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.

Proposed Rules Federal Register

20787 

Vol. 75, No. 76 

Wednesday, April 21, 2010 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2010–0382; Directorate 

Identifier 2009–NM–211–AD] 

RIN 2120–AA64 

Airworthiness Directives; Bombardier, 

Inc. Model DHC–8–400, –401, and –402 

Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to adopt a new 

airworthiness directive (AD) for the 

products listed above that would 

supersede an existing AD. This 

proposed AD results from mandatory 

continuing airworthiness information 

(MCAI) originated by an aviation 

authority of another country to identify 

and correct an unsafe condition on an 

aviation product. The MCAI describes 

the unsafe condition as: 

Several cases have been reported where a 

loss of fluid in the No. 2 hydraulic system 

has caused the power transfer unit (PTU) to 

overspeed, resulting in pressure fluctuations 

and increased fluid flow within the No. 1 

hydraulic system. In one case, the hydraulic 

system control logic did not shut down the 

PTU and the overspeed condition persisted, 

resulting in the illumination of the No. 1 

HYD FLUID HOT caution light. 

* * * * * 

The unsafe condition is possible loss 

of both the No. 1 and No. 2 hydraulic 

systems, resulting in the potential loss 

of several functions essential for safe 

flight and landing of the airplane. The 

proposed AD would require actions that 

are intended to address the unsafe 

condition described in the MCAI. 

DATES: We must receive comments on 

this proposed AD by June 7, 2010. 

ADDRESSES: You may send comments by 

any of the following methods: 

• Federal eRulemaking Portal: Go to 

http://www.regulations.gov. Follow the 

instructions for submitting comments. 

• Fax: (202) 493–2251. 

• Mail: U.S. Department of 

Transportation, Docket Operations, M– 

30, West Building Ground Floor, Room 

W12–140, 1200 New Jersey Avenue, SE., 

Washington, DC 20590. 

• Hand Delivery: U.S. Department of 

Transportation, Docket Operations, M– 

30, West Building Ground Floor, Room 

W12–40, 1200 New Jersey Avenue SE., 

Washington, DC, between 9 a.m. and 5 

p.m., Monday through Friday, except 

Federal holidays. 

For service information identified in 

this proposed AD, contact Bombardier, 

Inc., 400 Coˆte-Vertu Road West, Dorval, 

Que ́bec H4S 1Y9, Canada; telephone 

514–855–5000; fax 514–855–7401; email thd.qseries@aero.bombardier.com; 

Internet http://www.bombardier.com. 

You may review copies of the 

referenced service information at the 

FAA, Transport Airplane Directorate, 

1601 Lind Avenue, SW., Renton, 

Washington. For information on the 

availability of this material at the FAA, 

call 425–227–1221. 

Examining the AD Docket 

You may examine the AD docket on 

the Internet at http:// 

www.regulations.gov; or in person at the 

Docket Operations office between 9 a.m. 

and 5 p.m., Monday through Friday, 

except Federal holidays. The AD docket 

contains this proposed AD, the 

regulatory evaluation, any comments 

received, and other information. The 

street address for the Docket Operations 

office (telephone (800) 647–5527) is in 

the ADDRESSES section. Comments will 

be available in the AD docket shortly 

after receipt. 

FOR FURTHER INFORMATION CONTACT: 

Fabio Buttitta, Aerospace Engineer, 

Airframe and Mechanical Systems 

Branch, ANE–171, FAA, New York 

Aircraft Certification Office, 1600 

Stewart Avenue, Suite 410, Westbury, 

New York 11590; telephone (516) 228– 

7303; fax (516) 794–5531. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

We invite you to send any written 

relevant data, views, or arguments about 

this proposed AD. Send your comments 

to an address listed under the 

ADDRESSES section. Include ‘‘Docket No. 

FAA–2010–0382; Directorate Identifier 

2009–NM–211–AD’’ at the beginning of 

your comments. We specifically invite 

comments on the overall regulatory, 

economic, environmental, and energy 

aspects of this proposed AD. We will 

consider all comments received by the 

closing date and may amend this 

proposed AD based on those comments. 

We have lengthened the 30-day 

comment period for proposed ADs that 

address MCAI originated by aviation 

authorities of other countries to provide 

adequate time for interested parties to 

submit comments. The comment period 

for these proposed ADs is now typically 

45 days, which is consistent with the 

comment period for domestic transport 

ADs. 

