1E, System Safety Analysis and Assessment for Part 23 
Airplanes,\4\ as resulting in a large reduction in safety margins, 
physical distress or higher workload, or serious or fatal injury to an 
occupant other than the flight crew. A large position error (0.2 NM or 
more) may lead to loss of separation, increased ATC workload, a 
reduction in safety margins, and a near midair collision. These are 
unsafe conditions that warrant a ``hazardous'' severity level for risk 
assessment purposes.
---------------------------------------------------------------------------

    \4\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/.
---------------------------------------------------------------------------

    From Table ES-1 of SBS-036C, the likelihood of this failure for a 
properly functioning system was assessed as extremely improbable. 
Figure ES-1 in SBS-036C is a risk matrix that yields an overall risk 
based on the severity classification and the assessed likelihood of 
occurrence. A severity classification of ``hazardous'' and an assessed 
likelihood of ``extremely improbable'' yields an overall risk of 
``Low,'' which is an acceptable risk.
    However, the likelihood assessment of ``extremely improbable'' in 
Table ES-1 is based on the aircraft's GPS receiver having either fault 
detection or fault detection and exclusion, which is required in order 
to meet the ADS-B Out position integrity requirements of 14 CFR 91.227. 
A GPS receiver with fault detection detects a faulty satellite signal 
and provides an alert of the fault. If the GPS receiver has fault 
detection and exclusion, it additionally excludes the faulty satellite 
signal from the position computation. Because the GPS position source 
in the NavWorx ADS600-B units has no demonstrated fault detection or 
exclusion features, the FAA determined the appropriate likelihood 
should be based on the GPS constellation fault rate of 
10-\4\ per hour (that is, a probability of 0.0001 
occurrences per flight hour). As a result, the FAA elevated the risk of 
the hazard and assessed a likelihood of ``remote.'' \5\ Using the 
severity classification of ``hazardous'' and an assessed likelihood of 
``remote'' yields an overall risk of ``High'' in Figure ES-1. This is 
an unacceptable risk.
---------------------------------------------------------------------------

    \5\ Although the CARB assessed a likelihood of ``remote,'' 
Figure 2 of AC 23.1309-1E assesses a likelihood between ``remote'' 
and ``probable,'' depending on the class of aircraft, for a 
probability of 10\-4\. Either likelihood classification would yield 
a High overall risk on the Figure ES-1 risk matrix.
---------------------------------------------------------------------------

    These determinations are documented in the meeting minutes from the 
FAA's Corrective Action Review Board (CARB) held on September 19, 2016. 
In accordance with FAA Order 8110.107A, Monitor Safety/Analyze Data, 
the CARB considered this safety issue on that date and determined that 
an unsafe condition existed with the units. This documentation is 
available for review in Docket No. FAA-2016-9226.
    Comment: A few commenters, including NavWorx, noted the FAA 
approved software revisions 4.0.7, 4.0.8, and 4.0.9, which included the 
software changes for the units to broadcast a SIL of 3.
    FAA Response: The commenters are correct that the FAA approved 
NavWorx's software changes identified as 4.0.7, 4.0.8, and 4.0.9. 
However, none of these changes identified on NavWorx's submittals 
affected the SIL value or referenced the SIL value change in 4.0.6. The 
FAA's approvals did not alter the FAA's previous written statements to 
NavWorx advising the equipment must report a SIL of 0 to remain 
compliant with TSO-C154c. This documentation is available for review in 
Docket No. FAA-2016-9226.

C. Requests To Allow Alternative Actions

    Request: Many commenters, including AOPA, requested that, since the 
internal GPS is the issue with the NavWorx unit, the AD allow the ADS-B 
units to use an external GPS position source or, similarly, that the AD 
not apply to units using an external GPS position source.
    FAA Response: We agree. The only external GPS position source 
approved by the FAA for interface with the ADS600-B is the Accord 
NexNav mini LRU GPS Receiver P/N 21000 (Accord external GPS).\6\ We 
revised the AD to allow interfacing the ADS-B unit with an Accord 
external GPS as an optional corrective action. For operators who wish 
to interface with other external position sources, under the provisions 
of paragraph (f) of this AD, we will consider requests for approval of 
an Alternative Method of Compliance (AMOC) if sufficient data is 
submitted to substantiate that the unit would provide an acceptable 
level of safety.
---------------------------------------------------------------------------

    \6\ Some commenters stated or implied that other external GPS 
sources, such as the Garmin 530W, the Garmin GNS 430W, the Garmin 
GNS 480, and the Garmin GTN 650, are approved for installation in 
the ADS600-B. Contrary to any documentation these commenters may 
have from NavWorx, the only FAA-approved external GPS source is the 
Accord NexNav mini P/N 21000. Documentation of this is available for 
review in Docket No. FAA-2016-9226.
---------------------------------------------------------------------------

