26036 Federal Register /Vol. 61, No. 101/ Thursday, May 23, 1996/ Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 121 and 135

[Docket No. 28586; Notice No. 96–5]

RIN 2120–AE81

Air Traffic Control Radar Beacon

System and Mode S Transponder

Requirements in the National Airspace

System

AGENCY: Federal Aviation

Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This notice proposes to

rescind the Mode S transponder

requirement for all aircraft operations

under part 135 and certain aircraft

operations under part 121 of the Federal

Aviation Regulations (14 CFR parts 121

and 135). For part 121 operators, this

amendment would affect only those

aircraft not required to have Traffic

Alert and Collision Avoidance System II

(TCAS II). The initial mandate for Mode

S equipage was based on the

assumption that Mode S would provide

the sole method for air traffic control

data link. The FAA’s revised strategy of

multiple air-ground data links managed

through an Aeronautical

Telecommunications net work removes

this requirement. Further, operational

experience with the Mode S ground

sensors has shown that most

surveillance enhancements can be

achieved by the Mode S ground sensors

with the present mixed population of

airborne transponders. In addition, the

use of Mode S transponders for aircraft,

other than those required to have TCAS

II, does not offer, nor is it expected to

offer, any significant safety advantage in

the current or future airspace

environment. Therefore, requiring all

aircraft at this time to have Mode S

transponders when those aircraft are not

required to have TCAS II is not essential

for a safe and efficient National

Airspace System. In the current airspace

operational environment, the public

interest does not require that all

transponders newly installed in certain

aircraft operated under part 121 and all

aircraft operated under part 135 after

January 1, 1992, be Mode S

transponders.

DATES: Comments must be received on

or before July 22, 1996.

ADDRESSES: Comments on this NPRM

should be mailed, in triplicate to:

Federal Aviation Administration, Office

of the Chief Counsel, Attention: Rules

Docket (AGC–200), Docket No. 28537,

800 Independence Avenue, SW.,

Washington, DC 20591. Comments may

also be sent electronically to the Rules

Docket by using the following Internet

address: nprmcmt@mail.hq.faa.gov.

Comments must be marked Docket No.

28586. Comments may be examined in

the Rules Docket in Room 915G on

weekdays between 8:30 a.m. and 5 p.m.,

except on Federal holidays.

FOR FURTHER INFORMATION CONTACT: Mr.

Daniel V. Meier Jr., Air Carrier

Operations Branch (AFS–220), Air

Transportation Division, Federal

Aviation Administration, 800

Independence Avenue SW.,

Washington, DC 20591; telephone (202)

267–3749.

SUPPLEMENTARY INFORMATION:

Comments Invited

Any person may obtain a copy of this

NPRM by submitting a request to the

Federal Aviation Administration, Office

of Rulemaking, 800 Independence

Avenue SW., Washington, DC 20591, or

by calling (202) 267–9677.

Communications must identify the

notice number of this NPRM. Persons

interested in being placed on a mailing

list for future FAA NPRM’s should

request a copy of Advisory Circular No.

11–2A, Notice of Proposed Rulemaking

Distribution System, which describes

application procedures.

An electronic copy of this document

may be downloaded using a modem and

suitable communications software from

the FAA regulations section of the

Fedworld electronic bulletin board

service (telephone: 703–321–3339) or

the Federal Register’s electronic

bulletin board service (telephone 202–

512–1661). Internet users may reach the

FAA’s web page at http://www.faa.gov

or the Federal Register’s webpage at

http://www.access.gpo.gov/suldocs for

access to recently published rulemaking

documents.

Availability of NPRM’s

Any person may obtain a copy of this

NRM by submitting a request to the

Federal Aviation Administration, Office

of Rulemaking, 800 Independence

Avenue SW., Washington, DC 20591, or

by calling (202) 267–9677.

Communications must identify the

notice number of this NPRM.

