<AA Ronald J. Hinderberger 

Lead Adminislralor 

Regulatory Administration 

Commercial Airplanes 

The Boeing Company 

P.O Box 3707 MC 03-56 

Seattle, WA 98124-2207 

SEP % 1 2011 

KA-n-04847 

U.S. Department of Transportation 

Docket Operations 

West Building Ground Floor, Room W12-140 

1200 New Jersey Avenue, S.E. 

Washington, DC 20590 

CO 

Dear Sir or Madam, 

Subject: Petition for Exemption to Title 14 Code of 

Federal Regulations (CFR) Part 25.863 

In accordance with the provisions of Title 14 Code of Federal Regulation 

§11.61(b), The Boeing Company, herein petitions for an exemption from 14 CFR 

§25.863, tiie exemption petition only address 14 CFR Part 25.863, in accordance 

with the agreement in the Reference b) FAA Letter. 

The exemption, if granted, applies to the following airplanes when owned and/or 

operated by Boeing: 

Model 

737 

Type 

-600/-700/-700C/-800/-900/-900ER 

Petition for Exemption 

In accordance with the requirements of 14 CFR §11.81(a)-(g), we provide the 

following detailed information in support of our petition: 

Contact Information: 

Ron Hinderberger 

VP, Regulatory Administration 

Boeing Commercial Airplanes 

P.O. Box 3707, M/C 03-37 

Seattle, WA 98124-2207 

e-mail: ron.j.hinderberfg.boeing.com 

The specific sections of 14 CFR from which we seek an exemption: 

Boeing is seeking relief from the following regulation for the main engine 

exhaust plug installation on the 737-600/-700/-700C/-800/-900/-900ER models: 

14 CFR §25.863 Flammable fluid protection. 

(a) In each area where flammable fluids or vapors might escape by leakage 

of a fluid system, there must be means to minimize the probability of 
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ignition of the fluids and vapors, and the resultant hazards if ignition 

does occur, 

(b) Compliance with paragraph (a) of this section must be shown by analysis 

or tests, and the following factors must be considered: 

(J) Possible sources and paths of fluid leakage, and means of detecting 

leakage. 

(2) Possible ignition sources, including electrical faults, overheating of 

equipment, and malfunctioning of protective devices. 

The extent of relief we are seeking, and the reason we are seeking the relief: 

Extent of Relief 

The CFM56-7B engine installation on the 737-600/-700/-700C/-800/-900/-

900ER models uses a core exhaust nozzle and plug to control the flow of the 

exhaust gases from the engine. The CFM56-7B engine incorporates a center vent 

tube that exhausts air into the plug cavity. The plug has a 4.8 inch opening in the 

aft end to allow the engine vent air to e)diaust overboard. The engine also 

incorporates a drain for the main bearing aft oil sump that discharges into the 

plug cavity. There are not designed drainage provisions for the plug cavity of the 

314A2620-1 plug installation. 

Boeing is seeking relief from §25.863 (a), (b)(1), (b)(3) as it applies to the 

internal cavity of the 314A2620-1 plug installation on certain 737-600/-700/-

700C/-800/-900/-900ER airplanes. Engine oil and/or fiiel can be directed to the 

plug cavity by the aft sump drain and/or the center vent tube. There are no 

drainage provisions in the 314A2620-1 plug installation. The plug surface 

temperatures can exceed the auto-ignition temperature of engine oil and fuel. 

Consequently direct compliance for the 314A2620-1 plug installation cannot now 

be shown to §25.863 (a), (b)(1), (b)(3). The 314A2620-1 plug installation was 

previously found compliant with §25.863(a), (b)(1), (b)(3) in error. 

At Line No. 3762, Boeing introduced a new exhaust installation including a new 

plug that was compliant with §25.863. However, the new type design could not 

be approved with the 314A2620-1 plug installation as an interchangeable spare 

for the new exhaust. Consequently, installation of the 314A2620-1 plug is not 

allowed on 737-600/-700/-700C/-800/-900/-900ER models from Line No. 3762 

and on. Boeing is seeking relief from the regulation via exemption to allow the 

installation. 

