[Federal Register Volume 59, Number 249 (Thursday, December 29, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-31903]


[[Page Unknown]]

[Federal Register: December 29, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 94-SW-03-AD; Amendment 39-9112; AD 95-01-01]

 

Airworthiness Directives; Terra Corporation TRT 250 Series 
Transponders

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to Terra Corporation TRT 250 series transponders, that 
requires 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 Air 
Traffic Control Radio Beacon System (ATCRBS)/Mode S ground station and 
Traffic Collision Avoidance System (TCAS) II airborne equipment. This 
amendment is prompted by FAA tests that show that the transponder does 
not respond properly to certain interrogations by a Mode S or TCAS II 
signal. The actions specified by this AD are intended to prevent 
failure of the transponder to respond properly to Mode S interrogations 
from both Mode S ground stations and TCAS II airborne equipment, which 
could result in loss of airspace separation.

DATES: Effective February 6, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 6, 1995.

ADDRESSES: The service information referenced in this AD 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 Blvd., 
Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 
800 North Capitol Street, NW., suite 700, Washington, DC.

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

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to Terra Corporation TRT 250 series 
transponders was published in the Federal Register on May 26, 1994 (59 
FR 27249). The original comment period was open for 30 days. However, 
subsequently, the FAA determined that the original comment period was 
inadequate and reopened the comment period on September 6, 1994 (59 FR 
46007) with no additional changes in the proposed rule. That action 
proposed to 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.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Thirty-four comments were received 
from thirty-one commenters. Three of the commenters responded twice and 
two commenters commented on two different items contained in the Notice 
of Proposed Rulemaking (NPRM). Due consideration has been given to the 
comments received. Two commenters request that certain information be 
included in the preamble language that further explains the history 
behind these transponders and this AD. These commenters request that 
language be inserted in the final rule stating that: (1) these 
transponders have been produced since 1985; (2) these transponders meet 
the requirements of Technical Service Order (TSO)-C74c; (3) the Mode S 
ground stations and the TCAS II airborne equipment interrogates beyond 
the ATCRBS interrogation for which these transponders were designed 
instead of stating that the Mode S and TCAS II interrogates beyond the 
P3 pulse; and (4) the economic analysis that shows the $298 as the 
cost of the required parts not only includes the cost of the parts, but 
also the labor required to modify the affected transponders. While the 
FAA agrees with the substance of these comments, they are not proposing 
any changes to the AD language; therefore, no changes are made to the 
AD based upon these comments.
    Four commenters state that this AD should be published as an 
immediately adopted final rule because of its serious safety 
implications. The FAA does not concur. The FAA determined that, based 
upon the impact of the proposed requirements of this AD, it was 
appropriate to acquire as many public comments as possible prior to 
finalizing the actions. Therefore, the FAA published an NPRM soliciting 
public comments. To ensure the safety of flight, the Mode S ground 
stations are temporarily altered to permit the affected transponders to 
respond properly to ATCRBS interrogations during the compliance period.
    Another two commenters state that there is no justification for an 
extended compliance period and that compliance should be required as 
soon as possible. The FAA does not concur that a compliance time of 
less than 6 months is appropriate. With an estimated 5,000 transponders 
in the field that require replacement or modification, a compliance 
time of less than 6 months would not allow adequate time for all 
transponders to be modified or replaced.
    Two commenters state that longer compliance times should be 
provided within which to modify these transponders because no 
significant safety hazard exists. The FAA does not concur. In April 
1994, Terra Corporation notified its customers of the forthcoming FAA 
AD against the TRT 250 series transponders. The FAA informed the public 
via the NPRM process in May 1994, and provided a 30-day comment period. 
The comment period for the NPRM was reopened in September 1994 to 
provide another 60 days for additional comments. Public notices 
appeared in several aviation trade publications during this period. The 
manufacturer indicates that several hundred transponders have been 
modified since the May 1994 publication of the NPRM. Transport aircraft 
that utilize TCAS II and Mode S transponders cannot detect those 
aircraft equipped with a Terra transponder built according to the 
requirements of TSO-C74c. As a direct result of the Terra transponder 
problem, a thorough evaluation and a complete implementation of Mode S 
ground sensors cannot occur until the transponders are modified. In 
summary, this AD establishes the existence of an aviation safety 
problem, and the FAA has allowed an appropriate compliance time for 
action by owners or operators.
    One commenter states that the FAA employee or employees involved 
with the approval of the original transponder's design should pay for 
the costs of modifying the transponders. The FAA does not concur. The 
FAA as an agency is responsible for all directives, policies, mandates, 
etc., issued under its authority, and does not penalize employees for 
actions committed in good faith and within the scope of their duties.
    Twenty-two commenters state that since the FAA is responsible for 
the transponder's design problems, either because of the FAA's short-
sighted approval of the TSO used to produce these transponders, or 
because it decided to implement the Mode S ground sensors without 
adequate research and testing to determine whether all transponders 
would respond properly to the interrogations, the FAA should bear the 
costs associated with modifying these transponders. The FAA does not 
concur with the commenters. Although the FAA has determined that a 
safety problem exists with the transponder's design, the manufacturer 
is responsible for the design. The technical performance standards for 
airborne air traffic control (ATC) transponder equipment (TSO-C74c) 
were developed by a committee comprised of both government and industry 
representatives. A representative of the transponder manufacturer is 
included on the membership list for that committee. There have been no 
reports of other manufacturers having a similar transponder design 
deficiency. Additionally, the FAA's budget does not include allocations 
to cover AD costs incurred in modifying privately-owned equipment.
    Since the issuance of the NPRM, the manufacturer has issued 
Revision 1 to Mandatory Service Bulletin (MSB) No. SB-104 on June 27, 
1994. This revision adds an additional optional modification method to 
the original MSB No. SB-104, dated March 14, 1994, that was proposed to 
be incorporated by reference in the NPRM. Since the revised MSB imposes 
no additional burden on operators and is an optional relieving 
provision, MSB No. SB-104, Revision 1, dated June 27, 1994, is 
incorporated by reference in this final rule. Additionally, since the 
issuance of the NPRM, the FAA has reevaluated the labor rate, and based 
upon this evaluation, has increased the hourly labor rate to $60 per 
work hour instead of the proposed $55 per work hour. This change 
increases the estimated overall cost of this AD by $37,500 to 
$1,940,000.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with only editorial changes 
and the changes described previously. The FAA has determined that these 
changes will neither increase the economic burden on any operator nor 
increase the scope of the AD.
    The FAA estimates that 5,000 aircraft of U.S. registry will be 
affected by this AD, that it will take approximately 1.5 work hours per 
aircraft to accomplish the required actions, and that the average labor 
rate is $60 per work hour. Required parts will cost approximately $298 
per aircraft. Based on these figures, the total cost impact of the AD 
on U.S. operators is estimated to be $1,940,000.
    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.
    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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from 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. 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 a new airworthiness directive 
to read as follows:

