[Federal Register Volume 65, Number 111 (Thursday, June 8, 2000)]
[Proposed Rules]
[Pages 36391-36393]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-14438]


========================================================================
Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

========================================================================


Federal Register / Vol. 65, No. 111 / Thursday, June 8, 2000 / 
Proposed Rules

[[Page 36391]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-127-AD]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 35, 35A, 36, and 36A 
Series 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 Learjet Model 35, 35A, 36, and 
36A series airplanes. This proposal would require revision of the 
Airplane Flight Manual (AFM) to add procedures for donning the 
flightcrew oxygen masks when the cabin altitude warning horn is 
activated. This action is intended to prevent incapacitation of the 
flightcrew due to lack of oxygen and consequent loss of control of the 
airplane due to absence of AFM procedures for donning the flightcrew 
oxygen masks when the cabin altitude warning horn is activated.

DATES: Comments must be received by July 24, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-127-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. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
<a href="/cdn-cgi/l/email-protection#d7eefab6b9bafab9a7a5bab4b8babab2b9a397b1b6b6f9b0b8a1"><span class="__cf_email__" data-cfemail="221b0f434c4f0f4c52504f414d4f4f474c56624443430c454d54">[email protected]</span></a>. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-127-AD'' in the subject line and need not 
be submitted in triplicate.
    Information regarding this docket may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Ben Sorensen, Flight Test Pilot, ACE-
117W, FAA, Small Airplane Directorate, Wichita Aircraft Certification 
Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, 
Kansas 67209; telephone (316) 946-4165; fax (316) 946-4407.

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.
    Submit comments using the following format:
    <bullet> Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    <bullet> For each issue, state what specific change to the proposed 
AD is being requested.
    <bullet> Include justification (e.g., reasons or data) for each 
request.
    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 2000-NM-127-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-114, Attention: Rules 
Docket No. 2000-NM-127-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On October 25, 1999, a Learjet Model 35 series airplane operating 
under part 135 of the Federal Aviation Regulations (14 CFR 135) 
departed Orlando International Airport enroute to Dallas, Texas. Air 
traffic control lost communication with the airplane near Gainsville, 
Florida. Air Force and National Guard airplanes intercepted the 
airplane, but the flightcrews of the chase airplanes indicated that the 
windows of the Model 35 series airplane were apparently frosted over 
and prevented the chase airplane flightcrews from observing the 
interior of the Model 35 series airplane. The flightcrews of the chase 
airplanes reported that they did not observe any damage to the 
airplane. Subsequently, the Model 35 series airplane ran out of fuel 
and crashed in South Dakota. To date, causal factors of the accident 
have not been determined. However, lack of the Learjet flightcrew's 
response to air traffic control poses the possibility of flightcrew 
incapacitation and raises concerns with the pressurization and oxygen 
systems.
    Recognizing these concerns, the FAA initiated a special 
certification review (SCR) to determine if pressurization and oxygen 
systems on Model 35 series airplanes were certificated properly, and to 
determine if any unsafe design features exist in the pressurization and 
oxygen systems.
    The SCR team found that there have been several accidents and 
incidents that may have involved incapacitation of the flightcrews 
during flight. In one case, the airplane flightcrew did not activate 
the pressurization system or don their oxygen masks and the airplane 
flew in excess of 35,000 feet altitude. In another case, the airplane 
flightcrews did not don their oxygen masks when the cabin aural warning 
was activated. Further review by the SCR team indicates that the 
Airplane Flight Manual (AFM) of Learjet Model 35/36 series airplanes do 
not have an emergency procedure that requires donning the flightcrew 
oxygen masks when the cabin altitude aural warning is

[[Page 36392]]

activated. Additional review has found that the AFM's of Model 35A and 
36A series airplanes also do not contain appropriate flightcrew actions 
when the cabin altitude aural warning is activated. However, the AFM's 
do contain an abnormal procedure that allows the flightcrew to 
troubleshoot the pressurization system prior to donning the oxygen 
masks after the cabin altitude warning sounds. Troubleshooting may 
delay donning of the oxygen masks to the point that flightcrews may 
become incapable of donning their oxygen masks.
    The SCR findings indicated that the most likely cause for 
incapacitation was hypoxia (lack of oxygen). The only other plausible 
cause of incapacitation is exposure to toxic substances. However, no 
evidence was found to support the existence of toxic substances.
    Delayed response of the flightcrew in donning oxygen masks when the 
activation of the cabin altitude warning horn could lead to 
incapacitation of the flightcrew and loss of control of the airplane.

Explanation of Requirements of Proposed Rule

    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 revising Emergency Procedures Section of the 
AFM to provide the flightcrew with appropriate and timely actions in 
response to activation of the cabin altitude warning horn.

Cost Impact

    There are approximately 739 Learjet Model 35, 35A, 36, and 36A 
series airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 500 airplanes of U.S. registry would be affected by this 
proposed AD, that it would take approximately 1 work hour per airplane 
to accomplish the proposed actions, and that the average labor rate is 
$60 per work hour. Based on these figures, the cost impact of the 
proposed AD on U.S. operators is estimated to be $30,000, or $60 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 proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect 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, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    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:

Learjet: Docket 2000-NM-127-AD.

    Applicability: Model 35, 35A, 36, and 36A series airplanes, 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent incapacitation of the flightcrew and consequent loss 
of control of the airplane due to delays in donning oxygen masks in 
response to the activation of the cabin altitude warning horn; 
accomplish the following:
    (a) Within 10 days after the effective date of this AD, revise 
the Emergency Procedure Section of the FAA-Approved Airplane Flight 
Manual (AFM) to include the following. This may be accomplished by 
inserting a copy of this AD into the AFM.

``CABIN ALTITUDE WARNING HORN ACTIVATES (EMERGENCY DESCENT)

    1. Oxygen Masks--Don. Select 100% oxygen.
    2. Thrust Levers--IDLE.
    3. Autopilot--Disengage.
    4. SPOILER switch--EXT.
    5. Landing gear switch--DN below MMO VLE as appropriate for 
altitude. Keep sideslip angles to a minimum (ball centered) when 
extending gear.
    6. Descend at MMO or VLE as appropriate, but NOT below minimum 
safe altitude.
    7. PASS OXY Valve--NORM.
    8. PASS MASK Valve--MAN.
WARNING: If pressurization loss is due to structural failure, limit 
speeds and maneuvering loads as much as possible in descent.

NOTE:
    Descent from 45,000 feet to 15,000 feet requires approximately 2 
minutes 45 seconds.
    Hats and ``ear-muff'' type headsets must be removed prior to 
donning crew oxygen masks.
    Communication between crewmembers can be accomplished by using 
the INPH function of the AUDIO CONTROL PANEL and adjusting the 
MASTER VOL.
    Communication with passengers can be accomplished by using PASS 
SPKR function of the AUDIO CONTROL panel and adjusting the PASS SPKR 
VOL level.
    The HORN SILENCE switch will mute the cabin altitude warning 
horn for 60 seconds.

    If Time and Conditions Permit:
    9. Transponder--Emergency 7700.
    10. Pilot and Copilot OXY--MIC switches--ON.
    11. Notify controlling agency.
    12. Check condition of passengers and provide assistance if 
conditions permit.''

Alternative Methods of Compliance

    (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, Wichita Aircraft Certification 
Office (ACO), FAA, Small Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Wichita ACO.

    Note 1: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Wichita ACO.

Special Flight Permit

    (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.


[[Page 36393]]


    Issued in Renton, Washington, on June 2, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-14438 Filed 6-7-00; 8:45 am]
BILLING CODE 4910-13-U


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