Airworthiness Directives; PTC Aerospace Model 91700 Passenger Oxygen System

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-12; Amendment 39-9035; AD 94-20-07]

Airworthiness Directives; PTC Aerospace Model 91700 Passenger

Oxygen System

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to PTC Aerospace Model 91700 passenger oxygen system,

installed in PTC Aerospace Model 881, 940, and 950 seats installed on

McDonnell Douglas DC-10 series aircraft. This AD requires a one-time

inspection to verify the proper configuration and functioning of the

passenger oxygen system, and replacement, if necessary, with

serviceable parts. This amendment is prompted by oxygen canisters

failing to activate due to the installation of incorrect pin release

brackets or defective oxygen canister release pins. The actions

specified by this AD are intended to prevent failure of the passenger

oxygen system to activate.

DATES: Effective December 27, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of December 27, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from PTC Aerospace, 607 Bantam Road, Litchfield, CT 06759.

This information may be examined at the Federal Aviation Administration

(FAA), New England Region, Office of the Assistant Chief Counsel, 12

New England Executive Park, Burlington, MA; or at the Office of the

Federal Register, 800 North Capitol Street, NW., suite 700, Washington,

DC.

FOR FURTHER INFORMATION CONTACT: Terry Fahr, Aerospace Engineer, Boston

Aircraft Certification Office, FAA, Engine and Propeller Directorate,

12 New England Executive Park, Burlington, MA 01803-5299; telephone

(617) 238-7155, fax (617) 238-7199.

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 PTC Aerospace Model 91700

passenger oxygen system, installed in PTC Aerospace Model 881, 940, and

950 seats found on McDonnell Douglas DC-10 series aircraft, was

published in the Federal Register on September 21, 1993 (58 FR 48486).

That action proposed to require a one-time inspection to verify the

proper configuration and functioning of the passenger oxygen system,

and replacement, if necessary, with serviceable parts. The actions

would be required to be accomplished in accordance with PTC Service

Bulletin (SB) No. 25-1233, Revision D, dated February 2, 1993, that

describes procedures for a one-time inspection to verify the proper

configuration and functioning of the passenger oxygen system, and

replacement, if necessary, with serviceable parts.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the rule as proposed.

Two commenters state that the compliance time should be reduced,

one to six months after the effective date of the AD, the other to 30

days. The Federal Aviation Administration (FAA) does not concur.

Neither comment offered engineering or technical data to support a

reduction in the compliance interval from the 15-month compliance time

contained in the proposed rule. The proposed compliance time was

determined to provide an acceptable level of safety considering the

maintenance schedules of the operators. Therefore, the FAA has retained

the 15-month compliance time in the final rule.

One commenter states that the lanyard length check should be

deleted due to difficulty in performing that check. The FAA concurs

that the check was difficult to perform but does not concur in deleting

the check. The check is needed to verify the correct lanyard length.

Since publication of the NPRM, the manufacturer has advised the FAA

that the lanyard length tolerance has been increased to plus or minus

.25 inch, which will allow that check to be more easily accomplished.

This tolerance factor has been added to paragraph (a)(3) of this Final

rule.

One commenter states that the AD should require repetitive

inspections. The FAA does not concur. The one-time inspection, and

replacement, if necessary, with serviceable parts, required by this AD

will obviate the need for repetitive inspections other than those

performed during routine scheduled maintenance.

The commenter further states that the AD should contain a

requirement for reporting malfunctions. The FAA does not concur. The

one-time inspection, and replacement, if necessary, with serviceable

parts, required by this AD will preclude the need for reporting

malfunctions.

The commenter further states that the SB does not provide adequate

work step instructions. The FAA concurs. Since issuance of the NPRM,

PTC Aerospace has issued SB No. 25-1233, Revision E, dated April 15,

1994, which contains clarified work step instructions. The FAA has

added this new service bulletin to the AD.

The commenter further states that the SB should specify a different

oxygen canister safety cap. The revised SB specifies two safety caps.

The commenter further states that a functional test should be

required prior to disassembly. The FAA does not concur. The FAA has

determined that a functional test prior to disassembly would not

provide any benefit in evaluating the passenger oxygen system.

The commenter further states that there should be a snag test on

the release pin for grooves and burrs. The FAA does not concur. The FAA

believes that the instructions for testing as stated in the revised SB

are adequate.

Since publication of the NPRM, the manufacturer has advised the FAA

that an additional safety cap, Scott Part Number (P/N) 36425-00, is

available. Also, the manufacturer has added a black plastic grommet, P/

N 91880-2, on the pin release bracket, and a bushing, P/N 121836-1, on

the activator assembly spring, P/N H13341. Finally, the manufacturer

has included instructions for verifying the gap between the cable

actuating lever and the cable activating lever stop in PTC Aerospace SB

No. 25-1233, Revision E, dated April 15, 1994. These revised

instructions have been added to the compliance section of this final

rule.