We will post all comments we 

receive, without change, to http:// 

www.regulations.gov, including any 

personal information you provide. We 

will also post a report summarizing each 

substantive verbal contact we receive 

about this proposed AD. 

Discussion 

On July 31, 2008, we issued AD 2008– 

17–06, Amendment 39–15644 (73 FR 

47818, August 15, 2008). That AD 

required actions intended to address an 

unsafe condition on the products listed 

above. 

Since we issued AD 2008–17–06, a 

modification of the power transfer unit 

(PTU) control logic, including the 

provision of automatic PTU shutdown 

in the event of loss of fluid in the No. 

2 hydraulic system, has been developed. 

The modification addresses the 

identified unsafe condition. In addition, 

the applicability has been revised to 

remove airplanes having serial number 

4185 and subsequent, since an 

equivalent modification has been 

installed in production on these 

airplanes. Transport Canada Civil 

Aviation (TCCA), which is the aviation 

authority for Canada, has issued 

Canadian Airworthiness Directive CF– 

2006–08R1, dated August 31, 2009 

(referred to after this as ‘‘the MCAI’’), to 

correct an unsafe condition for the 

specified products. The MCAI states: 

Several cases have been reported where a 

loss of fluid in the No. 2 hydraulic system 

has caused the power transfer unit (PTU) to 

overspeed, resulting in pressure fluctuations 

and increased fluid flow within the No. 1 

hydraulic system. In one case, the hydraulic 

system control logic did not shut down the 

PTU and the overspeed condition persisted, 

resulting in the illumination of the No.1 HYD 

FLUID HOT caution light. 


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20788 Federal Register / Vol. 75, No. 76 / Wednesday, April 21, 2010 / Proposed Rules 

As an interim action to avoid possible loss 

of both the No. 1 and No. 2 hydraulic 

systems, the Airplane Flight Manual (AFM) 

has been revised to include pulling the HYD 

PWR XFER circuit breaker in the event of the 

loss of all hydraulic fluid in the No. 2 

hydraulic system. 

Insertion of the resultant Temporary 

Amendment (TA) No. 13 into the AFM was 

mandated in the original issue of this 

[Canadian] directive. This instruction * * * 

remains in effect until * * * this [revised] 

directive is accomplished. 

Revision 1 of this directive * * * 

mandates modification of the PTU control 

logic, including the provision of automatic 

PTU shutdown in the event of loss of fluid 

in the No. 2 hydraulic system. In addition, 

the applicability of the [Canadian] directive 

has been revised to remove aircraft Serial 

Number (SN) 4185 and subsequent, since an 

equivalent modification has been installed in 

production on these aircraft. 

The unsafe condition is possible loss 

of both the No. 1 and No. 2 hydraulic 

systems, resulting in the potential loss 

of several functions essential for safe 

flight and landing of the airplane. You 

may obtain further information by 

examining the MCAI in the AD docket. 

Relevant Service Information 

Bombardier has issued Service 

Bulletin 84–29–22, Revision A, dated 

February 24, 2009. The actions 

described in this service information are 

intended to correct the unsafe condition 

identified in the MCAI. 

FAA’s Determination and Requirements 

of This Proposed AD 

This product has been approved by 

the aviation authority of another 

country, and is approved for operation 

in the United States. Pursuant to our 

bilateral agreement with the State of 

Design Authority, we have been notified 

of the unsafe condition described in the 

MCAI and service information 

referenced above. We are proposing this 

AD because we evaluated all pertinent 

information and determined an unsafe 

condition exists and is likely to exist or 

develop on other products of the same 

type design. 

Differences Between This AD and the 

MCAI or Service Information 

We have reviewed the MCAI and 

related service information and, in 

general, agree with their substance. But 

we might have found it necessary to use 

different words from those in the MCAI 

to ensure the AD is clear for U.S. 

operators and is enforceable. In making 

these changes, we do not intend to differ 

substantively from the information 

provided in the MCAI and related 

service information. 

We might also have proposed 

different actions in this AD from those 

in the MCAI in order to follow FAA 

policies. Any such differences are 

highlighted in a Note within the 

proposed AD. 

