[Federal Register Volume 65, Number 231 (Thursday, November 30, 2000)]
[Rules and Regulations]
[Pages 71239-71241]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-30396]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-127-AD; Amendment 39-12026; AD 2000-24-19]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 35, 35A, 36, and 36A 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to all Learjet Model 35, 35A, 36, and 36A series airplanes, 
that requires 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 amendment 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: Effective January 4, 2001.

ADDRESSES: Information pertaining to this amendment may be examined at 
the Federal Aviation Administration (FAA), Transport Airplane 
Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; 
or at the FAA, Wichita Aircraft Certification Office, 1801 Airport 
Road, Room 100, Mid-Continent Airport, Wichita, Kansas.

FOR FURTHER INFORMATION CONTACT: Ben Sorensen, Flight Test Pilot, 
Flight Test and Program Management, ACE-117W, FAA, 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: 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 all Learjet Model 35, 35A, 36, and 
36A series airplanes was published in the Federal Register on June 8, 
2000 (65 FR 36391). That action proposed to 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. That proposal was 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.

Since the Issuance of the Proposal

    The FAA has determined that the identified unsafe condition is 
adequately addressed by Step 1 (donning the oxygen mask following a 
cabin high altitude warning) of the AFM revision under paragraph (a) of 
the proposed AD. In line with that determination, it is no longer 
necessary to include Steps 2 through 12 of paragraph (a). The FAA has 
revised paragraph (a) of the final rule accordingly.

Comments on the Proposal

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request To Withdraw the Proposal

    One commenter states that it opposes the adoption of the proposal, 
as well as the FAA's continued efforts to use rulemaking to address 
``operational'' concerns. The commenter contends that airworthiness 
directives should only address corrective actions that specifically 
identify product flaws that create an unsafe condition. In particular, 
the commenter maintains that the unsafe condition demands an 
``operational'' as well as an educational concern. The commenter 
further states that its primary concern with the proposal is that, in 
the accidents and incidents reports where incapacitation of the 
flightcrew was due to hypoxia, the root design or mechanical flaw has 
not been identified. The commenter concludes that a pilot's failure to 
don an oxygen mask raises ``operational'' concerns that have nothing to 
do with the specific problems concerning the continued airworthiness of 
the product in question. From these comments, the FAA infers that the 
commenter requests that the proposed AD be withdrawn.
    The FAA does not concur that the proposed AD should be withdrawn. 
The purpose of an AD is to correct an identified unsafe condition in 
products, regardless of where the unsafe condition is located or what 
it is caused by. The current AFM does not contain procedures to don 
oxygen masks when the cabin altitude aural warning is activated. The 
FAA considers that the lack of such procedures constitutes an unsafe 
condition and, as such, must be corrected. In essence, the requirement 
to revise the AFM to add procedures to don oxygen masks when the cabin 
altitude warning is activated serves to

[[Page 71240]]

protect the flying public from the consequences of the unsafe 
condition. The AD also serves to protect the manufacturer from the 
liability that would be faced should the unsafe condition not be 
corrected.

Request To Revise the Emergency Procedures

    One commenter requests that the proposed emergency descent 
procedures be revised to specify that the flightcrew (1) don the oxygen 
mask; (2) level off (stabilize) the aircraft; and (3) verify loss of 
cabin pressure. The commenter suggests that if loss of cabin pressure 
is verified, the flightcrew should continue with the remainder of the 
emergency procedures. The commenter states that the purpose of adding 
these steps would be to ensure that the procedures, as proposed, do not 
lead the flightcrew to a possible overreaction. The commenter concludes 
that the suggested additional steps would provide clear direction for 
the flightcrew when the cabin altitude warning horn activates.
    The FAA does not concur with the request to add procedures 
specifying that, immediately after donning the oxygen masks, the 
flightcrew level off the aircraft and verify loss of cabin pressure. As 
explained previously, the FAA has determined that, other than donning 
the oxygen masks, it is unnecessary to add further requirements to the 
Emergency Procedures Section of the AFM. The current FAA-approved AFM 
appears to take a conservative approach to cabin high altitude 
emergency procedures and specifies that the flightcrew perform an 
emergency descent. Furthermore, the FAA has not identified any unsafe 
conditions associated with those specific AFM procedures. The FAA has, 
however, forwarded the commenter's suggestions to the manufacturer for 
its consideration.

Request To Revise the Title of the Emergency Procedures

    One commenter, the manufacturer, requests that the title of the 
emergency procedures be revised to also address the condition where the 
flightcrew notices a high cabin altitude before the warning horn 
sounds. The commenter suggests that the following words be added to the 
title: ``* * * or Cabin Altitude Exceeds 10,000 feet.''
    The FAA finds that the suggested additional words will clarify and 
specify emergency procedures for a possible situation, and will 
encourage proactive flightcrew action. Therefore, the FAA concurs with 
the commenter's request, and has revised paragraph (a) of the AD 
accordingly.