    Request: Several commenters, including AEA, requested the AD allow 
disabling the unit rather than removing it.
    FAA Response: We agree. We revised the AD to allow disabling the 
unit as an optional corrective action.
    Request: Several commenters, including AOPA, requested the AD allow 
changing the SIL from 3 to 0 as an alternative to removing the unit.
    FAA Response: We agree. We did not include this option in the NPRM 
because NavWorx has stated it will not provide its customers with 
software to change the SIL to 0. However, we revised the AD to allow 
changing the

[[Page 25949]]

SIL to 0 as an alternative to removing the unit in the event such 
software becomes available and is approved by the FAA.
    Request: One commenter requested that the AD not apply to units 
with software versions prior to 4.0.6, because these units broadcast a 
SIL of 0 and thus are not subject to the unsafe condition.
    FAA Response: We agree. We considered excluding units with software 
prior to version 4.0.6 when we issued the NPRM. We did not exclude them 
because our understanding of the units is that there is no 
recordkeeping, marking, or indication from the unit itself that allows 
an operator to identify the current software version. However, changes 
to the AD in response to other comments render this exclusion 
unnecessary.
    Request: AOPA requested that we allow the units to remain in 
service if NavWorx upgrades the internal position source with a 
position source that meets the requirements of Appendix B to AC 20-
165B. Similarly, several commenters requested that we allow NavWorx to 
re-certify the unit.
    FAA Response: We agree. Should NavWorx upgrade its internal 
position source with a position source that meets the performance 
requirements of Appendix B to AC 20-165B, or demonstrate that the 
internal SiRF IV GPS meets those requirements, under the provisions of 
paragraph (f) of this AD, we will consider requests for approval of an 
AMOC.
    Request: Several commenters requested that we allow more time for 
compliance. Two of those commenters requested that we delay compliance 
until 2020, when the ADS-B operational rules become effective.
    FAA Response: We agree with extending the compliance time. We 
determined that safety will be maintained if the corrective actions are 
implemented within six months of the effective date of the AD, and we 
revised the AD accordingly.
    We disagree with delaying compliance until 2020. The FAA's ADS-B 
ground station network is already operational and in use by ATC 
nationwide, and ADS-B In is also widely used in general aviation 
aircraft for traffic awareness. Therefore, the fact that ADS-B Out will 
not be required equipment until 2020 does not negate the unsafe 
condition that exists from those units currently operating in the NAS.
    Request: Many commenters requested that the FAA withdraw the NPRM 
and instead work with NavWorx to address the unsafe condition. Some 
commenters inferred a failure by the FAA in this regard because it 
appeared it took the FAA six months to respond to NavWorx's design 
change notification. A few commenters expressed disappointment and 
outrage at the FAA's handling of the certification process with NavWorx 
and requested we constructively and immediately resolve this situation.
    FAA Response: We agree it is desirable to work with manufacturers 
to resolve differences of opinion regarding product compliance and 
correct identified safety concerns. The FAA made numerous efforts, in a 
variety of forms and over a considerable period of time, to resolve 
this situation with NavWorx. Those efforts were unsuccessful.
    After receiving NavWorx's design change, the FAA advised NavWorx 
that it could not manufacture the units as TSO C-154c units because 
NavWorx had not provided acceptable data to substantiate modifying the 
SIL value of the internal SiRF IV GPS to 3. Initially, NavWorx agreed 
to return the SIL to 0 and requested 60 days to effect this change. 
Instead, over two months later, NavWorx informed the FAA that it would 
not be returning the SIL value to 0 after all. The FAA continued to 
advise NavWorx, both verbally and in writing, that the SIL change 
rendered the units non-compliant with the TSO. The FAA also continued 
to request that NavWorx voluntarily return the SIL to 0, but NavWorx 
refused. The FAA met with NavWorx and explained the means of compliance 
in our existing guidance for certifying the SiRF IV GPS to broadcast a 
SIL of 3, as well as the process for submitting an alternate or 
equivalent means of compliance for approval. While NavWorx indicated 
its desire to initiate one of those processes, it did not. Instead, 
NavWorx continued to sell and ship the part-numbered 200-0012 and 200-
0013 units with the unapproved design change, and continued to furnish 
product software upgrades through its Web site to existing owners that 
contained the unapproved design change. When the FAA repeatedly 
requested to conduct a routine inspection of NavWorx's facility, in 
part to review NavWorx's units and data supporting its design change, 
NavWorx refused.
    After determining the situation created by NavWorx resulted in an 
unsafe condition, and without NavWorx's cooperation to correct the 
unsafe condition, the FAA found it necessary to issue an AD. 
Documentation of these events is available for review in Docket No. 
FAA-2016-9226.
    Request: One commenter requested the FAA allow a temporary, 
alternative solution in which operators would periodically validate the 
units by flight test.
    FAA Response: We disagree. Validation flight tests are not 
engineering tests and are not designed to evaluate the unit's position 
source integrity. The commenter's requested method of compliance would 
not correct the unsafe condition.
    Request: One commenter requested we exclude ADS-B units that are 
already installed from the requirements of the AD.
    FAA Response: We disagree. The FAA has determined an unsafe 
condition exists on the affected ADS-B units and that removal or 
correction of the units is required.
    Request: Two commenters request the AD not apply to aircraft 
operating under visual flight rules (VFR).
    FAA Response: We disagree. The FAA has determined that an unsafe 
condition with the NavWorx units exists and requires corrective action 
because of the hazard they pose to other users of the NAS. The NavWorx 
unit broadcasting a SIL of 3, when it is only authorized to broadcast a 
SIL of 0, has the potential to incorrectly report its own position to 
other aircraft and to ATC by 0.2 NM or more, without providing an 
alert. Even in visual meteorological conditions, this could result in 
the pilot of another aircraft visually searching the wrong sector of 
sky for the incorrectly reporting ADS600-B-equipped aircraft or 
incorrectly assessing the ADS600-B-equipped aircraft as not being a 
collision threat, based on the depicted relative position of the 
ADS600-B aircraft on its ADS-B In traffic display.
    Request: EAA and two individual commenters requested the AD not 
apply to experimental or light sport aircraft, since they are not 
regulated in the same manner as type-certificated aircraft. EAA states 
the FAA should address any valid airworthiness concerns with parts 
intended for experimental aircraft through a Special Airworthiness 
Information Bulletin (SAIB) or safety alert for operators (SAFO). Two 
commenters requested the AD apply to experimental aircraft, because 
those aircraft operate in the same airspace as type-certificated 
aircraft and should use equipment with the same integrity. A few 
commenters, including AOPA, requested we clarify whether the AD applies 
to experimental aircraft.
    FAA Response: We agree to clarify this issue. We confirm that the 
AD applies to all aircraft, including experimental, and we revised the 
AD to clarify the applicability. We made this

