[Federal Register Volume 61, Number 203 (Friday, October 18, 1996)]
[Proposed Rules]
[Pages 54364-54366]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-26707]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-242-AD]
RIN 2120-AA64


Airworthiness Directives; Airtell International, Inc., Centaurus 
Model C3-100 Ground Proximity Warning System (GPWS), as Installed in 
Various Airplanes

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 all Airtell International, Inc., 
Centaurus Model C3-100 GPWS equipment that is installed on any type of 
airplane. This proposal would require replacement of this equipment 
with a similar type of equipment that meets specific performance 
requirements. This proposal is prompted by results of an investigation, 
which revealed that, under certain circumstances, the Centaurus GPWS 
equipment does not provide the flight crew with aural warnings to 
indicate that the airplane is descending. The actions specified by the 
proposed AD are intended to prevent failure of the GPWS equipment to 
provide such aural warnings. If the flight crew relies on receiving 
such warnings and the GPWS equipment fails to provide those warnings, 
the ability of the flight crew to prevent the airplane from impacting 
the ground may be inhibited.

DATES: Comments must be received by November 25, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-242-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    Information concerning this proposal may be obtained from or 
examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, 
SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: John P. Dimtroff, Aerospace Engineer, 
Flight Test and Systems Branch, ANM-111, FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
telephone (206) 227-2117; fax (206) 227-1100.

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 shall 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 in 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 96-NM-242-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, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 96-NM-242-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    Section 135.153 of the Federal Aviation Regulations (14 CFR 
135.153) specifies that no turbine-powered airplane having a passenger 
seating configuration (excluding any pilot seat) of 10 or more seats 
may be operated unless the airplane is equipped with an approved ground 
proximity warning system (GPWS). In order to be considered approved, 
GPWS equipment must meet certain minimum performance standards 
prescribed in Technical Standard Order (TSO) C-92b, dated August 19, 
1976. That TSO references Radio Technical Commission for Aeronautics 
(RTCA) Document No. DO-161A, ``Minimum Performance Standards, Airborne 
Ground Proximity Warning Equipment,'' dated May 27, 1976, as an 
additional source of information. The RTCA document indicates that the 
minimum performance standards are a means of ensuring that GPWS 
equipment will satisfactorily perform its intended function under all 
conditions normally encountered in routine aeronautical operations.
    The FAA has received reports indicating that Centaurus Model C3-100 
GPWS equipment, which is installed in various transport, commuter, and 
normal category airplanes, does not meet the minimum performance 
standards prescribed in TSO C-92b.

GPWS Equipment, in General

    The GPWS equipment is an aid to the flight crew for determining the 
imminent occurrence of inadvertent contact of the airplane with the 
ground. This equipment is intended to supplement flight instrument 
data, which alerts the flight crew that inadvertent contact with the 
ground may occur. The GPWS equipment must provide indications of 
proximity to the ground in the following modes of aircraft operation:
    Mode 1. Excessive rates of descent;
    Mode 2. Excessive closure rate to terrain;
    Mode 3. Negative climb rate or altitude loss after takeoff;
    Mode 4. Flight into terrain when not in landing configuration; and
    Mode 5. Excessive downward deviation from an instrument landing 
system (ILS) glide slope.
    Distinctive aural warnings must be provided for Modes 1 through 4 
above. The aural warning for these modes must consist of the sound 
``Whoop-Whoop,'' followed by either ``Pull Up'' or ``Terrain'' (or 
other acceptable annunciation), which is repeated until the hazardous 
condition no longer exists.

Results of FAA Testing

    Subsequent to the reports discussed previously, the FAA conducted 
testing of two Centaurus Model C3-100 GPWS

[[Page 54365]]