Persons interested in being placed on

the mailing list for future NPRM’s

should request from the above office a

copy of Advisory Circular No. 11–2A,

Notice of Proposed Distribution System,

which describes the application

procedure.

History

In 1982, the FAA announced a

comprehensive plan to modernize and

improve air traffic control and airway

facilities. One part of the comprehensive

plan included introducing the Mode S

system. In an advance notice of

proposed rulemaking, the FAA stated

that improved surveillance reliability

and accuracy would be a central

objective of the Mode S system (48 FR

48364, October 18, 1983). Mode S

transponders were considered an

integral link in the system, furnishing

accurate, reliable, and positive air traffic

control information on aircraft identity,

position, and altitude. The plan

envisioned that all groundbased

secondary radars would be replaced by

Mode S stations, and that Mode S would

provide the exclusive medium for an

air/ground data link. At that time, the

first 137 Mode S ground sensors were

expected to be on-line by 1991.

Therefore, the Mode S transponder

requirement was promulgated with a

final rule published February 3, 1987

(Amendment Nos. 121–190 and 135–22;

52 FR 3380). This final rule provided

that any transponder newly installed in

aircraft used for operations under parts

121 and 135 of Title 14, Code of Federal

Regulations (14 CFR 121 and 135),

before January 1, 1992, could be a Mode

A transponder provided the transponder

was manufactured prior to January 1,

1990; only Mode S transponders could

be newly installed in these aircraft after

January 1, 1992.

Mode A and Mode S Transponders

The two kinds of aircraft equipment

addressed by this rulemaking are the

Mode A and the Mode S transponders.

They are the airborne portion of the

secondary radar system, which is not a

true radar system but rather an

interrogate/respond system used to

establish aircraft position and identity.

The Mode A transponder consists of

a radio transceiver that responds to a

coded train of pulses from ground

sensors (known as Air Traffic Control

Radar Beacon Interrogators (ATCBI)).

The Mode A transponder response

encodes one of 4,096 discrete codes (set

by the pilot) in response to a Mode A

interrogation from the ground sensor.

The ground sensor receives the reply

message, and processors extract the

aircraft’s position and identity for

display on the controller’s radar scope.

An enhanced transponder is capable of

responding to Mode C interrogations

from the ground station by reporting the

aircraft’s altitude derived from a

suitable encoding altimeter.
Federal Register /Vol. 61, No. 101/ Thursday, May 23, 1996/ Proposed Rules 26037

The Mode S transponder is an

advanced version of the Mode A

transponder which responds to

conventional Mode A and Mode C

interrogations, but it is also capable of

responding to a Mode S interrogation

with a unique code based on the

aircraft’s tail number. When used in

conjunction with Mode S ground

sensors, a system of nearly interferencefree radar transmission and reception

will exist. This system provides for

improved target information to be

display on the controller’s radar screen

and enables the various air traffic

control computers (ATC) to detect

conflict and control aircraft flow. In

addition, the Mode S ground station

recognizes a conventional Mode A

transponder and reverts to conventional

ATCBI operation for that aircraft.

The Mode S System

The Mode S system was designed to

rectify limitations in the current radar

system. The limitations include

synchronous garble, loss of target and

altitude integrity, and restrictions on

traffic management caused by the

limited number of discrete beacon

codes. Of the two components in the

Mode S system (i.e., the ground sensor

and the transponder), the ground sensor

provides most of the capability to

ameliorate these limitations.

Synchronous garble occurs when the

ground sensor interrogating two aircraft

near one another cannot distinguish

between their respective replies. In this

situation, the data cannot be

reconstructed; the ATC computer will

either not display information or

display erroneous information on the air

traffic controller radar scope. When this

condition can occur any time aircraft are

in proximity, it is most likely to hamper

air traffic services in areas of high

density aircraft activity such as Classes

B and C airspace areas. Improved

processing capabilities found in the

latest monopulse secondary radars are

able to resolve many garble situations

without Mode S transponder equipage

by the aircraft. Operational experience

with the currently deployed Mode S

systems indicates that the garble

resolution provided with the current

transponder population is sufficient to

provide assured separation using

today’s separation standards.