[[Page 25950]]

AD applicable to the ADS600-EXP P/N 200-8013 units because the design 
of the Model ADS600-EXP P/N 200-8013 is substantially identical to the 
Model ADS600-B P/N 200-0012 and 200-0013, specifically with regard to 
the internal GPS and the SIL setting. While some commenters are correct 
that the FAA has chosen to minimize regulations on experimental 
aircraft because of the level of the safety risk, these risks normally 
apply to the individual airplane and do not affect the overall NAS. The 
safety risks defined in this AD extend beyond one aircraft and could 
affect many other aircraft as well as ATC. Therefore, we find it 
necessary to include experimental aircraft in the AD's applicability.
    We do not agree that an SAIB or SAFO would be an appropriate 
solution. These documents contain information and recommended actions 
that are voluntary and not regulatory. Moreover, an SAIB is issued only 
for airworthiness concerns that do not rise to the level of an unsafe 
condition.
    The mission of the FAA is aviation safety. ADs are used by the FAA 
to correct known safety defects. It would be contrary to the intent of 
the FAA's mission and statutory authority to exclude certain aircraft 
when we have determined that a part installed on those aircraft has a 
safety problem.

D. Comments Regarding Costs of Compliance With This AD

    Request: Many commenters stated that the cost to comply with this 
AD is underestimated or inaccurate and requested the FAA revise its 
cost estimate. These commenters stated the cost should include the cost 
to replace the unit with a new ADS-B unit and costs associated with 
loss of utility; should increase the number of labor hours to account 
for indirect costs such as removal and reinstallation of associated 
equipment, research, and paperwork; and should increase the labor rate.
    FAA Response: We disagree. The cost analysis in AD rulemaking 
actions typically includes only the costs associated with complying 
with the AD. In this AD, the only required action is the removal of the 
unit, the deactivation of the unit, the coupling of the unit with an 
approved external GPS source, or the upgrading of the software in the 
unit to broadcast a SIL of 0. These actions are estimated to take 1 
work-hour each, except for coupling the unit with an approved external 
GPS source, which is estimated to take about 4 work-hours. The costs of 
associated required actions such as installing a placard or revising 
the flight manual are nominal. ADS-B Out equipment is not required for 
operation until January 1, 2020, and is only required for operation in 
certain specified airspace after that date. Individual operators are in 
the best position to determine whether they will need to install this 
equipment for the airspace they intend to operate in. Therefore, 
replacement of the unit is not necessary to comply with this AD.
    The labor rate of $85 per hour is provided by the FAA Office of 
Aviation Policy and Plans for the FAA to use when estimating the labor 
costs of complying with AD requirements.
    Request: Several commenters requested the FAA revise its 
determination that the AD is not a significant regulatory action. One 
commenter requested the FAA analyze the costs of the AD under the 
Regulatory Flexibility Act.
    FAA Response: We disagree. An AD is economically significant when 
the cost may have an annual effect on the economy of $100 million or 
more.\7\ Even if we were to include labor for indirect costs and the 
cost of replacing the unit with a new unit in our estimate, at an 
estimated cost of $10,000 per aircraft and $8 million for the U.S. 
fleet over the next three years, the AD would not rise to level of 
economically significant. In addition, ADs correct identified unsafe 
conditions, rather than raise an already adequate level of safety, and 
cannot be assessed in terms of benefits balancing costs, as would be 
the case for rulemaking that amends airworthiness standards.
---------------------------------------------------------------------------

