U.S. Department of Transportation Feder a l Aviatio n Administration

October 17, 2014

Douglas M. Lane Director The Boeing Company PO Box 3707 Seattle, Washington. 98124

Dear Mr. Lane: Transport Airplane Directorate 1601 Lind Ave , SW. Renton , Washington 98057
-3356

Exemption No. 11086 Regulatory Docket No. FAA-20 13-0767

This letter is to inform yo u that we have granted your request for exemption. It transmits our decision and explains its basi s. The Basis for Our Decision By letter RA-13-03942 elated August 26, 2013, Mr. Thomas Howorth, on behalf ofThe Boeing Company, petitioned the Federal Aviation Administration (FAA) for an exemption from the requirements

**of~** 25.961(a)(5) ofTitle 14, Code of Federal Regulations (14 CFR) as it relates to fuel-system hot-weather operation. The request seeks relief from these requirements for Boeing Model 767-2C airplanes. The FAA has issued grants ofexemption . with operational limits , in circumstances similar in all material respects to tho se presented in your petition, including for Boeing Model 747-400 and 757 series airplanes using JP-4 and Jet B fuel. Having reviewed your reasons for requesting an exemption, I find that-

• they don't diffcr materially hom those presented by the petitioner in the enclosed grant of exemption:
• the reasons stated by the FAA for granting the enclosed exemption also apply to the situation you present: and
• a grant ofexemption is in the public interest.

### FederalRegister Publication The FAA has determined that good cause exists for not publishing a summary ofthe petition in the Federal Register because the requested exemption would not set a precedent, the FAA has not received public comments on other exemption requests for relieffrom § 25.961 (a)(5), fuelsystem hot-weather operation, and any delay in acting on this petition would be detrimental to The Boeing Company. Our Decision Under the authority contained in 49 U.S.C

. 40113 and 44701, which the FAA Administrator has delegated to me, I hereby grant The Boeing Company an exemption from the requirements of 14 CFR 25

.961(a)(5) as it relates to fuel-system hot-weather operation on Boeing Model 767-2C airplanes. All "Operational Limits" described in the " Grant ofExemption" section ofexemption 7790 also apply to this exemption. Sincerely,

Michael Kaszycki Acting Manager, Transport Airplane Directorate Aircraft Certification Service

Enclosure

### Exemption No. 7790

UNITED STATES OF AMERICA DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION RENTON, WASHINGTON 98055-4056

In the matter ofthe petition of 

### The Boeing Company for an exemption from§ 25.961(a)(5) of Title 14, Code ofFederal Regulations 

### Regulatory Docket No. FAA-2001-11155

GRANT OF EXEMPTION By letter dated November 8, 2001 (B-H320-2001-00899), Mr. Edgars A. 

### Kupcis, Manager, Certification, Certification & 

### ETOPS Programs, B-H320, The Boeing Company, P.O. Box 3707, Seattle, WA 98124-2207, petitioned for an exemption from the requirements of§ 25.961(a)(5) at Amendment 25-85 ofTitle 14, Code ofFederal Regulations (14 CFR) to permit The Boeing Company, for the Model 757-300 series airplanes powered by Pratt & 

### Whitney PW2000 series engines, to be relieved ofthe requirement that the airplane and engines perform satisfactorily with the critical fuel at a temperature ofat least 11 0°F. 

### Sections of the Federal Aviation Regulations (FAR) Affected Section 25.961(a)(5), at Amendment 25-85, requires that the airplane and engines perform satisfactorily with the critical fuel at a temperature ofat least 110°F. 

### Petitioner's Supportive Information The Boeing Company's supportive information is summarized as follows: Boeing is introducing a Model 757-300 series airplane powered by Pratt & 

### Whitney engines. The Model 757-200 series airplane with Pratt & 

### Whitney engines was introduced in 1984, and has accumulated over 11.6 million flight hours ofrevenue service. The Model 757-300 series airplane with Rolls Royce engines was introduced in 1999 and has accumulated over 80,000 flight hours ofrevenue service. The Pratt & 

### Whitney-powered

### Model 757-300 series airplane will offer three engines: PW2037, PW2040, and PW2043. The Model 757-200 series airplane offers PW2037 and PW2040 engines. Boeing is requesting relieffrom the requirements of 14 CFR 25.961(a)(5), at Amendment 25-85, for the Pratt & 