95-01-01 Terra Corporation: Amendment 39-9112. 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 Level) 4 and below; 3-inch ATI-mounted TRT 250 pushbutton 
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.
    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), Revision 1, dated June 27, 
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 been modified in 
accordance with the provisions of SB-104, Revision 1, dated June 27, 
1994;
    (2) An unaffected Terra Corporation transponder; or,
    (3) Another manufacturer's transponder that responds properly to 
Mode S interrogations from both an Air Traffic Control Radio Beacon 
System (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, 
Revision 1, dated June 27, 1994, perform a ramp test in accordance 
with the Testing section of SB-104, Revision 1, dated June 27, 1994. 
Conduct the tests and checks required by section 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 
that has been modified and tested in accordance with SB-104, 
Revision 1, dated June 27, 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 Avionics 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 Airplane Certification Office.
    (f) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the aircraft to a location where 
the requirements of this AD can be accomplished.
    (g) The modification shall be done in accordance with Terra 
Corporation Mandatory Service Bulletin No. SB-104, Revision 1, dated 
June 27, 1994. 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 Terra Corporation, 
3520 Pan American Freeway NE, Albuquerque, New Mexico, 87107-4796. 
Copies may be inspected at the FAA, Office of the Assistant Chief 
Counsel, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.
    (h) This amendment becomes effective on February 6, 1995.

    Issued in Fort Worth, Texas, on December 21, 1994.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 94-31903 Filed 12-28-94; 8:45 am]
BILLING CODE 4910-13-P