    \7\ A ``significant regulatory action'' is defined in Executive 
Order 12866 (58 FR 51735, October 4, 1993).
---------------------------------------------------------------------------

    The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA) 
establishes as a principle of regulatory issuance that agencies shall 
endeavor, consistent with the objective of the rule and of applicable 
statutes, to fit regulatory and informational requirements to the scale 
of the businesses, organizations, and governmental jurisdictions 
subject to regulation. To achieve that principle, the RFA requires 
agencies to solicit and consider flexible regulatory proposals and to 
explain the rationale for their actions. The RFA covers a wide-range of 
small entities, including small businesses, not-for-profit 
organizations, and small governmental jurisdictions.
    Agencies must perform a review to determine whether a proposed or 
final rule will have a significant economic impact on a substantial 
number of small entities. If the agency determines that it will, the 
agency must prepare a regulatory flexibility analysis as described in 
the RFA.
    However, if an agency determines that a proposed or final rule is 
not expected to have a significant economic impact on a substantial 
number of small entities, section 605(b) of the RFA provides that the 
head of the agency may so certify and a regulatory flexibility analysis 
is not required. The FAA did make such a determination for this AD. The 
basis for this determination is now discussed.
    The FAA uses the Small Business Association (SBA) criteria for 
determining whether an affected entity is small. For aircraft 
manufacturers, aviation operators, and any business using an aircraft, 
the SBA criterion is 1,500 or fewer employees.
    NavWorx is a small entity, and this AD could have an adverse impact 
on its business interests. Besides NavWorx, the largest number of 
affected small entities would most likely be operators of ADS600-B-
equipped aircraft. Based on the estimated number of units in service, 
and assuming each unit is owned by a different small entity, the 
largest number of small entities affected is 800.
    The FAA estimates that there is a total population of 210,000 
general aviation and air taxi aircraft in the United States.\8\ Of 
these, approximately 70,300 (33.5%) are flown primarily for some type 
of business or commercial use and thus are potentially operated by a 
small entity. Aircraft flown primarily for personal use would not be 
operated by a small entity as defined by the SBA.
---------------------------------------------------------------------------

    \8\ Based on the FAA General Aviation and Air Taxi Activity 
Survey for calendar year 2015 (the most recent year of data 
available), table 1.2, General Aviation and Air Taxi Number of 
Active Aircraft by Primary Use. http://www.faa.gov/data_research/aviation_data_statistics/general_aviation/CY2015/media/2015_GA_Survey_Chapter_1_Tables_16SEP2016V2.xlsx.
---------------------------------------------------------------------------

    The FAA assumed all 70,300 commercial use aircraft are operated by 
small entities and that each small entity operates an average of 6 
aircraft,\9\ which yields an estimated number of 11,700 small entities. 
We also assumed that of the 800 affected units, 33.5% (270) are used in 
commercial operations.\10\ This

[[Page 25951]]

equates to a maximum of 2.3% (270/11,700) of small entities affected by 
this rule. This is not a substantial number of small entities under the 
RFA.
---------------------------------------------------------------------------

    \9\ We based this assumption on the sanction guidance in 
Appendix B of FAA Order 2150.3B, FAA Compliance and Enforcement 
Program, which classifies air carriers and operators by operating 
revenue, pilots employed, and aircraft operated for purposes of 
determining civil penalty amounts. http://rgl.faa.gov/Regulatory_and_Guidance_Library/.
    \10\ This assumption in particular is grossly high. First, some 
of the affected units are installed on experimental aircraft, which 
are prohibited from commercial operations and therefore could not be 
used by a small entity under the RFA. Second, of the approximately 
200 comments we received on the NPRM, only six commenters (NavWorx, 
a charitable aircraft operator, and four avionics installation 
businesses) could be presumed to be commercial entities. The 
remaining comments were submitted by individuals.
---------------------------------------------------------------------------

    Request: A few commenters requested or implied the FAA fund the 
costs of the AD.
    FAA Response: We disagree. The FAA, as a federal agency, is 
responsible for all directives, policies, and mandates issued under its 
authority. Although we have determined that an unsafe condition exists 
with the design change to the ADS-B unit, the manufacturer is 
responsible for the design change. Additionally, the FAA's budget does 
not include allocations to cover AD costs incurred in modifying 
privately-owned equipment.