Target and altitude integrity expresses

the ability of the radar system to

distinguish between transmissions

received from two different aircraft. The

ATCBI secondary radar system

transmits interrogation signals, and all

transponder-equipped aircraft receiving

the signal reply with a distinct code

and, if so equipped, report the aircraft’s

altitude. As described earlier, the ability

of the current system to distinguish

between two signals is affected by the

proximity of the aircraft to each other.

Terrain, signal strength of the aircraft

transponder equipment, and

environmental factors can also derogate

the ability of the ground sensor to

determine the position and altitude of

an aircraft.

Azimuth accuracy is improved with

the Mode S system. To illustrate, when

two aircraft are equal distances from a

sensor in the existing system, they must

be at least .23° of azimuth apart before

both targets are displayed. With the

Mode S system, those same aircraft need

only be apart by .06° of azimuth to be

displayed. A 1976 FAA-sponsored study

postulated that a homogeneous Mode S

environment (Mode S ground sensors

and transponders) would increase

integrity to more than 99 percent.

Recent FAA tests and operational

experience with the Mode S ground

sensors have verified these figures.

If the number of aircraft operating in

the National Airspace System continues

to increase, the number of codes needed

may eventually exceed the current limit

of 4,096 discrete codes. Controllers

assign these discrete codes, used to

track aircraft position and altitude, to

aircraft receiving air traffic services. The

unique code assigned by the Mode S

reduces the controller’s workload and

computer processing burden, allowing

positive identification of an aircraft as it

passes from one air traffic facility to

another, and as data link messages are

associated with surveillance targets.

However, without a nationwide network

of Mode S ground sensors in place and

enhanced ATC computers with

complementary software, these

productivity benefits cannot be fully

achieved.

Although the Mode S system

improves accuracy in the surveillance of

aircraft position and reduces

interference in identify reports

transmitted to air traffic controllers,

which allows for clear surveillance of

aircraft that are minimally separated,

studies with the Precision Runway

Monitor show that a multitude of

procedural, pilot training, and other

issues must be addressed before a

relaxation in aircraft separation

standards may be approved. Therefore

the capacity benefits envisioned

initially from Mode S are not primarily

dependent on improved surveillance

capability.

In addition to surveillance, the initial

strategy for Mode S deployment

includes a data-link capability. All

secondary radar ground stations were to

be converted to Mode S, which was to

be the sole data link used for critical

ATC messages. The FAA has adopted a

new data link strategy with two

principle thrusts: (1) a second FAA data

link will be deployed as part of the nextgeneration air-ground VHF radios; and

(2) private data link services will be

considered if they meet FAA

performance requirements. The message

itself will be routed through an

Aeronautical Telecommunications

Network (ATN), which will

automatically select the best air-ground

media based on the nature of the

message. This strategy provides a much

more flexible and market-driven

approach, which allows the FAA to

work with the aviation community to

use the best available evolving

technology.

The new data link strategy means that

nationwide Mode S ground station

deployment is no longer required to

establish the air-ground link. Further,

mandatory Mode S transponder

equipage by aircraft is not required to

achieve widespread data link equipage

in aircraft. The number of Mode S

ground stations will now be determined

by surveillance requirements and the

marginal benefit of the increased airground data link capability.

Mode S capability is an integral part

of the Traffic Alert and Collision

Avoidance System II (TCAS II) required

by § 121.356 14 CFR for certain aircraft

operating under part 121. This

regulation requires such aircraft having

a passenger seating configuration of

more than 30 seats to be equipped with

an approved TCAS II and appropriate

Mode S transponder by December 30,

1993. Used with TCAS II, Mode S

provides air-to-air data exchange

between TCAS-equipped aircraft

making coordinated, complementary

resolution advisories (recommended

escape maneuvers) possible. A TCAS II

system is rendered ineffective unless a

Mode S transponder is installed with

the TCAS II component.

