Enclosure to RA-13-00338

Petition for Exemption from § 25.901(c) Amendment 25-126 and 

25.981(a)(3) Amendment 25-125, Title 14, Code of Federal Regulations

Page 1

Name and Address of the Petitioner

Doug Lane, Director, Regulatory Administration Deputy Lead Administrator

The Boeing Company

PO Box 3707

Seattle, Washington, 98124

Section(s) of the Regulations from which Relief is sought:

14 CFR 25.901(c) at Amendment 25-126 requires:

(c) For each powerplant and auxiliary power unit installation, it must be established that no 

single failure or malfunction or probable combination of failures will jeopardize the safe 

operation of the airplane except that the failure of structural elements need not be considered 

if the probability of such failure is extremely remote.

14 CFR 25.981(a)(3) at Amendment 25-125 requires:

(a) No ignition source may be present at each point in the fuel tank or fuel tank system where 

catastrophic failure could occur due to ignition of fuel or vapors. This must be shown by:

(3) Demonstrating that an ignition source could not result from each single failure, 

from each single failure in combination with each latent failure condition not shown 

to be extremely remote, and from all combinations of failures not shown to be 

extremely improbable. The effects of manufacturing variability, aging, wear, 

corrosion, and likely damage must be considered.

The Extent of Relief Sought and Reason(s):

Regulation Compliance requires: Relief is Necessary because:

14 CFR 25.901(c) 

Amendment 25-126

No single failure or 

malfunction or probable 

combination of failures will 

jeopardize safe operation 

Direct compliance would require 

unnecessary redesign of the Airplane 

Wiring System to ensure Fuel Quantity 

Indication System (FQIS) tank circuit 

wire separation for retrofit of 777-200/-

300 model series aircraft using the 

changed Fuel Quantity Processing Unit 

(FQPU) for replacement or repair. 

14 CFR 25.981(a)(3) 

Amendment 25-125

An ignition source could not 

result from each single failure, 

from each single failure in 

Same as above
Enclosure to RA-13-00338

Petition for Exemption from § 25.901(c) Amendment 25-126 and 

25.981(a)(3) Amendment 25-125, Title 14, Code of Federal Regulations

Page 2

combination with each latent 

failure condition not shown to 

be extremely remote, and from 

all combinations of failures not 

shown to be extremely 

improbable. The effects of 

manufacturing variability, 

aging, wear, corrosion, and 

likely damage must be 

considered.

Description of Issue:

The Fuel Quantity Processor Unit (FQPU) manufacturer informed Boeing that their supply of 

particular components within the FQPU would be exhausted in late 2013 and that they had 

unsuccessfully attempted to find alternate sources for the procurement of these components, leading 

to component changes within the FQPU. The FQPU component changes included the following 

hardware changes to the FQPU Circuit Card Assemblies (CCAs), which contain the following 

airborne electronic hardware (AEH) devices that are complex per RTCA/DO-254: 

- ARINC 429 receiver Application Specific Integrated Circuit (ASIC) device

- ARINC 629 ASIC device

- Three unique FPGAs (Field Programmable Gate Array)

- Commercial Off The Shelf (COTS) microprocessors 

It is the position of The Boeing Company that system level full compliance to 25.901(c) Amendment 

25-126 and 25.981(a)(3) Amendment 25-125 for Fuel Quantity Indicating Systems (FQIS) for 

retrofit of previously delivered 777-200 and 777-300 model series airplanes prior to line number 562

should not be required for this proposed change. The objective of this exemption is to allow airline 

operators to install the changed FQPU on earlier airplane models that are no longer in production. 

The basis for this exemption request is that without exemption relief, significant airplane changes 

would be required for these earlier airplanes. These changes involve new system architecture and 

extensive airplane wiring installation changes to ensure adequate wire separation throughout the fuel 

quantity indication system.

This level of retrofit change for the existing fleet would be a significant burden as the changes are 

costly and time consuming and would not provide a proportional benefit or increased level of safety 

that is comparable to the level of effort required to incorporate them. 
Enclosure to RA-13-00338

Petition for Exemption from § 25.901(c) Amendment 25-126 and 

25.981(a)(3) Amendment 25-125, Title 14, Code of Federal Regulations

Page 3

Statement of Public Interest:

Granting this exemption is in the public interest because denial of this petition for exemption 

would result in the airlines having to perform extraordinary work which would result in 

disruption of operations and would pose significant burden on the airlines to make the 

airplane changes outlined for installation of a 25.901(c) and 25.981(a)(3) compliant FQIS

whenever an in-service FQPU fails within their fleet.

Statement of No Adverse Effect on Safety:

The current FQIS system on the 777-200 and 777-300 model series has been thoroughly evaluated 

for safety aspects in such forums as Boeing’s safety assessment that was required per 14 CFR 

Special Federal Aviation Regulation No. 88 (SFAR88) for the FQIS and no safety issues were 

identified by Boeing. Since then there have been safety improvements to address issues identified 

by the FAA. The replacement FQPU will be certified and thoroughly tested to the current

regulations during qualification testing. Allowing the changed FQPU to be retrofitted and installed 

as a part of the existing FQIS will not adversely affect the existing level of safety.

Request for Reduction of Publication Comment Period:

In view of the anticipated obsolescence of parts by late 2013, Boeing requests that the Public 

comment period be kept to a minimum.

Privileges of the Exemption Outside the United States:

Per 14 CFR 11.81(h), Boeing requests that the privileges of this exemption be extended outside the 

United States. This extension of privileges is necessary for operations based within foreign countries 

having bilateral agreements with the United States accepting FAA 14 CFR Part 25 as their 

airworthiness standards for transport category aircraft. 

Conclusion:

Boeing is petitioning for an exemption from the provisions of 14 CFR 25.901(c)[Amdt. 25-126] and 

25.981(a)(3)[Amdt. 25-125] at the system level as they apply to the FQIS installed on the 777-200

and 777-300 airplanes prior to line number 562 for the FQPU parts obsolescence change described. 

The following component changes are necessary due to part obsolescence: 

- ARINC 429 receiver ASIC device (Application Specific Integrated Circuit)

- ARINC 629 ASIC device

- Three unique FPGAs (Field Programmable Gate Array)

The changed FQPU with these components will not impact the FQIS safety and the part itself will be 

shown to meet the requirements of 14 CFR 25.901(c) and 25.981(a)(3). 
Enclosure to RA-13-00338

Petition for Exemption from § 25.901(c) Amendment 25-126 and 

25.981(a)(3) Amendment 25-125, Title 14, Code of Federal Regulations

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Granting this exemption will allow use of the type certified production FQPU line replaceable unit 

(LRU) on previously delivered 777-200 and 777-300 model series without extensive rework to an inservice aircraft.

Summary to be Published in the Federal Register:

PETITIONER: Boeing Commercial Airplanes

SECTION OF 14 CFR AFFECTED: 14 CFR 25.901(c) Amdt. 25-126, 14 CFR 25.981(a)(3) 

Amdt. 25-125

DESCRIPTION OF RELIEF SOUGHT: 

Boeing is petitioning for an exemption from the provisions of 14 CFR 25.901(c)[Amdt. 25-126] 

and 25.981(a)(3)[Amdt. 25-125] at the system level as they apply to the FQIS installed on the 

777-200 and 777-300 airplanes prior to line number 562 for an FQPU parts obsolescence 

retrofit modification, without extensive rework to the in-service aircraft.