E. Comments to the FAA's Rulemaking Process

    Request: Several commenters questioned the FAA's motive in 
proposing the AD. Some believed that the FAA is colluding with other 
ADS-B manufacturers or industry organizations. Others suggested the FAA 
is unfairly targeting NavWorx and would not be taking this action if it 
involved a larger manufacturer. We interpret these comments as 
requesting we withdraw the NPRM.
    FAA Response: We disagree. The FAA has not communicated with any 
other ADS-B product manufacturer or industry organization regarding the 
compliance or safety of NavWorx products. In issuing this AD, we 
followed established policy and procedures, including the public notice 
and comment procedures of the Administrative Procedures Act, as well as 
the DOT's ex parte policy, which can be found in Appendix 1 to 14 CFR 
part 11. We placed all ex parte comments in the rulemaking docket and 
considered all comments we received.
    We also disagree that we are unfairly targeting NavWorx. We have 
determined an unsafe condition exists on a NavWorx product and we are 
requiring corrective action accordingly. If the FAA identifies similar 
problems and determines that an unsafe condition exists on other ADS-B 
products, whether manufactured by NavWorx or other companies, we would 
take appropriate action to correct the unsafe condition.
    Request: An individual commenter questioned whether we intended to 
issue an AD against ADS-B transponders manufactured by Trig or Dynon. 
According to the commenter, the Trig transponder allows the installer 
to manually set the SIL value, and the commenter claims installers will 
improperly set the SIL at 3 to obtain traffic information. The 
commenter also states the Dynon ADS-B uses the same GPS source that is 
the subject of this AD.
    FAA Response: We are issuing this AD to correct an unsafe condition 
that we have determined exists on a NavWorx product. This AD is not 
applicable to Trig Avionics (Trig) or Dynon Avionics (Dynon) ADS-B 
units. In the case of the older Trig units, installers are responsible 
for setting the SIL appropriately based on the qualification of the 
position source used. Additionally, neither the Trig units nor the 
Dynon units use the SiRF IV position source.
    Request: Several commenters noted they purchased a NavWorx unit 
because the FAA originally listed them as eligible for the ADS-B Rebate 
Program. We interpret these comments as requesting we withdraw the 
NPRM.
    FAA Response: We have considered the comment. When the FAA rebate 
program Web site activated, it listed the ADS600-B as an eligible unit 
without distinction by part number. This was consistent with NavWorx's 
Web site, www.navworx.com, which advertised the ADS600-B for sale 
without distinguishing between the four different unique transceiver 
part numbers comprising that model series. P/N 200-0112 and P/N 200-
0113 are 2020 compliant, as these units contain a TSO-C145c approved 
Accord NexNav Mini internal GPS. P/N 200-0012 and P/N 200-0013, which 
are the subject of this AD, are not 2020 compliant because these units 
contain the uncertified SiRF IV GPS. Once the FAA rebate program office 
realized that the P/N 200-0012 and 200-0013 units were not eligible for 
the rebate, it changed the Web site to identify the ADS600-B model by 
P/N and listed only the P/N 200-0112 and P/N 200-0113 units as ADS600-B 
equipment selection options. While the FAA regrets any inconvenience 
these actions caused, what occurred with the rebate program Web site is 
not relevant to whether this AD is necessary to resolve the unsafe 
condition presented by the NavWorx units that improperly transmit a SIL 
of 3. We did not change the AD based on these comments.
    Request: One commenter states the proposed AD is contrary to the 
FAA's Compliance Philosophy because we did not cooperate with NavWorx 
or provide NavWorx a reasonable time to work on a corrective action. 
The commenter requests we withdraw the NPRM, unless we can collect 
technical data confirming a safety issue, in which case the commenter 
requests any AD be issued in a non-punitive manner.
    FAA Response: We disagree. The FAA's Compliance Philosophy applies 
to enforcement actions taken for regulatory violations. It does not 
apply to ADs, which are rulemaking actions taken to correct unsafe 
conditions found in aeronautical products. Notwithstanding, we also 
disagree with contentions that we failed to cooperate with NavWorx or 
provide NavWorx with a reasonable amount of time to correct the unsafe 
condition. The FAA clearly and repeatedly explained to NavWorx the 
safety concerns with its ADS-B units and requested that NavWorx 
voluntarily make the units TSO-compliant. NavWorx's failure to do so 
created an unsafe condition, for which AD action is necessary.
    Comment: An individual commenter stated that owners of experimental 
aircraft could simply remark the affected part with a new part number 
so that the AD wouldn't apply. The commenter reasoned that since the 
builder of an experimental aircraft is also the manufacturer, he could 
alter the part to a new design and mark it with a new part number.
    FAA Response: If the FAA identifies similar problems and determines 
that an unsafe condition exists on other part-numbered ADS-B products, 
we would take appropriate action to correct that unsafe condition. 
Also, simply changing the part number of the unit, without performing 
any other corrective action, will not correct the unsafe condition that 
we have determined exists in the unit. Since the unsafe condition 
remains in the unit, operating an aircraft with such a unit (that has 
only had the part number modified with no other corrective action 
taken) would therefore be a violation of 14 CFR 91.7(a), which states 
that no person may operate a civil aircraft unless it is in an 
airworthy condition. Any individual taking such action is subject to a 
civil penalty for a violation of the Federal Aviation Regulations.