### Whitney-powered Model 757-300 series airplane. The regulation requires that the airplane and engines perform satisfactorily with the critical fuel at a temperature ofat least 11 0°F. Boeing requests that the FAA approve a set oflimitations for JP-4 (a military designation for a Jet B type commercial grade fuel with additives) and Jet B fuels on the Pratt & 

### Whitney-powered Model 757-300 series airplane in lieu of compliance with the specified temperature of 11 0°F. The limitations consist ofrestricting the fuel temperature to 85°F, restricting the initial cruise altitude vs. fuel temperature, and restricting JP-4 and Jet B fuels to the main tanks only. These same limitations were approved for the Rolls Royce-powered Model 757-300 series airplane. Boeing submits this petition for the following reasons: ( 1) It 

### is in the public interest. Airline operators strongly desire the operational flexibility ofJP-4 and Jet B fuels, and a maximum temperature of 85°F meets their needs. (2) The Model 757-200 series airplane with Pratt & 

### Whitney PW2037 engines demonstrated satisfactory performance with JP-4 at 1 04°F. All Pratt & 

### Whitneypowered Model 757-200 series airplanes are approved for JP-4 and Jet B use up to ll0°F. (3) There will be no significant differences in the fuel system between the Pratt & 

### Whitney-powered Model 757-200 and the Model 757-300 series airplanes. (4) The proposed limitations on fuel temperature, maximum altitude for initial cruise, and prohibition on the use ofJP-4 and Jet B fuels in the center tank provide a level of safety equal to that intended by§ 25.961(a)(5). (5) The FAA granted a similar exemption for the Rolls Royce-powered Model 757-300 series airplane (FAA Exemption No. 6867, issued Feb. 12, 1999, Regulatory Docket No. 29202). The Rolls Royce-powered Model 757-200 series airplane has had an 85°F temperature limitation for JP-4 and Jet B fuels since entry into service in 1983.
Public Interest Boeing argues that it is in the public interest that airlines be able to operate with JP-4 and Jet B fuels. These fuels are used in some parts ofthe world and are occasionally the only fuels available at military airfields that may serve as diversion airports. The economic impact ofnot being able to divert to these airfields in the event ofan emergency is significant. When surveyed, several 757 operators reported that the loss ofthis capability would significantly impact their operations. Excerpts from two operators are provided below. The usage of JP-4fuel is very rare, but in afew occasions it was necessary... due to diversions to military airfields. Restricting the use of JP-4fuel would heavily impact the



### 2operation

.. . as several enroute alternates or destination alternates could no longer be chosen for flight planning

. This is especially true for the areas of Alaska, Canada, Caribbean, Iran /

Persia and Turkey. 

### Ifthe aircraft were not certificated to use JP-4 /

Jet B then each sector would need to be re-evaluated with respect to approved diversionary airfields and reservefuel carried, so it is quite possible that there would be many routes which would cost more to operate and others where a decision would be made not to operate because ofthe capability of the aircraft

. Boeing contends that the economic impact offull compliance with§ 25.961(a)(5) would be debilitating. It is unlikely that the existing Pratt & Whitney- and Rolls Royce-powered Model 757's or the upcoming Pratt & Whitney-powered Model 757-300 series airplanes would satisfy the performance requirements as they have been applied to recent new airplane programs with 11 0°F fuel. A major redesign to the airplane fuel feed system, fuel tanks , and potentially the airplane electrical system would be required to satisfy these requirements as most recently interpreted. These changes would involve an expensive recertification effort ofthe Model 757 fuel feed system with essentially no return on investment or enhancement ofsafety. It is probable these changes would introduce new failure modes into the present system that has proven very reliable in service. 

### Level of Safety Provided
With regard to§ 25.961(a)(5) , the ability ofan · airplane to operate with JP-4 and Jet B fuels is a function ofthe vapor pressure ofthe fuel, which increases with temperature. The vapor pressure ofwide cut fuels such as JP-4 and Jet B is considerably higher than that ofnarrow cut fuels such as Jet A. Under normal conditions, the aircraft fuel boost pumps maintain the pressure in the fuel feed system above the vapor pressure ofthe fuel.