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 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 initial estimate in the NPRM of approximately 3,000 passenger

oxygen systems of the affected design in the worldwide fleet was

incorrect. The manufacturer has advised the FAA that the revised number

is 4,800 passenger oxygen systems in the worldwide fleet. The FAA

estimates that 4,000 passenger oxygen systems are installed on aircraft

of U.S. registry, of which 2,500 have already been modified, leaving

approximately 1,500 passenger oxygen systems that have not yet been

modified in accordance with this AD. The FAA estimates that it will

take approximately 1 work hour per passenger oxygen system to

accomplish the required actions, and that the average labor rate is $55

per work hour. Required parts will cost approximately $20 per passenger

oxygen system. Based on these figures, the total cost impact of the AD

on U.S. operators is estimated to be $112,500.

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 the following new

airworthiness directive:

94-20-07 PTC Aerospace: Amendment 39-9035. Docket 93-ANE-12.

Applicability: PTC Aerospace Model 91700 passenger oxygen

system, installed in PTC Aerospace Model 881, 940, and 950 seats,

installed on McDonnell Douglas DC-10 series aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the passenger oxygen system to activate,

accomplish the following:

(a) Within 15 months after the effective date of this AD, or the

next seat removal, whichever occurs first, verify the proper

configuration and functioning of the passenger oxygen system in

accordance with PTC Aerospace Service Bulletin No. 25-1233, Revision

E, dated April 15, 1994, as follows:

(1) Remove the seat bottom cushion and open the oxygen housing

assembly door, Part Number (P/N) 91626, to expose the oxygen

canister and lower firing system. On the Model 950 seats, remove

fastening screws of the center console, P/N 98154, and rotate the

console forward in addition to removing the cushion.

(2) Install an oxygen canister safety cap, Tri-Star P/N CD3, or

Scott P/N 36425, to prevent discharging of the oxygen canister.

(3) Remove the cable release assembly, P/N 91601. Verify that

the assembly is the correct length (10.25 inches plus or minus .25

inch), that the release pin, P/N 91587-1, is free of burrs and

notches, and that the nylon cord is not worn and is free of any burn

damage. If any discrepancies are found, replace with a serviceable

unit.

(4) Verify installation of the correct pin release bracket, P/N

91602-1. A correct bracket has its plastic grommet located

vertically above the oxygen canister release sleeve. If the bracket

is found to be misaligned, replace it with a correct bracket.

Replace the white plastic grommet with a new black plastic grommet,

P/N 122326, securing it with Devo 44044 cyanoacrylate adhesive or

equivalent. The grommet is correctly positioned when the grommet

slot is aligned with the pin release bracket slot.

(5) Reassemble the cable release assembly with the safety cap on

the oxygen canister. Adjust and tighten the jam nuts, P/N H12292, to

obtain a gap between the cable actuating lever, P/N 91599-1 or -2,

and cable actuating lever stop, P/N 87310-3, within .03 inch and .25

inch. Verify that the nylon cord will not contact the oxygen

canister in the assembled configuration and that the cable release

pin will release from the oxygen canister with a tension of one

pound or less. If any discrepancies are found, replace the cable

release assembly with a serviceable unit.

(6) Remove the oxygen masks from the seat back housing. Compress

the actuator assembly spring, P/N H13341, and install a bushing, P/N

121836-1, oriented so that the spring seats in the bushing's

counterbore.

(7) Reassemble the oxygen system components with the safety cap

on the oxygen canister. Verify that the oxygen system functions

properly by verifying that the lanyard assembly release pin, P/N

91587-1, releases from the oxygen canister when the masks are pulled

from the seat back housing. If any discrepancies are found, replace

the oxygen system with a serviceable unit.

(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, Boston Aircraft Certification

Office. The request should be forwarded through an appropriate FAA

Principal Maintenance Inspector, who may add comments and then send

it to the Manager, Boston Aircraft Certification Office.

Note: Information concerning the existence of approved

alternative methods of compliance with this airworthiness directive,

if any, may be obtained from the Boston Aircraft Certification

Office.

(c) Special flight permits may be issued in accordance with

Secs. 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.

(d) The verification and modification shall be done in

accordance with the following service bulletin:

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Document No. Pages Revision Date

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PTC Aerospace..............

SB No. 25-1233............. 1-18 E April 15, 1994.

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Total:................. 18.

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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 PTC Aerospace, 607 Bantam Road, Litchfield,

CT 06759. Copies may be inspected at the FAA, New England Region,

Office of the Assistant Chief Counsel, 12 New England Executive Park,

Burlington, MA; or at the Office of the Federal Register, 800 North

Capitol Street NW., suite 700, Washington, DC.

(e) This amendment becomes effective on December 27, 1994.

Issued in Burlington, Massachusetts, on September 12, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-26139 Filed 10-27-94; 8:45 am]

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