F. Comments on the Negative Impact of the FAA's Actions

    Request: Several commenters stated that the AD would create 
confusion or skepticism in the flying community, and will prevent 
aircraft owners from adopting new technologies promoted by the FAA in 
the future. Some commenters stated that because of the AD people will 
quit flying; many others stated aircraft owners will choose to operate 
without ADS-B equipment. These commenters requested or implied that we 
withdraw the NPRM.

[[Page 25952]]

    FAA Response: We disagree. Although the FAA sympathizes with owners 
who became early adopters of this technology in good faith and 
unfortunately are now adversely affected by a situation not of their 
making, the potential for this action to create skepticism and distrust 
of the FAA among aircraft owners does not negate the need to correct 
the identified unsafe condition. The FAA's failure to take action to 
correct this unsafe condition could lead to accidents, which would also 
reasonably result in skepticism and distrust of the FAA, not only on 
the part of the flying community but of the public at large. We did not 
change the AD based on these comments.
    Request: A few commenters stated the FAA created this problem by 
suddenly and unilaterally changing the operational ADS-B rules to deny 
TIS-B data to aircraft broadcasting a SIL of 0. Two of these commenters 
noted that NavWorx initially submitted data to substantiate a SIL of 3, 
but the FAA refused to grant NavWorx TSO authorization unless the units 
broadcast a SIL of 0. The commenters request the FAA provide TIS-B data 
to all aircraft, regardless of SIL.
    FAA Response: We disagree. The FAA's changes to only provide TIS-B 
services to aircraft broadcasting a SIL greater than 0 were neither 
sudden nor unilateral. The changes were announced on March 31, 2015, 
and became effective in early 2016.\11\ However, they were initiated 
several years prior, as the result of an FAA study to determine a low 
risk, cost-effective, technically beneficial strategy for modification 
of the FAA TIS-B service. During this study, we consulted with the 
current manufacturers of ADS-B systems (both certified and uncertified) 
designed to use TIS-B information, including Accord Technologies, 
Dynon, FreeFlight Systems, Garmin, Honeywell, NavWorx, Rockwell 
Collins, and Trig. Like other manufacturers, NavWorx had the 
opportunity to make and obtain approval for appropriate design changes 
to its equipment so its customers could receive TIS-B traffic after the 
service change. NavWorx chose instead to only change the SIL setting 
from 0 to 3 in software without demonstrating the existing GPS position 
source's qualification to broadcast of a SIL of 3. Since that time, the 
FAA has been requesting NavWorx submit testing data supporting its 
conclusion that the SiRF IV GPS meets the performance requirements to 
broadcast a SIL of 3. NavWorx has not provided the FAA with this data.
---------------------------------------------------------------------------

    \11\ A copy of the FAA's announcement of its decision to make 
changes to the TIS-B service is available for review in Docket No. 
FAA-2016-9226.
---------------------------------------------------------------------------

    We also disagree with the contention that NavWorx initially 
submitted data to substantiate a SIL of 3. NavWorx's TSO-authorized 
design for its P/N 200-0012 and P/N 200-0013 ADS-B units has always 
identified the internal GPS source for those units as an uncertified 
SiRF IV GPS. The SiRF IV is not manufactured under an FAA TSO. The FAA 
approved this equipment and its installation to transmit a SIL of 0 
because that is what is required by RTCA Document DO-282B (the 
performance standard for TSO-C154c and the NavWorx units) and AC 20-
165B.
    The commenters' request to provide TIS-B data to all aircraft, 
regardless of SIL, would not correct the unsafe condition. We did not 
change the AD based on these comments.

