[Federal Register Volume 59, Number 101 (Thursday, May 26, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-12868]


[[Page Unknown]]

[Federal Register: May 26, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-SW-03-AD]

 

Airworthiness Directives: Terra Corporation TRT 250 Series 
Transponder

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to the Terra Corporation TRT 250 
series transponder (transponder). This proposal would require removing 
the transponder from the aircraft, inspecting it to determine if the AD 
applies, and replacing any affected transponder with a modified Terra 
Corporation transponder or another transponder that responds properly 
to Mode S interrogations from both an ATCRBS/Mode S ground station and 
TCAS II airborne equipment. This proposal is prompted by FAA tests that 
show that the transponder does not reply to certain interrogations by a 
Mode S or Traffic Collision Avoidance System (TCAS) II signal. The 
actions specified by the proposed AD are intended to prevent failure of 
the transponder to reply to Mode S interrogations from both Mode S 
ground stations and TCAS II airborne equipment which could result in 
loss of airspace separation.

DATES: Comments must be received by June 27, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Assistant Chief Counsel, Attention: 
Rules Docket No. 94-SW-03-AD, 2601 Meacham Boulevard, room 663, Fort 
Worth, Texas 76137-4298. Comments may be inspected at this location 
between 9 a.m. and 3 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Terra Corporation, 3520 Pan American Freeway NE, 
Albuquerque, New Mexico 87107-4796. This information may be examined at 
the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Boulevard, 
room 663, Fort Worth, Texas.

FOR FURTHER INFORMATION CONTACT:
Mr. George R. Hash, Aerospace Engineer, Airplane Certification Office, 
FAA, Rotorcraft Directorate, 2601 Meacham Boulevard, Fort Worth, Texas 
76137, telephone (817) 222-5134, fax (817) 222-5959.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained is this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 94-SW-03-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Office of the Assistant Chief Counsel, Attention: Rules 
Docket No. 94-SW-03-AD, 2601 Meacham Boulevard, room 663, Fort Worth, 
Texas 76137-4298.

Discussion

    This notice proposes the adoption of a new airworthiness directive 
(AD), that is applicable to the Terra Corporation TRT 250 transponder, 
part number (P/N) 0900-0250-00, with serial numbers (S/N) 4194 and 
below, Modification Level (Mod Level) 4 and below; 3-inch ATI-mounted 
TRT 250 push-button transponders, P/N 0900-0250-20, with S/N 5324 and 
below, Mod Level 4 and below; and, TRT 250 D digital display 
transponders, P/N 0900-0250-30, with S/N 1155 and below, Mod Level 1 
and below (transponder). Recent FAA tests have shown that these 
transponders do not reply to Air Traffic Control Radio Beacon System 
(ATCRBS) only or ATCRBS/Mode S ``all-call'' interrogations by a Mode S 
ground sensor. The affected transponder processes interrogation data 
beyond the P3 pulse as an invalid interrogation, which causes it 
to suppress the reply. The Mode S ground stations and the TCAS II 
airborne equipment interrogates beyond the P3 pulse. This 
inability of the affected transponder to reply to valid interrogations 
creates an unsafe condition. This condition, if not corrected, could 
result in failure of the transponder to reply to Mode S interrogations 
from Mode S ground stations and TCAS II airborne equipment, which could 
result in loss of airspace separation.
    The FAA has reviewed and approved Terra Corporation Mandatory 
Service Bulletin SB-104, dated March 14, 1994, that describes 
procedures for modifying the transponder and then performing a final 
test procedure on the transponder unit.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require, within 6 months after the effective date of 
this AD, removal of the transponders to determine the P/N, S/N, and Mod 
Level. This proposal would also require replacement of any affected 
transponder with an appropriately modified Terra Corporation 
transponder or another transponder that responds properly to Mode S 
interrogations from both an ATCRBS/Mode S ground station and TCAS II 
airborne equipment.
    The FAA has temporarily altered the Mode S ground sensors to permit 
the affected transponder to function normally. However, in order to 
make the Mode S ground sensors operational in support of the new 
national digital communication data link implementation, this temporary 
alteration will be removed following the replacement of all the 
affected transponders. The AD proposes to allow 6 months for 
replacement of the affected transponders.
    The FAA estimates that 5,000 aircraft of U.S. registry would be 
affected by this proposed AD, that it would take approximately 1.5 work 
hours to accomplish the proposed actions, and that the average labor 
rate is $55 per work hour. Required parts would cost approximately $298 
per transponder. Based on these figures, the total cost impact of the 
proposal on U.S. operators is estimated to be $1,902,500.
    The regulations proposed 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.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 draft 
regulatory 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, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Terra Corporation: Docket No. 94-SW-03-AD.

    Applicability: Model TRT 250 transponders, part number (P/N) 
0900-0250-00, with serial numbers (S/N) 4194 and below, Modification 
Level (Mod Leval) 4 and below; 3-inch ATI-mounted TRT 250 push-
button transponders, P/N 0900-0250-20, with S/N 5324 and below, Mod 
Levels 4 and below; and, TRT 250 D digital display transponders, P/N 
0900-0250-30, with S/N 1155 and below, Mod Level 1 and below 
(transponder).
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the transponder to respond properly to 
Mode S interrogations from Mode S ground stations and Traffic 
Collision Avoidance System (TCAS) II airborne equipment, which could 
result in loss of airspace separation, accomplish the following:
    (a) Within 6 months after the effective date of this AD, remove 
the TRT 250 series transponder in accordance with the procedures 
stated in the Accomplishment Section of Terra Corporation Mandatory 
Service Bulletin No. SB-104 (SB-104), dated March 14, 1994, and 
determine the part number (P/N), serial number (S/N), and 
modification level (Mod Level).
    (b) If the determination made in paragraph (a) reveals one of 
the affected part numbers, serial numbers, and modification levels 
indicated in this AD, replace the affected transponder with:
    (1) A Terra Corporation transponder that has modified in 
accordance with the provisions of SB-104, dated March 14, 1994;
    (2) An unaffected Terra Corporation transponder; or,
    (3) Another manufacturer's transponder that responds properly to 
Mode S interrogations from both an ATCRBS/Mode S ground station and 
TCAS II airborne equipment.
    (c) If installing a replacement Terra Corporation transponder 
that has been modified in accordance with the provisions of SB-104, 
dated March 14, 1994, perform a ramp test in accordance with the 
Testing section of SB-104, dated March 14, 1994. Conduct the tests 
and checks required by Sec. 91.413 of the Federal Aviation 
Regulations (14 CFR 91.413) prior to approving the aircraft for 
return to service.
    (d) Installation of an affected Terra Corporation transponder 
modified and tested in accordance with SB-104, dated March 14, 1994, 
or another transponder that responds properly to Mode S 
interrogations from both an ATCRBS/Mode S ground station and TCAS II 
airborne equipment constitutes terminating action for the 
requirements of this AD.
    (e) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used when approved by the Manager, Airplane Certification Office, 
FAA, Rotorcraft Directorate. Operators shall submit their requests 
through an FAA Principal Maintenance Inspector, who may concur or 
comment and then send it to the Manager, Airplane Certification 
Office.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Airplance Certification Office.

    Issued in Fort Worth, Texas, on May 18, 1994.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 94-12868 Filed 5-25-94; 8:45 am]
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