Request To Add Certain Notes

    One commenter, the manufacturer, also requests that two new notes 
be added to clarify the proposed requirements of paragraph (a) after 
Step 10 and Step 12.
    The FAA does not concur. Since all steps except Step 1 of paragraph 
(a) of the proposal have been removed (as explained previously) from 
the proposed AD, it is unnecessary to provide further clarification of 
the other steps.

Request To Redesign the Oxygen System

    Two commenters request that the proposal include a requirement that 
the oxygen bottle in the cockpit be redesigned to show oxygen bottle 
pressure and not system pressure. Additionally, one of those commenters 
requests that the oxygen bottle clearly indicate that the system is 
``on'' during preflight.
    The FAA does not concur that this AD should require redesign of the 
oxygen bottle system. The FAA finds that a properly conducted preflight 
of the oxygen masks will establish and verify the correct gauge that 
reads bottle pressure, and ensure that the oxygen bottle valve is 
properly positioned. Additionally, the required flow check will not 
work if the oxygen bottle is turned off since all oxygen would have 
been released from the system. The actions required in this AD are 
intended to sufficiently address the stated unsafe condition.
    Since redesign of the oxygen bottle system was not specified in the 
proposal, to require such redesign in this AD would be to mandate 
requirements without benefit of opportunity for public comment. Since 
the FAA has received no reports of any unsafe conditions associated 
with the design of the indicating system or bottle pressure system, it 
is not considering further rulemaking at this time. However, the FAA 
has forwarded this suggestion to the manufacturer for its 
consideration.

Request To Add Additional Models to the Applicability

    One commenter requests that the applicability be revised to include 
Learjet Model 23, early Model 24, and Model 25 series airplanes. The 
commenter states that the oxygen and pressurization systems on these 
airplanes are similar to the airplane models cited in the applicability 
of the proposed AD.
    The FAA does not concur that additional airplane models should be 
added to the applicability of this AD. The FAA acknowledges that the 
oxygen and pressurization systems on those airplanes are similar to the 
Learjet Model 35 and 36 series airplanes. However, if those airplane 
models were added to the applicability of this AD, additional time for 
opportunity to comment would be required. The FAA finds that to delay 
this action would be inappropriate in light of the identified unsafe 
condition. If information is received that points to an unsafe 
condition on the Learjet Model 23, Model 24, or Model 25, the FAA will 
consider further rulemaking. The FAA will forward the commenter's 
suggestion to the airplane manufacturer.

Request To Identify Flight Conditions Where Emergency Descent Is 
Unnecessary

    One commenter requests that the FAA identify all flight conditions 
in which an emergency descent is not required subsequent to donning 
oxygen masks, and clearly present the appropriate instructions in the 
final rule. The commenter notes that the proposed AD specifies that, 
regardless of the existing flight conditions, the flightcrew perform an 
emergency descent upon activation of the cabin altitude warning. The 
commenter points out that it is possible for the cabin altitude warning 
horn to activate during flight conditions that would not require an 
emergency descent and landing.
    The FAA does not concur that identification of all flight 
conditions in which an emergency descent is not required is necessary. 
The FAA considers that the manufacturer has taken a prudent and 
conservative approach in establishing the current emergency descent 
procedures, which specify emergency descent is necessary regardless of 
flight conditions. However, for the reasons explained previously, other 
than donning the oxygen masks, the FAA has removed the requirement to 
complete additional emergency descent procedures from this final rule. 
Therefore, no change to the final rule is necessary in this regard.

Conclusion

    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 the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

[[Page 71241]]

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 will be affected by this 
AD, that it will take approximately 1 work hour per airplane to 
accomplish the required actions, and that the average labor rate is $60 
per work hour. Based on these figures, the cost impact of the 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 requirements of this AD 
action, and that no operator would accomplish those actions in the 
future if this 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 adopted herein will 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 final rule does not have federalism 
implications under Executive Order 13132.
    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, 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 the following new 
airworthiness directive:

2000-24-19  Learjet: Amendment 39-12026. 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 Procedures Section of the FAA-approved Airplane Flight 
Manual (AFM) by accomplishing the actions specified in paragraphs 
(a)(1) and (a)(2) of this AD:
    (1) Revise the title for the existing ``Emergency Descent'' 
section to read:

``CABIN ALTITUDE WARNING HORN ACTIVATES OR CABIN ALTITUDE EXCEEDS 
10,000 FEET (EMERGENCY DESCENT)''

    (2) Insert the procedures specified below between the new, 
revised title specified in paragraph (a)(1) of this AD and the 
existing procedures for emergency descent specified in the AFM.
    ``Don Oxygen Masks and Select 100% oxygen.''

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. 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: 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.

Effective Date

    (d) This amendment becomes effective on January 4, 2001.

    Issued in Renton, Washington, on November 22, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-30396 Filed 11-29-00; 8:45 am]
BILLING CODE 4910-13-P