G. Comments Beyond the Scope of the NPRM

    Request: A few commenters expressed disagreements with the ADS-B 
mandate. One commenter stated compliance with the rule would put him 
out of business, because he did not fly often enough to justify the 
cost. Another commenter requested the mandate not apply to aircraft 
operating under VFR in certain airspace. The third commenter stated 
that because of the mandate, the FAA is unable to manage the increase 
in ADS-B technology development or deal with the market.
    FAA Response: Comments about the 2020 mandate are beyond the scope 
of this AD. The rules mandating ADS-B Out usage, 14 CFR 91.225 and 
91.227, were promulgated through notice and comment rulemaking that 
began with an aviation rulemaking committee. An NPRM was issued in 2007 
(72 FR 56947, October 5, 2007) and the comment period was subsequently 
re-opened for an additional 30 days in 2008 (73 FR 57270, October 2, 
2008). The final rule published on May 28, 2010 (75 FR 30160) and 
considered approximately 240 comments from air carriers, manufacturers, 
associations, and individuals. All documentation of this rulemaking is 
available for review in Docket No. FAA-2007-29305.
    Request: Some commenters requested or implied they should be given 
until 2025 to comply with the AD because compliance with the ADS-B 
mandate is not required for air carriers until 2025.
    FAA Response: Comments about the 2020 mandate are beyond the scope 
of this AD. It appears the commenters are referring to Exemption No. 
12555, which is not a blanket 5-year extension for all air carriers. 
Exemption No. 12555 applies only to those operators who submit a 
request to use it and who comply with its conditions and limitations. 
Exemption No. 12555 allows the use of current ADS-B Out systems that 
are not fully compliant with the rule until fully compliant systems are 
installed on or before January 1, 2025. Documentation concerning 
Exemption No. 12555 is available for review in Docket No. FAA-2015-
0971.
    Comment: One commenter described a safety of flight issue he 
encountered with a Garmin ADS-B transponder that he has previously 
reported to the FAA.
    FAA Response: The comment is not relevant to whether this AD is 
necessary to correct the unsafe condition presented by the NavWorx ADS-
B units broadcasting a SIL of 0. We did not change the AD based on this 
comment.
    Comment: A few commenters expressed criticism of the FAA in 
general, without requesting specific changes to this AD.
    FAA Response: The comments are not relevant to whether this AD is 
necessary to correct the unsafe condition presented by the NavWorx ADS-
B units broadcasting a SIL of 0. We did not change the AD based on 
these comments.

FAA's Determination

    We have reviewed the relevant information, considered the comments 
received, and determined that an unsafe condition exists and is likely 
to exist or develop on other products of this same type design and that 
air safety and the public interest require adopting the AD requirements 
as proposed with the changes described previously. These changes are 
consistent with the intent of the proposals in the NPRM (81 FR 72552, 
October 20, 2016) and will not increase the economic burden on any 
operator nor increase the scope of the AD.

Related Service Information

    We reviewed NavWorx AFMS for ADS600-B as installed under STC No. 
SA11172SC, approved May 4, 2014; NavWorx Installation Manual for 
ADS600-B Part 23 AML STC 240-0021-00-07, Revision 7, dated May 4, 2014; 
and NavWorx STC Master Drawing List 240-0013-00, Revision 10, dated May 
29, 2014. This service information identifies the internal GPS position 
source for the NavWorx Model ADS600-B P/N 200-0012 and P/N 200-0013 as 
uncertified and not compliant with 14 CFR 91.225 and 91.227.

[[Page 25953]]

Costs of Compliance

    We estimate that this AD affects approximately 800 ADS-B units 
installed on various aircraft of U.S. registry. Operators may incur the 
following costs in order to comply with this AD based on an average 
labor rate of $85 per work-hour. Removing the ADS-B unit, disabling the 
ADS-B unit, or revising the software of the ADS-B unit will take about 
1 work-hour, for a total of $85 per aircraft. Coupling the ADS-B unit 
with an approved external GPS will take about 4 work-hours for a total 
of $340 per aircraft.

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.
    We are 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) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979);
    (3) Will not affect intrastate aviation in Alaska to the extent 
that it justifies making a regulatory distinction; and
    (4) 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.
    We prepared an economic evaluation of the estimated costs to comply 
with this AD and placed it in the AD docket.

List of Subjects in 14 CFR Part 39

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

Adoption of 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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive (AD):

2017-11-11 NavWorx, Inc.: Amendment 39-18910; Docket No. FAA-2016-
9226; Directorate Identifier 2016-SW-065-AD.