Ifall aircraft boost pumps are inoperative, the engine fuel pumps will continue to draw fuel out ofthe tanks to maintain engine operation. This condition is termed suction feed operation. At high fuel temperatures and high altitudes, the pressure in the fuel feed system can decrease to or reach a value near the vapor pressure ofthe fuel , allowing some fuel to vaporize and potentially causing engine flameout. Regulation§ 25.961(a)(5) addresses this condition, among others, and is intended to ensure that airplane operation will not be adversely impacted by fuel temperature. Boeing believes that incorporating a temperature limitation of 85 °F for JP-4 and Jet B fuels provides a level ofsafety equal to that intended by the regulation. This position is based on several considerations: a) Differences between the Model 757-200 and Model 757-300 series airplane fuel systems do not affect suction feed operation. The changes include longer wiring between the fuel quantity indicating system processor and in-tank capacitance probes, a slightly increased allowable fuel volume for all three fuel tanks , and a longer fuel

3feed hose to the auxiliary power unit. These changes were certified on the Rolls Royce-powered Model 757-300 series airplane. There are no further airplane fuel system changes planned for the Pratt & Whitney-powered Model 757-300 series airplane. b) There are no hardware differences between the PW2037/PW2040 engine fuel systems on the Model 757-200 and Model 757-300 series airplanes. c) Hardware differences between the PW2037/2040 and PW2043 engine fuel systems do not adversely affect suction feed operation. There are two changes in the engine fuel system to support the PW2043: the fuel control unit (FCU) and the fuel pump. The PW2043 FCU is the same basic unit as the PW2037/2040 FCU with a larger fuelmetering window. The PW2043 fuel pump is designed to match the performance of the PW2037/2040 pump with increased flow capacity at higher pump rotational speeds. The PW2043 pump was certified for use on the Model 757-200/PW2037 and PW2040 via bench and flight testing in June 2000. Suction feed requirements were substantiated by back-to-back rig testing. d) Thrust differences at maximum continuous thrust (MCT) between the PW2037, PW2040, and PW2043 are offset by the temperature limitation of 85 °F. The Model 757-200 series airplane with PW2037 engines demonstrated satisfactory performance in suction feed operation with JP-4 fuel at a temperature of 104°F

. The slightly lower system pressure resulting from the increased fuel flow at PW2040 and PW2043 thrust is more than offset by the decreased vapor pressure between 1 04°F and 85 °F. The slightly higher fuel pump rotor speed at PW2040 and PW2043 thrust has a negligible effect on the net positive suction pressure required by the pump to prevent cavitation. In addition to the temperature limitation, Boeing proposes to incorporate additional restrictions on altitude vs. temperature and center tank usage to further ensure an equal level of safety

. The following limitations, already approved and incorporated in the Rolls Royce-powered Model 757-300 airplane flight manual, are proposed for the Pratt & Whitney-powered Model 757-300 airplane flight manual : (1) JP-4 or Jet B fuel shall not be used in the center tank

. (2) The maximum allowable fuel temperature for JP-4 or Jet B fuel is 85°F. (3) When operating with JP-4 or Jet B fuels , the maximum allowable altitude for the first two hours ofcruise operation shall be limited to:

Dispatch Fuel Temperature (°F)
65 to 85 45 to 65 25 to 45 15 to 25

4 Altitude Limit (Feet) 32,000 36,000 39,000 41 ,00015 or Lower 42,000 (4) The fuel tanks must be defueled to sump level (i.e. level at which fuel pump low-pressure lights illuminate) following operations with JP-4 or Jet B fuel. If the fuel tanks are not delueled, the JP-4 fuel usage limitations shall continue to apply. It should be noted that there is an inherent margin of safety associated with limiting JP-4 or Jet B fuel usage based on suction fuel feed capability. Under normal conditions, the airplane tuel boost pumps will be functioning. There are two alternating current (AC) powered boost pumps in each of the main fuel tanks, and two AC-powered boost pumps in the center tuel tank. The center tank boost pumps can adequately supply fuel to the engines with the main tank boost pumps inoperative. Under pressure feed conditions, the airplane can operate normally with .IP-4 fuel at a temperature of 110°F up to maximum altitude. Suction feed operation is required only when all AC power is lost on the airplane. The probability ofthis occurrence is extremely low due to redundancies incorporated in the airplane electrical system. Notice and Public Pt·ocedurc Provided On March 28,2002. the FAA published notice ofthe petition for exemption in the Federal Register and requested comments from the public. No comments have been received. FAA's Analysis of the Petition The regulation regarding fuel system performance with hot fuel is intended to ensure that an uninterrupted fuel supply is provided to the engines. Section 25.961 (a)(5) specifically requires that this capability be demonstrated with fuel at a temperature ofat least 110 °F. The Boeing Model 757-200 series airplane with Pratt & Whitney PW2037 engines was shown by testing ofcomponents and tuel system analysis to directly comply with § 25.961 (a)(5). As discussed by the applicant, an 85 °F fuel temperature limitation was imposed for Boeing Model 757-200 series airplanes equipped with Rolls-Royce engines following testing intended to show compliance with § 25.1351 (d). This testing showed that engine power interruption could not be induced at any altitude within the airplane performance envel ope with 