Costs of Compliance 

Based on the service information, we 

estimate that this proposed AD would 

affect about 42 products of U.S. registry. 

The actions that are required by AD 

2008–17–06 and retained in this 

proposed AD take up about 1 work-hour 

per product, at an average labor rate of 

$85 per work hour. Required parts cost 

about $0 per product. Based on these 

figures, the estimated cost of the 

currently required actions is up to $85 

per product. 

We estimate that it would take up to 

165 work-hours per product to comply 

with the new basic requirements of this 

proposed AD. The average labor rate is 

$85 per work-hour. Required parts 

would cost about $10,982 per product. 

Where the service information lists 

required parts costs that are covered 

under warranty, we have assumed that 

there will be no charge for these costs. 

As we do not control warranty coverage 

for affected parties, some parties may 

incur costs higher than estimated here. 

Based on these figures, we estimate the 

cost of the proposed modification on 

U.S. operators to be up to $1,050,294, or 

up to $25,007 per product. 

Authority for This Rulemaking 

Title 49 of the United States Code 

specifies the FAA’s authority to issue 

rules on aviation safety. Subtitle I, 

section 106, describes the authority of 

the FAA Administrator. ‘‘Subtitle VII: 

Aviation Programs,’’ describes in more 

detail the scope of the Agency’s 

authority. 

We are issuing this rulemaking under 

the authority described in ‘‘Subtitle VII, 

Part A, Subpart III, Section 44701: 

General requirements.’’ Under that 

section, Congress charges the FAA with 

promoting safe flight of civil aircraft in 

air commerce by prescribing regulations 

for practices, methods, and procedures 

the Administrator finds necessary for 

safety in air commerce. This regulation 

is within the scope of that authority 

because it addresses an unsafe condition 

that is likely to exist or develop on 

products identified in this rulemaking 

action. 

Regulatory Findings 

We determined that this proposed AD 

would not have federalism implications 

under Executive Order 13132. This 

proposed AD 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. 

For the reasons discussed above, I 

certify 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. 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. 

We prepared a regulatory evaluation 

of the estimated costs to comply with 

this proposed AD and placed it in the 

AD docket. 

List of Subjects in 14 CFR Part 39 

Air transportation, Aircraft, Aviation 

safety, Incorporation by reference, 

Safety. 

The Proposed Amendment 

Accordingly, under the authority 

delegated to me by the Administrator, 

the FAA proposes to amend 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. 

§ 39.13 [Amended] 

2. The FAA amends § 39.13 by 

removing Amendment 39–15644 (73 FR 

47818, August 15, 2008) and adding the 

following new AD: 

Bombardier, Inc.: Docket No. FAA–2010– 

0382; Directorate Identifier 2009–NM– 

211–AD. 

Comments Due Date 

(a) We must receive comments by June 7, 

2010. 

Affected ADs 

(b) This AD supersedes AD 2008–17–06, 

Amendment 39–15644. 

Applicability 

(c) This AD applies to Bombardier, Inc. 

Model DHC–8–400, –401, and –402 

airplanes, certificated in any category; serial 

numbers 4001, 4003, 4004, 4006, and 4008 

through 4184 inclusive. 

Subject 

(d) Air Transport Association (ATA) of 

America Code 29: Hydraulic power. 

Reason 

(e) The mandatory continuing 

airworthiness information (MCAI) states: 

‘‘Several cases have been reported where a 

loss of fluid in the No.2 hydraulic system has 

caused the power transfer unit (PTU) to 


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Federal Register / Vol. 75, No. 76 / Wednesday, April 21, 2010 / Proposed Rules 20789 

overspeed, resulting in pressure fluctuations 

and increased fluid flow within the No. 1 

hydraulic system. In one case, the hydraulic 

system control logic did not shut down the 

PTU and the overspeed condition persisted, 

resulting in the illumination of the No.1 HYD 

FLUID HOT caution light. 

‘‘As an interim action to avoid possible loss 

of both the No. 1 and No. 2 hydraulic 

systems, the Airplane Flight Manual (AFM) 

has been revised to include pulling the HYD 

PWR XFER circuit breaker in the event of the 

loss of all hydraulic fluid in the No. 2 

hydraulic system. 

