Airworthiness Directives; AlliedSignal Inc. KT 76A Air Traffic Control (ATC) Transponders

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-CE-30-AD; Amendment 39-10637; AD 98-14-03]

RIN 2120-AA64

Airworthiness Directives; AlliedSignal Inc. KT 76A Air Traffic

Control (ATC) Transponders

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that

applies to certain AlliedSignal Inc. (AlliedSignal) KT 76A ATC

transponders that are installed on aircraft. This AD requires

incorporating a modification on the affected transponders that consists

of replacing two resistor network modules with glass-coated modules.

This AD is the result of reports of these ATC transponders transmitting

misleading encoding altimeter information to ground-based ATC radar

sites and nearby Traffic Alert and Collision Avoidance System (TCAS)-

equipped aircraft. The actions specified by this AD are intended to

prevent the transmission of misleading encoding altimeter information

between affected aircraft caused by the inability of these ATC

transponders to coordinate with ground-based ATC radar sites and nearby

TCAS-equipped aircraft.

DATES: Effective August 16, 1998.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of August 16, 1998.

ADDRESSES: Service information that applies to this AD may be obtained

from AlliedSignal Inc., General Aviation Avionics, 400 N. Rogers Road,

Olathe, Kansas 66062-1212. This information may also be examined at the

Federal Aviation Administration (FAA), Central Region, Office of the

Regional Counsel, Attention: Rules Docket No. 97-CE-30-AD, Room 1558,

601 E. 12th Street, Kansas City, Missouri 64106; or at the Office of

the Federal Register, 800 North Capitol Street, NW, suite 700,

Washington, DC.

[[Page 35788]]

FOR FURTHER INFORMATION CONTACT: Mr. Roger A. Souter, Aerospace

Engineer, Wichita Aircraft Certification Office, FAA, 1801 Airport

Road, Mid-Continent Airport, Wichita, Kansas 67209; telephone: (316)

946-4134; facsimile: (316) 946-4407.

SUPPLEMENTARY INFORMATION:

Events Leading to the Issuance of This AD

A proposal to amend part 39 of the Federal Aviation Regulations (14

CFR part 39) to include an AD that would apply to certain AlliedSignal

KT 76A ATC transponders that are installed on aircraft was published in

the Federal Register as a notice of proposed rulemaking (NPRM) on

February 4, 1998 (63 FR 5763). The NPRM proposed to require replacing

two resistor network modules, RM401 and RM402, with new glass-coated

parts. Accomplishment of the proposed action as specified in the NPRM

would be in accordance with AlliedSignal Service Bulletin SB KT 76A-7,

dated July 1996.

The NPRM was the result of reports of these ATC transponders

transmitting misleading encoding altimeter information to ground-based

ATC radar sites and nearby Traffic Alert and Collision Avoidance System

(TCAS)-equipped aircraft.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

Comment Issue: The Compliance Time Should Be Extended

Three commenters believe that the proposed compliance time of 6

calendar months is unrealistic. These comments are detailed as follows:

1. One commenter states that, in order to accomplish the work,

Allied Signal would have to supply 38 repairmen who would work 8 hours

per day for 6 months. The commenter questions whether this commitment

will be made.

2. Another commenter agrees with the FAA's decision to state the

compliance in calendar time, but believes that a more appropriate and

more convenient time would be to require the work at the next annual

inspection or transponder system inspection. This would reduce the

down-time for the affected aircraft by allowing the work to be

accomplished during regularly scheduled maintenance.

3. The third commenter states that many of the affected

transponders will be part of a complete pitot-static system that

requires biennial calibration in accordance with Sec. 91.413 of the

Federal Aviation Regulations (14 CFR 91.413). The commenter proposes

that since the unit will already be at the avionics shop for this

calibration, then the FAA should write the compliance time to coincide

with the biennial pitot-static system calibration.

The FAA partially concurs with the above comments, as follows:

1. After re-evaluating all information related to this subject, the

FAA concurs that 6 calendar months is an unrealistic time period to

have the work accomplished on all of the affected transponders. The FAA

believes that a large number of the affected aircraft already have the

proposed modification incorporated on the transponder. Based on all

information, the FAA believes that a 12 calendar month compliance time

is more realistic. The final rule will reflect this change.

2. The 12 calendar month compliance time will allow the

modification to be incorporated during the airplane's next annual

inspection, as requested by the commenter.