### JP-4 fuel at a temperature of 85° F. A similar, early test on the 757-200 airplane with Pratt & Whitney PW2037 engines demonstrated adequate performance ofthe fuel system with 104° F. JP-4 fuel and JP-4/Jet B use was therefore unrestricted within the normal I I

# oo F limitation. Since the original finding ofcompliance with§ 25.961(a)(5) on the Boeing Model 757-200 series airplane with Pratt & Whitney PW2037 engines, the FAA has determined that a more extensive tlight test ofthe airplane with hot fuel is necessary to show compliance with this section. Anal ysis and component testing alone are no longer accepted by the FAA as an adequate demonstration ofcompliance because ofunexpected

5fuel flow interruption to the engines during certification flight testing on an airplane utilizing these method s. 1-! owever, in this petition for exemption, the applicant has proposed operational limitations on dispatch fuel temperatures and altitude that ensure that satisfactory fuel system performance will be achieved. These limitations are consistent with flight test per1ormance previously demonstrated by the airplane and engines, and with the latest. more stringent, requirements.
The petitioner has requested that the Boeing Model 757-300 derivative airplane equipped with Pratt & Whitney PW2000 series engines be granted an exemption from 

### § 25.961 (a)(5). The inf ormation provided by the petitioner indicates that granting ofthe exemption to allow usc orJP-4 and Jet B fuel would be in the public interest because it will allow use of alternate airports where these fuels are the only fuels available. Public safety would not be adversely affected because the temperature and fuel loading limitations placed on the airplane will limit operation ofthe airplane to fuel temperatures where sati sfactory fuel system performance has been demonstrated. The Grant of Exemption
In consideration ofthe roregoing, I 1ind that a grant ofexemption is in the public interest and will not adversely afrect the level or safety provided by the regulations. Therefore, pursuant to the authority contained in 49 U.S.C. 40113 and 44701, delegated to me by the Administrator, the petition ofthe Boeing Company for an exemption from the fuel system hot weather operation requirements or§ 25.96 1 (a)(5) at Amendment 25 -85, tor the fuel system ofthe Boeing Model 757-300 series airplanes powered by Pratt & Whitney PW2000 series engines, is hereby granted, with the following limitations.
The foll owing limitations are to be included in the airplane flight manual (AFM) for Model 757-300 series ai rpl anes powered with Pratt & Whitney PW2000 series engines:

" Operational Limits: "(I) JP-4 or Jet B fuel shall not be used in the center tank

.

..(2) The maximum all owable fuel temperature for JP-4 or Jet B fuel is 85 °F

.

..(3) When operating w ith JP-4 or Jet B fuels, the maximum allowable altitude for the first two hours ofcruise operation shall be limited to: Dispatch Fuel Temperature (°F)
65 to 85 45 to 65 25 to 45 15 to 25 15 or Lower



### 6 Altitude Limit (Feet) 32,000 36,000 39,000 41 ,000 42,000

### "(4) The fuel tanks must be defueled to sump level (i.e. level at which fuel pump low-pressure lights illuminate) following operations with JP-4 or Jet B fuel. Ifthe fuel tanks are not defueled, the JP-4 fuel usage limitations shall continue to apply." Issued in Renton, Washington, on June 3, 2002.

I

s / Ali Bahrami Ali Bahrami Acting Manager Transport Airplane Directorate Aircraft Certification Service

7