Traffic Alert and Collision Avoidance

System I (TCAS I) does not require data

from Mode S transponders to function.

This system is intended for use by

aircraft with passenger seating

configuration between 10 and 30 seats

that are operated under parts 121 and

135. TCAS I provides proximity

warning only to assist a pilot in the

visual acquisition of intruder aircraft.

The FAA has determined that the

requirement to install Mode S

transponders after January 1, 1992, in

aircraft not required to be equipped

with TCAS II exceeds the requirements

of the present and immediate future for

a safe and efficient National Airspace

System. Studies and analysis are being
26038 Federal Register /Vol. 61, No. 101/ Thursday, May 23, 1996/ Proposed Rules

conducted on advanced methods of

aircraft separation to support the FAA’s

goal of ‘‘free flight.’’ Free flight is an

operational vision that will allow

aircraft to cooperatively plan and

execute their optimal flight paths with

minimal interference from ground-based

controllers. The overall infrastructure

improvements to the airspace system

(including surveillance) required to

achieve operational benefits are being

defined, and public comment will be

sought on the benefits, procedures, and

any new avionics requirements before

they are implemented. The FAA further

invites comment on whether future

equipage of Mode S transponders

should be mandatory for certain areas of

operation.

Except for aircraft equipped with

TCAS II, the presence of Mode S

transponder capability on part 135

aircraft would not enhance the safety of

flight in today’s airspace environment. If

the demand for air traffic services

continues to increase, A mode S

transponder may be necessary for

aircraft operating under parts 121 and

135 to increase efficiency in some areas

of the national airspace system.

The Proposed Rule

The FAA proposes to rescind the

Mode S transponder requirement for

aircraft operating under part 135 of the

FAR and those aircraft operating under

part 121 that are not required to have

TCAS II.

Paperwork Reduction Act

This proposed rulmaking would

rescind an agency regulation and would

not change any reporting requirements.

Therefore, no review or approval under

the Paperwork Reduction Act is

required.

Regulatory Evaluation Summary

The FAA has determined that this

rulemaking is not a ‘‘significant

regulatory action’’ as defined by

Executive Order 12866 (Regulatory

Planning and Review). The anticipated

costs and benefits associated with this

NPRM are summarized below. (A

detailed discussion of costs and benefits

is contained in the full regulatory

evaluation contained in the docket for

this NPRM.)

Overview

Although this proposal applies to

operators under parts 121 and 135, the

benefits and costs sections of this

evaluation will only focus on part 135

operators. Of the part 121 operators,

only those not required to install TCAS

II would be affected by this proposed

rule. The FAA is not able, at this time,

to determine the number of these

operators because there is no

information readily available. For this

reason, only the potential impact on

part 135 operators will be analyzed in

this evaluation. The FAA solicits

comments from the aviation community

as to the number of part 121 operators

not required to have TCAS II.

This proposed Mode S rescission

would apply to all part 135 operators

regardless of what kind of transponder

(remote-mounted or panel-mounted)

they would purchase. For this

evaluation, however, the FAA will

consider only those part 135 operators

who would install remote-mounted

transponders. When the FAA estimated

the benefits of the Mode S rescission for

part 91 operators, it counted all of the

panel mounted Mode S transponders

since those transponders are

predominantly installed in part 91

aircraft. The FAA has since learned that

some panel-mounted transponders are

also installed in part 135 aircraft,

especially those with less than 10 seats.

Thus, the FAA has not estimated the

number of panel-mounted transponders

that are being operated in part 135

aircraft for this proposed rule. The FAA

has not estimated this number for two

reasons. First, the proportion of new

panel-mounted transponders that are

installed in part 135 aircraft is very

difficult to estimate. Second, even if that

proportion could be estimated, it could

not be used to calculate the benefits for

the proposed rule since they were

already used to calculate the benefits of

rescinding the Mode S requirement for

part 91 operators. Consequently, the

benefits of the proposed rule are

underestimated.