Public Interest 

Exemption from §25.863(a),(b)(l), (b)(3) forthe 314A2620-1 plug installation 

on Line No. 3762 and on would be in the public interest. The inability to use the 

314A2620-1 plug on a sub-group of airplanes within an airline operator's fleet 

creates a significant interchangeability issue. There are currently over 7,000 of 

the 314A2620-1 plugs in service operation. Typically the exhaust is installed as 

part of the spare engine kit to minimize the engine change time on the flightline. 

Operators have informed Boeing that the interchangeability restriction will 
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increase operational costs arising from the additional inventory control processes 

that will be needed, and potential delays if the correct exhaust part number is not 

immediately available. These costs will eventually be passed on to the public. 

Removing the restriction will allow greater flexibility and increased efficiency 

for the operator to better serve the public. 

Safety 

Exemption from §25.863(a),(b)(l), (b)(3) forthe 314A2620-1 plug installation 

on Line No. 3762 and on would not adversely affect public safety based on the 

features summarized below. The F AA-SACO agreed with a similar assessment 

in 2009. 

The airplane is protected from the effects of a potential fire within the exhaust 

plug by the following design and construction features: 

The plug is considered fireproof There is a 4.8 inch diameter opening in the aft 

end of the plug to provide for ventilation flow. This opening is approximately 60 

inches aft from the location where fluid would collect at the forward end of the 

plug. 

The plug is shielded from the airplane surfaces along most of its length by the 

exhaust nozzle, which is also considered fireproof. 

There is a heat shield direcfly above and aft of the exhaust that protects the aft 

strut fairing. The heat shield is considered fireproof 

The lower surfaces of the wing within one nacelle diameter of the fire zone, 

including the control surfaces, are fire resistant. 

The vertical distance from the opening in the aft end of the pug to the aft fairing 

is 11 inches; to the undersurface of the wing is 36 inches. The horizontal 

distance to the wing rear spar is 48 inches. 

Failures of the engine that could result in evacuation of the oil system into the 

plug cavity will be indicated to the Flight Crew by a low oil pressure indication. 

The Boeing Flight Crew Operations Manual (FCOM) instructs the crew to 

perform an engine shutdown for low oil pressure indication. 

A potential fire in the plug cavity will be identified and addressed by the Flight 

and Ground crews in the same manner as a traditional fuel-fed tailpipe fire. 

The installation is currently operating on over 3,500 airplanes and has 

accumulated over 66 million hours and 35 million cycles as of April 2011. 

Operation and installation of the 314A2620-1 plug installation on post-Line No. 

3762 airplanes is identical to the installations that have safely accumulated these 

hours/cycles. 
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Summary of Petition 

Petitioner: Boeing Commercial Airplanes 

Section of 14 CFR affected: 14 CFR 25.863(a), (b)(1), (b)(3) 

Description of Relief Sought: To permit installation of the 314A2620-1 exhaust 

plug on 737-600/-700/-700C/-800/-900/-900ER model airplanes, Line No. 3762 

and on. 

Request to Waive Publication and Comment 

In some cases, the FAA may waive the requirement for publication and 

comment. One potential reason is that the relief requested is identical to 

previously granted exemptions. Given that the installation of the 314A2620-1 

exhaust plug is currently operating on over 3,500 airplanes and has accumulated 

over 66 million hours and 35 million cycles as of April 2011, Boeing requests 

that the FAA waive the requirement for publication and comment. 

Need to Exercise the Exemption Outside of the United States 

737-600/-700/-700C/800/-900/-900ER model airplanes from Line No. 3762 and 

on are anticipated to be operated in many foreign countries. To provide for 

maximum efficiency and flexitility for foreign operators, Boeing requests that the 

FAA allow the use of the petitioned exemption outside of the United States. 

Should you have questions or require additional information, please do not 

hesitate to contact the undersigned or Debra Dean at debra.a.deanfg,boeing.com 

or (425) 717-1165. 

Very truly yours. 

Timothy P. Dowling 

RA Program Manager Fleet Support 

(206) 766-3885, MC 03-56 

FAX: (425)294-9340