8900.1 CHG 349



Indicates new/changed information.

Section 15  Part 135 Transponder Requirements

4-14-15-1    PURPOSE. This section provides guidance to Maintenance and Avionics aviation safety inspectors (ASI) concerning the requirement for an aircraft to be equipped with a transponder meeting the standards of Technical Standard Order (TSO) TSO-C112 (Mode S) when operated under Title 14 of the Code of Federal Regulations (14 CFR) part 135. It includes a job aid to assist you in determining compliance with the requirements of part 135, § 135.143(c). The job aid incorporates rule provisions and Federal Aviation Administration (FAA) policy stated in public notices.

4-14-15-3    BACKGROUND. Section 135.143(c) prohibits the installation of non-Mode S transponders into aircraft operated under part 135 and contains provisions for the continued use of transponders meeting the standards of TSO‑C74b or TSO-C74c (Mode C). This rule was issued in February 1987 with an implementation date of January 1992.

A.    The 1996 Notice of Proposed Rulemaking (NPRM). When this requirement was issued, operators contended that it was premature since infrastructure had not yet been implemented to provide a safety benefit. In response, in May 1996, we (the FAA), issued an NPRM to evaluate rescinding the requirement. We granted exemptions from § 135.143(c) to operators between January 1992 and October 2005.

B.    Withdrawal of the 1996 NPRM. In October 2005, we issued a public notice that our evaluation had determined that technology and infrastructure had advanced to the point where the provisions of § 135.143(c) resulted in a safety benefit. We withdrew our 1996 NPRM and established an effective date of March 2007, after which exemptions would no longer be reissued.

C.    Exemptions. Operators of aircraft that had been operating under exemption expressed concerns that aircraft with functional Mode C transponders would need to have those transponders replaced or cease operation under part 135 in March 2007. In response to this concern, in February 2006, we issued public notice that aircraft which had operated under exemption from § 135.143(c) could continue to be operated under part 135 with their existing transponder until that unit could no longer be maintained.

4-14-15-5    DISCUSSION.

A.    Transponder Requirement. The provisions of § 135.143(c) apply only to aircraft equipped with a transponder. An aircraft without a transponder may be placed on an operator’s part 135 certificate and operated in accordance with 14 CFR part 91, § 91.215. These aircraft may not operate in certain airspace without special authorization from air traffic control (ATC).

B.    Conditional Use of ATC Radar Beacon System (ATCRBS) Transponder. The March 2007 Federal Register (FR) notice provided a provision for aircraft to operate under part 135 with a Mode C transponder installed after January 1, 1992. The provision applies to an aircraft with a transponder not meeting the requirements of TSO-C112, which was installed prior to March 1, 2007 and had been operated under an exemption to § 135.143(c) at some time in the past.

NOTE:  The exemption was aircraft specific and could include operation of the aircraft by another operator under part 135.

C.    Multiple Transponders. Aircraft operated under part 135 meet the requirements of § 135.143(c) when they are equipped with a single Mode S transponder or are compliant based on the provision described above. Additional transponders are not required to also meet the provision of § 135.143(c) (i.e., they may be Mode C rather than Mode S transponders).

D.    Proving Transponder Date. It may be difficult for an operator to prove the exact date a transponder was manufactured or installed. Reasonable proof is adequate.

E.      Job Aid. The Flight Standards Service (AFS), Aircraft Maintenance Division (AFS-300), Avionics Branch (AFS-360) has developed a job aid (see Figure 4-71, 14 CFR Part 135 Transponder Requirements) to assist an ASI in determining compliance with § 135.143(c).

4-14-15-7    ACTION. You should use this job aid (Figure 4-71) to perform surveillance or determine eligibility of an aircraft for operation under part 135.


A.    References:

·    FR Volume 52, Number 22 (February 3, 1987). Air Traffic Control Radar Beacon System and Mode S Transponder Requirements in the National Airspace System (FR Doc No: 1987-3380).

·    FR Volume 61, Number 101 (May 23, 1996). Air Traffic Control Radar Beacon System and Mode S Transponder Requirements in the National Airspace System (FR Doc No: 1996-26036).

·    FR Volume 70, Number 194 (October 7, 2005). Mode S Transponder Requirements in the National Airspace System (FR Doc No: 2005-58966).

·    FR Volume 71, Number 31 (February 15, 2006). Mode S Transponder Requirements in the National Airspace System (FR Doc No: 2006-7892).

B.    Forms. None.

C.    Job Aids. Figure 4-71, 14 CFR Part 135 Transponder Requirements.

Figure 4-71.    14 CFR Part 135 Transponder Requirements

Figure 4-71. 14 CFR Part 135 Transponder Requirements

RESERVED. Paragraphs 4-14-15-11 through 4-14-15-25.