Benefits

The benefits of this proposed rule are

the cost-savings to aircraft operators

who would be allowed to purchase

Mode A transponders instead of Mode

2 transponders. The FAA estimates the

cost-savings to be approximately $10

million over the next 10 years. The

present value of these cost-savings

would be $7 million (discounted, 7

percent, 1992 dollars).

To estimate the potential cost-savings

of this proposed rule, the FAA

estimated the number of remotemounted transponders that would be

installed in part 135 aircraft with 10 to

29 seats. The FAA estimates that 780

such aircraft are being operated in the

United States. These aircraft make up

the vast majority of aircraft that would

be affected by the proposed rule to

rescind the Mode S requirements.

The potential benefits would be the

cost-savings that these operators would

realize when they replace an existing

remote-mounted Mode A transponder.

The proposed rule would allow them to

purchase and install another remotemounted Mode A transponder instead of

a new remote-mounted Mode S

transponder. To estimate these potential

benefits, the FAA surveyed several

transponder manufacturers, fixed-based

operators, and regional airlines in an

effort to ascertain information on the

frequency of Mode A transponder

replacement. According to these

industry sources, a part 135 operator

would purchase a new transponder, on

average, once every 10 years. Thus, over

the next 10 years, on average, each part

135 operator would have purchased a

new Mode S transponder.

Currently, an estimated 780 part 135

aircraft would potentially be affected by

this proposed rule. Therefore, the

population of part 135 aircraft that

would be affected by this proposed rule

annually would be approximately 78

(780/10). This translates into

approximately 78 remote-mounted

Mode S transponders that would be sold

annually over the next 10 years.

The difference in price (including

installation) between the average

remote-mounted Mode A transponder

and the average remote-mounted Mode

S transponder is $12,800. This price

represents the average cost-savings that

a part 135 operator could realize as a

result of the proposed rule to rescind

Mode S requirements. Multiplying this

cost-savings estimate of $12,800 by the

number of transponders expected to be

sold over the next 10 years would result

in total potential benefits of $10 million

(or $7 million discounted).

Costs

The proposed rule would impose an

estimated cost of $910,000 (or $640,000

discounted) over the next 10 years. This

cost impact would only affect Mode S

manufacturers and would be the

reduction in profit earned from Mode S

sales. (Sales from Mode S exports would

not be affected by the NPRM.) This

proposed rule would not impose costs

in the form of either reduced aviation

safety or operational efficiency. The

expected aviation safety and operational

efficiency benefits of the Mode S rule

have not been realized because the

ground sensors were never installed and

tested. This assessment is based on the

following analysis of each of the

potential cost components.

Aviation Safety and Operational

Efficiency

Rescinding the Mode S requirement

would not decrease operational

efficiency in the air traffic control
Federal Register /Vol. 61, No. 101/ Thursday, May 23, 1996/ Proposed Rules 26039

system. In addition, the rescission

would not decrease safety to aircraft

operators and the flying public. While

areas of high density air traffic may

benefit from the improved target and

altitude integrity of the Mode S system,

the benefit will derive primarily from

the ground sensor component; the

limited benefit expected from the

transponder component by itself would

appear not to warrant the current Mode

S transponder requirement for part 135

aircraft. Since those potential benefits

have never been realized, neither

aviation safety nor operational

efficiency would decrease as a result of

this proposed rule.

Mode S Transponder Manufacturers

Another potential cost impact of this

proposed rule would be the additional

costs incurred by manufacturers of

Mode S transponders in lost profits. The

manufacturers of remote-mounted Mode

S transponders have made investments

in designing and developing such

products. The potential costs to those

manufactures would be: (1) The initial

investment to develop Mode S

transponders for part 135 aircraft and (2)

the potential lost profit on each remotemounted Mode S transponder sold in

the future. In terms of the initial

development cost, there would be no

loss due to this proposed rule. These

manufacturers have incurred costs for

developing remote-mounted Mode S

transponders in response to the Mode S

rule. Such costs, which are in excess of

$4 million (undiscounted), are sunk and

cannot be considered as part of the

proposed rule. Once an investment is

made and cannot be altered, it is called

a sunk cost. For this reason, sunk costs

are not considered when evaluating the

costs of regulatory actions.