‘‘Insertion of the resultant Temporary 

Amendment (TA) No. 13 into the AFM was 

mandated in the original issue of this 

[Canadian] directive. This instruction * * * 

remains in effect until * * * this [revised] 

directive is accomplished. 

‘‘Revision 1 of this directive * * * 

mandates modification of the PTU control 

logic, including the provision of automatic 

PTU shutdown in the event of loss of fluid 

in the No. 2 hydraulic system. In addition, 

the applicability of the [Canadian] directive 

has been revised to remove aircraft Serial 

Number (SN) 4185 and subsequent, since an 

equivalent modification has been installed in 

production on these aircraft.’’ 

The unsafe condition is possible loss of 

both the No. 1 and No. 2 hydraulic systems, 

resulting in the potential loss of several 

functions essential for safe flight and landing 

of the airplane. 

Compliance 

(f) You are responsible for having the 

actions required by this AD performed within 

the compliance times specified, unless the 

actions have already been done. 

Restatement of Requirements of AD 2007– 

12–03: Airplane Flight Manual (AFM) 

Revision 

(g) Within 14 days after July 10, 2007 (the 

effective date of AD 2007–12–03, 

Amendment 39–15081, which was 

superseded by AD 2008–17–06), revise the 

Limitations section of the applicable AFM to 

include the information in the applicable 

Bombardier temporary amendment specified 

in Table 1 of this AD, as specified in the 

temporary amendment. These temporary 

amendments introduce procedures for 

pulling the ‘‘HYD PWR XFER’’ circuit breaker 

in the event of the loss of all hydraulic fluid 

in the No. 1 or No. 2 hydraulic system. 

Operate the airplane according to the 

limitations and procedures in the applicable 

temporary amendment. 

TABLE 1—AFM TEMPORARY AMENDMENTS

For Model— 

Use 

Bombardier 

Temporary 

Amendment— 

Issue— Dated— 

To Bombardier 

Dash 8 Q400 

Airplane Flight 

Manual— 

DHC–8–400 airplanes ................................................. 13 1 July 14, 2005 .................................. PSM 1–84–1A. 

DHC–8–401 airplanes ................................................. 13 1 July 14, 2005 .................................. PSM 1–84–1A. 

DHC–8–402 airplanes ................................................. 13 1 July 14, 2005 .................................. PSM 1–84–1A. 

Note 1: This may be done by inserting a 

copy of the applicable temporary amendment 

into the applicable AFM. When the 

applicable temporary amendment has been 

included in general revisions of the AFM, the 

general revisions may be inserted into the 

AFM, provided the relevant information in 

the general revisions is identical to that in 

the temporary amendment. 

Restatement of Requirements of AD 2008– 

17–06: AFM Revision 

(h) Within 14 days after September 2, 2008 

(the effective date of AD 2008–17–06), revise 

the applicable AFM Normal and Abnormal 

Procedures section to include the 

information in the applicable Bombardier 

temporary amendment specified in Table 2 of 

this AD, as specified in the temporary 

amendment. These temporary amendments 

introduce additional procedures for ensuring 

that the ‘‘PTU CNTRL’’ switch is Normal, the 

‘‘PTU CNTRL ON’’ advisory light is out, and 

the ‘‘HYD PWR XFER’’ circuit breaker is 

pulled in the event of the illumination of the 

‘‘#2 HYD ISO VALVE’’ caution light. After 

accomplishing the AFM revision, the AFM 

limitation required by paragraph (g) in this 

AD may be removed from the AFM. 

TABLE 2—AFM TEMPORARY AMENDMENTS

For Model— 

Use 

Bombardier 

Temporary 

Amendment— 

Issue— Dated— 

To Bombardier 

Dash 8 Q400 

Airplane Flight 

Manual— 

DHC–8–400 airplanes ................................................. 13 3 June 9, 2008 .................................. PSM 1–84–1A. 

DHC–8–401 airplanes ................................................. 13 3 June 9, 2008 .................................. PSM 1–84–1A. 

DHC–8–402 airplanes ................................................. 13 3 June 9, 2008 .................................. PSM 1–84–1A. 

New Requirements of This AD: Actions 

(i) Within 6,000 flight hours after the 

effective date of this AD, modify the PTU 

control logic, in accordance with the 

Accomplishment Instructions of Bombardier 

Service Bulletin 84–29–22, Revision A, dated 

February 24, 2009. Doing this modification 

terminates the requirements of paragraphs (g) 

and (h) of this AD, and after the modification 

has been done, the AFM limitation required 

by paragraphs (g) and (h) of this AD may be 

removed from the AFM. 