units in accordance with RTCA Document No. DO-161A. Results of that 
testing confirmed that Centaurus Model C3-100 GPWS equipment does not 
meet all minimum performance standards specified in TSO C-92b and RTCA 
Document No. DO-161A. Specifically, failures occurred in Mode 2 
(excessive descent rate) and Mode 3 (descent after takeoff) of aircraft 
operation.
    The FAA has determined that the effect of the deficiencies found in 
Modes 2 and 3 could result in an unsafe condition. Those deficiencies 
are as follows:
    1. Mode 2A2. Using a start altitude of 2,450 feet, the FAA tested 
the GPWS equipment and listened for aural warnings issued at terrain 
closure rates from 2,500 to 7,000 feet per minute (fpm). At closure 
rates of 3,750 fpm and below, no warnings were received within the 
acceptable range. Warnings were issued at parameters outside specified 
minimum performance requirements.
    2. Mode 2A4. Using a start altitude of 2,450 feet, the FAA tested 
the GPWS equipment and listened for warnings issued at terrain closure 
rates from 2,500 to 7,000 fpm. Valid warnings were received at closure 
rates within the acceptable band until descent rates decreased to less 
than 3,500 fpm. Descent rates of less than 3,500 fpm yielded alarms 
outside the prescribed minimum performance requirements.
    3. Mode 2B1. Using a start altitude of 2,450 feet, the FAA tested 
the GPWS equipment and listened for warnings issued at terrain closure 
rates from 2,500 to 7,000 fpm. Valid warnings were received at closure 
rates within the acceptable band until descent rates decreased to less 
than 3,200 fpm. Descent rates of less than 3,200 fpm yielded alarms 
outside the prescribed minimum performance requirements.
    4. Mode 3B. Simulating takeoff from zero feet radio altitude to 700 
feet, the BARO rate (altitude loss) parameter was increased in 20-foot 
increments from 20 to 140 feet, and then to 500 and 1,000 feet. After 
numerous attempts, valid results could not be obtained, i.e., neither 
unit tested issued a warning at 140 feet (or less) altitude loss. At an 
altitude loss value above 140 feet, warnings were noted; however, these 
warnings were intermittent at times.

FAA's Findings

    Concerning Mode 2, the FAA finds that Centaurus Model C3-100 GPWS 
equipment does not provide the flight crew with appropriate aural 
warnings of encroaching terrain when the rate of descent of the 
airplane is 3,750 feet per minute or less at altitudes of 1,000 feet or 
below.
    In addition, regarding Mode 3, when an airplane is descending after 
takeoff, Centaurus Model C3-100 GPWS equipment does not provide an 
aural warning (``DON'T SINK'') when a barometric altitude loss of 140 
feet or less is encountered to indicate that the airplane is descending 
after takeoff.

FAA's Conclusions

    It is reasonable to assume that flight crews may come to rely on 
the aural warnings that should be provided by GPWS equipment during 
Modes 2 and 3 of aircraft operation. If the flight crew relies on 
receiving such warnings and the GPWS equipment fails to provide those 
warnings, the ability of the flight crew to prevent the airplane from 
impacting the ground may be inhibited.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist on other products of this same type design, the proposed AD would 
require removal and replacement of Centaurus Model C3-100 GPWS 
equipment with a similar type of equipment that meets specific 
performance requirements. The actions would be required to be 
accomplished in accordance with a method approved by the FAA.
    It also may be possible to correct the addressed unsafe condition 
by modifying the unit. However, the FAA has not identified any 
particular means by which such a modification may be accomplished. The 
FAA would consider a request for approval of an alternative method of 
compliance, in accordance with the provisions of this proposed AD, 
provided that adequate justification is presented to support such a 
request.

Cost Impact

    The FAA estimates that 30 airplanes of U.S. registry would be 
affected by this proposed AD, that it would take approximately 20 work 
hours per airplane to accomplish the proposed actions, and that the 
average labor rate is $60 per work hour. Required parts would cost 
approximately $16,000 per airplane. Based on these figures, the cost 
impact of the proposed AD on U.S. operators is estimated to be 
$516,000, or $17,200 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this AD were not adopted.

Regulatory Impact

    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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

Airtell International, Inc.: Docket 96-NM-242-AD.

    Applicability: Centaurus Model C3-100 ground proximity warning 
system (GPWS) equipment, as installed in, but not limited to, the 
following airplanes, certificated in any category:

Beech 99 series airplanes;
Beech 200 series airplanes;
Dassault Aviation Model Mystere-Falcon 200 series airplanes;
EMBRAER (Empresa Brasileira de Aeronautica S.A.) EMB-110 series 
airplanes;

[[Page 54366]]

Fairchild Aircraft Model SA226-TC series airplanes;
Fairchild Aircraft Model SA227-AT series airplanes; and
Grumman Model G-73 Mallard airplanes.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the GPWS equipment to provide certain 
aural warnings, which could inhibit the ability of the flight crew 
to prevent the airplane from impacting the ground, accomplish the 
following:
    (a) Within 60 days after the effective date of this AD, remove 
and replace Centaurus Model C3-100 GPWS equipment with a similar 
type of equipment that meets minimum performance standards specified 
in Technical Standard Order (TSO) C-92b, dated August 19, 1976. 
Accomplish the actions in accordance with a method approved by the 
Manager, Flight Test and Systems Branch, ANM-111, FAA, Transport 
Airplane Directorate.
    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Flight Test and Systems Branch, 
ANM-111. Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Flight Test and Systems 
Branch, ANM-111.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Manager, Flight Test and Systems Branch, ANM-111.

    (c) 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 airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on October 9, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-26707 Filed 10-17-96; 8:45 am]
BILLING CODE 4910-13-U