In terms of profits on Mode S

transponders sold in the future, the

proposed rule would impose a cost. The

proposed Mode S rescission would

decrease the demand for remotemounted Mode S transponders by part

135 operators; hence, the cost to

manufacturers would be lost profit. This

lost profit would represent the

difference in profit earned from sales of

Mode A rather than Mode S

transponders over the next 10 years.

Due to the proprietary nature of such

information, the FAA was unable to

ascertain specific rates of profit that

manufacturers earn on the sale of Mode

S transponders. However, the FAA did

receive information that indicates the

profit earned on the sale of Mode A

transponders is 10 percent. The FAA

contends that this rate is also a fair

representation for Mode S transponders

as well, since they are similar products

installed in the same type of aircraft and

purchased by the same part 135

operators.

The amount of potential lost profit

(LP) is the amount of revenue (R) that

would be earned from the sale of Mode

S transponders (instead of Mode A

transponders) less the cost (C) of

manufacturing Mode S transponders

(instead of Mode A transponders). The

revenue is equivalent to the cost-savings

incurred by aircraft operators, which is

$7 million (discounted) over the next 10

years. The cost of manufacturing Mode

S tranponders can be estimated based

on the relationship between the rate of

profit, the revenue and the

manufacturing cost. In general terms,

this relationship can be represented as

R=C×P. In this instance, revenue is $7

million and profit is 1.10. To estimate

the potential lost profit, the following

calculation is made:

R=C×P=$7M

C=$7M/1.10=$6.36M

LP=R¥C=$640,000

As shown in the above calculation,

the estimate of $640,000 represents the

present value lost profit from selling

Mode A instead of Mode S transponders

over the next 10 years. The FAA

recognizes that there is some

uncertainty in the accuracy of the rate

of profit on transponder sales for

manufacturers. This uncertainty is due,

in large part, to the fact that the rate of

profit varies among manufacturers of

remote-mounted Mode S transponders.

As the result of this uncertainty, the

FAA solicits comments from

manufacturers of remote-mounted Mode

S transponders as to the accuracy of the

10 percent rate of profit estimate.

Conclusion

The potential cost-relieving benefits

of this proposed rule are estimated to be

$7 million (discounted). The potential

costs are estimated to be $640,000

(discounted). Based on this assessment,

the FAA has determined that this

proposed rule is cost-beneficial.

Initial Regulatory Flexibility

Determination

The Regulatory Flexibility Act of 1980

(RFA) was enacted by Congress to

ensure that small entities are not

unnecessarily burdened by government

regulations. The RFA requires agencies

to review rules that may have a

‘‘significant economic impact on a

substantial number of small entities.’’

According to the FAA’s Regulatory

Flexibility Criteria and Guidance

(2100.14A), a substantial number of

small entities means a number that is

not less than 11 and that is more than

one third of the small entities subject to

the proposed rule. The small entities

that this proposed rule would

potentially affect are aircraft flight

instrument manufacturers that produce

no more than 250 units annually. The

FAA has identified the three

manufacturers that produce remote

mounted Mode S transponders. On

average, these three manufacturers

combined sell approximately 2,200

transponders annually. Each of the three

manufacturers sell, on average,

approximately 730 (2,200/3) Mode S

transponders annually. Since 730

exceeds the annual size threshold of

250, none of the U.S. Mode S

transponder manufacturers are

considered to be small. Thus, this

proposed rule would not impose a

significant economic impact on a

substantial number of small entities. For

this reason, a regulatory flexibility

analysis is not required.