(j) Modifying the PTU control logic is also 

acceptable for compliance with the 

requirements of paragraph (i) of this AD if 

done before the effective date of this AD, in 

accordance with Bombardier Service Bulletin 

84–29–22, dated December 5, 2008. 

FAA AD Differences 

Note 2: This AD differs from the MCAI 

and/or service information as follows: No 

differences. 

Other FAA AD Provisions 

(k) The following provisions also apply to 

this AD: 

(1) Alternative Methods of Compliance 

(AMOCs): The Manager, New York Aircraft 

Certification Office (ACO), ANE–170, FAA, 

has the authority to approve AMOCs for this 

AD, if requested using the procedures found 

in 14 CFR 39.19. Send information to ATTN: 

Program Manager, Continuing Operational 

Safety, FAA, New York ACO, 1600 Stewart 

Avenue, Suite 410, Westbury, New York 

11590; telephone 516–228–7300; fax 516– 

794–5531. Before using any approved AMOC 

on any airplane to which the AMOC applies, 

notify your principal maintenance inspector 

(PMI) or principal avionics inspector (PAI), 

as appropriate, or lacking a principal 

inspector, your local Flight Standards District 

Office. The AMOC approval letter must 

specifically reference this AD. 

(2) Airworthy Product: For any 

requirement in this AD to obtain corrective 

actions from a manufacturer or other source, 

use these actions if they are FAA-approved. 

Corrective actions are considered FAAapproved if they are approved by the State 

of Design Authority (or their delegated 

agent). You are required to assure the product 

is airworthy before it is returned to service. 


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20790 Federal Register / Vol. 75, No. 76 / Wednesday, April 21, 2010 / Proposed Rules 

(3) Reporting Requirements: For any 

reporting requirement in this AD, under the 

provisions of the Paperwork Reduction Act 

(44 U.S.C. 3501 et seq.), the Office of 

Management and Budget (OMB) has 

approved the information collection 

requirements and has assigned OMB Control 

Number 2120–0056. 

Related Information 

(l) Refer to MCAI Canadian Airworthiness 

Directive CF–2006–08R1, dated August 31, 

2009; and Bombardier Service Bulletin 84– 

29–22, Revision A, dated February 24, 2009; 

for related information. 

Issued in Renton, Washington, on April 9, 

2010. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2010–9110 Filed 4–20–10; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2010–0384; Directorate 

Identifier 2010–NM–003–AD] 

RIN 2120–AA64 

Airworthiness Directives; McDonnell 

Douglas Corporation Model DC–10–10, 

DC–10–10F, DC–10–15, DC–10–30, DC– 

10–30F (KC–10A and KDC–10), DC–10– 

40, DC–10–40F, MD–10–10F, MD–10– 

30F, MD–11, and MD–11F Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to adopt a new 

airworthiness directive (AD) for certain 

Model DC–10–10, DC–10–10F, DC–10– 

15, DC–10–30, DC–10–30F (KC–10A 

and KDC–10), DC–10–40, DC–10–40F, 

MD–10–10F, MD–10–30F, MD–11, and 

MD–11F airplanes. This proposed AD 

would require installing an in-line fuse 

in certain float level switches and 

sleeving the wires between the fuel tank 

and the in-line fuse. For certain 

airplanes this proposed AD would also 

require installing an in-line fuse in 

certain fuel pump pressure switches. 

This proposed AD results from fuel 

system reviews conducted by the 

manufacturer. We are proposing this AD 

to prevent fuel tank explosions and 

consequent loss of the airplane. 

DATES: We must receive comments on 

this proposed AD by June 7, 2010. 

ADDRESSES: You may send comments by 

any of the following methods: 

• Federal eRulemaking Portal: Go to 

http://www.regulations.gov. Follow the 

instructions for submitting comments. 

• Fax: 202–493–2251. 

• Mail: U.S. Department of 

Transportation, Docket Operations, M– 

30, West Building Ground Floor, Room 

W12–140, 1200 New Jersey Avenue, SE., 

Washington, DC 20590. 