(a) Applicability

    This AD applies to the following NavWorx, Inc., Automatic 
Dependent Surveillance-Broadcast (ADS-B) Universal Access 
Transceiver units (unit) installed on aircraft certificated in any 
category, including experimental:
    (1) Model ADS600-B part number (P/N) 200-0012;
    (2) Model ADS600-B P/N 200-0013; and
    (3) Model ADS600-EXP P/N 200-8013.

(b) Unsafe Condition

    This AD defines the unsafe condition as an ADS-B unit 
incorrectly broadcasting a Source Integrity Level (SIL) of 3 instead 
of its authorized SIL of 0. This condition could result in the unit 
communicating unreliable position information to Air Traffic Control 
and nearby aircraft and a subsequent aircraft collision.

(c) Effective Date

    This AD becomes effective July 11, 2017.

(d) Compliance

    You are responsible for performing each action required by this 
AD within the specified compliance time unless it has already been 
accomplished prior to that time.

(e) Required Actions

    (1) Within 6 months, comply with either paragraph (e)(1)(i), 
(ii), (iii), or (iv) of this AD:
    (i) Remove the ADS-B unit.
    (ii) Disable and prohibit use of the ADS-B unit as follows:
    (A) Pull and secure the circuit breaker and disconnect the 
internal GPS antenna connector from the ADS-B unit and secure.
    (B) Install a placard in view of the pilot that states ``USING 
THE ADS-B SYSTEM IS PROHIBITED.''
    (C) Revise the Limitations section of the Aircraft Flight Manual 
supplement (AFMS) by inserting a copy of this AD or by making pen-
and-ink changes to add the following: ``USING THE ADS-B SYSTEM IS 
PROHIBITED.''
    (iii) Revise the software so the ADS-B unit broadcasts a SIL of 
0.
    (iv) Couple the ADS-B unit with an approved external GPS as 
follows:
    (A) Interface the ADS-B unit with an Accord NexNav mini LRU GPS 
Receiver P/N 21000.
    (B) Revise the Limitations section of the AFMS by inserting a 
copy of this AD or by making pen-and-ink changes to add the 
following: ``OPERATION USING THE INTERNAL POSITION SOURCE IS 
PROHIBITED. USE OF THE ACCORD NEXNAV MINI P/N 21000 EXTERNAL 
POSITION SOURCE IS REQUIRED.''
    (2) After the effective date of this AD, do not install an ADS-B 
unit Model ADS600-B P/N 200-0012, Model ADS600-B P/N 200-0013, or 
Model ADS600-EXP P/N 200-8013 on any aircraft unless you have 
complied with the requirements of paragraph (e)(1)(ii), (e)(1)(iii), 
or (e)(1)(iv) of this AD.

(f) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Fort Worth Aircraft Certification Office, FAA, 
may approve AMOCs for this AD. Send your proposal to: Kyle Cobble, 
Aviation Safety Engineer, Fort Worth Aircraft Certification Office, 
Rotorcraft Directorate, FAA, 10101 Hillwood Pkwy, Fort Worth, TX 
76177, telephone (817) 222-5172, email kyle.cobble@faa.gov; or 
Michael Heusser, Program Manager, Continued Operational Safety 
Branch, Fort Worth Aircraft Certification Office, Rotorcraft 
Directorate, 10101 Hillwood Pkwy, Fort Worth, TX 76177, telephone 
(817) 222-5038, email michael.a.heusser@faa.gov.
    (2) For operations conducted under a 14 CFR part 119 operating 
certificate or under 14 CFR part 91, subpart K, we suggest that you 
notify your principal inspector, or lacking a principal inspector, 
the manager of the local flight standards district office or 
certificate holding district office before operating any aircraft 
complying with this AD through an AMOC.

(g) Additional Information

    NavWorx Airplane Flight Manual Supplement for ADS600-B as 
installed under Supplemental Type Certificate (STC) No. SA11172SC, 
approved May 4, 2014; NavWorx Installation Manual for ADS600-B Part 
23 AML STC 240-0021-00-07, Revision 7, dated May 4, 2014; and 
NavWorx STC Master Drawing List 240-0013-00, Revision 10, dated May 
29, 2014, which are not incorporated by reference, contain 
additional information about the subject of this AD. For service 
information identified in this AD, contact NavWorx Inc.; telephone 
(888) 628-9679; email: support@navworx.com or at www.navworx.com. 
You may review a copy of this information at the FAA, Office of the 
Regional Counsel, Southwest Region, 10101 Hillwood Pkwy, Room 6N-
321, Fort Worth, TX 76177.

(h) Subject

    Joint Aircraft Service Component (JASC) Code: 3452, ATC 
Transponder System.

[[Page 25954]]

    Issued in Fort Worth, Texas, on May 30, 2017.
Lance T. Gant,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 2017-11625 Filed 6-5-17; 8:45 am]
 BILLING CODE 4910-13-P