3. Because the silver migration process is affected by

environmental factors as well as occurring over time, the FAA cannot

predict when a particular transponder could fail. A transponder could

work well one day and then fail the next day. With this in mind, the

FAA does not concur that the compliance time should be written to

coincide with the next pitot-static system biennial calibration in

accordance with Sec. 91.413 of the Federal Aviation Regulations (14 CFR

91.413). This could allow the condition defined in this AD to go

undetected for up to 24 months.

Comment Issue: Problem Occurs Only on Aircraft Operating Above

10,000 Feet and the AD Should Be Limited to Only Those Aircraft

Operating in Instrument Flight Rule (IFR) Conditions

Two commenters believe that the condition specified in the NPRM is

associated with ``at altitude'' operations over time. The commenters

state that one could imply that:

``aircraft in the high altitude structure may be more likely to

experience this problem than one operating below 10,000 feet and

using the Allied Signal KT 76A ATC transponder simply because the

aircraft operates within Class B or C airspace or within a 30

nautical miles ``veil'' for a class B airport. The problem with an

erroneous altitude report from a high speed aircraft operating in

the IFR airspace system is significantly different than a small

airplane flying in visual flight rules (VFR) conditions.''

Both commenters recommend different actions than are already

proposed based on the above information and both believe that the

private operator (who is mostly a Sunday pilot) would remove the

equipment from the aircraft since aircraft in VFR operation outside of

the B and C airspace do not need to have a transponder unit. Both

believe that removing the transponder would reduce safety. These

recommendations are as follows:

1. One commenter suggests that those operating in only VFR

conditions fabricate and install a placard with the words ``For VFR Use

Only''. If or when these aircraft's transponders no longer comply with

the 125-foot error requirement of part 43, Appendix E, of the Federal

Aviation Regulations (14 CFR part 43, Appendix E), then the commenter

proposes that the AD require immediate replacement or modification of

the transponder equipment. The commenter feels that this would allow

thousands of small aircraft to fly legally and safely within the 30

nautical mile veils associated with Class B airports, without incurring

an additional expense to their flying activities.

2. The other commenter recommends that the FAA not issue the

proposed AD as a final rule, or if issued, limit the Applicability of

the AD to only turbine-powered or ``10-or-more seats'' aircraft. This

commenter feels that replacing equipment that meets performance

standards because of a ``maybe'' malfunction (which will simply cause

an error in altitude reporting) is wrong when it comes to private

aircraft (used mostly for pleasure). The commenter also suggests a

possible mandatory replacement or modification of the equipment if a

certain error is detected.

The FAA does not concur with the proposed alternatives presented by

the commenters. The altitude at which an aircraft equipped with one of

the affected transponders is flown and the amount of time flown at this

altitude do not affect the probability of the unit failing. The

``silver migration'' process occurs regardless of the altitude or the

time ``at altitude''. This ``silver migration'' process is slow and is

affected by environmental factors as well. The FAA cannot assure that

any given unit would not be affected by this condition during any given

2 year period. A unit could pass on one day and then fail the next day.

Aircraft that are operated in VFR conditions are interrogated by TCAS-

equipped aircraft in the areas. The ATC system and misleading aircraft

altitude information could represent a hazard to the aircraft in VFR

conditions. The FAA has determined that safety would be compromised if

the AD allowed, for aircraft operating in VFR conditions, the

[[Page 35789]]

system to fail before mandating replacement or modification.

Comment Issue: Limit the AD to Only Those Aircraft Exhibiting

Problems

In addition to the comments above proposing replacement or

modification of the Allied Signal KT 76A ATC transponder upon condition

for aircraft operating in VFR conditions, one commenter proposes that

the AD only apply to those transponders that exhibit problems during

the 24 calendar month pitot-static system calibration in accordance

with Sec. 91.413 of the Federal Aviation Regulations (14 CFR 91.413).

This would be for all transponders regardless of the type of operation

in which the aircraft is involved. The commenter believes that this

would accomplish the intent of the AD without burdening operators

already in good working order.

The FAA does not concur. As discussed earlier, the FAA cannot

predict when a particular transponder could fail. A transponder could

work well one day and then fail the next day. The FAA has determined

that safety would be compromised if the AD allowed the system to fail

before mandating replacement or modification.