• Hand Delivery: U.S. Department of 

Transportation, Docket Operations, M– 

30, West Building Ground Floor, Room 

W12–140, 1200 New Jersey Avenue, SE., 

Washington, DC 20590, between 9 a.m. 

and 5 p.m., Monday through Friday, 

except Federal holidays. 

For service information identified in 

this proposed AD, contact Boeing 

Commercial Airplanes, Attention: Data 

& Services Management, 3855 

Lakewood Boulevard, MC D800–0019, 

Long Beach, California 90846–0001; 

telephone 206–544–5000, extension 2; 

fax 206–766–5683; e-mail 

dse.boecom@boeing.com; Internet 

https://www.myboeingfleet.com. You 

may review copies of the referenced 

service information at the FAA, 

Transport Airplane Directorate, 1601 

Lind Avenue, SW., Renton, Washington. 

For information on the availability of 

this material at the FAA, call 425–227– 

1221. 

Examining the AD Docket 

You may examine the AD docket on 

the Internet at http:// 

www.regulations.gov; or in person at the 

Docket Management Facility between 9 

a.m. and 5 p.m., Monday through 

Friday, except Federal holidays. The AD 

docket contains this proposed AD, the 

regulatory evaluation, any comments 

received, and other information. The 

street address for the Docket Office 

(telephone 800–647–5527) is in the 

ADDRESSES section. Comments will be 

available in the AD docket shortly after 

receipt. 

FOR FURTHER INFORMATION CONTACT: 

Philip Kush, Aerospace Engineer, 

Propulsion Branch, ANM–140L, FAA, 

Los Angeles Aircraft Certification 

Office, 3960 Paramount Boulevard, 

Lakewood, California 90712–4137; 

telephone (562) 627–5263; fax (562) 

627–5210. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

We invite you to send any written 

relevant data, views, or arguments about 

this proposed AD. Send your comments 

to an address listed under the 

ADDRESSES section. Include ‘‘Docket No. 

FAA–2010–0384; Directorate Identifier 

2010–NM–003–AD’’ at the beginning of 

your comments. We specifically invite 

comments on the overall regulatory, 

economic, environmental, and energy 

aspects of this proposed AD. We will 

consider all comments received by the 

closing date and may amend this 

proposed AD because of those 

comments. 

We will post all comments we 

receive, without change, to http:// 

www.regulations.gov, including any 

personal information you provide. We 

will also post a report summarizing each 

substantive verbal contact we receive 

about this proposed AD. 

Discussion 

The FAA has examined the 

underlying safety issues involved in fuel 

tank explosions on several large 

transport airplanes, including the 

adequacy of existing regulations, the 

service history of airplanes subject to 

those regulations, and existing 

maintenance practices for fuel tank 

systems. As a result of those findings, 

we issued a regulation titled ‘‘Transport 

Airplane Fuel Tank System Design 

Review, Flammability Reduction and 

Maintenance and Inspection 

Requirements’’ (66 FR 23086, May 7, 

2001). In addition to new airworthiness 

standards for transport airplanes and 

new maintenance requirements, this 

rule included Special Federal Aviation 

Regulation No. 88 (‘‘SFAR 88,’’ 

Amendment 21–78, and subsequent 

Amendments 21–82 and 21–83). 

Among other actions, SFAR 88 

requires certain type design (i.e., type 

certificate (TC) and supplemental type 

certificate (STC)) holders to substantiate 

that their fuel tank systems can prevent 

ignition sources in the fuel tanks. This 

requirement applies to type design 

holders for large turbine-powered 

transport airplanes and for subsequent 

modifications to those airplanes. It 

requires them to perform design reviews 

and to develop design changes and 

maintenance procedures if their designs 

do not meet the new fuel tank safety 

standards. As explained in the preamble 

to the rule, we intended to adopt 

airworthiness directives to mandate any 

changes found necessary to address 

unsafe conditions identified as a result 

of these reviews. 

In evaluating these design reviews, we 

have established four criteria intended 

to define the unsafe conditions 

associated with fuel tank systems that 

require corrective actions. The 

percentage of operating time during 

which fuel tanks are exposed to 

flammable conditions is one of these 

criteria. The other three criteria address 

the failure types under evaluation: 

Single failures, single failures in 

combination with latent condition(s), 


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