International Trade Impact Assessment

The Office of Management and Budget

directs agencies to assess the effects of

regulatory changes on international

trade. This proposed rule would not

have a competitive trade disadvantage

on foreign companies that sell foreign

aviation products or services in the

United States. This proposed rule also

would not have a competitive trade

disadvantage on domestic companies

that sell U.S. products or services in

foreign countries. This assessment is

based on the belief that the number and

type of transponders sold to foreign

operators by U.S. manufacturers would

not change as a result of this proposed

rescission. The FAA was not able to

identify any foreign manufacturers that

sell transponders in the United States.

Based on this information, the FAA

contends that there would be no impact

on them. However, the FAA solicits any

comments on the international trade

impact.

Federalism Implications

The proposed rescission of the

regulation herein would 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 proposal

would not have sufficient federalism

implications to warrant the preparation

of a Federalism Assessment.

Conclusion

For the reasons discussed in this

preamble and based on the findings in
26040 Federal Register /Vol. 61, No. 101/ Thursday, May 23, 1996/ Proposed Rules

the Regulatory Flexibility Determination

and the International Trade Impact

Analysis, the FAA has determined that

the proposed rescission of this

regulation is not significant under

Executive Order 12866. In addition,the

FAA certifies that this rule will not have

a significant economic impact on a

substantial number of small entities

under the criteria of the Regulatory

Flexibility Act. This proposal is

considered not significant under DOT

Regulatory Policies and Procedures (44

FR 111034; February 26, 1979). A

regulatory evaluation of the regulation,

including a Regulatory Flexibility

Determination, and International Trade

Impact Analysis, has been placed in the

docket. A copy may be obtained by

contacting the person identified under

FOR FURTHER INFORMATION CONTACT.

List of Subjects

14 CFR Part 121

Air carriers, Aircraft, Aviation safety,

Charter flights, Transportation.

14 CFR Part 135

Air taxis, Aircraft, Aviation safety.

The Proposed Amendment

In consideration of the foregoing, the

Federal Aviation Administration

proposes to amend parts 121 and 135 of

Title 14, Code of Federal Regulations

(14 CFR parts 121 and 135) as follows:

PART 121—CERTIFICATION AND

OPERATIONS: DOMESTIC, FLAG, AND

SUPPLEMENTAL AIR CARRIERS AND

COMMERCIAL OPERATORS OF

LARGE AIRCRAFT

1. The authority citation for part 121

continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 40119,

44101, 44701–44702, 44705, 44709–44711,

44713, 44716–44717, 44722, 44901, 44903–

44904, 44912, 46105.

2. Section 121.345(c) is revised to

read as follows:

§ 121.345 Radio equipment.

* * * * *

(c) ATC transponder equipment

installed after January 1, 1992, must

meet the performance and

environmental requirements of the

following TSO’s:

(1) For aircraft not required to be

equipped with an approved TCAS II

traffic alert and collision avoidance

system pursuant to § 121.356, any class

of TSO–C74b or TSO–C74c, as

appropriate, or the appropriate class of

TSO–C112 (Mode S).

(2) For aircraft required to be

equipped with an approved TCAS II

traffic alert and collision avoidance

system pursuant to § 121.356, the

appropriate class of TSO–C112 (Mode

S).

PART 135—AIR TAXI OPERATORS

AND COMMERCIAL OPERATIONS

1. The authority citation for part 135

continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701–

44702, 44705, 44709, 44711–44713, 44715–

44717, 44722.

2. Section 135.143(c) is revised to

read as follows:

§ 135.143 General requirements.

* * * * *

(c) ATC transponder equipment

installed after January 1, 1992, must

meet the performance and

environmental requirements of any class

of TSO–C74b or TSO–C74c, as

appropriate, or the appropriate class of

TSO–C112 (Mode S).

Issued in Washington, DC on May 15,

1996.

William J. White,

Acting Director, Flight Standards Service.

[FR Doc. 96–13030 Filed 5–22–96; 8:45 am]

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