Comment Issue: Wait for Results of Technical Field Study on

Transponders

One commenter agrees with the FAA that the KT 76A ATC transponders

have a demonstrated history of inaccurate or misleading data

transmission and that corrective action is necessary to address this

issue. This commenter goes on to state that the FAA Technical Center in

Atlantic City conducted a full-scale field study of transponder

performance in general aviation aircraft and determined that a variety

of deficiencies exist in a broad range of transponders, including the

KT 76A ATC transponders. This commenter suggests that the FAA withhold

issuance of this AD until the full scope of the transponder issues can

be addressed, including the problems associated with ``silver

migration'' in the KT 76A ATC transponders.

The FAA concurs that the information from the Technical Center

Study is very important. However, correspondence received from the

Technical Center indicates that resolution of these issues may take a

considerable amount of time. As stated earlier, the FAA cannot predict

when a particular transponder could fail. A transponder could work well

one day and then fail the next day. The FAA has determined that safety

would be compromised if the AD was not issued awaiting a resolution

from the FAA Technical Center in Atlantic City, regarding the full

scope of the transponder issues.

Comment Issue: Certain Aspects Not Covered in the Cost Impact

Four commenters propose changes to the section that describes the

cost impact upon the public. These include:

--It will take 2.5 workhours to accomplish the action instead of 2

workhours as presented in the NPRM;

--In addition to providing parts at no charge, Allied Signal is

providing warranty credit for up to 2.5 workhours to accomplish the

action;

--The cost impact should include the costs of a recalibration of the

pitot-static system; and

--The cost impact does not take into account the costs the affected

aircraft operators will incur while their aircraft is out-of-service.

The FAA concurs that it will take 2.5 workhours to accomplish the

action and that Allied Signal will provide warranty credit for up to

2.5 workhours to accomplish the action. The final rule will incorporate

this information.

The FAA does not concur that the cost impact section should account

for recalibration costs because the inputs affected by the silver

migration are encoding altimeter inputs and are not directly connected

to the pitot static system. Therefore, there are no costs associated

with pitot static system when complying with this AD.

The FAA believes that the change in the compliance time from 6

calendar months to 12 calendar months will take into account the cost

impact of aircraft ``out-of-service.'' This will allow the operator to

schedule the replacement and modification to coincide with a regularly

schedule maintenance event, thus, the AD will not necessitate any

additional downtime. Even if additional downtime is necessary for some

airplanes, the FAA does not possess sufficient information to evaluate

the number of airplanes that may be so affected or the amount of

additional downtime that may be required.

Comment Issue: Include Statistical Data Concerning the Problem in

the AD

One commenter states that including statistical data that more

fully discusses the origin of the ``silver migration'' problem would be

helpful.

The FAA, in working with the manufacturer, saw a three-fold

increase in the usage of spare parts of the Allied Signal KT76A ATC

transponders. Between the last quarter of 1995 and the first quarter of

1996, quarterly usage of spare parts increased from approximately 40

parts per quarter to approximately 120 parts for that quarter. This

indicates a significant trend and failure analysis of these

transponders. Information submitted to the FAA revealed that this

increase in spare parts usage was due to the ``silver migration''

problem. Within a 3-month period, over 150 of these transponder units

were in the repair shops to have ``silver migration'' problems

remedied.

Comment Issue: Concur With the Action

One commenter agrees with the proposal as written and states that

accomplishing ``this relatively inexpensive and simple repair action

will eliminate the potential hazard and enhance general flying safety

in the National Airspace System.''

The FAA's Determination

After careful review of all available information related to the

subject presented above, the FAA has determined that air safety and the

public interest require the adoption of the rule as proposed except for

the change in the compliance time and minor editorial corrections. The

FAA has determined that this change and minor corrections will not

change the meaning of the AD and will not add any additional burden

upon the public than was already proposed.

Cost Impact

The FAA estimates that 20,000 transponder units could be affected

by this AD if all were installed in aircraft of U.S. registry.

Approximately 2.5 workhours will be needed to accomplish this action,

at an average labor rate of $60 an hour. However, Allied Signal will

provide warranty credit for up to 2.5 workhours to accomplish the

action, as well as providing all necessary parts at no cost to the

owners/operators of airplanes with the affected transponder units

installed. Based on these figures and Allied Signal's warranty program,

this AD will impose no cost impact on U.S. operators of the affected

aircraft.

