Federal Aviation Administration (FAA) guidance requires that components, systems, or appliances installed on an aircraft under an STC be included in the MMEL before approval for inclusion in an operator’s MEL is allowed. Before inclusion in the MMEL, the Flight Operations Evaluation Board (FOEB) must evaluate an STC for such relief. The STC holder/applicant should request an FOEB evaluation as early as possible during the certification process. The STC applicant or aircraft operator involved in the certification of an STC should submit a request for MMEL relief in accordance with the FOEB MMEL Agenda Coordination Process. Refer to MMEL Policy Letter 109 for additional information.
In accordance with existing guidance, operators seeking to obtain MEL relief for components installed through an STC would either contact their principal inspectors (PIs) or the STC holder, or contact the Aircraft Evaluation Group (AEG) directly. Subsequently, upon application, the FOEB would then evaluate the STC and determine if MMEL/MEL relief is suitable. If relief is granted, the FOEB would revise the MMEL by listing that specific STC in the appropriate section. Once the STC is listed in the MMEL, operators may then revise their MELs to include that specific STC and exercise relief for that component, upon MEL approval from the principal operations inspector (POI).
Additionally, an aircraft manufacturer, operator, STC holder, or Industry Focal may initiate a subsequent request for a revision to an existing MMEL, in order to evaluate and incorporate STC relief.
An aircraft operator that seeks MEL relief for a new item installed on its aircraft not currently listed in the MMEL may also contact the STC holder for MMEL relief support. The STC holder or operator who seeks MMEL relief will contact the responsible AEG to begin the FOEB process.

The Automatic Dependent Surveillance – Broadcast (ADS-B) Out rule takes effect on January 1,
2020. After this date, and unless otherwise authorized by ATC, no person may operate an
aircraft in Class A airspace or other airspace as listed in Title 14 Code ofFederal Regulations (14
CFR) part 91.225, unless the aircraft has equipment installed that meets the performance
requirements in TSO-C166b or TSO-C154c. The ADS-BOut equipment performance
requirement listed in 14 CFR 91.227(c)(1)(ii) states the aircraft’s Navigation Accuracy Category
for Velocity (NACv) must be less than 10 meters per second.
Guidance from AC 20-165B, Airworthiness Approval of Automatic Dependent Surveillance Broadcast
OUT (dated 1217/15), paragraph 3.3.3.7.3, states: A NACv = 3 or NACv = 4 should
not be set based on GNSS velocity accuracy unless you can demonstrate to the FAA that the
velocity accuracy actually meets the requirement. Furthermore, in Appendix B, paragraph
B.4.14.3, NACV = 3 or 4, states: No standard for performance has been developed to support
NACv = 3 or NACV = 4. A NACv = 3 or NACv = 4 should not be set based on GNSS velocity
accuracy unless you can demonstrate to the FAA that the error contributions have been
adequately modeled to meet those levels of performance.