Regulatory Impact

The regulations adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

[[Page 35790]]

For the reasons discussed above, I certify that this action (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); and (3) will not have a

significant economic impact, positive or negative, on a substantial

number of small entities under the criteria of the Regulatory

Flexibility Act. A copy of the final evaluation prepared for this

action is contained in the Rules Docket. A copy of it may be obtained

by contacting the Rules Docket at the location provided under the

caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends part 39 of

the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding a new airworthiness directive

(AD) to read as follows:

98-14-03 AlliedSignal Inc.: Amendment 39-10637; Docket No. 97-CE-

30-AD.

Applicability: AlliedSignal KT 76A Air Traffic Control (ATC)

transponders; part number (P/N) 066-1062-00/10/02; serial numbers

93,000 through 109,999, as installed on, but not limited to the

following airplanes (all serial numbers), certificated in any

category:

Cessna Aircraft Company: 172, 182, R182, T182, 06, P206, U206,

TP206, 210, T210, P210, 310, 310, T310, and 421 series airplanes.

Twin Commander Aircraft Company: 500, 520, 560, 680, 681, 685, 690,

695, and 720 series airplanes.

The New Piper Aircraft Corporation: PA-31, PA-32, and PA-34 series

airplanes.

Raytheon Aircraft Company: E33, F33, G33, 35, J35, K35, L35, K35,

M35, P35, S35, V35, 36, A26, B36, D55, E55, 56, A56, 58, 58A, 95,

B95, D95, and E95 series airplanes.

Mooney Aircraft Corporation: M20 series airplanes.

McDonnell Douglas Helicopter Company: Model 500N rotorcraft.

Note 1: This AD applies to each aircraft equipped with a

transponder that is identified in the preceding applicability

provision, regardless of whether it has been modified, altered, or

repaired in the area subject to the requirements of this AD. For

aircraft that have been modified, altered, or repaired so that the

performance of the requirements of this AD is affected, the owner/

operator must request approval for an alternative method of

compliance in accordance with paragraph (d) of this AD. The request

should include an assessment of the effect of the modification,

alteration, or repair on the unsafe condition addressed by this AD;

and, if the unsafe condition has not been eliminated, the request

should include specific proposed actions to address it.

Compliance: Required within the next 12 calendar months after

the effective date of this AD, unless already accomplished.

To prevent the transmission of misleading encoding altimeter

information between affected aircraft caused by the inability of the

affected ATC transponders to coordinate with ground-based air

traffic control (ATC) radar sites and nearby Traffic Alert and

Collision Avoidance System (TCAS)-equipped aircraft, accomplish the

following:

(a) Replace the two resistor network modules, M401 and RM402,

with new glass-coated parts in accordance with the MODIFICATION

PROCEDURE section of AlliedSignal Service Bulletin SB KT 76A-7,

dated July 1996. When accomplished, this replacement is referred to

as Mod 7.

(b) As of the effective date of this AD, no person may install

an AlliedSignal KT 76A ATC transponder; part number (P/N) 066-1062-

00/10/02; serial numbers 93,000 through 109,999, in an aircraft

without first incorporating Mod 7 as specified in paragraph (a) of

this AD.

(c) Special flight permits may be issued in accordance with

Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR

21.197 and 21.199) to operate the airplane to a location where the

requirements of this AD can be accomplished.

(d) An alternative method of compliance or adjustment of the

compliance time that provides an equivalent level of safety may be

approved by the Manager, Wichita Aircraft Certification Office

(ACO), 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita,

Kansas 67209. The request shall be forwarded through an appropriate

FAA Maintenance Inspector, who may add comments and then send it to

the Manager, Wichita ACO.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Wichita ACO.

(e) The replacement required by this AD shall be done in

accordance with AlliedSignal Service Bulletin SB KT 76A-7, dated

July 1996. This incorporation by reference was approved by the

Director of the Federal Register in accordance with 5 U.S.C. 552(a)

and 1 CFR part 51. Copies may be obtained from AlliedSignal Inc.,

General Aviation Avionics, 400 N. Rogers Road, Olathe, Kansas 66062-

1212. Copies may be inspected at the FAA, Central Region, Office of

the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City,

Missouri, or at the Office of the Federal Register, 800 North

Capitol Street, NW, suite 700, Washington, DC.

(f) This amendment becomes effective on August 16, 1998.

Issued in Kansas City, Missouri, on June 23, 1998.

Marvin R. Nuss,

Acting Manager, Small Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 98-17301 Filed 6-30-98; 8:45 am]

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